Littérature scientifique sur le sujet « Bacillus (Bacteria) – Control – South Africa »

The Cr(VI) reducing capability of an acclimated indigenous culture cultivated from primary sludge was evaluated in batch and packed-bed bioreactor systems. Performance evaluation was carried out in unmodified cultures, cultures modified by substituting terminal organisms in the consortium by a known Cr(VI)-reducing organism (Escherichia coli ATCC 33456), and pure cultures of Cr(VI)-reducing organisms. A high Cr(VI) reduction rate was observed in modified cultures and in the pure culture of the Cr(VI)-reducing bacteria (Bacillus sp.). Furthermore, the Bacillus sp. pure culture outperformed both the unmodified and modified consortium cultures in reducing Cr(VI). Abiotic Cr(VI) reduction activity was evaluated in heat-killed and azide (N3−) inactivated control cultures. No significant Cr(VI) reduction was observed in the controls. This study is part of the continuing research to identify synergistic culture systems for treating toxic compounds from polluted environments.

Recent discoveries of RNA-based regulatory mechanisms have prompted substantial interest in how they formed and the extent to which varying environmental conditions have influenced their evolution. One class of RNA-based regulatory mechanism that has been found in bacteria is the riboswitch, regulating the biosynthesis of certain vitamins by an RNA genetic control element that senses small molecules and responds with a structural change that affects transcription termination or translation initiation without the participation of proteins. By taking the thiamin pyrophosphate (TPP)-riboswitch in Bacillus subtilis as a model system, we wish to examine whether beneficial mutations may exist at the level of RNA that will cause an improvement in organism fitness. By computationally analyzing the difference in primary and secondary structure of the B. subtilis TPP-riboswitch collected from the xeric "African" south-facing slope (SFS) vs. the mesic, "European", north-facing slope (NFS) in "Evolution Canyon" III at Nahal Shaharut, southern Israel, we wish to experimentally study the environmental effect on transcription termination in these RNA-based regulatory mechanisms that are believed to be of ancient origin in the evolutionary time scale. Computational results, so far, indicate that specific mutations affect the riboswitch conformation by causing a global rearrangement. We would like to check whether such mutations could be adaptive mutations that may have a beneficial fitness effect, taking the TPP-riboswitch as a model system at the micro-scale. Empirical results so far indicate that in the promoter region of the TPP-riboswitch, all mutations increase nucleotide GC content in the xeric SFS, whereas in the mesic NFS they increase AT content. Preliminary examination of termination efficiency of strains found exclusively on one slope or the other, reveal increased termination efficiency in the presence of TPP and at more moderate temperatures, but only a suggestion of greater termination efficiency from strains found on both slopes. We expect that further results will shed light on the mutational differences of TPP-riboswitch sequences found on opposite slopes of "Evolution Canyon" III at Nahal Shaharut, potentially leading to interesting discoveries that relate to the topic of adaptive, nonrandom mutations.

Terrorism that involves the deliberate release or distribution of biological agents is called bioterrorism. These pathogens are bacteria, viruses, fungi, other microorganisms and their related toxins, insects, and they can be natural or human-modified forms, which are roughly the same way as in biological warfare that can sicken or kill people, livestock, or crops. These high-priority means include organisms or toxins that pose the greatest risk to the public and national security: Anthrax (Bacillus anthracis) Botulism (Clostridium botulinum toxin) Plague (Yersinia pestis). They have the ability to have harmful effects on human health in many ways, from relatively mild allergic reactions to serious medical conditions and even death. Bacillus anthracis, the bacterium that produces anthrax, and is one of the pathogens most likely to be used for biological attacks.Bioterrorism cancausemass deaths, epidemics, medical staff illness, environmental pollution, legal issues, and cause anxiety in the medical community and the wider community (1). Unfortunately, bioterrorism agents are difficult to control and affect military personnel and civilian men, women and children. In the past 100 years, the United States and the international community have experienced various acts of bioterrorism against civilians. The model shows that the economic impact of bioterrorism attacks ranges from an estimated US$477.7 million per 100,000 people exposed (brucellosis scenario) to US$26.2 billion per 100,000 people exposed (anthrax scenario). The possibility of bioterrorism is particularly worrying because it causes disease, death and panic, disproportionate to the resources consumed (2). The purpose of bioterrorism is usually to create fear and / or threaten the government or society in order to obtain political, religious or ideological objectives. Compared to weapons like explosives, it can have a unique impact on society. Depending on the situation, wear a mask to reduce inhalation or spread of bacteria. If you have been in contact with biological agents, remove and store your clothing and personal things. Follow official instructions for disposing of contaminated items. Wash with soap and water and put on clean clothes. Bioterrorism agents can be spread through the air or into food or water, and are extremely difficult to detect. The outbreak of biological weapons’ diseases may lead to the extinction of endangered wild animal species, the erosion of genetic diversity of domesticated animals and plants, and the destruction of traditional human livelihoods (3). Symptoms of exposure to biological agents may include sore throat, fever, blurred vision or diplopia, rash or blistering, exhaustion, slurred speech, confusion, muscle weakness, nausea, abdominal pain, vomiting, diarrhoea, and cough. The occurrence of a weapon attack may be impossible, but planning and preparation can greatly reduce the death and suffering caused by it. Only 16 countries plus Taiwan possess or presumably possess biological weapons programs: Canada, China, Cuba, France, Germany, Iran, Iraq, Israel, Japan, Libya, North Korea, Russia, South Africa, Syria, and the United States. Britain and the United States. The way to deal with such threats is through international law and carefully negotiated treaties and verification mechanisms. An important protection measure against biological weapons is currently being negotiated in Geneva. Available protective equipment includes respiratory protection devices, full-face protective masks and surgical masks for respiratory protection, combat suits, protective gloves, and skin-protecting boots. Full protection is required when the agent is not recognized. The inherent characteristics of biological agents that affect their potential for use as weapons include: virulence; toxicity; pathogenicity; incubation period; transmissibility; lethality and stability. Now regarding the COVID19 pandemic, there is a game of blame between the two superpowers, the United States and China. It is not clear whether the spread of COVID19 is intentional or unintentional, whether it is a natural virus threatening the world or an artificial virus. Two conspiracy theories about the origin of COVID19 are widely circulated in China and the West, one accusing the United States and the other accusing the higher-level biological containment laboratory in Wuhan, the epicentre of the pandemic (4). However, this has caused pain, death, mental distress, depression, and billions of dollars in treatment and vaccine costs all over the world. This whole process reminds us of Frankenstein's sci-fi monster. The moral lesson learned from this is that people need to blend in and feel connected to others in order to survive. In addition, humans must carefully consider the cost of scientific progress.

AbstractFlocculants are chemicals that mediate flocculation process, by aggregating colloids from suspension to form floc. Chemical flocculants are hazardous to the environment, which inform the search for safer and eco-friendly alternatives from microorganisms. Bacterial strains were isolated from water and sediment samples collected from Sodwana Bay, South Africa, and physiological properties of the bacterial strains were observed. Flocculation test using kaolin clay suspension was done on all isolates and the ones that showed flocculating activity were identified molecularly using 16 rRNA gene sequence analysis. Forty marine bacteria isolates were gotten from sediments and water samples collected from Sodwana Bay. Most of the isolates exhibited a range of colony pigmentation (pink, creamy, yellow, and white). After purification of individual isolates, they were screened for their potential to produce bioflocculant. The result revealed that isolates marked SOD3, SOD10, SOD12, SOD26, SOD27, SOD28, SOD32, SOD33 and SOD34 produced bioflocculants as shown by the flocculating activities from their crude extract. All these isolates showed good flocculation of kaolin clay suspension above 60% (flocculating activity) except SOD12. These bioflocculant producing isolates were identified asPseudoalteromonas sp,Alcaligenes faecalis,Bacillus subtilis,Bacillus cereus,Bacillus stratosphericus. The results showed Sodwana Bay, South Africa as a reservoir of bacteria with potential to produce flocculants. However, further studies on the optimisation of culture conditions for bioflocculant production, extraction, characterisation and application of isolates is on the way to underscore the biotechnological importance of these microbes as producers of substitutes to harmful chemical flocculants commonly used in water and wastewater treatment.

There is a growing concern that exposure to particulate matter of aerodynamic diameter of less than 2.5 µm (PM2.5) with biological composition (bioaerosols) may play a key role in the prevalence of adverse health outcomes in humans. This study determined the bacterial and fungal concentrations in PM2.5 and their inhalation health risks in an industrial vicinity in South Africa. Samples of PM2.5 collected on a 47-mm glass fiber filter during winter and summer months were analysed for bacterial and fungal content using standard methods. The health risks from inhalation of bioaerosols were done by estimating the age-specific dose rate. The concentration of bacteria (168–378 CFU/m3) was higher than fungi (58–155 CFU/m3). Bacterial and fungal concentrations in PM2.5 were lower in winter than in the summer season. Bacteria identified in summer were similar to those identified in winter: Staphylococcus sp., Bacillus sp., Micrococcus sp., Flavobacterium sp., Klebsiella sp. and Pseudomonas sp. Moreover, the fungal floras identified include Cladosporium spp., Aspergillus spp., Penicillium spp., Fusarium spp. and Alternaria spp. Children inhaled a higher dose of bacterial and fungal aerosols than adults. Bacteria and fungi are part of the bioaerosol components of PM2.5. Bioaerosol exposure may present additional health risks for children.

In recent times, diverse agriculturally important endophytic bacteria colonizing plant endosphere have been identified. Harnessing the potential of Bacillus species from sunflower could reveal their biotechnological and agricultural importance. Here, we present genomic insights into B. cereus T4S isolated from sunflower sourced from Lichtenburg, South Africa. Genome analysis revealed a sequence read count of 7 255 762, a genome size of 5 945 881 bp, and G + C content of 34.8%. The genome contains various protein-coding genes involved in various metabolic pathways. The detection of genes involved in the metabolism of organic substrates and chemotaxis could enhance plant-microbe interactions in the synthesis of biological products with biotechnological and agricultural importance.

Groundwater in the Mooi River catchment is prone to mining, agricultural, municipal and septic tank pollution. In this study physico-chemical and microbiological parameters were determined using appropriate methods. Bacterial isolates were identified by 16S rRNA sequencing (heterotrophic plate count (HPC) bacteria and amoeba-resistant bacteria (ARB)) and multiplex polymerase chain reaction (Escherichia coli). Antibiotic resistance tests were also performed. Physico-chemical parameters were generally within target water quality ranges for drinking water. HPC bacteria ranged between 105 and 107 colony-forming units (cfu)/ml. E. coli were enumerated from Trimpark, School and Cemetery. The Blaauwbank borehole was negative for faecal streptococci. Pseudomonas spp. were most abundant in the bulk water. Opportunistic pathogens isolated included Pseudomonas aeruginosa, Acinetobacter, Aeromonas, Alcaligenes, Flavobacterium, Bacillus cereus and Mycobacterium spp. Varying patterns of antibiotic resistance were observed. Most HPC bacterial isolates were resistant to cephalothin and/or amoxicillin and a few were resistant to erythromycin and streptomycin. Pseudomonas spp. was also the most abundant ARB. Other ARBs included Alcaligenes faecalis, Ochrobactrum sp. and Achromobacter sp. ARBs were resistant to streptomycin, chloramphenicol, cephalothin, and/or amoxicillin compared to HPCs. The presence of E. coli and ARB in these groundwater sources indicates potential human health risks. These risks should be further investigated and quantified, and groundwater should be treated before use.

Endophytic bacteria is an excellent candidates for the biological control of pathogenic fungi in plantations. The objectives of this study were to isolate and examine anti-fungal activity of endophytic bacteria from oil palm plantations in South Kalimantan against Ganoderma boninense. This research was performed in three phases, i.e., isolation, selection, and assessment of endophytic bacteria isolates against Ganoderma boninense. A total of 126 colonies of endophytic bacteria were isolated. The result of the anti-fungal activity test with dual culture method demostrated that BKA 10 isolate had the largest inhibition zone (62.22%). Molecular identification by DNA analysis using 16S rRNA primers showed that BKA 10 is most closely related to Bacillus cereus. In conclusion, isolate with the best anti-fungal acitivity against Ganoderma boninense has the closest kinship with Bacillus cereus. Keywords: antifungal, dual culture, Bacillus cereus.

Microbial Cr(VI) reduction in groundwater aquifer media was investigated in microcosm reactors extracted from Cr(VI) contaminated sites in South Africa. The reactors were operated under an influent Cr(VI) concentration of 40 mg/L to simulate the current Cr(VI) level at the contaminated site. Near complete Cr(VI) removal was observed in microcosm reactors inoculated with Cr(VI) reducing bacteria from dried activated sludge collected from a treatment plant receiving periodic loadings of Cr(VI). The best performance was observed under low hydraulic loading (flow rate, Q=0.310 cm3/hr). Microbial culture characterisation results showed a change in culture composition after 17 days of reactor operation, indicating Bacillus and Lysinibacillus species as the most dominant organisms in reactors that reduced Cr(VI). The predominance of Bacillus and Lysinibacillus species was either due to resilience against toxicity or adaptation to the changing conditions in the reactor. This research was the initial step towards the development of an in situ bioremediation process to contain the spread of a Cr(VI) plume in a groundwater aquifer at contaminated site in Brits, South Africa. South Africa holds about 72% percent of the world’s chromium resources, the majority of which is mined in the North Eastern region of the country formally known as Transvaal.

Bacillus cereus is a group of ubiquitous facultative anaerobic spore forming Gram-positive rods commonly found in soil. It has been detected and implicated in several contaminated food products and raw milk in dairy farms and it causes foodborne gastroenteritis by producing several toxins. This study is aimed at characterizing virulence determinants of B. cereus from cow‟s raw milk. A total of 400 raw milk samples were collected in Fort Hare Dairy Trust and Middledrift Dairy Farm; and cultured on Polymyxin pyruvate Egg-Yolk Mannitol Bromothymol Agar (PEMBA) for 48 hours at 37°C. DNA was isolated from the isolates and 16S rDNA was amplified and sent to Central Analytical Laboratory for sequencing. The gyrB gene of B. cereus was also used to confirm the identity of the isolates. Antibiotic susceptibility profiles of the isolates together with virulence genes were investigated. Multilocus Sequence typing was used to investigate the genetic relatedness of some selected isolates. Furthermore, spores of the isolates were produced, harvested and their concentrations determined. All (100%) of the isolates were identified as having a 96-99% similarity to B. cereus, B. thuringiensis and B. anthracis using sequencing; while gyrB gene was observed in all (100%) of the isolates. Three virulence genes nheA, nheB, nheC encoding for non haemolysin enterotoxin were amplified in all (100%) the isolates. All (100%) of the isolates were susceptible to doxycycline, gentamycin, tetracycline, ciprofloxacin, chloramphenicol and streptomycin. Resistance to rifampicin and penicillin G was predominant with equal rate of 100%, while susceptibility to erythromycin, clindamycin and doxycycline ranged from 60% to 100%. The selected isolates were related and are descendants of the same ancestor. All (100%) the isolates produced spores. The B. cereus isolates contain virulence genes, has multiple antibiotic drug resistance and produce spores, which poses a health risk to the public and cannot be used as probiotics.

This study focuses on the isolation and characterization of bacteria from lignocellulosic biomass obtained from the sediments of the Tyume River in Alice, Eastern Cape and to determine those bacterial isolates with good potential for modification and decomposition of lignocellulosic biomass for industrial application. Several bacterial isolates were recovered and screened for ability to degrade various lignocellulosic materials. Nine of the isolates were positive for lignocellulolytic activity. Four isolates were cellulase positive and six were xylanase positive. Moreover, one isolate (SB1) was positive for both xylanase and cellulase activities and showed the best hydrolysis zone on solid media. This isolate was then chosen as the best and identified molecularly. The 16S rDNA sequence analysis indicated that SB1 was a Bacillus cereus species. Factors affecting the cellulose and xylanase enzyme production by the organisms were studied. The organisms produced the enzymes maximally at earlier hours of incubation (12-30 hr) and optimally at acidic pH (3-5) and at moderate temperatures (35-45ºC). SB1 appears to hold promise in the decomposition of lignocellulosic wastes.

Maize is the staple food for most South Africans. This implies that any damage to the maize crop will affect food security of many South Africans. Although Eastern Cape Province is not a traditionally maize producing area, smallholder farmers in the province produce it mostly for subsistence purposes and some sell the surplus on the local market or use it to secure other good through barter trading. In South Africa, insect-resistant Bt maize/yieldgard has been used commercially for approximately 10 years now. Available impact studies on Bt maize reveal that, this technology is beneficial not only to farmers but consumers of maize products as well. Welfare gains as well as positive effects for human health are realised by both groups. Due to the costs and effectiveness associated with traditional and conventional maize stem borer control methods, Bt technology has the potential to be part of the solution. This thesis has attempted to investigate the economic viability of planting Bt maize seeds under smallholder farming conditions and identify factors as well as perceptions relating to attributes of Bt maize and to analyze the relationships between those perceptions and choices regarding use of Bt technology. Data was collected from 90 households who were selected using purposive sampling through the use of the snowball method. To collect data, a questionnaire was administered through face-to-face interviews. Gross margin analysis revealed that Bt maize is a more profitable option as compared to conventional maize seeds. Furthermore, econometric analyses, through use of the binomial regression model revealed that perceptions could be used to distinguish between users and non-users of Bt maize seed in the Eastern Cape Province. Results of inferential analysis indicate that the statistically significant variables at 5% level are gene erosion, quality and nutrition of products and food labels for Bt maize products perceptions. On the other hand, low expenses, seed market availability and farmers’ knowledge perceptions were significant at 10%. These findings suggest that an adjustment in each one of the significant variables can significantly influence the probability of Bt maize adoption. In view of the research findings, several policy proposals are suggested to support policy formulation. Key words: Bacillus thuringiensis (Bt) maize, yieldgard, smallholder farmers, perceptions, Flagstaff, gross margin analysis, binomial logistic regression model, Eastern Cape Province.

There are apprehensions that genetic modification of maize with Bacillus thuringiensis (Bt) may have negative effects on soil biodiversity, ecosystem processes and functions. This study aimed at determining the effect of Bt maize crop, Bt maize residues and its genetic modification on microbial biomass carbon (MBC), selected enzyme activities, vesicular arbuscular mycorrhizal (VAM) fungi and N and P release patterns. The study was conducted under field, glasshouse and laboratory conditions. In 2010/2011 season, four maize cultivars; DKC 61-25B (Bt), DKC 61-24 (non-Bt), PAN 6Q-321B (Bt) and PAN6777 (non-Bt) were planted. Determination of MBC, enzyme activities and fungal spore count was done at 42, 70, and 105 days after planting (DAP). A loam soil amended with Bt or non-Bt maize leaf residues from a study of 2009/2010 season was incubated to investigate effects of Bt maize residues on MBC and soil enzyme activities. Leaf residues of Bt and non-Bt maize cultivars (DKC 61-25B, DKC 61-24, PAN 6Q-321B and PAN6777) were used and soil without residues was used as a control. Samples were collected at 7, 28 and 56 days of incubation (DOI). An incubation study was also carried out in the laboratory to determine the effect of Bt maize residues (i.e. leaf, stem and root) and its genetic modification on N and P release patterns. Residues of DKC 61-25B, DKC 61-24, PAN 6Q-321B and PAN6777and soil without residues as a control were incubated in the laboratory. After destructive sampling at 0, 7, 14, 28, and 56 DOI, N in the form of NH4-N and NO3-N and P mineralisation were determined. Amendment of soil with residues enhanced MBC (p < 0.05) at all the sampling dates. For example MBC increased from 95 in the control to 146.3 mg/kg in the DKC 61-25B treatment at the end of the glasshouse trial. In the field DKC 61-25B had 9.1 mg/kg greater MBC than DKC 61-24, while PAN 6Q-321B had 23.9 mg/kg more MBC than PAN6777 at the end of the trial. However, no differences (p < 0.05) were observed in enzyme activities under field and glasshouse conditions except for dehydrogenase that had greater activity where DKC 61-25B and PAN 6777 were grown. There were no differences between the type of residues (Bt and non-Bt) on enzyme activities tested. However, differences were observed among the sampling dates. No effects of Bt maize crop on fungal spore count were observed. Similarly no differences were observed in leaf, stem and root tissues composition between Bt and non-Bt maize cultivars. Net N and P mineralisation from Bt maize cultivars did not differ from that of non-Bt maize cultivars. However, differences were observed among the cultivars. The results of this study suggested that Bt maize with Bt MON810 event can be grown in the central region of the Eastern Cape (EC), South Africa without affecting MBC, soil enzyme activities, VAM, and release of N and P nutrients from its residues.

South Africa is the world's second largest exporter of fresh citrus and is ranked 14th in citrus production. Fungal pathogens such as Phytophthora and Pythium cause economic losses as a result of root rot and brown rot. Mycorrhizal fungi are specialized members of the fungal community forming a mutualistic relationship with plant roots. Mycorrhizal fungal structures are known to associate with other soil microorganisms and these may contribute to improved plant growth. A diverse group of bacteria that interact with the mycorrhizal fungi are known as Mycorrhizal Helper Bacteria (MHB). The aim of this study was to investigate the role of arbuscular mycorrhiza and associated bacteria isolated from spores and determine whether they had any plant growth promoting potential. A total of 19 bacteria were isolated from arbuscular mycorrhizal spores and were molecularly identified as belonging to several Bacillus, Micrococcus, Onchrobactrum and Staphylococcus sp. All bacterial isolates were tested for plant growth promotion abilities. One Bacillus isolate was able to solubilise phosphate. Four isolates Micrococcus sp, Micrococcus leteus, Ochrobacterum sp and Ochrobacterum antropi were able to produce Indole Acetic Acid and three isolates showed potential to reduce growth of Phytophthora nicotianae, P. citrocola and P. citrophthora in in vitro plate cultures. Further tests using culture supernatants of the Bacillus sp, Micrococcus sp and Bacillus cereus confirmed their ability to inhibit or reduce growth of the three Phytophthora species in a 96 well bioassay. Bacillus sp and Bacillus cereus were able to inhibit Phytophthora spp by 95 to 100 % and Micrococcus spp was able to decrease pathogen growth by 60 to 94 %. These bacterial isolates were further evaluated for plant growth promoting abilities on citrus rough lemon seedlings alone or in combination with arbuscular mycorrhizal inoculum. Bacterial and mycorrhizal inoculants influence the increase in shoot and root biomass. Bacillus cereus in combination with mycorrhizal inoculum significantly increased seedling shoot to root ratio while root biomass was significantly increased with mycorrhizal inoculation. Due to the short duration of the trial mycorrhizal colonisation could not be assessed. It is evident that selected combinations of bacteria and mycorrhizal fungi could promote citrus seedling growth and potentially improve seedling health. Further studies under nursery conditions are recommended.

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Entomopathogenic nematodes have the potential to be outstanding biocontrol agents against agricultural pest insects. Combined with their bacterial symbionts, these biocontrol agents have proven to be very effective against numerous pests. The nematodes belong to the families Steinernematidae and Heterorhabditidae, and are ideal to be used in, and integrated with, pest management systems. There is a dire need for new and innovative methods to control agricultural pests, as numerous pest insects have developed resistance against broad-spectrum insecticides. Together with the environmental impact of these insecticides and the safety aspect regarding humans and animals, the need to develop new technologies, including entomopathogenic nematodes for pest management, is high. In this study, the associated symbiotic bacteria of three entomopathogenic nematodes species were isolated, and the potential of two nematode species to be successfully mass cultured in liquid medium was evaluated. Regarding the symbiotic bacteria, results from the study showed that bacteria species from all three nematode species, Heterorhabditis noenieputensis, Steinernema khoisanae and Heterorhabditis zealandica, were novel. Heterorhabditis noenieputensis was isolated in the Mpumalanga province during a previous survey conducted in citrus orchards. The bacterium isolated from this nematode belongs to the genus Photorhabdus, and bear closest similarity (98.6%) to the type strain of P. luminescens subsp laumondii (TT01T). Photorhabdus luminescens subsp. noenieputensis subsp. nov., derives its name from the area where the nematode was sourced, namely the farm Springbokvlei, near the settlement Noenieput close to the Namibian border. Thus far, 85 Steinernema spp. have been described worldwide, including S. khoisanae which was isolated in the Western Cape province of South Africa. Four S. khoisanae strains, namely SF87, SF80, SF362 and 106-C, were used for characterisating the new bacteria from different localities in South Africa. Using the neighbor-joining method, all the strains were aligned with 97% homology to the 16S rRNA sequences of several Xenorhabdus- type strains, indicating that they belonged to the same genus. The multigene approach was used to distinguish between the Xenorhabdus spp. and partial recA, dnaN, gltX, gyrB and infB gene sequences of the various strains were analysed. The bacterium species was named Xenorhabdus khoisanae sp. nov. after the nematode from which it was isolated. The results showed that the third bacterium species, which was isolated from H. zealandica, was new. The sequence of the bacteria strain clustered with the type strains of P. temperata and P. asymbiotica, indicate that it belonged to the genus Photorhabdus. This is the first study to show that H. zealandica associates with a luminescent Photorhabdus species, rather than with the known non-luminescent P. temperata. The potential of H. zealandica and Steinernema yirgalemense mass culture in liquid was investigated. Results illustrated that H. zealandica and its P. luminescens symbiont can be successfully cultured in liquid. However, two generations occurred during the process time, instead of the desirable one-generation. The growth curve of the symbiotic bacteria during the process time was measured, in order to determine when the stationary phase was reached, with the results showing this to occur after 36 h. Therefore, the optimum amount of time required for inoculating the IJs and for aiding in maximum infective juvenile (IJ) recovery is 36 h for adding the nematodes post pre-culturing of the bacteria. Future research goals should be to increase the percentage recovery in liquid culture, which would increase the number of nematodes produced per ml, which would, therefore, reduce the processing time significantly. The results from mass culturing the second nematode species, S. yirgalemense, indicated an asynchronous nematode development in the first generation. Growth curves were performed with the symbiotic bacteria that showed the exponential phase of Xenorhabdus started after 15 h, and that, after 42 h, the stationary phase was reached, with an average of 51 × 107 cfu·ml-1. Bioassays were performed to compare the virulence between in vitro- and in vivo-produced nematodes, with the results showing that the in vitro-produced nematodes were significantly less virulent than were the nematodes produced in vivo. The success obtained with the production of S. yirgalemense in liquid culture can serve as the first step in the optimising and upscaling of the commercial production of nematodes in industrial fermenters. The last aim of the current study was to determine when Xenorhabdus reached the stationary phase, when it is grown in a 20-L fermenter, as this would be the optimum time at which to add the IJs of S. yirgalemense. Such characteristics as the effect of stationary phase conditions on the bacterial cell density and on the DO2 rate in the fermenter were investigated. The results showed that the stationary phase of Xenorhabdus was reached after 36 h at 30˚C, which took 6 h less than did the same procedures followed with the Xenorhabdus sp. cultured in Erlenmeyer flasks on orbital shakers. This is the first step toward the liquid mass culturing of S. yirgalemense in industrial-size fermenters. Data from this study indicated the optimum amount of time that is required for adding nematodes to the bacterial culture in the fermenter, and for ensuring the optimum recovery of IJs, as well as a subsequent high yield of nematodes within a minimum processing time. This is the first report of its kind to investigate comprehensively the successful liquid culture of two South African entomopathogenic nematode species for the sole purpose of evaluating potential commercialisation. Results emanating from this study could be used as groundwork in future, in combination with similar research such as culturing nematodes intensively in large fermenters.
AFRIKAANSE OPSOMMING: Entomopatogeniese nematodes het die potensiaal om as doeltreffende biologiese beheeragente teen sleutelplaaginsekte gebruik te word. Elke nematood werk interaktief met ‘n spesifieke bakterium. Entomopatogeniese nematodes, behorende tot die families Steinernematidae en Heterorhabditidae, is ideale kandidate vir gebruik in ‘n geïntegreerde plaagbestuurprogram. Tans is daar ʼn behoefte vir nuwe metodes vir die beheer van plaaginsekte, omdat meeste insekte reeds weerstand opgebou het teen bestaande plaagdoders. As gevolg van die negatiewe impak van plaagdoders op die omgewing, asook kommer oor veiligheid vir die mens en diere, is die ontwikkeling en gebruik van alternatiewe plaagbeheermiddels noodsaaklik. In die eerste deel van die studie word drie nuwe bakterie spesies geïsoleer en beskryf. Resultate van hierdie studie het aangetoon dat die bakterië spesies vanuit die nematode spesies, Heterorhabditis noenieputensis, Steinernema khoisanae, en Heterorhabditis zealandica, tot dusver onbeskryf was. Eersgenoemde, H. noenieputensis, is afkomstig van ʼn sitrusboord in die Mpumalanga Provinsie. Die bakterie hieruit geïsoleer behoort tot die genus Photorhabdus en is biologies verwant (98.6%) aan P. luminescens subsp laumondii (TT01T). Die bakterie is benaam as Photorhabdus luminescens subsp. noenieputensis nov. en is na die nematood waaruit dit geïsoleer is vernoem. Tot dusver is wêreldwyd 82 spesies van Steinernema spp. beskryf, insluitende S. khoisanae van die Weskaap provinsie. Vier bakterie isolate is van S. khoisanae, SF87, SF80, SF362 en 106-C geïsoleer. Die buur-koppeling metode was gebruik om te bepaal dat hierdie bakterie isolate tot 97% ooreenstem met verskeie isolate van Xenorhabdus se 16S rRNA DNS volgordebepalings. Om tussen Xenorhabdus spp. te onderskei is ʼn multi-geen benadering gebruik deur gedeeltelike recA, dnaN, gltX, gyrB en infB DNS basispaar volgordebepalings van die verskeie isolate te bepaal. Hierdie bakterie isolaat is soortgelyk ook vernoem as, Xenorhabdus khoisanae sp. nov., na die nematood waaruit dit geïsoleer is. Die derde onbekende bakteriële spesie is uit H. zealandica geïsoleer. Die DNS basispaar volgordebepaling van die 16S geen van SF41 toon aan dat dit in dieselfde groep as P. temperata en P. asymbiotica val en sodoende aan die genus Photorhabdus behoort. Hierdie is die eerste studie met die bevinding dat H. zealandica ook met ʼn ander bakterie spesie geassosieer kan word buiten die normale P. temperata spesie. Die tweede deel van die studie gaan oor die teling van twee nematood spesies, H. zealandica en Steinernema yirgalemense, en hulle is geëvalueer vir hulle potensiaal om geteel te word in ʼn vloeibare medium. Die resultate het gewys dat H. zealandica met sy P. luminescens simbiont suksesvol in vloeistof aangeteel kan word, ten spyte van die feit dat daar twee generasies ontwikkel het, in plaas van die meer ideale enkel generasie. Die groeikurwe van die simbiotiese bakterie was gemonitor om te bepaal wanneer die stasionêre fase bereik word. Die resultate toon dat hierdie fase na 36 uur bereik was. Dus was die infektiewe nematode larwes eers na 36 uur tot die vloeibare medium waarin die bakterie geteel was bygevoeg. Navorsing in die toekoms moet dus gefokus wees om die persentasie herwinning van die infektiewe larwes te verhoog. Dit sal daartoe lei dat meer nematodes per ml geproduseer kan word en ook die prosesseringstyd van die nematodes verminder. ʼn Tweede nematode spesie, S. yirgalemense, was ook in vloeistof geteel. Hier het ʼn asinkroniese ontwikkeling in die eerste generasie plaasgevind wat problematies is. Groeikurwes is bepaal van die bakteriële simbiont en die resultate het gewys dat die groeifase van Xenorhabdus na 15 uur in aanvang geneem het en dat die stasionêre fase bereik was na 42 uur met ʼn gemiddelde van 51 × 107 selle·ml-1. Die virulensie van nematodes wat in vitro geteel is, is vergelyk met die virulensie van nematodes wat in vivo geteel is en die resultate het getoon dat die in vitro geteelde nematodes minder virulent was. Die teling van S. yirgalemense in vloeistof was oor die algemeen meer suksesvol as die teling van H. zealandica in dieselfde medium. Die doelwit van die laaste gedeelte van hierdie studie was om te bepaal wanneer Xenorhabdus die stasionêre fase bereik wanneer dit in ʼn 20-L fermenter gekweek word. Dit bepaal sodoende die optimale tyd wanneer die infektiewe larwes van S. yirgalemense bygevoeg behoort te word. Die uitwerking van die stasionêre fase op die bakteriële selle, asook die DO2-konsentrasie in die fermenter, was geëvalueer. Resultate het gewys dat die stasionêre fase van Xenorhabdus na 36 uur bereik was, wat 6 uur korter is as toe dit gekweek is in Erlenmeyer flesse. Hierdie studie is die eerste stap om die massa teling van S. yirgalemense in industriële fermenters suksesvol te bemeester. Die data wat verkry was, het aangedui wat die ideale tydsduur sal wees om die bakteriegetalle te vermeerder voordat die nematode bygevoeg word. Hierdie is die eerste studie wat die teling van twee Suid-Afrikaanse nematode spesies omvattend in vloeistof evalueer het. Die hoof doelwit is om die potensiaal van hierdie nematode spesies, met die oog op kommersiële gebruik, te meet. Die resultate van hierdie studie kan gekombineer word met toekomstige studies in hierdie spesifieke navorsingsveld.

Thesis (MSc)--Stellenbosch University, 1997.
ENGLISH ABSTRACT: The activity of iron-oxidizing bacteria, for example, Thiobacillut. ferrooxidans, in the outer layers of coal waste dumps results in the oxidation of pyrite with the formation of large volumes of acid mine drainage. The process requires atmospheric oxygen and moisture. Acid mine drainage may possibly be controlled by creating unfavourable environmental conditions in dumps for the iron-oxidizing bacteria. The present research investigated the possibility of inhibiting these bacteria and consequently acid formation in coal waste dumps by means of different dump construction techniques. Physical and chemical conditions, acid formation and populations of four groups of bacteria which might produce acid were studied in the outer layers of ten differently constructed pilot scale coal waste dumps at the Kilbarchan Mine near Newcastle, Kwazulu-Natal, from September 1993 to July 1995. Dump covers consisting of a 30-cm or 70-cm layer of Estcourt soil of low permeability covered with 70 cm or 30 cm, respectively, of more permeable Avalon soil produced anaerobic conditions in the dumps throughout most of the 22 months of the test period, as did a cover of 70 cm compacted plus 30 cm uncompacted Avalon soil alone. An uncoMpacted 30-cm or compacted 50- cm Avalon soil cover proved ineffective in causing prolonged anaerobic conditions. Uncovered dumps showed only slight reduction of oxygen in the coal waste after heavy rains. Pockets of acidity were detected on several occasions in the coal waste below the 50-cm Avalon soil layer from the time of construction and progressively increasing acidity in the uncovered dumps and the waste below the 30-cm Avalon soil cover. Iron-oxidizing bacterial populations of the T. ferrooxidans type have tended to be higher in the uncovered dumps and Avalon soil-covered dumps showing acidification than in the non-acidified dumps covered with 1 m of Avalon soil or Avalon and Estcourt soil. Associated populations of iron-oxidizing bacteria of the Metallogenium type, acidophilic and non-acidophilic thiosulphate-oxidizing bacteria were generally low in the coal waste of the dumps. Thus, five of the soil covers, all with a thickness of 1 m, but not covers with a thickness of 0.5 m or less, proved effective for almost 2 years in inhibiting the diffusion of oxygen to the underlying coal waste in the pilot scale dumps and also appeared to suppress the populations of iron-oxidizing bacteria believed to be implicated in acid formation in the coal waste. These results suggest that coal waste dumps in South Africa should be covered with soil layers of 0.5-1.0 m thick to prevent the generation of acid mine drainage.
AFRIKAANSE OPSOMMING: Die aktiwiteit van ysteroksiderende bakteriee soos Thiobacillus ferrooxidans, in die buitenste lae van steenkoolafvalhope, veroorsaak die oksidasie van piriet met die gevolg dat groot volumes suur mynafloopwater gevorm word. Hierdie proses benodig suurstof en vog. Suur mynafloopwater kan moontlik beheer word deur 'n situasie te skep waar die toestande in die hope ongunstig is vir die ysteroksiderende bakteriee. Die huidige navorsing het die moontlikheid ondersoek om hierdie bakteriee te inhibeer deur verskillende afvalhoopontwerpe op die proef te stel en sodoende suurvorming in steenkoolmynhope te beperk. Die fisiese en chemies kondisies, suurvorming en populasies van vier verskillende bakterie-groepe wat dalk by suurvorming betrokke is, is vanaf September 1993 tot Julie 1995 bestudeer in die buitenste lae van tien verskillend gekonstrueerde loodsskaalafvalhope by die Kilbarchan myn naby Newcastle in KwaZulu-Natal. Afvalhoopbedekkings bestaande uit 'n 30-cm of 70-cm Estcourt grond met 'n lae permeabiliteit bedek met'n 70-cm of 30-cm laag van meer deurlaatbare Avalon grond het anaerobe kondisies veroorsaak. Ongekompakteerde 30-cm en gekompakteerde 50-cm Avalon grondlae het egter nie bestendige anaerobe kondisies in die hope veroorsaak nie. Die onbedekte hope het aerobics gebly met slegs effense dalings van suurstofkonsentrasies gedurende en na swaar reens. Geisoleerde monsters uit die steenkoolafval onder die 50-cm Avalon grondlaag het vanaf die begin van die toetsperiode tekens van suurvorming getoon. Die onbedekte steenkoolafval en die van die sel met 'n 30-cm Avalon grondlaag het met verloop van tyd al hoe meer suur geword. Die ysteroksiderende bakterie-populasies van die T. ferrooxidans tipe het geblyk om in die onbedekte en Avalon grondbedekte hope wat tekens van suurvorming getoon het hoer te wees as in die hope wat met 'n 1-m laag Avalon grond of Avalon en Estcourt grond bedek is en geen tekens van suurvorming getoon het nie. Ysteroksiderende bakteriepopulasies van die Metallogenium tipe, nieasidofiele en asidofiele tiosulfaatoksiderende populasies was oor die algemeen laag in die steenkoolafvalhope. Vyf van die grondlae wat alma! 1 m dik was het dus geblyk om effektief te wees in die bekamping van die infiltrasie van suurstof na die onderliggende steenkoolafval in die loodskaalhope. Dit lyk asof daardie lae die ysteroksiderende populasies betrokke by suurvorming onderdruk het. Die 0.5-m grondbedekking het egter nie so 'n sterk onderdrukkende effek op die suurstofinfiltrasie of die bakteriepopulasie gehad nie. Na aanleiding van hierdie resultate blyk dit dat steenkoolafvalhope in Suid-Afrika met minstens 0.5 tot 1..0 m grond bedek moet word om effektief die probleem van suur mynafloopwater te bekamp.

M. Tech. (Biotechnology, Department of Biosciences, Faculty of Applied and Computer Sciences), Vaal University of Technology.
The Organization for Economic Co-operation and Development (OECD) and the Food and Agriculture Organization (FAO) of the United Nations predict that milk production and the dairy sector will remain one of the fastest-growing agricultural subsectors over the coming decade. The global milk production is projected to expand over the 2011-2020 period at an annual rate of 2%. In South Africa alone, approximately 14 – 15 million litres of milk are wasted annually due to microbial spoilage. Therefore, the identification of the spoilage microorganisms in the milk products is necessary. This will contribute towards the design of appropriate measures to prevent wastage due to spoilage and in turn contribute towards sustainability of the sector. Accordingly, one hundred samples of spoiled full cream UHT milk were collected from two plants of each of the two largest milk processors. These samples were examined visually, and the pH was measured. A presumptive identification up to genus level was conducted by examining morphological features and conducting Gram-stain, catalase and oxidase tests. Species-specific identification was done by using the Analytical Profile Index and Biolog system. Molecular profiling was done by sequencing the rDNA genes. The main spoilage organisms identified in the samples were Pseudomonas, Micrococcus, Bacillus, Enterococcus and Lactobacillus. All organisms belonging to the five genera were psychrotrophs, which are commonly found in biofilms in UHT milk processing equipment. Therefore, according to the study, the spoilage bacteria apparently entered into the milk due to inadequate cleaning-in-place (CIP) processes. More importantly, further studies should be conducted in order to identify the spoilage microbes and how CIP processes can be improved.

Fourteen spore-forming bacterial strains were isolated and screened for entomopathogenic activity. Five displayed toxicity towards the common mealworm, Tenebrio molitor L., (Coleoptera: Tenebrionidae). The majority of the isolates were obtained from insect larvae and insect rich environments. The three bacterial species identified were Bacillus thuringiensis Berliner, Brevibacillus laterosporus Laubach and Bacillus cereus Frankland and Frankland. Bioassays were conducted using T. molitor larvae. The one isolate of B. cereus required the highest concentration of bacterial cells to achieve its LC50, whereas one of the isolates of B. laterosporus required the lowest cell concentration to achieve its LC50. Dose response curves were generated for the five best isolates, which showed that the isolate of B. laterosporus (NDR2) was substantially more toxic than the other isolates.
Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2009.

Anthropogenic activities generate waste products that pollute the environment with bacteria and heavy metals. This research assessed pollution of the Kahwa River, Bukavu Town, DRC with cadmium and lead (HMs) and bacterial enteropathogens. A survey of businesses, households and healthcare facilities showed general use of the river to remove effluent and waste. Indicator organisms were cultured at over 200 cfu/100 ml showing faecal contamination of the river water. Antibiotic resistance was shown by enteropathogenic Vibrio cholerae and Salmonella typhi to ampicillin and cotrimoxazole with some sensitivity shown to ciprofloxacin. River water contained HMs at around 40 times the World Health Organisation limit for drinking water. The bacteria, particularly from river sediment, tolerated HMs up to a concentration of 1.5 mg/ml. The presence in the Kahwa River of antibiotic-resistant pathogens showing tolerance to HMs has serious public health implications
Environmental Management
M.Sc. (Environmental management)