Littérature scientifique sur le sujet « Didermes »

Diderma is one of the most abundant species in Myxomycetes. Based on the study of morphology and phylogeny, two new species—Diderma liaoningensis (is characterized by grouped sporocarps, the sporocyst with dehiscence lines, capillitium with large brown swelling, spore encircled by a pale line) and Diderma verrucocapillitia (is characterized by depressed plasmodiocarps, verrucose capillitium, red-brown spores)—collected from Liaoning province and Jilin province were introduced. Detailed descriptions and illustrations are presented as well as comparisons to similar species. Phylogenetic analyses were carried out using Maximum Likelihood and Bayesian inference based on small subunit ribosomal RNA sequences (SSU rRNA) of Diderma and related genera. These analyses confirmed the placement of two new species in the genus Diderma. A key to 19 species of Diderma from China is also provided. Holotype specimens have been housed in the Herbarium of the Mycological Institute of Jilin Agricultural University (HMJAU), Changchun, China.

Lyme disease is the leading tick-borne infection in the United States, caused by the pathogenic spirochete Borreliella burgdorferi, formerly known as Borrelia burgdorferi. Diderms, or bacteria with dual-membrane ultrastructure, such as B. burgdorferi, have multiple methods of transporting and integrating outer membrane proteins (OMPs). Most integral OMPs are transported through the β-barrel assembly machine (BAM) complex. This complex consists of the channel-forming OMP BamA and accessory lipoproteins that interact with the five periplasmic, polypeptide transport-associated (POTRA) domains of BamA. Another system, the translocation and assembly module (TAM) system, has also been implicated in OMP assembly and export. The TAM system consists of two proteins, the BamA paralog TamA which has three POTRA domains and the inner membrane protein TamB. TamB is characterized by a C-terminal DUF490 domain that interacts with the POTRA domains of TamA. Interestingly, while TamB is found in almost all diderms, including B. burgdorferi, TamA is found almost exclusively in Proteobacteria. This strongly suggests a TamA-independent role of TamB in most diderms. We previously demonstrated that BamA interacts with TamB in B. burgdorferi and hypothesized that this is facilitated by the BamA POTRA domains interacting with the TamB DUF490 domain. In this study, we utilized protein-protein co-purification assays to empirically demonstrate that the B. burgdorferi TamB DUF490 domain interacts with BamA POTRA2 and POTRA3. We also observed that the DUF490 domain of TamB interacts with the accessory lipoprotein BamB. To examine if the BamA-TamB interaction is more ubiquitous among diderms, we examined BamA-TamB interactions in Salmonella enterica serovar Typhimurium (St). Interestingly, even though St encodes a TamA protein that interacts with TamB, we observed that the TamB DUF490 of St interacts with BamA in this organism. Our combined findings strongly suggest that the TamB-BamA interaction occurs independent of the TamA component of the TAM protein export system.

Abstract A new species of Diderma (Physarales, Didymiaceae) was recorded in the Mata Estrela Private Nature Reserve, Rio Grande do Norte state. It is characterized by sessile sporangia, white globose columella, capillitium irradiating from the peridium, forming three layers, the middle part strongly calcareous, the outer layer cartilaginous and the inner layer membranous. A key to species of sessile sporangia Diderma with triple peridium is presented.

Two specimens of a rare species Diderma aurantiacum collected in the Sikhote-Alin Nature Reserve and the territory of the Land of the Leopard National Park (Primorye Territory, Russian Federation) were found during revision of the myxomycete collection of the Mycological herbarium of the Komarov Botanical Institute (LE). These specimens are the first records of this species outside the Japanese islands. Diderma aurantiacum is characterized by a thick cartilaginous peridium of dull orange color that breaks into petal-like fragments during dehiscence, a small hemispherical columella, weakly branched dark capillitial threads with pale tips, and warted spores with darker warts arranged in small groups. The color photographs of sporocarp structures and SEM images of spores and capillitium are published for the first time. The partial nucleotide sequences of nrSSU (18S rDNA) and EF1α genes of specimens from the Russian Far East differed clearly from these of other Diderma species.

Specimens of myxomycetes obtained as field collections or from moist-chamber cultures during surveys for these organisms carried out at several localities in New Zealand have yielded eight species not included in the monograph of the group published in 2003. One other species, listed provisionally as Diderma cf. miniatum on the basis of a single, rather limited collection, but now known from several additional collections, is described herein as Diderma novae-zelandiae. These new records bring the number of myxomycetes reported from New Zealand to 196 species.

L'enveloppe bactérienne est essentielle à de nombreuses fonctions cellulaires, comme le maintien de l'intégrité structurelle, la division cellulaire, la motilité, l'absorption des nutriments et la communication. Elle joue également un rôle crucial dans la pathogénicité bactérienne, faisant de son assemblage et de son maintien un domaine de recherche clé pour le développement de nouveaux antimicrobiens. Les enveloppes bactériennes présentent une dichotomie unique entre les structures monodermes (membrane unique) et didermes (double membrane). Traditionnellement, cette distinction correspond aux bactéries à Gram-positif (monodermes) et à Gram-négatif (didermes). On considérait initialement que les bactéries didermes avaient évolué à partir des monodermes par complexification progressive. Cependant, des études phylogénomiques récentes montrent que le dernier ancêtre commun bactérien (LBCA) était probablement déjà un diderme, et que la transition vers une structure monoderme s'est produite via des pertes indépendantes de la membrane externe (ME). Ces transitions ont principalement eu lieu chez les Terrabacteries, un sous-domaine regroupant des phylums comme les Cyanobactéries, Firmicutes et Actinobactéries. Les raisons de ces pertes d'ME chez les Terrabacteries restent floues, mais pourraient être liées à des mécanismes de biogenèse de la ME encore inconnus. Dans ma thèse, j'ai étudié la biogenèse de la ME sur deux modèles de Terrabacteries. Le premier est Veillonella parvula, une bactérie diderme du microbiome humain appartenant aux Firmicutes, mieux connus pour leurs modèles monodermes (Bacillus, Staphylococcus). J'ai caractérisé deux gènes (lap1 et lap2), associés aux didermes dans une analyses bioinformatique précédemment réalisée par le laboratoire, et montré leur rôle dans la biogenèse de la ME. J'ai montré que Lap1 et Lap2 sont localisés respectivement à la membrane cytoplasmique et à la ME. De manière surprenante, les mutations de Lap1-2 ont été compensées par des gènes de biosynthèse des lipides, y compris PlsA, une enzyme récemment découverte de synthèse d'étherlipides. Bien que je n'aie pas pu établir un lien direct entre plsA et la biogenèse de la ME, j'ai pu démontrer son rôle dans la résistance au stress oxydatif chez les bactéries. J'ai aussi développé un système CRISPR/Cas9 ciblant PlsA en profitant d'un test colorimétrique différentiel pour le WT et mutant de délétion plsA. De plus, j'ai identifié un nouveau transporteur putatif de glycérophospholipides et montré qu'il devenait essentiel en absence des protéines AsmA-like, suggérant un rôle dans le transport de ces lipides. J'ai également constaté que les Terrabacteria possédaient souvent une seule copie des protéines AsmA-like, tandis que les Gracilicutes en avaient plusieurs, suggérant l'existence d'autres transporteurs de glycérophospholipides. Le second modèle que j'ai étudié est Deinococcus radiodurans, une bactérie appartenant au phylum Deinococcota, dont l'enveloppe se distingue des modèles didermes classiques. J'ai retracé l'évolution du transporteur Lpt chez les Deinococcota, montrant qu'il s'est dupliqué avec un complexe prédit pour être impliqué dans le transport du lipopolysaccharide (LPS), et l'autre possédant un substrat encore inconnu. J'ai également montré que les Deinococcota ont perdu le LPS trois fois indépendamment. En étudiant les transporteurs Lpt chez D. radiodurans, j'ai découvert que le complexe impliqué autrefois dans le transport des LPS n'était pas important pour cette bactérie, tandis que la suppression du second complexe entraînait des défauts sévères. J'ai proposé que ce dernier soit impliqué dans l'exportation des lipoprotéines, basé sur des analyses de mutations compensatoires, la cryo-EM et la spectrométrie de masse
The bacterial envelope is essential for numerous cellular functions, including maintaining structural integrity, cell division, motility, nutrient uptake, and communication. It also plays a key role in bacterial pathogenicity, making its assembly and maintenance a critical area of research for new antimicrobial development. Bacterial envelopes exhibit a significant dichotomy, unique to the bacterial domain, between monoderm (single membrane) and diderm (double membrane) structures. Traditionally, this divide has been classified as 'Gram-positive' (monoderm) and 'Gram-negative' (diderm). Historically, it was thought that diderm bacteria evolved from monoderms through a gradual increase in complexity. However, recent phylogenomic studies challenge this view, suggesting that the last bacterial common ancestor (LBCA) was already a diderm, and that the shift to a monoderm architecture occurred through multiple independent losses of the outer membrane (OM). Interestingly, all these diderm-to-monoderm transitions are confined to the Terrabacteria subdomain, which includes phyla such as Cyanobacteria, Firmicutes, and Actinobacteria. The reasons for these OM losses specifically in Terrabacteria remain unknown but may be linked to unknown mechanisms unique to the OM biogenesis in this group. In my thesis, I studied the outer membrane biogenesis of two Terrabacteria model. The first model is Veillonella parvula, a diderm from the human microbiome that belongs to the Firmicutes which are better known for their monoderm models (Bacillus, Staphylococcus). I characterized two genes of unknown function (lap1 and lap2) which were previously associated to diderms in a bioinformatical analyses and found that they were involved in OM biogenesis and localized at the cytoplasmic membrane and OM respectively. Surprisingly, the deletions mutant of Lap1-2 was suppressed by lipid biosynthesis genes including a recently identified ether-lipid synthesis enzyme PlsA. While I could not associate the function of plsA in OM biogenesis, I could demonstrate its function in oxidative stress resistance for the first time in Bacteria. I also used a differential colorimetric assay between the WT and plsA deletion mutants to develop CRISPR/Cas9 using plsA as a target. I also identified a putative a new type of glycerophospholipid transporter and obtained preliminary data suggesting it becomes essential in a genomic background devoid of all copies of the recently discovered glycerophospholipid transporter family AsmA-like supporting its putative role. I also showed that AsmA-like proteins have higher copy numbers in Gracilicutes while Terrabacteria often have a single copy or none suggesting the existence of more glycerophospholipid transporters than previously known. Interestingly the newly identified putative transporter was more abundant in Terrabacteria. The second model I studied is Deinococcus radiodurans, a bacterium belonging to the phylum Deinococcota and whose envelope differs significantly from classical diderm models. I was able to retrace the evolutionary history of the lipopolysaccharide transporter Lpt in Deinococcota as I showed that it duplicated in this phylum with one complex predicted to be involved in LPS transport while the other was predicted to possess an unknown substrate. I showed that Deinococcota have lost LPS three times independently and studied the function of both Lpt transporters in D. radiodurans which has lost LPS. I found that the complex which used to be involved in LPS transport was not crucial to the physiology of D. radiodurans while the other complex led to grave defects in the bacterium when deleted. I suggested that this second complex is involved in lipoprotein export to the surface based on suppressor assays, cryo-EM and mass spectrometry

L’enveloppe bactérienne est l’une des structures cellulaires les plus anciennes et les plus fondamentales. Toutefois, de nombreux aspects concernant sa diversité et son histoire évolutive sont encore inconnus. Dans cette thèse, j’ai profité du nombre croissant de génomes disponibles dans les bases de données publiques, afin de mener une analyse de phylogénomique et de génomique comparative à une large échelle évolutive. Les deux objectifs de ce travail doctoral étaient (i) d’identifier de nouvelles lignées didermes au sein des Firmicutes pour éclairer la transition monoderme/diderme, et (ii) d’élucider l’histoire évolutive de l’enveloppe cellulaire chez les bactéries et d’en déduire la nature chez le LBCA.En résumé, les résultats que j'ai obtenus au cours de cette thèse fournissent une avancée significative dans notre compréhension de la diversité et de l'évolution de l'enveloppe cellulaire, et sur l'une des transitions majeures de l'histoire des bactéries, celle entre les monodermes et les didermes
The bacterial envelope is one of the oldest and most fundamental cellular structures. Yet, many aspects of its diversity and evolutionary history are unknown. In this thesis I have taken advantage of the large available genomic data to investigate the issue through a large-scale phylogenomic and comparative genomic analyses at the level of Bacteria. The two goals of this doctoral work were (i) to identify putative new diderm lineages in the Firmicutes to illuminate the monoderm/diderm transition, and (ii) to elucidate the evolutionary history of the cell envelope in Bacteria and infer its nature in the LBCA. To sum up, the results I obtained during this thesis provide a timely and significant advancement to our understanding of the diversity and evolution of the cell envelope, and on one of the major transitions in the history of Bacteria, that between monoderms and diderms

Миксомицеты — широко распространенная в наземных экосистемах группа хищных амебоидных протистов, систематика которых основана главным образом на морфологических признаках их макроскопических спороносящих стадий (спорокарпов), которые возможно обнаружить в полевых условиях невооруженным глазом или получить в лаборатории методом влажных камер. Первые сведения о миксомицетах Приморья содержатся в работе Н. А. Наумова [4], опубликованной по результатам экспедиции по Южно-Уссурийскому краю, осуществленной им в 1912 году. В советское время миксомицеты Приморья не становились предметом специального изучения, однако некоторые сообщения о них встречались в работах микологов А. А. Аблакатовой, И. А. Бункиной и Э. З. Коваль [1 и др.]. Позднее достаточно хорошо были исследованы миксомицеты Лазовского [2, 3] и Сихотэ-Алинского [5] заповедников. Сведения же о миксомицетах заповедника «Кедровая Падь» до последнего времени ограничивались списком из 19 видов, обнаруженных в 1955–1960 годах Э. З. Коваль [1]. Для более полноценного их изучения в 2016, 2017 и 2020 годах в заповеднике были осуществлены полевые исследования, в ходе которых было собрано 2147 образцов плодовых тел миксомицетов и 719 образцов различных субстратов: гнилой древесины, наземного опада и коры живых деревьев и кустарников 34 видов. В ходе камеральной обработки этих субстратов при помощи метода влажных камер было получено и собрано дополнительно 1554 образца спороношений миксомицетов. Всего в ходе исследований в заповеднике «Кедровая Падь» было выявлено 172 вида миксомицетов из 36 родов, 13 семейств и 9 порядков, что составляет 36% от числа видов, известных в России на данный момент. Из обнаруженных видов большинство (95%) были новыми для заповедника, 63 вида — новыми для Приморского края и 29 — для России. Семь видов из родов Diderma Pers., Licea Schrad. и Trichia Haller были описаны как новые для науки. Наиболее высокое разнообразие миксомицетов было выявлено в коренных хвойно-широколиственных сообществах, а в экологической группе кортикулоидных миксомицетов наибольшее число видов было отмечено на коре Abies holophylla Maxim., Quercus mongolica Fisch. ex Ledeb. и Chosenia arbutifolia (Pall.) A. Skvorts. (40, 40 и 27 видов, соответственно).

Introdução: Cocos nucifera L., é considerada uma das frutíferas mais difundidas mundialmente. A importância socio-econômica do coqueiro deve-se à produção de diversos produtos e sub-produtos oriundos de diferentes partes da planta, principalmente, do fruto, utilizado nas agroindústrias e in natura como alimento para a população. As doenças do coqueiro são fatores limitantes no desenvolvimento desta cultura, afetando de forma direta e negativa a produção dos frutos e, consequentemente, trazendo prejuízos significativos para os produtores. O registro acerca do potencial antagônico direto para espécies de myxomycetes é extremamente limitado, sendo ainda mais restrito o conhecimento deste potencial para o bio-controle de fungos fitopatogênicos de interesse agronômico. Objetivos: Com o intuito de contribuir para o desenvolvimento do conhecimento científico acerca do bio-controle de fungos fitoaptogênicos e o potencial biocontrolador dos mixomicetos, o plasmódio de Diderma chondrioderma (de Bary & Rostaf) G. Lister foi testado in vitro como antagonista de ascomiceto patógeno a plantas de interesse econômico. Materiais e métodos: A espécie de fungo foi isolada de folhas sintomáticas de Cocos nucifera L., identificada como Neopestalotiopsis foedans (Sacc. & Ellis) Maharachch. (Amphisphaeriales, Ascomycota) com base em caracteres morfológicos e análise filogenética (ITS, β-tubulina e TEF) e testada a sua patogenicidade, a qual foi confirmada para o hospedeiro. Resultados: Após a primeira semana de observação, registrou-se o crescimento considerável da colônia do fungo inoculado e a migração do plasmódio na direção do micélio, em todas as placas testes. No início da segunda semana foi evidenciada, em todas as culturas, atividade predatória exercida pelo plasmódio contra o fungo. Observou-se a sobreposição do micélio pelo plasmódio e excreção de material fagocitado, na medida em que o mesmo avançava pela colônia. Os conídios foram fagocitados, juntamente com o micélio e facilmente vistos no fluxo do conteúdo citoplasmático do plasmódio, impedindo a esporulação do fungo. Após a cobertura total dos micélios e conídios pelos plasmódios, as colônias se tornaram inviáveis e não apresentaram crescimento quando inoculadas em BDA. Conclusão: Este estudo apresenta o primeiro registro de atividade antagônica para a espécie D. chondrioderma além do primeiro relato de bio-controle acerca da espécie N. foedans, patógena a C. nucifera.