7.9
Phylum bactérien Verrucomicrobia
Le phylum Verrucomicrobiota comprend au moins quatre ordres caractérisés, dont la majorité des espèces sont classées dans l’ordre des Verrucomicrobiot…
L’embranchement Verrucomicrobiote est classé en quatre ordres, la plupart des espèces étant classées dans l’ordre Verrucomicrobiales.
Les espèces de cet embranchement sont des bactéries aérobies obligatoires ou facultatives largement réparties dans divers environnements, y compris l’eau douce, les habitats marins, les sols forestiers et les terres agricoles.
Les espèces de verrucomicrobiote contribuent au cycle du carbone. De nombreuses espèces fermentent les sucres, tandis que les méthanotrophes aérobies comme le genre Methylacidiphilum oxydent le méthane.
Il est intéressant de noter que les espèces du Verrucomicrobiote possèdent des extensions cytoplasmiques membranaires appelées prothèses. Ces appendices sont soutenus par le peptidoglycane dans leurs parois cellulaires.
Les genres Verrucomicrobium et Prosthecobacter sont remarquables pour produire plusieurs prothèses sur chaque cellule.
Elles subissent une division cellulaire symétrique, de sorte que les cellules mères et filles possèdent des prothèses au moment de la division.
Les espèces de Prosthecobacter ont deux gènes qui présentent une homologie significative avec les gènes codant pour la tubuline dans les cellules eucaryotes. Mais leur fonction reste incertaine, car aucun cytosquelette de type eucaryote n’a été observé chez ces bactéries.
View the full transcript and gain access to JoVE Core videos
Q1: What are the main characteristics of the phylum Verrucomicrobiota?
Verrucomicrobiota comprises at least four characterized orders, with most species in the order Verrucomicrobiales. Members are aerobic or facultatively aerobic bacteria distributed across freshwater, marine habitats, forest soils, and agricultural lands. A distinctive feature is their possession of cytoplasmic extensions called prosthecae, supported by peptidoglycan in cell walls, distinguishing them from bacterial phylum planctomycetes.
Q2: How do Verrucomicrobium and Prosthecobacter differ from other bacteria in cell division?
Verrucomicrobium and Prosthecobacter undergo symmetrical cell division, resulting in both mother and daughter cells possessing prosthecae at division time. This contrasts with Caulobacter, which develops a single prostheca and releases flagellated swarmer cells lacking prosthecae. The name Verrucomicrobium derives from Greek meaning warty, describing their multiple protruding prosthecae.
Q3: What metabolic roles do Verrucomicrobiota species play in their environments?
Verrucomicrobiota species contribute significantly to carbon cycling through diverse metabolic pathways. Many species ferment sugars for energy, while aerobic methanotrophs like Methylacidiphilum oxidize methane. Additionally, some Verrucomicrobiota establish symbiotic relationships with protists, expanding their ecological roles and nutrient cycling capabilities across diverse habitats.
Q4: What are prosthecae and how are they structured in Verrucomicrobiota?
Prosthecae are membrane-bound cytoplasmic extensions characteristic of Verrucomicrobiota. These appendages are supported by peptidoglycan in their cell walls, distinguishing them from similar structures in other bacteria. The genera Verrucomicrobium and Prosthecobacter produce multiple prosthecae on each cell, giving them their distinctive warty appearance.
Q5: Why are tubulin-like proteins in Prosthecobacter significant?
Prosthecobacter species possess two genes exhibiting strong similarity to eukaryotic tubulin genes, the primary protein forming eukaryotic cytoskeletons. These bacterial tubulin-like proteins show greater structural resemblance to eukaryotic tubulin than the bacterial FtsZ protein. However, their function remains unclear since no eukaryotic-like cytoskeleton has been observed in these bacteria.
Q6: How is Verrucomicrobiota classified within the broader bacterial taxonomy?
Verrucomicrobiota is classified into four orders, with most species in the order Verrucomicrobiales. Classification relies on molecular and morphological characteristics examined through methods of classification and identification. Understanding their classification helps contextualize their role within microbial diversity and their relationships to other bacterial groups.
Q7: What distinguishes Verrucomicrobiota from Planctomycetes?
Both Verrucomicrobiota and Planctomycetes possess membrane-bound intracellular structures. However, Verrucomicrobiota's distinctive feature is cytoplasmic extensions called prosthecae supported by peptidoglycan in cell walls. This structural difference sets Verrucomicrobiota apart and reflects their unique evolutionary adaptations within bacterial diversity and ecological niches.