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PlanctomycesRANK: GenusTAXONOMY: Bacteria -> PVC group -> Planctomycetes -> Planctomycetia -> Planctomycetales -> Planctomycetaceae -> Planctomyces OVERVIEW: Cells are spherical, ovoid, ellipsoidal, teardrop-shaped, or bulbiform. Often relatively large (ignoring appendages and aggregations, individual vegetative cells range up to 3.5 µm in greatest dimension; immature buds smaller). Have at least one major multifibrillar (nonprosthecate) appendage (called a spike, spire, fascicle, bristle, or stalk) which does not always have the true stalk function of connecting the cell to a substratum. Divide by budding. A holdfast-which is not always an easily visualized, discrete structure-is often present at the distal end of an appendage or at one end of the cell. Often form homologous aggregations, rosettes or bouquets, by attachment at the holdfasts in natural habitats. Produce crateriform surface structures (surface pits 12 nm in diameter, circumscribed by a grommet with a 30–36 nm outside diameter) and pili in characteristic patterns. Gram-stain-negative bacteria. Lack peptidoglycan. Resistant to β-lactam antibiotics. Divide by budding. Some species have a dimorphic life cycle: a sessile mother cell buds; the bud develops into a swarmer that is motile by means of a flagellum (often ensheathed); after maturation, the swarmer loses its flagellum and becomes a sessile, budding mother cell. All cultivated species are aerobes or facultative anaerobes. Occur worldwide in both eutrophic and oligotrophic freshwaters, as well as in estuarine and marine habitats. Sometimes become encrusted with iron and manganese oxides. Often associated in nature with algae and cyanobacteria. Although several species have now been isolated in pure culture, the type species and various other rosette-forming species have not been cultivated axenically. Carbohydrates are reported to be the main carbon source for cultivated members of the genus, which are relatively slow-growing.DNA G+C content (mol%): 50.5–57.7.Type species: Planctomyces bekefii |