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PirellulaRANK: GenusTAXONOMY: Bacteria -> PVC group -> Planctomycetes -> Planctomycetia -> Planctomycetales -> Planctomycetaceae -> Pirellula OVERVIEW: Pear or teardrop-shaped cells with one pointed attachment pole, 0.5–3.0 × 1.0–5.0 µm. Gram-stain-negative. Cells do not possess a stalk, but may form a fibrillar holdfast. Frequently form rosettes by attachment with the pointed cell pole. The holdfast occurs on one pole of the cell (the narrow pole of ovoid cells) and facilitates attachment to other cells to form rosettes. Crateriform structures are distributed at one pole only. Reproduction is solely by bud formation. Buds are formed at or near the opposite, wider pole which thus constitutes the reproductive pole. Newly formed buds are motile by polar to subpolar monotrichous flagella. When thin sectioned cells prepared via cryosubstitution are examined via electron microscopy, they display a characteristic organization including a major cell compartment, the pirellulosome, in which ribosomes and a condensed nucleoid are enclosed by an intracytoplasmic membrane, and a ribosome-free paryphoplasm region between this intracytoplasmic membrane and the closely apposed cytoplasmic membrane and cell wall. Chemoorganotrophic; obligately aerobic. The original description was emended following the description of Rhodopirellula and Blastopirellula to include more recent data (Schlesner et al., 2004). The major polyamine is symhomospermidine. The major respiratory lipoquinone present is MK-6. The major phospholipid present is phosphatidylglycerol. A number of other lipids are present that have characteristic Rf values, but whose structures are not currently known. The lipid pattern is characteristic. The major fatty acids present are C14:0, C16:1 ω7, C16:0, C18:1 ω9, C18:1 ω7, C18:0, and C20:1 ω11.DNA G+C content (mol%): 56.4 ± 0.4 to 59.0 (Tm, Bd).Type species: Pirellula staleyi |