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OscillatoriaRANK: GenusTAXONOMY: Bacteria -> Terrabacteria group -> Cyanobacteria/Melainabacteria group -> Cyanobacteria -> Oscillatoriophycideae -> Oscillatoriales -> Oscillatoria OVERVIEW: Filamentous organisms that divide exclusively by binary fission and in one plane. The cylindrical trichomes are straight (except for the terminal region in some cases); flexible or semirigid; over ∼4 µm in diameter; disc-like cells wider than long. The trichome diameter of cultured representatives is 4–16 µm, but species with trichomes up to >100 µm in diameter have been described in the botanical literature. Invariably, in larger trichomes (>10 µm in diameter) the cells are much shorter than broad. Cross-walls are generally visible by light microscopy (Figures 1 and 2). Constrictions at cross-walls are lacking or slight, but the total indentation never exceeds 1/8 of the trichome diameter. Generally, the cross-wall is thinner than the longitudinal wall. The initiation of cross-wall synthesis by centripetal growth precedes the completion of previously initiated cross-walls (Figure 3). During fission, the cytoplasmic membrane invaginates, with a thinner peptidoglycan layer following and separating the new membranes of the daughter cells. This characteristic also applies to the genera Spirulina, Arthrospira, and Lyngbya. Reproduction of trichomes is by transcellular breakage involving sacrificial cell death (i.e., “necridial” cells). |