Pedomicrobium

Abstract

Pe.do.mi.cro' bi.um . Gr. n. pedon soil; Gr. adj. micros small; Gr. masc. n. bios life; M.L. neut. n. Pedomicrobium soil microbe. Proteobacteria / Alphaproteobacteria / Rhizobiales / Hyphomicrobiaceae / Pedomicrobium Cells oval , spherical , or rod‐shaped , 0.4–2.0 × 0.4–2.5 µm. Up to 5 hyphae (i.e., cellular outgrowths or prosthecae of constant diameter with reproductive function) are formed per cell body. Hyphae are 0.15–0.2 µm in diameter. At least one hypha originates laterally ; others may appear at the cell poles. Multiplication is by budding at the hyphal tips , with the long axis of the bud arranged perpendicular to the hyphal axis (Figures 1 and 2). Mature buds either separate from the hyphae as uniflagellated swarmers or remain attached. Extracellular polymers can be stained with ruthenium red and sometimes are visible in India ink mounts as thick capsules around mother cells. Oxidized iron or manganese compounds are deposited on mother cells and later on hyphae . Resting stages are not known. Gram negative , older cells variable. Swarmer cells are motile by a single subpolar or polar flagellum (Figure 3). Other stages of the cell cycle (Figure 4) are nonmotile. Colonies are yellowish or reddish brown to dark brown, due to accumulated iron or manganese oxides. Aerobic. Catalase positive (test is in absence of MnO 2 and at neutral pH). Chemoorganotrophic . Acetate is utilized as a carbon source; most strains also grow on caproate or pyruvate. Protein digests, such as yeast extract, peptone, Casamino acids, and soytone, serve as carbon and/or nitrogen sources. Organic nitrogen sources utilized by most strains are glutamate, aspartate, glycine, serine, threonine, and valine. Inorganic nitrogen compounds allow only poor growth of some isolates; nitrate is reduced by most strains. Slow and poor growth occurs on agar media with 0 . 1–1 % fulvic acid iron sesquioxide complexes as sole carbon and nitrogen sources . Vitamin mixtures stimulate growth; lack of vitamins results in pleomorphic cells, which produce large granules of poly‐β‐hydroxybutyric acid. Growth is inhibited by polymyxin B and neomycin. The mol % G + C of the DNA is : 63–66.8. Type species : Pedomicrobium ferrugineum Aristovskaya 1961, 957, emend. Gebers and Beese 1988, 308.