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PhenylobacteriumRANK: GenusTAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Alphaproteobacteria -> Caulobacterales -> Caulobacteraceae -> Phenylobacterium OVERVIEW: Rods, coccobacilli, or cocci; 0.7–1.0 × 1.0–2.0 μm occurring singly, in pairs, or in short chains. Some strains tend to clump. In old cultures, pleomorphic forms, such as long rods (1.0 × 2.0–4.0 µm), long chains (10–50 µm) connected by filaments, and elliptical forms, may occur. Capsule stain negative; flexible capsule present. Nonmotile. Nonsporeforming. Non-acid-fast. Sheaths and prosthecae not produced. Nonpigmented. Gram negative. Growth on chloridazon–mineral salts agar is slow and colonies are small (1–2 mm) after 2–3 weeks. Colonies may be either smooth, convex, moist with shiny surfaces and entire edges, and easily emulsified in saline, or rough, dry, and not emulsifiable in saline. In liquid media, there is slight production of a greenish-yellow nonfluorescent pigment; in media containing l-phenylalanine a yellowish-green fluorescent pigment is produced. Strictly aerobic. Catalase positive, weakly oxidase positive. Chemoorganotrophic, having a strictly respiratory type of metabolism. Optimal temperature, 28–30°C. No growth at 4°C or 37°C; at 37°C cultures die within several days. Optimal pH 6.8–7.0; growth occurs between pH 6.5 and 8; no growth at pH 4 or 9. Osmotically sensitive. Vitamin B12 is a growth factor. High nutritional specialization; grows well on chloridazon, antipyrin, and l-phenylalanine (most strains only after long lag phase). Slow growth on l-glutamate, pyruvate, fumarate, succinate, and malate as well as on diluted complex media (0.5–2 g/l peptone). Most sugars, alcohols, amino acids, carboxylic acids, and ordinary complex media are not utilized. Does not denitrify; does not produce nitrite from nitrate. NH4+ and NO3− are used as sole sources of nitrogen; no growth with N2. Gelatin, casein, starch, and esculin not hydrolyzed. Urease negative. Litmus milk negative. Weak H2S production from thiosulfate or cysteine. Methyl red and Voges–Proskauer negative. Indole negative. No acid or gas produced from sugars or alcohols. Not pathogenic for rats or rabbits. Isolated from soil after enrichment in mineral salts media containing chloridazon, antipyrin, or pyramidon (synthetic heterocyclic compounds).The mol% G + C of the DNA is: 65–68.5. Type species: Phenylobacterium immobile This genus contains microbial species that can reside in the human gastrointestinal tract. [PMC 4262072]
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