TAXONOMY: Bacteria -> Terrabacteria group -> Actinobacteria -> Actinobacteria -> Propionibacteriales -> Nocardioidaceae -> Nocardioides
Abundantly branched vegetative hyphae or irregular rods may be formed in young cultures. The morphogenetic cycle is usually observable, with different organisms showing more or less complex succession of morphological stages. The morphogenetic cycle usually starts with the coccoid cells or short rods which may simply germinate into rods or longer filaments, show elementary branching or form extensively branched hyphae on and below the surface of agar media, and may give rise to aerial mycelium. The latter consists of irregular, sparsely branching or unbranched hyphae and may totally or partially cover the primary mycelium, or be discernible only microscopically. Both the vegetative and aerial hyphae and the rod-shaped cells undergo various degrees of fragmentation (division via septa formation). Fragmentation finally results in the next generation of short rod-like and coccoid cells. No endospores are formed. Rod-shaped bacteria may be motile. Gram-stain-positive type of cell wall. Non-acid-fast. The colony color is mainly whitish, creamy, or yellow of different tint and intensity and rarely orange. Diffusible pigments are not usually produced. Colonies not covered by aerial mycelium are mostly pasty, with smooth to wrinkled surface. Chemo-organotrophic, with an oxidative type of metabolism. Predominantly catalase-positive. The level of oxidase activity varies among species. Grows under aerobic conditions on standard laboratory media, including chemically defined (synthetic) media or media with low nutrient concentrations. Certain vitamins or other growth factors may be required. Utilizes a wide range of carbon and nitrogen sources, including unusual organic compounds and toxic environmental pollutants. Mostly mesophilic and neutrophilic; some grow at initial pH values of 5–5.5 and/or 11–12. Mostly non-halophilic, but salt-requiring organisms occasionally occur.
DNA G+C content (mol%): 67.5 (Tm)–74.8 (HPLC).
Type species: Nocardioides albus