All organisms in this group are straight or slightly curved chemoorganotrophic and aerobic rods with polar flagella.
General characteristics:
Straight or curved rods but no vibrioid; size 0.5-1.0µm by 1.5-4.0µm; no spores; gram-negative; polar flagella: single or multiple; no sheaths, appendages, or buds; respiratory metabolism, never fermentative, although may produce small amounts of acid from glucose aerobically; use low-molecular-weight organic compounds, not polymers; some are chemolithotrophic, using H
2 or CO as sole electron donor; some can use nitrate as electron acceptor anaerobically; some can use arginine as enery source anaerobically
Minimal characteristics for identification:
Gram-negative, straight or slightly curved; no spores; motile (always); polar flagella (flagellar stain); oxidative-fermentative medium with glucose: tube open, acid produced; tube sealed, acid not produced; gas not produced from glucose; oxidase, almost always positive; catalase always positive; photosynthetic pigments absent (distinguishes them from
purple nonsulfur bacteria); indole-negative; methyl red-negative; Voges-Proskauer-negative
Taken from the text Brock Biology of Microorganisms (10th ed.). Madigan, M.T., Martinko, J.M., and Parker, J. 2003. Prentice Hall. 368,370p.