Validity of the Genus Alcaligenes

Abstract

Data are given indicating that the type species, A. faecalis, of the genus Alcaligenes is definitely known and if it cannot be recognized the genus cannot be retained. Probably, however, it applies to a species of intestinal origin unable to grow in the absence of organic N, which is very different from the soil and milk bacteria which have sometimes been recognized as species of the genus Alcaligenes. The author accordingly proposes the new genus, AGROBACTERIUM, with A. tumefaciens (the crown gall organism) as its type species to include Gram- negative rod-shaped bacteria, which do not produce acid or gas in ordinary bacteriological culture media but are able to make use of inorganic sources of N. The author definitely assigns to this new genus 2 closely related species: Agrobacterium radiobacter (previously placed in the genera, Bacterium, Achromobacter, and Alcaligenes, respectively) and Agrobacterium rhizogenes (the cause of hairy root disease, previously placed in Phytomonas); but suggests that other plant pathogens, soil bacteria, and possibly milk forms may belong in it.