According to Bergey's Manual of Determinative Bacteriology, 7th edition, the genus Arthrobacter is divided into two groups, one of which utilizes citrate as a sole organic nutrient and the other does not utilize citrate. Among authentic strains of this genus, the growth of Arthrobacter pascens IFO 12139 and Arthrobacter simplex IFO 12069 was inhibited by citrate. It was found that A. pascens IFO 12139 required bivalent cation(s) for growth and failed to grow when the medium contained excess of citrate against bivalent cations. On the other hand, A. simplex IFO 12069 could not utilize citrate as a sole source of carbon, and citrate inhibited glucose utilization of the organism. Among many strains belonging to the genera Corynebacterium, Brevibacterium, and Bacillus, growth was inhibited by citrate.