Cultural Requirements for the Production of Black Pigments by Bacilli.

Spore-bearing aerobic bacteria' capable of producing striking black pigments have been known since the early reports of Gorini (1896) on "Bacillus lactis-niger" and of Biel (1896) and Lunt (1896) on "Bacillus mesentericus-niger." Although these types have become established in the bacteriological literature under the respective binomial designations of Bacillus niger (Migula, 1900) and Bacillus aterrimus (Lehmann and Neumann, 1896), there has been little agreement upon their characterization or upon the cultural conditions necessary for their pigmentation. Ford (1927) noted that B. aterrimus blackened potato very strikingly, in contrast to the brown color produced by B. niger. On the other hand, the differential key in Bergey's Manual (1934) employed the blackening of potato in the reverse order for separating the two species-B. aterrimu.s, white to pink; B. niger, black. Levine and Soppeland (1926) found both species capable of blackening potato, but only B. niger capable of fermenting lactose. This character was therefore used to separate the two species. Lehmann, Neumann and Breed (1931) considered the pigment-producing abilities of these organisms to be variable or inconstant, and grouped them together with forms closely related to Bacillus vulgatus.