Production of phenylacetic acid by Bacteroides melaninogenicus ssp. intermedius serogroup C-1.

The methyl derivatives of broth cultures of black-pigmented Bacteroides were examined by gas chromatography for production of phenylacetic acid. Two serogroups of B. melaninogenicus ssp. intermedius described by Lambe differed in the ability to produce phenylacetate. Serogroup C failed to produce phenylacetic acid while serogroup C-1 produced small amounts of phenylacetate, which contributed 2.2-5.7% to the total nonvolatile acid profile. Holdeman's newly proposed species "B. intermedius" and "B. corporis" correspond to serogroups C and C-1, respectively. These data support the elevation of the two serogroups of B. melaninogenicus ssp. intermedius to species status. Bacteroides gingivalis produced phenylacetate in significantly larger quantities than B. corporis. Bacteroides melaninogenicus ssp. melaninogenicus, "B. melaninogenicus ssp. levii," and B. asaccharolyticus did not produce phenylacetic acid. These results indicate that phenylacetic acid production may be useful in distinguishing "B. corporis" and B. gingivalis from the other black-pigmented Bacteroides.