Hydrolysis of N'-Benzoyl-Arginine-p-Nitroanilide Stereoisomers as a Phenotypic Test: a Study of Gram-Positive Halotolerant Bacteria

We tested a variety of halotolerant Gram-positive coccoid bacteria and other halotolerant bacteria for hydrolytic activity towards the L- and the D-isomer of N'-benzoyl-arginine-p-nitroanilide (BAPA). D-BAPA cleaving activity was earlier shown to be associated with endospore-forming bacteria and related organisms. Four groups were distinguished on the basis of their behavior towards the BAPA isomers: 1. D-BAPA cleaving bacteria: several Bacillus strains, two Planococcus species, and Marinococcus hispanicus. 2. Strain M96/12b, an endospore-forming bacterium, that cleaves both isomers. 3. L-BAPA cleaving bacteria: Gram-negative halotolerant bacteria (Halomonas elongata, Vibrio costicola), the Gram-positive coccoid bacterium Micrococcus luteus, and Bacillus pasteurii. 4. A number of Gram-positive cocci that cleave neither L-BAPA nor D-BAPA. Also a few ectoine-producing Bacillus species (B. halophilus, B. pantothenticus) fall in this category. We recommended to include the tests for L-BAPA and D-BAPA hydrolysis in phenotypic tests and numerical taxonomy studies of Gram-positive bacteria.