Dehydrogenase Patterns in the Taxonomy of Bacteroides

Abstract

The malate dehydrogenase (MDH) electrophoretic mobilities of 128 strains of Bacteroides belonging to 17 spp., including 3 ssp. of B. melaninogenicus and 2 ssp. of B. ruminicola, were examined. Among the pigmented bacteroides, the migration of this enzyme correlated well with recognized taxa and only 1 strain, VPI 9085 was clearly different. Other species such as B. oralis, B. buccalis, B. denticola, B. pentosaceus, B. bivius, B. disiens and B. ruminicola were delineated by the combined use of MDH and glutamate dehydrogenase. Strains (43) belonging to the ''B. fragilis group'' differed from the above species in possessing glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and reference strains and fresh isolates were assigned to the correct species by the mobility pattern of these 2 enzymes. Other properties of MDH such as the pH optima for the oxidation of malate or the reduction of oxaloacetate were of limited taxonomic value, but the alkaline stability of this enzyme at pH 9, 10 and 11 clearly differentiates the saccharolytic from the non-saccharolytic species of pigmented bacteroides with the latter showing highly stable enzymes with a half life greater than 50 min.