A Taxonomical Study on the Oxygen Sensitivity of Oral Aciduric Bacteria

Abstract

Even though oral aciduric bacteria can grow in the aerobic atomosphere, it has known in counting number of this bacteria in an oral specimen that anaerobic condition significantly favor their growth. Depending on the strict anaerobiosis of Lactobacillus bifidus, the first. interest should be concentrated at the taxonomical identification of those aerobic and anaerobic strains. The oral specimen was seeded on a plate of the Onisi and Kondo's selective medium for the lactobacillus count and incubated aerobically at 37°C for two days. Colonies representing aerobic strains of the specimen were picked up for further tests based on differences of the colonial morphology and the rest was marked in order to differentiate from anaerobic strains which may grow for successive two days incubation of the same plate in phosphorous jar. The common bacteriological tests for metabolites, fermentation. of sugars and refraction of lactic acid were described on 24 aerobically isolated and 29 anae robically isolated strains for the identification.
Isolated 31 strains were identified to either L. acidcphilus, L. brevis, L. plantarum, L. f ermenti, L. delbrueckii, L. casei or L. buclaneri, but 22 strains were unidentifiable to the established species but to types proposed by Morris. The major species was L. plantarum. L. plantarum, L. acidophilus and some of the unidentifiable types grew aerobically and anaerobically as well. Five out of six L. casei were found aerobic media while four L. fermenti out of five came from anaerobic cultures. Anaerobic culture seemed likely in case of lactobacillus count, because only under this condition, L. fermenti may be countable and numerous additional colonies of the other species and types may also be obtainable on the plate.