Effect of temperature, humidity and exposure to oxygen on the survival of anaerobic bacteria.

The relative effect of humidity, temperature and exposure to oxygen on the survival of 11 strains of Bacteriodes spp., Fusobacterium necrophorum, Eubacterium lentum, Clostridium ramosum, Peptococcus asaccharolyticus and Peptostreptococcus anaerobius was evaluated. Suspensions of the test strains were applied to membrane filters either in empty sterile petri dishes or on plates of non-nutrient agar to provide dry or moist conditions. The filters were stored aerobically or anaerobically in an atmosphere containing 10% CO2 at either 4 degrees C or 35 degrees C. After holding periods of 0.375-384 h, the filters were transferred to nutrient plates inside an anaerobic glove box. After incubation the growth on the filters was compared with that on control filters that had not been stored. Survival was better at 4 degrees C than at 35 degrees C. For the gram-negative organisms, survival was better under moist than under dry conditions, whereas for gram-positive organisms this finding was sometimes reversed. The results indicate that, generally, anaerobic bacteria kept under aerobic conditions survive best under moist conditions at 4 degrees C.