NITRATE-REDUCING BACTERIA ON RAT TONGUES

Nitrite-producing bacteria (NPB) were isolated from tongues of laborat ory rats, The most commonly found nitrite-producing organism was Staph ylococcus sciuri, followed by Staphylococcus intermedius, Pasteurella spp., and finally Streptococcus spp, Both morphometric quantification of bacteria on tongue sections and enumeration of culturable bacteria (CFU) showed an increase in the density of bacteria towards the poster ior tongue. Up to 65% of bacteria were located in the deep clefts on t he posterior tongue, The proportion of culturable NPB in the total cul turable microbial population increased from 6% (10(5) CFU cm(-2)) on t he anterior tongue to 65% (10(7) CFU cm(-2)) on the posterior tongue, Different species compositions of NPB were found on different tongue s ections with S. intermedius populations decreasing and S. sciuri and P asteurella populations increasing towards the posterior tongue, Nitrit e production was sensitive to oxygen, and significant nitrite producti on was only detected on the posterior tongue where the majority of bac teria are situated in deep clefts in the tongue surface, This study su ggests the importance of bacteria in nitrite production, from nitrate, on the tongue. Nitrite produced on the tongue may subsequently form n itric oxide in the acidic environment of the stomach, Because of the a ntimicrobial properties of nitric oxide, a key role for nitrate-reduci ng tongue bacteria in host animal defense against food-borne pathogens is proposed.