The bacteria Lactobacillius is notably present in the normal oral flora of the mouth. This is a gram-positive bacterium that is large rods, occurring singly or in pairs, and is anaerobic. Lactobacillius is rarely pathogenic and is widespread and found normally in the mouth and intestinal tracts of humans and other animals. In the oral cavity, Lactobacillius are associated with dental carries even though they are known not to be involved in the initiation of the decay. Lactobacillius are fermentative bacteria using sugar as a nutrient and producing lactic acid. The bacteria are resistant to acid conditions and grow well in pHs between 4 to 5 They can also survive at pHs as low as 3.2. since they can survive at these low pHs, this enables them to continue producing lactic acid where other bacteria can not.

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