Abstract
An L-lactate producing strain whose optimal temperature for growth and L-lactate production was 37°C, previously labeled as Streptococcus species IO-1, was characterized biochemically and genetically and identified as a variant strain of Lactococcus lactis. This strain tolerated 6.5% NaCl and grew on bile esculin agar. Thus the strain resembled enterococci biochemically. However, there was no Lancefield's group D antigen in the strain, but group N antigen was present. Quantitative DNA-DNA hybridization experiments showed that the strain did not resemble enterococci and should be assigned to the genus Lactococcus. Strain IO-1 was identified as a strain of Lactococcus lactic because the homology values between it and the type strain of the L. lactis, NCFB 604T were in a range of 62-77%. The growth of L. lactis is usually suppressed and very slow at 42°C but strain IO-1 grew confluently and very quickly at that temperature. It was also different from the type strain of L. lactis in that it produced antibiotics, which were not nisin but were similar to nisin to which other lactococci and some species of genus Bacillus and Clostridium were sensitive. This strain has been deposited in the Japan Collection of Microorganisms as L. lactis IO-1 JCM 7638.
