MEASUREMENT OF THE REDUCING ACTIVITY OF HETERO AND HOMOFERMENTATIVE LACTOBACILLI

¹ Department of Dental Research, Army Medical Service Graduate School, Walter Reed Army Medical Center, Washington, D. C.

A study has been made of the reduction of 2, 3, 5-triphenyltetrazolium (TTC) by washed cells of 15 strains and species of the genus Lactobacillus, representing both homo- and heterofermentative types. Maximal reduction occurred with 0.1 per cent TTC added to equal volumes of an 18-hour culture and M/50 glucose in 0.2 M buffer (pH 6.0) and incubated at 45° C. The minimum cell concentration, based on nitrogen content, which would effectively reduce TTC was less for heterofermentative strains than it was for homofermentative strains. The reduction of TTC is suggested as a means of differentiating homo- and heterofermentative strains of lactobacilli.