Genetic Evidence for Plasmid-Linked Lactose Metabolism in Streptococcus lactis subsp. diacetylactis.
It has been previously observed that loss of plasmid pGK4101 occurred concomitantly with loss of lactose-fermenting ability in Streptococcus lactis subsp. diacetylactis 18-16. Transfer of this 41-megadalton plasmid to LM0230, a lactosenegative (Lac) strain of S. lactis, required cell-to-cell contact and resulted in a conversion of LM0230 to the Lac phenotype. This confirms the linkage of lactose-fermenting ability to the 41-megadalton plasmid in S. lactis subsp. diacetylactis and, in addition, demonstrates transfer by a process resembling conjugation in the group N streptococci.
Kempler
G M
GM
Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108.
McKay
L L
LL