Characterization of lac+ transductants of Streptococcus lactis.
A phage-mediated transducing system was used in studying certain physiological characteristics of S. lactis C2 wild type, lactose-negative mutants, and lactose-positive transductants. Lac(-) mutants, obtained by acriflavine treatment of the wild type, were similar to the wild type in all characteristics tested except they lacked beta-D-phosphogalactoside galactohydrolase (beta-Pgal) and could not transport [(14)C]lactose; they also had approximately 10% of the proteolytic ability than wild-type cells. The lactose-fermenting characteristic was transduced from the wild type to Lac(-) mutants. The Lac(+) transductants obtained were similar to the wild-type parent with respect to lactose fermentation and level of beta-Pgal activity (0.186 U of protein per mg). These transductants, however, had not regained full proteolytic ability and were similar to the Lac(-) mutant in this respect. Lactic acid production of the transductants in milk was approximately two-thirds that of the wild type. Data suggest that both the lactose-fermenting and proteolytic characters are carried on extrachromasomal particles (plasmids).
D000167:Acriflavine; D000818:Animals; D002250:Carbon Radioisotopes; D003470:Culture Media; D005285:Fermentation; D005690:Galactose / Q000378:metabolism; D005696:Galactosidases / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism; D007773:Lactates / Q000096:biosynthesis; D013294:Lactococcus lactis / Q000201:enzymology / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism*; D008242:Lysogeny; D008358:Mannose / Q000378:metabolism; D008892:Milk; D009153:Mutagens; D009154:Mutation; D014161:Transduction, Genetic
D002250:Carbon Radioisotopes; D003470:Culture Media; D007773:Lactates; D009153:Mutagens; D000167:Acriflavine; D005696:Galactosidases; D005947:Glucose; D007785:Lactose; D008358:Mannose; D005690:Galactose