L-(+)-lactate dehydrogenase deficiency is lethal in Streptococcus mutans.
The previously cloned gene for L-(+)-lactate dehydrogenase (LDH) from Streptococcus mutans was mutagenized in vitro. An Escherichia coli transformant which expressed a thermolabile LDH activity was identified. The ldh(Ts) gene was introduced into S. mutans on a suicide vector to create a heterodiploid expressing both wild-type and thermolabile LDH activities. Self-recombinants which had only one ldh gene were isolated. One of these clones expressed only the thermolabile LDH activity. This isolate grew well at 30 degrees C but did not grow at 42 degrees C under a variety of cultivation conditions, thereby proving that LDH deficiency is lethal in S. mutans in the absence of compensatory mutations.
Chen
A
A
Department of Oral Biology, University of Florida College of Dentistry, Gainesville 32610.
Hillman
J D
JD
Duncan
M
M
D015139:Blotting, Southern; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D004795:Enzyme Stability; D005798:Genes, Bacterial; D006358:Hot Temperature; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D010957:Plasmids / Q000187:drug effects; D011995:Recombination, Genetic; D015183:Restriction Mapping; D013295:Streptococcus mutans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013816:Thermodynamics
D004269:DNA, Bacterial; D006898:Hydroxylamines; D019811:Hydroxylamine; D007770:L-Lactate Dehydrogenase