title: L-(+)-lactate dehydrogenase deficiency is lethal in Streptococcus mutans.
abstract: 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.
authors.affiliation: Department of Oral Biology, University of Florida College of Dentistry, Gainesville 32610.
authors.forename: A
authors.initials: A
authors.lastname: Chen
authors.forename: J D
authors.initials: JD
authors.lastname: Hillman
authors.forename: M
authors.initials: M
authors.lastname: Duncan
mesh_terms: 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
chemical_list: D004269:DNA, Bacterial; D006898:Hydroxylamines; D019811:Hydroxylamine; D007770:L-Lactate Dehydrogenase