K J Littel | PubMed Health

PubMed1983

Fluorogenic selective and differential medium for isolation of fecal streptococci.

Of 44 fluorogenic substrates tested for their ability to differentiate species of fecal streptococci, four yielded species-differentiating reactions. The remaining substrates either yielded uniformly positive, negative, or variable strain-dependent reactions. One substrate, 4-methylumbelliferone-alpha-D-galactoside, was hydrolyzed by Streptococcus bovis and S. faecium and its biotypes. 4-Methylumbelliferone-alpha-D-galactoside and a colorimetric starch substrate were incorporated into the fecal streptococcal selective medium of Donnelly and Hartman (Appl. Environ. Microbiol. 35:576-581, 1978). Three phenotypic groups were identifiable on the new fluorescent gentamicin-thallous-carbonate agar: (i) starch hydrolysis and fluorescence (S. bovis), (ii) no starch hydrolysis but fluorescence (S. faecium and its biotypes), and (iii) no starch hydrolysis or fluorescence (S. faecalis, S. avium, S. equinus, S. mitis, and S. salivarius). Of the presumptive identifications from sewage, swine, and bovine samples, 86% were confirmed as being correct. The new medium has potential application in water, food, environmental, and possibly clinical microbiology.

Animals↗

PubMed1982

Genetic and biochemical analyses of pantothenate biosynthesis in Escherichia coli and Salmonella typhimurium.

Pantothenate (pan) auxotrophs of Escherichia coli K-12 and Salmonella typhimurium LT2 were characterized by enzymatic and genetic analyses. The panB mutants of both organisms and the pan-6 ("panA") mutant of S. typhimurium are deficient in ketopantoate hydroxymethyltransferase, whereas the panC mutants lack pantothenate synthetase. panD mutants of E. coli K-12 were previously shown to be deficient in aspartate 1-decarboxylase. All mutants showed only a single enzyme defect. The finding that the pan-6 mutant was deficient in ketopantoate hydroxymethyltransferase indicates that the genetic lesion is a panB allele. The pan-6 mutant therefore is deficient in the utilization of alpha-ketoisovalerate rather than the synthesis of alpha-ketoisovalerate, as originally proposed. The order of the pan genes of E. coli K-12 was determined by phage P1-mediated three-factor crosses. The clockwise order was found to be aceF panB panD panC tonA on the genetic map of E. coli K-12. The three-factor crosses were greatly facilitated by use of a closely linked Tn10 transposon as the outside marker. We also found that supplementation of E. coli K-12 auxotrophs with a high concentration of pantothenate or beta-alanine increased the intracellular coenzyme A level two- to threefold above the normal level. Supplementation with pantoate or ketopantoate resulted in smaller increases.

Carboxy-Lyases↗