[Taxonomic study of "Citrobacter freundii" biochemical variants (author's transl)]. / Position taxonomique de variants biochimiques de Citrobacter freundii.

Biochemical variants (ornithine-decarboxylase-positive and beta-galactosidase-negative) of Citrobacter freundii were characterized using numerical taxonomy, determination of deoxyribonucleic acid (DNA) base composition and DNA-DNA hybridization. Three clusters were detected by numerical taxonomy based on the assimilation of 146 carbohydrates. The atypical strains were dispersed into two clusters along with typical C. freundii strains. Furthermore, m-hydroxybenzoate metabolism, determination of base composition and DNA reassociation show that all three clusters are closely related. Therefore, the biochemical variants form a biogroup within C. freundii rather than a separate species.

[Study of Enterobacter strains belonging to a particular group related to Enterobacter aerogenes (author's transl)]. / Etude de souches de Enterobacter appartenant à un groupe particulier proche de E. aerogenes

Thirty strains of Enterobacteriaceae constitute a new group related to E. aerogenes with the following differential biochemical characters: urease+, KCN-, sorbitol-, mucate- and gelatinase-. Ten of these strains with antigenic similarities and polyresistance to antibiotics were isolated from urine in the same hospital.

Polynucleotide sequence divergence among strains of Salmonella sub-genus IV and closely related organisms.

Polynucleotide sequence relatedness studies were carried out to determine the extent of divergence present in Salmonella sub-genus IV strains, related strains of Salmonella of other sub-genera and the Citrobacter genus. Salmonella sub-genus IV were 91-97% related. The Salmonella of sub-genus I, II and III showed lower binding (79-87%) to Salmonella sub-genus IV. The change in thermal elution midpoint closely followed the reassociation data. Relatedness of Salmonella sub-genus IV and C. freundii ranged between 44 and 57%, which confirms that these organisms belong to different genera. The taxonomic position of Salmonella sub-genus IV is discussed according to the actual classification of the family Enterobacteriaceae.

Physical studies of a plasmid mediating tetracycline resistance and hydrogen sulfide production in Escherichia coli.

Tetracycline resistance and hydrogen sulfide production have been previously found to be plasmid-mediated in a naturally-occurring strain of Escherichia coli; both functions are specified by a single conjugative plasmid called pIP231(Te-H2S); pIP231DNA was isolated as covalently closed molecules in dye-buoyant density gradients. The base ratio of the DNA was found to be 50% GC by density gradient analysis. Electron micrographs of plasmid molecules showed a contour length of 20 +/- 2 mum (40 +/- 4 X 10(6) daltons). Between one and two copies of pIP231 molecules per host chromosome were found in E. coli K12.