A genome and fatty acid analysis of 16 reference strains having DNA compositions ranging from 62.2 to 65.5 mol% G+C was performed by pulsed-field gel electrophoresis of I and I macrorestriction fragments and gas chromatography of total cellular fatty acids. Macrorestriction fragment patterns were evaluated by using previously described algorithms (D. Grothues and B. Tümmler, Mol. Microbiol. 5:2763-2776, 1991), and the results allowed us to subdivide the species into two groups which correlated with G+C content. Two examples of recent strain divergence were observed among clinical isolates, but in general a marked degree of heterogeneity was observed in the macrorestriction fragment patterns, and even phenotypically similar strains produced divergent patterns. While the differences were not sufficiently great to exclude any strain from , they suggest that recombination and niche-specific selection may be significant factors responsible for generating and maintaining the heterogeneity inherent in the species. Genome sizes were estimated from the sums of I restriction fragment sizes and ranged from 3.4 to 4.3 Mbp; the genome sizes of the low-G+C-content strains (G+C contents, approximately 62 mol%) were confined to a narrow range between 3.9 and 4.1 Mbp. An examination of the distributions of macrorestriction fragments resulting from digestion with I and I showed that both distributions differed significantly from the expected (random) distribution, suggesting that there is a supragenic level of chromosomal organization. An analysis of fatty acid methyl ester data by using Microbial Identification System software revealed a similar correlation between phenotype and G+C content, indicating that division of the species is possible by the method used in this study. For comparative purposes, a numerical analysis of previously reported substrate utilization data (N. J. Palleroni, M. Doudoroff, R. Y. Stanier, R. E. Solánes, and M. Mandel, J. Gen. Microbiol. 60:215-231, 1970) was performed. The results of this analysis revealed that there was a relationship among strains which showed no correlation with the results obtained from either the macrorestriction fragment analysis or the fatty acid methyl ester analysis.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error