GENOME AND FATTY-ACID ANALYSIS OF PSEUDOMONAS-STUTZERI

A genome and fatty acid analysis of 16 Pseudomonas stutzeri reference strains having DNA compositions ranging from 62.2 to 65.5 mol% G+C was performed by pulsed-field gel electrophoresis of XbaI and SpeI macror estriction fragments and gas chromatography of total cellular fatty ac ids. Macrorestriction fragment patterns were evaluated by using previo usly described algorithms (D. Grothues and B. Tummler, Mol. Microbiol. 5:2763-2776, 1991), and the results allowed us to subdivide the speci es 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 macrores triction fragment patterns, and even phenotypically similar strains pr oduced divergent patterns. While the differences were not sufficiently great to exclude any strain from P. stutzeri, they suggest that recom bination and niche-specific selection may be significant factors respo nsible for generating and maintaining the heterogeneity inherent in th e species. Genome sizes were estimated from the sums of SpeI restricti on 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 digest ion with XbaI and SpeI showed that both distributions differed signifi cantly from the expected (random) distribution, suggesting that there is a supragenic level of chromosomal organization. An analysis of fatt y acid methyl ester data by using Microbial Identification System soft ware revealed a similar correlation between phenotype and G+C content, indicating that division of the species is possible by the method use d in this study. For comparative purposes, a numerical analysis of pre viously reported substrate utilization data (N. J. Palleroni, M. Doudo roff, R. Y. Stanier, R. E. Solanes, 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 correlati on with the results obtained from either the macrorestriction fragment analysis or the fatty acid methyl ester analysis.