LIMITS AND POSSIBILITIES OF TOTAL FATTY-ACID ANALYSIS FOR CLASSIFICATION AND IDENTIFICATION OF BACILLUS SPECIES

A numerical study of fatty acid patterns of 313 Bacillus strains was d one based on standardized cultural and chemical techniques. All strain s were characterized by the predominance of branched fatty acids (main ly i15:0, a15:0, often i17:0, a17:0, rarely i13:0, i14:0, i16:0) rangi ng from 40% to more than 90% of total fatty acids. The ratios and prop ortions of the major fatty acids were found to be largely responsible for grouping strains into seven clusters (I to VII) by the UPGMA metho d using the correlation coefficient (S(C)). Two main groups of Bacillu s species can be defined on the basis of the ratio of the quantitative ly predominant fatty acids i15:0 and a15:0. The species B. amyloliquef aciens, B. firmus, B. firmus-lentus intermediates, B. lentus, 'B. freu denreichii', B. laterosporus, B. licheniformis, B. megaterium, B. past eurii, B. subtilis, B. alvei, B. circulans, B. coagulans, B. globispor us, B. lautus, B. macerans, B. pabuli, B. pantothenticus, B. polymyxa, B. psychrophilus and some strains of B. sphaericus (grouped into clus ters I, II, and VII) are characterized by a ratio of i15:0/a15:0 < 2. The species B. thermoglucosidasius, B. badius, B. pumilus, the majorit y of B. sphaericus strains, B. stearothermophilus, B. cereus and B. th uringiensis grouped into clusters III to VI and exhibited a ratio of i 15:0/a15:0 > 2. Significant quantitative variations were observed for particular fatty acids in different strains belonging to the species B . firmus, B. firmus-lentus intermediates, B. macquariensis, B. megater ium, B. subtilis, B. circulans, B. coagulans, B. macerans, and B. cere us. The species could be clustered into subgroups at a similarity leve l of 97.5% (S(C)). With fatty acid analysis, Bacillus strains can be a ssigned to species groups, however, the enormous heterogeneity of fatt y acid profiles within several species reflects the unsatisfactory tax onomic situation within the genus, which can be improved by further DN A-DNA hybridization studies.