[Numerical taxonomy of a thermophilic "Bacillus" species isolated from West African rice soils (author's transl)].

Fifty-seven strains of endospore-forming thermophilic bacteria, 37 of which were capable of denitrification, were isolated from rice soils of West Africa. They were compared with 17 strains of similar bacteria from culture collections, utilizing a total of 123 morphological, physiological and biochemical characteristics. A numerical analysis was performed using the complete linkage-clustering method and the Khi2 test. Seventy-five percent (55 strains) could be included in 12 groups at a taxonomic distance of 0.015. Wild strains of denitrifiers issued in phenons 8 to 12 and strains of phenon 4 (not denitrifying) were related to the named strains of phenons 1 and 7 (Bacillus stearothermophilus). Twenty-two wild strains, and 5 strains from culture collections, were only thermotolerating without growth at 65 degrees C. The strains of phenon 3 were related to the 3 named strains of B. coagulans. Phenons 5 and 6 were composed of strains related to B. circulans. The strains of phenon 2 denitrified and showed a swollen central endospore; they were closely related to B. brevis. The denitrifying thermophilic strains isolated from rice soils (phenons 8 to 12) were related to the first group (B. kaustophilus) of Walker and Wolf but their base compositions of DNA were significantly different from those found for the reference strains.