Characterization of nitrogen-fixing (C2H2-reducing) Bacillus species from Egyptian soils

The characteristics of ten N2(C2H2)-fixing Bacillus strains, isolated from Egyptian soils, were investigated. The isolates were not completely identical to any of the described species in the 8th Edition of BERGEY's Manual. However, two strains were closely related to B. cereus, five strains were tentatively characterized as B. licheniformis and three strains with swollen sporangia and thick-walled endospores shared their main characteristics with B. circulans. A comparison between these bacilli and other known nitrogen-fixing Bacillus species revealed major differences in culture characteristics and C2H2-reducing activities. This suggests that the Bacillus isolates described here are new nitrogen-fixing bacteria.