Bacilli are a large homogeneous group of bacteria that survive in a wide range of environmental conditions. Formation of resistant spores allows them to survive in high temperature zones where other organisms cannot. Eighty samples were collected and inoculated directly into nutrient broth. Of the eighty samples collected, thirty three exhibited growth. Nine of these were Gram positive rods, twenty were Gram negative rods, and four were Gram positive cocci. Only cultures that yielded Gram positive rods were processed further. Antimicrobial profiling was performed using standard organisms: Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, E. coli 35218 and Pseudomonas aeruginosa ATCC 27853. No inhibition was noted against S. aureus ATCC 29213 and E. coli 35218. Five of the nine Gram positive isolates revealed inhibitory properties against the standard organisms. Phylogenetic analysis of amplified 16S rDNA gene confirmed that all the six antagonistic isolates formed close phylogenetic clusters with known members of Bacillus species with a 88-99% sequence identity. The current study shows the presence of thermophilic Bacillus species, which are potential biomolecule producers within the hot springs of Lake Bogoria, Kenya. However, further investigation will be useful for the discovery of novel bioactive substances effective against wide range of pathogens. Key words: Bacillus, Lake Bogoria, secondary metabolites, antibiotics.
