bacillus firmus bacillus firmus bacillus firmus is a species of bacteria within the genus bacillus. some strains of this species are very alkaline-tolerant and may grow in environments with ph as high as 11. bacillus firmus scientific classification domain: bacteria phylum: bacillota class: bacilli order: bacillales family: bacillaceae genus: bacillus species: b. firmus binomial name bacillus firmusbredemann and werner 1933 this species has been recently transferred into the genus cytobacillus. the correct nomenclature is cytobacillus firmus.