aerobic organism anaerobic organism anthrax bacillaceae bacillales bacilli bacillus anthracis bacillus cereus bacillus coagulans bacillus licheniformis bacillus megaterium bacillus sphaericus bacillus subtilis bacillus thuringiensis bacteria bacterial disease biofilm biological classification catalase coccobacillus coccus diplococcus endospore enzyme exotoxin facultative anaerobic organism firmicutes foodborne illness genus gut flora human flora insect lipophilic bacteria lysogenic cycle model organism paenibacillus pathogenic bacteria periplasmic space skin flora species staphylococcus test tube type species vaginal flora