Do species of Bacillus vary in their ability to cause hemolysis?
Answer Hello Julia, in fact, the ability for hemolysis is not widespread at all in the genus Bacillus. Most species are not hemolytic, i.e. don’t possess hemolysin genes (e.g. sph, hbl or plc). B. cereus, B. subtilis and B. megaterium are very closely related and belong to the B. cereus subgroup. However, of these three species only B. cereus is well-known for hemolytic strains (meaning that not all bacteria of this species are hemolytic, but only certain ‘clonal lineages’; perhaps 1/3 to 1/2 of the strains in culture collections are hemolytic). B. subtilis strains may show weak hemolysis (possibly a feature acquired by genetic transformation, i.e. uptake of plasmids containing hemolysin genes). The ability for hemolysis can be tested on petri dishes with sheep blood agar. No hemolytic strains of B. megaterium are known yet.
