Largest pathogenic Bacillus organism is -
The anthrax bacillus is one of the largest of pathogenic bacteria measuring 3-10 x 1-16 um. It resembles a Bamboo stick appearance Ref: Ananthanarayan & paniker's Textbook of Microbiology 9th edition pg no 244
Bacillum subtilis
Bacillum cereus
Bacillum anthrocis
Bacillum megaterism
general microbiology