Bacillus species - Overview

Unidentified species of Bacillus grown on Blood agar. (Microrao unknown date, Wikimedia commons)

Overview

Bacillus species are mostly non-pathogenic, environmental organisms.

Characteristics

The bacteria are large, motile, Gram positive rods that produce endospores. They are aerobes or facultative anaerobes and are catalase positive and oxidase negative. They grow on non-enriched media. Bacillus anthracis colonies are up to 5mm diameter, flat, dry and grey with a ground-glass appearance. Curled outgrowths from the edge of the colony give a 'medusa head' appearance. They are non-haemolytic and can be differentiated from Bacillus cereus. Bacillus licheniformis forms dull, rough, wrinkled colonies, with hair-like outgrowths. Bacillus species can often tolerate adverse environmental conditions.