Types of Bacillus Bacteria
The term bacillus may be used interchangeably to describe both a specific genus of bacteria (denoted as Bacillus with capital B) and also in the general sense to describe the shape of many different strains of bacteria. This issue can cause confusion as there are many strains of bacteria of the genus Bacillus that are not of the same shape.
In the general sense, bacillus refers to any strain of bacteria that are rod-shaped. They are found in many different taxonomic groups and contain Gram-negative as well as Gram-positive strains.
Diplobacillus refers to two rod-shaped bacteria connected on one end. This arrangement normally occurs after one bacterium divides and fails to completely separate from the newly formed bacterium.
Streptobacillus describes a chain of rod-shaped bacteria joined together from end to end. This again results from the bacterial cells failing to completely separate after dividing as seen with the diplobacillus bacteria.
Coccobacillus strains are shortened rods and described as intermediates between spherical coccus bacteria and the aforementioned rod-shaped bacillus. However, despite their resemblance to coccus strains, they are considered bacillus-shaped bacteria.