Spirillum bacteria include gram-negative bacteria that come in several species, which are Spirillum volutans and Spirillum winogradskyi. These spirillum have spiral-shaped bodies and distinct bacterial cell shapes. Besides coccus and bacillus cells, spirillum bacteria are the only other bacteria in the world to have distinct physical shapes throughout their lives.
According to Britannica, the genus Spirillum includes a suite of spiral-shaped bacteria that live almost exclusively in watery environments. The only exception is the species S. minus, which lives and breeds on land, and causes a rat-bite fever in humans. Although classified under one name, the title S. minus applies to several different species with corkscrew-shaped torsos. S. volutans is the largest of the spirillum species, and resides in the blood of living organisms, including mice, rats, gerbils and other small rodents. This bacteria can be transmitted easily to other living creatures, including primates and humans. Aquaspirillum and oceanospirillum are other types of bacteria in the spirillum family; these organisms inhabit primarily aquatic environments. Oceanospirillum live in salty bodies of water such as oceans and marshes, and prefer locations with oxygen levels lower than those found in the atmosphere. Spirillum are distinguished from other bacteria by their rigid cell walls and flagella, which act as tails to propel them through water.