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2. Characteristics of Spirillum minus

A Spirillum

This fastidious bacterium cannot be cultured in vitro . Because of this, Spirillum minus has not been fully characterized. The bacterium can be grown in vivo, by inoculating non-infected rats with material presumed to be infected. Animal innoculation is the method used to identify Spirillum minus infection in humans.

Spirillum minus is a gram negative bacteria. Gram negative bacteria have thinner cell walls than gram positive bacteria. Gram negative cell walls contain lipopolysaccharide (LPS) which acts as an endotoxin that may cause a strong immune response in the host when the cell is lysed.

The characteristics that support the classification of Spirillum minus as a spirillum are the cell's spiral shape and its rigid cell wall. There are two types of bacteria with spiral shapes, spirillum and spirochetes. The major difference between these two types is their rigidity. Spirillum are rigid while spirochetes are more flexible. 

Spirillum minus is very small. Each cell is about .2µm wide and 3-5µm in length. The cell has two to three waves, each wavelength measuring .8-1µm. It is possible that these “turns” maybe planar rather than helical.

This bacterium can be visualized by the use of dark-field or phase contrast microscopes. The use of stains can help in the identification of these organisms. While these organisms are gram negative, the gram stain works poorly on this bacterium. Giemsa, Wright, and silver staining work much better.

Spirillum minus has one to five flagella on each end and is very motile. The flagella of bacteria move in circular motion, unlike eukaryotic flagella which move in a back and forth motion.

Because Spirillum minus is a bacteria,  the only subcellular structures this organism has are its DNA and its ribosomes. The DNA is where the genetic information of the species is stored. Its bacterial DNA is circular, unlike Eukaryotic DNA which is linear. The ribosomes are the structure where proteins for the cell are produced. The ribosomes found in Prokaryotes (like bacteria)  are different from those in Eukaryotes (multicellular organisms) is their size. Prokaryotic ribosomes are much smaller than those of Eukaryotes.

This organism reproduces through binary fission. Binary fission is a method of asexual replication in which the DNA of the bacterium is doubled and attached to the cell membrane. The cell begins to increase in size until the original cell has been doubled. Then the membrane pinches off to produce two new cells.

Spirillum minus is most commonly found in Asia.  It is found within the mouth and nose of rodents, mainly rats. It is considered part of their natural flora. In certain areas up to 25% of rats carry this bacteria.

Spirillum minus is a facultative anaerobe which means that although it grows best in the presence of oxygen, it is able to live in conditions lacking oxygen. Spirillum minus uses oxygen as the final acceptor of electrons in the electron transport chain but is also able to perform fermentation when it lacks oxygen.