The term bacillus comes from the Latin word bacillum, which can be translated as “rod”. The concept is used in the field of biology to name a bacterium that has this shape.
Bacilli, thus, are long-bodied bacteria that can be found in different environments. Many bacilli are pathogenic for humans, although not all have a negative impact.
Bacilli are usually classified according to their reaction to the Gram stain. When the violet crystal is fixed on the cell wall (as the chemical compound that acts as a dye is known), it is called a Gram positive bacillus. On the other hand, when this fixation does not occur, the bacterium is a Gram negative rod.
Many bacilli are known by the name of their discoverer. The Koch bacillus, for example, discovered by Robert Koch in the 19th century, is the bacterium Mycobacterium tuberculosis, which causes tuberculosis, a disease that begins by affecting the lungs and can then spread to the rest of the body until causing death.
The genus Mycobacterium, to which this bacillus belongs, has approximately thirty species, of which six are disease-causing. It is the type genus of Mycobacteriaceae, the family found in the suborder Corynebacteinae, belonging to the order Actinomycetales.
Koch’s bacillus is characterized by growing at a much slower rate than other bacteria; more precisely, its division can take up to sixteen hours. On the plate, it is sometimes necessary to wait two weeks to begin to see the colonies. Since its discovery is quite old, its genome has been completely sequenced, and for this reason it is possible to differentiate the four species that make up the complex.
Our immune system has many targets that can be attacked in the wall of the bacteria. In recent years, scientists have found species that resist the effect of normal antibiotics, such as ampicillin and rifampin. According to the number of antibiotics that are capable of resisting, they can be classified as multi-resistant or ultra-resistant strains. Some studies indicate that this capacity may be due to certain mutations in intergenic areas of the genome.
Another aspect that makes Koch’s bacilli particularly strong is their resistance to low temperatures, although this is contrasted with their sensitivity to heat and their vulnerability to pasteurization. This bacillus needs oxygen to grow properly. When faced with adverse conditions, it can encapsulate itself to deal with threats.
The bacillus of Hansen on the other hand, is the bacterium Mycobacterium leprae, which causes leprosy. This disease generates spots and nodules that destroy the tissues and cartilage and can cause mutilations. Another well-known bacillus is the Aertrycke bacillus, the origin of salmonella.
It is important to note that there are beneficial bacilli for humans. The Lactobacillus casei, which lives in the mouth and in the intestines of people, is a bacterium that is used to produce yogurt and helps to improve the digestive process.
The dairy industry takes advantage of the properties of this lactic acid-producing bacillus to make probiotic foods, that is, those that have live microorganisms in their composition, thanks to which the health of those who consume them can be highly benefited.
Various studies have shown that Lactobacillus casei is particularly resistant to a wide range of temperature and pH. These aspects are very important in its effectiveness, since it must pass through the gastric, duodenal and bile juices without being affected on the way to the intestine, where it is expected to arrive intact.