A bacillus is an elongated bacteria.
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 bacteria that has this shape.
Bacilli, in this way, are bacteria with an elongated body that can be found in different environments. Many bacilli are pathogenic for people, although not all of them have a negative impact.
It is common for bacilli to be classified according to their reaction to Gram stain . When crystal violet (as the chemical compound that acts as a dye is known) is fixed to the cell wall, it is called a Gram positive bacillus . On the other hand, when this fixation does not occur, the bacteria is a Gram-negative bacillus .
Koch's bacillus
Many bacilli are known by the name of their discoverer. Koch's bacillus , for example, discovered by Robert Koch in the 19th century, is the bacteria Mycobacterium tuberculosis , which causes tuberculosis , a disease that begins by affecting the lungs and can then spread to the rest of the body until it causes death.
The genus Mycobacterium , to which said bacillus belongs, has approximately thirty species , of which six cause diseases. This 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 speed than other bacteria; more precisely, its division can take up to sixteen hours. On plates, 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.
Many bacilli can cause diseases.
The action of antibiotics
Our immune system has many targets that can be attacked on the wall of the bacteria. In recent years, scientists have found species that resist the effect of standard antibiotics, such as ampicillin and rifampicin. According to the number of antibiotics they 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 bacilli especially 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 conditions that are adverse to it, it can encapsulate itself to deal with threats.
Harmful and beneficial bacilli
Hansen's bacillus , on the other hand, is the bacteria Mycobacterium leprae , which causes leprosy . This disease generates spots and nodules that destroy tissues and cartilage and can cause mutilations. Another well-known bacillus is Aertrycke's , the origin of salmonella .
It is important to highlight that there are beneficial bacilli for humans . Lactobacillus casei , which lives in the mouth and intestine of people, is a bacteria that is used to produce yogurt and that helps improve the digestive process.
The dairy industry takes advantage of the properties of this lactic acid-producing bacillus to produce probiotic foods, that is, those that have live microorganisms in their composition, thanks to which the health of those who consume them can be greatly benefited.
Various studies have shown that Lactobacillus casei is a species 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 .