Bacillus subtilis

The English name of Bacillus subtilis is Bacillus subtilis (for bacteria, it is usually named according to the double name method of "genus + species"). "Bacillus" means "rod" in Latin --- bacteria in this genus all grow like rods, so they are called "bacilli". And because this bacterium is particularly easy to multiply in grass, it is also called Hay Bacillus and Grass Bacillus in English, so it is Bacillus subtilis.

Bacillus subtilis is very smart --- when it finds that the living environment is not ideal (usually lack of nutrients), it will form a dormant living cell form, which we call "spore". At this time, the spore contains all the genetic material (alive), and is surrounded by a thick three-layer spore wall (the inner layer is the spore wall, the middle layer is composed of peptidoglycan, and the outer layer is a protein shell; absolutely not afraid of wind and rain outside. Hit), you can sleep peacefully. When the environment is suitable for survival, hey, it can wake up again!

Where is the power of spores? It is resistant to high temperature, drought, high acid and alkali, hypertonicity, radiation and many chemical drugs. It is called "the most stress-resistant organism in the entire biological world", and it is invincible.

In simple terms, the mechanism is mainly as follows:
Each layer of spore wall is very powerful, like wearing layers of armor, resisting the entry of harmful substances;
Low water content (dehydrated by calcium ions in the process of spore formation, see the above animation), which is helpful for heat resistance;
The 2, 6-dipicolinic acid (dipicolinic acid, DPA; accounting for 10-15% of the dry weight of bacteria) rich in spores has the effect of protecting and stabilizing protein & DNA.

In animal nutrition, the super ability of Bacillus subtilis to form spores can bring a big benefit --- that is, we can prepare it into an inoculum in a "spore form". As long as it is not given a source of nutrition, it is particularly stable and easy to store. The key is to be able to withstand various "difficulties" that may be encountered in the process of feed processing, such as the high temperature environment and the acid environment in the stomach. And when it enters the animal intestines smoothly, it seems to be in a warm and comfortable canteen, and it can quickly recover and reproduce.

This is why Bacillus subtilis is widely used in the animal nutrition industry.
We know that only those that are beneficial to the host can be called probiotics. So, how does Bacillus subtilis become "probiotic" after resuscitation in the animal's intestines? In principle, today, there are three main mechanisms.

1). It is an aerobic bacteria and needs oxygen to survive, so it inhales oxygen vigorously in the intestines, which creates a suitable living environment for other probiotics such as lactic acid bacteria and bifidobacteria that do not like oxygen very much. Strictly speaking, lactic acid bacteria are facultative anaerobes and can live with or without oxygen, but in an anaerobic environment, they can produce lactic acid, which can inhibit the growth of harmful bacteria, such as E. coli and Salmonella. Bifidobacterium is strictly anaerobic, which makes it even happier. After its team grows, it can also exert a series of beneficial effects on the host. (In addition to oxygen consumption, Bacillus subtilis can also improve the environment for other probiotics by lowering the pH of the intestine and its metabolites)

Why are lactic acid bacteria and bifidobacteria widely used in food, but seldom used in feed? It is because the two of them do not have the ability to produce spores and cannot handle the feed processing link. Therefore, Bacillus subtilis plays an "assist" role, indirectly regulating the intestinal microecosystem, reducing pathogenic bacteria, and thereby reducing the occurrence of intestinal diseases.

2). The second point is closely related to the first point --- if from the beginning, "good bacteria" such as Bacillus subtilis and lactic acid bacteria occupy the position of the dominant intestinal flora, then they themselves can also be competitively rejected Directly reduce the colonization of pathogenic bacteria in animal intestines. At the same time, it also protects the integrity of the intestinal barrier.

This is very important in breeding. Taking poultry as an example, we know that necrotizing enteritis is the most important challenge, and Clostridium perfringens is the main instigator. Many studies have found that Bacillus subtilis has the ability to reduce Clostridium perfringens, so naturally, the risk of necrotizing enteritis is reduced.
3). It can secrete many nutrients (vitamins, amino acids, organic acids, etc.), enzymes (such as protease subtilisin, etc.), and other active substances (such as surfactin, etc.) during its own metabolism. To a certain extent, these metabolites can promote nutrient absorption, improve intestinal health, and have antibacterial effects --- Take surfactin as an example, it can kill bacteria by directly destroying the cell membrane of pathogenic bacteria.