Lactic acid bacteria cannot block the growth and reproduction of Vibrio in aquaculture
Teng's Aquatic Products Business Network - Contemporary Aquaculture Magazine exclusive report:
Lactic acid bacteria is a general term for a class of non-spore-forming, Gram-positive bacteria that ferment carbohydrates with lactic acid as the main product. All bacteria that can produce lactic acid from the fermentation of glucose or lactose are collectively called lactic acid bacteria. Lactic acid bacteria are a fairly diverse group of bacteria, currently divided into at least 18 genera, with more than 200 species in total.
1. Types
Although lactic acid bacteria have many properties and types, we can still clearly divide them into two major categories based on their source of origin:
(1) Animal-derived lactic acid bacteria
Obtained from animals. Because the strains are often in a relatively unstable state, their biological efficacy is also relatively unstable, and when consumed in large quantities, they can easily cause animal protein allergies in humans, that is, rejection reactions.
(2) Plant-derived lactic acid bacteria
Because they are obtained from plants, they are easily absorbed by the human body. No matter how large the amount ingested, the human body will not produce a foreign protein rejection reaction, and plant-derived lactic acid bacteria are more vigorous than animal-derived ones, and can reach the human small intestine for colonization in numbers 8 times greater than animal-derived ones, thereby exerting their powerful and stable biological efficacy.
Humans were already using lactic acid bacteria 5000 years ago; the use of lactic acid bacteria is not a discovery of modern people.
2. Functional characteristics
When a microbial ecological preparation produced from a good strain of lactic acid bacteria is applied in aquaculture, its main functions are: changing the composition of the intestinal flora of aquatic organisms, improving gastrointestinal function, maintaining the balance of intestinal flora, and forming an antibacterial biological barrier. But it absolutely does not, and cannot, have the effect of blocking the growth and reproduction of Vibrio.
What is blocking? Interrupting the process or progress (of something) due to obstruction by a certain substance is called blocking.
What are blocking drugs? Blocking drugs refer to drugs that act on the substrate or as competitive inhibitors that play a leading role in the viral transcription process, thereby preventing viral replication. These drugs are mainly divided into the following 5 categories. (1) Nucleoside analogues. Mainly used to treat immunodeficiency diseases and related syndromes; they have serious adverse reactions and require long-term or lifelong medication. (2) Non-nucleoside reverse transcriptase inhibitors. These drugs can be used in combination with other antiviral drugs to treat viral infections. (3) Protease inhibitors. Combined use of these drugs with nucleoside analogues can effectively inhibit viral replication and reduce adverse reactions. (4) Entry inhibitors. These drugs achieve antiviral effects by interfering with the adhesion and fusion of viruses with host cells. (5) Integrase inhibitors. These drugs inhibit the integration of viral genes with host cell genes by integrase.
At present, whether for humans or animals, there are very few drugs used for blocking treatment, and the drugs used for blocking treatment are all used for viruses, not bacteria. Drugs used to block bacterial DNA synthesis are all antibiotics. And lactic acid bacteria and their metabolites absolutely do not have the effect of blocking the growth and reproduction of Vibrio in aquaculture water or aquatic products!
3. Mechanism of action
The principle by which lactic acid bacteria can exert effects in aquatic animals is biological antagonism, and they do not have the function of blocking the growth and reproduction of Vibrio.
What is biological antagonism? Biological antagonism refers to the struggle among microorganisms of mutual resistance, mutual exclusion, mutual competition for living space and conditions, and even mutual killing. A stable, normal microflora in biological balance has an obvious biological antagonistic effect on foreign bacteria in aquaculture water and aquatic products. The causes of biological antagonism are the effects of microorganisms and the various secreted substances they produce, among which anaerobic bacteria play a major role.
Biological antagonism roughly takes the following forms:
(1) Changing the micro-environment of aquaculture water and aquatic organisms. The organic acids produced during bacterial growth lower the pH value in the aquaculture water and the environment of aquatic organisms, inhibit foreign bacteria, promote intestinal peristalsis, and clear foreign bacteria.
(2) Occupancy. Bacteria closely combine with the mucosal epithelial cells of aquatic organisms to form "occupancy" protection (biological barrier), thereby excluding foreign bacteria.
(3) Competition for nutrients. Because anaerobic bacteria (most of which are beneficial bacteria) are present in very large numbers in their specific aquatic organism environment, they are at an advantage in competing for nutrients with foreign bacteria, thereby limiting the growth and reproduction of foreign bacteria.
(4) Secreting antibacterial substances. The antibacterial substances produced by microorganisms during biological fermentation play a crucial role, having a powerful inhibitory and killing effect on foreign bacteria.
(5) Immune effect. The normal microflora, in cooperation with the host's immunity, can also produce very effective biological antagonism.
4. Application of lactic acid bacteria in aquaculture
Lactic acid bacteria are a major group of bacteria used by humans as food microorganisms, and have achieved good results especially in enhancing the health functions of milk, improving silage quality, improving the production performance of livestock and poultry, and reducing the impact of storage of livestock products on meat flavor. They are widely used in fields such as food, medicine, light industry, and animal husbandry.
At present, reports on lactic acid bacteria in aquaculture mainly focus on the inhabiting conditions of lactic acid bacteria in the gastrointestinal tract and other internal organs of aquatic animals. The application of lactic acid bacteria in aquaculture is relatively extensive, mainly by mixing them into feed and feeding them together to aquatic animals, or by spraying them into water bodies as the dominant bacteria in EM bacteria.
Adding lactic acid bacteria to aquaculture water to improve the aquaculture water environment, inhibit the reproduction and growth of harmful bacteria in the water, regulate the balance of algal phases, and control harmful bacteria and algae.
5. Can lactic acid bacteria block the growth of Vibrio in aquaculture water or aquatic organisms?
Whether from the functional characteristics or the mechanism of action of lactic acid bacteria, it is proven that lactic acid bacteria cannot block the growth and reproduction of Vibrio in aquaculture water or aquatic organisms.
This article is selected from the March 2015 issue of Contemporary Aquaculture. The article is an exclusive report of Teng's Aquatic Products Business Network. Please indicate the source when reprinting. Violators will be held legally responsible. Thank you for your cooperation.