- The impacts that the species in a community have on one another are referred to as biological interactions.
- Microbial interactions can take many different forms, including interactions with other bacteria, Plant-Germ interactions that support plant development, interactions with animals, interactions with people, interactions with water, etc.
- Microbial interactions are pervasive, diversified, essential to the operation of every biological community, and they play a key role in the biogeochemistry of the whole planet.
- Mutually beneficial interactions are the most frequent cooperative interactions found in microbial communities. According to whether both populations and one of them gain from the relationships, or one or both populations are badly affected, the interactions between the two populations are categorised.
- There are many different types of symbiotic relationships between the species, including mutualism, parasitism, amensalism, commensalism, competition, predation, and protocooperation.
Table of Contents
Types of Microbial Interaction
1. Mutualism
2. Syntrophism
3. Protocooperation
4. Commensalism
5. Amensalism (antagonism)
6. Competition
7. Parasitism
8. Predation
Types of Microbial Interaction
- Positive interaction: Syntrophism, Commensalism, Mutualism, Proto-Cooperation
- Ammensalism (antagonism), parasitism, predation, and competition are examples of negative interactions
1. Mutualism
- It is described as a connection where each creature interacting gains something from the partnership.
- Mutualist and host are physiologically obligated to one another in this connection.
- It is extremely clear that in a mutualistic connection, one member of the association cannot be replaced by another species.
- Close physical touch between interacting species is necessary for mutualism.
- The mutualistic interaction between organisms enables them to live in an environment that neither species could occupy on their own.
- They may function as a single organism because of the mutualistic interaction between them.
Mutualism examples:
Lichens: Lichens provide a wonderful illustration of mutualism. They are an assemblage of certain fungal and algal genera. Mycobiont, a fungus, and phycobiont, an alga—both of which are green algae and cyanobacteria—are partners in the lichen (Trabauxua).
2. Syntrophism
- It is a relationship in which one organism's development is either influenced by or enhanced by the substrate offered by another organism.
- Both associated species gain from one another in syntrophism.
Population 1 uses Compound A, Population 2 uses Compound B, and Population 1 and 2 both use Compound C.
In this hypothetical example of syntrophism, population 1 is capable of using and metabolising component A to create compound B, but it is unable to do it without the assistance of population 2. Although Population 2 cannot use Compound A, it can metabolise Compound B to produce Compound C. Following that, a metabolic process that neither population alone could carry out is carried out by both populations 1 and 2, resulting in the production of the final product.
Examples of syntrophism:
a. Methanogenic ecosystem in a sludge digester
- Methanogenic bacteria rely on interspecies hydrogen transfer from fermentative bacteria to make their methane.
- Carbohydrates are used by anaerobic fermentative bacteria to produce CO2 and H2, which are then used by methanogenic bacteria (Methanobacter) to manufacture methane.
b. Lactobacillus arobinosus and Enterococcus faecalis
- Lactobacillus arobinosus and Enterococcus faecalis may coexist and thrive in the minimum media, but not by themselves.
- Because Lactobacillus needs phenylalanine, which is generated by Enterococcus faecalis, and E. faecalis needs folic acid, which is produced by L. arobinosus, there is a synergistic link between the two bacteria.
3. Protocooperation
- It is a partnership where each organism in an association benefits from the others' presence.
- While this connection resembles mutualism, in protocooperation the interactions between the organisms are not as obligated as they are in mutualism.
Examples of Protocooperation:
a. Association of Desulfovibrio and Chromatium: The carbon cycle and the sulphur cycle are working together in this manner.
b. Interaction between N2-fixing bacteria and cellulolytic bacteria such as Cellulomonas.
4. Commensalism
- It is a connection in which one organism (commensal) benefits from the association while another organism (host) neither benefits from nor is hurt by the interaction.
- It is a unidirectional relationship, and the commensal may thrive even if it is cut off from the host.
Examples of commensalism:
a. Non-pathogenic E. coli in the intestinal tract of humans:
As a facultative anaerobe that consumes oxygen and reduces the amount of oxygen in the gut, E. coli fosters an environment that is favourable for obligate anaerobes like Bacteroides. Bacteroides have no effect on the host E. coli.
b. Flavobacterium (host) and Legionella pneumophila (commensal):
Legionella pneumophila uses cystine, which is excreted by Flavobacterium, to thrive in the aquatic environment.
c. Association of Nitrosomonas (host) and Nitrobacter (commensal) in Nitrification:
Finally, Nitrobacter takes the energy from nitrite to oxidise it into nitrate after Nitrosomonas has converted ammonia to nitrite.
5. Amensalism (antagonism)
- Ammensalism or antagonism is the term for the interpopulation connection that results when one microbial population generates chemicals that are antagonistic to another microbial population.
- There is a bad connection there.
- While other populations are suppressed, the initial population that generates inhibitory compounds is unharmed or may even experience competition and thrive in the ecosystem. Antibiosis is the name for this chemical inhibition.
Examples of the antagonism (amensalism):
a. Lactic acid produced by lactic acid bacteria in the vaginal tract:
Numerous healthy bacteria in the vaginal canal create lactic acid, which inhibits many harmful species including Candida albicans.
b. Skin normal flora:
Numerous skin pathogenic microorganisms are inhibited by fatty acids generated by skin flora.
c. Thiobacillus thiooxidant:
By oxidising sulphur, Thiobacillus thioxidant creates sulfuric acid, which lowers the pH of the culture medium and prevents the majority of other bacteria from growing.
6. Competition
- The rivalry between the two microbial populations implies a bad relationship in which both populations are negatively impacted in terms of survival and growth.
- Competition happens when two populations share the same resources, such as food or space, and results in a decreased maximum density or growth rate for the microbial population.
- The microbial population competes for any resources that limit their ability to expand, including carbon, nitrogen, phosphorus, vitamins, growth hormones, etc.
- Because one population will win the competition and the other one will be wiped out, competition prevents both populations from occupying the exact same ecological niche.
Examples of competition:
a. Competition between Paramecium caudatum and Paramecium aurelia:
When these protozoa are combined, both species of Paramecium feed on the same bacterial population. Due to competition, P. aurelia grows faster than P. caudatum.
7. Parasitism
- In this arrangement, one population (the parasite) benefits and receives nutrients from the other population (the host), which suffers.
- The relationship between a host and a parasite is defined by a considerable amount of time spent in touch, either physically or metabolically.
- While some parasites, known as ectoparasites, reside outside the host cell, others, known as endoparasites, do so inside the cell.
Examples of parasitism:
a. Viruses:
A highly particular host-specific obligatory intracellular parasite, viruses. Numerous viruses (bacteriophage), as well as fungus, algae, protozoa, and other organisms, are parasites of bacteria.
b. Bdellovibrio:
Many gram-negative bacteria harbour an ectoparasite called Bdellavibrio.
8. Predation
- When one creature (a predator) engulfs or attacks another organism, it is a common occurrence (prey).
- Whether the prey is bigger or smaller than the predator, it usually dies as a result.
- Predator-prey interactions are often brief.
Examples of Predation:
a. Protozoan-bacteria in soil:
Numerous protozoans may feed on different populations of bacteria, which aids in keeping the number of soil bacteria at an ideal level.
b. Bdellovibrio, Vamparococcus, Daptobacter, etc are examples of predator bacteria that can feed on a wide range of the bacterial population.
