Microbial Interactions:

Microbes can physically interact with other organism in any number of ways. The physical interaction of microbes may either be permanent life cycle or intermittent or discontinuous contribution.

Intermittent symbiosis of microorganisms with plants

The intermittent and cyclic symbiosis results in variety of chronic diseases. The interaction of microorganisms with plants and animals shall be intermittent and cyclic symbiosis. For instance, protobacterium live in angiosperm (Ardisia), cyanobacterium found in rice paddy fern, nitrogen fixing bacteria rhizobia found in bean, cyanobacterium found in tropical angiosperm like Gunnera are bacterial interactions with plants.

Intermittent symbiosis of microorganisms with aquatic environment

Intermittent interactions of bacteria with aquatic microorganisms are complex in structure. For instance, symbiodinium that is dinomastigote found in coral coelenterates, vibrio and photo bacterium found in luminous fish and photo bacterium found in squid.

Permanent symbiosis of microorganism with animals

Host animals shall be aphids, squids, nematodes, leeches and etc. Here each organism attach to the particular host throughout their lifecycle. Luminous bacteria which live in Sepiolid squid (Euprymna scolopes) contribute luminescence by their symbiotic relationship. Enteric bacterium is found in medicinal leech helps in digestion of blood. Bacteria like Buchnera aphidicola live in Schizaphis gramium, aphid synthesis amino acids. Luminous bacteria namely Photorhabdus luminescens lives in heterorhabditis, nematode worm is a type of predatisic relationship and it helps in synthesis of antibiotic. Gill cell bacteria found in Lyrodus pedicellatus, shipworm mollusk helps in fixing of nitrogen and digestion of cellulose.

Types of microbial physical interaction

Prevalently found interactions of microbes are mentioned below.

• Endosymbiont and
• Ectosymbiont

Ectosymbiont: When single organism is found on the other organism’s surface it is referred as ectosymbiont. Ectosymbiont are so small in size found on the larger organisms. Physical contact is strong when different organisms interact with same sized species. A consortium is best term to explain such physical relationship. A consortia formation is so complex in aquatic environments. For instance Thiothrix is a sulfur utilizing bacteria. It is found attached to mayfly larva body’s surface which has a parasitic bacterium in their body.

Endosymbiont: When an organism is found inside the cells or body of other organism they are referred as endosymbiont. Endosymbiosis is mostly obligate. For instance, nitrogen fixing bacteria found in root nodules of legumes, algae that are found in corals and bacterial endosymbiont feed nutrients to insects. Mitochondria and chloroplasts are instance of obligate endosymbiont. Endosymbiosis may harm any of the organisms.

Interaction between microbes

It is evident either of the microorganisms make an intact contact with other organism, hence it is easy to predict type of interaction and contribution to ecological environment. There are some types of physical intact with the organism that provides no information on contribution or prediction about their interaction. This type of interaction can either be positive or negative results.

Positive interactions

Microbial interactions which result in the benefit of host and microorganism are positive microbial interactions. Mutualism, protocooperation and commensalisms are positive interactions.

Mutualism: The interaction of organism and host is completely dependent on each other for effective metabolism. Both the organism is benefited from their mutualisitic relationship. Parasite – termite relationship and lichens are examples of microbial interactions.

Protocooperation: It is similar to mutualism. Unlike mutualism it is not obligatory relationship. They can survive independently when they separate. Interaction of nitrogen fixing organism with cellulolytic organism and interaction of desulfovibrio with chromatium are protocooperative relationship.

Commensalism: The relationship benefits each other without affecting other organism. Waste of one organism is the substrate of other organism.

Negative interactions

The interactions that result in adverse ecological effect are referred as negative interaction. Predation, parasitism, amensalism and competition are negative microbial interactions.

Predation: The predator ultimately harms or kills the prey. For instance, Bdellovibrio is a periplasmic predator.

Parasitism: By this interaction organism is benefited whereas host is affected. For instance parasitic fungi like Rhizophydium solani with Mucor.

Amensalism: The release of some specific compounds by one organism has a negative effect on another organism is referred as amensalism. For instance, Bacteriocin production during cell wall disruption is amensalic relationship.

Competition: When same resource is attacked by different organism of same community resulting in depletion of resource or provision of limited resource. For instance, limited nutrient supply during transportation in Chemostat is competitive.