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![Mutualism
• Mutualism [Latin mutuus, borrowed or reciprocal] defines the relationship in which
some reciprocal benefit accrues to both partners.
• This is an obligatory relationship in which the mutualist and the host are
dependent on each other.
• When separated, in many cases, the individual organisms will not survive.
• Example: lichen (between fungus and alga), symbiotic nitrogen fixing
(between plant and nitrogen fixing bacteria like Rhizobium), mycorrhizae
(between plant and fungi)
• In symbiotic nitrogen the plant provides sugars from photosynthesis that are
utilized by the nitrogen-fixing microorganism for the energy it needs for
nitrogen fixation. In exchange for these carbon sources, the microbe
provides fixed nitrogen to the host plant for its growth
• In mycorrhizal interaction the plant makes organic molecules such as sugars
by photosynthesis and supplies them to the fungus, and the fungus supplies
to the plant water and mineral nutrients, such as phosphorus, taken from
the soil.](https://image.slidesharecdn.com/ge-microbe-microbeinteraction1-250207134010-d1909509/75/GE-microbe-microbe-interaction-1-pptx-8-2048.jpg)
![Protocooperation
It is a type of syntrophic relationships. Syntrophism [Greek syn, together, and
trophe, nourishment] is an association in which the growth of one organism
either depends on or is improved by growth factors, nutrients, or substrates
provided by another organism growing nearby.
Both the populations are benefited
Positive but not obligatory for the survival of either population
Nonetheless, the most useful distinction between protocooperation and
mutualism is the observation that cooperating organisms can be separated
from one another and remain viable, although they may not function as well.](https://image.slidesharecdn.com/ge-microbe-microbeinteraction1-250207134010-d1909509/75/GE-microbe-microbe-interaction-1-pptx-10-2048.jpg)
![Commensalism
Commensalism [Latin com, together, and mensa, table] is a relationship in
which one symbiont, the commensal, benefits while the other (sometimes
called the host) is neither harmed nor helped
Common in nature but not obligatory
When the commensal is separated from its host experimentally, it can
survive without the addition of factors of host origin.
This is a unidirectional process
Commensal feed on substances captured or ingested by the host and
often obtain shelter by living either on or in the host. But the commensal
is not directly dependent on the host metabolically and causes it no
particular harm.](https://image.slidesharecdn.com/ge-microbe-microbeinteraction1-250207134010-d1909509/75/GE-microbe-microbe-interaction-1-pptx-12-2048.jpg)
![Example of Amensalism
• Antibiotic production: A classic example of amensalism is the production
of antibiotics that can inhibit or kill a susceptible microorganism
• Bacteriocin: Other important amensalistic relationships involve microbial
production of specific proteinaceous compounds that disrupt cell wall or
plasma membrane integrity of target microorganisms. These include the
bacteriocins,
• [Other examples are defensins from phagocytes, dermicidins in human
sweat, cathelicidins from skin, organic acids by LAB during fermentation
of milk].](https://image.slidesharecdn.com/ge-microbe-microbeinteraction1-250207134010-d1909509/75/GE-microbe-microbe-interaction-1-pptx-15-2048.jpg)
GE- microbe-microbe interaction (1).pptx
- 1. Terminology • Habitat: Inecology, a habitat is the type of natural environment in which a particular species of organism lives. It is characterized by both physical and biological features. A species' habitat is those places where it can find food, shelter, protection and mates for reproduction. • Microhabitat: A habitat can be subdivided into regions with different environmental conditions like exposure to light, humidity, temperature, air movement and other factors. These subdivisions are called microhabitat. For example, in a pond, some organisms are surface dwellers while some others are bottom dwellers. • Niche: An organism’s role, function or position in an ecosystem. In other words, niche is a term used to indicate not only the habitat but also the role played by the organisms in the environment. According to Odum, while the habitat is the organism’s ‘address’, its ecological niche is its ‘profession’. • Niche Differences: Those factors that keep organisms from competing for resources (like plants that draw nutrients from different depths). • Population: Population refers to individuals of a given single species living in a given place in a given time. • Community: Community is a broader concept that refers to all populations (so, different species) living in a given place in a given time
- 2. Type of interactions •Under natural conditions, organisms live together influencing each others’ life directly or indirectly. Vital processes like nutrition, growth and reproduction are dependent upon this interaction • Interaction may occur between individuals of same species (intraspecific interaction) or between those of different species (interspecific interaction) • More complex interactions may exist between taxonomically distantly related species, such as between plants and microbes or animals and microbes • For different types of relationships among organisms, various authors have used different terminology. There is no agreement on various terms used to denote types of interaction • Sometimes interaction between two organisms may be very complex to explain and accommodate it to any one category
- 3. Symbiosis (sym: together;bio: life) The term symbiosis in its original broadest sense means “an intimate longterm relationship of two or more populations” as proposed by H A deBary (1879) Ecologists sometimes use the terms “mutualism” and “symbiosis” interchangeably, but it is not true. Symbiosis is an ecological interaction between at least two species (=partners) where there is persistent contact between the partners. In symbioses, one partner is often smaller, lives on or in the larger partner, and has a shorter lifespan than the larger partner. The smaller partner is a symbiont, and the larger partner is a host. Ectosymbiont: When one organism is located on the surface of another. endosymbiont: When one organism is located within another organism. Consortium: While the simplest microbial interactions involve two members, a symbiont and its host, a number of interesting organisms host more than one symbiont termed consortium. Microbial consortium is usually referred as group of diverse microorganisms that have the ability to act together in a community. Example, Fungi associated with plant roots (mycorrhizal fungi) often contain endosymbiotic bacteria, as well as having bacteria living on their surfaces
- 4. Types of relationship Most of the ecologists include all types of interactions including parasitism under symbiosis Burkholder (1952), on the basis of several combinations of 0 (no significant interaction), + (beneficial like growth, survival etc) and – (inhibitory to growth, survival etc) between two species, recognised nine possible combinations
- 5. Burkholder classification ofinteraction Combination Detailed effect Interaction type 0 0 Neither population affects the other neutralism - - Direct inhibition of each species by the other competition - - Indirect inhibition where common resources is in short supply competition (resource based type) + + Interaction favouring both but non- obligatory protocooperation + + Interaction favouring both and obligatory mutualism + - Parasite, generally smaller than the host parasitism + - Predator, generally larger than the pray Predation - 0 One inhibited another not affected Amensalism + 0 One benefited another not affected commensalism
- 6.
- 7. Neutralism • Two differentspecies of microorganisms occupy the same environment without affecting each other. • Two organisms behave entirely independent of one another • There is no effect of one organism on the other • Can be caused by physical, spatial or temporal separation • Example: Two organisms separated by clay, grown at different locations in soil or in different time
- 8. Mutualism • Mutualism [Latinmutuus, borrowed or reciprocal] defines the relationship in which some reciprocal benefit accrues to both partners. • This is an obligatory relationship in which the mutualist and the host are dependent on each other. • When separated, in many cases, the individual organisms will not survive. • Example: lichen (between fungus and alga), symbiotic nitrogen fixing (between plant and nitrogen fixing bacteria like Rhizobium), mycorrhizae (between plant and fungi) • In symbiotic nitrogen the plant provides sugars from photosynthesis that are utilized by the nitrogen-fixing microorganism for the energy it needs for nitrogen fixation. In exchange for these carbon sources, the microbe provides fixed nitrogen to the host plant for its growth • In mycorrhizal interaction the plant makes organic molecules such as sugars by photosynthesis and supplies them to the fungus, and the fungus supplies to the plant water and mineral nutrients, such as phosphorus, taken from the soil.
- 9. Example of mutualism •Lichen: the body of lichen is made up of a matrix formed by a fungus, within which an alga is embedded. • Role of fungus: absorption of moisture and minerals for algae • Benefit to fungus: acquires food manufactured by alga • Role of alga: Manufacture of food by photosynthesis • Benefit to alga: acquire moisture and minerals absorbed by fungus • When neither fungus nor alga can grow alone independently, then the interaction is mutualism. However in some lichens, the interaction is not obligatory, the alga is independent and the fungus acquire food from alga. Then it can be denoted as protocooperation. Some authors have explained the interaction as a type of parasitism too.
- 10. Protocooperation It isa type of syntrophic relationships. Syntrophism [Greek syn, together, and trophe, nourishment] is an association in which the growth of one organism either depends on or is improved by growth factors, nutrients, or substrates provided by another organism growing nearby. Both the populations are benefited Positive but not obligatory for the survival of either population Nonetheless, the most useful distinction between protocooperation and mutualism is the observation that cooperating organisms can be separated from one another and remain viable, although they may not function as well.
- 11. Example of Cooperation •Cellulomonas-Chromatium: • Role played by Chromatium: fixing of nitrogen • Benefit to Chromatium: absorb glucose liberated from cellulose degraded by Cellulomonas • Role played by Cellulomonas: degradation of cellulose liberating glucose • Benefit to Cellulomonas: absorb fixed nitrogen by Chromatium • Desulfovibrio-Chromatium: Desulfovibrio provides H2S and CO2 to Chromatium. Chromatium in turn provides SO4 2- and sugar to Desulfovibrio.
- 12. Commensalism Commensalism [Latincom, together, and mensa, table] is a relationship in which one symbiont, the commensal, benefits while the other (sometimes called the host) is neither harmed nor helped Common in nature but not obligatory When the commensal is separated from its host experimentally, it can survive without the addition of factors of host origin. This is a unidirectional process Commensal feed on substances captured or ingested by the host and often obtain shelter by living either on or in the host. But the commensal is not directly dependent on the host metabolically and causes it no particular harm.
- 13. Example of Commensalism Nitrosomonas-Nitrobacter interaction Role played by Nitrosomonas: oxidation of ammonium ion to nitrite Benefit to Nitrosomonas: Nil Role played by Nitrobacter: Nil Benefit to Nitrobacter: uses nitrite produced by Nitrosomonas to obtain energy for growth
- 14. Amensalism Amensalism (fromthe Latin for not at the same table) describes the adverse effect that one organism has on another organism. This is a unidirectional process based on the release of a specific compound by one organism which has a negative effect on another organism.
- 15. Example of Amensalism •Antibiotic production: A classic example of amensalism is the production of antibiotics that can inhibit or kill a susceptible microorganism • Bacteriocin: Other important amensalistic relationships involve microbial production of specific proteinaceous compounds that disrupt cell wall or plasma membrane integrity of target microorganisms. These include the bacteriocins, • [Other examples are defensins from phagocytes, dermicidins in human sweat, cathelicidins from skin, organic acids by LAB during fermentation of milk].
- 16. Predation • Predation amongmicrobes involves a predator species that attacks and usually kills its prey.
- 17. Example of Predation •Bdellovibrio: Bdellovibrio is an active hunter that is vigorously motile, swimming about looking for susceptible gram-negative bacterial prey. Upon sensing such a cell, Bdellovibrio swims faster until it collides with the prey cell. It then bores a hole through the outer membrane of its prey and enters the periplasmic space where it can reproduce. • Arthrobotrys : Another example is Arthrobotrys, which traps nematodes by use of constricting rings of hyphae. After the nematode is trapped, hyphae grow into the immobilized prey and the cytoplasm is used as a nutrient. Thus its an example of predaceous fungus.
- 18. Parasitism • Parasitism isone of the most complex microbial interactions; the line between parasitism and predation is difficult to define. • This is a relationship between two organisms in which one benefits from the other and the host is usually harmed. This can involve nutrient acquisition and/or physical maintenance in or on the host. • In parasitism there is always some co-existence between host and parasite. Successful parasites have evolved to co-exist in equilibrium with their hosts. This is because a host that dies immediately after parasite invasion may prevent the microbe from reproducing to sufficient numbers to ensure colonization of a new host.
- 19. Example of Parasitism •One example is the disease typhus. This disease is caused by the bacterium Rickettsia typhi, which is harboured in fleas that live on rats. It is transmitted to humans who are bitten by such fleas, so in order to contract typhus, one must be in close proximity to rats. • Viruses are an obligate intracellular parasite that exhibits great host specificity. There are many viruses that are parasite to bacteria (bacteriophage), fungi, algae, protozoa etc • The invasive nature of the fungal partner on algal cells in lichen is considered by some as parasitic relationship.
- 20. Competition • Competition ariseswhen different organisms within a population or community try to acquire the same resource, whether this is a physical location or a particular limiting nutrient • If one of the two competing organisms can dominate the environment, whether by occupying the physical habitat or by consuming a limiting nutrient, it will outgrow the other organism. This phenomenon was studied by E. F. Gause, who in 1934 described it as the competitive exclusion principle
- 21. Example of Competition Chlamydosporesof Fusarium, Oospores of Aphanomyces and conidia of Verticillium dahlae require exogenous nutrients to germinate in soil. But other fungi and soil bacteria deplete these critical nutrients required for spore germination and thereby hinder the spore germination resulting into the decrease in population.
- 22. Methods for studyingmicrobial diversity There are at least three main approaches for studying microbial diversity. These are • microscopic (i.e., using a microscope) • culturing (i.e., growing microbes in defined conditions in the lab) • molecular (i.e., assaying microbes in samples by directly characterizing their molecular components). Molecular approaches are generally known as “culture-independent” (metagenomics).