Assignment On Microbial Associations

Assignment On Microbial Associations

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  1 North Maharashtra University SchoolOf Life Sciences Assignment On Microbial Associations Submitted To Dr. Bipin K. Salunkhe Submitted By Miss. Mugdha P. Padhye
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  2 Index- Sr. No. Contents Page No. 1 Introduction 3 2Mutualism 5 3 Proto-co-operation OR Synergism 6 4 Syntrophism 7 5 Commensalism and Amensalism 8 6 Antagonism 9 7 Role of Microbial Associations in Environment 11 8 References 12
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  3 Introduction- Varieties of waysare adapted by microbes to tolerate physical environment like that of Symbiosis. In nature, microbes can make symbiotic association with plants, animals or other microbes. The close association between two different organisms is called as symbiosis (Ancient Greek word sýn "with" and bíōsis "living"). A German mycologist Heinrich Anton de Bary (1879) coined the term symbiosis (literally means living together) to describe organisms that live together in physical association. He defined it as "the living together of unlike organisms." In symbiosis, Bary clearly included commensalism, mutualism and parasitism. The organisms involved in symbiotic interactions are called as symbionts. Considering the closeness; the symbiont can be categorized as ectosymbiont and endosymbiont. Some symbiotic relationships are obligate, means that both symbionts entirely depend on each other for survival. For example, many lichens consist of fungal and photosynthetic symbionts that cannot live on their own. Whereas, others are facultative, means that they can, but do not have to live with the other organism. Endosymbiosis is any symbiotic relationship in which one symbiont lives within the tissues of the other, either in the intracellular space or extracellularly. Examples are rhizobia, nitrogen-fixing bacteria that live in root nodules on legume roots; actinomycete nitrogen-fixing bacteria called Frankia, which live in alder tree root nodules; single-celled algae inside reef-building corals; and bacterial endosymbionts that provide essential nutrients to about 10% -15% of insects. Ectosymbiosis, also referred to as exosymbiosis, is any symbiotic relationship in which the symbiont lives on the body surface of the host, including the inner surface of the digestive tract or the ducts of exocrine glands. Examples of this include ectoparasites such as lice, commensal ectosymbionts such as the barnacles that attach themselves to the jaw of baleen whales, and mutualist ectosymbionts such as cleaner fish. Now here, we are going to discuss several microbial associations like Mutualism, Syntrophism, Proto-co-operation, Commensalism, Amensalism, Predation, Parasitism, etc.
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  5 Mutualism- Mutualism is anyrelationship between individuals of different species where both individuals derive a benefit. Features of Mutualism- It is mostly a type of obligate, endosymbiotic interaction where both the partners do not survive individually and metabolically depend on each other. Thus, it is a bi-directional phenomenon. Types of Mutualism- Trophic Mutualism (e.g. N2 fixation), Dispersive Mutualism (e.g. Pollination), Defensive Mutualism (e.g. Bull horn acacias provide nutrients and housing for acacia ants in return for protection from herbivores) Examples of Mutualism- 1. Symbiotic Nitrogen Fixation Several microorganisms have the ability to fix atmospheric nitrogen by symbiotic association with legume plants. Major genera include Azotobacter, Rhizobium, Azospirillum, etc. 2. Ruminants and microbes Several anaerobic bacteria and fungi like Neocallimastix, Ciliates and Protozoa present in the Rumen of herbivorous animals digest the cellulose eaten by them through consumption of plants. 3. Lichens It is an obligate association in fungi (mycobiont) and algae (phycobiont) where algae provide food to fungi by photosynthesis and in turn, a fungus helps in absorption of moisture. Xanthori Platismatia Physcia
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  6 Proto-co-operation OR Synergism- Protocooperation is any facultative relationship between individuals of different species where both individuals derive a benefit. Pollination is a classic example of Proto-co-operation Features of Proto-co-operation- It is mostly ectosymbiotic, non obligatory i.e. facultative interaction where both the partners get benefitted (Bi-directional phenomenon). Example of Proto-co-operation- Desulfavibrio provides CO2 and H2S to Chromatium. Desulfavibrio require organic matter and sulphate. These are produced by Chromatium by reduction of CO2 to O2 through photosynthesis and oxidation of sulphide to sulphate. In this way, both partners provide nutrients to each other. Difference between Mutualism and Proto-co-operation- In proto-co-operarion, two or more organisms interact and benefit from each other in some way, but that the relationship is not essential or even required in order for each to thrive and survive, whereas mutualism is more reliant upon these interactions and normally the cessation of the interaction would have a negative effect upon one or more of the participants.
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  7 Syntrophism- Syntrophism is asymbiotic association in which growth of one organism is supported/ improved by growth factors or metabolites, secreted by other organism. (Syn-“together”, Trophe- “nourishment”) Features of Syntrophism- It is an obligatory; ectosymbiosis where one partner is beneficial for the other (positive, unidirectional interaction). Example of Syntrophism- Phyllosphere and Rhizosphere The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a plant as a habitat for microorganisms. The plant leaves and stem secrete organic compound, which prevent growth of pathogenic microbes; in turn, phyllosphere protects the plant. The below-ground bacterial habitats (i.e. the root surfaces) are referred to as the Rhizosphere. It is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms which induce N2 fixation, root-hair formation in plants. Electron micrograph showing bacteria on the surface of an Arabidopsis leaf
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  8 Commensalism- Commensalism is aclass of relationship between two organisms where one organism benefits but the other is neutral (there is no harm or benefit). Features of Commensalism- It is an ectosymbiotic, obligatory interaction wherein only one is get benefitted (unidirectional, positive interaction). Example of Commensalism- Several microorganisms reside on or in human body as a commensal. The typical example is of Escherichia coli, normally found in human intestine. Amensalism- Amensalism is an interaction where a specific compound secreted by one organism imparts negative effect on other organism. Features of Amensalism- It is an ectosymbiotic association wherein only one is gets benefitted (unidirectional, negative interaction). In such association, one partner never grows due to the inhibitory substance secreted by other partner. Example of Amensalism- Antibiotics Penicillin secreted by Penicillum notatum is harmful to Staphylococcus aureus.
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  9 Antagonism- In antagonistic interactionsone species benefits at the expense of another (e.g. parasitism and predation). Parasitism- Parasitism is an association in which one organism (host) is harmed while other (parasite) gets benefitted. Features of Parasitism- It is an ecto or endosymbiotic association wherein one of the partners (host) get harmed (unidirectional, negative interaction). Ocassionally, death of the host may occur. Types of Parasites- 1. Ectoparasites Parasites that live on the surface of the host (e.g. mites, lice, etc.) 2. Endoparasites Parasites that live inside the host (e.g. Plasmodium spp., Salmonella typhi, etc.) A Tomato Hornworm Roundworm Epiparasites- An epiparasite is one that feeds on another parasite. This relationship is also sometimes referred to as hyperparasitism which may be exemplified by a protozoan (the hyperparasite) living in the digestive tract of a flea living on a dog.
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  10 Predation- Predation is aninteraction in which one organism (predator) engulfs/eats other organism (prey). Features of Predation- It is a type of ectosymbiosis where death of prey occurs (Unidirectional, negative interaction). Example of Predation- 1. Bdellovibrio Predator of gram negative bacterial cells,grows in periplasmic space and feed on protoplasm of the cell. Life Cycle of Bdellovibrio Vampirococcus with Chromatium 2. Vampirococcus Aquatic obligate parasite that is specific to Chromatium. They are, mostly, considered as epibionts.
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  11 Role of MicrobialAssociations in Environment- 1. Associations with Animals and Plants Microbes invariably enter into beneficial, sometimes essential, associations with all higher forms of organisms, including insects, invertebrates, fish, animals and plants and do various functions like; N2 fixation, food digestion, protection from other pathogens, etc. 2. Production of Foods and Fuels Several microbes are used in manufacture of dairy products, fermented products, beverages, etc. 3. Key role in Co-evolution Symbiosis is a major driving force behind evolution. Co-evolution is “the change of a biological object triggered by the change of a related object.” Co-evolution of different species includes the evolution of a host species and its parasites, predator and prey, host and symbiont, host and parasites, etc. 4. Medical, Pharmaceutical and Biotechnological Applications Antibiotics, vaccines produced from microbial associations are used for the treatment and prevention of infectious diseases. 5. Basic research These associated microbes can be used for basic research and the study of cellular life as well as in Environmental and Ecological studies.
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  12 References- 1. http://in.answers.yahoo.com/question/index?qid=20080515031250AAXbTZ5 2. http://encyclopedia2.thefreedictionary.com/Microbial+Associations 3.http://upendrats.blogspot.com/2009/08/microbial-association-microbial.html 4. http://en.wikipedia.org/wiki/Symbiosis 5. Foundations In Microbiology- Ulhas Patil, Dr. J. S. Kulkarni, Dr, A. B. Chaudhari, Dr. S. B. Chincholkar