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Population Interactions

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Presentation on theme: "Population Interactions"— Presentation transcript:

1 Population Interactions

2 Population Interactions
Microbial Ecology Population Interactions Commensalism Synergism Mutualism Competition Amensalism Predation Parasitism

3 Microbial Ecology The interrelationships between microorganisms and their living ( biotic ) and nonliving ( abiotic ) environments * beneficial interactions : Mutualism * detrimental interactions : Competition and predation Microbial metabolism * The global biogeochemical cycles of elements * The biodegradation and bioremediation of wastes (sewage, pollutants) * The Recombinant DNA technology

4 Population Interactions
Positive Interactions Negative Interactions * To maintain community stability * Self-regulation mechanism * autochthonous populations (indigenous populations) allochthonous populations (foreign populations) * Neutralism Commensalism (편리공생) Synergism (상조공생) Mutualism (상리공생) Competition (경쟁) Amensalism (편해작용) Predation (포식) Parasitism (기생)

5 Population Interactions
Commensalism(편리공생) Commensal relationships are common, often occurring when the unaffected population modifies the habitat in such a way that a second population benefits. Bacteroides : E. coli ( gastrointestinal tract) Many commensal relationships are based on the production of growth fators (Vitamin). Some marine bacteria : surface algae (amino acid or Vitamin production)

6 Population Interactions
- Production of a primary bacterial film on the hull of a ship Primary infection ; secondary infections (opportunistic pathogens) Waste products of one organism may be a favorable substrate for the growth of another organism. ( Coprophagous fungi live on fecal material) Some bacterial populations produce and excrete growth factors, such as vitamins, that can be utilized by other populations.

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* Commensalism (편리공생) Unidirectional relationship Cometabolism Epiphytes Cometabolism of cyclohexane. Mycobacterium vaccae Propane Energy + CO2 + H2O Cometabolism Cyclohexane Cyclohexanone Assimilatory metabolism Yielding energy Cyclogexanol pseudomonas Energy + CO2 + H2O

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Epiphytes Fig. 3 Epiphytic Bacteria. Micrograph showing numerous epiphytic bacteria growing on the surface of an alga. (400X)

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* Synergism (상조공생) Proto-cooperation Both Populations benefit from the relationship but that the association is not obligatory * Syntrophism A type of synergism in which two populations supply each other’s nutritional needs. Cross-feeding

10 Population Interactions
Enterococcus faecalis and E. coli (arginine  putrescine) arginine  ornithine ornithine  putrescine Lactobacillus arabinosus and Enterococcus faecalis phenylalanime folic acid

11 Population Interactions
Fig. 4 Bacterial Synergism. The synergistic relationship between Lactobacillus arabinosus and Enterococcus faecalis permits each to grow on a minimal medium when both are present. The synergism is based on cross- feeding of essential growth factors. Neither can grow alone on a minimal medium.

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Various fermentative bacteria : low molecular weight fatty acids Anaerobic bacteria : fatty acids Molecular hydrogen H2-producing fatty acid-oxidizing bacteria grow better when H2 is consumed by methanogens because H2 does not accumulate as an end-product inhibitor. Syntrophomonas : butyric acid, caproic acid : valeric acid, enanthic acid Acetate + H2 Acetate + CO2 + H2 Syntrophobacter : propionic acid Acetate + CO2 + H2

13 Population Interactions
H2-Consuming methogenic archaca : The metabolism of the methanogens maintains very low concentrations of H2 . The removal of the H2 end-product  the equilibrium of fatty acid fermentation(H2 production)  increasing the growth rates of S.

14 Population Interactions
* Rhizosphere Effect Rhizosphere : The soil region in close contact with plant roots Rhizoshpere effect : A plant roots exert a direct influence on the soil bacteria The bacteria in the rhizosphere grow on the nutrients released from the plant roots

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Microbial populations in the rhizosphere may benefit the plant by Removing hydrogen sulfide Increasing solubilization of mineral nutrients needed by the plant for growth Synthesizing vitamins, amino acids, auxins, and gibberellins that stimulate plant growth Antagonizing potential plant pathogens through competition and the production of antibiotics

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* Mutualism ( 상리공생) An interrelationship between two specific populations that benefits both Endosymbiotic evolution Mitochondria, chloroplasts Mixotricha paradoxa is propelled by rows of attached bacterial cells( spirochetes)

17 Lichens A mutualistic relationship A primary producer : phycobiont (photosynthetic algal or cyanobacterial partners) A consumer : mycobiont (heterotrophic fungi) Habitat : rock surfaces Most lichens are resistant to extremes of temperature and desiccation self-sufficient organism The mycobiont provides physical protection for the lichen and produces organic acids that can solubilize rock minerals, making essential nutrients available to the lichen.

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Lichens A B Fig. 5 Lichens. A, Colorized micrograph of the lichen Letharia vulpina showing it is composed of a fungus (mycobiont) and an alga (phycobiont) living in mutualistic association. (1,000 X) B, Lichens growing on a rock. These organisms can grow under dry conditions.

19 F 19.53

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Lichens Fig. 6 Lichen Sensitivity to Air pollutants. Lichens are sensitive to air pollutants and disappear from urban areas. Contaminants in the air disrupt the delicate balance between the phycobiont and the mycobiont of the lichen.

21 Population Interactions
* Mutualism ( 상리공생) Endosymbionts Paramecium aurelia and various bacterial species The obligately endosymbiotic bacteria that appear as structure, such as kappa particles killer strains ( kappa particles) sensitive strains (lack bacterial endosymbionts)

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* Mutualism ( 상리공생) The presence of kappa particles gives an important advantage to killer strains when they compete with sensitive strains for available resources. The strains with kappa particles can eliminate strains that lack them.

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* Mutualism ( 상리공생) Mycorrhizae Mycorrhizae (fungal roots) are formed by mutualistic relationships between fungi and plant roots. The importance of this microorganism-plant interaction is attested to by the fact that 95% of all plants have mycorrhizae. Vesicles and Arbuscules VA is the most common form of mycorrhiza Fungal Gardens of Insects mutualistic relationships between microorganisms and animal populations. Some plant-eating insect populations Fungal gardens of myrmicine ants

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Mycorrhizae Fig. 7 Mycorrhizae. There are several types of mycorrhizae formed between fungi (purple) and plant root. A, Ectomycorrhizae. B, Endomycorrhizae. C, Vesicular-arbuscular(VA) mycorrhizae.

25 Population Interactions
* Mutualism ( 상리공생) Ruminant Animal-Microorganism Symbioses The rumen provides a stable, constant-temperature, anaerrobic environment for the establishment of mutualistic associations with microbial populations. Microbial populations within the rumen convert cellulose, starch, and other polysaccharides to carbon dioxide, hydrogen gas , methane, and low molecular weight organic acids.

26 Population Interactions
* Mutualism ( 상리공생) A portion of the low molecular weight fatty acids, carbon dioxide and molecular hydrogen produced by various fermentative bacteria, such as Ruminococcus, are converted by methanogenic bacteria to methane. 57.5 (C6H12O6) 65 acetate propionate butyrate + 60 CO CH H2O

27 Population Interactions
Ruminant Animal-Microorganism Symbioses Fig. 8 Microbial Metabolism in the Rumen. Anaerobic microorganisms within the rumen degrade polysaccharides. The fermentation products they form serve as the nutritional sources for ruminant animal. Methane is produced by methanogenic bacteria in the rumen.

28 Population Interactions
* Mutualism ( 상리공생) Bioluminescence The mutualistic relationship between some luminescent bacteria and marine invertebrates and fish FMNH2 + O2 + RCHO FMN + RCOOH + H2O + Light luciferase * Competition (경쟁) Competition occurs when two populations are striving for same resource (nutrient, light, space) Competitive exclusion

29 Population Interactions
Bioluminescence Fig. 9 Bioluminescence in Flashlight Fish. The flashlight fish (photoblepharon) maintains populations of luminescent bacteria (turquoise) near the eye and elsewhere on the body. This fish lives in dark regions of the ocean and the luminescent bacteria produce blue light.

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* Competition (경쟁) Fig. 10 Competition between Protozoa. Competition for available nutrients can lead to the exclusion of the less successful population. Paramecium caudatum is competitively excluded by P. aurelia in mixed culture.

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* Amensalism (편해작용) Amensalism or Antagonism : One population produces a substance inhibitory to another population. Streptococcus and Lactobacillus species : The production of lactic acid. . Antibiotics . Various other chemicals produced by microbial populations ; oxygen, ammonia, mineral acids, hydrogen sulfide, fatty acids alcohols

32 Population Interactions
* Predation (포식) Predator – Prey interactions Many protozoa prey on bacterial species ; grazing Predation is an important process in establishing transfers of food within an ecosystem to support the growth of higher organisms Some fungi are able to trap and consume much larger nematods Interactions of predator and prey species could lead to regualr cyclic fluctuations in the populations of the two species.

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* Predation (포식) Fig. 11 Predation-Protozoan Grazing on Bacteria. Colorized micrograph showing the phagocytic capture of a rodshaped bacterium by the soil protozoan Vahlkampfia. (5,200X) Many protozoa graze on bacteria as their food sources.

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* Predation (포식) Fig. 12 Predation-Nematode-trapping Fungi. A, Colorized micrograph showing hyphae of nematode-trapping fungus with a circle of cells that is the trap. When a nematode swims through this trap, the cells contract like a noose to capture the nematode. B, Colorized micrograph of a nematode-trapping fungus that forms a “sticky lethal lollipop.” When a nematode, as shown here, contacts this trap, it adheres to the fungus (yellow) so tightly that despite violent thrashing it cannot escape.

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* Predation (포식) Fig. 13 Predator-Prey Interactions. Theoretical cycles of population sizes of a predator and its prey species.

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* Parasitism (기생) The parasite population is benefited and the host population is harmed. The host-parasite relationship is typically quite specific. Some bacteria are parasites of other bacteria. Bdellovibrio is parasitic on other bacterial populations and is able to invade and multiply by binary fission within cells of E. coli.

37 Population Interactions
* Parasitism (기생) Fig. 14 Parasitism by Bdellovibrio. Colorized micrographs showing Bdellovibrio entering an Escherichia coli cell and reproducing within the periplamic space.


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