ecology PART 2 2015-2016.pptx

7/24/2019 ecology PART 2 2015-2016.pptx

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MICROBIAL

INTERACTIONS


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Mutualism

Some reciprocal benefit to both

partners

Relationship with some degree of

obligation

often partners cannot live separately mutualistand host are dependent on

each other


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Examples

Lichensthe association between specific fungui and

certain genera of either green algae orcyanobacteria.

mycobiont fungal partner

provides water, minerals, protectedenvironment and firm substratum for

growth phycobiont

alga or cyanobacterium

provides organic carbon and oxygen


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Figure 30.14


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Mycorrhizae

represent a mutualisticsymbiosis between the root

system of higher plants andfungal hyphae.

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Advantages

. !he fungus derives nutrients via the root of the

plant. Sugars formed in the leaves move down the

stem as sucrose

". !he fungal hyphae act li#e a massive root hair

system, scavenging minerals from the soil andsupplying them to the plant.

$. %ecause of this associationship the plant partner, in

addition to the nutritional benefits, develops

drought resistance, tolerance to p& andtemperature extremes, and greater resistance to

pathogens due to 'phytoalexins( released by the

fungus.8


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)ctotrophic Mycorrhiza


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)ndotrophic Mycorrhiza


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Syntrophism growth of one organism depends on or is improved

by growth factors, nutrients, or substrates providedby another organism growing nearby also called crossfeeding

is also defined as a mutualistic interrelationship

between two different microorganisms whichtogether degrade some substances *and conserveenergy doing it+ that neither could degradeseparately. n most cases of syntrophism the nature of a

syntrophic reaction involves &"gas beingproduced by one partner and being consumed bythe other.

!hus, Syntrophy has also been called interspecies

hydrogen transfer.


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Example

Anaerobic methanogenic ecosystems

fatty acids catabolized by anaerobic bacteria

*e.g.,Syntrophobacter+, producing &"

methanogen *e.g.,Methanospirillum+ uses &"

for methanogenesis


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protocooperation

%enefits both organisms inrelationship

-iffers from mutualism becauseprotocooperative relationship is notobligatory

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)xamples of protocooperation


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Nocardiapopulation metabolizescyclohexane resulting in degradation

products that are used by

Pseudomonaspopulation. !hepseudomonasspecies produce biotin

and growth factors that are reuiredfor the growth of /ocardia.


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0ommensalism

1ne organism benefits and the

other is neither harmed nor

helped 0ommensal is the organism that

benefits


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Examples of Commensalism

. the waste product of one microorganism is the

substrate for another species. An example is

nitrification

/&$/1" /1$/itrification carried out by two different

bacteria

e.g.,Nitrosomonas carries out first step

e.g.,Nitrobactercarries out second step *i.e., it

benefits from its association withNitrosomonas+


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". 0an also involve modification of

environment by one organism, ma#ing

it more suited for another organism

. 2or example, when facultative anaerobes

utilize oxygen and lower the oxygen

content, they create anaerobic habitatwhich favor the growth of obligate

anaerobes because the latter benefit from

the metabolic activities of the facultativeanaerobes in such a habitat. , such as the

oral cavity and human intestine, is

dependent on such commensal relationship.18


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$. 0ommensalism also is important in the

colonization of the human body.

. 2or example, A disease causingmicrobial population when a lesion on

the surface, it creates an entry3passage

for other microbial population thatotherwise could not enter and grow in

the host tissues. 2or convenience,

Mycobacterium leprae, the causative agent

of leprosy, open lesions on the body3

surface and thus allow other pathogens to

establish secondary infections.

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ecology PART 2 2015-2016.pptx

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