Populations,guilds,and communities-an example of microbial community structure in
a lake ecosystem,(a) Microbial guilds consist of populations of cells of various species
that arise ecosystem,For simplicity,only three microbial communities are
chemoorganotrophic,aerobic chemmorganotrophic,and anaerobic,In the anaerobe
community,examples of guild structure are given.
Microbial population interactions
Mutualism
Symbiosis is an obligatory interrelationship
between two populations that benefits both of
them,
Lichens is composed of a fungus and an alga.
Basic Structure of a Hydrothermal Vent with its
Mutualistic Microbe-Animal Associations.
Protocooperation
Protocooperation is a mutually beneficial
relationship,similar to that which occurs in
mutualism,but in protocooperation,this relationship
is not obligatory,Beneficial complementary
resources are provided by each of the paired
microorganisms,The organisms involved in this
type of relationship can be separated,and if the
resources provided by the complementary
microorganism are supplied in the growth
environment,each microorganism will function
independently,
Example of
Protocoope-
rative
Symbiotic
Processes
Commensalism is a unidirectional relationship
between populations in which one population
benefits and the other one is unaffected.
Predation
? Predation is a widespread phenomenon where the
predator engulfs of attacks the prey,The prey can be
larger or smaller than the predator,and this normally
results in the death of the prey.
Example of Predatory
Bacterial Found in Nature.
(a) Bdellovibrio,a
periplasmic predator that
penetrates the cell wall and
grows outside the plasma
membrane
(b) Vampirococcus with its
unique epibiotic mode of
attacking a prey bacterium,
(c) Daptobacter showing
its cytoplasmic location as
it attacks a susceptible
bacterium
Parasitism,the parasite population is
benefited and the host population is harmed.
Amensalism
? Amensalism describes
the negative effect that
one organism has on
another organism,
? Antibiotic production
and inhibition of
growth of a
susceptible bacterium
on an agar medium.
Competition occurs when two populations are
striving for the same resource of nutrients or
the habitat.
Symbioses in Complex Systems
It should be emphasized that symbiotic interactions
discussed in this section do not occur independently,
Each time a microorganism interacts with other
organisms and their environments,a series of
feedback responses occurs in the larger biotic
community that will impact other parts of
ecosymtems.
Complex Interaction in
Microbial Ecology
Biogeochemical cycles
1,Carbon cycle
2,Nitrogen cycle
3,Sulfur cycle
4,Iron cycle
Macrobiogeochemistry,A Cosmic View of Mineral Cycling in
Microorganisms,Higher Organisms,and the Abiotic Chemical World
The Basic Carbon Cycle in the Environment.
The Influence of
Oxygen on
Organic Matter
Decomposition
Carbon dioxide is incorporated,or fixed,into organic
compounds by such photoautotrophs as cyanobacteria,green
plants,algae,and green and purple sulfur bacteria,
Chemoheterotrophs consume the organic compounds,animals
eat photoautotrophs,especially green plants,and may in turn
be eaten by other animals,
When the organisms die,the organic compounds of their bodies
are deposited in the soil and are decomposed by microorganisms,
principally by bacteria and fungi,During this decomposition,
carbon dioxide is returned to the atmosphere,
The Basic Nitrogen Cycle,Flows that occur predominantly
under aerobic conditions are noted with open arrows,Anaerobic processes are noted with solid
bold arrows,Processes occurring under both aerobic and anaerobic conditions are marked with
cross-barred arrows,The anammox reaction of NO2- and NH4+ to yield N2 is shown,Important
genera contributing to the nitrogen cycle are given as examples,
Proteins from
dead cells and
waste products
Microbial
decomposition Amino
acids
Amino
acids
Ammonia
(NH3)
ammonification
Almost all the nitrogen in the soil exists in organic molecules,primarily in
proteins,When an organism dies,the process of microbial decomposition
results in the hydrolytic breakdown of proteins into amino acids.
The amino groups of amino acids are removed and converted into ammonia
(NH3),Ammonification is brought about by numerous bacteria and fungi.
NH4+ N02-Nitrosomonas
Ammonium ion Nitrite ion
N02- N03-
Nitrite ion Nitrate ion
Nitrobacter
Nitrification involves the oxidation of the ammonium ion to nitrate
The genera Nitrosomonas and Nitrobacter are autotrophic
nitrifying bacteria,These organisms obtain energy by oxidizing
ammonia or nitrite,In the first stage,Nitrosomonas oxidizes
ammonium to nitrites,In the second stage,such organisms as
Nitrobacter oxidize nitrites to nitrates
Key processes and prokaryotes in the nitrogen cycle
Processes Example organisms
Nitrification(NH4+→NO 3-)
NH4+→NO 2- Nitrosomonas
NO2-→NO 3- Nitrobacter
Denitrification(NO3-→N 2) Bacillus,Pseudomonas
N2 Fixation(N2+8H → NH 3 +H2)
Free-living
Aerobic Azotobacter
Cyanobacteria
Anaerobic Clostridium,purple green bacteria
Symbiotic Rhizobium
Bradyrhizobium,Frankia
Ammonification(organic-N → NH 4+)
Many organisms can do this
Photosynthetic and chemosynthetic
microorganisms contribute to the
environmental sulfur cycle,Sulfate
and sulfite reductions carried out by
desulfovibrio and related
microorganisms,noted with purple
arrows,are dissimilatory processes,
Sulfate reduction also can occur in
assimilatory reactions,resulting in
organic sulfur forms,Elemental
sulfur reduction to sulfide is carried
out by desulfuromonas,
thermophilic archaea,or
cyanobacteria in hypersaline
sediments,Sulfur oxidation can be
carried out by a wide range of
aerobic chemotrophs and by aerobic
and anaerobic phototrophs.
The Basic Sulfur Cycle
Key processes and prokaryotes in the sulfur cycle
Processes Organisms
Sulfide/sulfur oxidation(H2S→S 0 → SO42-)
Aerobic Sulfur chemolithotrophs
(Thiobacillus,Beggiatoa,many others)
Anaerobic Purple and green phototrophic
bacteria,some chemolithotrophs
Sulfate reduction(anaerobic)(SO42- → H 2S)
Desulfovibrio,Desulfobacter
Sulfur reduction(anaerobic) (S0 → H 2S)
Desulfuromonas,many
hyperthermophilic Archaea
Sulfur disproportionation(S2O32- → H 2S + SO42-)
Desulfovibrio and others
Organic sulfur compound oxidation or reduction(CH3SH→CO 2+ H2S)
(DMSO→DMS)
Desulfurylation(organic-S → H 2S)
Many organisms can do this
The Basic Iron Cycle,A simplified iron cycle with examples of
microorganisms contributing to these oxidation and reduction processes,In addition to these
oxidation and reduction processes,In addition to ferrous ion (Fe2+) oxidation and ferric ion (Fe3+)
reduction,magnetite (Fe3O4),a mixed valence iron compound formed by magnetotactic bacteria
is important in the iron cycle,Different microbial groups carry out the oxidation of ferrous ion
depending on environmental conditions.
1,Microorganisms are an important part of ecosystems
2,Microbial communities are complex
3,Microbial growth requires nutrients and all of which
must be present in usable forms
4,Most microorganisms normally associated with higher
organisms and those grown in the lab,tend to be less able
to compete and survive in soils and waters
5,Extreme environments restrict the range of microbial
types which are able to survive and function
Concepts
Microorganisms and Ecosystems
Microorganisms thus carry out many important function as they
interact in ecosystems,including:
1,Contributing to the formation of organic matter through
photosynthetic and chemosynthetic process.
2,Decomposing organic matter,often with the release of inorganic
compounds (e.g.,CO2,NH4+,CH4,H2) in mineralization processes.
3,Serving as a nutrient-rich food source for other chemoheterotrophic
microorganisms,including protozoa and animals.
4,Modifying substrates and nutrients used in symbiotic growth processes
and interactions,thus contributing to biogeochemical cycling.
5,Changing the amounts of materials in soluble and gaseous forms,This
occurs either directly by metabolic processes or indirectly by
modifying the environment.
6,Producing inhibitory compounds that decreases microbial activity or
limit the survival and functioning of plants and animals.
7,Contributing to the functioning of plants and animals through positive
and negative symbiotic interactions.
The Vital Role of Microorganisms in Ecosystems.
Microorganisms play vital roles in ecosystems as primary producers,decomposers,and
primary consumers.
A simple Ecosystem,An alga,which releases photosynthetically generated oxygen
and organic matter to its environment,is surrounded by chemoheterotophs that are
using these products of primary production,These two types of microorganisms,
producing and consuming oxygen and organic matter,form a self-regulating
ecosystem (× 1,000).
Stress and Ecosystems
microorganisms function in ecosystems that develop
under a wide range of environmental conditions,
These have varied pHs,temperatures,pressures,
salinity,water availability,and ionizing radiation,
Such stress factors have major effects on microbial
populations and communities,and can create an
extreme environment.
Microorganisms Growing in Extreme
Environment
Salterns truned red by halophilic
alage and halobacteria
a lake ecosystem,(a) Microbial guilds consist of populations of cells of various species
that arise ecosystem,For simplicity,only three microbial communities are
chemoorganotrophic,aerobic chemmorganotrophic,and anaerobic,In the anaerobe
community,examples of guild structure are given.
Microbial population interactions
Mutualism
Symbiosis is an obligatory interrelationship
between two populations that benefits both of
them,
Lichens is composed of a fungus and an alga.
Basic Structure of a Hydrothermal Vent with its
Mutualistic Microbe-Animal Associations.
Protocooperation
Protocooperation is a mutually beneficial
relationship,similar to that which occurs in
mutualism,but in protocooperation,this relationship
is not obligatory,Beneficial complementary
resources are provided by each of the paired
microorganisms,The organisms involved in this
type of relationship can be separated,and if the
resources provided by the complementary
microorganism are supplied in the growth
environment,each microorganism will function
independently,
Example of
Protocoope-
rative
Symbiotic
Processes
Commensalism is a unidirectional relationship
between populations in which one population
benefits and the other one is unaffected.
Predation
? Predation is a widespread phenomenon where the
predator engulfs of attacks the prey,The prey can be
larger or smaller than the predator,and this normally
results in the death of the prey.
Example of Predatory
Bacterial Found in Nature.
(a) Bdellovibrio,a
periplasmic predator that
penetrates the cell wall and
grows outside the plasma
membrane
(b) Vampirococcus with its
unique epibiotic mode of
attacking a prey bacterium,
(c) Daptobacter showing
its cytoplasmic location as
it attacks a susceptible
bacterium
Parasitism,the parasite population is
benefited and the host population is harmed.
Amensalism
? Amensalism describes
the negative effect that
one organism has on
another organism,
? Antibiotic production
and inhibition of
growth of a
susceptible bacterium
on an agar medium.
Competition occurs when two populations are
striving for the same resource of nutrients or
the habitat.
Symbioses in Complex Systems
It should be emphasized that symbiotic interactions
discussed in this section do not occur independently,
Each time a microorganism interacts with other
organisms and their environments,a series of
feedback responses occurs in the larger biotic
community that will impact other parts of
ecosymtems.
Complex Interaction in
Microbial Ecology
Biogeochemical cycles
1,Carbon cycle
2,Nitrogen cycle
3,Sulfur cycle
4,Iron cycle
Macrobiogeochemistry,A Cosmic View of Mineral Cycling in
Microorganisms,Higher Organisms,and the Abiotic Chemical World
The Basic Carbon Cycle in the Environment.
The Influence of
Oxygen on
Organic Matter
Decomposition
Carbon dioxide is incorporated,or fixed,into organic
compounds by such photoautotrophs as cyanobacteria,green
plants,algae,and green and purple sulfur bacteria,
Chemoheterotrophs consume the organic compounds,animals
eat photoautotrophs,especially green plants,and may in turn
be eaten by other animals,
When the organisms die,the organic compounds of their bodies
are deposited in the soil and are decomposed by microorganisms,
principally by bacteria and fungi,During this decomposition,
carbon dioxide is returned to the atmosphere,
The Basic Nitrogen Cycle,Flows that occur predominantly
under aerobic conditions are noted with open arrows,Anaerobic processes are noted with solid
bold arrows,Processes occurring under both aerobic and anaerobic conditions are marked with
cross-barred arrows,The anammox reaction of NO2- and NH4+ to yield N2 is shown,Important
genera contributing to the nitrogen cycle are given as examples,
Proteins from
dead cells and
waste products
Microbial
decomposition Amino
acids
Amino
acids
Ammonia
(NH3)
ammonification
Almost all the nitrogen in the soil exists in organic molecules,primarily in
proteins,When an organism dies,the process of microbial decomposition
results in the hydrolytic breakdown of proteins into amino acids.
The amino groups of amino acids are removed and converted into ammonia
(NH3),Ammonification is brought about by numerous bacteria and fungi.
NH4+ N02-Nitrosomonas
Ammonium ion Nitrite ion
N02- N03-
Nitrite ion Nitrate ion
Nitrobacter
Nitrification involves the oxidation of the ammonium ion to nitrate
The genera Nitrosomonas and Nitrobacter are autotrophic
nitrifying bacteria,These organisms obtain energy by oxidizing
ammonia or nitrite,In the first stage,Nitrosomonas oxidizes
ammonium to nitrites,In the second stage,such organisms as
Nitrobacter oxidize nitrites to nitrates
Key processes and prokaryotes in the nitrogen cycle
Processes Example organisms
Nitrification(NH4+→NO 3-)
NH4+→NO 2- Nitrosomonas
NO2-→NO 3- Nitrobacter
Denitrification(NO3-→N 2) Bacillus,Pseudomonas
N2 Fixation(N2+8H → NH 3 +H2)
Free-living
Aerobic Azotobacter
Cyanobacteria
Anaerobic Clostridium,purple green bacteria
Symbiotic Rhizobium
Bradyrhizobium,Frankia
Ammonification(organic-N → NH 4+)
Many organisms can do this
Photosynthetic and chemosynthetic
microorganisms contribute to the
environmental sulfur cycle,Sulfate
and sulfite reductions carried out by
desulfovibrio and related
microorganisms,noted with purple
arrows,are dissimilatory processes,
Sulfate reduction also can occur in
assimilatory reactions,resulting in
organic sulfur forms,Elemental
sulfur reduction to sulfide is carried
out by desulfuromonas,
thermophilic archaea,or
cyanobacteria in hypersaline
sediments,Sulfur oxidation can be
carried out by a wide range of
aerobic chemotrophs and by aerobic
and anaerobic phototrophs.
The Basic Sulfur Cycle
Key processes and prokaryotes in the sulfur cycle
Processes Organisms
Sulfide/sulfur oxidation(H2S→S 0 → SO42-)
Aerobic Sulfur chemolithotrophs
(Thiobacillus,Beggiatoa,many others)
Anaerobic Purple and green phototrophic
bacteria,some chemolithotrophs
Sulfate reduction(anaerobic)(SO42- → H 2S)
Desulfovibrio,Desulfobacter
Sulfur reduction(anaerobic) (S0 → H 2S)
Desulfuromonas,many
hyperthermophilic Archaea
Sulfur disproportionation(S2O32- → H 2S + SO42-)
Desulfovibrio and others
Organic sulfur compound oxidation or reduction(CH3SH→CO 2+ H2S)
(DMSO→DMS)
Desulfurylation(organic-S → H 2S)
Many organisms can do this
The Basic Iron Cycle,A simplified iron cycle with examples of
microorganisms contributing to these oxidation and reduction processes,In addition to these
oxidation and reduction processes,In addition to ferrous ion (Fe2+) oxidation and ferric ion (Fe3+)
reduction,magnetite (Fe3O4),a mixed valence iron compound formed by magnetotactic bacteria
is important in the iron cycle,Different microbial groups carry out the oxidation of ferrous ion
depending on environmental conditions.
1,Microorganisms are an important part of ecosystems
2,Microbial communities are complex
3,Microbial growth requires nutrients and all of which
must be present in usable forms
4,Most microorganisms normally associated with higher
organisms and those grown in the lab,tend to be less able
to compete and survive in soils and waters
5,Extreme environments restrict the range of microbial
types which are able to survive and function
Concepts
Microorganisms and Ecosystems
Microorganisms thus carry out many important function as they
interact in ecosystems,including:
1,Contributing to the formation of organic matter through
photosynthetic and chemosynthetic process.
2,Decomposing organic matter,often with the release of inorganic
compounds (e.g.,CO2,NH4+,CH4,H2) in mineralization processes.
3,Serving as a nutrient-rich food source for other chemoheterotrophic
microorganisms,including protozoa and animals.
4,Modifying substrates and nutrients used in symbiotic growth processes
and interactions,thus contributing to biogeochemical cycling.
5,Changing the amounts of materials in soluble and gaseous forms,This
occurs either directly by metabolic processes or indirectly by
modifying the environment.
6,Producing inhibitory compounds that decreases microbial activity or
limit the survival and functioning of plants and animals.
7,Contributing to the functioning of plants and animals through positive
and negative symbiotic interactions.
The Vital Role of Microorganisms in Ecosystems.
Microorganisms play vital roles in ecosystems as primary producers,decomposers,and
primary consumers.
A simple Ecosystem,An alga,which releases photosynthetically generated oxygen
and organic matter to its environment,is surrounded by chemoheterotophs that are
using these products of primary production,These two types of microorganisms,
producing and consuming oxygen and organic matter,form a self-regulating
ecosystem (× 1,000).
Stress and Ecosystems
microorganisms function in ecosystems that develop
under a wide range of environmental conditions,
These have varied pHs,temperatures,pressures,
salinity,water availability,and ionizing radiation,
Such stress factors have major effects on microbial
populations and communities,and can create an
extreme environment.
Microorganisms Growing in Extreme
Environment
Salterns truned red by halophilic
alage and halobacteria
