Methanotrophs are unique bacteria that use methane as their sole carbon and energy source. They play several important roles in the environment. First, they oxidize methane produced by archaea, reducing the amount of this potent greenhouse gas that enters the atmosphere. Second, they can degrade various organic pollutants using monooxygenase enzymes. Finally, they can remediate heavy metals by transforming more toxic forms into less toxic forms or facilitating precipitation. Methanotrophs thus aid in carbon and pollutant cycling while also helping to mitigate climate change.
1. ROLE OF METHANOTROPHS IN
ECOSYSTEM
PRESENTED BY:
Mousami Jaria
St. George College of Management
and Science
MSc Microbiology
Semester 2
2. INTRODUCTION
• Methanotrophs are unique and ubiquitous
bacteria that utilize methane as a sole source
of carbon and energy from the atmosphere.
• They can also be targeted for bioremediation
of diverse type of heavy metals and organic
pollutants owing to the presence of
monooxygenases enzyme.
• They are highly specialized group of aerobic
bacteria.
3. • Have a unique capacity for oxidation of
certain organic pollutants like alkanes,
halogenated alkanes , aromatics etc.
• They oxidize much of the methane produced
by the anaerobic metabolism of metanogenic
archaea before it escapes to the atmosphere
thereby lessening the effects of global
warming.
• Found in freshwater, marine environments,
soils, sediments, rice paddies, hot springs,
cold as well as thermophillic environments.
4. ROLE IN ECOSYSTEM
CARBON FIXATION PATHWAYS:
• Aerobic methanotrophs are prokaryotes that
grow by oxidation of methane
• They are included among broader class of
aerobes called methylotrophs which oxidize
C1 compounds such as
methanol,methylamine, carbin monoxide ,
dimethylsulfide.
5. • Two broad groups of methanotrophs are
recognized: 1. Methylococcaceae
2. Methylocystaceae
1. Methylococcaceae:
• Located within gamma subdivision
• There are two recognised subgroups :
a. Type 1 : mostly mesophiles and
psychrophiles, and they branch closely to
number of methane oxidizing endosymbionts.
b. Type X : contain thermotolerant and
thermophilic members.
6. 2. Methylocystaceae: located within the alpha
subdivision of proteobacteria.
STEPS:
• All aerobic methanotophs are united in the
methane oxidation involving the oxidation of
methane to methanol with the enz. Methane
monooxygenase and the conversion of methanol
to formaldehyde
• ALL type 1 and type X methanotrophs use
ribulose monophosphate pathway(RuMP) for
carbon assimilation.
7. • All cell carbon is assimilated from
formaldehyde .
• Three formaldehydes are incorporated into
three ribulose-5-phosphate molecule ,
forming three molecules of hexulose-6-
phosphate .
• 1 ATP molecule is used for every 3 molecules
of formaldehyde assimilated.
• 3 molecules of formaldehyde ultimately forms
1 molecule of glyceraldehyde-3-phosphate
which is channeled into biosynthesis.
9. • The serine pathway is used by type 2
methanotrophs.
• In this pathway both formaldehyde and CO2
are incorporated to form acetyl Co A, some of which
are directed to biosynthesis.
• The initial step in the process is incorporation of
formaldehyde into glycine , forming serine
• Later CO 2 is incorporated into phosphophenol
pyruvate , which is converted into oxaloacetate
• This pathway requires the utilization of 2 ATP and 2
NADH foe each molecule of acetyl Co A formed.
10.
11.
12. REMEDIATION OF HAZARDOUS ORGANIC
POLLUTANTS:
• Methanotrophs synthesize both particulate
and soluble forms of methane
monooxygenases ( pMMO and sMMO), which
can co metabolize diverse type of
hydrocarbons and halogenated organic
compounds including aromatics.
• Priority pollutants like trichloroethylene (TCE)
can be easily degraded by application of
methanotrophs
13. • The sMMO expressing methanotrophs due to
their relatively broad substrate range and fast
turnover kinetics , exhibit fast decline in level
of pollutants
• The sMMO is capable of oxidizing a wider
range of organic compounds like aliphatic,
aromatic hydrocarbons.
• Biodegradation of chlorinated hydrocarbons
by methanotrophs occurs in an oxidative
manner they do not accumulate hazardous
intermediates.
14. REMEDIATION OF HEAVY METALS:
• Methanotrophs influence the speciation and
bioavailability of metals in environment.
• Methylococcus capsulatus transforms more
toxic Cr(IV) into less toxic Cr(III) as Cr(III) is
insoluble and tends to get precipitated at high
pH .
• The toxic mercury(II) ion is usually detoxified
by bacteria via its reduction to elemental
mercury catalysed by enz. mercury reductase.
15. • Thus methanotrophs mot only degrade
moiety but also aid in remediaton of inorganic
elements.
16.
17. MODEL SHOWING ROLE OF METHANOTROPHIC
BACTERIA FOR ENVIRONMENTAL REMEDIATION
18. CONCLUSION
• With the combination of biotechnology and
genetic engineering , methanotrophs can be
exploited for in situ bioremediation of a wide
range of inorganic and organic pollutants.
