Role of micro-organisms in climate change

Role of micro-organisms in climate

change

ANURAG SAHA ENVB40090: Essay (MSc Applied Science)

Student No.: 13201125 Year: 2013-14

Role of micro-organisms in climate change

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Introduction

Global warming affects all of us, the more we learn about the nuts and bolts about global

warming, the better the chance we have of doing something about it. The Earth's getting

warmer; the intergovernmental panel on climate change (IPCC) that synthesizes climate

change research says that most of the warming they have seen is due to human activities

(IPCC, 2007). We won't be able to say how much more warming is going to happen and one

of the missing pieces is how ecosystems will respond to climate change.

Without the greenhouse effect, the earth would be a frozen ball in space. While the

majority of the atmosphere is oxygen and nitrogen, a small fraction consists of greenhouse

gases such as, carbon dioxide, methane and nitrous oxide, as well as other trace gases.

Water is also a significant greenhouse gas (fig.1). The greenhouse effect works like a blanket

around the earth by trapping heat radiated off the surface of the planet. It's the same as

putting on extra blankets or clothing. By doing so, more heat is trapped inside the layers.

Since the beginning of the industrial age nitrous oxide (N2O) has increased by 18%, carbon

dioxide (CO2) from fossil fuel combustion by 39%, and methane (CH4) up to 148%

(Friedlingstein et al., 2006). This warming is also increasing the temperature of the ocean,

which evaporates more water.

Figure 1: Left - Naturally occurring greenhouse gases—carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)—normally trap some of the sun’s heat, keeping the planet from freezing. Right - Human activities, such as the burning of fossil fuels, are increasing greenhouse gas levels, leading to an enhanced greenhouse effect. The result is global warming and unprecedented rates of climate change (Elder, 2014).

Biogeochemical cycles are defined as the

pathways for the transport and transformation

of matter within categorical areas that make up

the planet Earth, i.e., biosphere, hydrosphere,

lithosphere, and atmosphere (Moses, 2012).

They may involve gas or sedimentary cycles;

with some cycles being both gas and sediment.

In gas cycles, elements move through the

atmosphere whereas in sedimentary cycles,

elements move from land to water to sediment.

From a climate change perspective the two

most important cycles are the carbon and

nitrogen cycles, which are interconnected

(fig.2). Figure 2: The two major biogeochemical cycles (Sultzman, 2008).


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Micro-organisms play a central role in nutrient cycling in the environment. In soil systems

they mediate decay of plant matter, consumption and production of trace gases,

transformation of metals and plant growth (Panikov, 1999). Through these roles

microorganisms have the potential to impact climate; and due to their vast numbers and

widespread distribution they have immense effect at a global scale. Soil micro-organisms

contribute significantly to the production and consumption of greenhouse gases, including

carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and nitric oxide (NO), and human

activities such as waste disposal and agriculture have stimulated the production of

greenhouse gases by microbes (fig.3). As concentrations of these gases continue to rise, soil

microbes may have various feedback responses that accelerate or slow down global

warming, but the extent of these effects are unknown (Madison et al.2009).

Figure 3: Showing the inter-relationship between the two major biogeochemical cycles, i.e., Carbon and Nitrogen cycles occurring simultaneously on the Earth (Lester, 2007).

Microbial ecology and metabolic diversity go hand in hand. By understanding the role of soil

microbes which have both contributors to and reactive components of climate change can

help us determine whether they can be used to curb emissions or if they will push us even

faster towards climatic disaster.

This essay is concerned with the role of microorganisms in climate change with particular

reference to their carbon and nitrogen cycling activities. We will see how micro-organisms

and their metabolic reactions play key roles in maintaining the web of life on Earth and are

of crucial importance for supporting different aspects of climatic conditions and their

variable changes.


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Micro-organisms and Carbon Cycle

The carbon cycle describes the fluxes of carbon among various reservoirs in the Earth

system. Carbon (C) is the fourth most abundant element in the universe after the Hydrogen

(H), Helium (He) and Oxygen (O). It is the building block of all life-on Earth, and plays crucial

roles in the climate system, climate change and energy resources on which humanity is most

dependent.

When organisms die they decompose or rot. This is largely brought about through the

actions of bacteria and fungi. These and other so-called decomposers feed on dead

organisms using some of the carbon in the dead tissues for growth, with the remaining

carbon in the dead organism returned back to the atmosphere as the carbon dioxide which

is a by-product of the decomposers' own respiration. Green plants of all kinds can then use

these newly freed carbon atoms during photosynthesis.

Figure 4: Left – Interaction between autotrophs and heterotrophs in any carbon cycle (Tsaile, 1986). Right – The CO2 incorporates into carbohydrate by fluxes (Copyrights 2012 © Biocyclopedia.com).

Living organisms are connected between ecosystems in many ways. A prominent example

will be the exchange of carbon between autotrophs and heterotrophs within and between

various ecosystems by way of atmospheric carbon dioxide (fig.4, left). It is the CO2 which is

considered as the building block that autotrophs use to build multi-carbon, high-energy

compounds, such as glucose.

Among various autotrophs, like the plants, photosynthetic bacteria, algae, lithotrophs, and

some methanogens, uses CO2 as the sole source of carbon for growth. This reduces the

molecule to organic cell material (CH2O). Even heterotrophs require organic carbon for

growth and ultimately convert it back to CO2 (fig.4, right).


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Thus, a relationship is established between autotrophs and heterotrophs wherein

autotrophs fix carbon needed by heterotrophs and heterotrophs produce CO2 used by the

autotrophs.

CO2 + H2O CH2O (organic material) autotrophy

CH2O + O2 CO2 + H2O heterotrophy

Since CO2 is the most prevalent greenhouse gas in the atmosphere, it would not be good if

the two equations get out of balance (i.e. heterotrophy predominating over autotrophy, e.g.

rain forests are destroyed and replaced with cattle).

Key groups of organisms:-

Carbon dioxide fixation.

Fermentation and anaerobic respiration.

Methanogenesis and methanogenic archaea.

Methane oxidation and methylotrophic bacteria.

Carbon cycles are floating around in the form of reservoirs, pools, storage sites, sinks and

sources. There are certain series of fluxes which may be utilized as transfer or processes.

These carbon sources and fluxes are dependent on each other and plays significant role to

the various carbon cycles occurring on the earth. Mainly three key fluxes are part important.

Photosynthesis is the basic chemical process in plants, algae, and phytoplankton. In this

chemically simplest form, it looks like this:

Energy (sunlight) + 6CO2 + 6H2O C6H12O6 + 6O2 (C6H12O6 is a generic carbohydrate)

Plants use solar radiation, carbon dioxide (CO2) from the atmosphere, and water (H2O), and

they produce carbohydrates and release oxygen into the atmosphere. Animals then eat

those carbohydrates and breathe that oxygen.

Respiration is the process in which animals acquire oxygen from the atmosphere, and

release carbon dioxide into the atmosphere.

Combustion is the burning of organic matter in the presence of oxygen. Oxygen-free

conditions prevent combustion. In its chemically simplest form, combustion looks like this:

CH4 + O2 CO2 + H2O + energy (heat)

In a slightly more complex, but still simple form:

C6H12O6 + 6O2 6CO2 + 6H2O + energy (heat)

The organic molecules in these equations (CH4 and C6H12O6) could be wood, paper, plastic,

cloth or any fossil fuel (coal, oil, natural gas). It could also be food for an animal, which is

known as metabolism instead of combustion. Whatever the fuel, it is burned along with

oxygen to produce energy and water, and to release carbon dioxide to the atmosphere.


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Autotrophs, being the primary producers, are always at the bottom of the food chain. They

are responsible for converting CO2 to a form required by the heterotrophs. Among

prokaryotes, the cyanobacteria, the lithotrophs and the methanogens are the formidable

biomass of autotrophs that account for a corresponding amount of CO2 fixation in the global

carbon cycle.

The lithotrophic bacteria and archaea oxidizes reduced nitrogen (N) and Sulphur (S)

compounds (Yahai and Conrad, 2005). All these autotrophs play important roles in the

natural cycles of N and S. These organisms are prevalent in sulphur-rich environments like,

hot springs, marine sediments, thermal vents, endosymbionts, etc. This may indicate an

unfavourable role to these prokaryotes as primary producers of organic carbon on earth.

The methanogens significantly play a dual role in the carbon cycle. The archaea are

inhabitants for all these anaerobic environments where CO2 and H2 occur naturally (Del et

al. 2002). They use these CO2 in their metabolism in two different ways. During autotrophic

growth, around 5% of CO2 taken up is reduced to cell material and the remaining 95% is

reduced to CH4 gas during a unique process of generating cellular energy (Arrigo, 2005).

Thus, the CH4 which accumulates in the rocks as fossil fuels (natural gas), in the rumen of

cows and guts of termites, swamps, sediments, landfills and sewage digesters.

CO2 + H2 CH2O (cell material) + CH4 methanogenesis

CH4 is the second most prevalent of the

greenhouse gases. It is best to

discourage the processes that lead to

its accumulation in the atmosphere. In

aerobic conditions, the CH4 and its

derivatives (methanol, formaldehyde,

etc.) can be oxidized as energy sources

by bacteria called methylotrophs. This

is a metabolic version of decomposition

or biodegradation during the carbon

cycle (fig.5).

In the carbon cycle, the microbes are

responsible for the process of

Biodegradation. It is the decomposition

of organic material (CH2O) back to

carbon dioxide (CO2), water (H2O) and

hydrogen (H2).

For soil habitats, the fungi play a

significant role in biodegradation, but the

prokaryotes are equally important

(Allison et al. 2010).

Figure 5: Redox cycle for carbon. The diagram contrasts autotrophic processes (CO2 organic compounds) and heterotrophic processes (organic compounds CO2). Yellow arrows indicate oxidation while the red arrows represent reduction (Copyrights 2012 © Suman Bhattacherjee, Retrieved from http://shomusbiology.weebly.com/).

http://shomusbiology.weebly.com/


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Typically the decomposition scenario involves the initial degradation of biopolymers (like,

cellulose, lignin, proteins and polysaccharides) by extracellular enzymes, followed by

oxidation (fermentation or respiration) of the monomeric subunits (Kirschbaum, 2004). The

ultimate end products are CO2, H2O and H2, perhaps with some amount of ammonia (NH3)

and sulphide (H2S). This depends on how the overall process is viewed (fig.6). The products

formed are scarfed up by lithotrophs and autotrophs for recycling (Schimel and Gulledge,

1998). In nature, the prokaryotes play a vital role in biodegradation which include the

actinomycetes, clostridia, bacilli, arthrobacters and pseudomonads.

Polymers (e.g. cellulose) monomers (e.g. glucose) depolymerisation

Monomers fatty acids (e.g. lactic acid, etc.) + CO2 + H2 fermentation

Monomers + O2 CO2 + H2O aerobic respiration

Figure 6: Diagrammatic representation of the carbon fixation in a carbon cycle through Aerobic and Anaerobic processes by various levels of decomposers (Copyrights 2007 © MicrobiologyBytes).

As the methanogens have the potential to remove CO2 from the atmosphere, by converting

it to cell material and CH4. These prokaryotes not influenced by the carbon cycle but by their

metabolism also affect the concentration of major greenhouse gases in earth’s atmosphere

(Toder, 2009). According to Prof. Paul Weimer (University of Wisconsin-Madison)

methanogenesis which utilizes CO2 for producing CH4 has a worse greenhouse effect.


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Prof. Paul clearly stated, “For methanogenesis by CO2 reduction, the stoichiometry is

4H2 + CO2 CH4 + 2H2O, so one mole of a greenhouse gas is exchanged for another. But

CH4 is about 15 times more potent than is CO2 in terms of heat absorption capability on a

per-molecule basis, so the net effect is a functional increase in heat absorption by the

atmosphere. Remember also that in most natural environments, around two-thirds of the

CH4 is produced by aceticlastic methanogenesis (CH3COOH CH4 + CO2) – an even less

welcome situation, as both products are greenhouse gases. Even though CH4 concentrations

in the atmosphere are two orders of magnitude below those CO2, methane is thought to

account for about 15% of the anthropogenic climate forcing, compared to about 60% from

CO2. Most of the rest of the contribution is from nitrous oxide (N2O, a respiratory

denitrification product that has something like 300 times the heat absorbing capacity as

CO2) and the old chlorofluorocarbons (CFCs), even stronger heat absorbers yet, but more

famous and dangerous as stratospheric ozone-depleters.”

There are a myriad of ways by which the soil microbes and their metabolic activity can

influence land-atmosphere carbon exchanges. These can be broadly divided into those that

affect ecosystem CO2 and CH4 uptake and control carbon loss from soil through respiration

and CH4 production (Bardgett et al. 2008). The sensitivity of stable and labile fractions of soil

organic carbon to temperature change is thought to vary greatly (Singh et al. 2010).

Micro-organisms and Nitrogen Cycle

Nitrogen is one of the primary nutrients critical for the survival of all living organisms

(Bernhard, 2012). Although it is abundant in the atmosphere, it is highly inaccessible to most

organisms in this form. It is one of the major components for many biomolecules, including

amino acids, proteins and nucleic acids, DNA and chlorophyll. It is a crucial plant nutrient.

Although nitrogen is abundant in the atmosphere in the form of dinitrogen gas (N2), but it is

highly inaccessible in this form to most organisms (Bernhard, 2012). This makes nitrogen a

very scarce resource and often limiting primary productivity in many ecosystems. It

becomes available to primary producers (such as plants), only when this gas is converted

from dinitrogen gas into ammonia.

Nitrogen exists in many different forms, including both inorganic (e.g., ammonia, nitrate)

and organic (e.g., amino and nucleic acids) forms. Thus, nitrogen undergoes into different

transformations in the ecosystem. This change is from one form to another as organisms

use it for growth as well as for energy. Nitrogen when applied to soil undergoes

transformation processes before becoming available for plants. The major transformations

of nitrogen are involved through nitrogen fixation, nitrification, denitrification, anammox

and ammonification (fig.6). The transformation of N2 into various oxidation states is the key

to productivity in the biosphere. This is highly dependent on the activities of a diverse

assemblage of microbes, such as bacteria, archaea and fungi.


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Figure 6: Major transformations in the Nitrogen cycle (Copyrights 2010 © Nature Education).

The key groups of microbes:-

Nitrification and Nitrosomonas, Nitrobacter, etc.

Denitrification.

Nitrogen fixation, detection by acetylene reduction.

Rhizobium and symbiotic associations etc - free living nitrogen fixation.

The plants absorb the nitrate ions and form vegetable proteins from them by nitrate

assimilation. The plants can also use ammonium ions (NH4+). Animals excrete nitrogenous

waste materials, such as urea, uric acid, ammonia. Urea and uric acid are converted into

ammonium compounds and CO2 by the putrefying bacteria (Bacillus ramosus and B.

vulgaris) are some fungi found in the soil and in the mud bottom of water bodies. They also

decompose the nitrogenous compounds (proteins) of the dead animals and plants into NH4+

compounds.

Some NH4+ compounds, nitrites (NO2

-) and nitrates (NO3-) are converted by bacteria and

fungi into molecular nitrogen (N2) which escapes into atmosphere or is added to water, and

is lost from the cycle. The process is called denitrification. The bacterium Pseudomonas

aeruginosa reduces nitrates to molecular nitrogen. Other denitrifying bacteria are

Micrococcus denitrificans and Thiobacillum denitrificans.

NO3- NO2

- N2 (denitrification)


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Most of the NH4+ compounds formed by the putrefying bacteria and fungi are oxidized by

the nitrite bacteria (Nitrosomonas and Nitrococcus) to soluble nitrites, which are further

oxidized by nitrate bacteria (Nitrobacter and Nitrocystis) and fungi to soluble nitrates. The

process of nitrate formation is known as nitrification, and the bacteria responsible for it as

the nitrifying bacteria. The nitrates so formed are added to the soil and water, thus

completing the cycle (fig.7).

Figure 7: Schematic

representation of the

flow of nitrogen

through the

environment. The

importance of bacteria

in the cycle is

immediately

recognized as being a

key element in the

cycle, providing

different forms of

nitrogen compounds

assimilable by higher

organisms (Copyrights

2009 © United States

Environmental

Protection Agency).

Free living Nitrogen fixing bacteria:-

a. Obligate anaerobes, e.g. Clostridium pasteurianum b. Facultative anaerobes, e.g., Klebsiella spp., a close relative of E. coli. c. Photosynthetic bacteria, e.g. Rhodobacter spp. d. Many cyanobacteria, e.g. Nostoc spp. e. Obligate aerobes such as Azotobacter f. Some methanogens Since nitrogenase is inactivated by O2, the fixation of N must occur under conditions which

are anaerobic at least locally. For anaerobes there is no problem. Facultative organisms

such as purple photosynthetic bacteria or Klesbsiella spp. fix nitrogen only when anaerobic.

Other organisms have protective mechanisms.

In Azotobacter, an obligate aerobe, the O2 concentration inside the cell is held down by

partial uncoupling of a highly active respiratory chain. This wastes carbohydrate, but if

growth is limited by absence of nitrogen compounds then this is justifiable. The

cyanobacteria in O2 are actually generated by photosynthesis. Fixation of N occurs in special

cells known as heterocysts which do not photosynthesize but are devoted solely to N2

fixation.


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In root nodules, the O2 level is regulated by special haemoglobin – leghaemoglobin. The

globin protein is encoded by plant genes but the heme cofactor is made by the symbiotic

bacteria. This is produced only when the plant is infected with Rhizobium. The plant root

cells convert sugar to organic acids which they supply to the bacteroids. In exchange, the

plant receives amino-acids (rather than free NH3).

The overall process of Nitrification

2NH4+ + 3O2 Nitrosomonas 2NO2

- + 4H+ + 2H2O

2NO2- + O2 Nitrobacter

2NO3-

2NH4+ + 2O2 Nitrifiers NO3

- + 2H+ + H2O

An important aspect of the nitrogen cycle that involves prokaryotes, though not exclusively,

is decomposition of N-containing compounds. Mostly, the organic N (in the form of protein)

yields NH3 during the process of deamination. Fungi are involved in decomposition as well.

The plants, animals and protista, even prokaryotes, completes the nitrogen cycle during the

uptake of the element for their own nutrition. Usually the N assimilation is usually in the

form of NO3-, an amino group or NH3.

Moreover, the rate of denitrification of NO3- in soil is dependent on various factors such as

the pH, temperature and H2O content in the soil. With the increased rise in soil pH, there is

a high acceleration of denitrification which turns to a higher adverse when the pH level rises

to 8.0 – 8.6 (Bremner & Shaw, 1958). Similarly, denitrification increases when temperature

rises from 2o to 25oC, the optimum temperature is about 60oC.

The degree of water saturation of the soil has a profound influence on the rate of

denitrification. No denitrification is occurs below a certain moisture level, but above this

level, denitrification increases rapidly with the increase in moisture content. The critical

moisture level is about 60% of the water-holding capacity of the soil (Bremner & Shaw,

1958). A prominent example to withstand this critical moisture level can be water-logging.

In the overall reactions of denitrification, formation of N2O is involved. According to a recent

article by Wunsch in Zumft (Journal of Bacteriology, vol. 187 [2005]), highlights some new

facts on the process of denitrification. It explains that N2O is a bacterial metabolite in the

reversal of Nitrogen fixation. The atmospheric increase of N2O due to anthropogenic

activities is a cause for concern. This greenhouse gas (N2O) has 300 times the heat absorbing

capacity as CO2. Denitrifying bacteria respire using N2O as an electron acceptor yielding N2

and thereby provide sink for N2O.

Transformations of fertilizer nitrogen in the soil

Nitrogen when applied to soil undergoes transformation processes before becoming

available for plants. The following two different sources of nitrogen explain the soil nitrogen

cycle;


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Nitrogen transformations when applying Ammonium Nitrate

1. Application of fertilizers, containing mineral nitrogen as ammonium and nitrate. Organic

fertilizers contain mostly complex forms of N and NH4+.

2. Uptake of nitrate is rapid due to the high particle mobility. Most plants therefore prefer

nitrate over NH4+.

3. Uptake of ammonium is slower than that of NO3-. NH4

+ is bound to clay particles in the

soil and roots have to reach it. Most of the NH4+ is therefore nitrified before it is taken-up by

plants.

4. Nitrification by soil bacteria converts NH4+ into NO3

- in between a few days and a few

weeks. N2O and NO are lost to the atmosphere during the process.

5. Denitrification is favoured by lack of O2 (e.g. water logging). Soil bacteria converts NO3-

and NO2- into gaseous N2O, NO and N. These are lost to the atmosphere.

6. Immobilization transforms mineral N into soil organic matter. Activity of soil microbes is

mainly stimulated by NH4+. Immobilized N is not immediately available for plant uptake, but

needs to be mineralized first. Mineralization of soil organic matter (and manure) releases

NH4+ into the soil.

7. Ammonia volatilization occurs when NH4+ is converted to NH3 and lost to the

atmosphere. A high soil pH level and temperature favour conversion of NH4+ to NH3. If

conversion takes place at the soil surface, losses are highest.

8. Leaching of NO3- occurs mainly during winter and fallow periods when percolating rainfall

washes residual and mineralized NO3- below the root zone. Accurate fertilization increases N

use efficiency and reduces the risk of leaching during the growth period and afterwards.

Nitrogen transformations when applying Urea

1. Application of fertilizers, containing mineral N as urea. Organic fertilizers contain mostly

complex forms of N and NH4+.

2. Hydrolysis of urea by soil enzymes converts urea into ammonium and CO2 gas. Depending

on temperature, hydrolysis takes a day to a week. The soil pH around the urea granules

strongly increases during this process, favouring NH3 volatilization.

3. Ammonia volatilization occurs when NH4+ is converted to NH3 and lost to the

atmosphere. A high soil pH level and temperature favour conversion of NH4+ to NH3. If

conversion takes place at the soil surface, losses are highest. These conditions are met when

urea is spread and not immediately incorporated.

4. Nitrification, by soil bacteria converts NH4+ into NO3

- in between a few days and a few

weeks. N2O and NO are lost to the atmosphere during the process.


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5. Uptake of nitrate is rapid due to high particle mobility. Most plants therefore prefer NO3-

over NH4+.

6. Uptake of ammonium is slower than that of nitrate. NH4+ is bound to clay particles in the

soil and roots have to reach it. Most of the NH4+ is therefore nitrified before it is taken-up by

plants.

7. Denitrification is favoured by lack of oxygen (e.g. water logging). Soil bacteria convert

NO3- and NO2

- into gaseous NO, N2O and N. These are lost to the atmosphere.

8. Immobilization transforms mineral N into soil organic matter. Activity of soil microbes is

mainly stimulated by NH4+. Immobilized N is not immediately available for plant uptake, but

needs to be mineralized first. Mineralization of soil organic matter releases NH4+ into soil.

9. Leaching of NO3- occurs mainly during winter and fallow periods when percolating rainfall

washes residual and mineralized nitrates below the root zone. Accurate fertilization

increases N use efficiency and reduces the risk of leaching during the growth period and

afterwards.

Ammonium Nitrate is taken-up directly by plants while urea first needs to be converted.

Ammonium Nitrate therefore offers higher N use efficiency than urea. Ammonium Nitrate

thus reduces losses and environmental impact.

Figure 8: Nitrogen undergoes transformations in the soil depending on the chemical composition of the nitrogen applied (Copyrights 2011 © Yara International, Norway).

The major human activities that today influence the global N cycle are fossil fuel

combustion, the production and use of chemical fertilizer, and the growing of N-fixing crops.

These activities are reported to have doubled the magnitude of N fixation over continents.

The major environmental issues associated with this enhancement are global climate

change, stratospheric ozone depletion, regional smog, visibility degradation, acid rain,

water-use impairment, and eutrophication.


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Conclusion

The complexity of the soil microbial community and its pivotal roles, coupled with the

myriad of ways that climate and other global changes can affect soil microbes to hamper the

ability to draw firm conclusions on this topic.

There are many alterations by microbes to their ecosystems. Indeed, soil microbes are

extremely diverse and one of the greatest challenges that concerns our understanding

about how microbial diversity responds to climate change. Even with the presence of huge

amount of N2 in the worldwide nitrogen cycle, it has side effects on the climates through

these microbial activities (Wagner, 2013).

People have been causing these biogeochemical cycles to change (UCAR, 2011). These are

influenced by various anthropogenic activities caused by human interferences; cutting down

of forests, building more factories, and even drive more automobiles that burn higher

quantity of fossil fuels (UCAR, 2011). This is the way that both carbon and nitrogen move

around the Earth changes. All these change add more greenhouse gases in the atmosphere

and this cause climate change.

Humankind has only relatively recently started to alter the composition of the atmosphere

and the energy balance of the planet, micro-organisms have been dictating the global

climate change for billions of years (Udakis, 2013). As microbes play an important role as

both users and producers of greenhouse gases, it cannot be ignored. Both natural and

human-induced fluxes of carbon dioxide, methane and nitrous oxide are dominated by

microbiology (Udakis, 2013).

Research has already found that due to global warming, bacteria and fungi reproduce more

rapidly (Agren, 2013). At the same time, they even use a larger share of the available carbon

for their own respiration, bringing more CO2 into the atmosphere which stimulates

atmospheric warming even more (Agren, 2013). This is how micro-organisms are believed to

contribute to global climate change.

Both in the carbon and nitrogen cycles there are certain levels of complex metabolic

activities which are influenced by inorganic nutrients (Six et al., 2006). These activities are

quite vigorous and fluent but will tend to alter if there is change within the surrounding

environment. This may result in vehement effects and impacts on global climatic

phenomena leading to change in its natural occurrences.

The average global surface temperature is predicted to increase by between 1.1 and 6.4oC

by 2100 (IPCC, 2007) and this might also have an effect on soil carbon and nitrogen

sequences by potentially accelerating heterotrophic microbial activity.

Attempts have been made to incorporate various data on microbial diversity, community

structure and physiological capabilities of various taxa. These microbial responses can be

understood only after the framework on management of the microbial systems for reduced

greenhouse gas emission is developed.


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Role of micro-organisms in climate change

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