Microbial Function on Climate Change – A Review

Greenhouse gases concentration is increased through time within different human and natural factors. Such as combustion of coal, oil and other fossil fuels, decay of plant matter and biomass burning. Now a day’s climate change and global warming is the major problem in the world. It is damage (destroy) a number of biotic componets. It have also effect on microbial comunity stracture, function and their metablolic activity. In order to fi ght (compromize) climate change using a number of methods are listed here. For example, microorganisms and other biological componets have many potential role for mitigation by contribute forward response. Microorganisms have a wide function especialy used in greenhouse gas treatment and reduction through nutrient recycling processes. It act as either generators or users of these gases in a good manner. It provide to reduce environment hazards which is caused by nature and antropogenic activity. In overall biogeochemical cycles and climate changes are never see separately. Review Article Microbial Function on Climate Change – A Review Endeshaw Abatenh*, Birhanu Gizaw, Zerihun Tsegaye and Genene Tefera Endeshaw Abatenh, Ethiopia Biodiversity Institute, Department of Microbiology, Comoros Street, 0000, Addis Ababa, Ethiopia Received: 14 March, 2018 Accepted: 28 April, 2018 Published: 30 April, 2018 *Corresponding author: Endeshaw Abatenh, Ethiopia Biodiversity Institute, Department of Microbiology, Comoros Street, 0000, Addis Ababa, Ethiopia, E-mail: Endeshewab@gmail.com


Introduction
The super challenges of the 21 st century are climate change, energy supply, health and diseases, and sustainable environment. These are hot topic today. World climate change is hot right now, intensely discussed by politicians, businessman, environmentalist, society and mass media. Microorganisms and biogeochemical cycles are the two faces for one coin. It is takes place inside oceans, soil, open and closed environment. Both are facilitate the way of making and using greenhouse gases. Microorganisms provide long and short term encouragement and discouragement feedback responses to global warming as well as climate change [1]. Microbes play an important role as either generators or users of these gases in the environment as they are able to recycle and transform the essential elements such as carbon and nitrogen that make up cells [2,3]. Biological method to control greenhouse gas emissions is invaluable regarding to nutrients recycling. Microbial diversity in different ecosystem have many contribution in climate change controlling and fi ghting its negative impacts due to their metabolism is amazingly versatile and they can grow in a broad environmental conditions. Microorganisms are perform uptake, storage and realese of gases easly. The aim of the review is to answer what is the role of microbes playing in helping to fi ght climate change and greenhouse gas redaction? How will that role involve in future within mitigation option?

Climate change
Climate is defi ned as general or average weather conditions of a certain region, including temperature, rainfall, and wind. Climate system is a complex, interactive system consisting of the atmosphere, land surface, snow and ice, oceans and other bodies of water, and living things. The earth's climate is most affected by latitude, the tilt of the Earth's axis, the movements of the Earth's wind belts, the difference in temperatures of land and sea, and also topography. The Earth is surrounded by a thick layer of gases which keeps the planet warm and allows plants, animals and microbes to live. These gases work like a blanket. Without this blanket the Earth would be 20-30°C colder and much less suitable for life. Due to the degree of temperature increase all over the world then climate change become happened. This is causing the Earth to heat up, which is called global warming. Global warming is termed as an increase in temperature of the Earth's atmosphere in amount over a period of time. The blanket of gases that surrounds the Earth is getting much thicker. These gases are trapping more heat in the atmosphere causing the planet to warm up. Green House effect is the phenomenon whereby the earth's atmosphere traps solar radiation, and is mediated by the presence in the atmosphere of gases such as carbon dioxide, water vapor, and methane that allow incoming sunlight to pass through, but absorb the heat radiated back from the earth's surface. This is provide a blanketing effect in the lower strata of the earth's atmosphere, and this blanketing effect is being enhanced because of the human activities like burning of fossil fuels [4,5].

Causes of climate change
Greenhouse gases emission is increased dramatically in DOI: http://dx.doi.org/10.17352/ojeb.000008 recent years due to human activity and natural factors like volcanic eruption. These gases accumulate in the atmosphere and causing concentrations to increase within time. Signifi cant increases in all of these gases have occurred in the industrial era. The major green house gases are carbon dioxide, methane, nitrous oxide and halocarbons.
1. Carbon dioxide is came from fossil fuel use in different sectors like transpor tation, building, heating, cooling and the manufacture of cement and other goods. It is also released from natural processes such as the decay of plant matter, respiration and microbial decomposition of organic matter [6]. It also turn out in deforestation program.
2. Methane production is result of anthropogenic day to day activities resemble to fossil fuels production, distribution and combustion, landfi lls and waste, livestock farming, biomass burning and rice agriculture. Natural processes that occur in wetland termites and oceans are unique sources for methane emissions [1].
3. Nitrous oxide is occurred during fertil izer use and fossil fuel burning. In another hand, naturally in soil and ocean also released [7].
4. Halocarbon gases quantity is increased primarily due to human and natural processes. Halocarbons are contained chlorofl uorocarbons (CFC-11 and CFC-12) which were used extensively as refrig eration agents and in other industrial processes before their presence in the atmosphere was found to cause stratospheric ozone depletion. Nowadays, the abundance of chlorofl uorocarbon gases is decreasing as a result of international regulations designed to protect the ozone layer.

5.
Ozone is a greenhouse gas that is continually produced and destroyed in the atmosphere by chemical reactions.
In the tro posphere, human activities have increased ozone through the release of gases such as carbon monoxide, hydrocarbons and nitrogen oxide, which chemically react to produce ozone. As mentioned above, halocarbons released by human activities destroy ozone in the stratosphere and have caused the ozone hole over Antarctica.  Effi ciency of soil microorganisms in using carbon determines the soil carbon response to climate change [16][17][18][19].

Effects of climate change on microorganisms
Microbial community composition, abundance, and function is altered when microbes are exposed to new extremes' in environmental condition; that is environmental change or global warming/climatic disturbance has an effect on microbial ecology, ecosystem structure, and function. Moreover, signifi cant changes also happen through over time in their functional genes and traits. This kind of effect/infl uence occurs under on each biogeochemical cycle. [41,42]. factors. The potential to mitigate climate change by reducing greenhouse gas emissions through managing terrestrial microbial processes is a tantalizing prospect for the future. It is widely accepted that microorganisms have played a key part in determining the atmospheric concentrations of greenhouse gases [1,20]. The major feedback response mechanism for climate change by changing their microbial community structure and composition solve this kind of environmental problem. Simply, by using nutrient cycling processes and stimulating their functional genetic material for degrading and eliminating chemicals or gasses which leads to global warming [21]. When microbial communities and biogeochemical cycles are linked together act as a good mechanism to solve climate change. Microorganisms are very important to use greenhouse gases as energy source and build their cell [1].

Microbial communities and carbon cycle
The global carbon cycle is mainly depend on microbial communities that fi x atmospheric carbon, promote plant growth, and degrade or transform organic material in the environment. Large amounts of organic carbon are currently locked in high latitude permafrost, grassland soils, tropical forests and other ecosystems. In another hand, microorganisms play key role in determining the longevity and stability of this carbon and whether or not it is released into the atmosphere as greenhouse gas which means mediate the processes of carbon cycle [12]. Microorganisms are slow down global warming and implications for crucial ecological processes such as nutrient cycling which rely on microbial activity. Microorganisms are critical in the process of breaking down and transforming dead organic material into forms that can be reused by other organisms. This is why the microbial enzyme systems involved are viewed as key 'engines' that drive the Earth's biogeochemical cycles. The terrestrial carbon cycle is dominated by the balance between photosynthesis and respiration. Carbon is transferred from the atmosphere to soil via 'carbon-fi xing' autotrophic organisms such as photosynthesizing plants, photo and chemoautotrophic microorganisms these are synthesis atmospheric carbon dioxide in to organic material. Practically, microorganisms use carbon for their metabolism substrate due to these highly consume atmospheric carbon dioxide (Figure 1).
Soil microorganisms essential for transfer carbon between environmental compartments to fulfi l their fundamental goal mainly to achieve survival through reproduction. Thus, microbes utilize different organic and inorganic forms of carbon as carbon and energy sources. The terrestrial carbon cycle is dominated by the balance between photosynthesis and respiration [22][23][24]. Carbon is also found in the earth's crust, primarily as limestone and kerogens. Chemoautotrophic is an organism obtaining its nutrition through the oxidation of non-organic compounds (or other chemical processes); as opposed to the process of photosynthesis. Carbon in the earth's atmosphere exists in two main forms: carbon dioxide and methane. Carbon dioxide is dissolve directly from atmosphere in to water bodies. In addition to this, dissolving in precipitation as raindrops fall through the atmosphere. When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid which is contribute to ocean acidity.
Microorganisms are part of a larger cycling of carbon that occurs on the global scale. The actions of microorganisms help extract carbon from non-living sources and make the carbon is available to living organisms (including themselves). Much of the carbon that enters the carbon cycle is carbon dioxide. This form of carbon exists as a gas in the atmosphere, but before it can be incorporated into living organisms it must be transformed in to usable organic form. The transformative process by which carbon dioxide is taken up from the atmospheric reservoir and "fi xed" into organic substances is called carbon fi xation. The best known example of carbon fi xation is photosynthesis, a process by which energy derived from sunlight is harnessed to form organic compounds. Photosynthetic algae are important microorganisms in this regard and chemoautotrophs are mentioned. Primarily, bacteria and archae are capable of carbon dioxide conversion in to sugar form available for cell building. Some organic carbon is returned to the atmosphere as CO 2 form during respiration. The rest of the organic carbon may cycle from organism to organism through in food chain. When an organism dies, it is decomposed by bacteria and its carbon is released into the atmosphere or the soil. CO 2 dissolves in the water at that time algae, plants and bacteria convert into organic carbon. Carbon may transfer between organisms from producers to consumers. Their tissues are ultimately broken down by bacteria and CO 2 is released back into the ocean or atmosphere [20,25].
The cycling of carbon by variety of bacteria and fungi species occurs in aquatic habitats. Even relatively oxygenfree zones such as in the deep mud of lakes, ponds and other water bodies can be regions where the anaerobic conversion of carbon takes place. Both types of conversion take place in the presence and the absence of oxygen. Algal involvement is an aerobic process. In anaerobic environments, microorganisms can cycle the carbon compounds to yield energy in a process known as fermentation. Other microorganisms are able to participate in the cycling of carbon. For example, green and purple sulfur bacteria are able to use the energy they gain from the degradation of a compound called hydrogen sulfi de to degrade carbon compounds. Other bacteria such as Thiobacillus ferrooxidans uses the energy gained from the removal of an  [8,29]. Microorganisms are used high amount of methane compounds which is found at everywhere [30].
In anaerobic conditions just like deep compacted mud, carbon dioxide easily changed in to methane this is accomplished by methanogenic bacteria. The conversion process needs hydrogen, yields water and energy for the methanogens. To accomplish the recycling pattern another group of methane bacteria called methaneoxidizing bacteria or methanotrophs (literally "methane eaters") can convert methane to carbon dioxide. This conversion, which is an aerobic process, also yields water and energy. In the presence of oxygen, CH 4 is oxidized to CO 2 by methanotrophic bacteria. The oxidation of CH 4 to CO 2 completes the carbon cycle. Methanotrophs tend to live at the boundary between aerobic and anaerobic environments.
They have access to the methane produced by the anaerobic methanogenic bacteria, but also access to the oxygen needed for their conversion of the methane [31]. ). Other bacterial species such as Nitrobacter, are responsible for the oxidation of the nitrites into nitrates (NO 3 − ). Ammonia is converted to nitrates or nitrites because ammonia gas is toxic to plants. Ammonium ion useful in energy source microorganisms involved in side the system. Nitrite is toxic to plant and animal. It must be immediately convert in to nitrate by different species [32,[36][37][38].

Assimilation:
This step indicate that the mechanism of plants get nitrogen. Plants can uptake nitrates from soil by their root hairs. Eventually, it is used in cellular component production like amino acids, nucleic acids, and chlorophyll. In plants that have a symbiotic relationship with rhizobia, some nitrogen is assimilated in the form of ammonium ions directly from the nodules. Other life form also seeking nitrogen through food chain structure [39].

4.
Ammonifi cation: is the stage of decaying. During living things are died, decomposers like fungi and bacteria turn nitrogen to ammonium. Later it can reenter in the normal nitrogen cycle. In the N 2 process the nitrogen is released usually in the form of ammonia. The process is termed as ammonifi cation or mineralization. Many types of enzymes are involved for example Gln Synthetase (Cytosolic & Plastid), Glu 2-oxoglutarate aminotransferase (Ferredoxin & NADH dependent) and Glu Dehydrogenase. Actually in soil this takes the form of the ammonium ion (NH 4 +) which has a positive charge. This charge tends to bind the nitrogen to clay minerals of the soil, an advantage in that the nitrogen is not readily lost by leaching or runoff. It has the disadvantage that it cannot easily migrate to reach plant roots for uptake [32,39].

5.
Denitrifi cation: at the end of cycle extra nitrogen molecule in the soil move out to atmosphere. Denitrifi cation is the reduction of nitrates back into the largely inert nitrogen gas (N 2 ) for completing cycle. This kind of task is performed by special and unique group of bacteria like Pseudomonas and Clostridium. They use nitrate as an electron acceptor in the place of oxygen during respiration. The denitrifying bacteria use nitrates in the soil to carry out respiration and consequently produce nitrogen gas, which is inert and unavailable to plants. The process is takes place in the absence of oxygen commonly in waterlogged soils. Eventually, nitrate is converted to nitrogen gas and reenter to atmosphere [32,40].
Other mitigation options used for solving climate change 1. Less chemical consumption on farms through a reduced need to spray crops.
2. Minimize introducing synthetic chemical fertilizer in agriculture and using plant promoting microorganisms which act as a biofertilizer in a form of bio inoculation.
Finally, can easily stop GHSs emission.
3. Avoiding the use of fossils raw materials and fuel (wood) through replacement the use of enzymes and microorganisms helps to make bio based products in adverse variety of industry sectors.
4. Using biofuel and apply bio based strategies and targets. For example, bioethanol. Biofuels are made from living things or the waste that they produce. One of the most common biofuels is ethanol, it is produced from plants.
As a result biofuels from food stuffs such as sugar cane are not likely to provide a long term solution as a replacement to fossil fuels. The sugar can then be fermented (broken down) to ethanol by microbes such as the yeast Saccharomyces cerevisiae, Sulfolobus solfataricus and Trichoderma reesei.
5. Using potential bio based chemicals and plastics because of can replace their fossil based counter parts with signifi cant and proven in greenhouse gases emission reduction.
6. Introducing novel species in the ecosystem 7. Improving drought tolerance biotic organisms 8. Minimizing and reducing water loss from agriculture 9. Applying afforestation program all over the world. Then carbon sequestration can easily managed 10. Creating public awareness and bring together to save nature and protect ecosystem

Conclusion
Generally, microorganisms through nutrient cycling act as a break down organic matter release greenhouse gases and speed up global climate change. In another side, it minimize or compromise the emission of different gases and slow down (prevent) climate change by converting to organic form usable for themselves and others. In ecological processes microbes have signifi cant value in consumption (transformation) and production of gases. Biological mechanism are regulate carbon and nitrogen exchanges between the land, water and atmosphere. Microbial ecology to assess terrestrial carbon cycle play important role for balance ecosystem and stabilize atmospheric condition. Methylotrophs can use greenhouse gases as substrates to fulfi ll their energy and carbon needs. Greenhouse gases are moving forward to atmosphere during respiration (breathing), decay and combustion (burning). Nature also by itself does a great job of balancing carbon and nitrogen with in biogeochemical nutrient cycling.

Recommendation
For best clarity further scientifi c investigation on how microorganisms use and produce GHGs will respond to climate change should be conducted.