On the earth where human beings thrive, most species are affected by climate change. Microbes support the existence of all life forms in higher education. In order to understand how human beings and other life forms on the earth (including life forms that we have not yet discovered) resist man-made climate change, it is very important to understand microorganisms. We should not only understand how microorganisms affect climate change (including the generation and consumption of greenhouse gases), but also understand.
Core role and its global importance. It reminds people that the impact of climate change will largely depend on the response of microorganisms, and the response of microorganisms is very important to realize the future of environmental sustainable development.
Paper ID
Original name: scientists' warning to mankind: microorganisms and climate change.
Scientists' warning to mankind: microorganisms and climate change
Journal of Nature Review Microbiology
If: 34.648
DOI:https://DOI . org/ 10. 1038/s 4 1579-0 19-0222-5
Release date: 20 19
Correspondence author: Ricardo Cavicioli
Author: University of New South Wales.
The article is quoted 186 times a year, which shows the importance and influence of the period.
Abstract content
2 marine biota
Marine life accounts for 70% of the earth's surface, from coastal estuaries, mangroves and coral reefs to the high seas (figure 1). Temperature rise will not only affect biological processes, but also reduce the density of water, leading to stratification and circulation, thus affecting the diffusion of organisms and the transportation of nutrients. Precipitation, salinity and wind also affect stratification, mixing and circulation. Nutrient input from air, rivers and estuaries will also affect the composition and function of microorganisms, and climate change will affect all these physical factors.
In addition to a large number of marine microorganisms, the marine environment also plays an important ecosystem function. Marine microorganisms mineralize organic matter by fixing carbon and nitrogen, forming the foundation of marine food web and global carbon and nitrogen cycle. The deposition of carbon in particulate organic matter and its fixation in marine sediments are the key long-term mechanism for storing CO 2 in the atmosphere. Therefore, climate change is determined by the balance between mineralization and the release of carbon and nitrogen stored on the seabed. In addition to warming (the increase of CO 2 concentration in the atmosphere leads to the enhancement of greenhouse effect), the marine environment has been acidified by about 0. 1 pH unit since pre-industrialization, and it is expected to further decrease by 0.3-0.4 units by the end of this century. Therefore, it is necessary to understand how marine life will respond. The effects of rising greenhouse gas concentration on ocean temperature, acidification, stratification, mixing, temperature-salt cycle, nutrient supply, radiation and extreme weather events will have a major environmental impact on marine microbial flora, including productivity, marine food webs, carbon emissions and seabed fixation.
2. 1 Microbes affect climate change
Marine phytoplankton only accounts for 1% of global plant biomass, but it has completed half of global photosynthesis (CO2 fixation and OO 2 production). Compared with terrestrial plants, marine phytoplankton is more widely distributed, less affected by seasonal changes and faster in turnover. Therefore, phytoplankton respond quickly to climate change on a global scale. The increase of solar radiation, temperature and fresh water input into surface water strengthens ocean stratification, thus reducing the transport of nutrients from deep water to surface water and reducing primary productivity. On the contrary, the increase of CO 2 content can increase the primary productivity of phytoplankton without the limitation of nutrients Some studies show that the overall density of marine phytoplankton in the world has decreased in the past century, but these conclusions need further study due to limited data collection and differences in analysis methods. Some studies have also found that the increase of global marine phytoplankton production is related to the changes of specific areas or specific phytoplankton groups. The reduction of global sea ice area leads to higher light transmittance and potential more primary productivity; However, there are contradictions in the forecasting effect of variable mixing model, nutrient supply change and productivity trend in polar regions. This emphasizes the necessity of collecting long-term data on phytoplankton yield and microbial community composition.
In addition to the contribution of marine phytoplankton to CO 2 fixation, chemoautotrophic archaea and bacteria can also fix CO 2 on the surface in deep water and dark conditions and polar winter Methane-producing bacteria and methane-oxidizing bacteria on the seabed are important producers and consumers of CH 4, but their influence on the atmospheric flux of this greenhouse gas is uncertain. Marine viruses, bacteria-loving bacteria and eukaryotic herbivores are also important components of microbial food webs. The impact of climate change on predator-prey interaction, including virus-host interaction, can affect the global biogeochemical cycle.
Aerosols affect the formation of clouds, thus affecting sunlight and precipitation, but the extent and manner of their impact on climate are still uncertain. Marine aerosol consists of a complex mixture of sea salt, non-sea salt sulfate and organic molecules, which can be used as cloud condensation nuclei, affecting radiation balance and thus affecting climate. Understanding the contribution of marine phytoplankton to aerosols can better predict how the changing marine environment will affect clouds and feedback to climate. In addition, the atmosphere itself contains about 10 22 microbial cells, so it is of great value to determine the ability of atmospheric microorganisms to grow and form aggregates for evaluating their impact on climate.
Coastal habitats where plants grow are of great significance for carbon sequestration. In the past 50 years, human activities, including man-made climate change, have reduced these habitats by 25-50% and the number of marine carnivores by 90%. According to the activities of microorganisms, how much carbon is remineralized and released into CO2 and CHCH 4, and considering such extensive environmental disturbances, the impacts of these disturbances on microbial communities need to be further evaluated.
2.2 the impact of climate change on microorganisms
Climate change destroys the interaction between species, forcing species to adapt, migrate or be replaced or extinct by other species. Ocean warming, acidification, eutrophication and overuse (such as fishing and tourism) will lead to the decline of coral reefs and may lead to changes in ecosystems. Generally speaking, microorganisms are easier to disperse than macro organisms. However, there are biogeographic differences in many microbial species, and diffusion, lifestyle and environmental factors strongly affect community composition and function. Ocean acidification makes the pH conditions of marine microorganisms far beyond their historical range, thus affecting the intracellular pH level. Species that are not good at adjusting the pH in the body will be more affected, and many environmental and physiological factors will affect the reaction and overall competitiveness of microorganisms in their local environment. For example, higher temperature will increase the protein synthesis of eukaryotic phytoplankton and decrease the cell ribosome concentration. Because the biomass of eukaryotic phytoplankton is ~ 1 Gt C and ribosomes are rich in phosphate, the change of nitrogen-phosphorus ratio caused by climate change will affect the global ocean resource allocation. Ocean warming is considered to be beneficial to smaller plankton rather than larger plankton, which changes biogeochemical flux. The increase of ocean temperature, acidification and the decrease of nutrient supply are expected to increase the release of dissolved organic matter in phytoplankton cells. The change of microbial food network may lead to the increase of microbial yield, but at the cost of higher nutrient level. The temperature increase can also alleviate the limitation of iron on nitrogen-fixing cyanobacteria, which has a potential far-reaching impact on the new nitrogen source provided by the future warming marine food web. It is necessary to pay attention to how to quantify and explain the response of environmental microorganisms to the pressures related to ecosystem changes and climate change. Therefore, the key issues are still about the functional consequences of flora transfer, such as changes in carbon remineralization and carbon sequestration, and their relationship with nutrient cycling.
3 terrestrial organisms
The terrestrial biomass is 100 times of the marine biomass, of which land plants accounts for about half of the global net primary productivity. Soil stores about 2 trillion tons of organic carbon, which is much higher than the sum of carbon in the atmosphere and vegetation. The total number of microorganisms in terrestrial environment is similar to that in marine environment. Soil microorganisms regulate the amount of organic carbon stored in soil and released into the atmosphere, and indirectly affect the carbon storage in plants and soil by providing various nutrients that regulate productivity.
Plants absorb CO 2 in the atmosphere through photosynthesis and produce organic matter; On the contrary, autotrophic respiration of plants and heterotrophic respiration of microorganisms release CO 2 back into the atmosphere. Temperature affects the dynamic balance between these processes, thus affecting the ability of terrestrial biosphere to capture and store man-made carbon emissions (Figure 1). Climate warming may accelerate carbon emissions. Forests cover 30% of the land area, accounting for 50% of the land primary productivity, and the man-made CO 2 sequestration rate is as high as 25%. The accumulation of organic carbon in permafrost far exceeds the loss of respiration, creating the largest terrestrial carbon sink. However, due to climate warming, it is expected that the permafrost will be reduced by 28-53%, so that large carbon pools can be used for microbial respiration and greenhouse gas emission.
By comparing and evaluating the profiles of surface soil (100 cm) and deep soil (100cm), it is found that climate warming will increase carbon emissions into the atmosphere. Further explaining the difference of carbon loss between different soil sites requires more predictive variables. However, the prediction from the global warming response assessment shows that under the condition of global warming, the loss of terrestrial carbon produces positive feedback, which accelerates the pace of climate change, especially in cold and temperate regions (which store most of the global soil carbon).
3. 1 Effects of microorganisms on climate change
The increase of CO 2 content improves the primary productivity, increases the content of plant litter and promotes the decomposition of litter by microorganisms, which leads to the increase of carbon emissions. The influence of temperature is not only the dynamic effect of microbial reaction rate, but also the result of plant input to stimulate microbial growth. Some inherent environmental factors (such as microbial community composition, dead wood density, nitrogen availability and water content) affect microbial activities, so it is necessary to predict soil carbon loss caused by climate warming through the earth system model to control ecosystem processes. In this respect, the availability of plant nutrients affects the net carbon balance of forests. Malnourished forests release more carbon than nutrient-rich forests. Plants release about 50% of fixed carbon into the soil for microbial growth. Secretion can not only be used as energy by microorganisms, but also destroy the combination of minerals and organisms, release organic compounds from minerals used by microorganisms, and increase carbon emissions. The correlation of these plant-mineral interactions shows that in addition to biological interaction (plant-microorganism), biological-abiotic interaction is also very important in evaluating the impact of climate change.
Whether soil organic matter is used for microbial degradation or long-term storage depends on many environmental factors, including soil mineral characteristics, acidity, redox state, water availability, climate and so on. The nature of organic matter, especially the complexity of matrix, will also affect the decomposition of microorganisms. In addition, the ability of microorganisms to obtain organic matter is different with different soil types. If availability is considered, it is expected that the increase of CO 2 content in the atmosphere will promote the decomposition ability of microorganisms, thus reducing the retention of organic carbon in soil. The increase of carbon dioxide concentration enhances the competition for nitrogen between plants and microorganisms. Herbivores will affect the content of organic matter in soil, thus affecting the biomass and activity of microorganisms. Climate change can reduce herbivores, lead to the overall change of global nitrogen cycle and carbon cycle, and thus reduce the fixation of terrestrial carbon. Harmful animals (such as earthworms) affect greenhouse gas emissions by indirectly affecting plants (such as increasing soil fertility) and soil microorganisms. The anaerobic environment in earthworm intestines contains microorganisms that perform denitrification and produce NO2. Earthworms can improve soil fertility, and their existence can lead to net greenhouse gas emissions, although the combined effects of rising temperature and decreasing rainfall on pest feeding and microbial respiration may reduce emissions.
In peatland, rot-resistant litter can inhibit microbial decomposition, while water saturation limits the exchange of oxygen, promotes the growth of anaerobic bacteria, and releases CO2 and CHCH 4. Changes in plant litter composition and related microbial processes (for example, reducing nitrogen fixation and enhancing heterotrophic respiration) are transforming peat land from carbon sink to carbon source. The melting of permafrost makes microorganisms decompose previously frozen carbon, releasing carbon dioxide and CHCH 4. The melting of permafrost leads to the increase of water-saturated soil, which promotes methane-producing bacteria and a series of microorganisms to produce CH 4 and CO 2. it is predicted that by the end of this century, carbon emissions in anoxic environment will drive climate change to a greater extent than those in aerobic environment
3.2 Impact of Climate Change on Microorganisms
Climate change can directly (such as seasonality and temperature) or indirectly (such as plant composition, plant litter and root exudates) affect the structure and diversity of microbial communities. Soil microbial diversity affects plant diversity and is very important for ecosystem functions including carbon cycle. Short-term laboratory simulated warming and long-term (more than 50 years) natural geothermal warming initially promoted the growth and respiration of soil microorganisms, resulting in the net release of CO 2. With the consumption of substrate, biomass and microbial activity decreased. This means that microbial communities are not easy to adapt to high temperature, which reduces the overall loss of carbon by affecting the reaction rate and substrate loss. In contrast, a study in 10 years found that soil communities can adapt to the rising temperature by changing the use pattern of substrates, thus reducing carbon loss. Substantial changes in bacterial and fungal communities were also found in forest soil with an annual average temperature exceeding 20℃.
The response of microbial growth to temperature is complex and changeable. Microbial growth efficiency is an index to measure how microorganisms can effectively convert organic matter into biomass. Lower efficiency means more carbon is released into the atmosphere. A week-long laboratory study found that the increase in temperature led to an increase in microbial turnover rate, but the growth efficiency of microorganisms did not change. At the same time, the study predicts that climate warming will promote the accumulation of carbon in soil. 18 years of field research found that the higher the soil temperature, the lower the efficiency of microorganisms. At the end of this period, the decomposition of non-degradable substrates will increase, and the net loss of soil carbon will also increase.
Climate change directly or indirectly affects microbial communities and their functions through several interrelated factors, such as temperature, precipitation, soil properties and plant input. Because microorganisms in desert soil are limited by carbon, the increase of plant carbon input promotes the transformation of nitrogen-containing compounds, microbial biomass, diversity, enzyme activity and the utilization of complex organic matter. Although these changes may enhance respiration and the net loss of carbon in soil, the characteristics of arid and semi-arid areas may mean that they can act as carbon sinks. In order to better understand the response of aboveground plant biomass to CO 2 level and seasonal precipitation, we still need to increase our understanding of microbial community response and function.
Climate change has also increased the frequency, intensity and duration of eutrophication of lakes, seawater and other environments. Blooming cyanobacteria can produce a variety of neurotoxins, hepatotoxins and skin toxins, which are harmful to the health of birds and mammals. Toxic cyanobacteria have caused serious water quality problems in many parts of the world, including Taihu Lake in China. Climate change is directly and indirectly beneficial to the growth of cyanobacteria, and many cyanobacteria that form blooms can grow at relatively high temperatures. At the same time, with the increase of thermal stratification in lakes and reservoirs, buoyant cyanobacteria can float upwards, forming dense surface blooms, so that they can get better illumination and have more selection advantages. At present, laboratory and in-situ experiments have proved that harmful cyanobacteria Microcystis have the ability to adapt to high CO 2. Therefore, climate change and the increase of CO 2 content are expected to affect the bacterial composition of cyanobacteria bloom.
4 agriculture
According to the data of the World Bank, nearly 40% of the land environment is used for agriculture. It is expected that this proportion will increase in the future, which will lead to major changes in the circulation of nutrients such as carbon, nitrogen and phosphorus in the soil. In addition, these changes are closely related to the loss of biodiversity. To increase the understanding of the utilization of microorganisms related to animals and plants, so as to improve the sustainable development of agriculture and reduce the impact of climate change on food production, but this requires a better understanding of the response of microorganisms to climate change.
4. 1 Effects of microorganisms on climate change
Methanobacteria produce methane in natural and artificial anaerobic environments, and there are also artificial methane emissions related to fossil fuels (Figure 2). In recent years (20 14-20 17), the atmospheric CH 4 level has increased significantly, but the reasons behind it are still unclear. Although rice only covers 10% of arable land, it feeds half of the world's population. Similarly, rice fields contribute 20% of agricultural methane emissions. It is predicted that by the end of this century, man-made climate change will double the methane emission from rice production. Ruminants are the largest single man-made source of CH 4 emission, and the carbon emission from meat production of ruminants is 19-48 times higher than that from high-protein food production of plants. Even the CH 4 produced by non-ruminant meat production is 3- 10 times higher than that produced by plant high-protein food. The burning of fossil fuels and the use of chemical fertilizers have greatly increased the content of available nitrogen in the environment, destroyed the global biogeochemical process and threatened the sustainable development of ecosystems. Agriculture is the biggest emitter of greenhouse gas NO2, which is released through microbial oxidation and nitrogen reduction. Climate change disturbs microbial nitrogen transformation (decomposition, mineralization, nitrification, denitrification and fixation) and N 2 O release rate. It is urgent to understand the effects of climate change and other human activities on microbial transformation of nitrogen-containing compounds.
4.2 Impact of Climate Change on Microorganisms
Rising temperature and drought have seriously affected the growth of crops. Fungi-based soil food webs are common in widely managed agriculture (such as pasture), while bacteria-based food webs usually appear in intensive systems, but compared with the latter, the former is more suitable for arid environment. The evaluation of topsoil around the world shows that soil fungi and bacteria occupy a specific niche and have different responses to precipitation and soil pH, which indicates that climate change will have different effects on their abundance, diversity and function. It is predicted that the intensification of drought caused by climate change will reduce the diversity and abundance of bacteria and fungi in drylands around the world, which will further reduce the overall function of microbial communities, thus limiting their ability to support plant growth.
Climate change and eutrophication (due to the application of chemical fertilizers) have unpredictable effects on the comprehensive competitiveness of microorganisms. For example, rich nutrition is usually beneficial to the reproduction of harmful algae, but different results have been observed in the relatively deep lake Zurich.
5 infectious diseases
Climate change affects the occurrence and spread of diseases in marine and terrestrial biota (Figure 3), which depends on different socio-economic, environmental and host pathogen specific factors. To understand the spread of diseases and design effective control strategies, it is necessary to fully understand the ecology of pathogens, their vectors and hosts, as well as diffusion and environmental factors (table 1). For example, ocean acidification may directly lead to tissue damage of fish and other organisms, and may weaken the immune system, thus creating opportunities for bacterial invasion. For crops, when people consider the response to pathogens, different interaction factors, including CO 2 level, climate change and the interaction between plants and pathogens, are very important. Different microorganisms will cause different plant diseases, which will affect crop yield, lead to famine and threaten food security. The spread of pathogens and the emergence of diseases are promoted by the transportation and introduction of species, and influenced by weather and growth environment conditions.
Table 1 transmission response of pathogens to climate and environmental factors.
Climate change can increase the risk of diseases by changing the adaptability of hosts and parasites. For ectotherms (such as amphibians), temperature can increase the susceptibility to infection by interfering with immune response. Unpredictable monthly and daily environmental temperature fluctuations increase the sensitivity of the Cuban tree frog to the pathogenic chicory fungus Batrachochytrium dendrobatidis. The effect of temperature rise on infection is in contrast to the decline of fungal growth ability in pure culture, which indicates that more attention should be paid to evaluating host-pathogen response (rather than inferring from the growth rate of isolated microorganisms) when evaluating the correlation of climate change. Climate change is expected to increase the resistance rate of some human pathogens to antibiotics. According to the data of 20 13-20 15, the increase of daily minimum temperature 10℃ will increase the antibiotic resistance rate of Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus by 2-4%. The potential mechanisms include: high temperature promotes the horizontal gene transfer of drug-resistant genetic factors, increases the growth rate of pathogens, and promotes the sustainability, carrying and spread of the environment.
Food-borne, air-borne, water-borne and other environmental pathogens may be vulnerable to climate change (table 1). For vector-borne diseases, climate change will affect the distribution of media, thus affecting the scope of disease transmission and the efficiency of vector-borne pathogens. Many infectious diseases, including several vector-borne diseases and water-borne diseases, are strongly influenced by climate change caused by large-scale climate phenomena (such as ENSO), which will destroy normal rainfall patterns and temperature changes in about two-thirds of the world every few years. It is reported that ENSO-related diseases include malaria, dengue fever, Zika virus disease, cholera, plague, African equine disease and many other important human and livestock diseases.
Although the adaptation mechanism of microbial population has been studied under natural and laboratory conditions, compared with animals (including humans) and plants, the adaptation of microbial species to local environment is less studied. Viral, bacterial and fungal pathogens related to plants and animals adapt to abiotic and biological factors in a way that affects ecosystem function, human health and food security. The adaptive model of pathogenic agricultural fungi well illustrates the circular feedback between microbial activities and human activities. Agricultural adaptation pathogens are more likely to cause epidemics than naturally occurring strains, which will pose a greater threat to crop production. Fungal pathogens have evolved to adapt to higher temperatures to enhance their ability to invade new habitats, which makes the threat posed by fungal pathogens to natural and agricultural ecosystems more complicated.
6 Microorganisms Mitigate Climate Change
Increasing the understanding of microbial interaction will help to design measures to mitigate and control climate change and its effects. For example, in order to understand the response of mosquitoes to Wolbachia, a common living arthropod, the spread of Zika virus, dengue fever and Chikungunya virus was reduced by introducing Wolbachia into the Aedes aegypti population and releasing it into the environment. In agriculture, the progress in understanding the eco-physiology of microorganisms that reduce NO2 to harmless N 2 provides an option for reducing emissions. Biochar is an example of an agricultural solution, which can reduce the impact of climate change microorganisms widely and indirectly. Biochar is produced by thermochemical transformation of biomass under oxygen restriction. By reducing microbial mineralization, reducing the influence of root exudates on the release of organic minerals, promoting plant growth, reducing carbon release and increasing the retention of organic matter.
Microbial biotechnology can provide solutions for sustainable development, and microbial technology also provides practical solutions (chemicals, materials, energy and remedial measures) for many of the sustainable development goals of the United Nations 17, and solves the problems of poverty, hunger, health, clean water, clean energy, economic growth, industrial innovation and sustainable development. Undoubtedly, by raising the public's awareness of the main role of microorganisms in global warming, that is, by realizing the microbial literacy of society, it will undoubtedly promote support for this action.
7 abstract
Microorganisms have made great contributions to carbon fixation, especially marine phytoplankton, which have fixed as much net CO 2 as land plants. Therefore, the environmental changes affecting the photosynthesis of marine microorganisms and the subsequent storage of fixed carbon in deep water are of great significance to the global carbon cycle. Microorganisms also make great contributions to greenhouse gas emissions through heterotrophic respiration (CO 2), methane production (CH 4) and denitrification (N 2 O). Many factors affect the balance of greenhouse gas capture and emission by microorganisms, including the interaction and reaction of biological communities, local environment and food webs, especially man-made climate change and other human activities. Human activities that directly affect microorganisms include greenhouse gas emissions, pollution, agricultural activities and population growth, which promote the spread of climate change, pollution, agricultural activities and diseases. Human activities have changed the ratio of carbon fixation and release, which will accelerate the speed of climate change. In contrast, microorganisms also provide important opportunities to remedy man-made problems by improving agriculture, producing biofuels and repairing pollution.
In order to understand how the microbial diversity and activities of small-scale interaction in the controllable range can be transformed into large-scale system flux, it is very important to expand the research results from individuals to communities and then to the whole ecosystem. In order to understand the biogeochemical cycle and climate change feedback in different parts of the world, we need quantitative information about the organisms (including humans, plants and microorganisms) that promote the material cycle and the environmental conditions (including climate, soil physical and chemical characteristics, topography, ocean temperature, illumination and mixing) that regulate these biological activities.
The existing life has experienced billions of years of evolution, resulting in great biodiversity, and the diversity of microorganisms is actually infinite compared with macro-life. Due to the influence of human activities, the biodiversity of macroorganisms is rapidly declining, which indicates that the biodiversity of host-specific microorganisms of animal and plant species will also decrease. However, compared with macro-organisms, human beings know little about the relationship between microorganisms and man-made climate change. We can recognize the impact of microorganisms on climate change and the impact of climate change on microorganisms, but our understanding of ecosystems is not comprehensive, so there are still challenges in explaining the impact of man-made climate change on biological systems. Because human activities are causing climate change, it has an impact on the normal driving function of the global ecosystem. In marine and terrestrial biota, the increase of greenhouse gas emissions driven by microorganisms is actively fed back to climate change. Ignoring the role, influence and feedback of microbial communities on climate change may lead to a threat to human development. At present, there is an urgent need for immediate, sustained and coordinated efforts to explicitly incorporate microorganisms into research, technology development and policy and management decisions.
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