Name: how microbes produce methane
Uploaded: 2026-03-12T13:57:35.000Z
Duration: 1 min 26 s
Channel: JoVE

酸素のない環境では、メタン生成と呼ばれる特殊な古細菌がメタン生成を行い、エネルギー代謝の最終産物としてメタンを生成します。死んだ生物からの有機化合物はしばしば無酸素ゾーンに沈み、セルロ分解菌が単純糖に分解します。発酵微生物はこれらの糖を酢酸、アルコール、水素、二酸化炭素などの短鎖脂肪酸に変換します。メタンゲンはアセテートと水素を直接消費し、それらをメタンに変換することがあります。水素を摂取することで、メタン生成物質は水素レベルを低く保ち、発酵を継続できるようにします。シントロフィー菌はアルコールやその他の脂肪酸を酢酸、水素、二酸化炭素に変換することで分解を助けます。メタン原産物はこれらの化合物を使ってメタンを生成します。同様に、シロアリの腸内でも微生物はセルロースを糖に分解します。無酸素原生生物はこれらを水素に発酵させ、内共生のメタン生成物質がそれを消費します。これにより水素濃度が低く保たれ、シロアリがエネルギーとして吸収する発酵や酢酸塩の継続的な生成が可能になります。

微生物とメタン生成

Microbes and Methanogenesis

メタン生成は嫌気性生態系における重要な微生物プロセスであり、強力な温室効果ガスであり貴重なバイオ燃料であるメタンの生物的生成を担っています。この代謝経路は主にメタン生成性古細菌によって促進されており、これらは湿地、堆積物、動物の消化管などの無酸素環境で繁栄します。これらの生息地に酸素が欠如しているため、好気性呼吸が妨げられ、有機物分解のための代替生化学的経路が促進されます。嫌気性分解の初期段階では、死んだ生物の複雑な有機物がセルロ分解細菌によって加水分解され、単純糖が放出されます。これらの糖は他の微生物によって発酵され、アセテートのような短鎖脂肪酸やアルコール、水素(H₂)、二酸化炭素(CO₂)など、さまざまな中間代謝物に変換されます。メタン生成は、メタン生成物質がこれらの発酵生成物、特に酢酸塩や水素を使ってメタン(CH₄)を生成するときに起こります。水素栄養経路はCO₂をH₂によって還元します。CO2 + 4H2 → CH4 + 2H2Oもう一つの主要な経路であるアセトクラスティックメタン生成は、アセテートをメタンと二酸化炭素に変換します。CH3COO− + H+→ CH4 + CO2長鎖脂肪酸やアルコールのようなより複雑な基質の分解には、共生相互作用が必要です。 Syntrophomonas wolfeiのような合栄養素はH₂を生成し、メタン生成物質はこの水を消費して過程に適した熱力学を維持します。シロアリの腸内では、無酸素原生生物がセルロースを加水分解し、内共生メタン生成物質は生成された水素を代謝してメタンを生成します。一方、アセトゲン細菌はグルコースと芳香族化合物を使ってアセテートを生成し、宿主昆虫にとって重要なエネルギー源です。これらの微生物ネットワークは、嫌気性システムからのメタンフラックスを維持する上での共生と代謝の協力が生態学的に重要であることを強調しています。

Methanogenesis is a critical microbial process in anaerobic ecosystems responsible for the biological production of methane, a potent greenhouse gas and ...

https://cloudfront.jove.com/files/ftp_upload/40739/40739_article_thumb_40739.jpg

Education

JoVE Core

Microbiology

微生物学

Unit

ユニット

Microbial Ecology

微生物生態学

KEY TERMS AND CONCEPTS

主要用語と概念

how microbes produce methane

Methane production in anaerobic ecosystems depends on methanogenic archaea and the microbes that work with them. This process happens where oxygen is absent, such as wetlands, sediments, and animal gastrointestinal tracts. In these anoxic habitats, aerobic respiration cannot run, so microbes use other pathways to break down organic matter.

Anaerobic decomposition starts when cellulolytic bacteria, or cellulose-digesting bacteria, hydrolyze dead organic material into simple sugars. Other microbes then ferment those sugars into short-chain fatty acids such as acetate, plus alcohols, hydrogen (H2), and carbon dioxide (CO2). Methanogens use these fermentation products, especially acetate and hydrogen, to make methane (CH4).

Two major methanogenesis pathways are shown. In hydrogenotrophic methanogenesis, methanogens reduce CO2 with H2 to form methane and water. In acetoclastic methanogenesis, methanogens convert acetate into methane and carbon dioxide. Both routes help move carbon through oxygen-free environments.

More complex substrates, such as long-chain fatty acids and alcohols, require syntrophic interactions. Syntrophs are microbes that depend on partners to finish a metabolic job. For example, Syntrophomonas wolfei produces H2, and methanogens consume that hydrogen to keep the process thermodynamically favorable.

The transcript also shows this cooperation in termite guts. In these anoxic environments, protists break down cellulose, and endosymbiotic methanogens use the released hydrogen to produce methane. At the same time, acetogenic bacteria turn glucose and aromatic compounds into acetate, which serves as an important energy source for the host insect. These microbial partnerships show how methanogenesis supports methane flow in anaerobic systems.

How Microbes Produce Methane

introduction to microbial ecology

Microbial Communities in Soil and Extremes

Microbial ecology looks at how microorganisms live, interact, and adapt in different ecosystems. It also shows how these tiny organisms help shape nutrient cycling, energy flow, and environmental balance. An ecosystem includes living parts and non-living parts, and microbes respond to both. Microorganisms can form populations, which are groups of the same species living together at the same time. When populations from different species live and interact in the same place, they form a microbial...

ecological niche

Microbial Niches in Ecosystems

Microbial niches describe how microorganisms survive, grow, and interact in an ecosystem. A niche includes how a microbe gets resources, reproduces, and relates to other species in its environment. This idea helps explain microbial community dynamics, biogeography, and ecosystem function. A microorganism’s fundamental niche is the full range of conditions where it could survive, grow, and reproduce. These conditions include both biotic factors, such as living interactions, and abiotic factors,...

methods to assess microbial populations

Measuring Microbes in Samples

Measuring microbes in a sample helps scientists study health, ecology, and industry. Microbial counts can show how many cells are present, how diverse they are, and what they may be doing. To do this, researchers use both culture-based and molecular methods. A viable plate count is a classic culture method for estimating living microbes. The sample is first diluted step by step, then spread on nutrient agar plates. Each viable cell can grow into a visible colony, so the colonies can be counted.

methods to assess microbial communities

Measuring Microbial Diversity and Activity

Microbial communities include bacteria, archaea, and eukaryotic microorganisms. They live in many ecosystems and affect important environmental and biological processes. Scientists study these communities by looking at how many species are present, how many individuals each species has, and how evenly the species are spread out. Species richness is the number of different species in a sample. Species abundance is the relative amount of each species. Species evenness describes how uniformly the...

the winogradsky column

Microbial Layers Inside a Winogradsky Column

A Winogradsky column shows how microbial layers form in a simple, sealed ecosystem. It is a clear model for studying microbial ecology and how different metabolisms interact in sediment over time. The setup uses a transparent glass cylinder. Half of it is filled with sediment mixed with cellulose, such as shredded paper, calcium carbonate, and gypsum. The cellulose provides a carbon source. Calcium carbonate buffers pH, and gypsum supplies sulfate. The rest of the cylinder is filled with pond...

microenvironments

Microbial Niches in Tiny Habitats

Microorganisms live in tiny habitats called microenvironments. These spaces have their own physical and chemical conditions. Oxygen level, pH, temperature, light, and nutrient supply can all differ from the surrounding area. These local conditions strongly affect microbial growth, metabolism, and which species can live there. Microenvironments often have sharp gradients over very small distances. In soil, oxygen may be available at the particle surface but drop off just a few millimeters below.

microbial mats

Microbial Mats and Oxygen Gradients

Microbial mats are layered communities of microbes that grow in response to changes in light, oxygen, and nutrients. These ecosystems are highly organized, and different microorganisms live at different depths. Biofilms are the early stage of this growth and are only a few millimeters thick. Mature microbial mats can grow to centimeter scale and show clear vertical structure. This layered arrangement lets microbes fill separate niches within a very small space. In cyanobacterial mats from hot...

microbial interactions: mutualism

Mutualistic Partnerships in Nature

Mutualistic partnerships in nature show how two or more organisms can benefit from living together. These symbiotic relationships can be obligate, meaning the partners depend on each other, or facultative, meaning the association is helpful but not required. Mutualism helps support many ecosystem functions across land and water. One common example is the partnership between plant roots and mycorrhizal fungi, such as Rhizophagus species. The fungal hyphae grow into the root hairs and epidermis,...

microbial interactions: cooperation

Microbial Cooperation in Soil and Hosts

Microbial cooperation describes helpful interactions between different species. In these partnerships, microbes work together for one or mutual benefit. These interactions can shape ecosystems and evolution. They also play major roles in symbiosis and disease. One clear example involves the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes carry the bacteria in the soil and need an insect host to mature. When the nematode...

microbial interactions: predation

How Microbes Hunt and Defend

Microbial predation is a form of interaction in which one microorganism kills and eats another to gain nutrients and energy. It includes both bacterial predators and protozoan predators. This process helps shape microbial communities and affects how nutrients move through the environment. Some bacterial predators attack from the outside, while others enter the prey cell. Epibiotic predators, such as Vampirococcus, attach to the surface of a prey cell and release hydrolytic enzymes. These...

microbial interactions: competition

Microbial Competition and Niche Partitioning

Microbial competition shapes how bacteria and other microbes share space and resources. In shared environments, they compete for nutrients, space, or light. The strength of this competition depends on the environment, including nutrient levels, space limits, and how many microbial species are present. These interactions help determine the structure, function, and resilience of microbial communities. Microbial competition is usually grouped into exploitative competition and interference...

microbial interactions: parasitism

Microbial Parasites and Host Dependence

Microbial parasites depend on a host for nutrients and shelter, and this dependence often harms the host. In parasitism, only the parasite benefits. This is different from mutualism, where both organisms gain from the relationship. Microbial parasites are classified by where they live in or on the host. Ectoparasites stay on the host’s surface, such as the skin or outer tissues, and take in nutrients from outside. Endoparasites live inside the host’s body and invade tissues or organs.

microbe-plant interactions

How Plant Microbes Affect Growth

Plant microbes can help, harm, or simply live alongside their hosts. These microbe-plant interactions shape plant growth, health, and ecosystem function. The plant microbiome includes bacteria, fungi, archaea, protists, and viruses, and these organisms may live on the plant surface, inside plant tissues, or in symbiosis throughout the plant. Some of the most important beneficial partnerships involve mycorrhizal fungi. These fungi form close connections with roots and are grouped as arbuscular...

microbes and the carbon cycle

How Microbes Move Carbon Through Earth

Microbes move carbon through Earth’s major reservoirs and help drive the carbon cycle. Carbon shifts among the biosphere, lithosphere, atmosphere, and hydrosphere, where it supports life and helps regulate climate. It commonly cycles as carbon dioxide (CO2), the oxidized form of carbon, but methane (CH4) and organic compounds also matter. Photosynthetic microbes take in atmospheric CO2 and turn it into organic carbon. Cyanobacteria are especially important because they carry out oxygenic...

microbes and methanogenesis

Methane production in anaerobic ecosystems depends on methanogenic archaea and the microbes that work with them. This process happens where oxygen is absent, such as wetlands, sediments, and animal gastrointestinal tracts. In these anoxic habitats, aerobic respiration cannot run, so microbes use other pathways to break down organic matter. Anaerobic decomposition starts when cellulolytic bacteria, or cellulose-digesting bacteria, hydrolyze dead organic material into simple sugars. Other...

microbes and the nitrogen cycle

Microbial Steps in the Nitrogen Cycle

Microbes drive the nitrogen cycle by changing nitrogen into forms that plants and other organisms can use. This biogeochemical cycle keeps nitrogenous compounds balanced in ecosystems. It also supports plant growth and microbial growth. Nitrogen fixation begins the cycle by converting inert atmospheric nitrogen gas, N2, into ammonia, NH3. This step depends on nitrogenase enzymes. Free-living diazotrophs do this on their own. Aerobic bacteria such as Azotobacter spp. and anaerobic bacteria such...

microbes and the sulfur cycle

Sulfur Cycling Through Microbial Reactions

Sulfur cycling depends on microbial reactions that move sulfur through rocks, water, soil, and the air. In Earth systems, sulfur shifts among inorganic forms such as sulfate, elemental sulfur, and sulfide. These changes happen through both abiotic processes and biological activity in oxic and anoxic environments. Sulfate is the most oxidized form of sulfur. It is stored mainly in rocks, marine sediments, and ocean water, where it acts as a long-term reservoir in the global sulfur cycle. In...

microbes and other elemental cycles

Microbes Driving Iron and Manganese Cycles

Microbes drive iron and manganese cycling in aquatic environments by changing these metals between reduced and oxidized forms. These reactions are especially important along redox gradients, where oxygen levels shift across stratified water layers. The microbes use these metals for energy, growth, and structural needs. In oxygen-rich surface waters, iron is usually present as insoluble ferric iron, Fe(III). Some bacteria release siderophores, which are small organic molecules that bind ferric...

marine microbial ecology

Microbial Life in the Ocean

Marine microbial life is shaped by salinity, low nutrients, and changing oxygen levels. These physical and chemical limits influence which microbes can survive and how they function. They also affect how ocean microbes help drive nutrient and carbon cycling. Small cell size is common in these environments because it gives microbes a larger surface-to-volume ratio. That helps them take up nutrients more efficiently when nutrients are scarce. In estuaries, where salinity changes often,...

deep sea microbial ecology

Deep Sea Microbes and Extreme Conditions

Deep sea microbes live in one of Earth’s harshest environments. The deep ocean is far below the sunlit photic zone, which usually reaches the upper 100 to 200 meters of open water. Below that layer, the bathypelagic and abyssal zones stretch from about 1,000 to 6,000 meters, and hadal trenches go even deeper. This region is dark, cold, and highly pressurized. Temperatures are usually around 2 to 3°C, although hydrothermal vents can be slightly warmer. Pressure rises by about 1 atmosphere for...

freshwater microbial ecology

Microbes in Streams, Lakes, and Rivers

Freshwater microbes live in streams, rivers, lakes, ponds, and marshes, but their communities change with water movement, light, depth, and nutrients. These systems are often grouped into lotic waters, which flow, and lentic waters, which are still or slow-moving. The physical setting shapes where microbes grow and how they get energy. In lentic systems, phytoplankton are the main producers. They make autochthonous organic carbon, which means carbon made within the water body. In lotic...

soil microbial ecology

How Soil Microbes Cycle Nutrients

Soil microbes drive nutrient cycling, organic matter turnover, and ecosystem stability. A gram of soil can contain thousands of bacterial and archaeal taxa, but their shared job is what helps sustain land ecosystems. Their activity changes the way carbon, nitrogen, and other nutrients move through soil. Soil is a patchwork of minerals, organic matter, water, and air. Microbes live in tiny microhabitats shaped by pore size, moisture, oxygen, and nutrients. Sandy soils drain fast and tend to...

key terms and concepts

Learn how methanogenic archaea, bacteria, and syntrophic partners break down organic matter and make methane in wetlands, sediments, and animal guts.

How Microbes Produce Methane | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

How Microbes Produce Methane

Description

Transcript