Name: how microbes hunt and defend
Uploaded: 2026-03-12T13:57:44.000Z
Duration: 1 min 28 s
Channel: JoVE

微生物による捕食とは、微生物が他の微生物を殺し、栄養を得るために食べる過程のことです。一部の捕食性細菌は、その戦略に基づいてエピバイオティックまたはエンドバイオティックと分類されます。ヴァンピロコッカスのようなエピバイオティック捕食者は獲物の外膜に付着し、溶解酵素を分泌し、放出された細胞質物質を吸収します。ブデロヴィブリオのようなエンドバイオティック捕食者は、獲物細胞に付着し、その外膜を貫通してペリプラズム空間に入ることで生活環を開始します。体内に入ると、捕食者は宿主を球状のブデロプラストに変えます。その後、細長化して増殖し、宿主を解体して子孫を放出します。ミクソコッカス は他の微生物を捕食することもできますが、有機物にも腐生的に増殖します。捕食時には、協調した ミクソコッカスの 集団が滑空運動を利用して獲物に接近し、群れをなして獲物細胞を溶かす酵素や抗生物質を放出します。捕食性原生動物は細菌を食べて、食物網を通じて炭素やエネルギーを移動させるのを助けます。食性侵食を防ぐために、細菌はしばしばフィラメントやマイクロコロニー、バイオフィルムなどの大きな構造を形成します。

微生物間相互作用:捕食

Microbial Interactions: Predation

微生物による捕食とは、ある微生物が別の微生物を殺し、栄養素やエネルギーを得るために消費する過程を指します。細菌性と原生動物の両方の捕食者を含みます。この相互作用は微生物群集の形成や栄養循環の調節に重要な役割を果たします。<h3>細菌の捕食者:エピバイオティクスとエンドバイオティクスの違い</h3>細菌の捕食者は攻撃様式に基づいてエピバイオティックまたはエンドバイオティックに分類されます。 ヴァンピロコッカスのようなエピバイオティック捕食者は獲物細胞の表面に付着し、プロテアーゼやヌクレアーゼなどの加水分解酵素を分泌して宿主細胞を溶解し、細胞質内容物を放出して栄養吸収を行います。対照的に、 Bdellovibrio bacteriovorus のような内生性捕食者は、獲物細胞の外膜に付着し、周辺空間に侵入することで生活環を開始します。ペリプラズム空間内で捕食者は伸びて複製し、最終的に宿主細胞を溶解させて複数の子孫を放出します。<h3>ミクソコッカスによる兼性捕食</h3>Myxococcus xanthusは兼性細菌の捕食者で、有機物をあさりと他の微生物を積極的に捕食する間を交互に行います。滑空運動を駆使し、協調したミクソコカムの集団が獲物に群がり、飲み込みます。これらの群れは分解酵素や二次代謝物の群れを分泌し、ミクソビレシンやミキシサラミドなどの抗菌化合物を含み、被食細胞の溶解や競争相手の抑制を助けます。この協力的な行動は細菌間の社会的捕食の例であり、細胞のシグナル伝達機構によって調節されています。<h3>原生動物の放牧と細菌防御</h3>捕食性原生動物—主に異栄養性鞭毛虫や繊毛虫—は、貪食作用を通じて細菌の集団を食い食います。これらの原生動物は、微生物の食物網を通じて炭素とエネルギーを輸送するという重要な生態学的役割を果たします。これに対抗して、細菌は細長いフィラメントや集まったマイクロコロニー、複雑なバイオフィルムを形成するなどの防御戦略を取ることが多いです。これらの構造的適応は物理的保護を提供し、個々の細胞へのアクセスを制限することで、原生動物が細菌の標的を包み込んだり侵入したりすることを難しくし、それによって食い込み圧力下での生存率を高めます。

Microbial predation refers to the process by which one microorganism kills and consumes another to obtain nutrients and energy. It encompasses both ...

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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 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 enzymes, including proteases and nucleases, break the host cell open so the predator can absorb the released cytoplasmic contents. Endobiotic predators, such as Bdellovibrio bacteriovorus, begin by attaching to the outer membrane of a prey cell and then moving into the periplasmic space.

Inside the periplasmic space, Bdellovibrio elongates and replicates. It then lyses the host cell and releases multiple progeny. Another bacterial predator, Myxococcus xanthus, can switch between scavenging organic matter and actively preying on other microbes. It uses gliding motility and coordinated swarms to move toward prey, engulf it, and release degradative enzymes and secondary metabolites.

Myxococcus swarms also produce antimicrobial compounds such as myxovirescin and myxalamide. These compounds help lyse prey cells and inhibit competitors. This group behavior is called social predation, and it is controlled by cell signaling. Protozoan predators, mainly heterotrophic flagellates and ciliates, graze on bacteria by phagocytosis, which is the process of engulfing cells. In the microbial food web, they transfer carbon and energy to higher levels.

Bacteria do not stay passive during grazing pressure. Many form elongated filaments, clustered microcolonies, or complex biofilms as defenses. These structures give physical protection and make individual cells harder for protozoans to engulf or penetrate. These adaptations can improve bacterial survival when predators are present.

How Microbes Hunt and Defend

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

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

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 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 bacterial and protozoan predators kill, consume, and graze on microbes, and how bacteria defend themselves with filaments, microcolonies, and biofilms.

How Microbes Hunt and Defend | 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 Hunt and Defend

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