Microbial metabolism is the engine that drives nutrient cycling and energy flow in aquatic ecosystems. From cellular respiration to photosynthesis, microbes employ diverse strategies to obtain energy and nutrients, shaping water quality and ecosystem dynamics.
Understanding microbial metabolism is crucial for managing aquatic environments. By breaking down organic matter, fixing nitrogen, and transforming inorganic compounds, microbes play a vital role in nutrient cycling and energy transfer throughout aquatic food webs.
Microbial metabolism overview
Microbial metabolism plays a crucial role in the functioning of aquatic ecosystems by driving nutrient cycling and energy flow
Microorganisms exhibit diverse metabolic strategies to obtain energy and nutrients from their environment
Understanding microbial metabolism is essential for managing water quality and predicting ecosystem responses to environmental changes
Cellular respiration in microbes
Top images from around the web for Cellular respiration in microbes
Powering the Cell: Cellular Respiration and Glycolysis ‹ OpenCurriculum View original
Is this image relevant?
Frontiers | Microbial Respiration, the Engine of Ocean Deoxygenation View original
Is this image relevant?
Anaerobic Respiration | Boundless Microbiology View original
Is this image relevant?
Powering the Cell: Cellular Respiration and Glycolysis ‹ OpenCurriculum View original
Is this image relevant?
Frontiers | Microbial Respiration, the Engine of Ocean Deoxygenation View original
Is this image relevant?
1 of 3
Top images from around the web for Cellular respiration in microbes
Powering the Cell: Cellular Respiration and Glycolysis ‹ OpenCurriculum View original
Is this image relevant?
Frontiers | Microbial Respiration, the Engine of Ocean Deoxygenation View original
Is this image relevant?
Anaerobic Respiration | Boundless Microbiology View original
Is this image relevant?
Powering the Cell: Cellular Respiration and Glycolysis ‹ OpenCurriculum View original
Is this image relevant?
Frontiers | Microbial Respiration, the Engine of Ocean Deoxygenation View original
Is this image relevant?
1 of 3
Cellular respiration is the process by which microbes break down organic compounds to generate energy in the form of ATP
Aerobic respiration requires oxygen as the terminal electron acceptor and yields the highest amount of energy (glucose, pyruvate)
Anaerobic respiration utilizes alternative electron acceptors such as nitrate, sulfate, or iron when oxygen is limited
Microbes in aquatic sediments often rely on anaerobic respiration due to the low oxygen availability in these environments
Fermentation processes
Fermentation is an anaerobic metabolic process that generates energy through the breakdown of organic compounds without the use of an external electron acceptor
Lactic acid fermentation is common in bacteria and produces lactic acid as the end product (Lactobacillus)
Alcohol fermentation is carried out by yeasts and results in the production of ethanol and carbon dioxide (Saccharomyces)
Fermentation processes are important in the decomposition of organic matter in anoxic zones of aquatic ecosystems
Photosynthesis in aquatic microorganisms
Photosynthesis is the process by which microorganisms convert light energy into chemical energy stored in organic compounds
Cyanobacteria and algae are the primary photosynthetic microorganisms in aquatic environments
Oxygenic photosynthesis releases oxygen as a byproduct and is responsible for the oxygenation of Earth's atmosphere (cyanobacteria)
Anoxygenic photosynthesis utilizes alternative electron donors such as hydrogen sulfide or hydrogen and does not produce oxygen (purple and green sulfur bacteria)
Chemosynthesis in extreme environments
Chemosynthesis is the process by which microorganisms obtain energy from the oxidation of inorganic compounds
Chemosynthetic microbes are found in extreme environments such as hydrothermal vents, cold seeps, and sulfidic springs
Sulfur-oxidizing bacteria derive energy from the oxidation of reduced sulfur compounds (Beggiatoa, Thiobacillus)
Methanogenic archaea produce methane using hydrogen and carbon dioxide in anaerobic environments (deep-sea sediments, wetlands)
Energy sources for microbes
Microorganisms have evolved to utilize a wide range of energy sources to support their metabolic processes
The availability and type of energy sources in an aquatic environment shape the microbial community composition and function
Organic compounds as energy sources
Organic compounds such as carbohydrates, proteins, and lipids serve as energy sources for heterotrophic microbes
Microbes secrete extracellular enzymes to break down complex organic matter into simpler compounds that can be transported into the cell
The degradation of organic matter by microbes releases nutrients and carbon dioxide, contributing to nutrient cycling in aquatic ecosystems
Dissolved organic carbon (DOC) is a major energy source for aquatic microbes, especially in oligotrophic environments
Inorganic compounds as energy sources
Inorganic compounds can be used as energy sources by chemolithotrophic microbes through oxidation-reduction reactions
Hydrogen gas is an important energy source for methanogens and sulfate-reducing bacteria in anaerobic environments (deep-sea vents, sediments)
Reduced sulfur compounds (hydrogen sulfide, thiosulfate) are utilized by sulfur-oxidizing bacteria (Thiobacillus, Beggiatoa)
Ammonia and nitrite serve as energy sources for nitrifying bacteria (Nitrosomonas, Nitrobacter)
Light energy utilization
Light energy is harnessed by photosynthetic microorganisms to drive the synthesis of organic compounds
Phytoplankton (cyanobacteria and microalgae) are the primary producers in aquatic ecosystems, converting light energy into chemical energy
The availability and quality of light influence the distribution and productivity of photosynthetic microbes in the water column
Photoheterotrophic bacteria can utilize light energy to supplement their organic carbon requirements (aerobic anoxygenic phototrophic bacteria)
Nutrient cycling by microbes
Microorganisms play a vital role in the cycling of essential nutrients in aquatic ecosystems, including carbon, nitrogen, sulfur, and phosphorus
Microbial metabolic processes regulate the transformations and availability of these nutrients
Carbon cycle in aquatic ecosystems
Microbes are key drivers of the carbon cycle in aquatic environments, mediating the fixation, degradation, and mineralization of organic carbon
Photosynthetic microorganisms (phytoplankton) fix atmospheric carbon dioxide into organic compounds, forming the base of aquatic food webs
Heterotrophic bacteria and archaea decompose organic matter, releasing carbon dioxide and nutrients back into the water column
Methanogenic archaea produce methane as a byproduct of anaerobic carbon degradation, contributing to greenhouse gas emissions from aquatic ecosystems
Nitrogen cycle and microbial transformations
Microorganisms mediate the major transformations in the nitrogen cycle, including nitrogen fixation, nitrification, denitrification, and ammonification
Nitrogen-fixing bacteria (Rhizobium, Azotobacter) convert atmospheric nitrogen gas into ammonia, making it available for biological uptake
Nitrifying bacteria (Nitrosomonas, Nitrobacter) oxidize ammonia to nitrite and nitrate, important nutrients for primary producers
Denitrifying bacteria (Pseudomonas, Thiobacillus) reduce nitrate to nitrogen gas under anaerobic conditions, removing bioavailable nitrogen from the ecosystem
Sulfur cycle and microbial metabolism
Microbes play a central role in the sulfur cycle, participating in the oxidation and reduction of sulfur compounds
Sulfate-reducing bacteria (Desulfovibrio, Desulfobacter) reduce sulfate to hydrogen sulfide in anaerobic environments, contributing to the formation of sulfidic sediments
Sulfur-oxidizing bacteria (Beggiatoa, Thiobacillus) oxidize reduced sulfur compounds to sulfate, coupling this process with carbon fixation or heterotrophic growth
The microbial sulfur cycle is closely linked to the carbon and iron cycles in aquatic ecosystems
Phosphorus cycle and microbial interactions
Microorganisms influence the phosphorus cycle through the solubilization, immobilization, and mineralization of phosphorus compounds
Phosphate-solubilizing bacteria (Pseudomonas, Bacillus) release bound phosphorus from inorganic and organic sources, making it bioavailable for primary producers
Polyphosphate-accumulating organisms (PAOs) store excess phosphorus as intracellular polyphosphate granules, regulating phosphorus availability in the environment
The microbial phosphorus cycle is tightly coupled with the carbon and nitrogen cycles, as phosphorus is a limiting nutrient in many aquatic ecosystems
Microbial adaptations to aquatic environments
Aquatic microorganisms have evolved diverse adaptations to thrive in the unique conditions of their habitats
These adaptations enable microbes to optimize their metabolic processes and survive in challenging environments
Metabolic adaptations to low nutrient conditions
Oligotrophic environments (open oceans, deep lakes) have low concentrations of essential nutrients, requiring microbes to develop efficient nutrient acquisition strategies
Microbes in nutrient-poor environments often have high-affinity nutrient transport systems to scavenge trace amounts of nutrients from the water column
Some microorganisms form symbiotic associations with other organisms (coral-algae symbiosis) to optimize nutrient acquisition and recycling
Oligotrophic bacteria (SAR11 clade) have streamlined genomes and minimized cell sizes to reduce nutrient requirements
Strategies for survival in extreme pH
Acidophilic microorganisms (Acidithiobacillus, Sulfolobus) thrive in low pH environments (acid mine drainage, volcanic springs) by maintaining a near-neutral intracellular pH
Alkaliphilic microbes (Bacillus, Clostridium) adapt to high pH environments (soda lakes) by regulating intracellular pH and utilizing sodium ion gradients for energy production
Extremophiles have specialized cell membranes and enzymes that function optimally under extreme pH conditions
Some microorganisms can tolerate wide pH ranges (Euryarchaeota) by adjusting their metabolic processes and gene expression patterns
Temperature effects on microbial metabolism
Temperature influences the rate of microbial metabolic processes, with higher temperatures generally increasing reaction rates up to an optimal point
Psychrophilic microbes (Polaromonas, Psychrobacter) have adapted to cold environments (polar regions, deep oceans) with enzymes that function efficiently at low temperatures
Thermophilic microorganisms (Thermus, Pyrococcus) thrive in high-temperature environments (hot springs, hydrothermal vents) with heat-stable enzymes and proteins
Mesophilic microbes (Escherichia, Bacillus) grow optimally at moderate temperatures and are common in temperate aquatic environments
Pressure adaptations in deep-water microbes
High hydrostatic pressure in deep-water environments (deep-sea trenches, abyssal plains) affects microbial cell physiology and metabolic processes
Piezophilic (pressure-loving) microbes (Shewanella, Moritella) have adapted to high-pressure conditions with specialized membrane lipids and pressure-resistant proteins
Deep-sea microorganisms often have slower growth rates and lower metabolic activities compared to their shallow-water counterparts
Pressure-adapted microbes play important roles in the biogeochemical cycles and food webs of deep-water ecosystems
Microbial interactions in aquatic ecosystems
Microorganisms in aquatic environments engage in complex interactions with each other and with other organisms
These interactions shape the structure and function of microbial communities and influence ecosystem processes
Symbiotic relationships between microbes
Mutualistic symbioses involve the exchange of benefits between microbial partners, such as nutrient sharing or protection from environmental stressors (lichens, coral-algae symbiosis)
Commensalistic relationships occur when one microbial partner benefits while the other is unaffected (epibionts on aquatic plants)
Parasitic interactions involve one microbe exploiting another, often resulting in harm to the host (phytoplankton parasites, bacterial viruses)
Syntrophic associations involve the cooperative metabolism of substrates, where the byproducts of one microbe serve as the energy source for another (methanogenic consortia)
Competition for resources among microbes
Microorganisms compete for limited resources such as nutrients, space, and light in aquatic environments
Competitive interactions can lead to the dominance of certain microbial species or strains with superior resource acquisition strategies
Allelopathy, the production of inhibitory compounds, is a competitive strategy used by some microalgae to suppress the growth of rivals (Prymnesium parvum)
Resource partitioning and niche differentiation help to maintain microbial diversity by reducing direct competition
Microbial food webs and trophic interactions
Microorganisms form the foundation of aquatic food webs, channeling energy and nutrients to higher trophic levels
Phytoplankton (primary producers) are consumed by zooplankton (primary consumers), which in turn are eaten by larger organisms (secondary consumers)
The microbial loop describes the recycling of dissolved organic matter by bacteria and their subsequent consumption by protists, linking primary production to higher trophic levels
Viral lysis of microbial cells releases nutrients back into the environment, influencing biogeochemical cycles and food web dynamics
Microbe-invertebrate relationships
Microorganisms form symbiotic associations with aquatic invertebrates, contributing to their nutrition, defense, and development
Chemosynthetic bacteria provide energy and nutrients to invertebrates (tubeworms, mussels) in deep-sea hydrothermal vent communities
Microbial biofilms on the surfaces of aquatic invertebrates (crustaceans, corals) protect against pathogens and environmental stressors
Invertebrate larvae (sponges, corals) acquire specific microbial symbionts from the environment during their development, establishing long-term partnerships
Anthropogenic impacts on microbial metabolism
Human activities can significantly influence microbial metabolism in aquatic ecosystems, often with consequences for water quality and ecosystem health
Anthropogenic factors such as pollution, eutrophication, and climate change alter the physical and chemical conditions that shape microbial communities
Eutrophication effects on microbial processes
Eutrophication, the excessive enrichment of water bodies with nutrients (nitrogen, phosphorus), stimulates the growth of phytoplankton and cyanobacterial blooms
Increased primary production leads to the accumulation of organic matter, which is decomposed by heterotrophic bacteria, depleting dissolved oxygen levels (hypoxia, anoxia)
Anoxic conditions favor the growth of anaerobic microbes (sulfate reducers, methanogens), leading to the production of toxic hydrogen sulfide and methane
Eutrophication-induced changes in microbial metabolism can result in the loss of biodiversity, fish kills, and the degradation of water quality
Pollutant degradation by microorganisms
Microorganisms have the ability to degrade a wide range of pollutants, including hydrocarbons, pesticides, and heavy metals
Bioremediation technologies harness the metabolic capabilities of microbes to clean up contaminated aquatic environments (oil spills, industrial effluents)
Pollutant-degrading bacteria (Pseudomonas, Alcanivorax) use contaminants as carbon and energy sources, converting them into less harmful compounds
The efficiency of microbial pollutant degradation depends on factors such as pollutant bioavailability, microbial community composition, and environmental conditions
Climate change impacts on microbial metabolism
Climate change affects aquatic ecosystems through changes in temperature, precipitation patterns, and ocean acidification
Warming temperatures can accelerate microbial metabolic rates, leading to increased respiration and the release of greenhouse gases (carbon dioxide, methane)
Altered precipitation regimes influence the input of nutrients and organic matter into aquatic systems, modifying microbial community structure and function
Ocean acidification, caused by the absorption of atmospheric carbon dioxide, affects the calcification and metabolism of marine microorganisms (coccolithophores, foraminifera)
Microplastics as substrates for microbial growth
Microplastics, tiny plastic particles (<5 mm), have emerged as a pervasive pollutant in aquatic environments
Microorganisms can colonize the surfaces of microplastics, forming biofilms known as the "plastisphere"
The plastisphere provides a unique habitat for microbes, with distinct community compositions compared to the surrounding water column
Microbial degradation of microplastics is limited, as most plastics are resistant to biodegradation, leading to their accumulation in aquatic food webs