Microbial Ecology and Ecosystems Quiz

Microbial Ecology

• Microbial ecology studies microbes and their interactions with the environment and hosts.
• Microbes have a significant impact on the environment and on humans, despite their small size.
• Most types of microbes are still unknown. Estimates are that less than 1% of microbial species are identified.
• Microbes are found everywhere in air, water, and soil.
• A gram of soil can contain billions of microbes, representing thousands of different species.
• Understanding microbial ecology is crucial for preserving the health of the planet.

Benefits of Understanding Microbial Ecology

• Reducing cholera incidence in Bangladesh can be achieved by filtering water through old cloths.
• Vibrio cholera bacteria rarely survive in water for long periods.
• Copepods depend on V. cholera to digest chitin from their egg cases.
• Copepods are larger than V. cholerae and easier to filter.
• Filtering out copepods can reduce exposure to V. cholerae.
• Microbes recycle organic material in both aquatic and terrestrial ecosystems, supplying resources for plants and animals.
• Microbial activity in soil is crucial to agriculture.

Microbial Interactions and Habitats

• Microbes inhabit a wide range of habitats on Earth.
• Microbial communities form the foundation of Earth's biosphere.
• Microbes shape the environments inhabited by plants and animals.
• In the oceans, microbes are primary producers, creating biomass that feeds fish and humans.
• In forests and fields, microbes are the primary consumers, decomposing plant material and creating fertile soil.
• Microbes play a crucial role in determining soil, air, and water quality.

Microbes in Ecosystems

• All microbes exist within ecosystems, interacting with both living and nonliving components—such as microorganisms living in conjunction with animals and plants, or interacting with nutrients, etc.
• Each microbe population in an ecosystem has a specific niche (role).
• A niche describes how a species responds to resource distribution and interactions with competitors and predators.
• Example: Synechococcus (cyanobacteria), a free-living marine organism, fixes CO2 into biomass and produces oxygen, which is used by other heterotrophic bacteria.
• The habitat of Synechococcus is the upper layer of the ocean, where its biomass serves as food for protists, invertebrates, and fish.

Ecosystems

• Microbes form symbiotic systems.
• Mycorrhizae support and connect plant roots throughout forests and fields.
• Rhizobia fix nitrogen for legumes.
• Algae photosynthesize for coral reefs.
• Anaerobes digest complex plant fibers for termites, cattle, and humans.

Interaction between Microbes and Ecosystems - Assimilation

• Common assimilation reactions include CO2 fixation and nitrogen fixation.
• Primary producers are organisms that creates biomass from inorganic carbon (CO2).
• Primary producers are crucial for ecosystem productivity.
• Microbes can assimilate nutrients (N or P) from mineral sources when organic sources aren't available.

Interaction between Microbes and Ecosystems - Dissimilation

• Dissimilation involves breaking down organic nutrients into inorganic minerals (e.g., CO2, NO2).
• Microbial dissimilation in soil releases minerals for plant uptake.
• Dissimilation is a basis for wastewater treatment.

Food Webs and Trophic Levels

• Microbes play vital roles in food webs.
• Food webs show connections between primary producers, consumers, and decomposers.
• All organisms participate in food webs to obtain energy and materials for biomass production.
• A food web describes how organisms consume each other.
• Trophic level of an organism is the number of steps from the primary producer in a food chain.
• A food chain is a sequence linking organisms through nutrient and energy transfer when one organism consumes another.

Food Web and Trophic Levels in the Oceans

• Phytoplankton (e.g., dinoflagellates, diatoms) are primary producers in marine environments
• Being similar to terrestrial plants, phytoplankton use chlorophyll, needing sunlight for survival and growth.
• Floating in the upper ocean layers, phytoplankton are exposed to sunlight, supporting their growth.

Representative Ocean Food Webs

• A diagram depicting connections (food web) among organisms at hydrothermal vents.
• Illustrates energy flow in a hydrothermal vent ecosystem.
• Shows microbial, and other organisms, dependence on chemosynthesis, a process creating energy from chemicals.
• Heterotrophic microorganisms utilize chemicals for energy production.

Trophic Levels (Food Pyramids)

• Trophic levels illustrate how organisms are grouped based on their place in the food web.
• The first trophic level consists of producers (plants in terrestrial environments; phytoplankton in aquatic environments).
• The second trophic level consists of herbivores, feeding directly on producers.
• The third trophic level consists of carnivores, feeding on herbivores.
• Higher trophic levels have fewer organisms due to energy loss with each trophic level.
• 10% of energy transfers between trophic levels; rest lost via heat, wastes, etc.
• A tuna sandwich is an example of biomass/energy loss as one moves up the food pyramid/web.
• Removing a keystone species will cause major disruption in the food web because they have an outsized impact relative to their abundance.
• Example: New Zealand sea stars in Fiordland control mussel populations, and their removal leads to an increase in the number of mussels and subsequent changes to the ecosystem.

Aquatic Inhabitants

• Marine environments vary from deep oceans to shallower coastlines.
• Nutrients are scarce in deep ocean areas and abundant in shallow regions.
• Seawater contains high salt concentrations and can support halophilic (salt-loving) organisms.
• Ocean waters, generally oligotrophic (low nutrients), limit microorganism growth.
• Inshore marine environments can be dramatically altered and made unstable by nutrient runoff and elevated microbial growth.
• Hypoxia (a lack of oxygen) can result from overgrowth.

Freshwater Microbial Communities

• Undisturbed lakes are typically oligotrophic.
• The epilimnion (upper layer) is oxygenated and supports oxygenic organisms (like algae and cyanobacterium).
• The littoral zone at the lakes' edge is where water is shallow enough for plant growth.
• Eutrophic lakes receive large nutrient run-offs causing algal blooms, which deplete oxygen.
• Lack of oxygen can lead to fish deaths.
• Lakes with high Biological Oxygen demand (BOD) levels have experienced high microbial consumption of the oxygen in the water.

Soil and Subsurface Microbiology

• Terrestrial plants are the main producers in soil environments.
• Soil is a complex mixture of organic and mineral matter, supporting vast microbial communities.
• The O layer is the surface organic layer.
• The A zone is the aerated zone with active decomposition of organic matter.
• Lower soil layers contain increasing mineral and rock fragments, eventually reaching bedrock.
• Soil layers can have different oxygen levels (aerobic or anoxic).
• Bedrock is permeated with microbes.

Soil Food Web

• Top soil horizons feature complex food webs.
• Plants are the major producers in soil.
• Plant leaves (detritus) are decomposed by fungi (e.g., Mycena, others) and bacteria (e.g., actinomycetes).
• Bacteria in the rhizosphere (root zone) play significant roles.
• They may discourage pathogens.
• Microbes (such as protozoa, nematodes) prey on the leaf detritus consuming and cycling nutrients
• Microbes are interconnected in the soil food web, playing vital roles.

Decomposition of Lignin to Humus

• Fungi (e.g., white rot fungi) and bacteria (e.g., actinomycetes) are crucial for decomposing lignin (a complex plant compound in wood).
• Lignin decomposition produces humus (organic matter).
• Humus releases nutrients slowly for plant growth.
• Lignin decomposition is a gradual process.

Microbes Associated with Roots

• The rhizosphere and rhizoplane are the regions surrounding plant roots.
• These regions host high microbial populations, impacted by root exudates.
• Microbes (e.g., fungi, bacteria, rhizobia) in the rhizosphere can be beneficial or harmful for plant growth.
• Mycorrhizae are symbiotic associations of fungi and roots, enhancing nutrient uptake by the plant.

Mycorrhizae (The Fungal Internet)

• Mycorrhizae are fungi intimately associated with plant roots.
• They extend plant access to minerals; obtain energy from plant photosynthesis.
• Ectomycorrhizae grow around rootlets.
• Endomycorrhizae penetrate plant cells.
• These fungi exist underground and lack a sexual cycle.

Nutrient Cycles (Biogeochemical Cycles)

• Biogeochemical cycles describe how elements move between living and nonliving forms.
• Essential cycles include water, carbon, nitrogen, phosphorus, and sulfur.
• Energy flows directionally in ecosystems, entering as sunlight and leaving as heat.

Carbon Cycle

• Carbon exists primarily as carbon dioxide (CO2).
• Photosynthesis converts CO2 into organic compounds (e.g., glucose).
• Cellular respiration releases CO2.
• Decomposition releases CO2.
• Cycle shows movement of carbon in different forms throughout the environment.

Nitrogen Cycle

• Nitrogen is vital for living organisms (proteins and DNA).
• Atmospheric nitrogen (N2) is not directly usable by most organisms.
• Nitrogen-fixing bacteria convert N2 to ammonia (NH3), which is usable by plants.
• Plants and Animals utilize the ammonia in nitrogen-containing molecules.

Phosphorus Cycle

• Phosphorus is mostly found as phosphate ions (PO4).
• Phosphate is often present in sedimentary rocks.
• Weathering releases phosphate into the environment and is then used by plants and other organisms.

Test your knowledge on the essential roles of microbes in ecosystems and their impact on agriculture, carbon cycles, and nitrogen fixation. This quiz covers various aspects of microbial communities and their significance in environmental health. Explore how these tiny organisms contribute to soil, air, and water quality.