Microbiology: Microbial Habitats

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Questions and Answers

Name the 3 major habitats mentioned in the content.

aquatic, terrestrial, atmospheric

What are the two categories of microorganisms based on their origin in a habitat?

Allochthonous (correct)

Exogenous

Autochthonous (correct)

Endogenous

In aquatic environments, what increases 1 atm with each 10 m in depth?

pressure

Photosynthetic activity usually occurs in the Profundal zone of lakes.

False Signup and view all the answers

Match the lake zones with their descriptions:

Epilimnion = Warm and O2 rich Thermocline = Rapid decrease of temperature Hypolimnion = Low temperature, low O2 concentrations, poor light penetration Signup and view all the answers

Where is the upper littoral zone of Phaeophyta located?

sublittoral zone Signup and view all the answers

Which group of organisms are found in the upper region of the ocean?

Marine plankton Signup and view all the answers

Viruses are important members of marine and aquatic microbial communities.

True Signup and view all the answers

The average VLP density in seawater is approximately $10^6$ to $10^7$/milliliter.

VLP (virus-like particle) Signup and view all the answers

Match the following environments with relevant information:

Benthic Marine Environments = the largest microbial biomass is under the sea Ocean Sediments (benthos) = revealed important information on microbial communities Barophilic microbes = able to tolerate atmospheric pressures up to 1,100 atm Signup and view all the answers

What are some nutrient sources for microorganisms in streams and rivers?

Autochthonous (in stream production based on photosynthetic organisms) and allochthonous (source is outside the stream) Signup and view all the answers

What distinguishes eutrophic systems in rivers and streams?

All of the above Signup and view all the answers

Marine environments cover approximately 97% of the Earth's water surface.

True Signup and view all the answers

Estuaries are semi-enclosed coastal regions where a ____ meets the sea.

river Signup and view all the answers

Match the following marine habitats with their descriptions:

Intertidal zone = Interface between marine ecosphere and litosphere with alternate flooding and drying periods Neritic zone = Nearshore zone from low tide mark to edge of continental shelf Continental slope = Sloping region from edge of continental shelf dropping down to the sea floor Signup and view all the answers

Study Notes

Marine Environments

Phaeophyta (brown algae) are found in the upper littoral zone to sublittoral zone, up to 220 m in clear tropical water.
Marine plankton (Chlorophyta and Chrysophyta) are found in the upper region of the ocean, 0-50 m deep.
Green algae are found above 30 m deep.
Marine protozoa are also present in marine environments.

Viruses in the Marine Environment

Viruses are important members of marine and aquatic microbial communities.
Virioplankton are the most numerous members of marine ecosystems.
Virus-like particles (VLPs) are viruses that have been enumerated by transmission electron microscopy.
The average VLP density in seawater is 10^6 to 10^7 per milliliter.
Phage particles are recognized as the most abundant life form on Earth.

Benthic Marine Environments

The largest microbial biomass is found under the sea.
Recent studies on ocean sediments have revealed important information on microbial communities.
The total subsurface biomass equals that of all terrestrial and marine plants.
Some microbes are barophilic and can tolerate atmospheric pressures up to 1,100 atm.

Microbial Habitats

There are three major habitats: aquatic, terrestrial, and atmospheric.
Hydrosphere is an important habitat for microorganisms.

Water as a Microbial Habitat

Important physical factors in aquatic environments include dissolved oxygen content, temperature, pH, and light penetration.
Microorganisms can be autochthonous (indigenous) or allochthonous (foreign) in aquatic environments.

General Influencing Factors in Aquatic Environments

Light determines the rate of photosynthesis and is dependent on the clarity of water, season, and latitude.
Temperature is determined by latitude and weather condition, and affects the distribution of heat in water bodies.
Pressure increases with depth, affecting the metabolism of organisms and the dissociation of carbonic acids, leading to a decrease in pH.
Nutrient availability varies greatly in aquatic environments.
Dissolved gases, including oxygen, carbon dioxide, and nitrogen, are important in aquatic environments.

Freshwater Habitats

Lotic systems include free-running waters, such as rivers, streams, and canals.
Lentic systems include free-standing waters, such as ponds, lakes, marshes, and slow-moving rivers.
The neuston layer of freshwater habitats is a habitat for microorganisms, with a higher density of microorganisms than underlying water.

Zones in Freshwater Habitats

The littoral zone has full light penetration and is dominated by submerged or partially submerged higher plants, algae, and cyanobacteria.
The limnetic zone is open water away from shore, with full light penetration and dominated by algae and cyanobacteria.
The light compensation point is the lowest level with effective light penetration, where photosynthetic activity equals respiratory activity.
The profundal zone has very low light penetration, high in organic nutrients, and is dominated by anaerobic heterotrophs.

Zonation of Lakes

The epilimnion is the warm and oxygen-rich surface layer.
The thermocline is the zone of rapid temperature decrease.
The hypolimnion is the cold and oxygen-poor bottom layer.

Stratification and Productivity in Lakes

Phytoplankton are confined to the epilimnion during summer stratification.
Productivity is dependent on nutrient inputs to the lake and nutrient recycling in the epilimnion.

Factors Affecting Growth of Microorganisms in Ponds and Lakes

Temperature, pH, oxygen, sunlight penetration, and nutrient availability affect the growth of microorganisms.

Eutrophication

Eutrophication is the process of nutrient enrichment, stimulating the growth of plants, algae, and bacteria.
Effects of eutrophication include reduced submerged aquatic vegetation, increased turbidity, and decreased oxygen levels.

Microbial Communities in Lakes and Ponds

Surface waters have autochthonous photoautotrophic bacteria, such as cyanobacteria.
Deeper waters have heterotrophic bacteria, anaerobic photoautotrophic bacteria, and sulfate-reducing organisms.
Sediments have anaerobic bacteria, including methanogenic bacteria and Desulfovibrio spp.

Nutrient Cycles in Lakes and Ponds

Phytoplankton grow and fix CO2 to form organic matter, acquiring N and P from water.
Biomass of phytoplankton enters the microbial loop, releasing dissolved organic matter that is used by heterotrophic bacteria.
Heterotrophic bacteria transform dissolved organic matter into particulate organic matter, which is consumed and digested by large predators, releasing C as CO2 and other nutrients that are recycled to phytoplankton.

Ecological Functions of Microorganisms in Fresh Water Environments

Decompose dead organic matter
Assimilate and reintroduce dissolved organic matter
Perform mineral cycling activities
Contribute to primary production
Serve as a food source for grazers### Microorganisms in Streams and Rivers
Microorganisms in streams and rivers are influenced by nutrient sources, which can be autochthonous (in-stream production based on photosynthetic organisms) or allochthonous (from outside the stream, e.g., runoff from urban, industrial, or agricultural sites).
Benthic microbial loops are important in most rivers and streams, with biofilms consisting primarily of heterotrophic microbes that are sources of degradation and mineralization.
Eutrophic systems can occur in streams and rivers, characterized by a high rate of respiration that exceeds photosynthesis, leading to anoxic conditions, and are often caused by runoff from agricultural and urban areas.
These eutrophic conditions can produce distinct, predictable changes in the microbial community, creating an oxygen sag curve.

Microorganisms in Lakes

Lakes are lentic systems, dominated by planktonic microbes and invertebrates.
Eutrophic lakes are nutrient-rich, with bottom sediments rich in organic matter, while oligotrophic lakes are nutrient-poor, remaining aerobic, and having a low microbial population.
Deep lakes are divided into two main regions: the littoral zone (shoreline) and the pelagic zone (central region).
The pelagic zone can be further divided into two layers: the epilimnion (warm upper layer) and the hypolimnion (deeper, cooler, bottom layer), which can be anaerobic, especially under nutrient-rich conditions.
The two layers are separated by a zone of rapid temperature decrease called a thermocline.

Microorganisms in Estuaries and Salt Marshes

Estuaries are semi-enclosed coastal regions where a river meets the sea, characterized by a salt wedge (salinity profile due to denser salt water).
Microorganisms in estuaries are often halotolerant, able to withstand large changes in salinity.
Estuarine waters are calm and nutrient-rich, but can also be prone to pollution, leading to loss of macroscopic life and harmful algal blooms.
Salt marshes are unlike estuaries, lacking freshwater input from a single river, and can be modeled in Winogradsky columns.

Microorganisms in Marine Environments

Marine environments encompass 97% of the Earth's water, with high pressure, high salinity (approximately 35%), and a pH range of 8.3-8.5.
Barophiles are microbes that thrive under high pressure.
Microorganisms in marine environments are adapted to survive in low-nutrient concentrations, are motile, and can exhibit unusual shapes.
Marine environments can be divided into freshwater habitats and marine habitats.

Horizontal and Vertical Stratification of Marine Habitats

Horizontal stratification includes the intertidal zone, neritic zone, continental slope, and oceanic zone.
Vertical stratification includes the euphotic zone, epipelagic zone, mesopelagic zone, bathypelagic zone, and benthic zone.
The euphotic zone is the area with effective light penetration, while the aphotic zone is below the euphotic zone.

Factors Affecting Microbial Growth in Marine Environments

Hydrostatic pressure, light, temperature, and nutrients are factors that affect microbial growth in marine environments.
Light absorption increases with depth, with only the euphotic zone (top 100 m) supporting primary productivity.
Nutrients are usually low at the surface and increase beneath the euphotic zone, with surface nutrient levels improving only during upwelling processes.

Microorganisms in the Open Ocean

Photosynthetic microbes that fix half of the world's carbon inhabit the upper 200-300 meters of the open ocean.
The open ocean is an oligotrophic environment, with low nutrient levels.
Microorganisms in the open ocean are adapted to survive in low-nutrient concentrations, and include SAR11, which are the most numerous organisms on Earth.

Ocean Photic Zone and Carbon Cycling

The ocean photic zone is the area where photosynthesis occurs, with a constant exchange of CO2 at the surface.
Dead organisms from the euphotic zone fall through the depths as marine snow, releasing nutrients that can be recycled back to the surface.
Nutrient-rich deep waters lack light energy for photosynthetic primary production, but can be fertilized with iron to trigger diatom blooms.

Nitrogen Cycling in the Open Ocean

The open ocean is limited by nitrogen, and recent studies have led to a new examination of the nitrogen cycle and amount of nitrogen fixed by various populations.
Bacterial consortia capable of anammox reaction (anaerobic reduction of NH4 to N2) cause the loss of nitrogen that would otherwise support life.

Abundance of Microbes in the Open Ocean

SAR11 are the most numerous organisms on Earth, making up 25% to 50% of the total bacteria and archaea in nearshore and open ocean surface waters.
SAR11 and Silicobacter demonstrate unique adaptations to living in the oligotrophic open ocean, including the production of photeorhodopsin proton pump.

Marine Microbial Community

The marine microbial community is composed of mostly gram-negative bacteria, such as Pseudomonas, Vibrio, and Flavobacterium, as well as gram-positive bacteria, such as Bacillus, in marine sediments.
Desulfovibrio and methanogens are found in sediments, while chemolithotropic bacteria, such as Nitrosococcus, Nitrosomonas, Nitrospina, and Nitrobacter, are involved in nitrogen cycling.
Marine algae of various divisions are also present in the marine microbial community.

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Description

This quiz covers the characteristics of microbial habitats, types of microorganisms in each habitat, and methods for evaluating them. It focuses on the three major habitats: aquatic, terrestrial, and atmospheric.