Marine Bacteria: Metabolism, Habitats, and Ecological Roles
Are Marine Bacteria Oligotrophic, Psychrophilic, Mesophilic, or Barophilic?
Marine bacteria can be oligotrophic (thriving in low-nutrient environments), psychrophilic (cold-loving), mesophilic (moderate temperature-loving), or barophilic (pressure-loving), depending on the species and their specific environment.
Metabolism of Nitrobacter to Incorporate Cellular Carbon
Nitrobacter incorporates cellular carbon through the Calvin-Benson-Bassham cycle, using the energy generated from the oxidation of nitrite to nitrate.
How is the Genus Photobacterium Used as an Indicator of Contamination?
Some Photobacterium species are bioluminescent. Their presence and light production can indicate contamination, particularly in seafood, as their growth is often associated with spoilage.
Why is Mutagenesis Not Frequent in the Marine Environment?
Mutagenesis might be less frequent in some marine environments due to factors like dilution of mutagens, high DNA repair efficiency in some marine organisms, and strong selective pressures that quickly eliminate deleterious mutations.
Structure of a Black Smoker
Black smokers are hydrothermal vents found on the ocean floor. They are characterized by:
- Chimney-like structures formed by the precipitation of minerals from superheated, mineral-rich water.
- Superheated water (up to 400°C or higher) emanating from the vent, rich in dissolved minerals like sulfides.
- A surrounding ecosystem of unique organisms adapted to the extreme conditions.
Bacterial Types Responsible for the Primary Trophic Chain of Black Smoker Ecosystems
Chemolithoautotrophic bacteria are the primary producers in black smoker ecosystems. They utilize chemicals like hydrogen sulfide as an energy source and convert inorganic carbon into organic matter, forming the base of the food chain.
How Do Tubeworms Obtain Energy and Organic Matter?
Tubeworms, such as Riftia pachyptila, found near hydrothermal vents, have a symbiotic relationship with chemolithoautotrophic bacteria. These bacteria reside within the tubeworm’s trophosome (a specialized organ) and oxidize hydrogen sulfide to produce energy and organic compounds, which are then shared with the tubeworm.
Explain the Role of Quorum Sensing in Symbiosis Between Bacteria
Quorum sensing is a cell-to-cell communication mechanism in bacteria. It allows bacteria to coordinate gene expression based on population density. In symbiosis, quorum sensing can regulate:
- Colonization of the host.
- Bioluminescence (e.g., in Vibrio fischeri and the bobtail squid).
- Nutrient exchange between the symbiont and the host.
- Biofilm formation.
Explain the Role of the Following Bacteria in the Development of Elements
- Nitrobacter (Nitrogen Cycle – Nitrification): Nitrobacter plays a crucial role in nitrification, oxidizing nitrite (NO2–) to nitrate (NO3–).
- Desulfuromonas (Sulfur Cycle – Sulfate Reduction): Desulfuromonas species are involved in sulfur cycling. They can grow on acetate or lactate and reduce elemental sulfur to hydrogen sulfide (H2S).
- Pseudomonas (Multiple Cycles – Organic Matter Decomposition): Pseudomonas species are diverse and participate in various biogeochemical cycles. Many are heterotrophic, breaking down organic matter and contributing to nutrient cycling.
Explain the Metabolism of Chemolithotrophic Iron Bacteria and Provide a Marine Example
Chemolithotrophic iron bacteria obtain energy by oxidizing ferrous iron (Fe2+) to ferric iron (Fe3+). This process releases energy that is used to fix carbon dioxide (CO2). They require a source of reduced iron and often thrive in environments where anoxic, iron-rich water mixes with oxygenated water.
Example: Gallionella ferruginea is a marine iron-oxidizing bacterium found in iron-rich environments.
Where Can Halophilic Bacteria Be Found?
Halophilic bacteria are adapted to high-salt environments. They can be found in:
- Saline lakes
- Salt flats
- Seawater (especially in areas with high evaporation rates)
- Polar areas, where waters are brackish due to sea ice formation.
Cite a Marine Habitat for Thermotoga
Thermotoga species are hyperthermophilic bacteria. In marine environments, they are typically found in hydrothermal vents.
Explain the Metabolism of Nitrosomonas
Nitrosomonas is a chemolithoautotrophic bacterium that plays a key role in the nitrogen cycle. It obtains energy by oxidizing ammonia (NH3) to nitrite (NO2–) and uses CO2 as a carbon source.
Cite Three Genera of Chemolithotrophic Sulfur-Oxidizing Bacteria
- Beggiatoa
- Thiothrix
- Thiobacillus
Why Are Iron Bacteria Not Frequent in the Marine Environment?
Iron bacteria are often limited in marine environments because iron is typically scarce in oxygenated seawater. Iron tends to be in its oxidized, insoluble form (Fe3+), which is not readily available to iron-oxidizing bacteria.
Cite Three Niches in the Marine Environment Where Vibrio Can Be Isolated
- Surface of fish
- Coral reefs
- Intestines of marine animals
Why Can Marine Methylotrophs Be Isolated in Hydrothermal Vent Areas?
Hydrothermal vents release various reduced compounds, including methane and methylated compounds. Methylotrophs are bacteria that can utilize one-carbon compounds (like methane and methanol) as their source of carbon and energy. Therefore, these habitats provide the necessary compounds for their metabolism.
What is the Fate of Trimethylamine, a Major Product of Marine Animal Metabolism?
Trimethylamine (TMA) can be rapidly converted to methane (CH4) by methanogenic archaea in anoxic environments.
Denitrification
Denitrification is the process where nitrate (NO3–) is used as an electron acceptor in anaerobic conditions, ultimately producing nitrogen gas (N2). It requires an oxidizable organic or inorganic substrate as an electron donor. Denitrification can be performed by both heterotrophic and autotrophic bacteria.
- Autotrophic denitrification: Inorganic electron donors like hydrogen (H2) or sulfur compounds are used, and CO2 serves as the carbon source.
- Heterotrophic denitrification: Organic substrates like methanol serve as both the electron donor and carbon source.
Differential Characteristics of Thiomargarita
Thiomargarita is one of the largest known bacteria (100-300 µm in diameter). It is found in marine sediments. It penetrates the sediment, and when it returns to the surface, it accumulates nitrate in large vacuoles. These vacuoles and sulfur granules occupy the periphery of the cell.
Explain the Symbiosis of Chlorochromatium aggregatum
Chlorochromatium aggregatum is a bacterial consortium where a central, motile, rod-shaped, flagellated, chemoheterotrophic beta-proteobacterium is surrounded by 10 to 20 green sulfur epibionts. There is a positive size ratio between the organisms. Physical contact is required. The central bacterium moves the aggregate to suitable areas.
What is Metabiosis?
Metabiosis, also known as protocooperation, is a positive interaction between organisms where the association is not obligatory. The organisms involved do not require physical contact and can appear at different times.
What is the Most Important Repercussion of Eutrophication?
The most significant repercussion of eutrophication is the alteration of community structure due to nutrient enrichment. An increase in nitrates and phosphates leads to rapid microalgae growth, causing algal blooms. These blooms can lead to a marked reduction in dissolved oxygen due to excess organic matter decomposition. Consequently, there is a shift from autotrophic to heterotrophic production.
Virioplankton
Virioplankton are viruses that infect planktonic organisms. They typically range in size from 0.01 to 0.2 µm.
Where Does Thiomargarita Live?
Thiomargarita is a chemolithoautotrophic bacterium that oxidizes sulfur and lives in marine sediments.
Metabolism of Thiomargarita
Thiomargarita is a chemolithoautotroph that oxidizes sulfur as an energy source and uses nitrate as an electron acceptor.
Three Examples of Prosthecate and Sessile Bacteria Important in Aquatic Environments
- Caulobacter
- Caulobacter maris
- Hyphomonas
- Neptunium
Levels of Marine Archaea in the Marine Environment
Marine archaea are typically found at concentrations of 103 to 104 cells/mL.
How Are Uncultured Bacteria Detected?
Uncultured bacteria are detected by isolating them from their environment and observing that they do not grow in standard cultivation media.
How Can the Marine Environment Influence Climate?
The marine environment can influence climate through the production of dimethylsulfoniopropionate (DMSP), which is converted to dimethyl sulfide (DMS). DMS can be oxidized in the atmosphere to form sulfate aerosols, which can affect cloud formation and, consequently, climate.
Why is Ice an Important Habitat for Microorganisms?
Ice provides a habitat where microorganisms can survive due to their low-temperature enzymatic systems. Additionally, there is reduced predation in this environment.
Where Do Cold-Adapted Microorganisms Primarily Grow in Water?
Cold-adapted microorganisms primarily grow in polar regions.
Where is Methane Hydrate Found?
Methane hydrate appears in cold seeps, along plate boundaries associated with both active and passive margins. It is found in waters sufficiently cold and under enough pressure to maintain its stability.
What is Reverse Methanogenesis?
Reverse methanogenesis is the process where methane is oxidized anaerobically, typically coupled to sulfate reduction. It is carried out by consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria.
How Can Atmospheric Phenomena Influence Nutrient Limitation in the Marine Environment?
Wind can transport nutrients, such as iron, to the marine environment, increasing productivity. Precipitation can also deliver terrestrial nutrients to the ocean through runoff.
Role of Protozoa in the Microbial Loop
Protozoa consume bacteria, releasing nutrients through excretion and respiration. These nutrients are then reused by autotrophic bacteria. This process is a crucial part of the microbial loop, making nutrients accessible to higher trophic levels.
What is an Oligotrophic Environment?
An oligotrophic environment is poor in nutrients. A suitable culture medium for oligotrophic marine bacteria might contain seawater, peptone, yeast extract, and agar.
Particulate Organic Matter (POM) and Dissolved Organic Matter (DOM)
Particulate organic matter (POM) is retained by a 0.22 µm filter, while dissolved organic matter (DOM) passes through.
Why is the Microbial Loop Important for Particulate Organic Matter?
The microbial loop is important because phagotrophic microplankton can consume particulate organic matter, contributing more efficiently to the utilization of matter and energy.