University of Texas BIO 330 Microbial Ecology Final Exam Review Guide

University of Texas BIO 330 Microbial Ecology Final Exam Review Guide Final portion of microbial ecology class review (this is just a review for the lectures since exam 2, the final is comprehensive) What is a plant symbiosis in which the plant acquires its symbionts every generation and how do these symbionts contribute to their hosts? (could be either rhizobia or mycorrhizae) This process is called horizontal symbiosis or horizontal transmission of symbionts. This means the plant does not inherit the symbionts from the parent, but instead acquires them from the environment in each new generation. Rhizobia-Legume Symbiosis - Legumes form a mutualistic relationship with nitrogen-fixing bacteria called rhizobia - Legumes acquire rhizobia via signal molecules, when rhizobia enter they induce the formation of root nodules. The nodules convert atmospheric N2 into ammonia NH3, providing the Legume with a usable nitrogen source. - In return, the plant supplies rhizobia with carbohydrates and protection. Mycorrhizal Fungi-Plant Symbiosis - Fungi are inherited from parent plants, but are acquired from the soil - The fungi colonize plant roots and create arbuscules, which increase nutrient and water absorption - The plant supplies the fungi with carbohydrates produced via photosynthesis. Both of these are mutualistic, but the plants must acquire these microbes from the soil for each generation. So, soil health and microbial diversity is essential in the formation/strength of this relationship. What are the functions of the gut microbiota in cows (and/or in termites?) Ruminants in Cows Cows rely on microbial fermentation in their rumen to break down plant material. The rumen microbiota help to: - Break down cellulose into simpler sugars - Ferment plant material to VFAs which energize the cow - Produce methane - Produce vitamins - And support the immune system This study source was downloaded by from CourseH on :14:31 GMT -05:00 Termites feed on wood, high in lignocellulose but nutrient poor. Their gut microbiota is essential for survival. Their microbiota can: - Breakdown cellulose and lignin - Convert sugars into acetate (energy source) - Fix nitrogen - Produce methane - What is rumen fermentation and what are some consequences for atmospheric composition? Rumen fermentation is the microbial breakdown of plant material in the rumen, the largest chamber of a ruminant’s stomach. It allows cows, sheep, and other plant consumers to digest compounds like cellulose that cannot be broken down on their own. Atmospheric effect: - Methane emissions are increased through rumen fermentation. Every cow emits 100-200 liters of methane per day via burping or gas. Methane is a big contributor to climate change. - Manure from ruminants can contribute to Nitrous Oxide emissions. What is the basis of primary production for communities around hydrothermal vents? In other words, how is CO2 fixed there without light? Microorganisms that grow on inorganic energy sources and fix carbon via chemosynthesis. This is similar to photosynthesis, but the energy is derived from chemical reactions and not sunlight. - Overall, it was found that photosynthesis is still used as Oxygen, a by-product of photosynthesis was needed in a lot of the chemical reactions. - It was found that there are photosynthetic, deep sea hydrothermal bacteria. These bacteria capture geothermal radiation as sunlight, using pigments, chlorosome, and a photosynthetic antennae complex. - This geothermal energy is utilized by animals in vents via symbiosis, consumption of bacteria, and predators that feed on the above. This study source was downloaded by from CourseH on :14:31 GMT -05:00 first originate? Mycorrhizal Fungi enhance plant nutrient uptake via hyphal networks, improve soil structure with glomalin, and promote biodiversity by reducing plant competition by sharing resources through CMNs. - These relationships are thought to originate back 500 million years ago. - Fossil evidence suggests that the earliest land plants formed symbiotic relationships with Glomeromycota fungi which allowed them to colonize terrestrial environments by providing essential nutrients. How do hydrothermal vents impact the chemistry of the oceans? Deep sea hydrothermal plumes are the interface for chemical exchange between the lithosphere and ocean. - Chemistry of the oceans previously unbalanced as excess Mg would enter them through rivers but there would not be enough Mg output (sediment). However, vents allow additional exchange of minerals that increased the chemical output of the ocean floor. - Hydrothermal vents are rich in: iron, manganese, sulfide, hydrogen, methane, and toxic heavy metals - The chemical characteristics come from reactions between sea water and basalt (rock from cooled lava) What is the source of microbes in hydrothermal plumes? How do plumes impact the water column? Deep sea hydrothermal plumes are a significant source of Fe & Mn to the oceans. When these minerals are introduced to deep-sea environments, it can cause “background” bacteria on the sea floor to become more activated and create “plume” communities. These plume communities then facilitate chemosynthesis which becomes an important source of iron to the surrounding water column. What is the chemical/physiological basis for the symbiosis between tube worms (Riftia) and bacteria in their troposphere? Symbionts in Riftia are internal = endosymbiosis This study source was downloaded by from CourseH on :14:31 GMT -05:00 bacteria that provide organic matter to the host - The host provides oxygen, sulfur, and CO2 to the symbionts What is a meromictic lake and how does this impact microbial community structures of lakes and biogeochemisitry in the different seasons? A meromictic lake is a lake in permanent stratification, meaning its layers do not fully mix. Unlike other lakes that undergo seasonal turnover and mixes, meromictic lakes have a deep, isolated later that remains anoxic all year round. Because of the layer stratification, each layer is known to have it’s own distinct microbial communities that drive unique biogeochemical cycles: - Mixolimnion layer (surface): dominated by aerobic bacteria, where photosynthesis occurs. Undergoes freezing in colder months that may reduce surface oxygen exchange - Chemocline layer (middle): supports anaerobic and microaerophilic bacteria. Sulfurreducing bacteria thrives here. During colder months, may have lower photosynthetic activity but sulfur cycling is still active - Monimolimnion layer (deep): dominated by strict anaerobes like methanogens, sulfate-reducing bacteria, and fermentative bacteria. Seasons do not affect its activity. CO2 and methane build up on the bottom due to lack of mixing. What are the most dominant bacteria in lakes? Actinobacteria What are the “killer lakes” and how have they been treated to avoid issues in the future? A killer lake is a meromictic lake that undergoes a rare explosion event that releases all of the methane and carbon dioxide that built up in the bottom layers. The release of these gases cause displacement of air and mass suffocation to people/animals in the area. In order to treat this, pressure from the bottom layer is released from man made pumps tat safely flushes out carbon dioxide and decreases the risk of an explosion. What are the limitations to life in the subsurface? There is low biological activity in the subsurface due to temperature and low energy flux. Relatively small concentrations of electron donors/acceptors and other key nutrients which leads to very slow reaction rates. Overall, there is a slow decline in energy. Rather than turning over biomass in hours to days, it takes centuries to millennia. This study source was downloaded by from