Final Exam Study Guide: Comprehensive Notes

Biogeochemical Cycles

• Carbon Cycle: Microbes decompose organic matter, releasing carbon dioxide (CO_2) into the atmosphere.
• Phosphorus Cycle: Microbes help in the solubilization of inorganic phosphate and mineralization of organic phosphorus, making it available for plants.
• Sulfur Cycle: Microbial activity is crucial for oxidizing and reducing sulfur compounds (e.g., converting sulfates to sulfides and vice versa).
• Nitrogen Cycle - Denitrification: Denitrification is a microbial process that converts nitrates (NO3^-) to nitrogen gas (N2), reducing the availability of nitrogen in ecosystems.
• Nitrogen Fixation in Legumes: Rhizobia bacteria in legume root nodules are responsible for nitrogen fixation, converting atmospheric nitrogen (N2) to ammonia (NH3).

Metagenomics and Environmental Microbes

• Metagenomics: It is the study of genetic material recovered directly from environmental samples. Its advantage is that it allows the study of microbial communities without the need for isolation and cultivation of individual species.
• Microbial Nitrogen Fixation: The process by which microorganisms convert atmospheric nitrogen gas (N2) into ammonia (NH3), which can then be used by plants and other organisms. It's significant because it introduces nitrogen into ecosystems.
• Nitrogen Cycling - Denitrification: Denitrification impacts nitrogen cycling by removing fixed nitrogen from ecosystems, converting it back into atmospheric nitrogen (N_2).
• Harmful Algal Blooms and Dead Zones: Harmful algal blooms lead to increased organic matter, which, when decomposed by microbes, consumes oxygen, creating hypoxic or