exam 3 study guide Flashcards
(42 cards)
what are reservoirs? what are the 4 major reservoirs?
where elements are contained; terrestrial, aquatic, atmospheric, living
what 2 reactions affect oxygen cycling the most? can anaerobic bacteria affect this cycling?
photosynthesis and respiration; yes
what is nitrogen fixation?
conversion of N2 into NH4+ by nitrogenase complex carried out by aerobic/anaerobic bacteria and archaea
what is nitrification?
NH4+ is converted into nitrite or nitrate where different sets of microbes carry out the reactions.
nitrite production takes place in a two-enzyme process using ammonia monooxygenase and hydroxylamine oxidoreductase.
what is denitrification?
use of nitrate/nitrite as terminal electron acceptor, eventually producing N2 (completing the nitrogen cycle)
what is methanogenesis?
production of methane as a byproduct of biodegradation of organic carbon in an anoxic environment
what is the importance of methane monooxygenase (mmo) enzyme for methanotrophs?
aerobic methods of methanotrophy are dependent on the methane monooxygenase enzyme
what reactions affect carbon cycling?
Influenced by processes such as photosynthesis, respiration, decomposition, and methanogenesis. These balance the atmospheric CO₂ levels and impact global climate.
phosphorus and sulfur are limiting elements; where can they be found?
found in rocks and dissolved in water
what are the steps of biofilm formation?
formation begins with the appendaged bacteria forming the primary layer on a surface. secondary colonizers then join the biofilm. together the microbes secret exopolysaccharide which helps protect the biofilm but also helps form water-filled channels for transport of nutrients and wastes.
what are the advantages of biofilms? how is it regulated?
Offer protection from environmental stresses (e.g., antibiotics, immune cells), allow for nutrient sharing, and provide a structured environment for gene exchange. Biofilm regulation involves quorum sensing, where bacteria communicate based on population density.
ecosystem
Interactions and exchanges of materials between organisms and their surrounding environment
Community of organisms
Primary producers capture energy through photosynthesis.
consumers ingest/utilize stored photosynthetic energy.
decomposers recycle components back into environments.
Members of communities can be grouped into functional groups called guilds.
niche
specific functional role of an organism within an ecosystem
As microbes are very small, they tend to exist in microenvironments.
Conditions can change dramatically in microenvironments over short distances.
Success of microbes in occupying particular niches depends on their ability to obtain different nutrients there to produce energy and biomass.
consortia
Cooperative groups of microorganisms working together.
community
A collection of coexisting microbial populations.
population
All individuals of a single microbial species in an area.
microbes make up the majority of the biomass in the ocean. what role do viruses play?
Microbes dominate marine biomass, and viruses control microbial population dynamics by infecting and lysing host cells, releasing nutrients back into the environment. Probably 10x more viruses exist in the oceans than microbes.
Little is known about these viruses, their reproduction cycles, and their ecological impacts.
What little is known shows viruses of cyanobacteria dominating the surface zone areas.
Viruses most likely liberate nutrients from cyanobacteria, making them available for heterotrophic microbes in deeper waters.
what did the winogradsky column demonstrate?
(named after the Russian biologist Sergei Winogradsky) illustrates enrichment in action.
are we limited to only studying organisms we can grow in the laboratory? if not, what other techniques can be used to study them?
DNA sequencing, metagenomics, and stable isotope probing allow for studying uncultured microbes, providing insights into microbial diversity and function.
enrichment media can be useful for growing organisms that may be more difficult to study. why?
Different microbes flourish in different areas of the column that correspond to different nutritional microenvironments.
When microbes can be grown in the lab setting, they may grow slowly or may be rare in a mixed population.
Enrichment methods promote growth of desired microbes over undesired cells.
does enrichment process give us a true analysis of the bacteria in the environment?
No, enrichment doesn’t provide a complete picture. It uses specific conditions to favor certain bacteria, which can:
Exclude slower-growing or interaction-dependent microbes.
Overrepresent fast-growing species.
Alter microbial behavior compared to natural environments.
Enrichment is helpful for isolating specific bacteria but misses the full diversity and function of the community.
how can microbes benefit plants? how do plants benefit microbes?
How microbes benefit plants:
Provide nutrients (e.g., nitrogen, phosphorus)
Promote growth through hormones
Protect against pathogens
How plants benefit microbes:
Supply food (sugars from roots)
Create a stable habitat (rhizosphere)
what is a rhizosphere? how is it different from other areas of the soil?
Rhizosphere:
The soil zone around plant roots where microbes are highly active.
Difference from other soil:
Contains more nutrients from root exudates (sugars, acids) that attract and feed microbes, leading to higher microbial diversity and activity.
what are the dangers of anoxic waters (“dead zones”), and how does this occur?
Dangers of Anoxic Waters (“Dead Zones”):
Lack of oxygen kills fish and marine life.
Disrupts ecosystems and harms fishing industries.
How It Occurs:
Excess nutrients (from fertilizers, runoff) cause algae blooms.
When algae die, decomposition uses up oxygen, creating low-oxygen conditions.
