WK - Microbial Diversity II Flashcards
How are microbes completely dependent on each other? (3)
- Microbes play critical roles in both health and the environment.
- They are responsible for every biogeochemical cycle.
- Fungal highways support microbial relationships (e.g., fungi provide transport, bacteria offer nutrients like thiamine)
What is the relationship between microbes and fungi? (3)
- Microbes and fungi engage in mutualism or commensalism.
- Fungi offer a “highway” for bacteria to travel through, while bacteria provide compounds like thiamine (B1).
- Mycorrhizal fungi, such as AMF, feed bacteria in exchange for phosphorus.
Biocrusts are consortia of…..? (6)
- Consortia of cyanobacteria
- Algae
- Fungi
- Lichens
- Mosses
- Liverworts
What are 2 additional features of biocrusts?
- They are typically early colonisers that reshape environments
- Biocrusts add carbon and nitrogen to the environment, supporting other organisms
What are the functions of biocrust ecosystems? (3)
- Reduce wind and water erosion (i.e. binds the soil)
- Helps with water retention
- Reduced UV pressure on underlying soil (some microbes produce scytonemin)
What are characteristics of biofilms? (5)
- Multi-species consortia
- Release of extracellular polymeric substances
- Resistant to environmental perturbation
- Resistant to antibiotics
- Predation protection
What is soil from a microbial perspective? (3)
- Soil is the weathered end product of climate and microbial decomposition
- Rich in organic matter and microbes
- Source of nutrients for vegetation
Soil from a Microbial perspective (1) vs from a Ecosystem perspective (3)
From a Microbial perspective:
- High levels of organic matter make surface soils and ideal microbial habitat
From Ecosystem Perspective:
- Microbes are fundamental biotic elements in soils
- Decompose organic matter
- Recycle and regenerate nutrients
Where do soil microbes live, and why is soil important to them? (3)
1) Soil aggregates – macro and micro
2) Individual soil particles aggregate to form soil architecture – held together by “microbial gums” (e.g. polysaccharides)
3) In between these aggregates are voids (pore space) allow for movement of air, water, microbes
- Critical for microbes
- Create heterogeneous environment
80-90% of microbes attach to soil surfaces, while 10-20% live in pores, which protect them from predators.
How does soil water content affect microbial processes? (3)
- In wet soils, oxygen diffusion is limited, impacting microbial respiration
- In dry soils, water limitations affect the transport of nutrients like carbon and oxygen
- In very dry soils, microbial activity may halt altogether.
What is the phyllosphere and the rhizosphere in plants?
Phyllosphere: The above-ground surface of plants colonized by microbes.
Rhizosphere: The thin layer of soil around plant roots where microbial activity is concentrated.
What are 4 types of ocean microbes?
- Planktonic cells
- Cells at depth
- Host-associated
- Sediment
How do microbes participate in the biological pump of the ocean? (3)
- Phytoplankton photosynthesize, then die or are consumed by zooplankton
- Resulting particulate organic carbon (POC) sinks to the ocean floor, removing carbon from the atmosphere for millennia
- Alternatively, the microbial loop returns carbon to the food web through microbial respiration and grazing by protists.
What is the phycosphere, and why is it important? (3)
- The phycosphere is the area around phytoplankton cells
- It serves as a hotspot for metabolic activity and nutrient exchange
- This area is similar to the rhizosphere in plants and involves chemotaxis.
How are animals dependent on microbes for nutrients and what are the two types of relationships?
Many higher organisms are dependent on microbes for nutrients
- Gut microbes = nutrients
Two types of relationships
1) Pathogenic interactions
2) Symbiotic interactions
- Commensal
- Mutualistic
- Parasitic
What are organ-specific microbiomes? (3)
- Each organ (e.g., gut, skin) has a unique microbiome
- Gut microbiome is the most studied, crucial for digestion and pathogen prevention
- Microbial dysbiosis (i.e. microbial imbalance) can lead to infections and diseases.
What roles do mutualistic microbes play in the animal gut? (3)
- Aid in digestion of some difficult to solubilize materials (e.g. cellulose)
- Prevent infection/colonization by pathogens
- Release additional nutrients, vitamins during digestions
What is Wolbachia, and how does it interact with insects? (3)
Wolbachia are inherited bacterial parasites that infect ~65% of insect species.
They manipulate insect reproduction by causing:
- Cytoplasmic incompatibility (CI).
- Feminization.
- Male killing.
What are termite gut mutualisms, and why are they important? (3)
- Termites play a key role in decomposing lignocellulose (woody material)
- Their gut microbiome converts 95% of cellulose into simple sugars within 24 hours
- Gut bacteria also fix nitrogen, providing bioavailable nitrogen to termites, crucial for their nutrition.
What is an example of a parasitic fungus? (2)
Zombie ants
- Ophiocordyceps unilateralis is a parasitic fungus that infects ants
- Infection involves the alteration of ant behaviour
What are extremophiles, and why is the term “extreme” relative? (2)
- Extremophiles are microbes that thrive in conditions detrimental to most life (e.g., high temperature, salinity, acidity).
- What’s “extreme” for us might be normal for these organisms.
What are Acidophiles and Alkaliphiles?
Acidophiles
Extreme acidophiles grow in environments with pH < 3, but moderate acidophiles can tolerate pH 3-5
- Environment where proteins and cell membranes are readily hydrolysised and denatured
Alkaliphiles
Exist in high alkaline environments (pH > 9)
* Alkaline lakes
Pump IN hydrogen ions
What are 2 types of tolerance mechanisms for Acidophiles?
Tolerance mechanisms:
1) Membrane transport systems to pump protons (H+) out of the cytoplasm and/or pump counter ions into the cell to maintain relatively neutral intracellular pH conditions (don’t need specialised proteins)
2) Rather than pumping in or out ions, some microbes survive with an acidified cytoplasm because their proteins are stable in acidic conditions (e.g. Acetobacter aceti and Sulfolobus acidocaldarius)
- Proteins with acidic residues
- Binding metal cofactors
What are Halophiles and what are their challenges (2) and adaptation mechanisms (2)?
Halophiles thrive in salty environments (3-30% salinity)
Challenges:
- High internal salt levels = protein aggregation
- Cell desiccation from osmosis
Adaptation mechanisms include:
- Osmoprotectants (e.g., betaines, amino acids) to balance osmotic pressure.
- Pumping inorganic salts into their cytoplasm to maintain turgor pressure and prevent desiccation
Need to have proteins that are adapted to high salt (e.g. charged amino acids on proteins to retain water molecules)
