Lecture 3: Geomicrobiology Flashcards
(26 cards)
What is microbial metabolism and what does it affect?
A chemical reaction in which reactants are removed, and metabolic products added, to the environment. This alters the geochemical environment and the precipitation and dissolution reactions of minerals.
What characteristic of surface waters causes microbial numbers and activity to be higher in this microenvironment?
They are nutrient rich
How are microorganisms typically found in soil solutions?
Not free - attached to soil particles in microcolonies
What is remarkable about the activity of attached bacteria?
It is much higher than for planktonic bacteria on a cell basis
Describe the three stages of biofilm development.
Attachment (adhesion of a few cells to a suitable solid surface)
Colonization (intercellular communication, growth and polysaccharide formation)
Development (further polysaccharide formation)
What constitutes Extracellular Polymeric substance, and what is exopolysaccharide formation necessary for?
It is dynamic, so composition depends on the organisms present and environmental conditions. Exopolysaccharide formation is required to stabilize the pillars of the biofilm.
pH is highest when O2 is highest during the day, what chemical is found in highest concentrations at night, when more acidic?
Sufide
What reaction that promotes precipitation at night, increases the concentration of sulfide, and what carries it out?
Sulphate reduction by sulphate reducers
Which of the following processes can be microbially controlled?
- Weathering
- Erosion and deposition
- Cementation and precipitation
Cementation and precipitation - although they can all be influenced and induced by microbes
Under Liebergs law of the minimum, what is the total biomass of an organism limited by?
The nutrient present in the lowest concentration relative to the organisms needs
According to Shelfords law of tolerance, what is the occurrence and abundance of organisms determined by?
Physico-chemical factors, not just nutrients.
What are the major factors that control bacterial growth in the environment?
pH, temperature, Oxygen, water availability
What occurs the the bacteria’s minimum temperature?
Membrane gelling, transport processes are so slow that growth cannot occur.
What happens at a bacterias maximum temperature?
Denaturing proteins, collapse of the cytoplasmic membrane and thermal lysis
Put the optimum growth temperature of the following in order:
Mesophile, extreme thermophilic bacterium, extreme thermophilic archaeon, psychrophile and moderate thermophile.
Psychrophile, mesophile, moderate thermophile, extreme thermophilic bacterium, extreme thermophilic archaeon.
How is it possible that bacteria first assembled in the deepsubsurface?
UV protection afforded by surface would have been required for early life, therefore it possible that bacteria assembled at the oil/water interface in a hydrophobic medium. H2 is also available by diffusion and was probably the earliest energy form. Temperatures in the subsurface less extreme.
When Fe is added as ferric ions to the ocean in order to create a carbon sink, how does this develop?
Promotes phytoplankton growth, which are then eaten by other organisms, increasing the stream of dead biota and carbonate shells sinking, so more CO2 dissolves in ocean surface waters.
How do microbes under sea ice affect the environment?
If they have strong pigmentation then can alter the albedo of the ice, and as the subglacial environment is anoxic, methane can be biologically produced below the ice.
How is the microbial loop linked to the food web?
It channels energy and carbon to bacteria who are consumed by protozoa, who are consumed by larger zooplankton.
What short circuits the loop?
Microphages
When is the microbial food chain most important?
When there is little production of larger nonbacterial phytoplankton
How do some bacteria / archaea fix carbon into organic matter?
By oxidising inorganic chemicals for energy
Why does the SA:V ratio of bacteria affect its growth rate?
Sets potential for metabolism and growth, whilst nutrients, O2 and waste have to pass through the surface.
Name some reduced chemical compounds in water from which Archaea can extract energy?
Methane, Hydrogen, sulfide, ammonium.
