Lecture 3: Geomicrobiology

Question 1

What is microbial metabolism and what does it affect?

Answer 1

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.

Question 2

What characteristic of surface waters causes microbial numbers and activity to be higher in this microenvironment?

Answer 2

They are nutrient rich

Question 3

How are microorganisms typically found in soil solutions?

Answer 3

Not free - attached to soil particles in microcolonies

Question 4

What is remarkable about the activity of attached bacteria?

Answer 4

It is much higher than for planktonic bacteria on a cell basis

Question 5

Describe the three stages of biofilm development.

Answer 5

Attachment (adhesion of a few cells to a suitable solid surface)
Colonization (intercellular communication, growth and polysaccharide formation)
Development (further polysaccharide formation)

Question 6

What constitutes Extracellular Polymeric substance, and what is exopolysaccharide formation necessary for?

Answer 6

It is dynamic, so composition depends on the organisms present and environmental conditions. Exopolysaccharide formation is required to stabilize the pillars of the biofilm.

Question 7

pH is highest when O2 is highest during the day, what chemical is found in highest concentrations at night, when more acidic?

Answer 7

Sufide

Question 8

What reaction that promotes precipitation at night, increases the concentration of sulfide, and what carries it out?

Answer 8

Sulphate reduction by sulphate reducers

Question 9

Which of the following processes can be microbially controlled?

• Weathering
• Erosion and deposition
• Cementation and precipitation

Answer 9

Cementation and precipitation - although they can all be influenced and induced by microbes

Question 10

Under Liebergs law of the minimum, what is the total biomass of an organism limited by?

Answer 10

The nutrient present in the lowest concentration relative to the organisms needs

Question 11

According to Shelfords law of tolerance, what is the occurrence and abundance of organisms determined by?

Answer 11

Physico-chemical factors, not just nutrients.

Question 12

What are the major factors that control bacterial growth in the environment?

Answer 12

pH, temperature, Oxygen, water availability

Question 13

What occurs the the bacteria’s minimum temperature?

Answer 13

Membrane gelling, transport processes are so slow that growth cannot occur.

Question 14

What happens at a bacterias maximum temperature?

Answer 14

Denaturing proteins, collapse of the cytoplasmic membrane and thermal lysis

Question 15

Put the optimum growth temperature of the following in order:
Mesophile, extreme thermophilic bacterium, extreme thermophilic archaeon, psychrophile and moderate thermophile.

Answer 15

Psychrophile, mesophile, moderate thermophile, extreme thermophilic bacterium, extreme thermophilic archaeon.

Question 16

How is it possible that bacteria first assembled in the deepsubsurface?

Answer 16

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.

Question 17

When Fe is added as ferric ions to the ocean in order to create a carbon sink, how does this develop?

Answer 17

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.

Question 18

How do microbes under sea ice affect the environment?

Answer 18

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.

Question 19

How is the microbial loop linked to the food web?

Answer 19

It channels energy and carbon to bacteria who are consumed by protozoa, who are consumed by larger zooplankton.

Question 20

What short circuits the loop?

Answer 20

Microphages

Question 21

When is the microbial food chain most important?

Answer 21

When there is little production of larger nonbacterial phytoplankton

Question 22

How do some bacteria / archaea fix carbon into organic matter?

Answer 22

By oxidising inorganic chemicals for energy

Question 23

Why does the SA:V ratio of bacteria affect its growth rate?

Answer 23

Sets potential for metabolism and growth, whilst nutrients, O2 and waste have to pass through the surface.

Question 24

Name some reduced chemical compounds in water from which Archaea can extract energy?

Answer 24

Methane, Hydrogen, sulfide, ammonium.

Question 25

What do heterotrophs feed on?

Answer 25

Autotrophs (who get their energy via photosynthesis converting sunlight into energy)

Question 26

When might the phosphorus cycle be short circuited?

Answer 26

When a mycrohizal funghi-plant relationship occurs, so plant roots take phosphorus from funghi becoming consumers not producers.