Topic 12 - Environmental Microbiology I & II

Question 1

What is environmental microbiology and what does this study encompass?

Answer 1

Study of the interactions of microbes in their natural habitat.
Encompasses biotic (living) and abiotic (nonliving) interactions.

Question 2

What is the biosphere?

Answer 2

Includes all ecosystems:

atmosphere, lithosphere, hydrosphere

Question 3

What is the atmosphere?

Answer 3

Gaseous enviro -air

Question 4

What is the lithosphere?

Answer 4

soil/earth’s crust

Question 5

What is the hydrosphere?

Answer 5

water -marine/fresh

Question 6

What is an extremophile? What kind of environments do they live in?
Give 2 real life examples.

Answer 6

Live in extreme environments e.g. pH, temperature, salinity.

1. Deep sea vents 2. Salt lakes

Question 7

Give 2 examples of biotechnology that extremophiles may be used for

Answer 7

1. thermotolerant enzymes (DNA polymerase) for use in PCR

2. Bioremediation: using microbes to remove chemical hazards

Question 8

Define symbiosis

Answer 8

Two differing organisms living in close association that is beneficial to one or both of them

Question 9

Define micorrhiza(e) and why it is a form of mutualism

Answer 9

Fungi living in close association w/ plant roots.

• Fungi extends effective SA of roots via hyphae, which solubilise phosphate and provide it for plants
• Fungi receives carbohydrates from plant

Question 10

Define biogeochemical cycle (BGC)

Answer 10

Recycling (oxidation and reduction) of chemical elements b/w living (biotic) and non-living (abiotic) environment

Question 11

What does soil consist of? Give total volume percentages

Answer 11

Mineral particles (clay, silt, gravel) -50%
Water & air (pore space) -40%
Organic matter (plant & animal derived) -9%
Living organisms -1%

Question 12

Name the 3 layers (horizons) of mature soil and a basic idea of what they contain

Answer 12

A horizon (surface soil) -contains most micro orgamisms
B horizon (subsoil) - contains little organic material and few micro organisms
C horizon (soil base) -organisms low

Question 13

Name the soil inhabitants (top 15cm soil)

Answer 13

Can be chemoheterotrophic or chemoautotrophic
Bacteria
actinomycetes
Fungi
Algae
Protozoa
Worms

Question 14

What is the rhizosphere?

Answer 14

a microecological zone on direct proximity of plant roots

Question 15

What percentage of soil microbes can be cultured from the soil?

Answer 15

10%

Question 16

Describe 6 methods of growing & studying soil microoganisms

Answer 16

1. Isolation & identification
2. Enumeration (counting)
3. Metagenomic sequencing of microbial DNA
4. Biological activity
5. Staining
6. Cultivation on agar

Question 17

Name the 4 different kinds of isolation techniques

Answer 17

selective media -discourage growth of unwanted organisms by inhibitory compounds

enrichment media -addition of a substrate that encourages growth of organisms of interest

MacConkey agar

Enrichment broth

Question 18

A bit about the carbon cycle?

Answer 18

Involves fixation and respiration of carbon.
Microoganisms fix CO2, use it to make organic material, are involved in decomposition & biodegradation, perform methanogenesis (conversion of carbon dioxide into methane).

Question 19

A bit about the nitrogen cycle?

Answer 19

Involves fixation, ammonification, nitrification and denitrification.
Cycling is mainly through biological processes but chemical reactions contribute to fixation.

Question 20

What is ammonification (nitrogen cycle, aka mineralisation)?

Answer 20

Produces ammonia from organic compounds

• Deamination of amino acids releases ammonia gas (NH3)
• NH3 solubilised in presence of H2O to form ammonium ions (NH4)

Question 21

What is nitrification? Describe the 2 steps and the microoganisms they involve

Answer 21

Biological oxidation of ammonia to nitrate.

1. Nitrosomonas converts ammonia to nitrite
2. Nitrobacter uses the nitrite produced by Nitrosomonas to make nitrate

Question 22

What is denitrification? What are the consequences? Which organisms does it involve?

Answer 22

Biological reduction of nitrate or nitrite to nitrogen or nitrous oxide.

• Leads to a decrease in soil fertility
• Occurs at pH <5, at high temps and anaerobic conditions (e.g. water logged soils)
• Involves Pseudomonas, Achromobacter, Bacillus

Question 23

Brief description of nitrogen fixation?

Answer 23

Dinitrogen gas (N2) => nitrogen fixation => ammonia (NH3)

Question 24

Why is waste water a public health and ecological problem?

Answer 24

1. Pathogens in sewage can be transmitted to humans in drinking and recreational water
2. Resistant chemicals or heavy metals may be concentrated in the aquatic food chain
3. Increased nutrients can lead to a massive growth of microbes (eutrophication)

Question 25

What is eutrophication? What is it caused by? What are the effects?

Answer 25

Overabundance of nutrients in lakes or streams.

Caused by:

• the addition of organic matter (e.g. sewage)
• or inorganic matter: phosphates (washing detergents/fertilisers), nitrogen (fertilisers)

Which cause algal or cyanobacterial blooms. Once bloom dies, heterotrophs remove oxygen, killing animals (fish).

Question 26

Describe the Biochemical Oxygen Demand (BOD, an effect of eutrophication)

Answer 26

BOD -a measure of the biologically degradable organic matter in water.
“amount of oxygen required by anaerobic microoganisms to decompose organic matter in a water sample”

Pollutants causing algal blooms cause BOD to rise.
Bacterial decomposition of organic matter uses up O2 dissolved in water.

Question 27

Describe how pathogens are removed from drinking water.

Answer 27

Municipal Water Purification Treatment.
Principally involves coagulation, filtration & disinfection.

1. Water held in reservoir to allow particles to settle
   2a. Water is mixed w/ flocculant
   2b. Floc settles and carries particles out of suspension w/ it.
2. Water undergoes filtration
3. Water is disinfected by chlorination, ozone or UV treatment.
4. Water is ready to be consumed.

Question 28

What is primary sewage treatment?

Answer 28

Removal of solids (screened, settled, floating material removed)
May use flocculants to remove more solids
Primary sludge removed

Question 29

What is secondary sewage treatment?

Answer 29

Mainly biological
Removal of the BOD (biological oxygen demand)
Strong aeration of sewage (activated sludge/trickling filter systems)
Water can be used for irrigation

Question 30

What is tertiary sewage treatment?

Answer 30

Removal of remaining BOD, N and P (secondary effluent) by filtration or activated charcoal
Disinfection (e.g. chlorination)
Water is drinkable

Question 31

What is an activated sludge system?

Answer 31

a process for treating sewage and industrial wastewater’s using air and a biological floc composed of bacteria and protozoans

Question 32

What is a trickling filter?

Answer 32

A coarse treatment system in which wastewater is trickled over a bed of stones or other material covered w/ bacterial biofilms that aerobically breakdown organic waste and produce clean water

Question 33

What is an anaerobic sludge digester? What happens in anaerobic sludge digestion?

Answer 33

An anaerobic process to treat sludge derived from sewage treatment, that encourages conversion to methane & CO2.
Methanogens are encouraged to grow. They help to convert dissolved carbon to gases, so lowering the BOD.