Topic 12 - Environmental Microbiology I & II Flashcards
What is environmental microbiology and what does this study encompass?
Study of the interactions of microbes in their natural habitat. Encompasses biotic (living) and abiotic (nonliving) interactions.
What is the biosphere?
Includes all ecosystems:
atmosphere, lithosphere, hydrosphere
What is the atmosphere?
Gaseous enviro -air
What is the lithosphere?
soil/earth’s crust
What is the hydrosphere?
water -marine/fresh
What is an extremophile? What kind of environments do they live in?
Give 2 real life examples.
Live in extreme environments e.g. pH, temperature, salinity.
- Deep sea vents 2. Salt lakes
Give 2 examples of biotechnology that extremophiles may be used for
- thermotolerant enzymes (DNA polymerase) for use in PCR
2. Bioremediation: using microbes to remove chemical hazards
Define symbiosis
Two differing organisms living in close association that is beneficial to one or both of them
Define micorrhiza(e) and why it is a form of mutualism
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
Define biogeochemical cycle (BGC)
Recycling (oxidation and reduction) of chemical elements b/w living (biotic) and non-living (abiotic) environment
What does soil consist of? Give total volume percentages
Mineral particles (clay, silt, gravel) -50%
Water & air (pore space) -40%
Organic matter (plant & animal derived) -9%
Living organisms -1%
Name the 3 layers (horizons) of mature soil and a basic idea of what they contain
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
Name the soil inhabitants (top 15cm soil)
Can be chemoheterotrophic or chemoautotrophic Bacteria actinomycetes Fungi Algae Protozoa Worms
What is the rhizosphere?
a microecological zone on direct proximity of plant roots
What percentage of soil microbes can be cultured from the soil?
10%
Describe 6 methods of growing & studying soil microoganisms
- Isolation & identification
- Enumeration (counting)
- Metagenomic sequencing of microbial DNA
- Biological activity
- Staining
- Cultivation on agar
Name the 4 different kinds of isolation techniques
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
A bit about the carbon cycle?
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).
A bit about the nitrogen cycle?
Involves fixation, ammonification, nitrification and denitrification.
Cycling is mainly through biological processes but chemical reactions contribute to fixation.
What is ammonification (nitrogen cycle, aka mineralisation)?
Produces ammonia from organic compounds
- Deamination of amino acids releases ammonia gas (NH3)
- NH3 solubilised in presence of H2O to form ammonium ions (NH4)
What is nitrification? Describe the 2 steps and the microoganisms they involve
Biological oxidation of ammonia to nitrate.
- Nitrosomonas converts ammonia to nitrite
- Nitrobacter uses the nitrite produced by Nitrosomonas to make nitrate
What is denitrification? What are the consequences? Which organisms does it involve?
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
Brief description of nitrogen fixation?
Dinitrogen gas (N2) => nitrogen fixation => ammonia (NH3)
Why is waste water a public health and ecological problem?
- Pathogens in sewage can be transmitted to humans in drinking and recreational water
- Resistant chemicals or heavy metals may be concentrated in the aquatic food chain
- Increased nutrients can lead to a massive growth of microbes (eutrophication)
