1. Microbes and The Environment
Topic F2, F5
Below: soil bacteria

2. Ecological Roles of Microbes
Producers
Decomposers
Nitrogen Fixers

3. Nitrogen (be able to draw)

4. Nitrogen Cycle
Atmospheric Nitrogen Gas (N2)
Roles of Bacteria
Nitrogen Fixation
Nitrogen Gas  Ammonium ions
Decomposition and Ammonification
Dead stuff  Ammonium ions
Nitrification
Ammonium  Nitrates
Assimilation
Nitrates being used by plants to make proteins and other molecules needed by living things
Denitrification
Nitrates Nitrogen Gas

5. Outline the roles of Rhizobium, Azobacter, Nitrosomonous, Nitrobacter and Pseudomonas denitrificans in the nitrogen cycle.
Rhizobium and Azobacter--nitrogen fixing
Nitrosomonous oxidizes ammonia to form nitrite.
Nitrobacter oxidizes nitrite to form nitrate. (nitrification)
Pseudomonas denitrificans denitrify

6. Describe the conditions that favor dentrification and nitrification.
Denitrification-- decreases soil fertility and plant growth.
water-logged soils.
poor aeration and deficiency of oxygen in the soil.
Nitrification
ploughed soil because then the oxygen gets into the soil and makes it unfavorable for dentrifying bacteria.
This is why soil is aerated

7. Sewage and Bacteria
Outline the consequences of releasing raw sewage and nitrate fertiliser into rivers.
Include:
pathogens
Eutrophication
algal blooms
deoxygenation
increase in biochemical oxygen demand (BOD)

8. The role of saprotrophic bacteria in the treatment of sewage:
Trickling filter beds- consists of a fixed bed of rocks, gravel, wood or plastic media over which
sewage flows downward and causes a layer or film of microbial slime to grow.
This slime has saprotrophic bacteria that decompose the sewage
Reed Bed System- Self contained, artificially engineered, wetland ecosystem for treatment and recycling of sewage.
Saprotrophic bacteria decompose…

9. Reed bed system

10. Bioremediation
Bioremediation -- any process that uses living things or their enzymes to return the natural environment to its original condition after being altered by contaminants
Bioremediation of soil by bacteria…
Selenium
Solvents
Pesticides
Bioremediation of contaminated water by bacteria
Oil spills
Other contaminants
Big picture: Certain bacteria can be used to decompose and/or convert contaminants into less toxic substances.

11. Metabolism of Microbes
Photoautotroph: An organism that uses light energy to generate ATP and produce organic compounds from inorganic substances. (ex. Cyanobacteria, algae etc.)
Photoheterotroph: an organism that uses light energy to generate ATP and obtains organic compounds from other organisms. (ex. Purple and green non-sulfur bacteria)
Chemoautotroph: an organism that uses energy from chemical reactions to generate ATP and produce organic compounds from inorganic substances. (ex. Deep sea vent bacteria)
Chemoheterotroph: an organism that uses energy from chemical reactions to generate ATP and obtain organic compounds from other organisms. (ex. Pathogenic bacteria)

12. Compare photoautotrophs with photoheterotrophs
Energy source: for both = light
Carbon source:
Photosynthesis for photoautotrophs
Food (organic compounds) for photoheterotrophs.

13. Compare chemoautotrophs and chemoheterotrophs
Energy source
Chemoautotrophs use chemical reactions of inorganic compunds to produce ATP
Chemoheterotrophs use organic compounds for energy (respiration)
Carbon source
Chemoautotrophs – use inorganic sources of carbon to make organic substances
Chemoheterotrophs – get organic compounds directly from food.

15. Draw and label: filamentous cyanobacterium (Anabaena)
This image is copyright Dennis Kunkel at
Draw and label: filamentous cyanobacterium (Anabaena)
An example photoautotroph.
Photosynthetic cell– does photosynthesis!
Heterocyst—cell that does nitrogen fixation

16. Biomass can be used as a source of fuels such as methane and ethanol.
Explain the principles involved in the generation of methane from biomass…
Anaerobic conditions (sealed)
3 types of bacteria involved
Type 1: decompose organic material to organic acids and alcohol.
Type 2: Convert organic acids and alcohol into carbon dioxide, hydrogen, and acetate
Type 3: Methanogenic bacteria/archaea such as methanobacillus and methanococcus
Produce methane from CO2,, acetate and Hydrogen.
The methane is then burnt as a source of energy.
The rest of thedigested material is rich in nutrients and used as fertiliser.