1. Option F: Microbes and Biotechnology F.2 Microbes and the Environment

2. F.2.1 List the roles of microbes in ecosystems, including producers, nitrogen fixers, and decomposers Producers: Algae and bacteria with chlorophyll Chemosynthetic bacteria Nitrogen fixers: Bacteria which remove N 2(g) from atmosphere and fix it into nitrates Decomposers: Breakdown organic molecules (detritus) into inorganic nutrients (cycling)

3. F.2.2 Draw and label a diagram of the nitrogen cycle N 2  NH 3

4. F.2.3 State the roles of Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter, and Pseudomonas denitrificans in the nitrogen cycle BacteriaRole in nitrogen cycle RhizobiumNitrogen fixation (root nodules) AzotobacterNitrogen fixation (soil) NitrosomonasNitrification (NH 3  NO 2 - ) NitrobacterNitrification (NO 2 -  NO 3 - ) Pseudomonas denitrificans Denitrification (NO 2 - and NO 3 -  N 2 )

5. F.2.4 Outline the conditions that favour denitrification and nitrification Nitrification: aerobic reactions by autotrophic bacteria Oxygen Neutral pH Warm temperature Denitrification: anaerobic reactions by autotrophic bacteria No oxygen High nitrogen

6. F.2.5 Explain the consequences of releasing raw sewage and nitrate fertiliser into rivers Eutrophication

7. F.2.6 Outline the role of saprotrophic bacteria in the treatment of sewage using trickling filter beds and reed bed systems Trickling filter beds Stone bed 1 – 2 m wide, through which sewage is drained saprotrophic bacteria are on the rocks and feed on the organic matter within the sewage Cleaner water filters out the bottom into another tank, whereby bacteria can be removed and water further treated with chlorine Reed bed systems artificial wetlands to treat waste water As sewage passes through the bed system it is broken down by saprotrophic bacteria living on the root system and in the litter These microbes utilise the sewage for growth nutrient, resulting in cleaner runoff

8. F.2.7 State that biomass can be used as raw material for the production of fuels such as methane and ethanol Biomass: Manure Forest Agricultural products Animal products Ethanol: made using fermentation of starch or cellulose by bacteria and enzymes Methane: made from manure where anaerobic bacteria convert organic matter into methane gas (CH 4 ) and CO 2

9. F.2.8 Explain the principles involved in the generation of methane from biomass, including the conditions needed, organisms involved and the basic chemical reactions

10. 3 types of bacteria are involved: 1.Acidogenic bacteria: organic matter  organic acids + alcohols 2.Acetogenic bacteria: organic acids + alcohols  acetate + (carbon dioxide + hydrogen gas) 3.Methanogenic bacteria: acetate  methane OR carbon dioxide + hydrogen  methane