Option F:Microbes and Biotechnology

F.2 Microbes and the Environment

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 N2(g) from atmosphere and fix it into nitrates

Decomposers:•Breakdown organic molecules (detritus) into inorganic nutrients (cycling)

F.2.2 Draw and label a diagram of the nitrogen cycle

N2 NH3

F.2.3 State the roles of Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter, and Pseudomonas denitrificans in the nitrogen cycle

Bacteria Role in nitrogen cycle

Rhizobium Nitrogen fixation (root nodules)

Azotobacter Nitrogen fixation (soil)

Nitrosomonas Nitrification (NH3 NO2-)

Nitrobacter Nitrification (NO2- NO3

-)

Pseudomonas denitrificans

Denitrification (NO2- and NO3

- N2)

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

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

Eutrophication

F.2.6 Outline the role of saprotrophic bacteria in the treatment of sewage using trickling filter beds and reed bed systemsTrickling 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

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 (CH4) and CO2

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

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

3 types of bacteria are involved:1.Acidogenic bacteria: organic matter organic acids + alcohols2.Acetogenic bacteria: organic acids + alcohols acetate + (carbon dioxide + hydrogen gas)3.Methanogenic bacteria: acetate methane OR carbon dioxide + hydrogen methane