1. Topic F2 – Microbes and the Environment

2. The Nitrogen Cycle -
Microbes occupy a number of niches in ecosystems:
F.2.1
Saprotrophs (decomposers) - they release nutrients trapped in detritus and make it available to ecosystems.
Cyanobacteria - (blue-green algae) and protocists such as algae
Euglena - are photosynthetic and act as producers
The bacteria Rhizobium and Azotobacter can fix nitrogen and convert it to a form that living things can use.

3. F.2.1 Three Roles of microbes in the Environment include:
Nitrogen Fixers
Producers
And Decomposers -
Work alongside plants!
Think algae/cyanobacteria
Decomposers turn waste in to a palatable food source for organisms both in the ocean and in terrestrial environments
Fancy schmancy crash course video (courtesy of Hank Green

4. F.2.3 The Nitrogen Cycle works perfectly!
The choreography of nitrogen fixation to nitrification to denitrification is seamless and amazing
F.2.3
These Rhizobium are an essential part of the process – they “fix” nitrogen from the air and turn it in to nitrogen that is accessible for the plants in the form of Ammonia. How do plants uptake Nitrogen ions from the soil?
Azotobacter are another example of a nitrogen fixing bacteria.
These nitrifying bacteria are Nitrosomonas, which can reside in the soil to turn ammonia into Nitrite
Who then feed the Nitrobacter with the Nitrite, which converts it to Nitrate
Pseudomonas denitrificans is then responsible for the denitrification process – turning Nitrate back into atmospheric nitrogen

5. F.2.3 F.2.4 Wait, what?!?!? Lets try this:
Nitrogen composes 70% of our atmosphere.
Nitrogen in the air is “fixed” to form ammonia by Rhizobium
Ammonia is nitrified to form nitrites via Nitrosomonas
Nitrites are turned into nitrates by Nitrobacter
And finally, Pseudomonas denitrificans converts the nitrates back into atmospheric nitrogen.
Chemical Composition
Where does this happen?
Atmosphere
Roots of plants
Soil/Water
Conditions
that favor Nitrification/
Denitrification
Available sources of oxygen and aerobic soil
Nitrification favors warmer climates/conditions
A neutral pH level
Unlike nitrification, denitrification prefers anaerobic soil

6. F.2.2 Draw this diagram of the nitrogen cycle. Challenge yourself –
Where in this diagram would nitrification occur?
How about denitrification?
Where would you most likely find a large population of Azotobacter?
Also – play around with this tutorial on the nitrogen cycle

7. Case Study – The Dead Zone
Until people get involved…..
F.2.5
Mmmmmm, raw sewage in the water. What are the lasting implications of sewage in the water system?
Eutrophication: is the addition of artificial or natural substances, such as nitrates or phosphates, through fertilizers or sewage to an aquatic environment.
Case Study – The Dead Zone
As you perform the study, pay attention to the following ecosystem changes – hypoxia, algal blooms, Increase in BOD.
Click the image above to access this case study on the implications of sewage dumping into the water system.

8. Trickling Filter Beds Reed Bed Systems
To help mitigate the effects of the extra nitrogen – Sewage Treatment Facilities!
F.2.6
Two major methods –
Trickling Filter Beds Reed Bed Systems

9. F.2.6 What role do saprotrophic bacteria have in the sewage process?
Trickling Filter Bed
-Saprotrophic bacteria form a biofilm over the rocks contained in a Trickling filter system, such that they can digest all of the waste as it moves past them
Reed Filter Bed
-In a reed filter bed, the bacteria are closely linked with the plant root system, and filter the water as it passes by the roots.

10. Biomass can be used at the end of this process to produce fuels such as methane and ethanol. This is known as biofuel production.
F.2.7
Ethanol Production Video - From Corn
Involves the creation and fermentation
of slurry (a corn mash)
Think Topic 3.7!
Methane Production Animation

11. F.2.8 1. 2. 3. Principles of Methane generation from Biomass
Can use either Manure or Cellulose as biomass, and results in
burnable methane gas for electricity generation
Methane generation is done in three steps: 1. 2. 3.
Conversion of organic matter into ethanol and organic acids
Conversion of EtOH and organic acids into Acetate, CO2 and H2 Gas
Methanogenic bacteria convert acetate/CO2 and H2 into Methane Gas
Acetate
Carbon Dioxide
Hydrogen Gas