Lecture 21

Identify 3 locations where nitrogen-fixing organisms may be found

1. Azobacter 2. Anabaena 3. Cyanobacteria

What are the steps of the carbon cycle?

1. Carbon enters the atmosphere via carbon dioxide 2. Carbon dioxide is absorbed and used as energy. 3. Carbon compounds enter the food chain. 4. Carbon reenters the atmosphere via decomposition. 5. The carbon cycle repeats.

Describe the role of green and purple sulfur in bacteria in the sulfur cycle

green and purple bacteria use H2S to fix carbon

What role do microbes play in the carbon cycle?

Dead organisms are decomposed by microbes in the soil and water

What techniques used for enumeration (discovering) of bacteria from water samples

1. Indicator organisms - present in human feces - survive in water at least as well as the pathogens -simple detection methods 2. Most probable number (MPN) -serial diluation, inoculate 3 to 5 tubes with each diluation -count the # of tubes with positive results (lactose fermentation) 3. Filtration methods -sample is filtered to capture any bacteria present

What are the steps in the nitrogen cycle?

1. Nitrogen fixation (nitrogen is converted into inorganic compounds) 2. Nitrogen assimilation (nitrates and ammonia are assimilated into specific tissue compounds of algae and higher plants) 3. Ammonification (remains of all living things are decomposed by microbes and converted to ammonia) 4. nitrification (transforms soil ammonia into nitrates which plants can incorporate into their own tissues) 5. denitrification (depletes soil nitrates forming free atmospheric nitrogen)

What two processes fuel the carbon cycle?

1. photosynthesis -photoautotrophs use light as an energy source -electrons excite by light from the sun -ETC is used to generate ATP through phosphorylation 2. cellular respiration

Describe the steps of the sulfur cycle

1. sulfur from volcano eruptions, decaying matter and pollution is released to the atmosphere 2. hydrogen sulfide will be absorbed by the clouds and fall back to the earth by rain 3. roots will take up the sulfate in the soil and be used in photosynthesis (animals receive sulfur by eating plants) 4. plans and algae in water will also absorb the sulfate that comes in rain 5. sulfur will evaporate repeating the cycle all over again

Describe the process of eutrophication

addition of organic matter and subsequent removal of oxygen from a body of water 1. nutrients added from far runoff 2. algae grows 3. algae dies 4. bacteria degrade dead algae 5. oxygen concentration from 6. fish die

Describe the role of anaerobic respiration in nitrogen fixation

anaerobic respiration generates energy from the breakdown of organic compounds in the absence of oxygen

Describe the function of nitrogenase in the nitrogen cycle

enzyme that catalyzes the conversion of nitrogen gas to ammonia -sensitive to oxygen (anaerobic) -produces by only a few species of bacteria

What is bioremediation

use of microbes to degrade pollutants -oil spills -drilling acidents in soil -high diversity of bacteria before skill -pseudomonas predominate after spill

What is the difference between coliforms and fecal coliforms

Coliforms: include bacteria that are found in soil, in water that has been influence by surface water, and in human or animal easte (nonpathogenic) Fecal coliforms: groups of total coliforms that are considered to be present specifically in the gut and feces of warm-blooded animals. (ex: E. Coli)

How do microbes work in the nitrogen cycle?

Through the process of ammonification remains of all living things and their waste are decomposed by microbes and converted into ammonia