Microbial Ecology

Question 1

ecosystem

Answer 1

• sum of all the organisms and abiotic factors in a particular environment
• made up of communities

Question 2

population

Answer 2

a group of organisms of the same species in the same place at the same time

Question 3

community

Answer 3

• two or more cell populations coexisting in a certain areas at a given time
• made up of guilds

Question 4

habitat

Answer 4

portion of an ecosystem where a community could reside

Question 5

guild

Answer 5

metabolically related microbial population

Question 6

niche

Answer 6

• habitat shared by a guild

- metabolically related things survive here

Question 7

alpha diversity

Answer 7

• diversity within a community (sample)

- richness, abundance, evenness

Question 8

richness

Answer 8

the total number of different species present in a particular area

Question 9

abundance

Answer 9

the proportion of each species

Question 10

evenness

Answer 10

how similar the abundances are (relative abundance of different species)

Question 11

beta diversity

Answer 11

comparison of samples (between community diversity)

Question 12

gamma diversity

Answer 12

the total species diversity for the different ecosystems within a region (landscape diversity)

Question 13

nitrification

Answer 13

the oxidation of ammonia to nitrate

Question 14

denitrification

Answer 14

the reduction of nitrate to nitrogen gas

Question 15

nitrogen fixation

Answer 15

the reduction of nitrogen gas to ammonia

Question 16

ammonification

Answer 16

the release of ammonia during the decomposition of organic nitrogen compounds

Question 17

anammox

Answer 17

the anaerobic oxidation of ammonia to nitrogen gas

Question 18

What is the role of the nitrogen cycle in nature?

Answer 18

• nitrogen is an essential nutrient for sustaining life

- the nitrogen cycle helps convert inert nitrogen gas into a usable form for plants

Question 19

legume-root nodule symbiosis

Answer 19

• plant-bacterial mutualism
• legumes: plants with seeds that grow in pods such as soybeans, clover, alfalfa, beans, peas, peanuts
• legumes grow well in nitrogen deficient soils
• legumes play a key role in crop rotation by replenishing nitrogen to the soil
• infection of legume roots by nitrogen fixing bacteria rhizobid leads to the formation of root nodules
• legumes with the bacteria grow better in nitrogen deficient soil and do not need nitrogen fertilizers

Question 20

ruminants

Answer 20

• herbivorous animals that possess a rumen

- cows, sheep, goats, etc

Question 21

rumen

Answer 21

digestive organ within which cellulose and other plant polysaccharides are digested by microbes

Question 22

What happens in the rumen?

Answer 22

• rumen contains 10^10-10^11 microbes/g
• cellulolytic microbes hydrolyze cellulose to free sugars
• fermentation of sugars yields volatile fatty acids (acetate, propionate, butyrate) that pass through the rumen wall into the bloodstream and serve as the ruminant’s main energy source
• CO2 and CH4 are released via erucatation (burping)

Question 23

microenvironments

Answer 23

• microbial environments in nature
• complex
• constantly changing
• conditions determined in part by metabolic activities of the community
• resources and growth conditions highly variable and often suboptimal
• competition and cooperation occurs
• “feast or famine” existence

Question 24

biofilms

Answer 24

• assemblages of bacterial cells attached to a surface
• heterogeneous community
• enclosed in adhesive matrix
• trap nutrients for microbial growth and help prevent detachment of cells
• provide protection
• microbes can interact with one another

Question 25

How are biofilms formed?

Answer 25

1. Substratum preconditioning by ambient molecules 2. Cell deposition 3. Cell adsorption/desorption 4. Cell to cell signaling and onset of exopolymer production 5. Convective and diffusive transport of O2 and nutrients 6. Replication and growth 7. Secretion of polysaccharide matrix 8. Detachment, erosion, and sloughing

Question 26

What are problems associated with biofilms?

Answer 26

- can be found on medical devices and can cause disease - biofilms on teeth can cause cavities - biofilms can cause pneumonia - can be found on industrial devices and interfere with fluid distribution - potential for corrosion

Question 27

quorum sensing

Answer 27

- the regulation of gene expression in response to fluctuations in cell population density - bacteria secrete chemical messengers that affect bacterial behavior - ex: can make cells competent so that they can uptake DNA, increasing genetic diversity - ex: to kill other cells to get their DNA or use them as a source of nutrients - bacteria act differently on their own than they do in a biofilm