Exam 3

Question 1

How are the nutrients used by cells cycled in the biosphere?

Answer 1

cycling of elements

Question 2

what is cycling of elements?

Answer 2

all biomass consists of biogenic elements in roughly similar proportions (C, O, N, H, P, K)

Question 3

Cycling often involves changes in ______

Answer 3

oxidation state
organisms contribute to these by redox reactions

Question 4

types of reservoirs to contain elements:

Answer 4

terrestrial
aquatic
atmospheric
living

Question 5

flux is…

Answer 5

the movement of elements between reservoirs (reaching equilibrium over the long term) Human activities threaten to disrupt this equilibrium.

Question 6

monitoring chemical cycling

Answer 6

like detection of atmospheric gases:
air collected in a sealed cylinder is subjected to infrared radiation. If more is absorbed (not detected), moe CO2 is present. Use of mesocosms (artificially enclosed ecosystems) can measure changes over time.

Question 7

radioisotope tracers

Answer 7

molecules are labeled with radioactive elements prior to release in a mesocosm.
determination of the movement of the radioactively labeled elements through the mesocosm can inform researchers on cycling methods.

Question 8

how do microbes influence the cycling of carbon?

Answer 8

the global carbon cycle. A balance is maintained between organic and inorganic carbon reservoirs. complementary metabolic activities of photosynthesis, respiration, and decomposition maintain the balance. Human activity can disrupt these cycles, increasing atmospheric levels of greenhouse gases.

Question 9

If CO2 fixation exceeds respiration, organic matter

Answer 9

accumulates (positive net community productivity)

Question 10

fermentation processed produce___

Answer 10

partially oxidized organic end products (can serve as nutrients for other organisms)

Question 11

methanogenesis

Answer 11

production of methane as a byproduct of biodegradation of organic carbon in an anoxic environment

Question 12

methanogens rely on communities of

Answer 12

interdependent organisms (consortia). Methanogens only use a strict diet of substrates.

Question 13

syntrophic partnership

Answer 13

the give-and-take of the consortia pairings

Question 14

hydrogenotrophic methanogens produce

Answer 14

CH4 from CO2 and H2

Question 15

Acetotrophic methanogens produce

Answer 15

CH4 from acetate (CH3COO-)

Question 16

methanotrophy

Answer 16

metabolism of CH4 into other forms (allowing greater carbon cycling) (can occur aerobically or anaerobically)

Question 17

aerobic methods of methanotrophy are dependent on

Answer 17

methane monooxygenase (MMO) enzyme

Question 18

anaerobic oxidation of methane (AOM) occurs

Answer 18

heavily in marine environments by archaea.

Question 19

The archaea responsible for AOM have yet to be cultured. Thus,

Answer 19

they are termed anaerobic methane oxidizers (ANMEs).
Three distinct phyla recognized by DNA analyses

Question 20

How do microbes influence the cycling of nitrogen?

Answer 20

Nitrogen is most abundant in the atmospheric reservoir (79% of atmospheric gas) but is relatively unusable in N2 form.

Question 21

3 steps of the nitrogen cycle

Answer 21

1. nitrogen fixation
2. nitrification
3. denitrification

Question 22

what is nitrogen fixation?

Answer 22

the conversion of N2 into NH4+ by nitrogenase complex

Question 23

where does nitrogen fixation happen?

Answer 23

it is carried out by aerobic/anaerobic bacteria and archaea

Question 24

nitrifcation

Answer 24

NH4+ is converted into nitrite (NO2-) or nitrate (NO3-)
Different sets of microbes carry out the reactions:
nitrite production takes place in a two-enzyme process using ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase.
Nitrifier takes the reactions one step further, using nitrite and nitrite oxidoreductase (NOR) to produce nitrate.

Question 25

denitrification

Answer 25

use of nitrate/nitrite as a terminal electron acceptor, eventually producing N2 (completing the nitrogen cycle)

Question 26

Haber-Bosch process

Answer 26

can produce synthetic nitrogen fertilizer

Question 27

overuse of fertilizers contributes to:

Answer 27

marine "dead zones" or an imbalance of nitrogen reservoirs and ecosystems

Question 28

How are various biogeochemical cycles connected?

Answer 28

cycling of oxygen

Question 29

cycling of oxygen

Answer 29

actively cycled reservoirs of O2 include O2, CO2, and H2O. It is heavily cycled back and forth between photosynthesis and respiration reactions. it can even be used marginally in anaerobic respiration (SO42- as a terminal electron acceptor) connections between the various cycles are quite common

Question 30

cycling of sulfur and phosphorus

Answer 30

most sulfur and phosphorus is found in rocks and dissolved water. incorporation occurs through terrestrial and aquatic microorganisms into higher-order organisms. decomposition reactions release the elements back into the terrestrial and aquatic systems to complete the cycle. Microbes are critical to these processes as some can metabolize inorganic molecules containing the elements.

Question 31

ecosystems

Answer 31

interactions and exchanges of materials between organisms and their surrounding environment

Question 32

community of organisms

Answer 32

primary producers capture energy through photosynthesis consumers ingest/utilize stored photosynthetic energy decomposers recycle components back into environments (members can be grouped into functional groups called guilds)

Question 33

niche

Answer 33

specific functional role of an organism within an ecosystem

Question 34

the success of microbes in occupying particular niches depends on:

Answer 34

their ability to obtain different nutrients available to produce energy and biomass

Question 35

biofilm

Answer 35

groups/layers of microbes on a surface that interact with and support each other

Question 36

where can biofilms be found?

Answer 36

in nature, but can be of practical importance to humans to what to rid a surface of microbes

Question 37

biofilm formation

Answer 37

often begins with appendages bacteria forming the primary layer on a surface secondary colonizers then join the biofilm together microbes secret exopolysaccharide (eps) which helps protect the biofilm but also helps form water-filled channels for transport of nutrients and wastes

Question 38

How can microbial communities be studied?

Answer 38

two broad objectives: understand biodiversity (the variety of microbial life in nature) and understand the effect of organisms on ecosystems. there is an astonishing amount of cellularity and biomass production from non-eukaryal cells.

Question 39

enrichment cultures

Answer 39

microbes grown in the lab setting may grow slowly or may be rare in a mixed population. enrichment methods promote the growth of desired microbes over undesired cells.

Question 40

winogradsky column

Answer 40

named after russian biologist Sergei Winogradsky; illustrates enrichment in action different microbes flourish in different areas of the column that correspond to different nutritional microenvironments

Question 41

direct sequencing (without growth or cloning)

Answer 41

extraction of DNA from an environmental sample followed by pcr (often for ssu rrna genes) and sequencing sequences compared to databases of known sequences for identification

Question 42

metagenomics

Answer 42

DNA from an environmental sample is used to construct a genomic library genes from this "community" library can then be identified, screened, and compared to other areas.

Question 43

marine ecosystems

Answer 43

over 98% of the oceans's biomass is microbial most of the microbes exist in oligotrophy (using nutrients at very low concentrations) "overfeeding" marine microbes can quickly lead to anoxic water states ("dead zone" formation)