Lecture 21: Microbes in Ecosystems Flashcards
1
Q
Abiotic processes
A
nonliving
2
Q
Biotic processes
A
Nutrient cycling
3
Q
Biogeochemical Cycling
A
- microbes on earth’s surface contribute to rapid nutrient cycling, while deep surface microbes impact elemental cycling over geological periods
4
Q
Carbon cycle
A
- Carbon is continuously transformed from one form to another
- CO2 is reduced to methane (CH4)
5
Q
Carbon Cycle-Reduction to methane
A
- CO2 can be reduced
anaerobically to methane
(CH4) - Methane is oxidized
aerobically by bacteria or
anaerobically by archaea - Methane sediments found
in rice paddies, ruminant
animal stomachs, coal
mines, sewage treatment
plants, landfills, and
marshes
6
Q
Nitrogen Cycle
A
- Nitrogen species serve as electron acceptors in
anaerobic respiration or as electron donors in chemolithotrophy
7
Q
Nitrogen fixation
A
- Reduction of inorganic N2
to organic form (NO3
2-, NH3) - Carried out by some bacteria and archaea
- Can be carried out under both oxic and anoxic
conditions
8
Q
Nitrogen fixation&Nitrifaction
A
- transmitted by respiratory droplets
- Product of nitrogen fixation
is ammonia (NH3) - Immediately incorporated into organic matter
9
Q
Nitrification
A
- ammonium donates electrons to become other nitrogen compounds
10
Q
Assimilatory nitrate reduction
A
- Fate of NO3-
- reduced and incorporated into microbial and plant cell biomass
11
Q
Dissimilatory nitrate reduction
A
- Fate of NO3-
- nitrate is fully reduced to N2, nitrogen is removed from ecosystem and returned to
atmosphere - denitrification
12
Q
The phosphorus cycle
A
- Phosphorus required for ATP, nucleic acids, and some lipids and polysaccharides
- Thought to be derived only from weathering of phosphate-containing rocks
- Phosphonates (C—P bond) are the organic form and source for phosphorus for marine microorganisms
13
Q
The sulfur cycle
A
- Depending on oxidation state of sulfur species, it can serve as electron acceptor, donor, or both
14
Q
Assimilatory sulfate reduction
A
- sulfur cycle
- Reduction of sulfate for use in amino acid and protein
biosynthesis
15
Q
Dissimilatory sulfate reduction
A
- Sulfur cycle
- The use of sulfate as a terminal electron acceptor (anaerobic respiration)
16
Q
Global Climate Change
A
- Biogeochemical cycling out of balance
- Microbial activity is critical in maintaining the dynamic equilibrium that defines our biosphere
- Reflects the changes in patterns of wind, precipitation, and ocean and atmospheric temperatures that the Earth is now experiencing
17
Q
Greenhouse gases
A
- climate change driver
- Trap heat reflected from the
Earth’s surface in the atmosphere, rather than allowing it to radiate into space - Gases accumulate if the rate
these gases enter the atmosphere exceeds the rate by which the natural carbon and nitrogen cycles can remove them - Accumulation of these gases has resulted in global warming
18
Q
Greenhouses gases- Nitric oxides
A
- Runoff may cause eutrophication which disturbs the ecosystem balance
- Nitrification/denitrification cycles fueled by fertilizer are responsible for high Nox levels
19
Q
Eutrophication
A
- Ecological enrichment of nitrogen/phosphorus
- When occurring naturally,
eutrophication is a very slow process in which nutrients, especially phosphorus compounds and organic matter, accumulate in water bodies from weathered rock - Excess fertilizer causes it to happen more quickly
20
Q
Disruption of global nutrient cycles
A
- Global climate change
- Measured over decades
- Parameters: 1. Surface temperature on land and sea, and in the atmosphere 2. rates of precipitation 3. frequency of extreme weather
21
Q
Oceanography
A
study of marine systems and
the biological, physical, geological, and chemical factors that impact biogeochemical cycling, water circulation, and climate
22
Q
Limnology
A
- investigation of aquatic systems within continental boundaries, including glaciers, groundwater, rivers,
streams, and wetlands
23
Q
Primary produces- Marine environment
A
- Autotrophic organisms that fix CO2, providing organic carbon
- In open ocean, all organic carbon is the product of microbial autotrophy
- In streams and lakes, macroscopic algae and terrestrial runoff provide organic carbon.
24
Q
Harmful Algal Blooms
A
- When a single microbial species grows at the expense of other organisms in the community
- Red tide: water becomes red or pink from growth of pigmented algae.
- Can kill fish or marine mammals
25
Sargasso Sea
- oceanic surface microbes
- SAR11 (Sargasso Sea) are the most abundant organisms on Earth
- SAR11 make up 25 – 50% of the microbial cells in coastal and open ocean
- Produces proteorhodopsin pump to supplement ATP pools in nutrient-depleted waters
26
Deep Ocean Sediments
- largest microbial biomass is under the sea
- Recent studies on ocean sediments (benthos) have revealed information on microbial communities
- Previously thought to be devoid of life, we now know that ocean sediments are the Earth’s largest microbial habitat
27
Freshwater microorganisms
- lakes
- Dominated by planktonic
microbes and
invertebrates
28
Oligotrophic lakes
- Mountain lakes fed from infertile land
- Explains why lakes tend
to be clear.
29
Eutrophic lakes
- Low level lakes that catch
water from fertile, cultivated soils
- nutrient rich
- high level of planktonic growth and the lakes appear murky
30
terrestrial microorganisms
- Microbial diversity in soil exceeds that of any other habitat on Earth
- Microhabitats created by interdependent biological, physical and chemical factors
- soil particles
- pore space
- provide optimum environment for microbial growth
31
Soil Microorganisms
- direct contact
- 35 different phyla of
bacteria in soil
- Soil populations play roles in degradation of hydrocarbons, plant materials, and soil humus
32
Geosmin
- odor causing compound which gives soil earthly odor
33
Microbe Plant interactions
- 3 relationships:
1. Commensal relationship (0/0)
2. Mutualistic relationship (+/+)
3. The microbe can be a plant pathogen and harms the host (+/-).
- Once relationship is initiated, microbes and plants monitor physiology of their partner and adjust actions accordingly
34
Mycorrhizal fungi
- Mutualistic fungus-plant
associations
- colonize plant roots
- Are not saprophytic, instead use photosynthetically derived carbohydrate from the host
- Provide enhanced nutrient uptake for plant
- Can increase a plant’s competitiveness
35
Endomycorrhizae
- mycorrhizal fungi
- fungi that enter the root cells
36
Ectomycorrhizae
- mycorrhizal fungi
- fungi that remain extracellular
- form a sheath of interconnecting filaments (hyphae) around roots
37
Rhizobia
- bacterial mutualism with plants
- Several α-proteobacterial genera contain species able to form nitrogen-fixing nodules with legumes.
- Convert gaseous nitrogen (N2) to ammonia (NH3).
- Vital part of the global N cycle
38
Plant Pathogens
- parasitic (+/-)
- Biotrophic fungi assimilate living plant material but do not kill hosts
- Necrotrophic fungi infect (and kill) host by releasing toxins.
- Many bacteria are also plant
pathogens
- Phytophthora infestans: öomycete caused the Irish potato famine
