Lecture 21: Microbes in Ecosystems

Question 1

Abiotic processes

Answer 1

nonliving

Question 2

Biotic processes

Answer 2

Nutrient cycling

Question 3

Biogeochemical Cycling

Answer 3

• microbes on earth’s surface contribute to rapid nutrient cycling, while deep surface microbes impact elemental cycling over geological periods

Question 4

Carbon cycle

Answer 4

• Carbon is continuously transformed from one form to another
• CO2 is reduced to methane (CH4)

Question 5

Carbon Cycle-Reduction to methane

Answer 5

• 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

Question 6

Nitrogen Cycle

Answer 6

• Nitrogen species serve as electron acceptors in
  anaerobic respiration or as electron donors in chemolithotrophy

Question 7

Nitrogen fixation

Answer 7

• 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

Question 8

Nitrogen fixation&Nitrifaction

Answer 8

• transmitted by respiratory droplets
• Product of nitrogen fixation
  is ammonia (NH3)
• Immediately incorporated into organic matter

Question 9

Nitrification

Answer 9

• ammonium donates electrons to become other nitrogen compounds

Question 10

Assimilatory nitrate reduction

Answer 10

• Fate of NO3-
• reduced and incorporated into microbial and plant cell biomass

Question 11

Dissimilatory nitrate reduction

Answer 11

• Fate of NO3-
• nitrate is fully reduced to N2, nitrogen is removed from ecosystem and returned to
  atmosphere
• denitrification

Question 12

The phosphorus cycle

Answer 12

• 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

Question 13

The sulfur cycle

Answer 13

• Depending on oxidation state of sulfur species, it can serve as electron acceptor, donor, or both

Question 14

Assimilatory sulfate reduction

Answer 14

• sulfur cycle
• Reduction of sulfate for use in amino acid and protein
  biosynthesis

Question 15

Dissimilatory sulfate reduction

Answer 15

• Sulfur cycle
• The use of sulfate as a terminal electron acceptor (anaerobic respiration)

Question 16

Global Climate Change

Answer 16

• 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

Question 17

Greenhouse gases

Answer 17

• 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

Question 18

Greenhouses gases- Nitric oxides

Answer 18

• Runoff may cause eutrophication which disturbs the ecosystem balance
• Nitrification/denitrification cycles fueled by fertilizer are responsible for high Nox levels

Question 19

Eutrophication

Answer 19

• 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

Question 20

Disruption of global nutrient cycles

Answer 20

• 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

Question 21

Oceanography

Answer 21

study of marine systems and
the biological, physical, geological, and chemical factors that impact biogeochemical cycling, water circulation, and climate

Question 22

Limnology

Answer 22

• investigation of aquatic systems within continental boundaries, including glaciers, groundwater, rivers,
  streams, and wetlands

Question 23

Primary produces- Marine environment

Answer 23

• 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.

Question 24

Harmful Algal Blooms

Answer 24

• 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

Question 25

Sargasso Sea

Answer 25

• 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

Question 26

Deep Ocean Sediments

Answer 26

• 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

Question 27

Freshwater microorganisms

Answer 27

• lakes
• Dominated by planktonic
  microbes and
  invertebrates

Question 28

Oligotrophic lakes

Answer 28

• Mountain lakes fed from infertile land
• Explains why lakes tend
  to be clear.

Question 29

Eutrophic lakes

Answer 29

• Low level lakes that catch
  water from fertile, cultivated soils
• nutrient rich
• high level of planktonic growth and the lakes appear murky

Question 30

terrestrial microorganisms

Answer 30

• 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

Question 31

Soil Microorganisms

Answer 31

• direct contact
• 35 different phyla of
  bacteria in soil
• Soil populations play roles in degradation of hydrocarbons, plant materials, and soil humus

Question 32

Geosmin

Answer 32

• odor causing compound which gives soil earthly odor

Question 33

Microbe Plant interactions

Answer 33

• 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

Question 34

Mycorrhizal fungi

Answer 34

• 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

Question 35

Endomycorrhizae

Answer 35

• mycorrhizal fungi
• fungi that enter the root cells

Question 36

Ectomycorrhizae

Answer 36

• mycorrhizal fungi
• fungi that remain extracellular
• form a sheath of interconnecting filaments (hyphae) around roots

Question 37

Rhizobia

Answer 37

• 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

Question 38

Plant Pathogens

Answer 38

• 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