LECTURE 20 - Planetary health (Microbes and Ecosystems)

Question 1

The four laws of Ecology

Answer 1

• Everything is connected
• Everything must go somewhere
• Nature knows best
• There’s no such thing as a free lunch
• barry commoner

Question 2

Autotrophs in the Carbon cycle – Algae

Answer 2

Autotrophs in the Carbon cycle – Algae

• Autotroph: “Self-feeder” – uses CO 2 as carbon source
  –> simple, inorganic carbon dioxide (CO2) from the atmosphere and convert it into complex, organic carbon compounds.
• May use light as energy source (photoautotrophs) or may use
  chemical energy sources (chemoautotrophs)
• Autotrophs convert inorganic C to organic C, act as
  “SINKS” for CO 2  act to limit climate change

Question 3

photoautotrophs

Answer 3

such as algae
–> photosynthesis: they capture sunlight using pigments like chlorophyll –> convert it into chemical energy.

This energy is used to take in carbon dioxide from the air and convert it into organic carbon compounds, like sugars and starches.

In essence, they are using solar energy to “fix” carbon from the atmosphere.

Question 4

chemoautotrophs

Answer 4

such as methanogens
use chemical energy sources to fix carbon dioxide into organic compounds.
They don’t rely on sunlight but still play a crucial role in carbon cycling in unique environments.

Question 5

Methanogens

Answer 5

autotroph
Consume CO 2 and H 2, produce methane (CH 4)
–> chemoautotrophs: CO 2 is C source, H2 is energy source
Methanogens: an example of archaea
* Impact on climate change: act as sinks for CO 2 (good as absorbs CO2), but act
as sources of CH 4 (very bad, releases CH4!)…. Overall = bad.

ANAEROBIC. They are killed by oxygen !
–> instead ‘breathe’ CO2 and exhale CH 4

• This limits methanogens to oxygen-
  free habitats (deep sediments, soil
  micro-niches, animal gut)

Methanogens associate with protists in the termite gut

Question 6

Methanotrophs

Answer 6

Heterotrophs
Consume methane, produce CO 2
* Are heterotrophs*: Methane (the simplest organic compound) acts as both their carbon source and energy source
* Impact on climate change: act as sinks for CH 4 (very good!), but
act as sources of CO 2 (bad)…. Overall = good.

Domain BACTERIA

• Methanotrophs are useful for removing methane
• They also attack other more toxic pollutants e.g. trichloroethene (TCE)
  has an enzyme called MMO to degrade TCE= methane
  monooxygenase enzyme –> which has a broad substrate range

Question 7

Decomposers

Answer 7

• Heterotroph: “Other-feeder” – needs to eat other organisms, or other organic carbon sources; these also supply energy
• Heterotrophs are SOURCES of CO 2 [releases co2 into the atmosphere] –> bad for climate change
• Decomposers: recycle dead cells back to CO2.

Question 8

Predators

Answer 8

• Protists (protozoa type) are often predators of other microbes; these predators include ciliates, flagellates & amoebae (Amoebae engulfing bacteria).
• Not all protists are predators, some are ‘detritivores’ (scavengers : dead organic matter, such as decaying plant and animal material), and some are photosynthetic

Question 9

pollutant degraders

Answer 9

• Methanotrophs are just one example of bacteria that grow on hydrocarbons as their carbon and energy source.
• Hydrocarbon-degrading bacteria (including methanotrophs) are very useful for “bioremediation”
• Hydrocarbon-degrading bacteria are heterotrophs that specialise in eating ancient fossilised organic carbon
• These are similar to other decomposers, except that they contain special enzymes which can attack hydrocarbons

Question 10

bioremediation

Answer 10

the cleanup
of pollution by microbes

Question 11

Auto/Hetero-troph interactions - Coral symbiosis

Answer 11

• Corals are primitive animals (Phylum Cnidaria), which depend on symbiotic microscopic algae to supply them with food
• Algae: photoautotrophs, convert CO 2 + light –> sugars
• Coral: heterotrophs, convert sugars –> CO2

atmospheric CO2 –> algal symbiont –> coral symbiont –> co2 –> back to algal symbiont

Question 12

Symbiotic and Symbiont def

Answer 12

the nature of a relationship between two organisms from different species that live together in close physical proximity.
There are three main types of symbiotic relationships:

1. Mutualism
2. Parasitism
3. Commensalism

symbiont : a noun used to refer to one of the organisms involved in a symbiotic relationship.

Question 13

Auto/Hetero-troph interactions - Lichen symbiosis

Answer 13

LICHENS are primary producers in some terrestrial habitats, especially in dry environments.

• Photosynthetic, but they are not plants
• Actually a symbiosis between two microbes: a heterotrophic fungus and an autotrophic algae

Question 14

lichen meaning

Answer 14

an entity consistening of a fungus and a photosynthetic partner, which can be algae

fungus grows on rock or other surface and algae grows on fungus.

fungal partner in a lichen is often referred to as the mycobiont