Week 3: Microbes

Question 1

4 important reasons for studying microbes

Answer 1

1. Microbes cause diseases of macroscopic organisms
2. Microbes provide examples of early life on earth
3. Microbes are model systems for general principles in ecology
4. Microbes mediate many biogeochemical processes that affect climate

Question 2

Most diverse organisms on the planet

Answer 2

Microbes, more than 100 times more diverse than plants and animals

Question 3

Microbes are found where macroscopic organisms are not in environments with extremes in

Answer 3

Temperatures, PH or pressure

Question 4

Microbes breathe

Answer 4

Nitrate and sulfate

Question 5

Microbes consume

Answer 5

Hydrogen sulfide, which is toxic to macro organisms

Question 6

Microbes responsible with which processes

Answer 6

1. Recycling organic carbon
2. Degrade/detoxify pollutants
3. Methane production and ammonium synthesis

Question 7

Microbes account for what percent of the biomass in the ocean

Answer 7

90%

Question 8

The weight of all bacteria in the world is roughly

Answer 8

A gigaton

Question 9

The classic food web

Answer 9

Phytoplankton -> zooplankton -> small fish -> larger fish

Question 10

Particulate organic material (POM)

Answer 10

Bodies or fragments of dead organisms as well as fecal material

Question 11

Dissolved organic matter (DOM)

Answer 11

Low molecular weight compounds dissolved in seawater

Question 12

Decomposition

Answer 12

Degradation of organic matter (detritus)

Question 13

Detritus supports

Answer 13

An alternative food web, the microbial loop

Question 14

Marine carbon cycle (microbe focused)

Answer 14

1. Phytoplankton fix carbon during photosynthesis
2. Phytoplankton convert inorganic carbon and nutrients into organic matter via photosynthesis (DOM) (POM)
3. Phytoplankton biomass is consumed by zooplankton grazers (“classic” foodweb)
4. The microbial loop: Heterotrophic bacteria consume DOM+POM released by phytoplankton and (a) convert it into biomass (b) respire (release CO2) (c) remineralise inorganic materials
5. Protists and zooplankton then graze on bacteria
6. Heterotrophic bacteria transform DOM from a labile (usable) form (LDOM) to a recalcitrant (unusable) from (RDOM) - leads to long term storage
7. Sinking of particulate organic matter to the ocean floor - marine snow

Question 15

Most of the degredation of organic matter is due to

Answer 15

Aerobic respiration of DOM

Question 16

Remineralization

Answer 16

Release of inorganic or mineral nutrients and carbon, following decomposition

Question 17

Labile DOM (LDOM)

Answer 17

Present mainly in sunlit surface waters. Available for immediate biological utilization

Question 18

Semi-labile DOM (SLDOM)

Answer 18

A small fraction of DOM that can be utilized by microbes over a longer time scale (months-years)

Question 19

Recalcitrant DOM (RDOM)

Answer 19

1. The main fraction of DOM in the ocean (accounts for 95% of DOM in the global ocean).
2. Resistent to microbial utilization and can persist in the ocean for thousands of years

Question 20

Heterotrophic bacteria convert LDOM to RDOM

Answer 20

Long term storage

Question 21

Limits to bacteria growth and therefore microbial production

Answer 21

1. Biotic control: Predation, viral lysis, competition
2. Abiotic control: Temperature, organic carbon, inorganic nutrients

Question 22

Organic carbon cencentrationa are very ___ in nature

Answer 22

Low

Question 23

There is a correlation between

Answer 23

Bacterial production and primary production

Question 24

The quality of organic carbon influences

Answer 24

Microbial productivity

Question 25

Most abundant biological entities

Answer 25

Viruses (10^31 on planet)

Question 26

Bacterial predation

Answer 26

Grazing by protists

Question 27

Bacterial grazers process

Answer 27

Consume its prey and oxidise organic carbon to CO2

Question 28

Viral lysis process

Answer 28

Releases the entire cellular contents, producing DOM

Question 29

Viral shunt

Answer 29

Production of DOM by viral lysis and its subsequent reutilization by other microbes

Question 30

Degradation rates follow

Answer 30

Primary production

Question 31

What percent of global microbial production happens in the ocean

Answer 31

50%

Question 32

Microbes account for ____ of the total respiration

Answer 32

over half