Week 3: Microbes

Question 1

Why do we need to understand what microbes do

Answer 1

1. Important primary producers
2. Disease
3. Examples of early life
4. Mediate global climate
5. Model organisms for ecological research
6. Microbial production (the microbial loop)

Question 2

Microbes are everywhere

Answer 2

1. The most numerous and diverse organisms on the planet
2. More than 100 times more diverse than plants and animals
3. Found in environmental extremes to temperature, Ph and pressure

Question 3

Microbes doing nearly everything

Answer 3

1. Many different microbes have strange metabolisms
2. Live without oxygen and breathe nitrate or sulfate
3. Consume H2S (deadly for macroscopic organisms)
4. Methane production and ammonium synthesis from N2 only done by microbes
5. Degrade and detoxify pollutants
6. Almost exclusively responsible for recycling organic carbon

Question 4

Microbes at massive scales

Answer 4

1. Microbes account for >90% of the biomass in the ocean
2. About 99% of the biologically active surface area
3. The weight of bacteria in the world roughly a gigaton

Question 5

Microbes cause diseases of

Answer 5

Macroscopic organisms, which control populations

Question 6

Studying microbes provide information to understand

Answer 6

1. Life in the distant past
2. Insights into life on other planets

Question 7

Microbes are model systems for

Answer 7

General principles in ecology, as they grow rapidly and can be manipulated in labs easily.

Question 8

Microbial ecology is essential in understanding impact on greenhouse gases because

Answer 8

All of these gases are either used or produced by microbes

Question 9

The classic marine food web

Answer 9

1. Phytoplankton eaten by zooplankton
2. Zooplankton consumed by small fish
3. Small fish consumed by larger fish

Question 10

POM

Answer 10

Particulate Organic Material:
Bodies or fragments of dead organisms as well as fecal material

Question 11

DOM

Answer 11

Dissolved Organic Matter:
Low molecular weight compounds dissolved in seawater

Question 12

Decomposition/detritus

Answer 12

The degradation of organic matter

Question 13

Exudation by

Answer 13

Primary producers

Question 14

Excretion by

Answer 14

Autotrophs

Question 15

POM to DOM conversion via

Answer 15

Excretion of extracellular enzymes by bacteria

Question 16

DOM is not readily available to

Answer 16

The non microbial parts of food webs

Question 17

Detritus supports the alternative food web

Answer 17

The microbial loop

Question 18

The marine carbon cycle (microbe focused)

Answer 18

1. Phytoplankton fix C during photosynthesis
2. Phytoplankton convert inorganic C and nutrients into organic matter via photosynthesis (DOM,POM)
3. Phytoplankton biomass is consumed by zooplankton grazers (classic food web)
4. The microbial loop, Heterotrophic bacteria consume DOM+POM released by phytoplankton and, convert it into biomass, respire (release CO2) and remineralise inorganic nutrients
5. Protists and zooplankton then graze on bacteria
6. Heterotrophic bacteria transform DOM from a labile (usable0 form (LDOM) to a recalcitrant (unusable) form (RDOM) - leads to long term C storage
7. Sinking of particulate organic matter to the ocean floor - marine snow

Question 19

Most of the degradation of organic matter is due to

Answer 19

Aerobic respiration of DOM:

Question 20

Remineralization

Answer 20

Release of inorganic or mineral nutrients and carbon, following decomposition

Question 21

The microbial carbon pump involves

Answer 21

Heterotrophic bacteria successively transforming DOM from Labile DOM to recalcitrant DOM through the microbial loop

Question 22

LDOM

Answer 22

Labile DOM: Present mainly in sunlit surface waters, Available for immediate biological utilization

Question 23

SLDOM

Answer 23

Semi-Labile DOM: A small fraction of DOM that microbes can utilize over a longer timescale (months-years)

Question 24

RDOM

Answer 24

Recalcitrant DOM: The main fraction of DOM in the ocean (accounts for 95% of DOM in the global ocean). Resistant to microbial utilization, and can persist in the ocean for 1000s of years.

Question 25

Heterotrophic bacteria convert

Answer 25

LDOM to RDOM - long term C storage

Question 26

Limits to microbial production

Answer 26

Growth rates faster in controlled labs due to controls in
1. Temperature
2. Organic carbon (low in nature)
3. Predation/viral lysis

Question 27

Consumers of bacteria via predation

Answer 27

Protists

Question 28

Most abundant biological entities

Answer 28

Viruses

Question 29

Total viruses on the planet

Answer 29

10^31

Question 30

10-50% of bacterial mortality can be attributed to

Answer 30

Viruses, the rest to grazing protisrs

Question 31

More contact between viruses and hosts occurs when

Answer 31

There are higher nutrients which promote more cell production and higher biomass

Question 32

Viruses contribute more to bacterial mortality in habitats where

Answer 32

Protists do not grow well (arctic ice, low ph, high salt concentrations, high temperatures)

Question 33

Grazing and viral lysis result in

Answer 33

The death of both prey and host cells

Question 34

Grazers consumer its prey and

Answer 34

Oxidise organic carbon to CO2

Question 35

Viral lysis releases

Answer 35

The entire cellular contents, producing DOM (viral shunt)

Question 36

Degredation rates follow

Answer 36

Primary production

Question 37

What percentage of global microbial production happens in the ocean

Answer 37

About 50%

Question 38

What percentage do microbes account for of total respiration

Answer 38

Over 50%

Question 39

What percentage of the organic matter produced by primary production will end up as DOM, and channeled through the microbial loop

Answer 39

Around 50%