Heterotrophic Bacteria & Bacterial Growth Efficiency

Question 1

Heterotrophic Bacteria

Answer 1

Bacteria that needs food (organic carbon) from outside sources.

Question 2

Why do Bacteria need Organic Carbon?

Answer 2

To Build Biomass, Respire CO2 for energy, and Maintain Cellular Function

Question 3

Microbial Loop

Answer 3

Carbon cycle by heterotrophic bacteria that uses and produces DOC.

Like an “invisible clean up crew” that consumes remnants of excretions and sources of food that are invisible to the naked eye.
This reintroduces energy back into food web (when being eaten) and returns DOC to higher trophic levels.
The DOC can also be respired into CO2.

Question 4

Bacterial Growth Efficiency

Answer 4

Proportion of assimilated carbon that is converted into biomass by bacteria

Question 5

How to Calculate Bacterial Growth Efficiency?

Answer 5

BGE = BP/(BP + BR) = BP/BCD

BP = Bacterial Production (amount of biomass made)
BR = Bacterial Respiration (amount of food respired/remineralized to CO2)
BCD = Bacterial Carbon Demand (amount of food consumed)

Question 6

What factors influence BGE?

Answer 6

Primary Production, Temperature, DOM Composition, Growth Rate

Question 7

How is BGE Measured?

Answer 7

BCD is measured by the amount of food (radiocarbon food sources) disappeared in a controlled lab experiment.

BP is measured by concentrations of thymidine and/or leucine in cells.

BR is measured by oxygen respired

Question 8

SAR11 & it’s Importance

Answer 8

SAR11 is a heterotrophic bacteria that uses many DOC sources and is responsible for 6- 37% of total rate of organic carbon production (NPP) in the whole ocean

Question 9

Quorum Sensing & it’s Importance

Answer 9

Cell Communication—bacteria coordinate gene expression and activity and produce organic compounds that trigger specific activities when at a specific threshold population.

Quorum sensing may help POC convert to DOC.