Week 3: Microbes Flashcards
Why do we need to understand what microbes do
- Important primary producers
- Disease
- Examples of early life
- Mediate global climate
- Model organisms for ecological research
- Microbial production (the microbial loop)
Microbes are everywhere
- The most numerous and diverse organisms on the planet
- More than 100 times more diverse than plants and animals
- Found in environmental extremes to temperature, Ph and pressure
Microbes doing nearly everything
- Many different microbes have strange metabolisms
- Live without oxygen and breathe nitrate or sulfate
- Consume H2S (deadly for macroscopic organisms)
- Methane production and ammonium synthesis from N2 only done by microbes
- Degrade and detoxify pollutants
- Almost exclusively responsible for recycling organic carbon
Microbes at massive scales
- Microbes account for >90% of the biomass in the ocean
- About 99% of the biologically active surface area
- The weight of bacteria in the world roughly a gigaton
Microbes cause diseases of
Macroscopic organisms, which control populations
Studying microbes provide information to understand
- Life in the distant past
- Insights into life on other planets
Microbes are model systems for
General principles in ecology, as they grow rapidly and can be manipulated in labs easily.
Microbial ecology is essential in understanding impact on greenhouse gases because
All of these gases are either used or produced by microbes
The classic marine food web
- Phytoplankton eaten by zooplankton
- Zooplankton consumed by small fish
- Small fish consumed by larger fish
POM
Particulate Organic Material:
Bodies or fragments of dead organisms as well as fecal material
DOM
Dissolved Organic Matter:
Low molecular weight compounds dissolved in seawater
Decomposition/detritus
The degradation of organic matter
Exudation by
Primary producers
Excretion by
Autotrophs
POM to DOM conversion via
Excretion of extracellular enzymes by bacteria
DOM is not readily available to
The non microbial parts of food webs
Detritus supports the alternative food web
The microbial loop
The marine carbon cycle (microbe focused)
- Phytoplankton fix C during photosynthesis
- Phytoplankton convert inorganic C and nutrients into organic matter via photosynthesis (DOM,POM)
- Phytoplankton biomass is consumed by zooplankton grazers (classic food web)
- The microbial loop, Heterotrophic bacteria consume DOM+POM released by phytoplankton and, convert it into biomass, respire (release CO2) and remineralise inorganic nutrients
- Protists and zooplankton then graze on bacteria
- Heterotrophic bacteria transform DOM from a labile (usable0 form (LDOM) to a recalcitrant (unusable) form (RDOM) - leads to long term C storage
- Sinking of particulate organic matter to the ocean floor - marine snow
Most of the degradation of organic matter is due to
Aerobic respiration of DOM:
Remineralization
Release of inorganic or mineral nutrients and carbon, following decomposition
The microbial carbon pump involves
Heterotrophic bacteria successively transforming DOM from Labile DOM to recalcitrant DOM through the microbial loop
LDOM
Labile DOM: Present mainly in sunlit surface waters, Available for immediate biological utilization
SLDOM
Semi-Labile DOM: A small fraction of DOM that microbes can utilize over a longer timescale (months-years)
RDOM
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.
