Microbial Metabolism and Growth Flashcards
No matter how microbes obtain their energy source, what do they generally want to use for this?
Glucose
How do chemoheterotrophs get their glucose?
By importing it directly using transporters
How do chemoautotrophs get their glucose?
By fixing carbon to create glucose themselves using the Calvin Cycle
Why do microbes use glucose specifically?
-Glucose is a great electron donor
-Oxygen is a great electron acceptor
What are the phases of bacterial growth?
- Lag phase
- Log phase
- Stationary phase
- Death phase
Lag phase of bacterial growth
no increase in # of living bacterial cells
Log phase of bacterial growth
exponential increase in # of living bacterial cells
Stationary phase of bacterial growth
plateau in # of living bacterial cells; rate of cell division and death ~ equal
Death phase of bacterial growth
exponential decrease in # of living bacterial cells
Which is easier to metabolize? Glucose or lactose
glucose
Why is glucose easier to metabolize than lactose?
Lactose produces 2 glucose molecules BUT at the cost of 2 additional ATP and 6 enzymes
How do protons power ATP synthase?
Via proton motive force
Since prokaryotes and unicellular eukaryotes are metabolically diverse and flexible, what ability do they have regarding metabolic strategies?
They are able to quickly adjust metabolic strategies within a single cell type
In the absence of C6 or C4, some bacteria can use ____ with the ____________ cycle.
C2, glyoxylate
Isocitrate lyase
Bypasses number of TCA steps and creates an intermediate -> glyoxylate
Glyoxylate Cycle
Allows microbes to grow off of fatty acids as fatty acid degradation produces acetate
What are the variations on traditional aerobic central metabolism?
- Glyoxylate cycle
- Mixed Acid Fermentation
Mixed Acid Fermentation
-Anaerobic, low energy
-Pyruvate is converted to lactic acid (recover 1 NAD)
-Acetyl CoA is converted to ethanol and acetate (Recover 2 NAD, gain 1 ATP)
Lactic acid bacteria can “___________” and is why they are often considered “___________.”
niche construct, keystone species
Niche Construction
A process where organisms change their environment in ways that can affect the evolutionary dynamics of themselves and of other organisms
Keystone Species
A species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically
Is lactic acid fermentation a type of anaerobic respiration?
No because cellular respiration has a specific definition
Cellular Respiration
The act of oxidizing highly reduced compounds (FADH, NADH) to establish an electrochemical gradient (often a proton gradient) across a membrane. Protons moved down the gradient (across the membrane) through the proton channel of ATP synthase, creating ATP.
Aerobic respiration
Terminal electron receptor is oxygen
Anaerobic respiration
Terminal electron receptor is a non-oxygen inorganic molecule
Common alternative electron donors
- Ammonium
- Sulfur compounds
- Iron
Common alternative electron acceptors
- Nitrate
- Sulfate
- Manganese and iron = common metal electron acceptors
Rhizosphere
population of microorganisms that inhabit the area around a plant root
Most nitrifying bacteria are only able to do _______ step of oxidizing ammonia/ammonium > nitrite > nitrate
one
What microbes can do both steps of oxidizing ammonia/ammonium?
Comammox (Complete Ammonia Oxidation)
ex: Nitrospira
Pro and con of Nitrification
Pro: great for plants > fertilizer
Con: Source of pollution from run-off
Completion of the nitrogen cycle by ____________ is critical for ecosystem health.
denitrification (reducing NO3 to N2)
Denitrifying bacteria can be used for _________.
bioremediation
Bioremediation
use of microorganisms to break down environmental pollutants
What microbe can be used to biomine for gold?
Acidithiobacillus ferrooxidans
What is biomining?
extracting metals from ores or waste by using microorganisms
Geobacter spp. have special cytochromes on conductive pilli (__________) that transfer electrons to Fe3+ containing minerals.
nanowires
What is Rhodoferax ferrireducens and what can it be used for?
It is a facultative anaerobe that can use Fe(III) as a terminal electron receptor in the absence of oxygen to harness energy.
What are some applications for microbial batteries?
MEDICINE:
-ingestible endoscopy
-anti-cancer precision therapies
-anti-psychotics precision therapies
Summary of chemoheterotroph metabolism based on energy source
- organic electron donor
- Electron transport/generation of pmf (or Fermentation)
- S0, SO4, NO3 > anaerobic respiration/O2 > aerobic respiration
Summary of chemoautotroph metabolism based on energy source
- Inorganic electron donor (H2, H2S, Fe2+, NH4+, etc.)
- Electron transport/generation of pmf
- S0/SO4/NO3- > anaerobic/O2 > aerobic respiration
What is proton motor force (pmf)?
The key energy generation and microbial physiology; the electrochemical gradient of protons across bacteria cytoplasmic membrane
What is PMF essential for?
variety of critical bacterial processes (ATP synthesis, flagellar motility, and nutrient import)
In respirating organisms, what drives ATP synthesis?
PMF
In motile cells, what drives flagellar movement?
PMF
What environmental condition might be problematic for maintaining PMF?
Alkaline conditions (high pH)
In times of depleted PMF, what happens to help maintain the electrochemical gradient?
ATP synthase can reverse to export H+ at the expense of ATP
Why is PMF depletion less important for flagellum?
Motility is not essential during alkaline shock, cells can just stop swimming. However, import of resources and generating biomolecules to maintain cell structure needs PMF.
What do most bacterial flagellum run on?
hydrogen ions
What do alkaliphile flagellum run on?
sodium ions
Where are alkaliphile viruses/diseases most active during infection?
upper intestine: low pH
lower intestine: high pH
-LOWER
What do photosynthetic bacteria use to generate PMF?
light
Cyanobacteria
blue-green algae
Salinibacter ruber
red bacteria
Sulfur bacteria
purple
What are the two major types of photosynthetic metabolism?
anoxygenic and oxygenic
What metabolism and pigment does purple sulfur bacteria use?
anoxygenic and bacteriochlorophyll a
What metabolism and pigment does cyanobacteria use?
oxygenic and chlorophyll a
What earth event are cyanobacteria associated with?
great oxidation event (in the evolution of life on earth)
What does Chlorophyll a absorb and reflect?
absorbs: red/blue
reflects: green
top of ocean
What does Bacteriochlorophyll a absorb and reflect?
absorbs: ultraviolet rays
reflects: infrared
bottom of ocean
What are antenna complexes?
made up of arrangements of Chlorophylls or Bacteriochlorophylls to help funnel photons to the Reaction Center
What is the Reaction Center?
the site of primary energy conversion and the initial electron acceptor for the electron transport chain (reflect, concentrate, power PMF)
