Lecture 8: Bacterial growth and metabolism Flashcards
how does bacteria replicate?
binary fission: a fundamental form of asexual reproduction where a single cell divides into two genetically identical daughter cells
how do bacteria populations grow?
Bacterial population grows exponentially
what does the large numbers of bacterial populations mean for natural selection?
- More cell division means more DNA
replication - More DNA replication means more chance for DNA to mutate
- Members of population may have mutations advantageous to environment
Explain antibiotic resistance
- Some members of population mutated into antibiotic resistance strains by chance (red cells)
- Antibiotic resistant strains survive
antibiotics (natural selection) - Survivors grow back into a population of antibiotic resistant bacteria
requirements of life/growth?
- Needs energy
- Needs carbon source
- (among many other elements like nitrogen)
Photoautotrophs make __ from __
organic molecules (such as glucose)
sunlight, water and CO2
Chemoheterotrophs use
organic molecules to extract energy and as a carbon source
Glycolysis
the process from which energy is extracted from glucose
Glucose has how many carbons?
6 carbon sugar
Glycolysis generates
- 2 pyruvate (3-carbon sugar)
- 4 ATP
- 4 electrons (e-) + 4 protons (H+)
What is the net gain per glucose
Net 2 ATP gain per glucose
Of 4 ATP produced after splitting 1 glucose:
- 2 gets used to split another glucose
- 2 gets used for other jobs in the cell
NAD +
an organic molecule which can
bind to electrons
chemical reaction for NADH
(NAD^+) + (H^+) + 2 e- = NADH
Every time glucose gets split…
NAD + is used to accept electrons
what is the problem regarding NAD+
Limited number in cell
Can not do __ once NAD + gets
depleted
glycolysis
What is fermentation used to do?
- Use pyruvate to regenerate NAD+
- Pyruvate is the other product produced by
glycolysis
chemical reaction showing regeneration of NAD+
Pyruvate + NADH = (NAD^+) + fermented products
Pyruvate gets turned into fermentation
products in the process such as
acids, alcohols etc
Fermentation happens
anaerobically
is Fermentation efficient?
Fermentation is not efficient
* Pyruvate is a 3-carbon molecule
which has more energy stored
* Fermentation does not use this extra
energy since it uses pyruvate to
regenerate NAD+
Krebs cycle extracts energy which is left
inside pyruvate. What does one pyruvate become?
One pyruvate eventually becomes 3 CO 2
Krebs cycle makes more ___
NADH (and other electron carriers) + ATP
NADH gives electrons to
ETC, this regenerates NAD+
Energy is produced as
electrons pass through ETC, used to make ATP
* At the end of ETC, electrons are put onto O2,
the terminal electron acceptor
Aerobic respiration extracts the maximum
amount of energy from glucose,
producing up to
38 ATP per glucose
What part does O2 play?
- O2 is a very powerful electron acceptor
- Using O 2 as the terminal electron
acceptor allows electrons to pass through
ETC at maximum efficiency, extracting
maximum energy - Aerobic organisms (like human) are
dependent on O2 to produce energy
Anaerobic Respiration
- Respiration can be done using
molecules other than O 2 as terminal
electron acceptors - NO 3- (nitrate)
- SO 42- (sulphate)
- Non-O 2 electron acceptors are not as
effective as O 2 to drive electrons through ETC
Order the following processes based on how much total energy is produced: aerobic respiration, anaerobic respiration, fermentation
Fermentation < Anaerobic < Aerobic
Obligate aerobes
Oxygen required for survival
Facultative anaerobes
- Can use oxygen when available
- Can survive by anaerobic respiration
and/or fermentation if necessary
Obligate anaerobes
- Can not survive when oxygen is present
- Oxygen is extremely reactive and is
poisonous for organisms who does not
have protective measures
Mycobacterium tuberculosis
- Obligate aerobe
- Respiratory pathogen
E. coli
- Facultative aerobe
- Gut microbe/pathogen
____ is consumed using ___ during aerobic
exercise
Glucose
O2
We ferment pyruvate into ___ to
produce more energy anaerobically
lactic acid
* Accumulation of Lactic acid Lactic is said to be
correlated with muscle fatigue, although this
theory is sill being debated
yogurt fermentation process
- Must be done anaerobically
- Lactobacillus bulgaricus and Streptococcus
thermophilus are put into milk - Both Gram positive lactose-fermenting bacteria
- Lactose fermented to lactic acid
- Acidifies the product, thickening the solution
- In addition, L. bulgaricus and S. thermophilus
performs other other metabolic activities - All of this contributes to the taste and texture
of yogurt
how is the growth of organisms like E coli stopped during yogurt fermentation?
Acidification of yogurt (+ high incubation temperature) suppresses growth of other bacteria such as E. coli
ethanol/alcohol fermentation
- Yeast (Saccharomyces cerevisiae), a unicellular eukaryote (Fungi)
- Used for many food processes, including
production of alcohol from various sources of starch - Type of starch contributes to the type of alcoholic beverage produced
- Alcohol production begins to inhibit yeast growth after a while
Cyanobacteria: producing glucose
- Gram negative photoautotrophic bacteria
- Only clade of bacteria capable of photoautotrophy
- Use sunlight to produce organic molecules like glucose from CO 2
- Carbon fixation: Chemical energy generated by sunlight gets stored in glucose
CO2 + H 2O + sunlight = glucose + O2
Some cyanobacteria are also capable of
nitrogen fixation: convert atmospheric N 2
to ammonia (NH3)
* Nitrogen is essential for making DNA, proteins, etc.
* Most organisms can not use N2 as their
nitrogen source and depend on ammonia produced by nitrogen fixers
how does cyanobacteria do nitrogen fixation while producing O2 as a product
- Some cells in cyanobacteria filament terminally
differentiate to heterocysts: cells specialized for nitrogen fixation - Heterocysts can not survive on its own
- Can not photosynthesize and depends on
neighboring vegetative cells to provide glucose etc. - Heterocysts form barrier to block O2 entry,
allowing nitrogen fixation inside their cell - Heterocysts provide fixed nitrogen to
neighboring cells
