Growth, Nutrition, and Metabolism

Growth curve

lag, exponential (log), stationary, death

Lag Phase

-cell is synthesizing new components

-replenish spent materials

-adapt to new medium or other conditions

-varies in length (can be very short/absent)

Exponential (log) phase

-growth is constant

-population is most uniform

Stationary phase

-total number of viable cells remains constant

-metabolically active cells stop reproducing

-cell division rate= death rate

increased virulence or pathogenicity of bacteria

-preparing for long-term survival

-production of starvation response: chaperones, DNA protein, etc.

-morphological changes: decreased size, nucleotide condensation

Why do the bacteria enter the stationary phase

nutrient limitation, limited oxygen availability, toxic waste accumulation, critical population density is reached

Death phase

-decline in viable (living) cells

-possibilities: cell death (due to lack of nutrients), apoptosis of some, viable but non-culturable

-bottom line: some of the bacteria are dying, but the population is trying to survive

pH and temperature requirements

-ph=7.2

-tend to grow well in conditions found in the human blood

-bacteria still maintain an internal neutral pH

Siderophores

-release from bacteria to capture iron from the circulation

-our bodies use transferrin to capture free iron

-there is competition between siderophores and transferrin to capture the available iron

-bacteria with effective siderophores are more pathogenic

Oxygen requirements

• oxygen is easily reduced to toxic byproducts (superoxide radical and hydrogen peroxide)

• protective enzymes (Superoxide dismutase and catalase)

Bacteria have 3 common pathways

1.Glycolysis (anaerobic and aerobic)

2. Pentose phosphate pathway

3. Entner Doudoroff pathway (pseudomonas)

Aerobic respiration

-glycolysis+ oxidative phosphorylation

-32 ATP can be generated from aerobic respiration

-pyruvate into the TCA (or Kreb’s) cycle

-O2 is terminal electron acceptor

Anaerobic respiration

-Glycolysis +fermentation

-Pyruvate feeds into many different fermentation pathways

-End products are short chain alcohols or fatty acids

-Type of pathway and end product depends on the type of bacteria

-No matter which fermentation pathway is used, less ATP is made than with oxidative phosphorylation

Obligate Aerobes-aerobic and anaerobic effect

-Glycolysis + oxidative phosphorylation

-Produce more ATP

-Grow quickly (24-48h in lab)

Obligate Anaerobes-aerobic and anaerobic

-Glycolysis+ fermentation

-Produce less ATP

-Grow slowly (longer than a week in some cases)

Facultative Anaerobes

-If O2 is present, they will use aerobic respiration so that they can generate more ATP, the faster they grow the more competitive

Rate of DNA polymerases Eukaryotes

50-100 base pairs/second

Rate of DNA polymerases Prokaryotes

750-1000 bp/sec