L8: Bacterial Growth and Metabolism

How does bacteria replicate?

• binary fission

• bacteria population grows exponentially (doubles every cycle)

• Example: Escherichia coli divides every 20 mins

How does antibiotic resistance spread?

• random mutations occur

• the resistant mutated bacteria survive

• they replicate producing only resistant bacteria

What are the 3 requirements of life?

1. energy

2. carbon source

3. nitrogen

What does glycolysis produce?

• 2 pyruvate molecules

• net 2 ATP

• 4 electrons and 2 hydrogen ions that get used to convert 2 NAD+ to 2 NADH

• 2 hydrogen ions in cytoplasm

Fermentation

• anerobic respiration

• 2 NADH lose the 4 electrons, they oxidize to 2 NAD+ (used in glycolysis)

• 2 pyruvates + the 4 electrons produce fermented products (alcohol, acids, etc.)

• NOT EFFICIENT. Pyruvate can produce more ATP if aerobic. Only 2 ATP produced.

What happens once pyruvate is produced and oxygen is avilable?

• Pyruvate goes to TCA/krebs cycle

• 6 CO2 molecules are produced (3 per pyruvate)

• 2 ATP produced

• electron produced which converts NAD+ to NADH

• 4 electrons produced from the NADH converting to NAD+

• the 4 electrons from glycolysis and the 4 electrons from the krebs cycle (all from NADH being oxidized to NAD+) go to ETC

• the terminal electron acceptor, oxygen and produces H2O byproduct.

• 34 ATP produced max

Anerobic respiration (not fermentation)

• Instead of O2 as terminal electron acceptor, ETC uses nitrate (NO3 -) or sulfate (SO4 2-)

• Produce more than fermentation but less than aerobic respiration (less than 34 in ETC)

What are the 3 types of respiration in microorganisms?

1. obligate aerobic (human)

2. facultative anerobic (Escherichia coli)

3. Obligate anaerobe (oxygen poisonous)

Can humans do anerobic respiration?

• Yes humans undergo fermentation producing lactic acid.

• There are theories this is related to muscle fatigue

Streptococcus thermophilus

• put into milk

• gram positive

• lactose fermented to lactic acid when oxygen not present (makes yogurt)

• Lactose - Glucose - Pyruvate - Lactic acid

• High incubulation and acidification of the yogurt prevents growth of bacteria such as Escherichia coli

Alcohol fermentation

• yeast (unicellular fungi eukaryote) used to produce alcohol from starch.

• distillation is needed to produce higher percentages of alcohol

• Fermentable starches (ague/sugarcane/malted barley/grape/rice) - glucose - pyruvate - ethanol fermentation - distillation for some

Cyanobacteria

• gram negative

• only clade of bacteria that is photoautorophic

• Some capable of nitrogen fixation

Problem with nitrogen fixation

• can’t happen with oxygen nearby

• easily inhibited by oxygen

• heterocyst (perform nitrogen fixation). Can’t survive with too much oxygen. They form barrier to block O2 from entering the cell, so they can produce NH3 from N2.