Lecture 20: Bacterial Cell Division, Sporogenesis, and Extreme Microbes

What is MreB’s job?

major shape-determining factor

What type of bacteria have MreB

Rod-shaped bacteria (bacilli) and spiral bacteria (spirilla)

Where is MreB found in the cell?

inner membrane

What is Crescentin?

shape-determining protein (organizes into filaments giving cells curve)

Who has Crescentin?

vibrio-shaped bacteria

What is an endospore?

specialized, dormant (resting) cell formed inside a mother cell as a survival mechanism that allows bacteria to withstand extreme conditions

How long can endospores last?

1 day to 7500 years to 40 million years

What types of cells create endospores?

Gram-positive rod-shaped bacteria

What diseases do Gram-positive rod-shaped bacteria create?

• Genus clostridium (gangrene, tetanus, and botulism)

• Genus bacillus (anthrax)

What is the difference between vegetative and stasis?

in bacteria, vegetative means actively growing and stasis means not actively growing

Why do cells make spores?

To survive harsh conditions (extreme heat, drying out, lack of nutrients)

Endo vs Exospores – difference?

endo is inside mother and exo is outside mother

What acid is found in a spore?

dipicolonic acid and SASPs

What are SASP’s?

small acid-soluble spore proteins- protext spore DNA from UV damage, heat, and enzymes

Dipicolinic acid?

interacts with calcium to make it super dry in spore

What is the process of creating a spore called?

sporulation/sporogenesis

Difference between terminal, subterminal, and central endospores?

• Terminal: at end of cell

• Subterminal: Near end but not at tip

• Central: In middle of cell

What are the five different names for organisms based on their ideal temp?

• Psychrophiles

• Psychotrophs

• Mesophiles

• Thermophiles

• Hyperthermophiles

Psychrophiles temp range

Below 15

Psychotrophs temp range

Around 20

Mesophiles temp range

10 to 45 (optimal for humans)

Thermophiles temp range

Around 60

Hyperthermophiles temp range

Above 80

What really determines what temp the organism can survive in?

stability of macromolecules (proteins, DNA, lipids)

What happens to the organism if the temp gets too high?

• Proteins denature

• membranes lose integrity

• DNA strands break/become unstable

• cell death

How are hyperthermophiles able to survive such high heat?

high G/C ratio: DNA is stronger/harder to denature due to extra hydrogen bonds

What type of organism can survive the highest temps?

prokaryotes

How do psychrophiles survive the cold?

modified fatty acids: more unsaturated fatty acids—> water freezes around membrane instead of cracking the membrane

How can you grow psychrophiles?

Cold incubators

• in antartica you can just leave them outside

Food Safety – what is the danger zone?

15 to 45 degrees C

Why do we care about food safety zone?

Bacteria grows rapidly in this range

B. cereus

• Gram-positive, spore-forming bacterium that causes food poisoning and can grow in food safety danger zone

  • Better to store rice in smaller containers so it cools faster and is not in food safety danger zone

What are the five categories that organisms can be put in based on oxygen use?

• Obligate aerobes

• Facultative aerobes

• Obligate anaerobes

• Aerotolerant anerobnes

• Microaerophiles

Obligate aerobes

• Only aerobic growth; oxygen required

• Growth occurs only at high concentrations of oxygen (at top near surface of tube)

Facultative aerobes

• Both aerobic and anaerobic growth; greater growth in presence of oxygen

• Growth is best where most oxygen is present, but occurs throughout tube (mainly at top near surface and a little bit throughout tube)

Obligate anaerobes

• Only anaerobic growth; ceases in presence of oxygen

• Growth occurs only where there is no oxygen (bottom of tube)

Aerotolerant anerobnes

• Only anaerobic growth but continues in presence of oxygen

• Growth occurs evenly; oxygen has no effect (spread evenly throughout tube)

Microaerophiles

• Only aerobic growth; oxygen required in low concentration

• Growth occurs only where a low concentration of oxygen has diffused into medium (layer in middle of tube)

How do you grow microaerophiles?

Requires low oxygen levels, so candle jars/controlled CO2 incubators

How do you grow Obligate anaerobes?

Cannot tolerate oxygen so anaerobic chambers