Lecture 2

Question 1

What is the proportion between human cells and bacteria (and the genes) ?

Answer 1

1.3x more bacteria.
1% only of human genes

Question 2

microbiota in desease treatment

Answer 2

probiotics, fecal transplant, phage therapy, …

Question 3

Why do we owe microbes ?

Answer 3

Because our organelles are derived from bacteria : mitochondria and chloroplasts -> engulfing of prokaryotes

Question 4

Main differences between virus, bacteria, archea, fungi, animal, plants

Answer 4

LOOK AT TABLE IN SLIDES !!!

Question 5

Structure of viruses

Answer 5

• single or double stranded RNA or DNA
• surrounded by protein shell called capsid
• sometimes : outer envelope (lipids + prot) -> more dangerous because often similar to animal cells
• inactive outside a living cell

Question 6

What are bacteriophages ? Why are they useful ?

Answer 6

Naturally existing viruses that kill bacteria. They are useful to prevent using antibiotics (ex: coat implants). A lot of current molecular methods are based on phage studies !

Question 7

What are the 2 main bacteria shapes ?

Answer 7

coccus and rod

Question 8

Difference between gram+ and gram-

Answer 8

Gram+ : thick cell wall (peptidoglycan)
gram- : thin cell wall but second membrane -> much less sensitive to antimicrobials

Question 9

What are bacterial capsules and their functions ?

Answer 9

• Made of excreted polysaccharides.
• Protect against dessication, phagocytosis, anti-microbials
• adherance to surface

Question 10

What are fimbriae and pili ? and flagella ?

Answer 10

pili / fimbrae : filamentous structures composed of protein. They allow to stick to surfaces.
flagella : free at one end, ensure motility.

Question 11

What are spores ?

Answer 11

a survival structure, endure heat, chemicals, radiation, nutrient depletion, …
Killing them is hard !!

Question 12

Bacteria use many different metabolisms. Name 5. One problem?

Answer 12

respiration, fermentation, denitrification, sulfate reduction, methanogenesis.
Biofilms can cause corrosion cells -> infection very hard to treat

Question 13

2 structures of fungi

Answer 13

• yeasts : single cells
• hypheas : cells not completely separated, can transport food from the front to further away

Question 14

Particularity with fungal cell wall

Answer 14

Big variety. Super resistant to a lot of anti-microbials because so many layers.

Question 15

What helps for the diagnosis of fungal infections ?

Answer 15

Presence of glucans in almost all fungi’s cell wall.

Question 16

What is a problem with a fungi for humans?

Answer 16

We have a lot in common with fungi on a cellular level -> substances could also harm us. And resistance to antifungal treatment can also occur.

Question 17

What do antifungals mostly treat ?

Answer 17

Ergosterols and their production

Question 18

What do culture media need to contain and provide ?

Answer 18

carbon source, energy source, nitrogen source, (terminal electron acceptor).
Provide a stable appropriate pH, correct salinity, trace elements.

Question 19

3 types of media and their use.

Answer 19

Solid : separate types of microbes, check quality of a culture (contamination).
Liquid : produce large amounts of microbes, easy to monitor.
Semi-solid: used to check motility

Question 20

What is the difference between defined and complex medium ?

Answer 20

Defined = composition exactly known, pure chemical substances, free of animal-derived components.
Complex = approximate composition, containing yeast extract, … Composition varies between batches.