7-2: Microbial Warfare

Question 1

How are antibiotics used in microbial warfare

Answer 1

Some bacteria (e.g. Streptomyces) produce/secrete small molecules (NOT PROTEINS) that inhibit or kill bacteria

Question 2

Why is antibiotic production by organisms like Streptomyces highly regulated?

Answer 2

Prevents competitor organisms from becoming antibiotic resistant.

Question 3

Where do streptomyces live? When are antibiotics produced?

Answer 3

Soil, in competitive microbial communities.
Produced during starvation to inhibit growth of competitors and allows them to complete the sporulation process.

Question 4

What is the type VI secretion system (T6SS)

Answer 4

Essentially a syringe/needle to inject toxic proteins into competing bacteria. Requires close contact.
Species/strain variation - not all bacteria encode them.
Sometimes used on eukaryotes

Question 5

What are immunity proteins?

Answer 5

Found immediately downstream of the Type VI secretion system. Encoded to prevent self-intoxication.

Question 6

What are T6SS effectors? What is targeted?

Answer 6

Toxic proteins of type VI secretion systems. T6SS effectors targets key cell structures (CW, membranes, DNA)

Question 7

What are T6SS related to?

Answer 7

Systems used by phages to inject their DNA into bacteria.

Question 8

What are bacteriocins?

Answer 8

Protein (NOT SMALL MOLECULES) toxins produced/secreted by certain bacteria. Similar to antibiotics because they are secreted toxic molecules, similar to T6SS because they are toxic proteins targeting neighbouring cells

Question 9

What makes bacteriocins similar to T6SS?

Answer 9

Immunity proteins (similar to T6SS)
Strain to strain variation exists
Similar targets (CW, CM, nucleic acids)

Question 10

Describe the strucutre of bacteriocins.

Answer 10

Chemically modified proteins (aa of protein is modified by an enzyme)

Question 11

How do bacteriocins cross OM and CM to access target

Answer 11

Have specific domains that allow them to cross the outer/cytoplasmic membrane.

Question 12

What is Nisin?

Answer 12

Used in food preservation. Targets cell wall synthesis and effective against Gram positive bacteria. Requires 11 genes (several that encode AA modifing enzymes)

Question 13

What are killer yeasts?

Answer 13

Yeast strains that produce toxins to kill other yeasts. Have two parts: one that has toxicity, other triggers uptake into target cells. Typically have their own immunity to toxin.

Question 14

What are killer toxins in yeasts encoded by?

Answer 14

Viruses that infect the yeast, or plasmids

Question 15

What commonly consumes and digests bacteria as primary food/energy source?

Answer 15

Free-living amoeba

Question 16

How do amoeba consume bacteria

Answer 16

Use temporary appendages called pseudopods to engulf bacteria

Question 17

What happens once bacteria are engulfed by amoeba

Answer 17

Phagocytosed into a vacuole, fuses with lysozyme where bacteria are killed/digested

Question 18

What are legionella pneumophila

Answer 18

Gram negative causal agent of Legionnaires’ disease.
Evolved to survive when consumed by amoeba, manipulate amoeba biology, avoid fusion with lysosome, create intracellular niche called Legionella containing vacuole. Allows survival in macrophages.

Question 19

How do people acquire legionnaire’s disease?

Answer 19

Typically breathing in aerosolized water than contain Legionella species

Question 20

What secretion system do l. pneumophila use? for what?

Answer 20

type IV to inject effector proteins into amoeba that manipulate host cell biology