Lecture 1: Properties of Bacteria

Question 1

Bacterial actin and tubulin homologue

Answer 1

• MreB (actin)

- FtsZ (tubulin)

Question 2

Because bacteria do not have a nucleus, what is uniquely coupled in these cells?

Answer 2

-transcription and translation

Question 3

Rule of thumb: essential genes are found on the _______ and unessential genes are found on _____.

Answer 3

• Chromosome

- Plasmids

Question 4

Theme about bacterial genome size

Answer 4

• Size of genome reflects lifestyle of bacterium
• Small: obligate intracellular pathogens
• Large: thrive in variety of environments

Question 5

Differences between bacterial and eukaryotic membranes

Answer 5

• does not contain sterols
• site of energy production since they do not have mitochondria
• outside of membrane, have rigid cell wall

Question 6

Peptidoglycan is what bacterial cell walls are made of and is composed of repeating pairs of what sugars?

Answer 6

• NAG and NAM joined by B(1,4)- linkages

- crosslinked by peptides

Question 7

Peptidoglycan is sensitive to what enzyme and why?

Answer 7

-Lysozyme sensitive because this enzyme can cleave B(1,4) bonds

Question 8

Like bacterial cell shape, _______ can be very useful in identifying bacteria

Answer 8

-gram stain

Question 9

-Gram positive vs. gram negative

Answer 9

-G+: stains blue/purple, thick peptidoglycan layer outside of internal membrane

G-: stains pain, thin peptidoglycan layer sandwiched between inner and outer membrane

Question 10

In a gram negative cell, what is the space between the 2 membranes called?

Answer 10

-Periplasm

Question 11

Gram-positive surfacce

Answer 11

• Teichoic acid and Lipoteichoic acid (LTA)
• peptidoglycan and LTA are exposed and recognized by host immune system
• better at living in dry areas like skin

Question 12

Gram-negative surface

Answer 12

• very asymmetric
• outer leaflet of outer membrane contains LPS (lipopolysaccharide), an endotoxin, which is trigger for immune system
• outer membrane also has porins which makes it more permeable than inner membrane

Question 13

5 things bacteria use their surfaces for:

Answer 13

1. motility via flagella
2. Adherence via pili/fimbriae
3. sensing the environment via Two component signal transuction system
4. Acquiring nutrients
5. Avoiding immune defenses: capsule,

Question 14

Two-component systems

Answer 14

• used to sense and respond to bacteria’s surroundings
• consist of histidine kinase protein (HK) that spans bacterial membrane and a response regulator protein (RR) located in bacterial cytoplasm
• HK autophosphorylates when it binds its stimulus on outside of membrane. P-HK then phosphorylates RR which is usually a TF, to activate it
• result: change in environment results in a change in gene expression on inside of cell

Question 15

T/F: only gram + cells can form capsules.

Answer 15

-false, + and - can

Question 16

Type 3 Secretion System (TTSS)

Answer 16

• used only by G- cells
• crosses 3 membranes
• directly introduces bacterial effector proteins into host cell without risk of antibody interference
• effectors manipulate host cell’s behavior to usually affect actin in cytoskeleton to promote or inhibit uptake of bacterial cell

Question 17

Examples of bacteria living together to form multicellular structures

Answer 17

• fruiting bodies (anthrax)

- biofilm

Question 18

When do biofilms form?

Answer 18

-When planktonic cells attach to solid surface and start to secrete slime called extracellular polymeric substance (EPS)

Question 19

2 mechanisms for biofilm growth and which is more prominent?

Answer 19

• Cell division

- recruitment **

Question 20

Why are biofilms clinically important/worrisome?

Answer 20

-they are resistant to antibiotics and also to host antimicrobial peptides which makes them hard to treat

Question 21

Why is lateral gene transfer the major way bacterial evolve into pathogens, instead of mutations?

Answer 21

mutations are often detrimental, lateral transfer genes have already stood the test of selection, and it allows whole sets of genes to be transferred together

Question 22

T/F: most antibiotics are man-made

Answer 22

-false; most made by other microbes, often other bacteria

Question 23

T/F: virulence genes and antibiotic resistance genes are often carried on mobile DNA elements

Answer 23

True

Question 24

How are plasmids laterally transferred?

Answer 24

-conjugation

Question 25

Many bacterial toxins are encoded by ________.

Answer 25

-temperate bacteriophages

Question 26

Virulence genes found on bacterial chromosome are often clustered in what are called __________.

Answer 26

-Pathogenicity islands (likely from a phage)

Question 27

Natural competence is also known as?

Answer 27

• Transformation
• mainly G+ but also done by some G- cells
• incorporate free DNA usually from lysed siblings that is in their environment