Exam 2 Bacterial Structures 10/5

Question 1

How can bacteria avoid antibiotic treatment

Answer 1

Find a way for bacteria to go into dormancy

Producing more enzyme so that the antibiotic cant keep up inhibiting the enzymes at a rate that slows or stops their work

Question 2

Beta-lactam antibiotic resistance

Answer 2

Efflux pumps
Mutations in pore proteins
Beta lactamases

Question 3

The cell envelope:
Gram-positive cells

Answer 3

-Thick outer layer of peptidoglycan
-Very narrow periplasmic space
-Teichoic acids in the peptidoglycan

Question 4

The cell envelope:
Gram-negative cells

Answer 4

-A varying width periplasmic space
-Very thin layer of peptidoglycan
-An outer membrane composed of Lipopolysaccharide (LPS)

Question 5

LPS

Answer 5

Lipid A
Core polysaccharide
O-antigen

Question 6

Importance of LPS

Answer 6

contributes to negative charge on cell surface

helps stabilize outer membrane structure

may contribute to attachment to surfaces and biofilm formation

creates a permeability barrier

protection from host defenses

can act as an endotoxin

Question 8

Porin Proteins in E. coli

Answer 8

more permeable than plasma membrane due to presence of porin proteins and transporter proteins

Question 9

The cell wall:
Gram-positive

Answer 9

peptidoglycan layer has large pores throughout its matrix.

Question 10

The cell wall:
Gram-negative

Answer 10

cell has
porin and TonB proteins in its
outer membrane to transfer
molecules into the periplasmic
space.

Question 11

The cell envelope:

Answer 11

Some move from the periplasm to outside directly (these are known as autotransporters and are rare).

Some use single-step (never entering the periplasm) transport systems.

Question 12

The bacterial cell surface:

Answer 12

Motility from flagella: spiral, hollow, rigid filaments extending from the cell surface

Locations and number vary from species to species.

Question 13

Patterns of Flagella Distribution

*know for exam

Answer 13

monotrichous – one flagellum

polar flagellum – flagellum at end of cell

amphitrichous – one flagellum at each end of cell

lophotrichous – cluster of flagella at one or both ends

peritrichous – spread over entire surface of cell

Question 14

Three Parts of Bacterial Flagella

Answer 14

Motility from flagella

Composed of three basic pieces:

-Filament

-Hook protein

-Basal body

Question 15

Bacterial Flagellar Movement

Answer 15

flagellum rotates like a propeller
very rapid rotation up to
1100 revolutions/sec

counterclockwise (CCW) rotation causes forward motion (run)

clockwise rotation (CW) disrupts run causing cell to stop and tumble

Question 16

Chemotaxis

Answer 16

movement toward a chemical attractant or away from a chemical repellent

changing concentrations of chemical attractants and chemical repellents bind chemoreceptors of chemosensing system

Question 17

Motility by flagella

Answer 17

By using chemoreceptor proteins to sense changes in concentrations of attractants or repellents, cells can produce more runs to move in a particular direction.

Question 18

Mechanism of Flagellar Movement

Answer 18

flagellum is 2 part motor producing torque

rotor
- C (FliG protein) ring and MS ring turn and interact with stator

stator (electromagnet)- Mot A and Mot B proteins

Archaea-have a push me-pull me alternation with no tumbles

Question 19

The bacterial cell surface:

Answer 19

Motility from flagella
- Not all cells have EXTERNAL flagella!

• Some spirochetes have flagella in the periplasm.

Question 20

The bacterial cell surface:

Answer 20

Nonflagellar motility

• Gliding motility: smooth sliding over a surface
  (myxobacteria, cyanobacteria)
• Twitching motility: slow, jerky process using (pili) (N.meningitidis, P. aeruginosa)

Question 21

The bacterial cell surface:

Answer 21

Polymerization of actin-for propulsion of bacteria into adjacent cells (Shigella dysenteriae, Listeria monocytogenes)

Question 22

Adherence molecules to stick to surfaces
Cell surface

Answer 22

• Mediated by pili, fibers of pilin protein possess other proteins on their tips for sticking.
• A sex pilus is a different structure used for conjugation.
• Some scientists prefer to use “pili” only for conjugation structures and “fimbriae” (s. fimbria) for adherence.
• Some microbes (Caulobacter, Hyphomonas) use an extension of the cell envelope tipped by a “holdfast” of polysaccharides.

Question 23

Components Outside of the Cell Wall

Answer 23

outermost layer in the cell envelope
glycocalyx
- capsules and slime layers
- aid in attachment to solid surfaces
- e.g., biofilms in plants and animals

S-layers

Question 24

Capsules

Answer 24

composed of polysaccharides

well organized and not easily removed from cell

visible in light
microscope

protective
advantages