Microbiology - Bacterial Structure

Question 0

What is the bacterial cell wall composed of?

Answer 0

Peptidoglycans

Question 1

What are the 2 characteristics of bacteria that control pathogens in the environment?

Answer 1

Ribosomes

Cell wall made of peptidoglycan

Question 2

What is peptidoglycans made up of and how is it formed?

Answer 2

• Is made up of NAM (N-acetlymuranic acid) and NAG (N-acetylglycosamine)
• These 2 short peptides are cross-linked together by the enzyme transpeptidase

Question 3

2 big differences between gram + and gram - bacteria

Answer 3

Gram +: 
- has a thick cell wall
- 1 membrane on the inside
Gram -:
- has a thin cell wall
- has 2 membranes (1 on inside, 1 on outside of cell wall)

Question 4

What are techoic and lipotechoic acids and where are they found?

Answer 4

They are sugary molecules found on the cell wall of gram + bacteria that stick out into the environment (the first thing that outside agents will interact with)
They help anchor the cell wall to the membrane

Question 5

One thing the outer membrane of gram - bacteria has that gram + doesn’t

Answer 5

Lipopolysaccharides (endotoxin)

Question 6

What are the functions of the 2 membranes and the cell wall in gram - bacteria?

Answer 6

Outer: manipulates an environment (cell wall) and creates gradients with its porins
Inner: transports
Cell wall: there are enzymes that break things down (such as proteins)

Question 7

What is an endotoxin, its significance and what is it made of?

Answer 7

It is a generalized structure that is a toxic component of gram - bacteria cell wall.
It is made up of 3 things:
O-antigen repeating subunits, polysaccharide and Lipid A
Significance:
-it is what is recognized by the immune system
-it is used diagnostically to tell between different types of bacteria

Question 8

Key function of the cell wall in bacteria

Answer 8

Prevents osmotic shock

It also gives shape to cells

Question 9

Gram staining: what type of bacterial cells turn what color and why?

Answer 9

Gram + cells turn blue.
Gram - cells turn red.
It is because of the thickness off the cell wall (gram + is thick, gram - is thin)

Question 10

What is the periplasm?

Answer 10

The space between the plasma membrane and the outer membrane.
It has hydrolytic enzymes in it

Question 11

See table 2-1 on slide 19 for bacterial cell structures and functions

Answer 11

.

Question 12

Main functions of the capsule

Answer 12

Adherence (increases ability to survive in environment)
Stores carbohydrates
Reduces chances cell will be engulfed by phagocytosis

Question 13

Glycocalyx structures

Answer 13

Some cells have; anchored to cell surface
More specific in its intent to allow attachment
(also may have fimbriae which are also specific for allowing certain things to attach to the acquired pellicle)

Question 14

What are pili?

Answer 14

A polymer of protein

Forms a long thread to attach with an adjacent cell and exchange genetic info –> thus increasing diversity

Question 16

Flagellum structure and function

Answer 16

Function: mobility
Structure: have a hook structure and a filament; the filament acts as a propeller

Question 17

How does chemotaxis work with bacteria?

Answer 17

The direction of rotation of flagella of the bacterial cells is determined by the detection of changes in concentration gradients of the detected compounds
(there are sensors on the surface of cells that tell them whether to move toward something or tumble away from it)

Question 18

How do bacterial cells reproduce?

Answer 18

By binary fission
4 Steps:
-DNA replicates
-chromosome segregates
-septum forms
-cytokinesis (parent cell divides into 2 progeny)
*although there are steps, this is a continuous process; it doesn’t happen in distinct stages like with eukaryotes
*results in logarithmic growth
*plane of segregation provides for different cell arrangements (linear, clusters, etc - so for streptococci, plane is always in same orientation; but for staphylococci, it changes

Question 19

What are the external and internal factors of growth limits in bacteria?

Answer 19

External Factors:
- adherence
- food
- temperature
- pH
- oxygen
Internal Factors: 
- metabolites, catabolites

Question 19

What are the phases of growth of bacterial cells?

Answer 19

Lag phase - where certain genes are turned on
Exponential growth phase - very short phase, also called log phase
Stationary phase - occurs after resources are depleted
Decline and cell death - if there is no re-introduction of resources into environment, this will occur

Question 20

Oxygen need for cellular metabolism of different types of bacteria

Answer 20

Aerobes - need oxygen (as final e- acceptor)
Facultative Aerobes - can use O2 if present, but can also use fermentation
Aerotolerant - don’t use O2, but are ok if its around
Strict Anaerobes - don’t use O2 and cannot be in presence of it (they ferment and use nitrate, sulphate for final e- acceptor)
Microaerophiles - like a little bit of O2 (5%)