Bacteriology Lec 1 N 2

Front 1

What are autotrophs?

Back 1

Use non-living carbon and energy sources: the vast majority

Front 2

Saprophytes

Back 2

putrefactive. Live off nitrogenous waste: include some potential pathogens

Front 3

Name 3 type of symbiont relationships.

Back 3

interact with plants & animals
i) Commensal - normal flora
ii) Mutualistic - mutually beneficial
iii) Parasitic - disease producing (= the minority)

Front 4

Give 3 points about identifying the appearance of bacteria.

Back 4

1. Identification starts with a knowledge of colony appearance on plates and growth requirements

2. Then morphology + Gram stain on individual cells in a smear (see practical manual)

3. Bacteria are either Gram positive or Gram negative (are some exceptions)

Front 5

List the structures of an dealised bacterium (8)

Back 5

1. Cell Wall.
2. Capsule.
3. Flagella.
4. Mesosome
5. Sexpilus
6. Fimbriae/pili
7. Cytoplasmic membrane surrounding the protoplast.
8. Nucleus.

Front 6

What is the function of the cell wall? Give an example of a bacterium that does not posses the cell membrane.

Back 6

Cell walls give shape, and protect from osmotic pressure and the external environment.
Mycoplasma

Front 7

Which layer can the peptidoglycan be found in the gram positive and gram negative bacterium?

Back 7

Top on the +ve and middle in the -ve.

Front 8

What is peptidoglycan consists of?

What is the difference between gram +ve and -ve ?

Back 8

Consist of N-acetylglucosamine (G) and N-acetylmuramic acid (M), with L and D amino acids and lysine or diaminopimelic acid.

Gram positives have many such layers, whilst Gram negatives only have 1 or 2 such layers.

Front 9

Why does the gram positive bacteria stain blue?

Back 9

The thick layers of peptidoglycan holds the stain,

Front 10

What is the effect of lysosome on the cell wall.

Back 10

A natural antibacterial agent also works by breaking down the chains of G and M that make up the peptidoglycan.

Front 11

What extra layer does the gram negative bacteria have?

Back 11

Cells are surrounded by an outer membrane of lipopolysaccharide

Front 12

The space between the layers of peptidoglycan and the cell membrane is called the .............. .............. ?

Back 12

periplasmic space

Front 13

What are the 3 major regions of the LPS?

Back 13

O Polysaccharide
Core polysaccharide
Lipid A

Front 14

O Polysaccharide
Describe 3 points.

Back 14

>may be branched : mny different combinations
>antigenic : generates specific immune response
>highly species specific: gives serotype to bacteria.

Front 15

What is important about lipid A?

Back 15

Lipid A
toxic
internal, hence protected
(Fatty acids + N-acetylglucosamine

Front 16

Give 3 points of the capsule.

Back 16

1. Outer polysaccharide layer around some bacteria

2. - can convey resistance to phagocystosis (eg Bacillus anthracis)

3. Tight, or loose and slimy

Front 17

What is the Glycocalyx?
Why is it important?

Back 17

A slimy outer layer in some bacteria.
Involved in adhesion, clumping & biofilm formation

BIOFILMS e.g. Catheters, lungs

Front 18

Why are biofilms a major problem?

Back 18

They reduce penetration of antibiotics and disinfectants and provide the bacteria living in such communities with physical protection and other advantages.

Front 19

What are Pilus or Fimbria ?

Back 19

surface structures
rod-like protrusions
polypeptide subunits
>Extremely important in attachment of mucosal pathogens (therefore used in vaccines)

Front 20

What is the function of a sex pilus?

Back 20

- a single rod like structure protruding from the surface

- involved in transfer of DNA between bacterial cells (conjugative plasmids)

Front 21

Briefly give two points about the flagella,

Back 21

>Organs of motility, possessed by many bacteria.

>Require energy: driven by a rotary engine at the anchoring point in the inner cell membrane - pumps protons

Front 22

Define monotrichous

Back 22

one polar flagellum at one cell end

Front 23

Lophotrichous

Back 23

several at one end

Front 24

Amphitrichous

Back 24

several at both ends

Front 25

Petrichous

Back 25

many all over the cell surface

Front 26

Name 2 genera that produces spores.

Back 26

-Bacillus
- Clostridium

Front 27

Give 4 significance of spores.

Back 27

1. Microbial ecology (allows long term survival in the environment)
2. Food (contamination by spores and subsequent spoilage or food poisoning)
3. Sterilisation (difficult to acheive because of their resistance to nature.
4. Epidemiology (resevoirs in the soil).