Microbiology: Bacterial Structure & Function

Front 1

What are the subjects of study of microbiology?

Back 1

1) viruses,

2) bacteria,

3) algae,

4) fungi,

5) protozoa (single-celled eukaryotes)

Front 2

What are the 3 Domains of life?

Back 2

1) Archaea (prokaryotic cells) > {not human pathogens};

2) Bacteria (prokaryotic cells) > {majority of pathogenic microorganisms};

3) Eukarya (eukaryotic cells) > {contain kingdoms: fungi, plants, animals, protists}

Front 3

Differences between prokaryotes/eukaryotes

Back 3

1) prokaryotic cells are not compartmentalised, but eukar. cells are.

> prokar. - no nuclear membranes, mitochondria, endoplasmic reticulum, Golgi body, phagosomes, & lysosomes.

2) prokaryotes -> single circular chromosome (nucleoid) & no membrane-bound nucleus.

3) eukar. ribosomes are larger than prokar. (80S vs 70S).

4) bacterial (-> prokar.) membranes - no sterols (e.g. cholesterol)

Front 4

Does a typical bacterium contain nucleus?

Back 4

No. It contains a nucleoid - a nuclear region containing a single long (1mm) chromosome, but no nucleus.

Front 5

What are the types of bacterial cell arrangement?

Back 5

1) in 1 plane (Diplococci & Chain);

2) in 2 planes (Tetrad);

3) in 3 planes (Cluster).

Front 6

Why is cell wall important for bacterial cells?

Back 6

1. it confers structure, rigidity & shape;

2. it protects bacteria from osmotic lysis (bursting of cell because of excess fluid).

Front 7

Why do many antibiotics target cell wall specifically?

Back 7

Selective toxicity.

Cell walls are unique to prokaryotes, mammal cells do not synthesize them, and so, are immune to the toxic effect of targeted antibiotics.

Front 8

What is Peptidoglycan?

Back 8

It is a polymer which makes up the cell wall of bacteria.

# consists of 2 sugars (NAG & NAM [> unique to bacterial cell walls]) cross-linked by amino acid (peptide) bridges.

# the more peptide cross-linking there is, the more rigid cell wall is.

Front 9

Gram stain - what is it?

Back 9

A way to distinguish between the 2 large groups of bacteria with different structures of cell walls.

Front 10

What is binary fission & the consequences of it?

Back 10

Binary fission - bacterial cell division where 1 cell splits into 2.

Consequence: no genetic diversity

> it leads to: >

# bacteria cannot adapt to rapid environmental changes,

# antibiotics work

Front 11

Where is the cromosomal replication initiated in bacteria & where does it start?

Back 11

# initiated at the membrane,

# starts in the Origin of Replication.

Front 12

What type of organisms can produce endospores?

Back 12

only Gram +ve

Front 13

What are capsules, and what do they allow pathogens to do?

Back 13

Capsule - a form of bacterial structure. It is often an important determinant of virulence.

Capsules...

# protect a bacterium from drying, trap nutrients;

# enable some bacteria to resist phagocytic engulfment by white blood cells;

# allow to adhere to surfaces (eg. root hairs, teeth) & resist flushing.

>> essential, eg., for Streptococcus mutans/pneumoniae

Front 14

What are pili & what do they allow bacteria to do?

Back 14

Pili - protein tubes in the cytoplasmic membrane.

Pili...

# adhere to glycolipid/glycoprotein receptors on host cells & colonise.

Front 15

Where are pili found?

Back 15

# virtually all gram -ve bacteria,

# few gram +ve bacteria.

Front 16

What are flagella and what is their role in bacteria?

Back 16

Flagella - bacterial organs of locomotion.

they allow:

# to find source of nutrition;

# to penetrate host mucus.

Front 17

What is the cell wall structure of gram +ve bacteria?

Back 17

- Peptidoglycan (outer layer)

- Plasma membrane

Front 18

What is the cell wall structure of gram -ve bacteria?

Back 18

- Outer membrane

- Peptidoglycan (layer is thinner than in gram +ve)

- Periplasmic space

- Plasma membrane

Front 19

Colour of gram -ve stain?

Back 19

pink

Front 20

Colour of gram +ve stain?

Back 20

Purple