Intro to Bacteria

Question 1

List some parts of a bacterium

Answer 1

Capsule, cell wall, cytoplasmic/inner/plasma membrane, ribosomes, single chromosome (no nucleus), flagellum, fimbriae

Question 2

explain the cytoplasmic/plasma membrane of bacterial cells

Answer 2

thin, elastic and semi-permeable membrane around bacterial cell contents

Question 3

What lies ouside the cytoplasmic membrane of bacterial cells

Answer 3

the cell wall - rigid, giving cell strength and shape but is permeable

Question 4

What is the outer membrane a component of

Answer 4

the gram negative cell wall

Question 5

Gram positive bacteria

Answer 5

bacteria that have a thick peptidoglycan cell wall, and no outer membrane

Question 6

gram negative bacteria

Answer 6

Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. Gram-negative bacteria are typically more resistant to antibiotics than Gram-positive bacteria

Question 7

What colours do gram +ve and gram -ve bacteria stain

Answer 7

Gram positive - purple
Gram negagtive - pink (red)

Question 8

why are mycobacteria not reliably stained by gram stain

Answer 8

due to the large lipid content in the cell wall

Question 9

shape of cocci under microscope

Answer 9

spherical

Question 10

shape of bacilli under microscope

Answer 10

rod shaped

Question 11

How can bacteria appear under a microscope

Answer 11

may be spiral or corkscrew, spherical or rod shaped, can exist as single cells, chains or clusters

Question 12

Explain the bacterial cytoplasmic membrane in more detail

Answer 12

• Composed of phospholipids and proteins
• Allows the passage of water and uncharged small molecules but otherwise forms a barrier
• Proteins oif membrane have number of functions:
• transport systems for specific nutrients and ions
• as enzymes involved in processes such as energy generation, cell wall synthesis and DNA replication
• Sensing proteins that measure concentrations of molecules in the environment

Question 13

Explain the bacterial cell wall

Answer 13

• made of peptidoglycan: N-acetylglucosamine acid and Nacetylmuramic acid molecules linked alternately in a chain, with short peptides forming cross-links
• thick, strong and relatively rigidmaintains shape
• several antibiotics interfere with the construction of cell wall peptidoglycan -e.g. penicillan?

Question 14

what happens if the cell wall is weakened or ruptured?

Answer 14

osmosis means the cell will swell and burst -termed lysis

Question 15

role of cell wall in cell division

Answer 15

The cell wall plays an important part in cell division ie cross-walls form prior to separating into 2 daughter cells

Question 16

Describe the Lipopolysaccharide (LPS) outer membrane

Where is it present, function, structure…

Answer 16

• only present in Gram negative bacteria
• protects peptidoglycan from bile salts (in the gut), also from lysozyme
• blocks many antibiotics getting into the cell
• lipid A (within LPS) forms endotoxin, which, when released into the bloodstream (when multiplying or when lysed), may give rise to endotoxic shock -fever and low blood pressure

Question 17

WHat is the bacterial capsule

Answer 17

the polysachharide layer found outside the cell wall

Question 18

How do bacteria replicate and how does genertic variation arise

Answer 18

• replicate by binary fission (identical progeny)
• Genetic variation by: spontaneous mutation, transfer of DNA

Question 19

Bacterial conjugation

Answer 19

Conjugation is the process by which one bacterium transfers genetic material to another through direct contact. During conjugation, one bacterium serves as the donor of the genetic material, and the other serves as the recipient.

Question 20

What are bacteriophages

Answer 20

viruses that can infact bacteria

Question 21

Bacterial Ribosomes

Answer 21

• Consist of RNA and associated proteins
• function is to synthesise proteins
• divided into subunits - measurement is by the Svedberg unit, a measure of sedimentation rather than size
• bacteria have a 70S ribosomes, with large (50S) and small (30S) subunits. The small 30S subunit has itself a subunit, called 16S.

dont think you need to know the non-bold bits :)

Question 22

How can we detect and culture:
* individual bacteria
* colonies of individual bacteria

Answer 22

• individual bacteria: can only be seen with a microscope, use a stain (e.g. gram/flourescent dyes)
• colonies of individual bacteria: cultured on a solid medium (agar), can be see by eye

Question 23

How can we classify bacteria

Answer 23

Phenotypically (observable physiocal properties) or genotypically (relating to DNA)

Question 24

Give examples of phenotypic bacterial classification

Answer 24

• gram stain
• growth requirements eg aerobic, anaerobic, microaerophilic
• serologic
• mass spectrometry (protein profiling)

Question 25

Give examples of genotypic bacterial classification

Answer 25

• ribosomal RNA sequence analysis
• whole genome sequencing

Question 26

bacterial nomenclature

Answer 26

• name based on genus and species
• strains of a species have similar characteristics
• DNA typing techniques is used to identify strains

Question 27

Flagella

Answer 27

Flagellum is primarily a motility organelle that enables movement and chemotaxis. Bacteria can have one flagellum or several, and they can be either polar (one or several flagella at one spot) or peritrichous (several flagella all over the bacterium).

Question 28

Fimbriae

Answer 28

Fimbriae are long filamentous polymeric protein structures located at the surface of bacterial cells. They enable the bacteria to bind to specific receptor structures and thereby to colonise specific surfaces - ADHESION AT EPITHELIAL SURFACES

Question 29

Bacterial spores

Answer 29

A spore is a cell that certain fungi, plants (moss, ferns), and bacteria produce. Spores are involved in reproduction. Certain bacteria make spores as a way to defend themselves. Spores have thick walls

Question 30

Penicillin binding protein

Answer 30

Penicillin-binding proteins are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria