9. bacteria structure growth and taxonomy

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Taxonomic ranks

Answer 4

Kingdom

Division

class

family

genus

species

Question 5

bacteria nomenclature

Answer 5

binomial: genus+species

Question 6

why is bacterial taxonomy important?

Answer 6

handling info

learning

communication

identification: unknown

evolution

Question 7

how are bacteria classified

Answer 7

•Phenotypic characteristics

–Morphology: Macroscopic, Microscopic

–Biotyping – biochemical tests

–Serotyping

–Antibiogram patterns

–Pyocin/Phage typing

•Genotypic characteristics

–%G+C ratios

–DNA hybridisation

–Nucleic acid sequence analysis eg MLST

–Chromosomal DNA fragment analysis

–Ribotyping

Question 8

bacteria classification: macroscopic

Answer 8

growth on agar medium: Shape, Margin, Elevation, Size

–Texture

–Appearance

–Pigmentation

–Optical density

•Opaque/translucent

Question 9

microscopic classification

Answer 9

morphology of single cells

shape, arrangment, size, staining characteristics

Question 10

morphology of staphyloccoci

Answer 10

cocci (round), clusters (grapes)

Question 11

morphology of streptococci

Answer 11

coccus: round

chains

Question 12

morphology of bacilli

Answer 12

rods

Question 13

Answer 13

Question 14

why are gram stains used as a first line for diagnoses of bacterial infections?

Answer 14

the result can be definitive for genus of bacterium

gram +ve: thick cell wall

gram -ve: thin cel wall

Question 15

Answer 15

Question 16

function of a cell wall

Answer 16

•Maintain rigidity and cell shape/structure

–Meshlike linked exoskeleton - peptidoglycan

• Maintains osmolarity: prevent osmotic lysis
• Survival: Cell wall interacts with host membranes

•Cell division: Forms cross-wall separating two daughter cells

Question 17

bacterial cell wall synthesis

Answer 17

•Peptidoglycan precursor synthesised inside the cell

NAG/ NAM linked to lipid carrier- taken through cell membrane to new cell wall X bacitracin

intergrated into wall by enzymes (transpeptidase) create space then linked into existing structure

• The new nucleotide minus the terminal D-ala is encorporated
• Cell ‘grows’

Question 18

cell wall morphology of mycobacterium

Answer 18

–Modified peptidoglycan layer

–Covalently attached to arabinogalactan polymer

–Mycolic acid waxy coat - lipids

–Poor Gram stain

–Acid fast (Zeihl-Neelsen stain) - carbolfuchsin

Question 19

cell wall morphology of mycoplasma

Answer 19

–No cell wall

–Cell membrane contains steroids (host)

Question 20

cell membrane features

Answer 20

• Lipid bilayer - hydrophobic
• Similar Gram +ve and –ve bacteria
• No steroids (except mycoplasmas)
• Ion transport and energy production (mitoch
• Mesosome - cell division
• Electron transport (energy production)

Question 21

other (special) cell membrane features

Answer 21

•Spores

–Cell survival in adverse conditions

–Desiccation, heat, starvation

–Gram +ve only eg Bacillus spp./All Clostridium spp.

•Capsules

–Protection against phagocytosis

–Both Gram +ve / Gram –ve

–Gelatinous material, polysaccharide/polypeptide

•Flagella: chemotaxis, flagellin protein,

•Fimbriae (pili): pilin and adhesin

–E.coli (UTI)

–N.gonorrhoeae

–Sex pili (F plasmid)

Question 22

Morphological virulence factors in gram negative

Answer 22

•LPS (LOS)

–Lipid A/core polysacc.

–Shedding – Meningos

–Inflammatory response

–Cytokines/Septic shock

• Porins
• Pili (N. gonorrhea)

Question 23

Morphological virulence factors in gram positive

Answer 23

• Teichoic acids
• Lipoteichoic acids
• Peptido. Fragments
• Surface protein

–Afimbrial adhesins

–Protein F (Strep. pyogenes)

• Inflammatory response
• Cytokines/shock

Question 24

growth characteristics: physical

Answer 24

–O2/CO2

–Temperature

–Water

–pH

–Light

–Osmolarity

Question 25

Growth characteristics: nutritional requirements

Answer 25

–Carbon source

–Nitrogen source

–Inorganic salts (Fe/Na/K/P/Ca/Mg)

–Organic compounds (a-a’s?)