Bacteria Structure, Growth And Taxonomy

Question 1

What are bacteria?

Answer 1

Unicellular ‘free living’ organisms;
Ancient but very successful;
Historically placed in kingdom Protista;

Question 2

Monera (single cell)

Answer 2

Prokaryotes;
Unpaired chromosome;
No nucleus;

2 types - eubacteria and archaeobacteria;

Question 3

Protests (single cell)

Answer 3

Eukaryotes;
Paired chromosomes;
Nuclear structure;

Protozoa and algae/ slime moulds;

Question 4

Prokaryotes VS eukaryotes

Answer 4

Both have nucleic acids, ribosomes, cell membrane;
Eukaryotes have; prokaryotes don’t - structured nucleus, mitochondria, golgi, ER;
Prokaryotes have; eukaryotes don’t - Mesosome, rigid cell wall;

Question 5

Bacteria nomenclature

Answer 5

Genus + Species;

Question 6

Why is bacterial taxonomy important?

Answer 6

Handling information - facilitates storage and retrieval of info through use of databases;
Learning - facilitates learning and understanding large amounts of complex information about diverse organisms;
Communication - makes communication about bacteria more accurate;
Identification - makes identification of unknown bacteria possible;
Evolution - guide to evolution of bacteria - so epidemiological data is understood;

Question 7

Classification of bacteria - phenotypic characteristics

Answer 7

Morphology - macroscopic, microscopic;
Biotyping - biochemical tests;
Serotyping;
Antibiogram patterns;
Pyocin/ phage typing;

Question 8

Classification of bacteria - genotypic characteristics

Answer 8

% G+C ratios;
DNA hybridisation;
Nucleic acid sequence analysis;
Chromosomal DNA fragment analysis;
Ribotyping;

Question 9

Macroscopic (growth on agar medium)

Answer 9

Shape;
Size;
Elevation;
Margin;

Texture - smooth/rough;
Appearance - glistening (shiny) or dull;
Pigmentation - nonpigmented (cream, Tan, white) or pigmented (purple, red, yellow);
Optical density (opaque/translucent);

Question 10

Shapes

Answer 10

Rod;
Club;
Coccus (round);
Curved (vibrio);
Spirillum;
Spirochaete;

Question 11

Arrangement

Answer 11

Individual or groups/clusters/chains;

Question 12

Staining characteristics of gram stain and acid fast chain

Answer 12

Gram chain - true bacteria;

Acid fast chain - mycobacteria

Question 13

Shape of E. Coli

Answer 13

Short rod

Question 14

Shape of Clostridium

Answer 14

Large club like rod;

Question 15

Shape of Strep/staph

Answer 15

Coccus (round)

Question 16

Staining characteristics - gram stain

Answer 16

Differentiates bacteria on the basis of cell wall structure;
Generally first line test in diagnosis of bacterial infections - gram result/size and shape of bacteria can be definitive for a particular genus of bacterium; empirical antibiotic treatment;
Gram positive - thick cell wall;
Gram negative - thin cell wall;

Question 17

Gram positive example

Answer 17

Staphylococcus

Question 18

Gram negative example

Answer 18

E. coli

Question 19

Staph. Aureus is found in clusters or individually?

Answer 19

Clusters

Question 20

E.coli is found in clusters or individually?

Answer 20

Individual

Question 21

Cell envelope characteristics of gram negative VS gram positive

Answer 21

Gram positive - thicker cell wall, no outer membrane, has teichoic acid, has some strains of sporulation, sometimes has capsules, sensitive lysozyme, more susceptible to penicillin;

Gram negative - thinner cell wall, has outer membrane, no teichoic acid, no sporulation, sometimes has capsules, lysozyme not sensitive, less susceptible to penicillin;

Question 22

Functions of the cell wall

Answer 22

Maintain rigidity and cell shape/structure - peptidoglycan (mesh like exoskeleton);
Maintain osmolarity - prevent osmotic lysis;
Survival - interacts with host cell membranes;
Cell division - forms cross-wall separation 2 Daughter cells;

Question 23

Bacterial cell wall synthesis

Answer 23

Peptidoglycan precursor synthesized inside the cell;
Exported across cell membrane X bacitracin;
A site is created in existing wall by enzymic action (PBPs);
The new nucleotide minus the terminal D-ala is encorporated;
Cell grows;

Question 24

Different cell wall morphologies - mycobacterium

Answer 24

Mycobacterium tuberculosis;
Modified peptidoglycan layer;
Covalently attached to arabinogalactan polymer;
Mycolic acid waxy coat - lipids;
Poor gram stain;

Question 25

Mycoplasma

Answer 25

No cell wall;

Cell membrane contains steroids (host);

Question 26

Cell membrane

Answer 26

Lipid bilayer - hydrophobic;
Similar gram positive and gram negative bacteria;
No steroids (except mycoplasma);
Mesosome - cell division;
Ion transport and energy production (mitochondria);
Energy production (ETC);

Question 27

Other morphological features of bacteria

Answer 27

Spores;
Capsules;
Flagella;
Fimbriae (pilli)

Question 28

Spores

Answer 28

Cell survival in adverse conditions;
Desiccation, heat and starvation;
In gram positive only;
Eg. Clostridium, Baccilus

Question 29

Capsules

Answer 29

Protection against phagocytosis;
Gram positive and gram negative;
Gelatinous material - polysaccharide/polypeptide;

Question 30

Flagella

Answer 30

Cell motility;
Coiled in structure;
1-20;
Polar or peritrichous;
Protein (flagellin);
Anchored in bacterial membranes;
Chemotaxis;
Movement by ATP-driven motor membrane potential;

Question 31

Fimbriae (pilli)

Answer 31

Smaller length +diameter;
Peritrichous arrange;
Protein (pilin);
Sex pilli;
Adherence (adhesion);
100+;
Not coiled;
E. Coli

Question 32

Morphological virulence factors - gram negative

Answer 32

Pilli;
Inflammatory response;
Cytokines/septic shock;

Question 33

Morphological virulence factors - gram positive

Answer 33

Teichoic acids;
Surface protein;
Inflammatory response;
Cytokines/shock;

Question 34

Growth characteristics (Physical)

Answer 34

Oxygen/ carbon dioxide;
Temperature;
Light;
PH;
Osmolarity;
Water;

Question 35

Growth characteristics (nutritional requirements)

Answer 35

Carbon source;
Nitrogen source;
Organic compounds;
Inorganic salts (Fe/Na/K/P/Ca/Mg);

Question 36

Medical relevance

Answer 36

Cell wall synthesis - antibiotics - penicillin, vancomycin;
Capsules - vaccines;
Cell membranes - antibiotics, vaccines;
Ribosomes - antibiotics;