Bacteria

Question 1

Bacterial shapes

Answer 1

Coccoid - spherical or ovoid

Bacilli - Rod/cylindrical (can be short, fat, long, thin, or drumstick shapped.

Vibro - curved, helical, spiral shaped

Question 2

Cell Arrangement

Answer 2

Diplo - paired
Stretpto- chains
Staphylo - clusters
Tetrads -

Only used in describing Cocci

Question 3

Gram staining procedure

Answer 3

Primary stain (blue/violet) stains gram +ve
Mordant (Gram’s stain) - increases affinity of primary stain
Decolorizer (alcohol &/or acetone) - removes stain of -ve
Counterstain (safranin) - stains gram -ve cells red.

Question 4

Acid Fast Stain

Answer 4

Used on gram resistant bacteria (Mycobacterium, Nocardia)

• Ziehl-Neelsen Staining (hot) - basic carbolfuchsin; decolourize with acid-alkali. stains acid fast bacteria RED, others blue/green
• Kinyoun Stain (cold) same as above
• Fluorochrome - yellow/green stain against black background. Counterstain: potassium permanganate

Question 5

Flagellum Arrangements

Answer 5

• Monotrichous - one flagella on one side
• Amphitrichous - two flagella on each end. (4 total)
• Lophotrichous - two flagella on one end
• Peritrichous - nonpolar, multiple flagella at various locations.

Question 6

Flagellar components & movement

Answer 6

Helical filament: inserted into hook (flagellin - H antigen)
Basal Body: rod and 1 (+ve) or 2 (-ve) sets of double rings
L, P rings = Bushing (-ve only)
S, M rings = Rotor (both)

Rotation of basal plates CCW result in smooth swiming motion

CW direction flagella disperse (tumbling)

Question 7

Chemotaxis

Answer 7

Chemical receptor proteins attract or repel

• Positive response: organism swims from low to high concentrations
• Negative response: down concentration gradient
• Non response: random walk/ uniform concentration

Question 8

Glycocalyx

Answer 8

Capsule, Slime Layer, or S-Layer

• Slime Layer: poor organized, weak attach. to cell wall
• Capsule: organized, adhere to cell wall (K Antigen)

Fxn: antiphagocytic, adherence to surfaces, toxicity, protection, prevention of leukocyte migration.

Question 9

Quelling Reaction

Answer 9

• Swelling Reaction: Capsule presence by microscopy
• Antiserum + Bacteria = Swelling
• Specific antisera: capsular (K/M) antigens for TYPING

Question 10

Cell Wall

Answer 10

All bacteria (except Mycoplasma)

Peptidoglycan backbone: alternating NAG & NAM for rigidity and strength (4th peptide cross-link to 3rd peptide of adjacent polypeptide)

Question 11

NAM 3rd peptide gram -ve

Answer 11

Diaminopimelic Acid ( <60% cross-linked)

Question 12

NAM 3rd peptide gram +ve

Answer 12

L-Lysine. ( >90% cross-linked)

Question 13

Gram Positive Baceria

Answer 13

Thick peptidoglycan layer  (thick cell wall) containing
TEICHOIC ACIDS (Lipoteichoic acid- antigenic causing tissue necrosis, stimulation of compliment, hypersinsitivity) atop phospholipid bilayer

Question 14

Gram Negative Bacteria

Answer 14

Outer membrane containing porins (protein channels) and Lipopolysacc. (Endotoxin) atop Thin peptidoglycan layer atop inner membrane

Question 15

Endotoxin

Answer 15

Produces fever, necrosis, RBC lysis, TNF production, activation of alternative complement pathway

Lipopolysacc. form:

• O-antigen (40 repeat units)
• Core polysaccharide
• Lipid A (toxic)

Lipooligosacc form is missing O-antigen

Question 16

Periplasmic Space

Answer 16

Space between outer and inner membrane in gram negative bacteria. gel-like area with loose-network of peptidoglycan. May contain Axial Filaments

Question 17

Acid-Fast Bacteria

Answer 17

Peptidoglycan + arabinose & galactose polymers =
Arabinogalactan + esterification = mycolic acids (waxy) 60%
Sits atop cytoplasmic membrane

Question 18

Effects of Lysozyme

Answer 18

breaks beta 1-4 bonds between NAM & NAG. Destroying all or part of the cell wall. More effective against gram +ve bacteria due to lacking outer membrane

Question 19

Sphereoplast

Answer 19

Gram -ve bacteria upon exposure to lysozyme retaining portions of its cell wall. (portions remain due to inner and outer membrane)

Question 20

Protoplast

Answer 20

Gram +ve bacteria upon exposure to lysozyme resulting in complete removal of cell wall

Question 21

Transpeptidases

Answer 21

Penicillin Binding Proteins

Question 22

Effect of Penicillin

Answer 22

prevents cell wall formation, Inhibits formation normal cross-linkages in Peptidoglycan.

greater affect on gram +ve due to high cross-linking.

Question 23

Bacterial cytoplasmic membrane

Answer 23

Phospholipid bilayer, semi-permeable barrier, No sterols

Question 24

Axial Filaments

Answer 24

Endoflagellum, motile features in bacteria that lack flagella. located in periplasmic space

Question 25

Pathogenicity Islands

Answer 25

Distinct genetic elements on bacterial chromosomes that code virulence factors.

Often unstable, located near tRNA genes, and associated with transposons.

Question 26

R Plasmid

Answer 26

coding antibiotic resistance

Question 27

F Plasmid

Answer 27

coding mating capabilities (F-pilus)

Question 28

Endospores

Answer 28

Means of survival of Bacillus and Clostridium bacteria in extreme or depleted environmental conditions.

Resistant to UV, irradiation, chemical disinfection, drying

Coat (keritan-like), Cortex (peptidoglycan type), Spore Wall (peptidoglycan), Core (genetic material, etc)

Question 29

Sporulation

Answer 29

Spore to vegetative bacteria