Intro to Bacteria 1

Question 1

What size is a bacterial cell?

Answer 1

<10um, <2um in length
1/10th of mammalian
large surface area to volume ratio

Question 2

Prokaryotes

Answer 2

typically unicellular
non-compartmentalized
bacteria and archaea

Question 3

Bacterial cell types

Answer 3

coccus, bacillus, spiral bacteria

Question 4

Bacterial Phenotype

Answer 4

total characteristics displayed by an organism under a particular set of environmental factors, including morphology, growth and metabolic functions

Question 5

Common features of all cells

Answer 5

DNA, plasma membrane, cytoplasm, ribosomes

Question 6

Nuclear Material

Answer 6

chromosomal and extra chromosomal DNA
bacterial chromosome circular, linear before cell division
no nuclear membrane
chromosome encodes all essential activities

Question 7

Ribosomes

Answer 7

site of protein synthesis
70S unit with 50S and 30S subunits
target site of antibiotics, aminoglycosides, macrolides and tetracyclines

Question 8

Plasma membrane

Answer 8

essential for survival, retains cytoplasm
selectively permeable, contains receptor molecules
location for crucial metabolic processes

Question 9

Cell wall

Answer 9

sensing/prtoecting/adapting to environmental changes
cell wall determines gram stain reaction

Question 10

Gram stain

Answer 10

stain with crystal violet, wash
mordant dye with potassium iodide, wash
flush with alcohol, wash
G-ve decolorized, G+ve remain purple
counterstain with safranin, wash
G-ve become red, G+ve remain purple

Question 11

Gram positive cell envelope

Answer 11

G+ve cell wall 20 - 80nm thick homogenous peptidoglycan/murein layer
large amounts teichoic acid
connected to peptidoglycan/plasma membrane lipids
negative charge
aids in maintaining structure of wall

Question 12

Peptidoglycan

Answer 12

enormous polymer composed of many identical subunits
2 sugar derivatives, several different amino acids
chains of linked peptidoglycan subunits joined by crosslinks between peptides to give dense interconnected network

Question 13

Gram negative cell envelope

Answer 13

only small amount peptidoglycan, cannot retain stain
outer membrane also has bilayer

Question 14

Lipopolysaccharide

Answer 14

lipid A, core polysaccharide and O side chain
important for cell structure
antigenic variation in O side chain, ecoli
lipid A, toxic, major constituent of outer membrane
smooth vs rough

Question 15

Capsule

Answer 15

layer of material outside the cell wall
capsule layer well organised and not easily washed off
slime layer diffuse unorganised material, not easily washed off
both usually composed of polysaccharides, visible by light microscopy

Question 16

advantages of capsule

Answer 16

non essential
not easily destroyed
virulence factor
resist phagocytosis, toxic substances and infection by bacteriophage
aid attachment to tissue and solid surface
denoted by letter K

Question 17

S-layers

Answer 17

many bacteria
composed of protein/glycoprotein
protect against pH and ion fluctuations, osmotic stress, enzymes
maintain shape and rigidity
promote cell adhesion to surfaces
protect against complement attack and phagocytosis
phenotypic variants

Question 18

Flagella

Answer 18

long, rigid protein structures that provide movement
20nm diameter, special stains for visualisation
filament, basal body, hook
composed of flagellin
denoted by letter H

Question 19

Flagella types

Answer 19

single polar flagellum
multiple polar flagella
peritrichous
virulence factors
essential for colonization

Question 20

Spirochaetes

Answer 20

different flagellar structure
periplasmic flagella rotate counterclockwise along length of cell, cell rotates clockwise about cell and body axis

Question 21

Fimbriae

Answer 21

short fine, hairlike projections
thinner than flagella
not involved in motility
attachment
denoted by the letter F
sex pili: modified, larger

Question 22

Endospore

Answer 22

highly resistant dormant structure
not form of reproduction
survivable mechanism in unfavourable conditions
clostridium and bacillus species
sporulation, germination