CBSE Microbiology - Basic Bacteriology (Questions And Answers)
What is a bacterial pilus / fimbria? How does it differ in chemical composition and function
from bacterial flagellum? ~ It is an appendage of the bacterium, just like the flagellum.
However, it is made of glycoprotein, whereas flagellum is made of protein. Also, it is used
for adherence of the bacteria to cell surfaces, whereas the flagellum is used for motility.
Note--the pilus is used during bacterial conjugation! "The sex pilus".
What is a bacterial spore composed of? ~ A keratin-like coat, dipicolinic acid,
peptidoglycan, and DNA.
Do bacterial spores exist in gram negative or gram positive bacteria? ~ Only gram
positive
What is the function of the bacterial spore? ~ It is for survival; it resists dehydration,
heat and chemicals.
What are the components of the bacterial cell envelope? ~ Capsule, glycocalyx, outer
membrane, periplasm, cell wall and cytoplasmic membrane.
What is the chemical composition of the capsule? What is the function? ~ It's an
organized, discrete polysaccharide layer which protects against phagocytosis
In what bacteria is the capsule slightly different chemically? ~ In B. Anthracis -- the
poly-D-glutamate
What is the chemical composition and function of the glycocalyx? ~ It's a loose network
of polysaccharides which mediate adherence to surfaces, especially foreign surfaces, for
example, catheters.
What are the two layers of the outer membrane and what is each made of? What are the
proteins embedded in the outer membrane? ~ 1. The outer leaflet--has endotoxin! LPS /
LOS. 2. Inner leaflet: phospholipids. The outer membrane has embedded proteins: porins
and other OMPs--outer membrane proteins.
Which bacteria type contains an outer membrane? ~ Only Gram (-)
What structures in the outer membrane are antigenic and what is their MoA? ~ Most
OMPs and the O polysaccharide component of Endotoxin (endotoxin MoA: lipid A induces
TNF-alpha and IL-1)
What is the function of porins in the outer envelope? ~ Transport across the outer
membrane
, What is the periplasm, what does it contain, and in which bacteria type is it found? ~
ONLY in gram (-) bacteria. It is the space between the cytoplasmic membrane and the outer
membrane, and it contains peptidoglycans.
What does the periplasm do? ~ It accumulates components leaving the cell, including
hydrolytic enzymes like beta-lactamases.
What is the chemical composition and structure of the cell wall? ~ Peptidoglycan sugar
backbone with peptide side chains cross-linked by transpeptidase. It is a net-like structure
that gives rigid support, protects against osmotic pressure damage.
What is the chemical composition of the cytoplasmic membrane? What does it contain in
Gram (+)ive bacteria? ~ PL bilayer sac with embedded proteins (eg penicillin binding
proteins). *Contains lipoteichoic acids in gm (+) bacteria. These are extensions that extend
from the membrane to the exterior of the whole cell.
What is the function of the cytoplasmic membrane? What structure in the membrane is
antigenic? ~ Oxidative and transport enzymes are here; PBPs involved in cell wall
synthesis are also here, and lipoteichoic acids induce TNF and IL-1
What structures are found only in gm (+) bacteria ~ lipoteichoic acid
What structures are found only in gm (-)? ~ porins, endotoxin / LPS, periplasmic space
(beta-lactamase location!)
Staphylococci ~ Spherical gm (+)
Streptococci ~ Spherical gm (+)
Neisseria ~ Spherical gm (-)
Moraxella catarrhalis ~ spherical gm negative
Bacilli ~ gm positive rod
clostridium ~ gm pos rod
corynebacterium ~ gm pos rod
gardnerella ~ gm pos rod - gram variable*
lactobacillus ~ gm pos rod
listeria ~ gm pos rod
mycobacterium ~ gm pos rod - acid fast
What is a bacterial pilus / fimbria? How does it differ in chemical composition and function
from bacterial flagellum? ~ It is an appendage of the bacterium, just like the flagellum.
However, it is made of glycoprotein, whereas flagellum is made of protein. Also, it is used
for adherence of the bacteria to cell surfaces, whereas the flagellum is used for motility.
Note--the pilus is used during bacterial conjugation! "The sex pilus".
What is a bacterial spore composed of? ~ A keratin-like coat, dipicolinic acid,
peptidoglycan, and DNA.
Do bacterial spores exist in gram negative or gram positive bacteria? ~ Only gram
positive
What is the function of the bacterial spore? ~ It is for survival; it resists dehydration,
heat and chemicals.
What are the components of the bacterial cell envelope? ~ Capsule, glycocalyx, outer
membrane, periplasm, cell wall and cytoplasmic membrane.
What is the chemical composition of the capsule? What is the function? ~ It's an
organized, discrete polysaccharide layer which protects against phagocytosis
In what bacteria is the capsule slightly different chemically? ~ In B. Anthracis -- the
poly-D-glutamate
What is the chemical composition and function of the glycocalyx? ~ It's a loose network
of polysaccharides which mediate adherence to surfaces, especially foreign surfaces, for
example, catheters.
What are the two layers of the outer membrane and what is each made of? What are the
proteins embedded in the outer membrane? ~ 1. The outer leaflet--has endotoxin! LPS /
LOS. 2. Inner leaflet: phospholipids. The outer membrane has embedded proteins: porins
and other OMPs--outer membrane proteins.
Which bacteria type contains an outer membrane? ~ Only Gram (-)
What structures in the outer membrane are antigenic and what is their MoA? ~ Most
OMPs and the O polysaccharide component of Endotoxin (endotoxin MoA: lipid A induces
TNF-alpha and IL-1)
What is the function of porins in the outer envelope? ~ Transport across the outer
membrane
, What is the periplasm, what does it contain, and in which bacteria type is it found? ~
ONLY in gram (-) bacteria. It is the space between the cytoplasmic membrane and the outer
membrane, and it contains peptidoglycans.
What does the periplasm do? ~ It accumulates components leaving the cell, including
hydrolytic enzymes like beta-lactamases.
What is the chemical composition and structure of the cell wall? ~ Peptidoglycan sugar
backbone with peptide side chains cross-linked by transpeptidase. It is a net-like structure
that gives rigid support, protects against osmotic pressure damage.
What is the chemical composition of the cytoplasmic membrane? What does it contain in
Gram (+)ive bacteria? ~ PL bilayer sac with embedded proteins (eg penicillin binding
proteins). *Contains lipoteichoic acids in gm (+) bacteria. These are extensions that extend
from the membrane to the exterior of the whole cell.
What is the function of the cytoplasmic membrane? What structure in the membrane is
antigenic? ~ Oxidative and transport enzymes are here; PBPs involved in cell wall
synthesis are also here, and lipoteichoic acids induce TNF and IL-1
What structures are found only in gm (+) bacteria ~ lipoteichoic acid
What structures are found only in gm (-)? ~ porins, endotoxin / LPS, periplasmic space
(beta-lactamase location!)
Staphylococci ~ Spherical gm (+)
Streptococci ~ Spherical gm (+)
Neisseria ~ Spherical gm (-)
Moraxella catarrhalis ~ spherical gm negative
Bacilli ~ gm positive rod
clostridium ~ gm pos rod
corynebacterium ~ gm pos rod
gardnerella ~ gm pos rod - gram variable*
lactobacillus ~ gm pos rod
listeria ~ gm pos rod
mycobacterium ~ gm pos rod - acid fast
