Components of the Prokaryotic Cell and their Relationship to Disease
(Ability to cause, diagnose of, treatment, etc…)
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Glycocalyx
o Capsule form prevents phagocytosis and therefore allows the bacterium to cause disease
o Also may allow the bacterium to adhere to host tissues
o Allows some cells to form biofilm
Flagella
o Allow cells to move to target tissues
o The H antigen protein can be used to distinguish between strains for identification (E.
coli H7:0157)
Axial filaments of spirochetes allow the bacterium to move through bodily fluids
Fimbriae function in attachment forming biofilm and attachment to bodily surfaces (N.
gonorrhoeae and E. coli H7:0157)
Conjugation pili allow cells to exchange DNA in a process called conjugation (may give
antimicrobic resistance to the other cells)
Cell Wall
o Site of action of penicillin (prevents the formation of new peptidoglycan by interfering
with the linkage of peptidoglycan rows by peptide cross-bridges)
o Site of action of lysozyme (hydrolyzes the bonds between NAG and NAM
o Other antibiotics, such as beta-lactams enter more easily through the OM of G- cell walls
and are more effective than other antibiotics
o Polysaccharides in streptococci group them into medically important types
Gram + cell walls
o Gram stain used to identify for diagnosis and treatment options
o Teichoic acids are antigens and can be used to diagnose Gram + types of bacteria
Acid fast cell walls (Mycobacterium) contain a waxy substance that can be differentially stained
for diagnosis
Gram – cell walls
o Gram stain used to identify for diagnosis and treatment options
o Outer membrane of Gram – bacterial cell walls
 Contains LPSs (an endotoxin) –
 Lipid A portion (embedded in lipid of OM) when released, causes fever,
dilations of blood vessels, shock, blood clotting
 O polysaccharide (sticking out into outer environment) is an antigen and
can be used to diagnose specific types of bacteria (E. coli H7:0157)
o OM is another semipermeable structure capable of restricting the movement of antibiotics
and other harmful substances from entering the cell
o OM has a strong negative charge which helps the cell evade our defense system (inhibits
phagocytosis and complement)
Plasma membrane
o A semipermeable structure that may prevent some antimicrobics from entering the cells
o Detergents and some disinfectants (alcohols and quaternary ammonium compounds)
disrupt the lipid bilayer
o Some antibiotics (polymyxins) cause leakage through the plasma membrane and cell
death
o Glycoproteins and glycolipids serve as binding sites
DNA: bacterial chromosome or plasmids
o May contain genes for resistance or virulence factors
o May be transferred to other cells through transformation or conjugation
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May be the site of action of antibiotics or other antimicrobics (sulfa drugs)- prevention of
DNA synthesis will not allow the cell to reproduce
Ribosomes
o Function in protein synthesis- many antibiotics function to prevent or disrupt protein
synthesis specifically in bacteria (streptomycin, tetracycline)
Inclusions
o Specific inclusion materials may be specific to certain cells and therefore used for
diagnostic purposes
Endospores
o Allow cells to survive in the presence of many substances and in environments that
would normally kill the vegetative cell
o Important in the food industry (for example, boiling does not destroy the endospore for
many hours)
Enzymes – Often the site of antimicrobic agents
o Denature proteins
o Enzyme inhibition