Bacterial Structures & Functions Flashcards
Staphylococcus, Streptococcus & Bacillus are Gram ___
+
E. Coli and several spirochetes are Gram ____
-
bacteria name with sphere shape
coccus/cocci
bacteria with stick or rod shape
bacillus/bacilli
bacteria with spiral long hair shape
spirochete/s
staphylo-
cluster
strepto-
string or chain
diplo-
double
Example of Staphylobacilli
Staphylobacilli bacteria do not exist
Anatomy of a bacterial cell
- plasma membrane
- cell wall
- capsule
- pilus
- flagellum
note: a bacteria will have a plasma membrane; composition or presence of cell wall varies; bacteria may or may not have capsule/pilus/flagellum
bacteria cell envelope
includes everything that s tethered to the bacteria cell from the cell membrane outwards
- cell membrane (inner plasma membrane)
- peptidoglycan layer
- outer membrane (for Gram -)
Is the extracellular polysaccharide capsule a part of the bacterial cell envelope?
No
Gram + stains
purple
Gram - stains
pink/red
The only type of bacteria that does not have peptidoglycan
mycoplasma
bacteria cell wall contains
everything beyond the plasma membrane
components of cell wall in Gram - bacteria
- Thin peptidoglycan layer
- outer membrane
- outer leaflet composed of Lipid A
- LPS (embedded in outer membrane)
Where is the peptidoglycan layer in Gram - bacteria
between the inner and outer membranes
Which group of bacteria have an outer membrane?
unique to Gram - bacteria
LPS is unique to
Gram - bacteria
What is LPS
- Lipopolysaccharide
- bound to Lipid A
- core sugars +/- repeating O-antigen
- known as an endo-toxin
Components of cell wall in Gram + bacteria
thick peptidoglycan later containing LTA (lipoteichoic acid)
Mycoplasma spp.
- No cell wall at all (just plasma membrane)
- Pleomorphic (many different shapes)
Mycobacterium spp.
-Thick, waxy outer-membrane like surface containing mycolic acid and unusual sugars
Mycolic acid is found in
Mycobacterium
Does Mycoplasma have peptidoglycan?
No
Does Mycobacterium have peptidoglycan?
Yes (recall it has a cell wall)
Stain used for Mycobacterium
Acid-fast stain
Gram stain doesnt hold because of mycolic acid
Capsule
- Gelatinous coverings exterior to the peptidoglycan (G+) or outer membrane (G-)
- Composed of polysaccharide
- Protect bacteria from phagocytosis
Feature of many bacteria that cause pneumonia and/or meningitis
Capsule
Pili/fimbriae
- Filamentous appendages
- Composed of multiple protein subunits
- Mediate attachment to host and bacterial cells
- Permit exchange of genetic material between bacterial cells
- Twitching motility & biofilm formation
- Important feature on many Gram - pathogens
Flagellum
- Filamentous appendages, larger in diameter and longer than pili
- Can be on G+ and G-
- Composed of multiple protein (flagellin, a.k.a. H-antigen) subunits attached to a complex molecular motor
- Important for locomotion
Which two antigens are described in this strain designation: E. coli O157:H7
Saccharides in LPS: Flagellin
Is Lipid A an antigen?
No - it is not recognized because it is not a surface protein/extracellular; it’s in the outer membrane of gram - bacteria just under the LPS antigens that stick out from it (the saccharides sticking out from LPS is O-antigen)
Examples of encapsulated bacteria
- Streptococcus penumoniae (G+)
- Neisseria meningtidis (G-)
- Haemophilus influenzae (G-)
