Lecture 4 Basic Microbial Morphology Flashcards
Name the two types of prokaryotic cells
Bacteria
Archaea
Name the most important differential staining method in microbiology
The Gram Stain
Example of gram postive bacteria
Staphylococci
Example of gram negative bacteria
Escherichia coli
Explain the gram stain mechanism
Differential lipid content of G+ and G- cell envelopes
Crystal violet-iodine complex forms within the cells (Blue colour)
What effect does alcohol treatment for gram stain method have on gram negative cell envelope
G- cell envelope has a high lipid content which is extracted by alcohol to permeabilise the memberane
What effect does alcohol treatment for gram stain method have on gram positive cell envelope
G+ cell envelope has low lipid
content and is dehydrated by
alcohol - making it impermeable
Name the bacteria that doesn’t stain using the gram stain method
Mycobacteria
Why don’t Mycobacteria stain using the gram stain method
have a high wax content in their cell envelope
Name the method used to stain mycobacteria
Ziehl-Nielson stain
Name the smallest known bacteria
Mycoplasmas
Why can’t mycoplasma use the gram stain method
They have no cell wall to stain
Name the types of bacterial shapes
Cocci(Spherical)
Bacilli(Rod shaped)
Curved or spiral shaped
Name the structure in a bacterial cell containing the bacterial genetic information
Bacterial chromosome
Other than bacterial genetic information what else is found in the chromosome
Plasmids
Name the structure that surrounds the cytoplasm
Cytoplasmic membrane
Name the rigid layer surrounding the cytoplasmic membrane
Cell wall
Name the structure that cover the cell wall and acts as a molecular sieve for gram negative bacteria
Outer membrane
What is the cytoplasmic membrane primarily composed of
Lipids
Phospholipids
Does cytoplasmic membrane have an osmotic barrier
Yes , only molecules smaller than glycerol diffuse into the cytoplasm
Where is the site of energy production oxidative phosphorylation
Cytoplasmic membrane
How are important molecules transported in cytoplasmic membrane
Via Permeases
Name the types of membrane transport in cytoplasmic membrane
Facilitated diffusion (passive)
Active transport
Where does synthesis of new cell wall occur in bacteria cell
Cytoplasmic membrane
Name the structure that anchor the chromosome of bacteria cell
Cytoplasmic membrane
What is bacteria cell wall composed of
Peptidoglycan
What is Archaea cell wall composed of
Lacks peptidoglycan but composed of other polysaccharides or proteins
Function of cell wall in bacterial cells
Allows cell to withstand turgor pressure and give cell shape and rigidity
from high concentration of dissolved solutes that generate a high pressure within cell caused by cytoplasm pressing again cell envelope
Name the principle component of bacterial cell wall that prevent osmotic lysis
Peptidoglycan
What percentage of cell envelope material is made up of Peptidoglycan layers in gram positive
90% of cell envelope
What percentage of cell envelope material is made up of Peptidoglycan layers
2-20% of cell envelope material
Name the antibiotic that disrupts Peptidoglycan synthesis
Penicillin
What does NAG stand for in Peptidoglycan
N-acetylglucosamine
What does NAM stand for in Peptidoglycan
N-acetylmuramic acid
Which bonds connects NAM and NAG (G-M)
β(1,4) glycosidic bond
Describe cell wall of Archaea
No peptidoglycan
S-layer composed of a ordered layer of protein or glycoprotein Eg(thermophiles, halophiles, methanogens)
Few Archaea contain pseudopeptidoglycan
Repeated sugar units, however, ab1,3-linked) Example: Methanogens
Polysaccharides
Describe gram negative cell envelope outer membrane
Phospholipid-Lipopolysaccharide (LPS)bilayer (extra lipid layer - mechanism of gram stain)
Bacterial cell adhesion
Molecular sieve - access of some molecules to cell wall and cytoplasmic membrane
What is gram negative cell envelope outer membrane resistant to
Phagocytosis
Name the structure that extend from the cell surface
Flagella
Pili
Function of flagellae
They rotate and are required for motility (chemotaxis)
What do bacteria swim towards
Chemoattractants
What do bacteria swim away from
Chemorepellents
What structure do bacteria use to swim
Flagella
what is conjugative pili used for in bacteria cell
Plasmid transfer
what is common pili used for in bacteria cell
Adherence
