Bacterial Cells Flashcards
Importance of bacterial cell wall for biochemists
Fragments can have immunostimulatory and cytotoxic properties
Cell wall metabolism is a target for current and future antimicrobials
Provide the barrier preventing other antimicrobials reaching their target
What is used for phylogenetic studies
16S rRNA gene
As highly conserved between different species of bacteria and archaea
Traditional identification of bacteria
On the basis of phenotypic characteristics
16S rRNA gene
The gene that encodes the RNA component of the smaller subunit of the bacterial ribosome
The 16s gene is highly conserve and is implicated in the binding of transfer RNA to messenger RNA
It can be independently routinely used for identification of mycobacteria, and can lead to the recognition of novel pathogens and noncultured bacteria.
3 types of bacteria
Gram positive
Gram negative
Mycobacterium
Gram staining results
Gram positive = purple
Gram negative = pink
Technique of gram staining
Applying a primary stain (crystal violet) to a heat-fixed smear of a bacterial culture.
The addition of iodide, which binds to crystal violet and traps it in the cell
Rapid decolorization with ethanol or acetone
Counterstaining with safranin.
Peptidoglycan structure
Beta-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid (NAG NAM)
Carbohydrate backbone
Amino acid cross linking
Enzymes involved in peptidoglycan synthesis and remodelling
Incorporation
Peptide bond formation
Carbohydrate bond formation
Lipid II synthesis
ESKAPE
The acronym ESKAPE includes six nosocomial pathogens that exhibit multidrug resistance and virulence: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. Persistent use of antibiotics has provoked the emergence of multidrug resistant (MDR)
Gram positive vs gram negative
Gram-negative bacteria are surrounded by a thin peptidoglycan cell wall, which itself is surrounded by an outer membrane containing lipopolysaccharide.
Gram-positive bacteria lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than is found in the Gram-negatives.
Where is lipid II synthesised
Cytoplasm of bacteria
Amidase
Breaks amide bond in peptidoglycan when cell is dividing
Beta-Lactam antibiotics
DD-transpeptidase inhibitors
Lipid II
The peptidoglycan precursors are synthesized into lipid II in the cytoplasm.
This is “flipped” across the membrane by the transport lipid (undecaprenyl phosphate).
The glycosyltransferase (GT51) catalyses polymerization of the nascent peptidoglycan chain from lipid II.
