Flashcards in Microbiology Deck (17)
What are the three domains into which life is switch?
What are the main pathogens that can affect humans?
What is virulence?
The level of infectivity of a pathogen
The bacterial cell wall is composed of _____
What is peptidoglycan ?
The main constitute of a bacterial cell wall
It is essential in sugar caging- repeating polysaccharide structure with peptide cross links- providing a rigid structure and barrier
What two types of bacterial cell wall exist?
(There are also bacteria without a cell wall)
How are gram positive and negative bacteria differentiated ?
By performing a gram stain
What is a gram stain?
A test used to differentiate between gram positive and negative bacteria
Crystal violet dye is used to stain the cell wall- specifically the peptidoglycan layer
The extent to which the dye is retained determines the type of bacteria
Gram positive- thick peptidoglycan layer- stay purple
Gram negative- thin peptidoglycan layer- turns pink
Gram positive bacteria have a _____ peptidoglycan layer allowing them to deal with _____ internal pressures.
Of both gram positive and negative which of the toe has a larger periplasmic space?
Gram negative ( they have two different periplasmic spaces)
Which bacteria class has two membranes?
(outer and plasma)
What exists on the outside of gram negative bacteria that confer antigenic properties?
Lipid polysaccharides (endotoxins)
Besides having antigenic properties, what other important characteristics do lipid polysaccharides possess?
They have bacterial toxin properties which cause damage to neighbouring cells and evoke an inflammatory response
Why are gram positive bacteria more susceptible to antibiotics?
The outside peptidoglycan layer can act as a target for antibiotics such as penicillin
What happens when antibiotics bind to the peptidoglycan layer of gram positive bacteria?
The peptide cross links within peptidoglycan are broken down
What are flagella and fimbriae (pili)?
Extracellular proteinaceous extensions