Bacteria And Viruses Flashcards
Describe Gram staining.
Positively charged crystal violet binds to negatively charged cell components.
Iodine forms large complexed with crystal violet.
Acetone or methanol extract the complexes through gram-negative but not gram-positive cell walls.
A red dye stains the unstained gram-negative cells.
What is the difference between gram positive and am negative cells?
Gram positive cells have a thicker peptidoglycan layer and no outer membrane, gram negative cells have a thinner peptidoglycan layer and also have an outer membrane.
Why are spores resistant to treatment?
They can go into a dormant state.
What do staphylococci bacteria look like?
Aggregations of circular shaped bacteria.
What do streptococci bacteria look like?
Chains of circular bacteria.
What do diplococci bacteria look like?
Pairs of bacteria.
Which bacteria can’t be visualised with Gram stain?
Mycobacteria (use acid fast instead), auramine (use fluorescent stains), mycoplasms (no peptidoglycan), treponemes, rickettsia and chlamydia (too small).
Which cocci are gram positive?
Staphylococcus and streptococcus.
Which cocci are gram-negative?
Neisseria.
Which bacilli are gram-positive?
Clostridium.
Which bacilli are gram-negative?
Escherichia, salmonella, helicobacter, pseudomonas, legionella, bactericides.
Are RNA or DNA viruses more stable, why?
DNA viruses are more stable, DNA is more stable so less likely to mutate.
Which viruses contain lipids?
Enveloped viruses.
What is a capsid?
The protein outer coat of a virus.
What is required for a virus to successfully infect and replicate in a cell?
A receptor for the virus to bind to (ligand on the virus binds to the receptor).
