EFFECT OF OSMOTIC PRESSURE ON MICROBIAL GROWTH Flashcards
T/F:
Growth of bacteria can be affected by the amount of water entering or leaving the cell
TRUE
What is a hypotonic?
It has low solute content with a higher osmotic pressure in the cell
Does water flow INTO the cell or OUT under hypotonic conditions?
It flows INTO the cell
Why do bacterias that are supported by cell walls, do not rupture under hypotonic conditions?
They are resistant to lysis, because the cell becomes turgid and strong
What happens when the bacteria is placed in a hypertonic solution?
It will have high solute content (water would flow out the cell), and their growth is inhbited
What happens in a media of growth inhibiting osmotic pressure?
The cytoplasm becomes dehydrated and shrinks away from the cell wall
What is the term called when the cell membrane shrinks and detaches from cell wall?
Plasmolysis/the cell is plasmolyzed
What is the purpose of the effect of osmotic pressure excercise?
To test the degree of inhibition of organisms that results with media containing different concentrations of sodium chloride
What are the 3 broth cultures used?
- Escherichia coli
- Staphylococcus aureus (lvl 2)
- Halobacterium salinarium
Which species showed growth under 0.5-5% NaCl?
E.coli and S. aureus
Which showed Red pigment growth in 25% NaCl?
Halobacterium salinarium
Why are bacteria generally resistant to hypotonic environments whereas animal cells are not?
Bacteria have cell walls that resist osmotic pressure that causes cell to swell
How do hypertonic environments negatively affect most bacterial cells?
causes water to diffuse out of cells & cause plasmolyzed
Why are staphylococci well suited for colonization of skin?
They are halotolerant
Explain how foods can be preserved using salt or sugar?
It increases osmotic pressure, destroying certain bacteria and slows decay
