lecture 21 Flashcards
(22 cards)
does the pH of the environment effect microbial growth?
yes
what are organisms that grow at high, low, ad neutral pH’s called?
Neutrophils: organisms grow best between pH 6 and 8 (neutral conditions)
Acidophiles: pH 1-5.4 (acidic conditionds
Alkankphile: pH > 9 (basic conditions)
How much more acidic is a pH of 7 vs. 9? Know scale
moving from number to number is 10 times more/ less.
7 to 9 is 100x more basic
How do acidophiles survive the low pH?
Increase the acidity around them by pumping out protons. This makes the outside more acidic around them, this eliminates the competition, melting things for resources, and creates cave system.
What are barophiles?
organisms that thrive under high hydrostatic pressure.
Halophiles? What are three kinds?
They are extremophiles that thrives in high salt concentrations.
- Nonhalophile (slight, 1-7% salt)= no salt
- Moderate Halophiles (7-15% salt)= marine organisms
- Extreme Halophiles (15-30%) = salt!!
What is the difference between complex and defined media?
Complex Media- chemical is an undefined medium or complex medium (ex. nurtient broth or nutrition agar)
Defined (synthetic) Media- chemical composition of the medium is known.
What is the difference between selective, differential, and enrichment media?
Selective Medium- contains ingredients to unhibit certain species’ growth and allow others’ growth
Differential Medium: contains specific chemicals to indicate species that possess of lack a biochemical process
Enriched Medium: very specific
How do you crate a pure culture?
Isolate a single microorganism from a mixed culture, typically using the streak plate method, allowing a single colony to grow, which is then transferred to fresh media for further growth
What is a streak plate vs. pour plate vs. spread plate?
Streak Plate- isolates individual cells to form discrete colonies of species (ex. T-Streak)
Pour Plate (incubation)
1. sample is pipetted on to the surface of agar plate
2. sample is spread out evenly over plate with sterile spreader
result: surface colonies
Spread Plate (solidification and incubation)
1. sample is pipetted into the sterile plate
2. sterile medium is added and mixed well with inoculuim
result: surface and subsurface colonies
-80 degrees Celcuis Freezer vs. Lyophilization
Lyophilization (freeze-drying)
- last long time (room temp.)
- sucking all the water out
- 12 hrs
-80 degrees Celcius Freezer
What is ATCC and what do they do?
American Type Culture Collection (ATCC)
- keep in storage for a long time, and store it
- create and ship it out
True or False: One can perform a direct microscope count using a hemocytometer.
True
How does a Hemocytometer work?
Uses a calibrated grid etched onto a glass slide allowing for manual cell counting under a microscope.
Enabling the determinations of cell concentration and viability in a sample.
Differentiates living (clear) and dead (blue)cells
What are some limitations of a hemocytometer?
- time comsuming
- prine to human error
- limited accuracy for very dilute or high-concetration cell suspensions
How does a Spectrophotometer work? Good for living cells?
Measures the turbidity (cloudiness) of a sample.
Good for high populations, and measure dead too.
generate growth curve.
What is the standard plate count procedure?
Colonies grow on a plate containing a sample of diluted broth.
The number of colonies indicated the orginal number of viable (living) cells in broth.
What is CFU? How is it different then a cell?
CFU = Colony forming unit
unit of measurement that is used to estimate the number of viable cells, or bacteria in a sample.
Colony of cells rather than individual cells.
Why would you do a MPN?
To estimate the number of viable microorganism
What is MPN stand for?
MPN = most probable number
15 test tubes with preset-> add drinking water to tubes
1-5: 10 ml of water
6-10: 1 ml of water
11-15: o.1 of water
When might we use a filter?
particularly membrane filters, are used for sterilization of heat-sensitive solutions, sample preparation, and microbial separation, including water quality testing and isolating specific microorganisms.
