Chapter 6 (EXAM 2) Flashcards
Viable count
The number of microorganisms in a particular media that are alive
Total count
The number of microorganisms in a media that are both living and dead`
Generation time
The time for a cell to divide and population to double; species specific
The rate is always constant \
What is the growth curve and its phases
The curve of microorganisms in unnatural environment, not soil or water
Phases are lag, log, stationary and death
Lag phase
Little to no division of growth in bacteria
Turn genes on that were silences
Once they’ve gotten enough food they move to next phase
Log phase
Exponential increase in population
Industrial producers will create a condition of hemostatic environment(constant)
Stationary phase
When resources become scarce, the number of dying cells dont equal the number of cells dividing
At the end you see less growth, organisms are smaller then normal
Death phase
Organisms planning for death of population and produce endospores if the bacteria is able to
What phases are exponential
Log and death
What are plasmids
What bacteria pick up at later stationary phase and beginning of death phase in desperation to survive.
Tiny circles of genetic material that contain genes of resistance
What are growth influences of cells
Cells require water bc it aids in diffusion of materials
Like less then 1% salt, about .85 NacI
Applies to most bacteria except staph and hydrophilic archer bacteria can tolerate higher salt solutions
what does it mean to be phacotactive
Be on a needs basis with or without salt
Isotonic
Same on the outside as it is on the inside
Hypertonic
Enviroment is more concentrated in solutes on the outside
Water goes out cell then what’s inside the cell
Hypotonic
Solution cell is in is more watery compared to what’s inside of the cell. Cells take more water in
Describe psychrophiles
Cold organisms that can live btwn -10 & 20
15 being optimum temp
Describe psychrotrophs
Cold loving organism that can go in fridge range in 0-30
25 being optimum temp
Describe mesophils
Live within 10-50 range
37 being their fav temp ( body temp)
Describe thermophils
Like warm temp. Live in compost piles, dump, heat resistance
Live in 40-72 range, 62 being their fav temp
Describe hyperthermophils
Type of archer, extreme bacteria
Like temperature of 67-110, 94 being fav temp
Media: broth
Test tubes filled with liquid
media: slant
Test tubes with agar at an angle, cuts down contamination
media: deep
Test tube with media that goes straight across. You use a needle to push bacteria down under the surface to activate anaerobic enzymes
media: buffer
Added to medias to counteract the effect of acids
synthetic media
made of pure chemicals
complex media
contain foods, peptones
What is Agar
Polysaccharide from algae, jelly
Used in media to mountain moisture to prevent dehydrating and freezing at certain temps
selective media
Allows the growth of 1 microorganism over the other
Examples are EMB, Pea agar and Maconkey
What is an EMB
selective media, that allows gram - to grow over gram+
What is a PEA agar
Comes with or without blood, selective for gram +
Why is counting microbes important
It helps determine how bad food is or how intense an infection may be
Ways to count include direct: streak plate, pour plate, spread plate, serial dilutions, filtration, MPN, chambers and culture counter
indirect: spectrophotometer, metabolic
What are colonies
Time mounds of bacteria that contain 100’s of bacteria that create a colony. Have special characteristics
Plate has to be streaked tp create the colonies
What is a streak plate
When small amount of bacteria is placed on a plate
Create 4 quadrants but bacteria is only aseptically applied once.
IT is not a direct count, more of a ball park guess of number of colonies
What is the pour plate method
Bacterial dilution 1.0-0.1 ml
The disadvantage of this is that bacteria can be destroyed and appear different under than they do above. Hard to identify
1. inoculate an empty plate
2. Add melted agar
3. Swirl to mix
4. Colonies grow underneath(facultative anaerobe) or onto of the agar
What is the spread plate method
Same as the put plate method except you spread out the organisms on the surface with beads and colonies grow only on the surface
What are serial dilutions
Goal is 30-300 colonies on a plate, to do this dilutions need to be done
1:100= 1 ml added to the 9 ml of broth
The number of colonies will get lower the more the inoculum is diluted but easier to count bacteria in those
What is filtration
When filters are placed to trap bacteria flowingg in air or water
The filters that trap bacteria are placed on Petri dish to get food to grow, they are then counted and identified
What is MPN
Method that fives you a very wide range of possible number of microbes that can grow in combinations of test tubes containing nutrient agar
10ml= 5 bacteria
1 ml= 3 bacteria
0.1= 1 bacteria
Gives us a number of positive tubes and most possible number of bacteria
Not done often
What is the petfroff houser chambers
A specified volume under a coverslip on top is a grid to count the number of bacteria
The disadvantage is that it counts living and dead bacteria, and any bacteria with tails can swim underneath the surface and not be counted
What is the Coulter counter
Is used if you don’t want to plate out bacteria
Fluids can pass through and instruments are used to count the number of bacteria. Is useful in research labs and hospitals when you want to know immediately the bacteria count
Disadvantage is that other particles that aren’t bacteria can be counted aswell
What is a spectrophotometer
Indirect count
Measures the % of light that passes through a solution and tells you the approximate amount of particles that may be in the solution
It is important to dry and weigh so you can get an accurate number when it come to fungi bc they are masses of fibrous particles
What is metabolic counting
indirect count
Where you measure inout and output. You can take a guess of how many microbe may be there if you know how much food you fed and what kind of organisms it may be
Can also count carbon dioxide and acids
How do salts and sugars preserve food
They create a hypertonic enviroment
What is facultative anaerobe on a graph
Has a with and without line, v shape facing north east
In the bacterial growth curve, which phases are logarithmic
Log and death phase
Most bacteria grow In what ph
7, neutral
What is the generation time in bacteria
The time it takes for a cell to divide
What phase are antibiotics effective
Log phase
3 cells and ended with 192 cells, how many generations
6
What do you call an organism that can live with or without salt
facultative halophile
What do you call an organism killed by oxygen
obligate anaerobe
