Bacterial growth and counting
What has more bacteria when measured with a spectrophotometer, a sample with 45% transmission or a sample with 65% transmission?
45%
What is the layer of secretions that surrounds microbes in a biofilm called?
EPS (can be 50-90% of the biofilm!)
This is the term for bacteria that grow with and without oxygen but better with oxygen
Facultative anaerobe
colonies throughout media = pour
colonies only on surface= spread
While most bacteria reproduce by binary fission, what are some alternatives?
budding, fragmentation, multiple fission (splitting more than once before dividing)
How many colonies do you look for during serial dilution with plate count?
30-300 (some resources say 25-250)
Can grow on catheters etc. and are difficult to kill
This is the term for bacteria that like high carbon dioxide levels
capnophile
What is a chemostat?
a bioreactor that allows continuous growth of bacteria by adding nutrients and removing wastes
800
What advantage would fluorescence staining have over directly counting microbial cells?
can distinguish live from dead cells
free floating (planktonic) bacteria adhere to a surface
This is the term for organisms that like cooler temperatures such as 15 deg C, but can grow in your frig which is around 4 C
psychrophiles
What is a Coulter counter?
allows measurement of electrical resistance in a culture to analyze population size
How do you estimate populations from MPN results?
Name the four stages of binary fission
cell elongates, DNA replicates, septum, cells separate
What is a density-dependent chemical communication system that bacteria use to coordinate gene expression? It has been well studied in biofilm.
quorum sensing
This is an enzyme that converts hydrogen peroxide to water and oxygen
catalase
What is MPN and how is it used?
Most Probable Number, a statistical, culture-based technique used to estimate the number of viable microorganisms (especially coliforms) in water, food, or soil, particularly at low concentrations
What are pros and cons of dry weight to estimate population size?
pro: eliminates water variability
con: destructive
Name the four stages of bacterial population growth
lag log stationary death
Why do microbes form biofilms?
Survival! Helps with nutrient cycling and protection
Media that enhances growth of some microbes and inhibits other is known as
selective
How do you grow an obligate anaerobe?
stab a culture deep, use an anaerobic jar or chamber, old way=candle jar
You need to grow an organism that is a halophile, alkalophile, and thermophile. What do you need to provide it?
salt, basic pH, and heat