Microbial Growth Chp 9 Flashcards
What is the difference between a colony and a biofilm?
A colony is an aggregation of cells from a single parent cell, while a biofilm is a collection of microbes living in a complex community on a surface.
List the steps in biofilm formation.
1) Reversible attachment, 2) Irreversible attachment, 3) Growth & division, 4) EPS production & water channels, 5) Secondary colonization & dispersion.
Why are channels important in biofilms?
They help distribute nutrients, gases, and keep cells hydrated.
What is quorum sensing?
A regulatory mechanism that allows bacteria to coordinate behavior based on population density.
What are the benefits of being in a biofilm?
Protection, communication, and metabolic cooperation.
What are the two main types of culture media?
Solid and liquid media.
What is an inoculum?
Microbes that are intentionally introduced into a sterile culture medium.
How do anaerobic bacteria grow?
Through fermentation, anaerobic respiration, or anoxygenic photosynthesis.
What is the GasPak system?
A sealed jar system that creates an anaerobic environment for bacterial growth.
What is an anaerobic chamber?
A chamber that removes oxygen and replaces it with an oxygen-free gas.
What is generation time?
The time required for a bacterial cell to divide.
What are the four phases of bacterial growth?
Lag, log, stationary, and death phase.
What are the three physical growth requirements?
Temperature, pH, and salt tolerance.
Define minimum growth temperature.
The lowest temperature at which metabolism occurs.
Define maximum growth temperature.
The temperature at which proteins denature and the organism dies.
Define optimal growth temperature.
The temperature at which bacterial growth is fastest.
What are mesophiles and why are they important?
Bacteria that grow at 20-40°C and include many human pathogens.
What are psychrotrophs and why are they important?
Cold-tolerant bacteria like Listeria monocytogenes, which can grow in refrigerated food.
What pH range do alkaliphiles grow in?
pH 7.1-14.
What pH range do neutrophiles grow in?
pH ~7.0.
What pH range do acidophiles grow in?
pH 0-6.9.
What is the difference between macronutrients and micronutrients?
Macronutrients are required in large amounts, while micronutrients are needed in trace amounts.
What are the major elements bacteria need to grow?
Carbon, oxygen, nitrogen, phosphorus, and sulfur.
Define strict aerobe.
Requires oxygen to survive.
Define strict anaerobe.
Cannot survive in oxygen.
Define facultative anaerobe.
Prefers oxygen but can survive without it.
Define microaerophile.
Needs small amounts of oxygen (2-5%).
Define aerotolerant anaerobe.
Can survive with or without oxygen.
What do superoxide dismutase and catalase do?
They break down toxic oxygen byproducts.
What are fastidious organisms?
Organisms that require specific nutrients that must be supplied in their growth medium.
