Chapter 6 Microbial Growth Flashcards
what does microbial growth refer to?
the number of cells / nothing to do with the individual size
what are colonies in term of microbes?
groups of cells large enough to be seen without a microscope
what does the population refer to?
billions of cells of the same species
how are growth temperature ranges defined?
every microbe grows best in certain temperatures. we categorize them based on their
- minimum growth temperature
- optimum growth temperature
- maximum growth temperature
what are the different classes of microbes that like to grow at different temps?
psychrophiles: cold-loving
mesophiles: moderate-temperature loving
thermophiles: heat-loving
what temperature do psychrophiles grow in vs their optimum growth temp?
0° Celsius
15° Celsius
what temperature do psychrotrophs grow in vs their optimum growth temp?
0° Celsius
20-30° Celsius
what temperature is mesophiles’ optimum growth temp?
25-45° Celsius
what temperature is thermophiles optimum growth temp? What is the lowest temp they can grow in?
Optimum growth temperature: 50-60°C
Cannot grow below: 45°C
what is hyperthermophiles optimum growth temp?
Optimum growth temperature: 80°C or higher
what class of microbes are most likely to contain microorganisms that are human pathogens?
Because mesophiles can grow in room temperature and body temperature, they are MOST likely to be pathogens and cause spoilage of food or disease
which microbe class is the most common?
mesophiles
other than mesophiles, what other organisms can cause human harm?
pyschrotrophs can cause low temp food spoilage
what is the danger range of temp that bacteria are rapidly growing and may produce toxins?
15 - 50°C
what is the optimum pH range for bacteria?
6.5 - 7.5
what is the optimum pH range for Molds and Yeast?
5 - 6
what do acidophiles refer to and what is their optimum pH?
acid-lover
2 or below
Describe the process of plasmolysis
Hypertonic environment means there are more solutes outside the cell walls, than there are inside. Osmotic pressure causes fluid to escape out of the cell wall. this process is what makes up plasmolysis (similar process to crenation of blood cell)
what does halophiles refer to?
salt-loving; they REQUIRE salt for growth
what is the difference between facultative halophiles and extreme halophiles?
facultative halophiles: can tolerate 2% salt - at most 15%
extreme halophiles: require 30% salt for growth
why do cells not normally survive under salty conditions?
salty conditions means more solutes outside of the cell than inside (hypertonic solution) when in a hypertonic solution, the fluid inside of cells leaves outside of the cell wall due to osmotic pressure and the cell goes under plasmolysis and ruptures
what nutrients are needed for major cellular functions?
carbon
nitrogen
sulfur
phosphorus
oxygen
trace elements
what does the nutrient: carbon, help function?
makes up the structural backbone of living matter
what does the nutrient: nitrogen, help function?
DNA and RNA production
protein synthesis
