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
what does the nutrient: phosphorus, help function?
Nucleic acids
synthesis of ATP
synthesis of cell membrane
what does the nutrient: sulfur, help function?
sulfur containing amino acids (which are needed to build specific proteins)
vitamins
what do trace elements help function? (iron, copper, zinc, molybdenum)
cofactors for enzyme function
how can oxygen in the atmosphere be toxic?
when oxygen accepts excess electrons, it becomes a radical
oxygen radicals can interfere with other (metabolic functions?)
what are two forms of oxygen radicals?
superoxide anions (radicals)
peroxide anion (hydrogen peroxide)
what is the enzyme that detoxifies superoxide anions?
superoxide dismutase (SOD): neutralizes radicals to O2 and H2O2
what happens when you pour hydrogen peroxide on a cut? why?
catalase found in our body break down hydrogen peroxide into oxygen and water which looks like foam when hydrogen peroxide is poured onto a cut in order to NEUTRALIZE TOXIC OXYGEN IMPORTANT
what are two enzyme that detoxifies peroxide anion?
catalase: creates water and O2
peroxidase: creates two water molecules
How are superoxide anions formed?
in small amounts during normal respiration
what is another name for peroxide anion?
hydrogen peroxide
know examples of organic growth factors
describe obligate aerobes
NEED oxygen to survive; will always produce catalase and SOD
describe facultative anaerobes
can grow in oxygen and without; will have catalase and SOD
describe obligate anaerobes
can only grow in an environment without oxygen; lack enzymes because they will never form toxic oxygen radicals
describe aerotolerant anaerobes
can tolerate oxygen presence but grow in anaerobic conditions; presence of SOD
describe microaerophiles
only grow in aerobic conditions BUT in small amounts
describe how we usually measure bacterial growth
generation time: how long it takes for one cell to divide into two cells
A short generation will cause what to happen
more microbes to grow faster
A longer generation time will cause what to happen?
less microbes to grow
what are the four phases of bacterial growth?
lag phase
log phase
stationary phase
death phase
describe lag phase
there is little or no cell division (cell is figuring out its environment)
describe log phase
exponential growth phase
acclimated to environment
describe stationary phase
of new cells is equal to # of dead cells
use up nutrients
describe death phase
of deaths is more than # of new cells
what does drinking salt water when sick cause to happen?
drinking salt water creates a hypertonic solution which causes bacteria plasmolysis
A longer generation time will cause what to happen?
less microbes to grow
