Micro 1- microbial growth Flashcards
list 4 types of reproduction
- binary fission
- budding
- sexual reproduction
- fragmentation
binary fission
DNA is copied and cell divides into two equal cells
- most common in bacteria
- asexual
budding
small initial growth that enlarges and then separates
- yeast most common
- asexual
sexual reproduction
- requires two opposite mating strains
- generates diversity
- individual produced is genetically different from parents
- eukaryotic organisms (fungi, protozoa)
fragmentation
filamentous bacteria break off and initiate growth of new cells
generation time
time required for a cell to divide and its population to double (20 minutes to 24 hours)
binary fission and generation time
binary fission doubles the number of cells each generation
total number of cells = 2^(number of generations)
-growth curves are represented logarithmically
4 phases of growth
- lag phase
- log phase
- stationary phase
- death phase
lag phase
intense activity preparing for population growth but no increase in population
-no cell division, prep for growth
log phase
logarithmic or exponential increase in population
note very rapid growth makes bacterial cells more permeable
stationary phase
period of equilibrium, microbial deaths balance production of new cells
death phase
population is decreasing at a logarithmic rate
in what phase is bacteria most susceptible to chemical agents
log (exponential) phase
- because cell wall is not effective barrier at this stage (more permeable and allows for passage of molecules)
- antibiotics take advantage of this
physical requirements for growth (3)
- temperature
- pH
- osmotic pressure
chemical requirements (5)
- carbon
- nitrogen, sulfur, and phosphorous
- trace elements
- organic growth factors
- oxygen
temperature requirements
psychrophiles, mesophiles, thermophiles
psychophiles- cold loving
psychrotrophs (room temp loving- food spoiling)
pH requirements
most bacteria grow between 6.5 and 7.5 pH
(mods and yeasts grow between 5 and 6 pH)
most pathogens are neutrophiles- requiring neutral conditions
osmotic pressure requirements
hypertonic environments (higher in solutes than inside the cell) cause plasmolysis due to high osmotic pressure
extreme/ obligate halophiles
require high osmotic pressure (high salt)
facultative halophiles
tolerate high osmotic pressure
doesn’t need it to survive but can live through it
carbon requirements
- structural backbone or organic molecules
- chemoheterotrophs use organic molecules as energy
- autotrophs use CO2 (some bacteria, protozoa, and algae)
nitrogen requirements
component of proteins, DNA, and ATP
-most bacteria decompose protein materia for the nitrogen source
sulfur and phosphorus requirements
sulfur is used in animo acids, thiamine, and biotin
phosphorus is used in DNA, RNS, and ATP
trace element requirements
- inorganic elements required in small amounts
- used as enzyme cofactors
- include iron, copper, molybdenum, and zinc
