6: Microbial Growth Flashcards
increase in the number of cells, not the size of the cells
microbial growth
groups of cells large enough to be seen without a microscope, hundreds of thousands of accumulated cells
colonies
many bacteria survive and grow slowly in nutrient-poor environments by doing what?
forming biofilms
frequently sources of health care associated infections
biofilms
serratia marcesens
example of biofilm forming bacteria
3 physical requirements for microbial growth
temperature, pH, and osmotic pressure
can grow between -9c and 19c, but optimum growth around 15c and usually are found in the arctic regions or in the ocean’s depths
psychrophiles
temperature optima from 20-30c and are frequently responsible for low-temperature food spoilage
psychrotrophs
moderate-temperature-loving microbes, optimum growth around human body temp 37c
mesophiles
many pathogenic and most food spoilage microbes belong to this temperature category
mesophiles
heat-loving microbes, 50-60c, temp of hot tap water
thermophiles
Why don’t bacteria grow well in cold temperatures?
reduced enzyme activity from reduced brownian motion
can be found in warm soil, themal hot springs, and compost piles
thermophiles
can grow near boiling point of water 100c in hot springs, members of archaea
extreme thermophiles, hyperthermophiles
The ____ of thermophilic bacteria are unusually heat-resistant and may survive the heat treatment of canned goods.
spores
