Ch 6 Microbial Growth

the numbers to cells not to the changes in the size of the cells

accumulations of the cells large enough to be visible without a microscop

• physical - temperature, pH, osmotic pressure
• chemical - carbon, oxygen, sulfur, nitrogen

media infused with certain chemicals to accommodate certain bacteria

many growth factors required

used to grow most heterotrophic microbes

often has thio (sulfur) chemicals

suppresses growth of unwanted bacteria

distinguish between types of bacteria

dehydrated / freeze dried bacteria

time needed to undergo binary fission

phase where bacteria is gathering materials; preparing for division; some division

phase where there is rapid division

phase where rate of reproduction = rate of death

rapid death of the bacteria

• count colonies
• quebec colony counter
• serial dilutions
• direct microscopic counts

assume that 1 bacteria formed the colony (CFU = colony forming unit)

count typical amount of colonies in the appropriate size box and multiply by the number of boxes that fit the plate

• decrease concentration to be able to do direct count
• must multiply colonies by dilution number

put colonies in liquid on a microscope slide

• spectrophotometer
• metabolic products
• dry weight

• measures absorbency or transmission (turbidity)
• turbidity is caused by bacteria

determine how much bacteria by knowing how much of a product is produced by 1 bacteria

dry bacteria up and weigh

cold loving

middle temperature loving

heating loving bacteria

cell shrivels

cell explodes