1. A worker at a deli neglects to wash his hands before preparing potato salad. He unintentionally contaminates the salad with 12,000 Salmonella cells. How many bacteria will be present in 12 hours if the generation time is 15 minutes (assume all logarithmic growth)?

2. You determine that a coconut cream pie contains 3 million (3 x 10⁶) Staphylococcus aureus cells. You assume that the food preparer did not wash his hands and probably inoculated the cream with 500 S. aureus. If the pie was made 6 hours ago, (i) how many generations have occurred, and (ii) how long is each generation?

3. Using the generation time from Problem 2, how many S. aureus would be present after eight hours of logarithmic growth?

4. Streptococcus pyogenes (below) are often referred to as "flesh eating bacteria" (it's true, look it up). It is estimated that more than 700 million S. pyogenes infections occur world wide each year, including over 650,000 cases of severe, invasive infections with a mortality rate of 25%. The bacterium can divide every 40 minutes at body temperature. Assume that you fall down and scrape your knee and get infected with five S. pyogenes cells. You think nothing of this minor accident, and avoid seeking medical attention.

i) After 24 hours of logarithmic growth, how many S. pyogenes will be infecting your body?

ii) For every one million S. pyogenes in an infection, a cubic millimeter of flesh is consumed in a day. After 24 hours, how much tissue (in cubic mm) would be lost?