1. Clostridium and Streptococcus are both catalase-negative. Streptococcus grows by fermentation. Why is Clostridium killed by oxygen, whereas Streptococcus is not?
2. Assume that after washing your hands, you leave ten bacteria cells on a new bar of soap. You then decide to do a plate count of the soap after it was left in the soap dish for 24 hours. You dilute 1g of the soap 1:106 and plate it on standard plate count agar. After 24 hours of incubation, there are 168 colonies. How many bacteria were on the soap? How did they get there?
3. Why is each of the following bacteria often resistant to disinfectants?
1. Mycobacterium
2. Pseudomonas
3. Bacillus
4. Explain why gram-negative bacteria are more resistant to biocides than gram-positive bacteria. Be specific and descriptive in your response. A description of the differences between gram-negative and gram-positive bacteria should be included, along with an explanation of why any of those differences would have anything to do with the actions of biocides.