Appendix A – Cell Division in Bacteria
After reading Ch. 6 in Microbiology: Principles and Explorations, fill in the following matrix.
List the four phases of bacterial growth and briefly describe what happens in each phase.
Lag phase: Is the period when the bacteria are adjusting to the environment.
Log phase: Is when the population grows in a logarithmic fashion.
Stationary phase: a substance that shows different affinities for different components in sample mixture in a separation of the mixture by chromatography.
Death phase: Bacteria dies, characterized by a steady decline in population numbers from starvation and or high toxin concentrations.
List and describe at least four methods used to measure bacterial growth.
Direct Cell counts
Viable Cell Counts
Measuring Cell Products
List at least two physical factors that influence bacterial cell growth. Briefly describe how bacterial growth responds to changes in those factors.
PH: Most spoilage bacteria grow best near neutral pH. The optimum pH range is usually quite narrow so that changes in the pH can have a large effect on the growth rate of the organism.
Temperature: An increase in temp will increase enzyme activity. If temp gets too high enzyme activity will diminish and the proteins. Cycles of freezing and thawing can denature proteins.
Oxygen concentration: The paradoxical nature can be both toxic and essential to life. Obligate Aerobes rely on aerobic respiration for ATP and they use oxygen as the terminal electron transport chain. Microaerophilic require O2 from growth but they are damaged by normal atmospheric levels of oxygen and don’t have efficient ways to neutralize the toxic forms of oxygen such as superoxide ad hydrogen peroxide. Obligate anaerobes will die in the presence of oxygen because they lack enzymes like superoxide dismutase and catalase. Light: vital for