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Binary Fission A process where two identical daughter cells arise from the splitting of their mother cell Budding A process where one small daughter cell pops out of the larger mother cell Viable Plate Count Laboratory process that dilutes samples and grows them on agar plates then counts the number of colonies on the plates and uses that to calculate the number of viable bacteria in the sample Shortcomings of the Viable Plate Count Not all living bacteria in a sample form distinct colonies and therefore they are not counted Phases of Microbial Population Growth Lag Phase Logarithmic Phase Stationary Phase Death Phase Lag Phase Time where bacteria are adapting to their new environment and seeing what nutrients and toxins are present Logarithmic Phase Phase where microbes are doubling in a giving time forming an exponential increase in population size Generation Time Time it takes for a microbial population to double What Phase of Microbial Population Growth is Most Susceptible to Antibioticis? Logarithmic phase What Phase of Microbial Population Growth is Best for Gram Staining? Logarithmic Phase Stationary Phase The population is in equilibrium (# new cells = # cell deaths) What Phase of Microbial Population Growth does sporulation take place? Stationary Phase Death Phase Due to a build up of toxins or use of all the nutrients, all the cells begin to die in the microbial population Nutrients Required for Microbial Growth Iron Growth Factors Purines and pyrimidines Amino acids Vitamins Siderophores Iron-scavenging peptides produced by bacteria that have a higher affinity for iron compared to human proteins Auxotrophy Organisms are unable to synthesize their own growth factors Mesophiles Organisms that prefer to grow at temperatures between 30C and 37C Neutrophiles Organisms that prefer to grow at pHs between 5.5 and 8.0 Common pathogen that prefers an alkaline environment: Vibrio cholerae Osmotolerant Organism is able to live in high solute concentrations Common pathogen that is osmotolerant: Staphylococcus aureus (salt tolerant) which is why it grows on the skin Haloduric Salt tolerant Enzymes that microbes use to degrade ROS Superoxide dismutase Catalase Peroxidase Obligate Aerobes Require oxygen for metabolism because they use the TCA cycle and the ETC with oxygen as the final electron acceptor (can't use other electron acceptors) Microaerophiles Require some oxygen but cannot tolerate atmospheric levels Examples of microaerophiles Campylobacter Helicobacter Facultative Organisms Can switch between aerobic and anaerobic energy generation Aerotolerant Anaerobes Do not use oxygen in their metabolism but can grow in the presence of oxygen Strict Anaerobes Cannot survive in oxygen environment and also, therefore they cannot detoxify ROS and they have to use fermentative pathways Sporulation When conditions are poor, some bacteria will form endospores which make them heat, chemical, and radiation resistant Bacteria that can form endospores Bacillus Clostridium