Growth in colonies paralelles that in liquid medium, exceptthat most growth occurs at the edge of the colony, and all phases of growth simultaneously somewhere in the colony. 3. Measuring bacterial growth = measuring bacteria concentration at certain time points Serial dilution: Successive 1:10 dilutions of a liquid culture of bacteria are made and tranfered onto an agar plate; the colonies that arise are counted. Colony Forming Unit, CFU = number of colonies from 1 ml of liquid culture x times of dilution. Direct count: Use a (hemocytometer). Can not Petroff-Hausser counting chamber determine if living. Most propable number (MPN) Filtration Measuring OD600nm: Use a spectrophotometer to measure light obsorption that represents turbidity. This is the only method that can monitor the growth in real time and harvest cells at the log phase, which is necessary in a series of experiments. II. FACTORS AFFECTING GROWTH 1. Physical factors All bacteria have optimum of the following. temperature pH (Effect of buffer is to reduce change in pH) O2 level moisture nutrients salt or pressure Obligates and trophiles: Obligate aerobes: Must have O2; e.g. Pseudomonas Must have no O2; e.g. Obligate anaerobes*: Clostridium botulium Faculative anaerobics): Grow well with O2 and grow less well without O2 ; e.g. E. coli, Staphylococcus
Growth in colonies paralelles that in liquid medium, exceptthat most growth occurs at the edge of the colony, and all phases of growth simultaneously somewhere in the colony. 3. Measuring bacterial growth = measuring bacteria concentration at certain time points Serial dilution: Successive 1:10 dilutions of a liquid culture of bacteria are made and tranfered onto an agar plate; the colonies that arise are counted. Colony Forming Unit, CFU = number of colonies from 1 ml of liquid culture x times of dilution. Direct count: Use a Petroff-Hausser counting chamber (hemocytometer). Can not determine if living. Most propable number (MPN) Filtration Measuring OD600nm: Use a spectrophotometer to measure light obsorption that represents turbidity. This is the only method that can monitor the growth in real time and harvest cells at the log phase, which is necessary in a series of experiments. II. FACTORS AFFECTING GROWTH 1. Physical factors All bacteria have optimum of the following. temperature pH (Effect of buffer is to reduce change in pH) O2 level moisture nutrients salt or pressure Obligates and trophiles: Obligate aerobes: Must have O2; e.g. Pseudomonas Obligate anaerobes*: Must have no O2; e.g. Clostridium botulium Faculative anaerobics): Grow well with O2 and grow less well without O2 ; e.g. E. coli, Staphylococcus
Chapter%20Summary%20II.docx