Lab Exercise 13: Growth Curve OBJECTIVES 1. Bacteria Growth Rate Formula: N t = N 0 * ( 1 + r) t where: N t: The amount at time t N 0: The amount at time 0 r: Growth rate t: Time passed Understand and perform direct measurement of bacterial growth through serial dilutions and standard plate counts. malama.hawaii.edu/teachers/TLunsford/safety/Growth_curve.htm For science fair I tested the growth of bacteria (Escherichia coli) with food preservatives: vinegar, salt and sugar. bacterial cells, if a growth curve for the conditions used has already been established. Understand and perform indirect measurement of bacterial growth through spectrophotometer readings and optical density measurements. When plotted on a graph, a distinct curve is obtained referred to as the bacterial growth curve. The growth of a bacterial population can be graphed as the increase in the number of cells as a function of time and this graph draws a curve called the “bacterial growth curve”, in which several phases are distinguished where different characteristic processes occur. Method of Obtaining Bacterial Growth Curve A population growth curve for any particular species of bacterium may be determined by growing a pure culture of the organism in a liquid medium at a constant temperature. If we were to convert our vertical axis to a logarithmic scale - as on the graph at right - we will not need as many sheets of graph paper, and we will find that a steady rate of growth is reflected as a straight line. Bacterial Growth. The vinegar showed the most no growth area. Bacterial growth in a flask — or any other container which can be as big as an industrial fermenter — holding a growth supporting medium is known as a batch culture. Graphing of bacterial growth with cell number on a log scale. Graphs illustrating population growth during the log phase for a bacterial sample with an initial population of one cell and a doubling ti­me of 1 h. When plotted on a semilogarithmic scale (meaning the values on the y-axis are loga­rithmic), the growth rate appears linear. Dear Clare, firstly you should plot OD600 nm vs time graph for your bacteria. Other methods, such as viable plate counts, can also be used for determining bacterial growth curves but … In reality, exponential growth is only part of the bacterial life cycle, and not representative of the normal pattern of growth of bacteria in Nature. 2. Know the different phases of a standard growth curve. Alternatively, you can measure turbidity, which is the amount of bacteria in your sample. If I wanted to graph it would I have to use a certain graph or just a regular bar graph? 3. Then in log phase of growth the slope of linear part can be calculated. This is the most common method used to rapidly estimate bacterial numbers. The easiest way to measure bacterial growth is to put your sample on a clear glass plate under a microscope and count how many bacteria cells there are.