1. How would you obtain a pure culture of a microorganism from a soil sample containing many different species of bacteria? 2. The following data was obtained during a growth curve: Time (min) OD of culture 0 0.05 10 0.05 20 0.07 30 0.10 40 0.13 50 0.20 60 0.23 70 0.24 80 0.24 Plot the data using a linear scale for time and a logarithmic scale for the culture OD. (There is semi-log graph paper in the back of this manual). If you are unfamiliar with semi-log plots the following information may help you. The horizontal scale on this type of graph paper is the familiar linear scale; but the vertical scale is logarithmic. Thus numbers which increase exponentially if plotted on this scale will appear linear. Try this using the following series of numbers (horizontal numbers are given first and the vertical numbers to go with them are given second): 0,1; 1,2; 2,4; 3,8; 4,16; 5,32. These data are graphed on the next page. When using semi-log paper you must choose the particular range you wish to use. You could have the bottom cycle from 0.01 to 0.1, the next cycle from 0.1 to 1.0 and the next cycle from 1 to 10, etc. or whatever you choose. On your bacterial growth curve, identify lag, log, and stationary phase. What is the doubling time of the culture in log phase? Biology 422L Laboratory 2 Bacteriological Techniques Objectives: 1) To continue to practice sterile technique until it becomes easy for you to do. 2) To observe the growth of bacteria and see how to test the effect of a substance on bacterial growth. 3) To observe bacteria in the light microscope and learn how to do a Gram stain. 4) To use the technique of streaking plates which you learned in Experiment 1 to separate a mixed culture of bacteria. The ability to do this is often needed in a microbiology laboratory. References: Slonczewski and Foster, Chapter 4
1. How would you obtain a pure culture of a microorganism from a soil sample containing many different species of bacteria? 2. The following data was obtained during a growth curve: Time (min) OD of culture 0 0.05 10 0.05 20 0.07 30 0.10 40 0.13 50 0.20 60 0.23 70 0.24 80 0.24 Plot the data using a linear scale for time and a logarithmic scale for the culture OD. (There is semi-log graph paper in the back of this manual). If you are unfamiliar with semi-log plots the following information may help you. The horizontal scale on this type of graph paper is the familiar linear scale; but the vertical scale is logarithmic. Thus numbers which increase exponentially if plotted on this scale will appear linear. Try this using the following series of numbers (horizontal numbers are given first and the vertical numbers to go with them are given second): 0,1; 1,2; 2,4; 3,8; 4,16; 5,32. These data are graphed on the next page. When using semi-log paper you must choose the particular range you wish to use. You could have the bottom cycle from 0.01 to 0.1, the next cycle from 0.1 to 1.0 and the next cycle from 1 to 10, etc. or whatever you choose. On your bacterial growth curve, identify lag, log, and stationary phase. What is the doubling time of the culture in log phase? Biology 422L Laboratory 2 Bacteriological Techniques Objectives: 1) To continue to practice sterile technique until it becomes easy for you to do. 2) To observe the growth of bacteria and see how to test the effect of a substance on bacterial growth. 3) To observe bacteria in the light microscope and learn how to do a Gram stain. 4) To use the technique of streaking plates which you learned in Experiment 1 to separate a mixed culture of bacteria. The ability to do this is often needed in a microbiology laboratory. References: Slonczewski and Foster, Chapter 4
421-lab-Matthysse-Fall-13.docx