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Determination of the Growth Rate of Enterobacter sp. SM3
  • Sophie Pollack-Milgate,
  • Sanchi Saitia,
  • JAY TANG
Sophie Pollack-Milgate
Brown University
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Sanchi Saitia
Brown University
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JAY TANG
Brown University

Corresponding Author:[email protected]

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Abstract

We extend conventional optical density (OD) measurements to determine the growth rate of a recently identified species of Enterobacteriaceae, Enterobacter sp. SM3. To assess the reliability of this method, we compare growth rates obtained from fitting OD data to exponential growth, applying a relative density technique, and by measuring shifts in OD curves following set factors of dilution. These three techniques yield consistent results. Thus, they confirm that the most common method based on OD measurements can determine the bacterial doubling time. The main source of error is due to the reliance on a short span of an exponential growth phase. In lysogeny broth at 37oC, we found SM3 to divide every 22±3 minutes, notably faster than the RP437 strain of E. coli, which divides every 29±2 minutes. We also measured the SM3 division rate by counting colony-forming units (CFU) versus time, yielding results consistent with the OD measurements. These methods are applicable to determining the growth rate of any bacterial species.