Determination of the Growth Rate of Enterobacter sp. SM3
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.