Rapid growth rate of Enterobacter sp. SM3 determined using several methods

Area of Science:

• Microbiology
• Bacterial Physiology

Background:

• Bacterial growth rate is crucial but often inconsistently measured using optical density or colony counts.
• Existing literature shows wide variations in growth rates for common bacterial species.
• Reliable determination of bacterial doubling time requires careful methodology and validation.

Purpose of the Study:

• To reliably determine the growth rate of Enterobacter sp. SM3.
• To compare the growth rate of Enterobacter sp. SM3 with a wildtype E. coli strain.
• To validate and compare different methods for measuring bacterial growth rate.

Main Methods:

• Extended conventional optical density (OD) measurements for Enterobacter sp. SM3 growth rate determination.
• Compared OD data fitting, relative density method, and OD curve shifts for reliability.
• Validated OD measurements with colony-forming unit (CFU) counts over time.

Main Results:

• Three OD-based methods yielded consistent growth rate results for Enterobacter sp. SM3 with proper parameter selection.
• Colony-forming unit (CFU) measurements confirmed the OD-based growth rate findings.
• Enterobacter sp. SM3 exhibited a faster division rate (21 ± 3 min) than E. coli KP437 (29 ± 2 min) at 37°C in lysogeny broth.

Conclusions:

• Optical density (OD) and colony-forming unit (CFU) methods can provide consistent bacterial growth rate values.
• Employing and comparing multiple measurement techniques is essential for reproducible and reliable bacterial growth rate data.
• Cross-validation of methods prevents reporting variable doubling times for bacterial strains.