Viability of Escherichia coli ATCC 8739 in Nutrient Broth, Luria-Bertani Broth and Brain Heart Infusion over 11 Weeks

BACKGROUND Escherichia coli is a widely studied prokaryotic system. A recent study had demonstrated that reduced growth of E. coli after extended culture in Luria-Bertani broth is a result of depletion of fermentable sugars but able to sustain extended cell culture due to the presence of amino acids, which can be utilized as a carbon source. However, this had not been demonstrated in other media. The study aimed to determine the growth and viability of E. coli ATCC 8739 in 3 different media, Nutrient Broth (NB), Brain Heart Infusion (BHI) and Luria-Bertani Broth (LB) over 11 weeks. METHODS Growth of E. coli ATCC 8739 was determined by optical density. Viability was determined by serial dilution/spread-plate enumeration. After 11 weeks, the media were exhausted by repeated culture. Glucose was added to the exhausted media to determine whether glucose is the growth-limiting factor. RESULTS Our results showed that cell density in all 3 media increased to about 1 × 10(9) cells/ml by the end of week 1, from the inoculation density of 2.67 × 10(5) cells/ml, peaked at about 1 × 10(13) cells/ml at week 4, before declining to about 5 × 10(7) cells/ml at week 7. Cell density is highly correlated to genomic DNA content (r(2) = 0.93) but poorly correlated to optical density (r(2)< 0.2). Our results also showed that the spent media were able to support further growth after glucose-supplementation. CONCLUSION NB, LB and BHI are able to support extended periods of culture and glucose depletion is the likely reason for declining cell growth.