Demonstration of sequential adaptation strategy for developing salt tolerance in bacteria for wastewater treatment: A study using Escherichia coli as model

A wastewater isolate identified as Escherichia coli HPC781 was adapted for high salt concentration through sequential transfers in Luria Broth (LB). The cells were grown in LB with 5% sodium chloride (NaCl) and were analyzed for the acquired salt resistance network through gene expression profiles. Microarray studies revealed TCA, glyoxylate shunt and acetyl Co-A metabolism as key nodes for stress combat to arrive at compromised physiology. It also proposed that the cells were receiving signals from salt environment via OmpR–EnvZ two component systems and stress dependent general regulatory protein rpoH and rpoE. The salt adapted culture, when challenged with wastewater having additional 5% salt showed growth. The work represents a tactic to adjust biochemical network towards stress and reveals its applicability via real-time PCR measurement of genes in wastewater. The study proposes that the recycled biomass with an adaptation strategy could be applied for treatment of wastewater with high salt levels.