The primary role of the stationary phase in bacterial growth is:
Upon entry into stationary phase nutrient exhaustion does not equate to dormancy but triggers extensive differentiation for long term survival. Genome wide expression reprogrammed by ppGpp alarmone binding RNA polymerase, sigma factor switch from RpoD to RpoS general stress sigma encoded by rpoS. RpoS regulon includes oxidative protection catalase HPII, exonuclease, DNA protection Dps compacting chromosome sequestering iron preventing Fenton chemistry, acid resistance Gad system glutamate decarboxylase, trehalose synthesis. Secondary metabolism activated nonribosomal peptide synthetases, polyk
Ref: Prescott's Microbiology, 11th ed., Chapter 7: Stationary phase role - Sporulation and secondary metabolites.