LAUSR

We studied the viable but nonculturable (VBNC) state of the human pathogen Escherichia coli O157:H7 during desiccation using genomic, proteomic, and direct methods in a model soil under controlled conditions. During desiccation, the bacterial cells reduced their culturability, protein synthesis, and DNA replication, and changed their morphology. Four days after rewetting of dry soil, the culturability of E. coli recovered, and protein synthesis was restored. A total of 2,324 proteins were differently expressed in the VBNC state compared to the culturable state and identified. Morphological changes during the VBNC state paralleled the downregulation of cytoskeletal proteins and enzymes of the tricarboxylic acid cycle. On the contrary, proteins involved in nutrient transport, membrane, chemotactic, flagellar, virulence, and adhesion were upregulated. Overall, our results indicated that low soil moisture can induce the VBNC state in E. coli O157:H7 but this state can revert to culturability and full metabolic activity upon soil rewetting. These findings can be important aspects in assessing the environmental risks posed by microbial pathogens in soil.