Section 56
Chapter 55,049

Polynucleotide phosphorylase is required for Escherichia coli O157:H7 growth above refrigerated temperature

Hu, J.; McCormick, R.J.; Means, W.J.; Zhu, M.-J.

Foodborne Pathogens and Disease 11(3): 177-185


ISSN/ISBN: 1556-7125
PMID: 24328500
DOI: 10.1089/fpd.2013.1632
Accession: 055048665

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The growth of Escherichia coli O157:H7 in contaminated dairy and other refrigerated food products due to temperature fluctuation poses a major food safety threat. Effective control or inhibition of E. coli O157:H7 growth depends on our understanding of mechanisms that regulate its growth at low temperature. We hypothesized that polynucleotide phosphorylase (PNPase) plays a critical role in E. coli O157:H7 low-temperature growth. To test this hypothesis, the pnp deletion mutant of E. coli O157:H7 was generated using the λ Red recombinase system, and the growth and survival of wild-type and pnp deletion mutant strains were compared at low temperatures. The growth of pnp deletion mutant strains in Luria Broth (LB) and agar plate at 37°C was similar to their corresponding wild-type strains, while the deletion of pnp impaired E. coli O157:H7 growth in LB at 10°C and 22°C; growth impairment could be partially recovered in the mutant strains by ectopic expression of the pnp complementation plasmid, demonstrating that growth impairment was PNPase-specific. During 14 days of 10°C storage in both LB and milk, wild type strain EDL933 grew and reached >8 log10 colony-forming units per milliliter after 4 days of 10°C storage, while EDL933Δpnp gradually died off with effects more pronounced in milk, which were again mitigated by pnp overexpression. In addition, pnp deletion impaired the motility of E. coli O157:H7 but did not affect its susceptibility to H2O2. PNPase is required for the growth of E. coli O157:H7 at low temperature; PNPase thus provides a molecular target to control the growth of E. coli O157:H7, which may have important practical applications in dairy and other food industry.

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