Transcriptomic Analysis of Shiga Toxin-Producing Escherichia coli FORC_035 Reveals the Essential Role of Iron Acquisition for Survival in Canola Sprouts and Water Dropwort.

Hongjun Na,Dajeong Kim,Yeonkyung Kim,Hyunjin Yoon,Sangryeol Ryu

doi:10.3389/fmicb.2018.02397

Hongjun Na, Dajeong Kim + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2018.02397

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Abstract

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that poses a serious threat to humans. Although EHEC is problematic mainly in food products containing meat, recent studies have revealed that many EHEC-associated foodborne outbreaks were attributable to spoiled produce such as sprouts and green leafy vegetables. To understand how EHEC adapts to the environment in fresh produce, we exposed the EHEC isolate FORC_035 to canola spouts (Brassica napus) and water dropwort (Oenanthe javanica) and profiled the transcriptome of this pathogen at 1 and 3 h after incubation with the plant materials. Transcriptome analysis revealed that the expression of genes associated with iron uptake were down-regulated during adaptation to plant tissues. A mutant strain lacking entB, presumably defective in enterobactin biosynthesis, had growth defects in co-culture with water dropwort, and the defective phenotype was complemented by the addition of ferric ion. Furthermore, gallium treatment to block iron uptake inhibited bacterial growth on water dropwort and also hampered biofilm formation. Taken together, these results indicate that iron uptake is essential for the fitness of EHEC in plants and that gallium can be used to prevent the growth of this pathogen in fresh produce.

Highlights

Enterohemorrhagic Escherichia coli (EHEC) is a virulent foodborne pathogen that causes outbreaks associated with serious health problems worldwide (Sperandio and Nguyen, 2012)
Bacterial transcriptome analysis is an effective approach to understand the interactions between foodborne pathogens and plants (Kyle et al, 2010; Fink et al, 2012; Landstorfer et al, 2014)
Bacterial growth was increased in the presence of plant tissues (Figure 1), which was consistent with a previous study showing that bacteria could take advantage of plantsderived nutrients for their growth (Cooley et al, 2003; Jablasone et al, 2005; Schikora et al, 2008; Deering et al, 2012)

Summary

Introduction

Enterohemorrhagic Escherichia coli (EHEC) is a virulent foodborne pathogen that causes outbreaks associated with serious health problems worldwide (Sperandio and Nguyen, 2012). Log2 [fold change] values were used to determine relative gene expression between FORC_035 only and FORC_035 co-cultured with canola sprouts and water dropwort. To understand the bacterial response and adaptations in contact with plants, FORC_035 cells were harvested at 1 and 3 h post-inoculation and their RNAs were isolated for RNA-Seq analysis.

Results

Conclusion