Expression of Genes Located on the Incompatibility Group FIB Plasmids at Transcription and Protein Levels in Iron-Modified Growth Conditions.

Carter N Abbott,Monique Felix,Steven L Foley,Bijay K Khajanchi

doi:10.3389/fmicb.2021.729275

Abstract

Salmonella enterica strains often harbor plasmids representing several incompatibility groups (Inc) including IncFIB, which have been previously associated with carrying antimicrobial resistance and virulence associated genes. To better understand the distribution of virulence genes on IncFIB plasmids, we analyzed 37 complete whole genome and plasmid sequences of different S. enterica isolates from multiple serovars. Many of the sequences analyzed carried multiple virulence-associated genes, including those associated with iron acquisition systems; thus we aimed to determine how iron-rich (IR) and various iron-depleted (ID) conditions affected the transcription of iron acquisition and virulence genes including sitA, iutA, iucA, and enolase at different time intervals. sitA, iutA, and enolase from S. enterica that were grown in Luria-Bertani broth (LB) ID (LBID) conditions were substantially upregulated when compared to LBIR conditions. For both S. enterica strains that were grown at various LBID conditions, addition of 200 μM bipyridyl in the growth medium yielded the highest transcription for all four genes, followed by the 100 μM concentration. An antibody using a peptide targeting aerobactin receptor gene iutA encoded by IncFIB was generated and used to examine the protein expression in the wild-type, recipient, and transconjugant strain in LB, LBID, and LBIR growth conditions using Western blot analyses. A 70 KDa protein band was detected in the wild-type and transconjugant that carried the IncFIB plasmid, while this band was not detected in the recipient strain that lacked this plasmid.

Highlights

Salmonella enterica is one of the major foodborne pathogens in the United States (Scallan et al, 2011)
In silico Analyses of Virulence Genes Located on the IncFIB Plasmids
The number of studies that have examined the virulenceassociated characteristics related to IncFIB plasmids in Salmonella enterica is quite limited, with much of the focus on the Spv locus that contributes to virulence in a subset of serotypes (Gulig et al, 1993; Rotger and Casadesus, 1999)

Summary

Introduction

Salmonella enterica is one of the major foodborne pathogens in the United States (Scallan et al, 2011). It is estimated that Salmonella is responsible for 1.2 million illnesses per year, resulting in approximately 23,000 hospitalizations and 450 deaths in the United States (Scallan et al, 2011). Addition to the chromosomally-encoded virulence factors, many strains of Salmonella possess virulence associated plasmids that encode several virulence factors (Khajanchi et al, 2017). These plasmidassociated virulence factors include iron acquisition systems that are frequently located on the incompatibility group (Inc) FIB plasmids (Khajanchi et al, 2017)

Objectives

Methods

Results