A Novel Arsenate-Resistant Determinant Associated with ICEpMERPH, a Member of the SXT/R391 Group of Mobile Genetic Elements

Abstract

ICEpMERPH, the first integrative conjugative element (ICE) of the SXT/R391 family isolated in the United Kingdom and Europe, was analyzed to determine the nature of its adaptive functions, its genetic structure, and its homology to related elements normally found in pathogenic Vibrio or Proteus species. Whole genome sequencing of Escherichia coli (E. coli) isolate K802 (which contains the ICEpMERPH) was carried out using Illumina sequencing technology. ICEpMERPH has a size of 110 Kb and 112 putative open reading frames (ORFs). The “hotspot regions” of the element were found to contain putative restriction digestion systems, insertion sequences, and heavy metal resistance genes that encoded resistance to mercury, as previously reported, but also surprisingly to arsenate. A novel arsenate resistance system was identified in hotspot 4 of the element, unrelated to other SXT/R391 elements. This arsenate resistance system was potentially linked to two genes: orf69, encoding an organoarsenical efflux major facilitator superfamily (MFS) transporter-like protein related to ArsJ, and orf70, encoding nicotinamide adenine dinucleotide (NAD)-dependent glyceraldehyde-3-phosphate dehydrogenase. Phenotypic analysis using isogenic strains of Escherichia coli strain AB1157 with and without the ICEpMERPH revealed resistance to low levels of arsenate in the range of 1–5 mM. This novel, low-level resistance may have an important adaptive function in polluted environments, which often contain low levels of arsenate contamination. A bioinformatic analysis on the novel determinant and the phylogeny of ICEpMERPH was presented.

Temporal shifts in antibiotic resistance elements govern phage-pathogen conflicts

“…ICEs of the SXT/R391 family appeared in sequenced epidemic V. cholerae in 1987 (35) and are now appreciated as a prominent genomic feature of seventh-pandemic strains (49,50). Although SXT ICEs are infamous for conferring multidrug resistance (23,24,36), diverse SXT ICE cargo genes can confer a broad suite of adaptive traits to their bacterial hosts (24,(51)(52)(53)(54). Our results show that SXT ICEs invariably encode phage resistance genes, linking together antibiotic and phage resistances on a single mobile genetic element widespread in g-proteobacteria.…”

Genomic Analysis of SXT/R391 Integrative Conjugative Elements From Proteus mirabilis Isolated in Brazil

“…We hereafter refer to the P. stuartii element as ICEPst33672 (Table 1). It contains a heavy metal resistance cassette in variable region IV (Figure 1) similar as those found in R391 and pMERPH (Böltner et al, 2002;Ryan et al, 2019), and encodes a small protein containing a metallo-beta-lactamase fold in hotspot 4, but does not carry known antimicrobial resistance determinants. Interestingly, a nonsense mutation is present in traG in the Brazilian isolate (data not shown), probably impairing the conjugation function of this element, given its importance to the mating-pair stabilization (Firth and Skurray, 1992).…”