ICEpMERPH, arsenate resistance, ICE genomics, comparative bioinformatics, SXT/R391 elements, mobile genetic elements, Integrative Conjugative Elements
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.