Conjugal Transfer of Polychlorinated Biphenyl/Biphenyl Degradation Genes in Acidovorax sp. Strain KKS102, Which Are Located on an Integrative and Conjugative Element

Abstract

A polychlorinated biphenyl (PCB)/biphenyl degradation gene cluster in Acidovorax sp. strain KKS102, which is very similar to that in Tn4371 from Cupriavidus oxalaticus A5, was transferred to several proteobacterial strains by conjugation. The mobilized DNA fragment consisted of 61,807 bp and carried genes for mating-pair formation (mpf), DNA transfer (dtr), integrase (int), and replication-partition proteins (rep-parAB). In the transconjugants, transferred DNA was integrated at ATTGCATCAG or similar sequences. The circular-form integrative and conjugative element (ICE) was detected by PCR, and quantitative PCR analyses revealed that, in KKS102 cells, the ratio of the circular form to the integrated form was very low (approximately 10 ؊5 ). The circular form was not detected in a mutant of the int gene, which was located at the extreme left and transcribed in the inward direction, and the level of int transcriptional activity was much higher in the circular form than in the integrated form. These findings clearly demonstrated that the genes for PCB/biphenyl degradation in KKS102 cells are located on an ICE, which was named ICE KKS102 4677. Comparisons of similar ICE-like elements collected from the public database suggested that those of beta-and gammaproteobacteria were distinguishable from other ICE-like elements, including those in alphaproteobacteria, with respect to the gene composition and gene organization. Bacterial horizontal gene transfer plays an important role in the acquisition of new phenotypic traits and helps host cells adapt to their environments. Mobile genetic elements that carry genes for xenobiotic-compound degradation are of particular interest, because such elements contribute to the spread of genetic information that enables the host cell to degrade man-made chemicals.Among the several classes of mobile genetic elements are integrative and conjugative elements (ICEs) (2, 3, 35) that, by being excised from genomes, form plasmid-like circular structures, transfer to other cells by conjugation, and reintegrate into the genomes of new hosts. The excision of ICEs from the genome involves the activity of integrase, which excises the circular entity from the genome by recombining the DNA tract found at each end of the ICE. The integrase also catalyzes the integration of the circular form into the genome. In the integration process, the integrase mediates recombination between the attP site on the circular-form DNA and the attB site on the genome of the recipient cell.ICEs are known to encode a variety of phenotypic traits, including pathogenicity, resistance to antibiotics, and xenobiotic degradation (35). Examples of ICE-carrying genes for the degradation of xenobiotic compounds are limited to the clc element (105 kb) from Pseudomonas knackmussii B13 (23) and the bph-sal element (90 kb) from Pseudomonas putida KF715 (17); these elements carry degradation genes for 3-chlorobenzoate and polychlorinated biphenyl (PCB)/biphenyl plus salicylate, respectively. Acidovorax sp. strain KKS102, which is a ...

Pan-genome analysis of the emerging foodborne pathogen Cronobacterspp. suggests a species-level bidirectional divergence driven by niche adaptation

“…muytjensii ATCC 51329 harbor a 57 kb integrative conjugative element (ICE), which is 99% identical between strains (Table  4). This mobile genetic element is most closely related to the ICE-KKS family of integrating and conjugative elements, found in β- and γ- proteobacteria and represented by ICE KKS102 4677 , which carries polychlorinated biphenyl degradation genes [30]. For the Cronobacter ICE, in addition to the conjugal transfer, integrase, and replication/partition genes, there is a 21 kb internal segment which carries unique genes among this class of ICEs.…”

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element

“…The FseA protein is encoded on a widespread family of proteobacterial ICEs with transfer systems related to those of ICEMlSym R7A and Tn4371 (9,10,12,36,37). The Msi171 portion of FseA is a member of the "domain of unknown function" DUF2285 superfamily (COG5419, pfam10074), with 291 annotated members as of December 2014 (38).…”

Evidence and characteristics of a diverse and metabolically active microbial community in deep subsurface clay borehole water

“…The Acidovorax genus is a very common, mostly aerobic, soil bacterium, which was taxonomically dissociated from the Pseudomonas lineage over two decades ago (Willems et al ., ). It is mostly described as a plant pathogen, a degrader of xenobiotics with associated mobile genetic elements and/or a nitrate reducer (Hu & Young, ; Heylen et al ., ; Ohtsubo et al ., ). It occurs as a metabolically versatile genus, particularly coinciding with the high nitrate‐reducing potential observed by MPN.…”