Characterisation of Campylobacter jejuni genes potentially involved in phosphonate degradation

Abstract

Potential biological roles of the Campylobacter jejuni genes cj0641, cj0774c and cj1663 were investigated. The proteins encoded by these genes showed sequence similarities to the phosphonate utilisation PhnH, K and L gene products of Escherichia coli. The genes cj0641, cj0774c and cj1663 were amplified from the pathogenic C. jejuni strain 81116, sequenced, and cloned into pGEM-T Easy vectors. Recombinant plasmids were used to disrupt each one of the genes by inserting a kanamycin resistance (KmR) cassette employing site-directed mutagenesis or inverse PCR. Campylobacter jejuni 81116 isogenic mutants were generated by integration of the mutated genes into the genome of the wild-type strain. The C. jejuni mutants grew on primary isolation plates, but they could not be purified by subsequent passages owing to cell death. The mutant C. jejuni strains survived and proliferated in co-cultures with wild-type bacteria or in media in which wild-type C. jejuni had been previously grown. PCR analyses of mixed wild-type/mutant cultures served to verify the presence of the mutated gene in the genome of a fraction of the total bacterial population. The data suggested that each mutation inactivated a gene essential for survival. Rates of phosphonate catabolism in lysates of E. coli strain DH5α were determined using proton nuclear magnetic resonance spectroscopy. Whole-cell lysates of the wild-type degraded phosphonoacetate, phenylphosphonate and aminomethylphosphonate. Significant differences in the rates of phosphonate degradation were observed between lysates of wild-type E. coli, and of bacteria transformed with each one of the vectors carrying one of the C. jejuni genes, suggesting that these genes were involved in phosphonate catabolism.

Contribution of TAT System Translocated PhoX to Campylobacter jejuni Phosphate Metabolism and Resilience to Environmental Stresses

“…Difference in poly P accumulation between ppk1 and phoX mutants is likely due to ability of the phoX mutant to ameliorate the poly P defect with Pi obtained by other sources such as through phosphonate catabolism. C. jejuni has been shown to catabolize phosphonate [47] , [48] . However, ppk1 mutant can not synthesize poly P even in the presence of other Pi sources including phosphonates.…”

Aminophosphonate mineralisation is a major step in the global oceanic phosphorus redox cycle

“…Both phosphonate biosynthesis 1,3,5,46 and catabolic 1,23,25,43,[47][48][49][50][51][52] genes are ubiquitous in marine, soil and gut microbiomes, suggesting phosphonate cycling is widespread in nature. In contrast, the uptake of these molecules is comparatively understudied, with only two characterised ABC transport systems confirmed, both of which are linked solely to Pacquisition [29][30][31] .…”