The putative phosphate transporter PitB (PP1373) is involved in tellurite uptake in Pseudomonas putida KT2440

Abstract

Tellurium oxyanions are chemical species with great toxicity; their presence in the environment has increased because of mining industries and photovoltaic and electronic waste. Recovery strategies based on microorganisms for this metalloid are of interest, but further studies of the transport systems and enzymes responsible for implementing tellurium transformations are required because many mechanisms remain unknown. Here, we investigated the involvement in tellurite uptake of the putative phosphate transporter PitB (PP1373) in soil bacterium Pseudomonas putida KT2440. For this purpose, through a method based on the CRISPR/Cas9 system, we generated a strain deficient in pitB gene and characterized its phenotype on exposing it to varied concentrations of tellurite. Growth curves and Transmission Electronic Microscopy experiments of wild type and {Delta}pitB showed that both strains were able to internalize tellurite into the cytoplasm and reduce the oxyanion to black nano-sized and rod-shaped tellurium particles, however, {Delta}pitB strain showed an increased resistance to the tellurite toxic effects. At a concentration of 100 uM tellurite, where the biomass formation of wild type strain decreased by half, we observed a greater ability of {Delta}pitB to reduce this oxyanion with respect to wild type strain (~38% vs ~16%), which is related by the greater biomass production of {Delta}pitB and not by a greater consumption of tellurite per cell. The phenotype of the mutant was restored on over-expressing pitB in trans. In summary, our results indicate that PitB is one of several transporters responsible for tellurite uptake in P. putida KT2440.