SELECTION OF PURPLE NON-SULFUR BACTERIA RESISTANT TO SALINITY AND ARSENIC

Abstract

Arsenic (As) contamination and saltwater intrusion are emerging as significant environmental and public health concerns in certain regions of the Mekong delta. This study aimed to evaluate the potential of purple non-sulfur photosynthetic bacteria (PNSB) strains for their ability to tolerate and grow under saline and arsenic-contaminated conditions, with the prospect of applying these strains in mitigating the adverse effects of salinity and arsenic pollution. A series of experiments were conducted to assess the growth performance of various PNSB strains under the following stress conditions: (1) salinity stress with 1% Na⁺, (2) exposure to arsenite (As³⁺) at a concentration of 110 ppm, (3) exposure to arsenate (As⁵⁺) at a concentration of 200 ppm and (4) evaluation of exopolysaccharide (EPS) production and biomass accumulation. Under saline conditions (1% Na⁺), several strains exhibited robust growth, including S29, W10, W14, W15, W22, W25, W29, W31, W4.3, W44, W47, with biomass concentrations ranging from 0.94 to 1.53 mg/L. In the presence of As³⁺ (110 ppm), strains W14, W15, W25, W31, W4, W4.3, W47 demonstrated significant growth, with biomass concentrations ranging from 2.36 to 2.74 mg/L. However, PNSB strains generally exhibited limited growth in the presence of As⁵⁺ (200 ppm). EPS production among the tested PNSB strains ranged from 0.95 to 3.08 mg/L. These findings suggest that specific PNSB strains possess promising capabilities for application in strategies aimed at reducing arsenic contamination and the effects of salinity.