Arsenic-Resistant Plant Growth Promoting Pseudoxanthomonas mexicana S254 and Stenotrophomonas maltophilia S255 Isolated from Agriculture Soil Contaminated by Industrial Effluent

In many areas of developing countries, agriculture soil is irrigated with water from drains contaminated with industrial wastewater that contains many toxic substances including arsenic. Such sites could be explored for arsenic-resistant plant growth-promoting microbes. Ten arsenic-resistant bacteria were isolated from such a site and were characterized. Their ability to resist and reduce/oxidize arsenic was determined. The bacteria were also analyzed for plant growth-promoting abilities such as auxin and hydrogen cyanide production, phosphate solubilization, and nitrogen fixation. The effect of these bacteria on plant growth was determined using Vigna radiata both in presence and absence of arsenic. Bacterial isolates S254 and S255 showed maximum resistance against arsenic; up to 225 mM of As(V) and 25 mM of As(III). The phylogenetic analysis revealed that strain S254 belonged to the species Pseudoxanthomonas mexicana and strain S255 belonged to the species Stenotrophomonas maltophilia . Both P. mexicana S254 and S. maltophilia S255 showed positive results for hydrogen cyanide production, auxin production, and nitrogen fixation. P. mexicana S254 produced auxin at a concentration of 14.15 µg mL −1 and S. maltophilia S255 produced auxin as high as 68.75 µg mL −1 . Both the bacteria-enhanced the growth of V. radiata and a statistically significant increase in shoot and root lengths was observed both in the presence and absence of arsenic. The application of such bacteria could be helpful for the growth of plants in arsenic-contaminated lands.