Arsenic-Redox Transformation and Plant Growth Promotion by Purple Nonsulfur Bacteria Rhodopseudomonas palustris CS2 and Rhodopseudomonas faecalis SS5

Abstract

Arsenic (As) is a well-known toxic metalloid found naturally and released by different industries, especially in developing countries. Purple nonsulfur bacteria (PNSB) are known for wastewater treatment and plant growth promoting abilities. As-resistant PNSB were isolated from a fish pond. Based on As-resistance and plant growth promoting attributes, 2 isolates CS2 and SS5 were selected and identified as Rhodopseudomonas palustris and Rhodopseudomonas faecalis, respectively, through 16S rRNA gene sequencing. Maximum As(V) resistance shown by R. faecalis SS5 and R. palustris CS2 was up to 150 and 100 mM, respectively. R. palustris CS2 showed highest As(V) reduction up to 62.9% (6.29 ± 0.24 mM), while R. faecalis SS5 showed maximum As(III) oxidation up to 96% (4.8 ± 0.32 mM), respectively. Highest auxin production was observed by R. palustris CS2 and R. faecalis SS, up to 77.18 ± 3.7 and 76.67 ± 2.8 μg mL−1, respectively. Effects of these PNSB were tested on the growth of Vigna mungo plants. A statistically significant increase in growth was observed in plants inoculated with isolates compared to uninoculated plants, both in presence and in absence of As. R. palustris CS2 treated plants showed 17% (28.1 ± 0.87 cm) increase in shoot length and 21.7% (7.07 ± 0.42 cm) increase in root length, whereas R. faecalis SS5 treated plants showed 12.8% (27.09 ± 0.81 cm) increase in shoot length and 18.8% (6.9 ± 0.34 cm) increase in root length as compared to the control plants. In presence of As, R. palustris CS2 increased shoot length up to 26.3% (21.0 ± 1.1 cm), while root length increased up to 31.3% (5.3 ± 0.4 cm), whereas R. faecalis SS5 inoculated plants showed 25% (20.7 ± 1.4 cm) increase in shoot length and 33.3% (5.4 ± 0.65 cm) increase in root length as compared to the control plants. Bacteria with such diverse abilities could be ideal for plant growth promotion in As-contaminated sites.

Whole-genome sequencing and comparative analysis of two plant-associated strains of Rhodopseudomonas palustris (PS3 and YSC3)

“…S5 ), even though these strains possess most of the phosphate solubilization-related genes. This result is also consistent with previous reports that R. palustris lacks the ability to solubilize phosphate 55 , 56 . The commonly observed absence of phosphate-solubilization activity among R. palustris strains indicates that this function is probably no longer required for sustaining the growth of these bacteria in the environment.…”

Anoxic growth optimization for metal respiration and photobiological hydrogen production by arsenic‐resistant Rhodopseudomonas and Rhodobacter species

“…As‐resistance is reported to be bestowed due to the presence of the ars operon . Many PNSB bacteria have been reported to resist and reduce/detoxify As . Rhodobacter sp.…”

Arsenic-resistant and plant growth-promotingFirmicutesand γ-Proteobacteriaspecies from industrially polluted irrigation water and corresponding cropland

“…This gives twofold advantage to the plants growing in As-contaminated soil. Many scientists have reported plant growth promotion by bacteria in the presence of metals (Batool et al 2017), however, reports of As-resistant bacteria isolated from croplands and their effects on plant growth enhancement in the presence of As are rare. Table S2 highlights some of the studies reporting As/metals resistance and plant growth promotion by strains of the same bacterial species as reported in this study.…”