Effects of potassium-solubulizing and photosynthetic bacteria on tolerance to salt stress in maize.

AIMS: The purpose of this study was to determine the positive effects of potassium-solubilizing bacteria and photosynthetic bacteria on the salt tolerance of maize. METHODS AND RESULTS: We selected the maize inbred lines USTB-265 (salt-sensitive), USTB-109 (moderately salt-tolerant) and USTB-297 (salt-tolerant) to investigate their growth characteristics, enzyme activity and gene expression in response to inoculation with photosynthetic bacteria and potassium-solubilizing bacteria under salt-stress conditions. CONCLUSIONS: Photosynthetic bacteria and potassium-solubilizing bacteria inoculation significantly enhanced the expression of antioxidant enzyme-related genes and increased the activities of the antioxidant enzymes superoxide dismutase, catalase and ascorbate peroxidase. In addition, inoculation with photosynthetic bacteria more efficiently improved maize salt tolerance than inoculation with potassium-solubilizing bacteria. While the effects of these bacteria differed among the three maize lines, both photosynthetic bacteria and potassium-solubilizing bacteria can enhance salt tolerance in maize. SIGNIFICANCE AND IMPACT OF THE STUDY: Soil salinization is one of the most critical factors affecting maize growth. These two types of bacteria (e.g. Bacillus mojavensis JK07 and Rhodopseudomonas palustris) have proven useful in salinized agricultural lands as bio-inoculants to increase crop productivity.

Proteome Response of a Metabolically Flexible Anoxygenic Phototroph to Fe(II) Oxidation.

The oxidation of Fe(II) by anoxygenic photosynthetic bacteria was likely a key contributor to Earth's biosphere prior to the evolution of oxygenic photosynthesis and is still found in a diverse range of modern environments. All known phototrophic Fe(II) oxidizers can utilize a wide range of substrates, thus making them very metabolically flexible. However, the underlying adaptations required to oxidize Fe(II), a potential stressor, are not completely understood. We used a combination of quantitative proteomics and cryogenic transmission electron microscopy (cryo-TEM) to compare cells of Rhodopseudomonas palustris TIE-1 grown photoautotrophically with Fe(II) or H2 and photoheterotrophically with acetate. We observed unique proteome profiles for each condition, with differences primarily driven by carbon source. However, these differences were not related to carbon fixation but to growth and light harvesting processes, such as pigment synthesis. Cryo-TEM showed stunted development of photosynthetic membranes in photoautotrophic cultures. Growth on Fe(II) was characterized by a response typical of iron homeostasis, which included an increased abundance of proteins required for metal efflux (particularly copper) and decreased abundance of iron import proteins, including siderophore receptors, with no evidence of further stressors, such as oxidative damage. This study suggests that the main challenge facing anoxygenic phototrophic Fe(II) oxidizers comes from growth limitations imposed by autotrophy, and, once this challenge is overcome, iron stress can be mitigated using iron management mechanisms common to diverse bacteria (e.g., by control of iron influx and efflux).IMPORTANCE The cycling of iron between redox states leads to the precipitation and dissolution of minerals, which can in turn impact other major biogeochemical cycles, such as those of carbon, nitrogen, phosphorus and sulfur. Anoxygenic phototrophs are one of the few drivers of Fe(II) oxidation in anoxic environments and are thought to contribute significantly to iron cycling in both modern and ancient environments. These organisms thrive at high Fe(II) concentrations, yet the adaptations required to tolerate the stresses associated with this are unclear. Despite the general consensus that high Fe(II) concentrations pose numerous stresses on these organisms, our study of the large-scale proteome response of a model anoxygenic phototroph to Fe(II) oxidation demonstrates that common iron homeostasis strategies are adequate to manage this. The bulk of the proteome response is not driven by adaptations to Fe(II) stress but to adaptations required to utilize an inorganic carbon source. Such a global overview of the adaptation of these organisms to Fe(II) oxidation provides valuable insights into the physiology of these biogeochemically important organisms and suggests that Fe(II) oxidation may not pose as many challenges to anoxygenic phototrophs as previously thought.

Adaptation mechanism and tolerance of Rhodopseudomonas palustris PSB-S under pyrazosulfuron-ethyl stress.

BACKGROUND: Pyrazosulfuron-ethyl is a long lasting herbicide in the agro-ecosystem and its residue is toxic to crops and other non-target organisms. A better understanding of molecular basis in pyrazosulfuron-ethyl tolerant organisms will shed light on the adaptive mechanisms to this herbicide. RESULTS: Pyrazosulfuron-ethyl inhibited biomass production in Rhodopseudomonas palustris PSB-S, altered cell morphology, suppressed flagella formation, and reduced pigment biosynthesis through significant suppression of carotenoids biosynthesis. A total of 1127 protein spots were detected in the two-dimensional gel electrophoresis. Among them, 72 spots representing 56 different proteins were found to be differently expressed using MALDI-TOF/TOF-MS, including 26 up- and 30 down-regulated proteins in the pyrazosulfuron-ethyl-treated PSB-S cells. The up-regulated proteins were involved predominantly in oxidative stress or energy generation pathways, while most of the down-regulated proteins were involved in the biomass biosynthesis pathway. The protein expression profiles suggested that the elongation factor G, cell division protein FtsZ, and proteins associated with the ABC transporters were crucial for R. palustris PSB-S tolerance against pyrazosulfuron-ethyl. CONCLUSION: Up-regulated proteins, including elongation factor G, cell division FtsZ, ATP synthase, and superoxide dismutase, and down-regulated proteins, including ALS III and ABC transporters, as well as some unknown proteins might play roles in R. palustris PSB-S adaptation to pyrazosulfuron-ethyl induced stresses. Functional validations of these candidate proteins should help to develope transgenic crops resistant to pyrazosulfuron-ethyl.

Bacteremia caused by the photosynthetic environmental bacterium Rhodopseudomonas.

We report a case of persistent Rhodopseudomonas bacteremia in a patient two months after an allogeneic bone marrow transplant for acute myeloid leukemia. The bacteremia persisted until IV catheter removal. To our knowledge, this is the first report of Rhodopseudomonas causing infection in humans.

Arsenic resistance genes of As-resistant purple nonsulfur bacteria isolated from As-contaminated sites for bioremediation application.

This study aimed to identify arsenic resistant mechanisms in As-resistant purple nonsulfur bacteria (PNSB) by screening them for presence of As-resistance genes and related enzymes. Resistance to As(III) and As(V) of four As-resistant PNSB determined in terms of median inhibition concentration (IC50 values) were in the order of strains Rhodopseudomonas palustris C1 > R. palustris AB3 > Rubrivivax benzoatilyticus C31 > R. palustris L28 which corresponded to the presence of As-resistance genes in these bacteria. The strain C1 showed all As-marker genes; arsC, arsM, aioA, and acr3, while aioA was not detected in strain AB3. Strains C31 and L28 had only Arsenite-transporter gene, acr3. Translation of all these detected gene sequences of strain C1 to amino acid sequences showed that these proteins have vicinal cysteine; Cys126, Cys105, and Cys178 of Acr3, ArsC, AioA, respectively. Tertiary structure of proteins Acr3, ArsC, AioA, and ArsM showed strain C1 exhibits the high activities of arsenite oxidase and arsenate reductase enzymes that are encoded by aioA and arsC genes, respectively. Moreover, strain C1 with arsM gene produced volatile-methylated As-compounds; monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and arsenobetaine (AsB) in the presence of either As(III) or As(V). In conclusion, the strain C1 has great potential for its application in bioremediation of As-contaminated sites.

Bioenergetics of lactate vs. acetate outside TCA enhanced the hydrogen evolution levels in two newly isolated strains of the photosynthetic bacterium Rhodopseudomonas.

Two local hydrogen-evolving strains of purple nonsulfur bacteria have been isolated, characterized, and identified as Rhodopseudomonas sp. TUT (strains Rh1 and Rh2). Lactate followed by succinate and malate supported the highest amounts of H2 production, growth (O.D.660nm, proteins and bacteriochlorphyll contents), nitrogenase activity, and uptake hydrogenase; the least of which was acetate. Alginate-immobilized cells evolved higher hydrogen amounts than free cell counterparts. Rh1 was more productive than Rh2 at all circumstances. Lactate-dependent hydrogen evolution was more than twice that of acetate, due to ATP productivity (2/-1, respectively), which is limiting to the nitrogenase activity. The preference of lactate over other acids indicates the feasibility of using these two strains in hydrogen production from dairy wastewater.

Hydrogen production under salt stress conditions by a freshwater Rhodopseudomonas palustris strain.

Hydrogen represents a possible alternative energy carrier to face the growing request for energy and the shortage of fossil fuels. Photofermentation for the production of H2 constitutes a promising way for integrating the production of energy with waste treatments. Many wastes are characterized by high salinity, and polluted seawater can as well be considered as a substrate. Moreover, the application of seawater for bacterial culturing is considered cost-effective. The aims of this study were to assess the capability of the metabolically versatile freshwater Rhodopseudomonas palustris 42OL of producing hydrogen on salt-containing substrates and to investigate its salt stress response strategy, never described before. R. palustris 42OL was able to produce hydrogen in media containing up to 3 % added salt concentration and to grow in media containing up to 4.5 % salinity without the addition of exogenous osmoprotectants. While the hydrogen production performances in absence of sea salts were higher than in their presence, there was no significant difference in performances between 1 and 2 % of added sea salts. Nitrogenase expression levels indicated that the enzyme was not directly inhibited during salt stress, but a regulation of its expression may have occurred in response to salt concentration increase. During cell growth and hydrogen production in the presence of salts, trehalose was accumulated as a compatible solute; it protected the enzymatic functionality against salt stress, thus allowing hydrogen production. The possibility of producing hydrogen on salt-containing substrates widens the range of wastes that can be efficiently used in production processes.

Effects of metal ions on biomass and 5-aminolevulinic acid production in Rhodopseudomonas palustris wastewater treatment.

This work investigated the effects of eight metal ions on Rhodopseudomonas palustris growth and 5-aminolevulinic acid (ALA) yield in wastewater treatment. Results show that metal ions (Mg(2+) of 15 mmol/L, Fe(2+) of 400 µmol/L, Co(2+) of 4 µmol/L, Ni(2+) of 8 µmol/L and Zn(2+) of 4 µmol/L) could effectively improve the chemical oxygen demand (COD) removal, Rp. palustris biomass and ALA yield. The highest ALA yield of 13.1 mg/g-biomass was achieved with Fe(2+) of 400 µmol/L. ALA yields were differentially increased under different metal ions in the following order: Fe(2+) group > Mg(2+) group > Co(2+) group = Ni(2+) group > Zn(2+) group = Mo(2+) group > control. Cu(2+) and Mn(2+) inhibited Rp. palustris growth and ALA production. Mechanism analysis revealed that metal ions changed ALA yields by influencing the activities of ALA synthetase and ALA dehydratase.

Metabolism of Multiple Aromatic Compounds in Corn Stover Hydrolysate by Rhodopseudomonas palustris.

Lignocellulosic biomass hydrolysates hold great potential as a feedstock for microbial biofuel production, due to their high concentration of fermentable sugars. Present at lower concentrations are a suite of aromatic compounds that can inhibit fermentation by biofuel-producing microbes. We have developed a microbial-mediated strategy for removing these aromatic compounds, using the purple nonsulfur bacterium Rhodopseudomonas palustris. When grown photoheterotrophically in an anaerobic environment, R. palustris removes most of the aromatics from ammonia fiber expansion (AFEX) treated corn stover hydrolysate (ACSH), while leaving the sugars mostly intact. We show that R. palustris can metabolize a host of aromatic substrates in ACSH that have either been previously described as unable to support growth, such as methoxylated aromatics, and those that have not yet been tested, such as aromatic amides. Removing the aromatics from ACSH with R. palustris, allowed growth of a second microbe that could not grow in the untreated ACSH. By using defined mutants, we show that most of these aromatic compounds are metabolized by the benzoyl-CoA pathway. We also show that loss of enzymes in the benzoyl-CoA pathway prevents total degradation of the aromatics in the hydrolysate, and instead allows for biological transformation of this suite of aromatics into selected aromatic compounds potentially recoverable as an additional bioproduct.

Nano-TiO2 enhanced photofermentative hydrogen produced from the dark fermentation liquid of waste activated sludge.

After anaerobic dark fermentation of waste activated sludge (WAS) for hydrogen production, there are a large number of organic compounds including protein, polysaccharide, and volatile fatty acids left in the dark fermentation liquid, which can be further bioconverted to hydrogen by photofermentation techniquea. In this study, the enhancement of photofermentative hydrogen produced from WAS dark fermentation liquid by using nano-TiO2 is reported. First, high concentration of NH(4)(+)-N in the dark fermentation liquid was observed to inhibit the photofermentative hydrogen production, and its removal was essential. Then the effect of nano-TiO2 on photofermentative hydrogen generation was investigated, and the addition of 100 mg/L nano-TiO2 increased hydrogen by 46.1%. Finally, the mechanisms for nano-TiO2 improving hydrogen production were investigated. It was found that nano-TiO2 improved the decomposition of protein and polysaccharide to small-molecule organic compounds and promoted the growth of photosynthetic bacteria and the activity of nitrogenase but decreased the H2-uptake hydrogenase activity.

Differential accumulation of form I RubisCO in Rhodopseudomonas palustris CGA010 under Photoheterotrophic growth conditions with reduced carbon sources.

Rhodopseudomonas palustris is unique among characterized nonsulfur purple bacteria because of its capacity for anaerobic photoheterotrophic growth using aromatic acids. Like growth with other reduced electron donors, this growth typically requires the presence of bicarbonate/CO(2) or some other added electron acceptor in the growth medium. Proteomic studies indicated that there was specific accumulation of form I ribulose 1, 5-bisphosphate carboxylase/oxygenase (RubisCO) subunit proteins (CbbL and CbbS), as well as the CbbX protein, in cells grown on benzoate without added bicarbonate; such cells used the small amounts of dissolved CO(2) in the medium to support growth. These proteins were not observed in extracts from cells grown in the presence of high levels (10 mM) of added bicarbonate. To confirm the results of the proteomics studies, it was shown that the total RubisCO activity levels were significantly higher (five- to sevenfold higher) in wild-type (CGA010) cells grown on benzoate with a low level (0.5 mM) of added bicarbonate. Immunoblots indicated that the increase in RubisCO activity levels was due to a specific increase in the amount of form I RubisCO (CbbLS) and not in the amount of form II RubisCO (CbbM), which was constitutively expressed. Deletion of the main transcriptional regulator gene, cbbR, resulted in impaired growth on benzoate-containing low-bicarbonate media, and it was established that form I RubisCO synthesis was absolutely and specifically dependent on CbbR. To understand the regulatory role of the CbbRRS two-component system, strains with nonpolar deletions of the cbbRRS genes were grown on benzoate. Distinct from the results obtained with photoautotrophic growth conditions, the results of studies with various CbbRRS mutant strains indicated that this two-component system did not affect the observed enhanced synthesis of form I RubisCO under benzoate growth conditions. These studies indicate that diverse growth conditions differentially affect the ability of the CbbRRS two-component system to influence cbb transcription.

Influence of precursors and inhibitor on the production of extracellular 5-aminolevulinic acid and biomass by Rhodopseudomonas palustris KG31.

5-Aminolevulinic acid (ALA) and the biomass of photosynthetic bacteria, Rhodopseudomonas palustris KG31, have very high potential for development and exploitation as bioherbicide and biofertilizer respectively. In this work, the effects of two precursors and an inhibitor of aminolevulinic dehydratase (ALAD) added to the VFA culture medium on the production of ALA and biomass were investigated. The experimental runs were carried out according to a Box-Behnken design. The precursors were added to the medium at the beginning of cultivation, while the inhibitor was added after 24 h. Statistical analysis indicated that levulinic acid (LA) has a positive effect on ALA production while glycine has a negative effect on biomass production. In order to enhance both ALA and biomass products, the most suitable medium was VFA medium supplemented with 3.0 mM glycine and 10 mM LA, giving ALA and biomass of 182.91 microM and 3.1 gDCW/l within 54 h.

Herbicide binding in the bacterial photosynthetic reaction center.

The ureas and phenolics are two major classes of herbicides that act on Photosystem II (PSII) and are normally inactive in the photosynthetic reaction centers of purple bacteria. However, the triazine-resistant mutant T4 from Rhodopseudomonas (Rps.) viridis, which has the tyrosine residue at position 222 on the L subunit substituted for phenylalanine (TyrL222Phe), is sensitive to both ureas and phenolics. Since for the first time structural data on urea binding are available, T4 is a particularly interesting model for the herbicide-binding site of PSII.

Bacterial Longevity Requires Protein Synthesis and a Stringent Response.

Gram-negative bacteria in infections, biofilms, and industrial settings often stop growing due to nutrient depletion, immune responses, or environmental stresses. Bacteria in this state tend to be tolerant to antibiotics and are often referred to as dormant. Rhodopseudomonas palustris, a phototrophic alphaproteobacterium, can remain fully viable for more than 4 months when its growth is arrested. Here, we show that protein synthesis, specific proteins involved in translation, and a stringent response are required for this remarkable longevity. Because it can generate ATP from light during growth arrest, R. palustris is an extreme example of a bacterial species that will stay alive for long periods of time as a relatively homogeneous population of cells and it is thus an excellent model organism for studies of bacterial longevity. There is evidence that other Gram-negative species also continue to synthesize proteins during growth arrest and that a stringent response is required for their longevity as well. Our observations challenge the notion that growth-arrested cells are necessarily dormant and metabolically inactive and suggest that such bacteria may have a level of metabolic activity that is higher than many would have assumed. Our results also expand our mechanistic understanding of a crucial but understudied phase of the bacterial life cycle.IMPORTANCE We are surrounded by bacteria, but they do not completely dominate our planet despite the ability of many to grow extremely rapidly in the laboratory. This has been interpreted to mean that bacteria in nature are often in a dormant state. We investigated life in growth arrest of Rhodopseudomonas palustris, a proteobacterium that stays alive for months when it is not growing. We found that cells were metabolically active, and they continued to synthesize proteins and mounted a stringent response, both of which were required for their longevity. Our results suggest that long-lived bacteria are not necessarily inactive but have an active metabolism that is well adjusted to life without growth.

Improved phototrophic H2 production with Rhodopseudomonas palustris WP3-5 using acetate and butyrate as dual carbon substrates.

An indigenous purple nonsulfur bacterium Rhodopseudomonas palustris WP3-5 was used to produce hydrogen phototrophically from acetate (HAc) and butyrate (HBu), which are the major soluble products from acidogenic dark fermentation. Statistical experimental design methodology was applied to identify optimal composition of the two carbon substrates in the medium, leading to better H2 production performance of R. palustris WP3-5. Three performance indexes were used to assess the effectiveness of the phototrophic H2 production; they were H2 yield (Y H2), maximum H2 production rate (Rmax) and maximum cumulative H2 evolution (Hmax). An overlay contour plot was used to determine the optimal concentration range of HAc and HBu, taking into account all three performance indexes (i.e., Rmax, Hmax, and Y H2) simultaneously. With the response surface analysis, R. palustris WP3-5 could produce H2 efficiently with the best Rmax, Hmax, and Y H2 of 39.5 ml/h, 2738 ml, and 51.6%, respectively. This performance is superior to most reported values in the literature, indicating that the statistical experimental design is an effective tool to improve phototrophic H2 production with R. palustris WP3-5.

Increasing CoQ10 production by Rhodopseudomonas palustris J001 using a two-stage fermentation process.

CoQ10 is used not only as a medicine but also as a food supplement due to its various physiological activities. The production of CoQ10 by microbes is a successful approach for generating large amounts of this natural product. The effects of dissolved oxygen (DO) contents and the two-stage fermentation process on cell growth and CoQ10 production by Rhodopseudomonas palustris J001 were investigated. The optimal DO contents for cell growth and CoQ10 production were 45% and 15%, respectively. A two-stage fermentation process, which consists of a 1st stage with 45% DO, a 2nd stage with 15% DO and a synchronous feeding of 2.0% NaAc at the switching time (42 h after inoculation), has proven to be the optimum fermentation process for the production of CoQ10. The maximum biomass, CoQ10 production and CoQ10 production rate were 1.31 g l(-1), 89.1 mg l(-1), and 1.142 mg l(-1) h(-1), respectively, increased by 28%, 585% and 426% as compared to the one-stage batch production with 45% DO. The DO level was the major factor to increase the CoQ10 production by the two-stage process.

Reduction in arsenic toxicity and uptake in rice (Oryza sativa L.) by As-resistant purple nonsulfur bacteria.

This study aimed to investigate the potential of Rhodopseudomonas palustris C1 and Rubrivivax benzoatilyticus C31 to ameliorate As toxicity and to reduce As uptake in rice. Strain C1 was superior to strain C31 for siderophore production. The mixed culture (1: 1) was most effective in reducing the toxicity of As species [As(III) and/or As(V), each 30 mg/l] by yielding maximal germination index that related to α- and ß-amylase activities in two Thai rice cultivars (HomNil: HN and PathumThani 1: PT). Arsenic toxicity to the seed germination followed the order: mixed As species > As(III) > As(V); and the toxicity was reduced in inoculated sets, particularly with a mixed culture. The mixed culture significantly enhanced rice growth under As stress in both rice cultivars as indicated by an increase in the production of chlorophyll a and b, and also supporting the non-enzymatic (carotenoids, lipid oxidation, and nitric oxide) and enzymatic (superoxide dismutase, ascorbate peroxidase, catalase, and glutathione reductase) activities. These were concomitant with productions of 5-aminolevulinic acid, indole-3-acetic acid, exopolymeric substances, and siderophores which significantly reduced As accumulation in treated rice. It can be concluded that the mixed culture has great potential to ameliorate rice from As toxicity by preventing As species entry into rice for enhancing rice growth and also for reducing As accumulation to produce safe rice from rice grown in contaminated paddy fields.

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

Rhodopseudomonas palustris strains PS3 and YSC3 are purple non-sulfur phototrophic bacteria isolated from Taiwanese paddy soils. PS3 has beneficial effects on plant growth and enhances the uptake efficiency of applied fertilizer nutrients. In contrast, YSC3 has no significant effect on plant growth. The genomic structures of PS3 and YSC3 are similar; each contains one circular chromosome that is 5,269,926 or 5,371,816 bp in size, with 4,799 or 4,907 protein-coding genes, respectively. In this study, a large class of genes involved in chemotaxis and motility was identified in both strains, and genes associated with plant growth promotion, such as nitrogen fixation-, IAA synthesis- and ACC deamination-associated genes, were also identified. We noticed that the growth rate, the amount of biofilm formation, and the relative expression levels of several chemotaxis-associated genes were significantly higher for PS3 than for YSC3 upon treatment with root exudates. These results indicate that PS3 responds better to the presence of plant hosts, which may contribute to the successful interactions of PS3 with plant hosts. Moreover, these findings indicate that the existence of gene clusters associated with plant growth promotion is required but not sufficient for a bacterium to exhibit phenotypes associated with plant growth promotion.

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

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.