Potential of Mn2+-Resistant Purple Nonsulfur Bacteria Isolated from Acid Sulfate Soils to Act as Bioremediators and Plant Growth Promoters via Mechanisms of Resistance

Abstract

Resistance mechanisms of acid Mn 2+-resistant purple nonsulfur bacteria (PNSB) were investigated to determine their ability to alleviate adverse effects of excess manganese on plant growth and productivity in acid sulfate soils (ASS). PNSB were isolated and selected based on their resistance to acid and manganese. Their resistance mechanisms were assessed on the basis of biosorption, bioaccumulation, and plant growth promoting properties. Six PNSB were selected for their resistance to Mn 2+ in acidic conditions (pH 3.5-5.5). They were identified as Rhodopseudomonas palustris strains TLS12, VNS19, VNS32, VNS62, and VNW95, and Rhodopseudomonas harwoodiae strain TLW42. Under aerobic dark and microaerobic light incubating conditions in aqueous solution at pH 4.25 for 30 min, these strains adsorbed Mn 2+ (1500 mg L −1) more effectively with released exopolymeric substances (EPS) than with their biomass. Under both incubating conditions, bioaccumulation of Mn 2+ diminished in the following order: cell wall, cytoplasm, plasma membrane. Scanning electron microscope-energy dispersive X-ray spectrometry (SEM-EDS) found accumulated manganese (0.30-0.67% of total elements) in bacterial cells caused morphological change in the form of wrinkles and bleb-like features on exterior surfaces. All selected strains under both incubating conditions released NH 4 + by N 2 fixing and PO 4 3− by solubilizing phosphate from various P-sources. Siderophores, 5-aminolevulinic acid (ALA), and indole-3-acetic acid (IAA) were also released and pH increased. The studied strains showed potential as bioremediators that could reduce Mn 2+ toxicity using EPS and effectively release nutrients and plant growth promoting substances to improve cultivation and fertility in acidic conditions.

Culture optimization to enhance carotenoid production of a selected purple nonsulfur bacterium and its activity against acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus

“…The difference might then affect carotenoid yield ( Y P/B ). The optimum pH value for the growth of Rhodopseudomonas spp., including strain KTSSG46, was reported to be around 7.0 32 . This allowed better growth in modified BIM II compared with the control (Table 4).…”

“…The optimum pH value for the growth of Rhodopseudomonas spp., including strain KTSSG46, was reported to be around 7.0. 32 This allowed better growth in modified BIM II compared with the control (Table 4). The lower growth observed in modified BIM III was possibly due to toxicants such as methanol, soap, and sodium chloride present in the crude glycerol.…”

“…Light intensity was varied at 4, 8, 14, and 30 W (equivalent to 1000, 1500, 2000, and 3000 lux), and one treatment was conducted in the absence of light by covering the culture with aluminum foil to create a microaerobic dark condition. The range of light intensity was designed based on the optimal light intensities of acid resistant PNSB determined by Khuong et al., 32 which were 2000–3000 lux. After 48 h, growth, carotenoid content, and pH were measured to compare the effects of the various light intensities.…”

Potential of Phototrophic Purple Nonsulfur Bacteria to Fix Nitrogen in Rice Fields

“…R. palustris strains and a Rhodopseudomonas harwoodiae strain were isolated from acid sulfate soils and selected based on their resistance to acid and manganese [124]. High levels of Mn 2+ in acid sulfate soils constitute a global health concern, and it is important to develop a suitable method of reducing Mn 2+ toxicity in soil to ensure the safety of agricultural products including rice.…”

Improvement of Nutrient Uptake, Yield of Black Sesame (Sesamum indicum L.), and Alluvial Soil Fertility in Dyke by Spent Rice Straw from Mushroom Cultivation as Biofertilizer Containing Potent Strains of Rhodopseudomonas palustris

“…Successful applications of the PNSB Rhodopseudomonas spp. as biofertilizers in paddy felds have been reported to improve adverse efects of soil environments such as acidity, salinity, and toxicity [23][24][25][26][27][28][29] to enhance rice growth at diferent stages [25][26][27][28][30][31][32][33] and also rice productivity [29,33]. Additionally, the PNSB promoted the growth of various crops such as sweet herb Stevia rebaudiana [34], cucumber seedling [35,36], and pineapple [37].…”