Soil salinity in rice cultivation areas is considered a severely limiting factor that adversely affects the quantity and quality of rice production in wetlands. Recently, the alternative use of salt-tolerant plant growth-promoting rhizobacteria (PGPR) inhabiting extreme saline conditions has gained remarkable attention and had positive effects on soil and crops. Therefore, a study has been initiated to develop a liquid biofertilizer formulation from locally isolated multi-strain salt-tolerant PGPR strains such as Bacillus tequilensis and Bacillus aryabhattai, using glycerol (5 mM), trehalose (10 mM), and polyvinylpyrrolidone (PVP) at 1% as additives to prolong the shelf-life of the bacteria. After 3 months of incubation, the bacterial population in the trehalose-supplemented mixed strain was highest at 9.73×107 CFU/mL, followed by UPMRE6 and UPMRB9 at 9.40×107 CFU/mL and 8.50×107 CFU/mL respectively. The results showed that the optimal trehalose concentration successfully prolonged the shelf-life of bacteria with minimal cell loss. Validation of quadratic optimization by response surface methodology revealed that the cell density of the mixed strain was 4.278×107 log CFU/mL after 24 h. The precision ratio was 99.7% higher than the predicted value in the minimized medium formulation: 0.267 g/mL trehalose, 1% glycerol, at 120 rpm agitation using the data analysis tools of Design Expert software. The population study confirmed the better and longer survival of salt-tolerant PGPR fortified with 10 mM trehalose, which was considered the best liquid biofertilizer formulation. Moreover, the optimized trehalose-glycerol liquid formulation can be used commercially as it is cost-effective.
Soil salinity has been one of the significant barriers to improving rice production and quality. According to reports, Bacillus spp. can be utilized to boost plant development in saline soil, although the molecular mechanisms behind the interaction of microbes towards salt stress are not fully known. Variations in rice plant protein expression in response to salt stress and plant growth-promoting rhizobacteria (PGPR) inoculations were investigated using a proteomic method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Findings revealed that 54 salt-responsive proteins were identified by mass spectrometry analysis (LC-MS/MS) with the Bacillus spp. interaction, and the proteins were functionally classified as gene ontology. The initial study showed that all proteins were labeled by mass spectrometry analysis (LC-MS/MS) with Bacillus spp. interaction; the proteins were functionally classified into six groups. Approximately 18 identified proteins (up-regulated, 13; down-regulated, 5) were involved in the photosynthetic process. An increase in the expression of eight up-regulated and two down-regulated proteins in protein synthesis known as chaperones, such as the 60 kDa chaperonin, the 70 kDa heat shock protein BIP, and calreticulin, was involved in rice plant stress tolerance. Several proteins involved in protein metabolism and signaling pathways also experienced significant changes in their expression. The results revealed that phytohormones regulated the manifestation of various chaperones and protein abundance and that protein synthesis played a significant role in regulating salt stress. This study also described how chaperones regulate rice salt stress, their different subcellular localizations, and the activity of chaperones.
Constructed wetlands (CWs) are affordable and reliable green technologies for the treatment of various types of wastewater. Compared to conventional treatment systems, CWs offer an environmentally friendly approach, are low cost, have fewer operational and maintenance requirements, and have a high potential for being applied in developing countries, particularly in small rural communities. However, the sustainable management and successful application of these systems remain a challenge. Therefore, after briefly providing basic information on wetlands and summarizing the classification and use of current CWs, this study aims to provide and inspire sustainable solutions for the performance and application of CWs by giving a comprehensive review of CWs' application and the recent development of their sustainable design, operation, and optimization for wastewater treatment. To accomplish this objective, thee design and management parameters of CWs, including macrophyte species, media types, water level, hydraulic retention time (HRT), and hydraulic loading rate (HLR), are discussed. Besides these, future research on improving the stability and sustainability of CWs are highlighted. This article provides a tool for researchers and decision-makers for using CWs to treat wastewater in a particular area. This paper presents an aid for informed analysis, decision-making, and communication. The review indicates that major advances in the design, operation, and optimization of CWs have greatly increased contaminant removal efficiencies, and the sustainable application of this treatment system has also been improved.