Psychrotrophs of the genus Janthinobacterium with potential to weather potassium aluminosilicate mineral

Metagenomic views on taxonomic and functional profiles of the Himalayan Tsomgo cold lake and unveiling its deterzome potential

Cold habitat is considered a potential source for detergent industry enzymes. This study aims at the metagenomic investigation of Tsomgo lake for taxonomic and functional annotation, unveiling the deterzome potential of the residing microbiota at this site. The present investigation revealed molecular profiling of microbial community structure and functional potential of the high-altitude Tsomgo lake samples of two different temperatures, harvested during March and August. Bacteria were found to be the most dominant phyla, with traces of genomic pieces of evidence belonging to archaea, viruses, and eukaryotes. Proteobacteria and Actinobacteria were noted to be the most abundant bacterial phyla in the cold lake. In-depth metagenomic investigation of the cold aquatic habitat revealed novel genes encoding detergent enzymes, amylase, protease, and lipase. Further, metagenome-assembled genomes (MAGs) belonging to the psychrophilic bacterium, Arthrobacter alpinus, were constructed from the metagenomic data. The annotation depicted the presence of detergent enzymes and genes for low-temperature adaptation in Arthrobacter alpinus. Psychrophilic microbial isolates were screened for lipase, protease, and amylase activities to further strengthen the metagenomic findings. A novel strain of Acinetobacter sp. was identified with the dual enzymatic activity of protease and amylase. The bacterial isolates exhibited hydrolyzing activity at low temperatures. This metagenomic study divulged novel genomic resources for detergent industry enzymes, and the bacterial isolates secreting cold-active amylase, lipase, and protease enzymes. The findings manifest that Tsomgo lake is a potential bioresource of cold-active enzymes, vital for various industrial applications.

Psychrotolerant Mesorhizobium sp. Isolated from Temperate and Cold Desert Regions Solubilizes Potassium and Produces Multiple Plant Growth Promoting Metabolites

Soil potassium (K) supplement depends intensively on the application of chemical fertilizers, which have substantial harmful environmental effects. However, some bacteria can act as inoculants by converting unavailable and insoluble K forms into plant-accessible forms. Such bacteria are an eco-friendly approach for enhancing plant K absorption and consequently reducing utilization of chemical fertilization. Therefore, the present research was undertaken to isolate, screen, and characterize the K solubilizing bacteria (KSB) from the rhizosphere soils of northern India. Overall, 110 strains were isolated, but only 13 isolates showed significant K solubilizing ability by forming a halo zone on solid media. They were further screened for K solubilizing activity at 0 °C, 1 °C, 3 °C, 5 °C, 7 °C, 15 °C, and 20 °C for 5, 10, and 20 days. All the bacterial isolates showed mineral K solubilization activity at these different temperatures. However, the content of K solubilization increased with the upsurge in temperature and period of incubation. The isolate KSB (Grz) showed the highest K solubilization index of 462.28% after 48 h of incubation at 20 °C. The maximum of 23.38 µg K/mL broth was solubilized by the isolate KSB (Grz) at 20 °C after 20 days of incubation. Based on morphological, biochemical, and molecular characterization (through the 16S rDNA approach), the isolate KSB (Grz) was identified as Mesorhizobium sp. The majority of the strains produced HCN and ammonia. The maximum indole acetic acid (IAA) (31.54 µM/mL) and cellulase (390 µM/mL) were produced by the isolate KSB (Grz). In contrast, the highest protease (525.12 µM/mL) and chitinase (5.20 µM/mL) activities were shown by standard strain Bacillus mucilaginosus and KSB (Gmr) isolate, respectively.

Prospecting catabolic diversity of microbial strains for developing microbial consortia and their synergistic effect on Lentil (Lens esculenta) growth, yield and iron biofortification

Carbon profiling of heterotrophic microbial inoculants is worthwhile strategy for formulating consortium-based biofertilizers. Consortium-based biofertilizers are better than single strain-based biofertilizers for sustaining agricultural productivity and enhancing micronutrient concentration in grains. Currently, we investigated catabolic diversity among microbes using different carbon sources and certain enzyme activities. A field experiment was also carried to evaluate the synergistic effect of selected lentil Rhizobia and plant growth promoting rhizobacteria strains on lentil growth, yield, nitrogen fixation, and Fe-content in seeds. On the basis of carbon profiling Bacillus sp. RB1 and Pseudomonas sp. RP1 were selected for synergistic study with lentil Rhizobium-Rhizobium leguminosarum subsp. viciae RR1. Co-inoculation of Rhizobium with Bacillus sp. RB1 and Pseudomonas sp. RP1 significantly enhanced the plant height, number of pods per plant, seed yield, number of nodules per plant, nitrogenase activity and Fe biofortification in seed over the single Rhizobium inoculation or dual combination of Rhizobium + RB1 or RP1.The response of single Rhizobium inoculation or co-inoculation of Rhizobium with RB1 and/or RP1 at 50% RDF was almost similar or higher than full dose of recommended N:P:K with respect to lentil yield and Fe biofortification in seed. This deciphered grouping of microbial strains for formulation of microbial consortia-based biofertilizers and revealed the promise of consortium of Rhizobium and plant growth promoting rhizobacteria in improving the biological yield and enhancing the Fe content of lentil seed.

Spatial distribution and identification of bacteria in stressed environments capable to weather potassium aluminosilicate mineral

In the present study, we studied the distribution of silicate mineral weathering bacteria (SWB) in stressed environments that release potassium from insoluble source of mineral. Out of 972 isolates, 340 isolates were positive and mineral weathering potential ranged from 5.55 to 180.05%. Maximum abundance of SWB occurred 44.71% in saline environment followed by 23.53% in low temperature and 12.35% each in high temperature and moisture deficit. Among isolates, silicate mineral weathering efficiency ranged from 1.9 to 72.8 μg mL^-1 available K in liquid medium. The phylogenetic tree of SWB discriminated in three clusters viz. Firmicutes, Proteobacteria and Actinobacteria. This is the first report on SWB in stressed environments and identified 27 genera and 67 species which is not reported earlier. Among them Bacillus was the predominant genera (58.60%) distantly followed by Pseudomonas (6.37%), Staphylococcus (5.10%) and Paenibacillus (4.46%). These bacterial strains could be developed as inoculants for biological replenishment of K in stressed soils. Graphical abstract.