Screening and Characterization of Calcite Solubilizing Bacteria isolated from Marble Slurry dumped in Sukher, Udaipur, Rajasthan, India

Rajasthan is known as mineral majestic state as more than 50 types of minerals are produced including marble. Various types of marbles are spread over in 16 belts in 33 districts of the State. Large amount of marble slurry is discharged as a waste generated by the quarries which is dumped in empty pits in the forest area; thereby creating huge dumping area. The present study was undertaken for screening and characterization of calcite solubilizing bacteria from marble slurry collected from dumping yard in Sukher, Udaipur, India. Screening of calcite solubilizing bacteria was done on calcite agar medium. Calcite solubilizing efficiency (CSE) and calcite solubilizing activity index (CSAI) of the isolates were determined using 0.1% calcite agar medium at 37C for 10 days of incubation. Characterization of the isolates was done on the basis of morphological, biochemical and molecular methods. A total of 27 isolates appeared on calcite agar medium after an incubation of 24 hours at 37°C. Among them only 3 isolates namely isolate CS6, CS13 and CS25 showed clear halo zone of 20 mm, 29 mm and 2mm diameters respectively after 10 days of incubation indicating demonstrable calcite solubilizing activity. The maximum CSE and CSAI 362% and 4.62 respectively were observed for isolate CS13. Isolates CS6, CS13 and CS25 were identified as Exiguobacterium aquaticum CS6 (accession no. MK353511), Staphylococcous aureus CS13 (accession no. KY694446) and Bacillus endophyticus CS25 (accession no. MK353513) respectively. Two isolates that showed remarkable calcite solubilizing activity can be further analyzed for their possible use in restoration of marble slurry contaminated soil.

PHOSPHATSOLUBILIZING BACTERIA OF THE GENUS PSEUDOMONAS AND THE EFFICIENCY OF THEIR APPLICATION TO INCREASE THE AVAILABILITY OF PHOSPHORUS

Phosphorus is the second most important element for plants after nitrogen. Fertilizers based on it, used to stimulate productivity, are inaccessible for most crops, which leads to their accumulation in the soil and environmental pollution. The use of phosphate-solubilizing bacteria increases the amount of phosphorus absorbed by plants. In most publications describing this group of bacteria, their effectiveness is assessed only in vitro by the halo zones formed on agar media with calcium orthophosphate. The aim of this study was to compare the solubilizing properties of bacteria of the genus Pseudomonas on a solid nutrient medium, as well as in sand and soil. It was shown that all studied cultures of microorganisms are capable of solubilizing insoluble phosphate in Pikovskaya's medium. The most active strains were Pseudomonas laurentiana ANT 56 and Pseudomonas sp. IB 182, isolated from the activated sludge of biological treatment facilities and arable soil, respectively. Experiments with the introduction of strains showed that the amount of mobile phosphorus in the sand increased 2.6-3.8 times in two weeks (in the control 1.2 times), while in the experiment with soil, a significant increase in the content of mobile phosphorus compared to the control was recorded only for the strain P . laurentiana ANT 17 (by 29.1%). It is assumed that the high solubilizing activity of the P. laurentiana ANT 17 strain may be due to the complex action of mechanisms of different nature, including the synthesis of indolyl-3-acetic acid and exopolysaccharide. The studies carried out make it possible to consider this bacterial strain as a promising object for creating on its basis a biological preparation for agricultural purposes.

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.

BIODIVERSITY OF PHOSPHATE SOLUBILIZING FUNGIISOLATED FROM AGRICULTURAL FIELDS OF MARATHWADA REGION

Fungi are the core components of soil microorganisms, accounting for more of the soil biomass than bacteria, depending on soil depth and nutritional requirements. In the current study, phosphate solubilizing fungi were isolated from the soil of Maharashtras Marathwada area, and all fungal isolates were examined for their ability to solubilize phosphate.Only 11 fungal isolates out of a total of 40 were found to have P-solubilizing activity. After 48 hours of incubation, the fungal isolates Aspergillus niger (PQ9), Trichoderma spp (PQ36), and Penicillium spp (PQ19) demonstrated a considerable zone of solubilization with 34, 31 to 30 mm on selective agar medium. The potent phosphate solubilizing fungi were identified in 18SrRNA analysis.The study, therefore, proposed that these fungal species have strong phosphate solubilizing properties and can be used for excellent crop productivity as a biofertilizer.

Phytate Exudation by the Roots of Pteris Vittata Can Dissolve Colloidal Fepo4

Phosphorus (P) is limiting nutrient in soil system. The P availability in soil strongly depend on Iron (Fe) speciation. Colloidal iron phosphate (FePO4coll) is an important phosphorus (P) fraction in soil solution that carry P from soil to water bodies. This study tested the hypothesis that phytate exudation by Pteris vittata (P. vittata) can dissolve FePO4coll that leads to release of P and Fe. The phytate exudation in P. vittata increased from 434−2136 mg kg−1 as the FePO4coll concentration increased from 0−300 mM. The total P in P. vittata tissue increased from 2.88 to 8.28 g kg−1, the trichloroacetic acid P fractions (TCA fractions) were: inorganic P (0.86–5.10 mg g−1), soluble organic P (0.25–0.87 mg g−1), and insoluble organic P (0.16–2.03 mg g−1) which leads to higher biomass as FePO4coll increased from 0−300 mM. The linear regression analysis showed that FePO4 solubilizing activity has a positive correlation with TP, TCA P fractions in P. vittata, TP in growth media, and root exudates. This study shows that phytate exudation dissolved the FePO4coll due to the chelation effect of phytic acid on Fe, and due to the high Fe–P solubilizing activity in root exudates of P. vittata.

Potassium-Solubilizing Activity of Bacillus aryabhattai SK1-7 and Its Growth-Promoting Effect on Populus alba L.

In the present study, the potassium-solubilizing characteristics of Bacillus aryabhattai SK1-7 and its growth-promoting effect on plants were evaluated to determine the biotechnological potential of this bacterium in alleviating soil potassium deficiency. The potassium-solubilizing activity of SK1-7 was determined by fermentation. Additionally, the fermentation broth was determined by flame spectrophotometry. The aluminum and silicon ion contents in SK1-7 fermentation broth were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) after digestion with nitric acid hydrogen peroxide hydrofluoric acid. Scanning electron microscopy (SEM)-based observations were performed to assess the morphological changes in potassium feldspar surfaces digested by potassium-solubilizing bacteria. In addition, the effects of SK1-7 on plant growth and soil physical and chemical properties were analyzed. After incubation for 7 days in a potassium-solubilizing medium, the concentration of potassium dissolved reached 10.8 μg/mL and the percentage of potassium released was 32.6%. The pH rapidly decreased from 7.2 to 4.321 within the first day and then further decreased to 3.90 after 7 days. After 7 days, the concentrations of aluminum and silicon in the fermentation broth were 1.01 and 24.19 μg/mL, respectively. The growth promotion assay results showed that SK1-7 has good growth-promoting effects on poplar and can effectively improve the available potassium content in poplar rhizosphere soil. The SK1-7 strain can effectively dissolve insoluble potassium to release soluble potassium ions and clearly promotes the growth of poplar after being applied to soil. Thus, the SK1-7 strain is a potassium-solubilizing microorganism with good application prospects.

Native bacteria isolated from roots and rhizosphere of Solanum lycopersicum L. increase tomato seedling growth under a reduced fertilization regime

In semiarid regions is important to use native strains best adapted to these environments to optimize plant-PGPR interaction. We aimed to isolate and characterize PGPR from roots and rhizosphere of a tomato crop, as well as studying the effect of its inoculation on tomato seedlings growth. We selected four strains considering their effectiveness of fixing nitrogen, solubilizing phosphate, producing siderophores and indole acetic acid. They belong to the genera Enterobacter, Pseudomonas, Cellulosimicrobium, and Ochrobactrum. In addition, we also analyzed the ability to solubilize Ca3(PO4)2, FePO4 and AlPO4 and the presence of one of the genes encoding the cofactor PQQ in their genome. Enterobacter 64S1 and Pseudomonas 42P4 showed the highest phosphorus solubilizing activity and presence of pqqE gene. Furthermore, in a tomato-based bioassay in speed-bed demonstrated that a sole inoculation at seedling stage with the strains increased dry weight of roots (49–88%) and shoots (39–55%), stem height (8–13%) and diameter (5–8%) and leaf area (22–31%) and were equal or even higher than fertilization treatment. Leaf nitrogen and chlorophyll levels were also increased (50–80% and 26–33%) compared to control. These results suggest that Enterobacter 64S1 and Pseudomonas 42P4 can be used as bio-inoculant in order to realize a nutrient integrated management.

Identification of phosphate-solubilizing microorganisms and determination of their phosphate-solubilizing activity and growth-promoting capability

Phosphate-solubilizing microorganisms have been considered as a novel alternative approach to provide phosphate fertilizers that promote plant growth. In this study, three strains were isolated and identified as Penicillium oxalicum FJG21, Penicillium oxalicum FJQ5, and Bacillus subtilis BPM12, with a relatively high phosphate-solubilizing activity. Various phosphate sources were investigated, and Ca3(PO4)2 was identified as the effective phosphate source. Factors governing the phosphate-solubilizing activity of the strains included carbon and nitrogen sources, initial pH, and fermentation time. A high soluble phosphorus content was achieved with 529.0 μg·mL-1, 514.0 μg·mL-1, and 330.7 μg·mL-1 for Penicillium oxalicum FJG21, Penicillium oxalicum FJQ5, and Bacillus subtilis BPM12, respectively. An inverse correlation of the quantity of soluble phosphorus content and the pH value of the medium was observed. In addition, Bacillus subtilis BPM12 displayed a prominent capability of producing indole acetic acid. Penicillium oxalicum FJG21 and Penicillium oxalicum FJQ5 exhibited high cellulase activities. These phosphate-solubilizing microorganisms with good phosphate-solubilizing capability and growth-promoting ability are the promising strains for agricultural utilization.

Pseudomonas plecoglossicida as a novel bacterium for phosphate solubilizing and indole-3-acetic acid-producing from soybean rhizospheric soils of East Java, Indonesia

Astriani M, Zubaidah S, Abadi AL, Suarsini E. 2020. Pseudomonas plecoglossicida as a novel bacterium for phosphate solubilizing and indole-3-acetic acid-producing from soybean rhizospheric soils of East Java, Indonesia. Biodiversitas 21: 578-586. The use of synthetic fertilizers to grow soybean (Glycine max (L.) Merrill) in a long time, can increase the risk of environmental damage. Therefore, the current study aimed to find phosphate solubilizing bacteria that can produce indole-3-acetic acid (IAA) hormone to minimize the use of chemical fertilizers. Superior isolates selected through characterization of phosphate solubilization activity on Pikovskaya medium, screening of IAA producing bacteria, quantitative estimation of phosphate solubilizing activity using a spectrophotometer, hypersensitivity assay, antagonist within isolate assay, and molecular identification of selected bacterial isolates using 16S rRNA sequencing with primer forward 63f and primer reverse 1387r. Among the isolated bacteria, isolate Arj8 showed the highest phosphate solubilizing activity and IAA production. Molecular identification indicated that isolate Arj8 shared 100% similarity with Pseudomonas plecoglossicida. The highest phosphate solubilizing activity (75.39 mg/L) and IAA production (38.89 ppm) recorded on day-3. Multiple potentialities of P. plecoglossicida as phosphate solubilizing and IAA producing bacterium are a novel finding in the development of bioinoculants as bio-fertilizers that can reduce dependency on synthetic chemical fertilizers.