Search

Drought stress adversely affects plant health and productivity. Recently, drought-resistant bacterial isolates are used to combat drought resistance in crops. In this in vitro study, 20 bacterial isolates were isolated from harsh soil; their drought tolerance was evaluated using four concentrations of polyethylene glycol (PEG) 6000. The two most efficient isolates (DS4 and DS9) were selected and identified using 16S rRNA genetic sequencing. They were registered in the NCBI database and deposited under accession numbers MW916285 and MW916307 for Bacillus cereus (DS4) and Bacillus albus (DS9), respectively. These isolates were screened for plant growth-promoting properties compared to non-stressed conditions. Biochemical parameters; Proline, salicylic acid, gibberellic acid (GA), indole acetic acid (IAA), antioxidant activity, and antioxidant enzymes were measured under the same conditions, and in vitro seed germination was tested under stress conditions and inoculation with selected isolates. The results showed that under the harsh conditions of PEG6000, DS4 produced the highest amount of IAA of 1.61 µg/ml, followed by DS9 with 0.9 µg/ml. The highest amount of GA (49.95 µg/ml) was produced by DS9. On the other hand, the highest amount of siderophore was produced from DS4 isolate followed by DS9. Additionally, DS4 isolate recorded the highest exopolysaccharide (EPS) content of 3.4 mg/ml under PEG (-1.2 MPa) followed by DS9. The antioxidant activity increased in PEG concentrations depending manner, and the activity of the antioxidant enzymes increased, as catalase (CAT) recorded the highest activity in DS4 with an amount of 1.095 mg/ml. additionally, an increase in biofilm formation was observed under drought conditions. The isolated mixture protected the plant from the harmful effects of drought and showed an increase in the measured variables. Under unstressed conditions, the highest rates of emulsification index (EI 24%) were obtained for DS4 and DS9, at 14.92 and 11.54, respectively, and decreased under stress. The highest values of germination, total seedling length, and vigor index were obtained upon inoculation with the combination of two strains, and were 100%, 4.10 cm, and 410, respectively. Therefore, two strains combination is an effective vaccine capable of developing and improving drought tolerance in dryland plants.

The presence of 4-nitrophenol (4-NP) in the wastewater industry causes toxicity and inhibition of the anaerobic degrading bacteria. The anaerobes in the multistage anaerobic reactor were loaded by 30.0 mg/gVS Graphene nanoparticles (MAR-Gn) as an electron acceptor to detoxify wastewater industry. The half maximal inhibitory concentration (IC50) was reduced from 455 ± 22.5 to 135 ± 12.7 μg Gallic acid equivalent/mL at 4-NP loading rate of 47.9 g/m3 d. Furthermore, 4-NP was decreased by a value of 83.7 ± 4.9% in MAR-Gn compared to 65.6 ± 4.8% in control MAR. The 4-aminophenol (4-AP) recovery was accounted for 44.8% in the MAR-Gn at an average oxidation-reduction potential (ORP) of − 167.3 ± 21.2 mV. The remaining portions of 4-NP and 4-AP in the MAR-Gn effluent were efficiently removed by baffled high rate algal pond (BHRAP), resulting in overall removal efficiency of 91.6 ± 6.3 and 92.3 ± 4.6%, respectively. The Methanosaeta (52.9%) and Methanosphaerula (10.9%) were dominant species in MAR-Gn for reduction of 4-NP into 4-AP. Moreover, Chlorophyta cells (Chlorella vulgaris, Scenedesmus obliquus, Scenedesmus quadricauda and Ulothrix subtilissima were abundant in the BHRAP for complete degradation of 4-NP and 4-AP.

Cyanobacteria are immense sources of several pharmacological compounds such as flavonoids and carotenoids with anti-inflammatory and antioxidant activity. Two novel cyanobacterial isolates were isolated and identified by sequencing of 16S rRNA gene. The results revealed that the two isolates are Sphaerospermopsis aphanizomenoides (KU212886.1) and Cronbergia siamensis (KY296358.1). The BLAST alignment showed that the nearest NCBI deposited sequences were Cronbergia siamensis (NR153750.1) to C. siamensis (KY296358.1) and Sphaerospermopsis aphanizomenoides (LN846950.1) to S. aphanizomenoides (KU212886.1) with identity ratio 94% and 93%, respectively. The phylogenetic trees confirmed the same identity ratios on the roots of clades. The two newly identified isolates could be new species with novel and unique characteristics.