Morphogenetic Characterization and Phyco-remediation Potential of Selected Algal Flora Collected from Poonch AJK

Abstract

Microalgae, a source of food and nutrition, has been recently explored for their diverse potential applications across various scientific fields. Despite enormous potential, no baseline research has been conducted on freshwater algae locally. In this study, microalgae samples were collected from stream ecosystem in Hajira Poonch, AJK. In the collected samples, algae were isolated and identified morphologically and genetically. Microalgae enrichment was performed in vitro through solid streak plating. Axenic cultures developed on BBM and BG11 media. Green algae were commonly found accounting for 72% of the total, while 28% blue green types were also observed in the collection (field samples). During culturing, among green algal types, members of the family Scenedesmaceae were found most frequently, other green taxa were represented by either one or two species only. Among blue green types, Phormidium and Oscillatoria were observed frequently. Seven strains of green Desmodemus communis, Desmodesmus subspicatus, Scenedesmus dimorphus, Scenedesmus bijugas, Scenedesmus sp.1, Scenedemus sp.2, and Scenedesmus sp.3 were identified that belonged to the family Scenedesmaceae. These strains have been reported for the first time from Hajira Poonch, AJK. The isolated strains of Scenedesmaceae were assessed for their tolerance against heavy metals (Cd and Pb). Two strains (namely Desmodesmus subspicatus R3 and Scenedesmus dimorphus H9) were identified as the most effective in tolerating the elevated concentrations of Cd and Pb. These were assessed further for their Cd and Pb adsorption capacity under different conditions including pH, contact time, initial concentrations of metal ions in dried and living forms of algae. The experimental data were validated with adsorption kinetic (pseudo first order, pseudo second order and intra particle diffusion), and isotherm (Freundlich, Langmuir and Temkin isotherm) models revealing a chemisorption mechanism homogenously spanning over species surface. The RNASeq of Desmodesmus subspicatus (strain R3) revealed that 42,347,092, 47,483,530 for control and 39,333,360, 33,492,989 for Cd treated libraries respectively. Analysis further showed clear evidence of 615 differentially expressed genes. Among these, 452 genes were found to be up regulated while 163 genes were down regulated in the Cd stressed sample. The KEGG pathway analysis identified 10 key pathways to be involved in mitigating Cd stress. Metabolic pathways have a higher number of genes and biosynthesis of nucleotide sugars has a lower number of genes. Our results demonstrated that Cd retarded the growth rate in Desmodesmus subspicatus, which 2 was followed by a significant reduction in photosynthetic pigment and a decrease in the expression of genes linked with the photosynthetic system and oxidative phosphorylation. This study provides novel insights for understanding the molecular mechanisms of Desmodesmus subspicatus to cadmium-induced stress.