Influence of environmental heterogeneity on the distribution of micro-zooplankton community along the tropical coastal waters.

This study mainly focused on the water quality variability and distribution of micro-zooplankton (MZP) along the coastal waters of Tamil Nadu. Dendrogram analysis using water quality data categorized the study area into three regions: North (Chennai), Central (Puducherry), and South (Karaikal). The MZP consists of 40 ciliates and 8 dinoflagellates, with spirotrichea (52.4 %) significantly dominant, followed by dinophyceae (21.1 %), phyllopharyngea (14.7 %), and others (11.8 %). Paracyrtophoron tropicum, a new report in the coastal waters of India, was identified by comparing its molecular phylogeny (18S rRNA accession no: MT500569) to previously reported species. Statistical analysis revealed a positive correlation between P. tropicum abundance and water temperature, PO4, SiO4, TP, Chl-a, and Trichodesmium erythraeum, suggesting that they might not directly control the growth of P. tropicum but indirectly influence it via food availability, i.e., T. erythraeum. However, to understand these species interactions and ecological pathways, further long-term monitoring studies are required.

Impact of untreated sewage and thermal effluent discharges on the air-sea CO2 fluxes in a highly urbanized tropical coastal region.

Various biotic and abiotic factors regulate carbon dioxide (CO2) absorption and emission in coastal waters. Factors controlling the regional air-sea CO2 fluxes were studied in Tuticorin Bay, a highly urbanized region along the southeast coast of India. Significant spatial heterogeneity in the distribution of inorganic carbon components in the bay was observed based on the exposure to different anthropogenic pressures. Thermal effluent discharges made the south zone of the bay a strong CO2 source by enhancing heterotrophy. Untreated sewage discharges in the middle zone mediated eutrophic conditions leading to strong autotrophy and restricting the zone as a weak source of CO2. Irrespective of the anthropogenic stressors, biological processes dominated the air-sea CO2 fluxes in the Tuticorin Bay. The results indicated that micro-level studies are needed in understanding the carbon cycle in environments with multiple anthropogenic stressors.

Distribution patterns and seasonal variations in phytoplankton communities of the hypersaline Pulicat lagoon, India.

Phytoplankton structure and patterns are key components to forecast the net result of the gain and loss process that outline the resilience of the lagoon ecosystem. In order to understand the phytoplankton community structure and its relationship with the environmental variables in the shallow hypersaline Pulicat lagoon, east coast of India, observations were carried out during August 2018-January 2019 covering the three seasons: premonsoon (PrM), monsoon (M), and postmonsoon (PoM). The salinity of the lagoon varied with a minimum of 12.1 for the M and a maximum of 81.65 during the PoM. The clustering analysis performed on the phytoplankton abundance data separated the lagoon into three sectors: north sector (NS), central sector (CS), and south sector (SS). A total of 59 taxa/morphotypes from four taxonomic classes (Bacillariophyceae, Chlorophyceae, Cyanophyceae, and Dinophyceae) were recorded during the study period. The class Bacillariophyceae was dominant in the lagoon both spatially and temporally by 44.06% with Chaetoceros borealis as dominant species. Presence of characteristic species like Dunaliella sp. was observed in the higher salinity, whereas Pediastrum duplex and Scenedesmus sp. were dominant in the freshwater influx areas. The individual-based functional approach allowed grouping these taxa into 11 functional entities based on the derived 4 functional trait values (cell size, trophic regime, mobility, and coloniality). Formation of algal blooms of Protoperidinium sp. (3.3×105ind L-1) and Odentella sp. (2.8×105ind L-1) was observed in the SS during PoM as a result of reduced water exchange in the lagoon. During the same period, toxin-producing strains like Anabaena sp. and Nostoc sp. of Cyanophyceae were also recorded. Correlating the three sectors of the lake (NS, CS, and SS), it is observed that the physical, chemical, and biological properties of the lake varied continuously depending on the season and freshwater availability. Seasonal nutrient stoichiometry played a significant role in regulating the community structure and distribution pattern of phytoplankton communities of the lagoon.

Assessing the in situ bacterial diversity and composition at anthropogenically active sites using the environmental DNA (eDNA).

In this study, we identified the in situ bacterial groups and their community structure in coastal waters influenced by anthropogenic inputs. The use of environmental DNA (eDNA) and high throughput sequencing (HTS) were employed to derive accurate and reliable information on bacterial abundance. The V3 and V4 hypervariable regions of the 16S rRNA gene were amplified and the sequences were clustered into operational taxonomic units to analyze the site-specific variations in community composition. The percentage composition within the bacterial orders varied significantly among nearshore anthropogenic hotspots and offshore (5 km) samples. The microbial network constructed taking the bacterial abundance as nodes displayed strong positive and negative correlations within the bacterial families. Overall, the use of eDNA coupled with HTS is an incredible means for monitoring and assessing the abundance of bacterial communities and also serves as a biomonitoring tool to understand the degree of anthropogenic contamination in coastal waters.

Biological approaches practised using genetically engineered microbes for a sustainable environment: A review.

Conventional methods used to remediate toxic substances from the environment have failed drastically, and thereby, advancement in newer remediation techniques can be one of the ways to improve the quality of bioremediation. The increased environmental pollution led to the exploration of microorganisms and construction of genetically engineered microbes (GEMs) for pollution abatement through bioremediation. The present review deals with the successful bioremediation techniques and approaches practised using genetically modified or engineered microbes. In the present scenario, physical and chemical strategies have been practised for the remediation of domestic and industrial wastes but these techniques are expensive and toxic to the environment. Involving engineered microbes can provide a much safer and cost effective strategy in comparison with the other techniques. With the aid of biotechnology and genetic engineering, GEMs are designed by transforming microbes with a more potent protein to overexpress the desired character. GEMs such as bacteria, fungi and algae have been used to degrade oil spills, camphor, hexane, naphthalene, toluene, octane, xylene, halobenzoates, trichloroethylene etc. These engineered microbes are more potent than the natural strains and have higher degradative capacities with quick adaptation for various pollutants as substrates or cometabolize. The road ahead for the implementation of genetic engineering to produce such organisms for the welfare of the environment and finally, public health is indeed long and worthwhile.

Air quality assessment among populous sites of major metropolitan cities in India during COVID-19 pandemic confinement.

The present study aims to determine the impact of COVID-19 pandemic confinement on air quality among populous sites of four major metropolitan cities in India (Delhi, Mumbai, Kolkata, and Chennai) from January 1, 2020 to May 31, 2020 by analyzing particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), ammonia (NH3), sulfur dioxide (SO2), carbon monoxide (CO), and ozone levels. The most prominent pollutant concerning air quality index (AQI) was determined by Pearson's correlation analysis and unpaired Welch's two-sample t test was carried out to measure the statistically significant reduction in average AQI for all the four sites. AQI significantly plummeted by 44%, 59%, 59%, and 6% in ITO-Delhi, Worli-Mumbai, Jadavpur-Kolkata, and Manali Village-Chennai respectively. The findings conclude a significant improvement in air quality with respect to reduction of 49-73%, 17-63%, 30-74%, and 15-58% in the mean concentration of PM2.5, PM10, NH3, and SO2 respectively during the confinement for the studied locations. The p values for all of the four studied locations were found significantly less than the 5% level of significance for Welch's t test analysis. In addition, reduced AQI values were highly correlated with prominent pollutants (PM2.5 and PM10) during Pearson's correlation analysis. These positive results due to pandemic imprisonment might aid to alter the current policies and strategies of pollution control for a safe and sustainable environment. Graphical abstract.

Improved ethanol productivity and ethanol tolerance through genome shuffling of Saccharomyces cerevisiae and Pichia stipitis

Genome shuffling by recursive protoplast fusion between Saccharomyces cerevisiae and Pichia stipitis also known as Scheffersomyces stipitis resulted in a promising yeast hybrid strain with superior qualities than those of the parental strains in enhancing biofuel production. Our study focused on the substrate utilization, ethanol fermentation, and ethanol tolerance of the hybrids and the parental strains. The parental strain S. cerevisiae is limited to utilize only hexose sugars, and this leads to decrease in the ethanol yield when they are subjected to ethanol production from lignocellulosic biomass which is rich in pentose sugars. To overcome this limitation, we constructed a hybrid yeast strain through genome shuffling which can assimilate all the sugars present in the fermentation medium. After two rounds of recursive protoplast fusion, there was a higher increase in substrate utilization by hybrid SP2-18 compared to parental strain S. cerevisiae. SP2-18 was able to consume 34% of xylose sugar present in the fermentation medium, whereas S. cerevisiae was not able to utilize xylose. Further, the hybrid strain SP2-18 was able to reach an ethanol productivity of 1.03 g L−1 h−1, ethanol yield 0.447 g/g, and ethanol concentration 74.65 g L−1 which was relatively higher than that of the parental strain S. cerevisiae. Furthermore, the hybrid SP2-18 was found to be stable in the production of ethanol. The random amplified polymorphic DNA profile of the yeast hybrid SP2-18 shows the polymorphism between the parental strains indicating the migration of specific sugar metabolizing genes from P. stipitis, while the maximum similarity was with the parent S. cerevisiae

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Role of cyanobacteria in agricultural and industrial sectors: an outlook on economically important byproducts.

Cyanobacteria are potential organisms, which are used as food, feed and fuel. The unique characters of cyanobacteria include short generation times, their ubiquitous presence and efficient nitrogen fixing potential. Cyanobacteria are unique organisms performing photosynthesis, bioremediation of wastewater, high biomass and biofuel productions etc. They are also used in the treatment of industrial and domestic wastewaters for the utilization or removal of ammonia, phosphates and other heavy metals (Cr, Pb, Co, Cu, Zn). Biomasses of cyanobacteria are used as biofertilizers for the improvement of nutrient or mineral status and water-holding capacity of the soil. The secondary metabolites of cyanobacteria are used in pharmaceuticals, nutraceutical and chemical industries. In the industrial sector, value-added products from cyanobacteria such as pigments, enzymes and exopolysaccharides are being produced in large scales for biomedical and health applications. Age-old applications of cyanobacteria in agroecosystems as biofertilizers (Anabaena sp; Nostoc sp.) and in industrial sectors as food products (Spirulina) have motivated the researchers to come up with much more specific applications of cyanobacteria both in agricultural and in industrial sectors. Therefore, considering the effectiveness and efficiency of cyanobacteria, the present review has enlisted the standout qualities of cyanobacteria and their potential applications in agricultural and industrial sectors for the benefit of human beings and environment.

Improved ethanol productivity and ethanol tolerance through genome shuffling of Saccharomyces cerevisiae and Pichia stipitis.

Genome shuffling by recursive protoplast fusion between Saccharomyces cerevisiae and Pichia stipitis also known as Scheffersomyces stipitis resulted in a promising yeast hybrid strain with superior qualities than those of the parental strains in enhancing biofuel production. Our study focused on the substrate utilization, ethanol fermentation, and ethanol tolerance of the hybrids and the parental strains. The parental strain S. cerevisiae is limited to utilize only hexose sugars, and this leads to decrease in the ethanol yield when they are subjected to ethanol production from lignocellulosic biomass which is rich in pentose sugars. To overcome this limitation, we constructed a hybrid yeast strain through genome shuffling which can assimilate all the sugars present in the fermentation medium. After two rounds of recursive protoplast fusion, there was a higher increase in substrate utilization by hybrid SP2-18 compared to parental strain S. cerevisiae. SP2-18 was able to consume 34% of xylose sugar present in the fermentation medium, whereas S. cerevisiae was not able to utilize xylose. Further, the hybrid strain SP2-18 was able to reach an ethanol productivity of 1.03 g L-1 h-1, ethanol yield 0.447 g/g, and ethanol concentration 74.65 g L-1 which was relatively higher than that of the parental strain S. cerevisiae. Furthermore, the hybrid SP2-18 was found to be stable in the production of ethanol. The random amplified polymorphic DNA profile of the yeast hybrid SP2-18 shows the polymorphism between the parental strains indicating the migration of specific sugar metabolizing genes from P. stipitis, while the maximum similarity was with the parent S. cerevisiae.

Cytomorphological and nitrogen metabolic enzyme analysis of psychrophilic and mesophilic Nostoc sp.: a comparative outlook.

Cyanobacterial diazotrophs play a significant role in environmental nitrogen economy despite their habitat either tropical or polar. However, the phenomenon by which it copes with temperature induced stress is poorly understood. Temperature response study of psychrophilic and mesophilic Nostoc strains explores their adaptive mechanisms. The selected psychrophilic and mesophilic strains were confirmed as Nostoc punctiforme and Nostoc calcicola respectively, by ultrastructure and 16S rDNA phylogeny. The psychrophilic strain has extensive glycolipid and polysaccharide sheath along with characteristic deposition of cyanophycin, polyhydroxybutyrate granules, and carboxysomes. This is possibly an adaptive strategy exhibited to withstand the freezing temperature and high intense of ultraviolet rays. The biomass measured in terms of dry weight, protein, and chlorophyll indicated a temperature dependant shift in both the psychrophilic and mesophilic strains and attained maximum growth in their respective temperature niches. At low temperature, psychrophilic organism exhibited nitrogenase activity, while mesophilic strains did not. The maximum glutamine synthetase activity was observed at 4 °C for psychrophilic and 37 °C for mesophilic strains. Activity at 4 °C in psychrophilic strains revealed their energetic mechanism even at low temperature. The nitrate and nitrite reductase of both psychrophilic and mesophilic strains showed maximum activity at 37 °C denoting their similar nitrogen assimilating mechanisms for combined nitrogen utilization. The activity studies of nitrogen fixation/assimilation enzymes have differential effects at varying temperatures, which provide valuable insights of physiological contribution and role of Nostoc strains in the biological nitrogen cycle.