Interaction of pretilachlor with PS-II activity of the cyanobacterium Desmonostoc muscorum PUPCCC 405.10.

Interaction of pretilachlor with photosystem (PS)-II of the cyanobacterium Desmonostoc muscorum PUPCCC 405.10 has been studied in this paper. Pretilachlor negatively affected growth, chlorophyll a (Chl a), photosynthesis, and carbon dissimilation in a dose-dependent manner. Effects were also observed in PSs, especially PS-II (an 11-35% decrease), as well as the whole photosynthetic electron transport activity. The fluorescence emission spectrum of Chl a revealed a dose-dependent effect of pretilachlor on both the antenna and the core complex of PSs, with more severe effect on the former. Data of O-J-I-P fluorescence transient of Chl a revealed that pretilachlor interfered with electron flow between QA and QB sites of PS-II. It was further observed that pretilachlor decreased maximum fluorescence, variable and relative variable fluorescence, maximum quantum yield, quantum yield of electron transport, the rate of trapped exciton movement, quantum yield of electron transfer, and performance index of primary photochemistry; however, there was a progressive increase in the net rate of PS-II closure, quantum yield of energy dissipation, and effective antenna size per active reaction center. A decrease in photosynthetic activity leads to a decrease in carbon dissimilation, as evidenced by low activity of glucose-6-phosphate dehydrogenase and pyruvate kinase. Thus, pretilachlor, which is otherwise known to kill weeds by interfering with cell division, affected the growth of the cyanobacteria by interacting with PS-II.

Assessment of water quality condition and spatiotemporal patterns in selected wetlands of Punjab, India.

Wetlands are one of the most productive aquatic ecosystems on earth, and their water quality is an indicative of their suitability for maintaining various ecosystem services. In this study, different statistical techniques and water quality index (WQI) were employed to access the status and spatiotemporal patterns in water quality of seven selected (two natural and five manmade) wetlands of Punjab. The results revealed that the status of water quality in the selected wetlands was between good and poor during studied seasons (summer, monsoon, and winter) of year 2019. The principal component analysis identified three groups of wetlands with distinct water quality characteristics with spatial patterns: Kahnuwan Chhamb and Keshopur Miani having nearly similar values of pH, total dissolve salts, electrical conductivity, chemical oxygen demand, total alkalinity, bicarbonate and ammonium content; Ropar, Kanjli, and Harike having higher value of nutrients than the other wetlands; and Ranjit Sagar and Nangal with low value of measured water quality characteristics. Further, analysis of variance revealed that all analyzed water quality parameters showed temporal patterns in water quality except water pH, electrical conductivity, dissolved oxygen, biological oxygen demand, and phosphate content. This comparative study enhanced our knowledge about the spatiotemporal patterns in water quality and in the future will be helpful to the policymakers and concerned authorities for developing better water quality management strategies for these wetlands.

High production of carotenoids by the green microalga Asterarcys quadricellulare PUMCC 5.1.1 under optimized culture conditions.

Since carotenoids are important as natural colorants, antioxidants, neutraceutics and pharmaceutics, the aim of the present study was to find a new good source of these pigments. We hereby report a green microalga Asterarcys quadricellulare PUMCC 5.1.1 as a new and good producer of carotenoids. The organism produced 35±1.75 µg carotenoids mg-1 dry biomass during stationary phase in control cultures. The growth and carotenoids production by the test microalga were optimized by varying nutrient growth media, pH, nitrogen and phosphate source, salinity, light quality, intensity and duration. The optimized conditions for carotenoid production were: Bold basal (BB) medium with pH 8.5, containing with10 mM nitrate, 3.5 mM phosphate and 0.17 mM salinity and illuminated with blue light with 60 µmol m-2 s-1 photon flux light intensity. Cultivation of cultures in the above mentioned optimized conditions resulted in nearly 3.0 fold increase in carotenoid production compared to the control cultures grown in unmodified BB medium. Using HPTLC, four carotenoids have been identified as ß-carotene, lutein, astaxanthin and canthaxanthin. Further, carotenoids were also separated and purified by flash chromatography and the amounts of purified carotenoids were determined by HPLC. The organism produced 47.0, 28.7, 15.5 and 14.0 µg ß-carotene, lutein, astaxanthin and canthaxanthin mg-1 dry biomass, respectively, under optimized conditions. The amount of total carotenoids (118 µg mg-1 dry biomass) produced by Asterarcys quadricellulare PUMCC 5.1.1 under optimized culture conditions was significantly higher than control cultures. Thus, this microalgal strain is a promising candidate for carotenoid production at commercial level.

Cyanobacterial lectins characteristics and their role as antiviral agents.

Lectins are ubiquitous proteins/glycoproteins of non-immune origin that bind reversibly to carbohydrates in non-covalent and highly specific manner. These lectin-glycan interactions could be exploited for establishment of novel therapeutics, targeting the adherence stage of viruses and thus helpful in eliminating wide spread viral infections. Here the review focuses on the haemagglutination activity, carbohydrate specificity and characteristics of cyanobacterial lectins. Cyanobacterial lectins exhibiting high specificity towards mannose or complex glycans have potential role as anti-viral agents. Prospective role of cyanobacterial lectins in targeting various diseases of worldwide concern such as HIV, hepatitis, herpes, influenza and ebola viruses has been discussed extensively. The review also lays emphasis on recent studies involving structural analysis of glycan-lectin interactions which in turn influence their mechanism of action. Altogether, the promising approach of these cyanobacterial lectins provides insight into their use as antiviral agents.

Interaction between carbon and nitrogen metabolism during akinete development in the cyanobacterium Anabaena torulosa.

Nutrient enrichment with a nitrogen (as nitrate) or carbon (as fructose) source to unaerated diazo and photoautorophic cultures of the cyanobacterium Anabaena torulosa induced early development of akinetes with high frequency. When cultures under any mode of nutrition were aerated, akinetes were not differentiated. Unaerated cultures with nitrate nitrogen or fructose exhibited higher respiratory rates and nitrogen assimilation compared to aerated cultures. This was evidenced by increased respiratory O2 uptake and high activities of pyruvate kinase, malate dehydrogenase (NAD+), nitrogenase and nitrate reductase signifying that akinete forming unaerated cultures exhibited high carbon dissimilation and nitrogen assimilation resulting in high nitrogenous build up in the cells. Aerated, non-akinete cultures, on the other hand, were associated with low respiratory O2 uptake, low pyruvate kinase and malate dehydrogenase (NAD+) activities, suggesting that carbon dissimilation was not favoured either in presence of nitrate or fructose. Moreover, higher activity of NADP+ linked malate dehydrogenase and lower nitrate reductase activity in aerated cultures led to a high carbon and low nitrogen content of the cells resulting in high cellular C:N ratio. The results suggest that interaction between carbon and nitrogen metabolism regulates akinete development in A. torulosa.