Phylogenic diversity of bacteria associated with potentially toxic cyanobacteria Microcystis aeruginosa: a synthesis on its bloom dynamics.

The occurrence of toxic bloom-forming cyanobacteria, Microcystis aeruginosa, has been frequently reported worldwide. These colony forming toxic cyanobacteria harbour a wide range of heterotrophic bacterial communities. The present study has attempted to understand the bloom dynamics of M. aeruginosa along with isolating their colony-associated culturable heterotrophic bacteria from two freshwater ponds in south India with a persisting cyanobacterial bloom. The monthly monitoring of these study areas revealed the conducive role of warm, stagnant waters with high nutrients in forming M. aeruginosa bloom. The peak values of temperature, nitrate, and phosphate at station 1 reached up to 30.5 °C, 4.48 mg/L, 1.64 mg/L, and at station 2, 31 °C, 3.45 mg/L, and 0.62 mg/L, respectively. Twenty-eight bacterial isolates belonging to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria, and Firmicutes were obtained during the study. Among these 28 isolates, Firmicutes was dominant with the M. aeruginosa bloom from both the study areas.

Observed evidence for the impact of coastal currents on the recurrent Noctiluca scintillans blooms in the northwest Indian Ocean coast.

Recently, South Eastern Arabian Sea (SEAS) experiences recurrent winter blooms of green Noctiluca scintillans with serious ecological consequences. Here, the analysis of green N. scintillans blooms in SEAS for the past three consecutive years (2018-2021) is presented. The daily monitoring showed intense winter blooms during November with stable sea surface temperatures, high nitrate-phosphate concentrations and relatively lower pH levels. Dissolved oxygen concentration decreased to near hypoxia in the later stages of the bloom. Our analysis finds that the increased occurrence of N. scintillans blooms along SEAS is driven by the coastal currents (EICC), which transport the bloom species from the east coast (south west Bay of Bengal) to west coast of India. Therefore, the N. scintillans seeding from the South west Bay of Bengal intensifies winter blooms in SEAS, thus unveils the influence of oceanic currents in deciding the phytoplankton blooms across the coastal regions of north Indian Ocean.

Patterns and variability in the microplastic contamination along the southwest coast of India with emphasis on submarine groundwater discharge sites.

Beach sediments of the southwest coast of India were analysed to estimate the microplastic contamination with emphasis on the submarine groundwater discharge (SGD) zones. Both SGD and non-SGD sites were assessed for abundance, morphotype and polymer type of microplastics. Microplastic load was 230.429 ± 62.87 particles per 100 g. Fibre, mainly blue, was the abundant morphotype, followed by fragment, foam and film. The polymer types were POLYETHYLENE (PE) (30.77 %), POLYPROPYLENE (PP) (26.92 %), POLYAMIDE (PA) (19.23 %), POLYSTYRENE (PS) (11.54 %), ETHYLENE VINYL ACETATE (EVA) (7.692 %) and POLYVINYL CHLORIDE (PVC) (3.846 %). The SGD zones exhibited higher microplastic contamination with statistically significant variations from non SGD sites. The study accounts the levels of microplastic contamination along the southwest coast of India, a major fishery zone. The higher abundance of microplastic in the SGD zones indicates the significance of subterranean groundwater through flow as a pathway of anthropogenic contaminants towards marine ecosystems.

Role of mesoscale eddies in the sustenance of high biological productivity in North Eastern Arabian Sea during the winter-spring transition period.

Convective mixing, mesoscale eddies and regenerated production sustain an above-average biological productivity in the North East Arabian Sea (NEAS) during the winter-spring transition period. Satellite-derived long-term data sets on Chlorophyll-a (Chl-a), Sea Surface Height Anomaly (SSHA), Sea Surface Temperature (SST) and Okubo-Weiss parameterization show existence of number of mesoscale eddies, propagating and non-propagating, that contribute to the regional production. The dominance of Eddy Kinetic Energy (EKE) over the Available Potential Energy (APE) in the core depth and the diameter (120km) of the observed eddy being wider than the Rossby Radius of Deformation (RRD, 55 km), it is suggested that the baroclinic instability is a possible mechanism for the eddy formation. Spatial variation in APE and its influences on the regional dynamics, including chemical and biological response are explained. In the non-eddy areas, where convective mixing is active, diatoms (96.74%) dominated than dinoflagellates (3.14%), and the Chl-a in the Cold Core Eddy (CCE) were two to three folds higher to non-eddy regions. The abundance increased from core (58,152 cells L-1) to periphery (5.95 × 105 cells L-1) where the water column is less dynamic. Extensive blooms of the dinoflagellate green Noctiluca (N. scintillans) contribute to the very high cell density in the periphery of the CCE, where the currents were comparatively weak, and water column was more stable. Active mixing is associated with diatom dominance, followed by Noctiluca when the mixing slackens, making use of the available nutrients and supported by regenerated production. The bloom dynamics is explained for pre-bloom, bloom and post-bloom conditions with measurements on nutrients and plankton assemblages. The Noctiluca bloom (mid-March) is succeeded by Trichodesmium (April-May), in the stratified nutrient depleted, abundant light environment and propagated southwards. Observed increasing trends in the SSHA over the period indicate strengthening of stratification and hence altered production patterns in the NEAS.

Genetic identification and phylogenetic relationships of Indian clariids based on mitochondrial COI sequences.

Mitochondrial cytochrome C Oxidase I (COI) sequence variation among the clariid fishes of India (Clarias magur, C. dussumieri and C. gariepinus) and their relationship with other representative clariids was studied in this work. Three species were sampled and together with 23 COI sequences from GenBank were used to reconstruct phylogenetic relationships in the family Clariidae. The study revealed two clades: one consisting of the African species with C. dussumieri, and the other of Asian species suggesting the prevalence of intra-continental diversification of catfishes. This study further revealed that the genus Clarias is monophyletic. For the COI gene, the interspecies genetic divergence ranged from 0.056 to 0.182. The mean genetic difference between C. dussumieri and other selected African species in this study is 12.1%. It was also observed that the morphological similarity of C. dussumieri and C. magur was not replicated in the genetic level. Clarias dussumieri was more close to African catfish C. gariepinus thus indicating the utility of COI phylogeny to identify the well-known African-Asian relationships within catfishes. The results also showed that C. magur and C. batrachus are genetically distinct from each other.

Species identification of mixed algal bloom in the Northern Arabian Sea using remote sensing techniques.

Oceanic waters of the Northern Arabian Sea experience massive algal blooms during winter-spring (mid Feb-end Mar), which prevail for at least for 3 months covering the entire northern half of the basin from east to west. Ship cruises were conducted during winter-spring of 2001-2012 covering different stages of the bloom to study the biogeochemistry of the region. Phytoplankton analysis indicated the presence of green tides of dinoflagellate, Noctiluca scintillans (=N. miliaris), in the oceanic waters. Our observations indicated that diatoms are coupled and often co-exist with N. scintillans, making it a mixed-species ecosystem. In this paper, we describe an approach for detection of bloom-forming algae N. scintillans and its discrimination from diatoms using Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data in a mixed-species environment. In situ remote sensing reflectance spectra were generated using Satlantic™ hyperspectral radiometer for the bloom and non-bloom waters. Spectral shapes of the reflectance spectra for different water types were distinct, and the same were used for species identification. Scatter of points representing different phytoplankton classes on a derivative plot revealed four diverse clusters, viz. N. scintillans, diatoms, non-bloom oceanic, and non-bloom coastal waters. The criteria developed for species discrimination were implemented on MODIS data and validated using inputs from a recent ship cruise conducted in March 2013.

Comparative assessment of genetic variability in the populations of endemic and endangered yellow catfish, Horabagrus brachysoma (Teleostei: Horabagridae), based on allozyme, RAPD, and microsatellite markers.

The comparative assessment of genetic diversity using allozymes, random amplified polymorphic DNA (RAPD), and microsatellite markers was conducted in endemic and endangered yellow catfish (Horabagrus brachysoma) sampled from three locations in Western Ghats river systems of India. Among the three markers, microsatellites show more polymorphism, having 100% polymorphic loci, whereas allozymes show the least (56%). In RAPD, 60.5% of fragments were polymorphic. Observed heterozygosity and F(ST) values were very high in microsatellites, compared with the other markers. Microsatellite and RAPD markers reported a higher degree of genetic differentiation than allozymes among the populations depicted by pairwise F(ST)/G(ST), AMOVA, Nei's genetic distance, and UPGMA dendrogram. The three classes of markers demonstrated striking genetic differentiation between pairs of H. brachysoma populations. The data emphasize the need for fishery management, conservation, and rehabilitation of this species.

Kahalalide derivatives from the Indian sacoglossan mollusk Elysia grandifolia.

Two new cyclic depsipeptide derivatives, kahalalides R (1) and S (2), together with two known congeners, kahalalides F (3) and D (4), were isolated from the Indian sacoglossan mollusk Elysia grandifolia. The structures of the new compounds were unambiguously established on the basis of NMR spectroscopic (1H, 13C, COSY, HMBC) and mass spectrometric (FABMS, ESIMS, MALDI-TOF/PSD) data, which also included Marfey amino acid analyses. The new derivative kahalalide R was found to exert comparable or even higher cytotoxicity than the potential drug candidate kahalalide F toward the MCF7 human mammary carcinoma cell line.

Anion binding properties of reduced and oxidized iron-containing superoxide dismutase reveal no requirement for tyrosine 34.

We report the first spectroscopic observation of substrate analogue binding to the reduced state of iron superoxide dismutase from Escherichia coli (Fe(2+)SOD) and demonstrate that the pH dependence reflects inhibition of anion binding by ionized Tyr34, not loss of a positive contribution on the part of Tyr34's labile proton. This can also explain the pH dependence of the K(M) of Fe(2+)SOD. Thus, it appears that substrate binding to Fe(2+)SOD occurs in the second sphere and is not strongly coupled to hydrogen bond donation. Parallel investigations of substrate analogue binding to the oxidized state (Fe(3+)SOD) confirm formation of a six-coordinate complex and resolve the apparent conflict with earlier nuclear magnetic relaxation dispersion (NMRD) results. Thus, we propose that two F(-) ions can bind to the oxidized Fe(3+)SOD active site, either displacing the coordinated solvent or lowering its exchange rate with bulk solvent. We show that neutral Tyr34's unfavorable effect on binding of the substrate analogue N(3)(-) can be ascribed to steric interference, as it does not apply to the smaller substrate analogues F(-) and OH(-). Finally, we report the first demonstration that HS(-) can act as a substrate analogue with regard both to redox reactivity with FeSOD and to ability to coordinate to the active site Fe(3+). Indeed, it forms a novel green complex. Thus, we have begun to evaluate the relative importance of different contributions that Tyr34 may make to substrate binding, and we have identified a novel, redox active substrate analogue that offers new possibilities for elucidating the mechanism of FeSOD.

Chemical defense of Mediterranean sponges Aplysina cavernicola and Aplysina aerophoba.

The Mediterranean sponges Aplysina aerophoba and A. cavernicola accumulate brominated isoxazoline alkaloids including aplysinamisin-1 (1), aerophobin-2 (2), isofistularin-3 (3) or aerothionin (4) at concentrations up to 10% of their respective dry weights. In laboratory feeding experiments employing the polyphagous Mediterranean fish Blennius sphinx crude extracts of both Aplysina sponges were incorporated into artificial fish food at their physiological concentrations (based on volume) and offered to B. sphinx in choice feeding experiments against untreated control food. In addition to the Aplysina sponges, extracts from nine other frequently occurring Mediterranean sponges were likewise included into the experiments. Both Aplysina species elicited strong feeding deterrence compared to the other sponges tested. Bioassay-guided fractionation of A. cavernicola yielded the isoxazoline alkaloids aerothionin (4) and aplysinamisin-1 (1) as well as the 3,4-dihydroxyquinoline-2-carboxylic acid (8) as major deterrent constituents when tested at their physiological concentrations as present in sponges. Aeroplysinin-1 (5) and dienone (6), however, which are formed in A. aerophoba and A. cavernicola from isoxazoline precursors through bioconversion reactions upon tissue injury showed no or only little deterrent activity. Fractionation of a crude extract of A. aerophoba yielded aerophobin-2 (2) and isofistularin-3 (3) as major deterrent constituents against B. sphinx. We propose that the isoxazoline alkaloids 1-4 of Mediterranean Aplysina sponges as well as the 3,4-dihydroxyquinoline-2-carboxylic acid (8) (in the case of A. cavernicola) act as defensive metabolites against B. sphinx and possibly also against other predators while the antibiotically active bioconversion products aeroplysinin-1 (5) and dienone (6) may protect sponges from invasion of bacterial pathogens.

Proton-coupled electron transfer in Fe-superoxide dismutase and Mn-superoxide dismutase.

Fe-containing superoxide dismutase (FeSOD) and MnSOD are widely assumed to employ the same catalytic mechanism. However this has not been completely tested. In 1985, Bull and Fee showed that FeSOD took up a proton upon reduction [J. Am. Chem. Soc. 107 (1985) 3295]. We now demonstrate that MnSOD incorporates the same crucial coupling between electron transfer and proton transfer. The redox-coupled H(+) acceptor has been presumed to be the coordinated solvent molecule, in both FeSOD and MnSOD, however this is very difficult to test experimentally. We have now examined the most plausible alternative: that Tyr34 accepts a proton upon SOD reduction. We report specific incorporation of 13C in the C(zeta) positions of Tyr residues, assignment of the C(zeta) signal of Tyr34 in each of oxidized FeSOD and MnSOD, and direct NMR observations showing that in both cases, Tyr34 is in the neutral protonated state. Thus Tyr34 cannot accept a proton upon SOD reduction, and coordinated solvent is concluded to be the redox-coupled H(+) acceptor instead, in both FeSOD and MnSOD. We have also confirmed by direct 13C observation that the pK of 8.5 of reduced FeSOD corresponds to deprotonation of Tyr34. This work thus provides experimental proof of important commonalities between the detailed mechanisms of FeSOD and MnSOD.

Lattice-dictated conformers in bis(pyrazolyl)pyridine-based iron(II) complexes: Mössbauer, NMR, and magnetic studies.

Iron(II) complexes [FeL(2)](ClO(4))(2).CH(3)CN, [FeL(2)](BPh(4))(2).2CH(3)CN, and [FeL(2)](PF(6))(2) with an FeN(6) chromophore of the same ligand L (2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine) and differing counterions have been made and their crystal and molecular structures determined. The first two crystallized in triclinic space group P(-)1, and the third, with PF(6)(-) anion in Ibca space group. The FeL(2) complex ions in all lattices have similarly distorted octahedral geometry. Variable-temperature Mössbauer spectra of [FeL(2)](ClO(4))(2).CH(3)CN and [FeL(2)](PF(6))(2) measured in the temperature range 1.7-300 K reveal temperature-dependent populations of two different spin states with increased amount of low-spin form at high temperatures, a phenomenon unlike the normal spin crossover behavior; this abnormal behavior is interpreted here as due to the presence of two different conformations. It is very interesting to note that the two different compounds have similar spectra, Mössbauer parameters, and temperature dependence. But the variable-temperature Mössbauer spectra of [FeL(2)](BPh(4))(2).2CH(3)CN in the range 20-300 K do not show the presence of such different species but exhibit a clear phase transition at approximately 200 K. This phase transition is further supported by SQUID measurements. The results of variable-temperature (1)H NMR in CD(3)CN and the solution susceptibility measurement of all complexes also support the presence of high-spin and low-spin forms in solution. Hence, the complex ion [FeL(2)](2+) exhibits a thermally driven interconversion between low-spin and a high-spin structural forms-a phenomenon observed in the solid and solution states due to ligand dynamics. This is not due to the well-known spin crossover phenomenon. These results are compared with the case of normal spin crossover seen in [FeL'(2)](ClO(4))(2) (L' = 2,6-(bis(pyrazol-1-ylmethyl)pyridine)).

Hyperfine interaction in K2Ba[Fe(NO2)6].

Magnetic hyperfine splitting observed in the low temperature Mössbauer spectrum of potassium barium hexanitro ferrate(II), in the absence of any external field, is attributed to the 5T2g state of the central metal atom further split into a ground 5Eg state and a first excited 5B2g state under a distorted octahedral symmetry in contrast to the earlier prediction of 1A1g ground state on the basis of room temperature Mössbauer spectral and other properties. The central iron atom is coordinated to six nitrito groups (NO2-), having an oxidation state of +2. The temperature dependence of Mössbauer spectra is explained on the basis of electronic relaxation among the spin-orbit coupled levels of the 5Eg ground state. Various kinds of electronic relaxation mechanisms have been compared to explain the proposed mechanism. The observed temperature dependent spectra with varying internal magnetic field and line width can be explained by simple spin lattice relaxation.

Lupus anticoagulants in systemic lupus erythematosus: prevalence and clinical associations.

The prevalence of lupus anticoagulant (LAC) and its relation with reported clinical associations has been determined in 55 patients with systemic lupus erythematosus (SLE) from northern India who were studied prospectively. Kaolin clotting time was used to screen for LAC, which was detected in seven (13%) of the patients. Significant associations were found between LAC and thrombotic events, onset of disease at an early age, and disease of shorter duration. No statistically significant association could be found between LAC and recurrent abortions, pulmonary hypertension, thrombocytopenia, and neurological manifestations. It is concluded that LAC is a useful marker for a subset of patients with SLE at risk of thromboembolic events.

Coagulation abnormalities in systemic lupus erythematosus.

Coagulation profile was studied in 55 patients of systemic lupus erythematosus (SLE). Abnormal kaolin clotting time (KCT) was observed in fewer patients (12.9%) as compared to abnormal Russel's viper venom time (RVVT, 20.4%) or activated partial thromboplastin time (APTT, 32.7%). Prolonged prothrombin time (PT), observed in 7.3 per cent patients was not found to be a sensitive test for lupus anticoagulant (LAC). The correction of RVVT and KCT on addition of inosithin suggested a deficiency of platelet lipid factor in these patients. The initial value of uncorrected KCT in patient's plasma did not correlate with the amount of inosithin required for neutralisation. Occurrence of thromboembolic events was significantly associated with prolonged KCT. No other clinical feature showed significant association with any coagulation abnormality.

Cerebellar ataxia in systemic lupus erythematosus: three case reports.

Three patients presented with cerebellar ataxia among 350 cases of systemic lupus erythematosus (SLE) seen over the last 14 years. Cerebellar signs were unilateral in one and bilateral in the other two patients. Other neurological findings were present in all three patients. One initially presented with only cerebellar ataxia; other features of SLE appeared a few years later. Lupus anticoagulant test was positive in one patient. Corticosteroids given in the early stages appeared to benefit these patients by ameliorating cerebellar dysfunction.