Bacterial distribution in Twilight zone of the Indian sector of Southern Ocean: V3- V4 rDNA hypervariable region data.

Twilight zones in oceans represent the oceanic waters between 200 m to 1000 m in depth, wherein sunlight is diffused and intensity is <1% of surface value. The activities and diversity of marine micro-organisms in this unique zone are understudied, especially in the Indian Sector of the Southern Ocean. For a better understanding of the microbial environment and diversity in the twilight zone of the Indian sector of Southern Ocean, samples were collected from 200m depth in eddy-influenced waters of Subtropical Front (STF), Sub-Antarctic Front (SAF), Polar Front (PF), waters off Kerguelen (Kw), and Prydz Bay (Pb) waters. In this article, next-generation sequencing (NGS) based amplicon data of 16s rDNA bacterial samples are presented. Hypervariable V3-V4 regions were sequenced using Hiseq platform, and data was processed using Mothur v 1.48.0, and database Silva 138.1nr. Total of nine different phyla is reported from the Southern Ocean at 200m, whereas at order level Synechococcales was found in STF waters only and SAR 11_ Clades were present in all stations.

Bacterial distribution in the Equatorial Indian Ocean using Amplicon sequencing of V3-V4 rDNA hypervariable region data.

The Equatorial Indian Ocean (EIO) is a complex system strongly influenced by Indian Monsoon. During a RAMA (Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction) mooring maintenance expedition during the Southwest monsoon (August-September 2016) onboard ORV Sagar Kanya, seawater samples from the surface, deep chlorophyll maxima (DCM) and 200m were collected for bacterioplankton community structure. Herein we document our amplicon data of the bacterial community at 4 stations (4.01°S, 1.60°S, 0.36°N and 1.78°N) along the 67°00' E transect. The samples were subjected to next-generation sequencing (NGS), followed by processing with Mothur v 1.48.0, and the taxonomic classification prepared with Silva 138.1nr reference database. Our data indicates Alphaproteobacteria (48 %) and Cyanobacteria (33 %) dominance in the surface and DCM samples.

Mechanisms associated with the rapid decline in sea ice cover around a stranded ship in the Lazarev Sea, Antarctica.

In the satellite data era starting from 1979, the extent of Antarctic sea ice increased moderately for the first 37 years. However, the extent decreased to record low levels from 2016 to 2020, with the drop being greatest in the Weddell and Lazarev Seas of the Southern Ocean. An important question for the scientific fraternity and policymakers is to understand what ocean-atmospheric processes triggered such a rapid decline in sea ice. We employ in-situ, satellite, and atmospheric reanalysis data to examine the causative mechanism of anomalous sea ice variability in the Lazarev Sea at a time of ice growth in the annual cycle (March-April 2019), when a cargo ship was stuck in extensive ice cover and freed following the unusual decline in sea ice. High-resolution Sentinel-1 synthetic aperture radar captured a distinct view of the ship location and track within extensive ice cover of fast sea ice, dense pack ice, and icebergs in the Lazarev Sea on 27 March 2019. Subsequently, the sea ice cover declined and reached the fourth lowest extent in the entire satellite record during April 2019 which was 25.6% lower than the long-term mean value of 2.65 × 106 km2. We show that the anomalous sea ice variability was due to the occurrence of eastward-moving polar cyclones, including a quasi-stationary explosive development that impacted sea ice through extreme changes in ocean-atmospheric conditions. The cyclone-induced dynamic (poleward propagation of ocean waves and ice motion) and thermodynamic (heat and moisture plumes from midlatitudes, ocean mixed layer warming) processes coupled with high tides provided a conducive environment for an exceptional decline in sea ice over the region of ship movement.

Decadal changes in global phytoplankton compositions influenced by biogeochemical variables.

The global environmental changes owing to natural and anthropogenic influences are challenging the structure and functioning of the ocean ecosystem. The complex processes interacting within the physical, chemical, and biological environment at different spatio-temporal scales and their impact on the ocean ecosystem processes are yet to be investigated. A long term trend on phytoplankton biomass in terms of Chlorophyll-a concentration (Chl-a), phytoplankton compositions and the processes that control the variability is required for understanding the ocean ecosystem. This study investigated decadal trends (2002-2015) of phytoplankton composition and biogeochemical parameters over the Global Ocean (GO), Southern Ocean (SO), and the Arctic Ocean (AO) using ocean color remote sensing and assimilated data from the National Aeronautics and Space Administration (NASA) Ocean biogeochemical model. The results revealed the dominance of larger cell phytoplankton mainly diatoms throughout the SO and AO; however, the coccolithophores dominate in the remaining part of the GO. Analysis of nutrients showed that nitrate is not a limiting factor for the variability of phytoplankton biomass in the SO and AO. The low nitrate concentration influenced in the rest of the GO. The photosynthetically available radiation (PAR) limiting the phytoplankton biomass and composition in the SO and AO. Although the SO is known as the high nutrient low chlorophyll (HNLC) region of the GO, the low iron concentration along with the PAR co-limits the growth of phytoplankton biomass. Trend analysis showed that an increase in Chl-a and diatoms in the SO and AO. In contrast, it declined significantly in the other regions of the GO, in response to the consistent increase in sea surface temperature. The results indicated that, shifting of phytoplankton community from regional to global scale have a greater implication for climate change and marine ecosystem.

Molecular modeling piloted analysis for semicarbazone derivative of curcumin as a potent Abl-kinase inhibitor targeting colon cancer.

The human Abl kinases comprise a family of proteins that are known to be key stimulus drivers in the signaling pathways modulating cell growth, cell survival, cell adhesion, and apoptosis. Recent collative studies have indicated the role of activation of Abl and Abl-related genes in solid tumors; further terming the Abl kinases as molecular switches which promote proliferation, tumorigenesis, and metastasis. The up-regulated Abl-kinase expression in colorectal cancer (CRC) and the role of Abl tyrosine kinase activity in the Matrigel invasion of CRC cells have cemented its significance in CRC advancement. Therefore, the requisite of identifying small molecules which serve as Abl selective inhibitors and designing anti-Abl therapies, particularly for CRC tumors, has driven this study. Curcumin has been touted as an effective inhibitor of cancer cells; however, it is limited by its physicochemical inadequacies. Hence, we have studied the behavior of heterocyclic derivatives of curcumin via computational tools such as pharmacophore-based virtual screening, molecular docking, free-energy binding, and ADME profiling. The most actively docked molecule, 3,5-bis(4-hydroxy-3-methylstyryl)-1H-pyrazole-1-carboxamide, was comparatively evaluated against Curcumin via molecular dynamics simulation using Desmond, Schrödinger. The study exhibited the improved stability of the derivative as compared to Curcumin in the tested protein pocket and displayed the interaction bonds with the contacted key amino acids. To further establish the claim, the derivatives were synthesized via the mechanism of cyclization of Curcumin and screened in vitro using SRB assay against human CRC cell line, HCT 116. The active derivative indicated an IC50 value of 5.85 µM, which was sevenfold lower as compared to Curcumin's IC50 of 35.40 µM. Hence, the results base the potential role of the curcumin derivative in modulating Abl-kinase activity and in turn may have potential therapeutic value as a lead for CRC therapy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-03051-9.

Investigation of Black Carbon characteristics over southern ocean: Contribution of fossil fuel and biomass burning.

Black Carbon (BC) is an absorbing aerosol which has significant impact on the Earth - Atmosphere radiation balance and hence on climate. The variation of BC mass concentration and contribution of fossil fuel and biomass burning have been investigated over the Indian ocean sector of the Southern Ocean during austral summer. BC mass was in the range of 300-500 ng m-3 between 23.3oS to 24.5oS followed by decrease in BC to 150 ng m-3 as moving to higher southern latitudes till 41oS latitude. An increase in BC mass from 250 to 450 ng m-3 was found between 41 and 50oS due to trap of air masses by cyclonic wind and transport of aerosols from the southern part of African and eastern Madagascar regions. Higher BC concentration (250-350 ng m-3) was observed in the latitude range of 57-60oS which can be attributed to convergence of north-westerly and south-easterly winds. The dominant contributor to BC was fossil fuel, which was > 80% during half of the total observations, while > 20% biomass burning contributed to one fifth of observations. The coastal Antarctic region showed higher BC mass concentration with mixed type of contributions of biomass and fossil fuel. Such accumulation of BC near the Antarctic coast can have a crucial impact on the sea-ice albedo which significantly affect the Antarctic climate system locally and global climate in general.

Actinobacterial community structure in the Polar Frontal waters of the Southern Ocean of the Antarctica using Geographic Information System (GIS): A novel approach to study Ocean Microbiome.

Integration of microbiological data and geographical locations is necessary to understand the spatiotemporalpatterns of themicrobial diversity of an ecosystem. The Geographic Information System (GIS) to map and cataloguethe data ontheactinobacterial diversity of the Southern Ocean waterswas completed through sampling and analysis. Water samples collectedat two sampling stations viz.Polar Front 1(Station 1) andPolar Front 2(Station2)during7thIndian Scientific Expedition to the Indian Ocean Sector of the Southern Ocean (SOE-2012-13)were used for analysis. At the outset, two different genera of Actinobacteria were recorded at both sampling stations.Streptomyces was the dominantedwiththehigh score (> 60%), followed by Nocardiopsis (< 30%)at both the sampling stations-Polar Front 1 and Polar Front 2-along withother invasive genera such as Agrococcus, Arthrobacter, Cryobacterium, Curtobacterium,Microbacterium, Marisediminicola, Rhodococcus and Kocuria. This data will help to discriminate the diversity and distribution pattern of the Actinobacteria in the Polar Frontal Region of the Southern Ocean waters.Itis a novel approachusefulfor geospatial cataloguing of microbial diversityfromextreme nichesand in various environmental gradations.Furthermore,this research work will act as the milestone for bioprospecting of microbial communities and their products having potential applications in healthcare, agriculture and beneficial to mankind. Hence, this research work would have significance in creating a database on microbial communities of the Antarctic ecosystem.

Stable isotopes in water vapor and rainwater over Indian sector of Southern Ocean and estimation of fraction of recycled moisture.

Stable Hydrogen and Oxygen isotopic composition of water vapor, rainwater and surface seawater show a distinct trend across the latitude over the Southern Indian Ocean. Our observations on isotopic composition of surface seawater, water vapor and rainwater across a transect covering the tropical Indian Ocean to the regions of the Southern Ocean showed a strong latitudinal dependency; characterized by the zonal process of evaporation and precipitation. The sampling points were spread across diverse zones of SST, wind speed and rainfall regimes. The observed physical parameters such as sea surface temperature, wind speed and relative humidity over the oceanic regions were used in a box model calculation across the latitudes to predict the isotopic composition of water vapor under equilibrium and kinetic conditions, and compared with results from isotope enabled global spectral model. Further, we obtained the average fraction of recycled moisture across the oceanic transect latitudes as 13.4 ± 7.7%. The values of recycled fraction were maximum at the vicinity of the Inter Tropical Convergence Zone (ITCZ), while the minimum values were recorded over the region of subsidence and evaporation, at the Northern and Southern latitudes of the ITCZ. These estimates are consistent with the earlier reported recyling values.

Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean.

Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ(18)O and δ(13)C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75-200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ(18)O and δ(13)C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a 'vital effect' or a higher calcification rate. An interesting pattern of increase in the δ(13)C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ(13)C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.

Biological response to physical processes in the Indian Ocean sector of the Southern Ocean: a case study in the coastal and oceanic waters.

The spatial variation of chlorophyll a (Chl a) and factors influencing the high Chl a were studied during austral summer based on the physical and biogeochemical parameters collected near the coastal waters of Antarctica in 2010 and a zonal section along 60°S in 2011. In the coastal waters, high Chl a (>3 mg m(-3)) was observed near the upper layers (∼15 m) between 53°30'E and 54°30'E. A comparatively higher mesozooplankton biomass (53.33 ml 100 m(-3)) was also observed concordant with the elevated Chl a. Low saline water formed by melting of glacial ice and snow, as well as deep mixed-layer depth (60 m) due to strong wind (>11 ms(-1)) could be the dominant factors for this biological response. In the open ocean, moderately high surface Chl a was observed (>0.6 mg m(-3)) between 47°E and 50°E along with a Deep Chlorophyll Maximum of ∼1 mg m(-3) present at 30-40 m depth. Melt water advected from the Antarctic continent could be the prime reason for this high Chl a. The mesozooplankton biomass (22.76 ml 100 m(-3)) observed in the open ocean was comparatively lower than that in the coastal waters. Physical factors such as melting, advection of melt water from Antarctic continent, water masses and wind-induced vertical mixing may be the possible reasons that led to the increase in phytoplankton biomass (Chl a).

Redox signalling involving NADPH oxidase-derived reactive oxygen species.

Increased oxidative stress plays an important role in the pathophysiology of many diseases such as atherosclerosis, diabetes mellitus, myocardial infarction and heart failure. In addition to the well-known damaging effects of oxygen-free radicals, ROS (reactive oxygen species) also have signalling roles, acting as second messengers that modulate the activity of diverse intracellular signalling pathways and transcription factors, thereby inducing changes in cell phenotype. NADPH oxidases appear to be especially important sources of ROS involved in redox signalling. Seven NADPH oxidase isoforms, known as Noxs (NAPDH oxidases), are expressed in a cell- and tissue-specific fashion. These oxidases are thought to subserve distinct functions as a result of their tightly regulated activation (e.g. by neurohormonal and growth factors and mechanical stimuli) and their specific coupling with distinct downstream signalling pathways. In the present paper, we review the structure and mechanisms of activation of NADPH oxidases and consider their involvement in redox signalling, focusing mainly on the cardiovascular system.

An echocardiographic study of net atrioventricular compliance in juvenile and adult mitral stenosis.

BACKGROUND: Left atrial compliance is an important determinant of symptoms in mitral stenosis. About one-third of patients with mitral stenosis have reduced left ventricular compliance. We measured the net atrioventricular compliance in rheumatic mitral stenosis patients noninvasively and analyzed if there were any clinical, electrocardiographic, roentgenographic or echocardiographic correlates of net atrioventricular compliance. METHODS AND RESULTS: Seventy-six patients with mitral stenosis were analyzed and as many normal subjects were taken as control group. Patients were divided into two groups--those 20 years and below were grouped as juvenile mitral stenosis and those above 20 years as adult mitral stenosis patients. The net atrioventricular compliance in patients with mitral stenosis was significantly impaired compared to normal population. Mean compliance in juvenile group was 4.66+/-2.18 ml/mmHg (range 2.17-9.6) and in adult group it was 4.79+/-1.99 ml/mmHg (range 2.04-8.9) (p = ns). There was no difference in net atrioventricular compliance between the juvenile and adult patients with mitral stenosis. Mitral valve area showed an independent positive correlation with net atrioventricular compliance. CONCLUSIONS: The net atrioventricular compliance was significantly reduced in patients with rheumatic mitral stenosis; however, there was essentially no difference in the net atrioventricular compliance between the juvenile and adult patients with mitral stenosis. The net atrioventricular compliance may not be responsible for the more severe symptoms observed in juvenile mitral stenosis.

Interaction of fascin and protein kinase Calpha: a novel intersection in cell adhesion and motility.

Coordination of protrusive and contractile cell-matrix contacts is important for cell adhesion and migration, but the mechanisms involved are not well understood. We report an unexpected direct association between fascin, an actin-bundling component of filopodia, microspikes and lamellipodial ribs, and protein kinase Calpha (PKCalpha), a regulator of focal adhesions. The association is detectable by protein-protein binding in vitro, by coimmunoprecipitation from cell extracts, and in live cells as fluorescence resonance energy transfer detected by fluorescence imaging lifetime microscopy. The interaction is physiologically regulated by the extracellular matrix context of cells, depends on activation of PKCalpha and is mediated by the C1B domain of PKCalpha. Strikingly, a fascin mutant, fascin S39D, associates constitutively with PKCalpha. Through use of a newly developed set of membrane-permeable peptides that separately inhibit either fascin/PKCalpha or fascin/actin binding, we have uncovered that specific blockade of the fascin/PKCalpha interaction increases cell migration on fibronectin in conjunction with increased fascin protrusions and remodeling of focal adhesions. These results identify the fascin-PKCalpha interaction as an important novel intersection in the regulation and networking of cell-matrix contacts.

Fascins, and their roles in cell structure and function.

The fascins are a structurally unique and evolutionarily conserved group of actin cross-linking proteins. Fascins function in the organisation of two major forms of actin-based structures: dynamic, cortical cell protrusions and cytoplasmic microfilament bundles. The cortical structures, which include filopodia, spikes, lamellipodial ribs, oocyte microvilli and the dendrites of dendritic cells, have roles in cell-matrix adhesion, cell interactions and cell migration, whereas the cytoplasmic actin bundles appear to participate in cell architecture. We discuss the current understanding of the cellular mechanisms that regulate the binding of fascin to actin and how these processes contribute to the organisation or disassembly of cell protrusions. Although the in vivo roles of fascin have been studied principally in Drosophila, several human diseases are associated with inherited or acquired alterations in the expression of fascins. Strategies to modulate fascin-containing protrusions and thereby cell adhesive and migratory behaviour could have potential for therapeutic intervention in these conditions. The supplementary material referred to in this section can be found at http://www.interscience.wiley.com/jpages/0265-9247/suppmat/2002/v24.350.html

Modulation of alpha 5 beta 1 and alpha V beta 3 integrins on the cell surface during mitosis.

One of the hallmarks of cells undergoing mitotic division is their rounded morphology and reduced adhesion to the substratum. We have studied and compared the attachment of interphase and mitotic cells to substrata coated with fibronectin and vitronectin. We have found that adhesion of mitotic cells, as compared to interphase cells, is significantly reduced to fibronectin, but is higher to vitronectin. These results correlate well with the expression of alpha 5 beta 1 and alpha V beta 3 integrins, the respective receptors for fibronectin and vitronectin, on the cell surface. Mitotic cells show higher levels of alpha V beta 3 and very low levels of alpha 5 beta 1 proteins on the cell surface as compared to interphase cells. This difference in the levels of these integrins also reflects in the total amounts of fibronectin and vitronectin present on the cell surface of these cells. We have further shown, by flow cytometry, that binding of vitronectin, or the synthetic peptide -GRGDSP-, causes an increase in the intracellular levels of Ca2+ in mitotic cells, but no change is seen in the interphase cells. Binding of fibronectin to either of these cells fails to elicit any response. One interesting feature of our results is that the levels of total, i.e., cytoplasmic plus membrane bound, alpha 5 beta 1 and alpha V beta 3 integrins of mitotic and interphase cells remain the same, thus implying an alteration in the distribution of integrin chains between the plasma membrane and the cytoplasm during the conversion of interphase cells into the mitotic phase.

Isolation and characterization of laminin binding protein from regenerating rat liver plasma membrane.

Interaction of rat hepatocytes with laminin, the major basement membrane adhesive glycoprotein was studied. Rat fetal hepatocytes attached more to laminin than adult hepatocytes. Laminin promoted attachment of fetal hepatocytes in a concentration dependent manner and showed saturable binding pattern. Hepatocytes from CCl4 induced regenerating rat liver also attached more to laminin. The pentapeptide YIGSR derived from laminin promoted attachment of adult and fetal hepatocytes, but to a lesser extent. A 67 kDa protein was isolated from the hepatic plasma membrane of CCl4 induced regenerating rat liver by affinity chromatography over laminin sepharose. This protein appeared to be relatively abundant in regenerating liver than in normal liver. The radioiodinated 67 kDa protein could be inserted into liposomes and these liposomes attached to coverslips coated with laminin in a concentration dependent manner in a divalent cation free medium. Its specificity for laminin was also revealed by absence of significant binding to fibronectin and collagen.