Recent advances in the production, properties and applications of haloextremozymes protease and lipase from haloarchaea.

Proteases and lipases are significant groups of enzymes for commercialization at the global level. Earlier, the industries depended on mesophilic proteases and lipases, which remain nonfunctional under extreme conditions. The discovery of extremophilic microorganisms, especially those belonging to haloarchaea, paved a new reserve of industrially competent extremozymes. Haloarchaea or halophilic archaea are polyextremophiles of domain Archaea that grow at high salinity, elevated temperature, pH range (pH 6-12), and low aw. Interestingly, haloarchaeal proteolytic and lipolytic enzymes also perform their catalytic function in the presence of 4-5 M NaCl in vivo and in vitro. Also, they are of great interest to study due to their capacity to function and are active at elevated temperatures, tolerance to pH extremes, and in non-aqueous media. In recent years, advances have been achieved in various aspects of genomic/molecular expression methods involving homologous and heterologous processes for the overproduction of these extremozymes and their characterization from haloarchaea. A few protease and lipase extremozymes have been successfully expressed in prokaryotic systems, especially E.coli, and enzyme modification techniques have improved the catalytic properties of the recombinant enzymes. Further, in-silico methods are currently applied to elucidate the structural and functional features of salt-stable protease and lipase in haloarchaea. In this review, the production and purification methods, catalytic and biochemical properties and biotechnological applications of haloextremozymes proteases and lipases are summarized along with recent advancements in overproduction and characterization of these enzymes, concluding with the directions for further in-depth research on proteases and lipases from haloarchaea.

Characterization of Mn3 O4 -MnO2 nanocomposites biosynthesized by cell lysate of Haloferax alexandrinus GUSF-1.

Manganese oxide nanocomposites attract huge attention in various biotechnological fields due to their extensive catalytic properties. This study reports an easy, rapid, and cost-effective method of using the cell lysate of haloarchaeon, Haloferax alexandrinus GUSF-1 for the synthesis of manganese oxide nanoparticles. The reaction between the cell lysate and manganese sulfate resulted in the formation of a dark brown precipitate within 48 h at room temperature. The X-ray diffraction pattern showed the existence of Mn3 O4 and MnO2 phases consistent with the JCPDS card no. (01-075-1560 and 00-050-0866). The dark brown colloidal suspension of MnO3 -MnO2 in methanol showed maximum absorption between 220 and 260 nm. The EDX spectrum confirmed the presence of manganese and oxygen. The Transmission electron microscopy revealed the spherical morphology with an average particle size between 30 and 60 nm. The magnetic moment versus magnetic field (MH) curve, at room temperature (300 K) did not saturate even at a high magnetic field (±3T) indicating the paramagnetic nature of the prepared nanocomposite. The Atomic Emission Spectroscopic analysis showed a negligible amount of soluble manganese (0.03 ppm in 50 ppm) in the Mn3 O4 -MnO2 suspension suggesting the maximum stability of the material in the solvent over time. Interstingly, Mn3 O4 -MnO2 nanocomposites evidenced antimicrobial activity in the order of Pseudomonas aeruginosa > Salmonella typhi > Escherichia coli > Proteus vulgaris > Candida albicans > Staphylococcus aureus. Conclusively, this is the first report on the formation of Mn3 O4 -MnO2 nanocomposites using cell lysate of salt pan haloarcheon Haloferax alexandrinus GUSF-1 with antimicrobial potential.

Simultaneous purification and characterization of detergent-stable, solvent-tolerant haloextremozymes protease and lipase from Haloferax sp. strain GUBF 2.

Industrial important proteases and lipases are in increasing demand for various biotechnological applications. In the present study, the concomitantly produced protease and lipase by Haloferax sp. strain GUBF 2 were simultaneously purified as a heterogeneous lipase (45 and 66 kDa) and homogeneous protease (180 kDa); with 28.3 and 31.36 fold purity, respectively using Sephadex G-200. The aforementioned extremozymes were active at pH 3-13, 20-80 °C, 1-5 M NaCl, with optimal activity at pH 6, 70 °C, and 3 M NaCl, thus exhibiting attributes of true haloextremozymes. The Km and Vmax of purified lipase were 3.47 mM and 16.2 U/mL, while protease were 3.29 mg/mL and 28.5 U/mL, respectively. FTIR bands corresponding to the vibrations of amide II and amide III were detected in haloextremozymes which could perhaps be used to determine the secondary structure of the purified proteins. Furthermore, the activity of both enzymes was stimulated by Ca2+ and inhibited by 10 mM Hg2+ and phenylmethyl sulphonyl fluoride (PMSF). Additionally, these haloextremozymes are stable in the presence of detergent additives and organic solvents. In addition, purified protease displayed 74.3 ± 4.85% in-vitro blood clot dissolution activity. Conclusively this study revealed the key features, unusual properties, and possible biomedical applications of detergent-stable and organic solvent-tolerant haloextremozymes from Haloferax sp. strain GUBF 2 to date unexplored.

Isolation of Halomicroarcula pellucida strain GUMF5, an archaeon from the Dead Sea-Israel possessing cellulase.

A strain designated GUMF5 was isolated in Goa-India from sediments of Dead Sea-Israel  and identified as haloarchaeon Halomicroarcula pellucida based on 16S rRNA gene analysis similarity value of 99.84%. Strain GUMF5 grew on mineral salts medium with 20% NaCl and 0.5% carboxymethyl cellulose-sodium (CMC-Na) as a sole source of carbon and produced haloextremozyme cellulase. The enzyme was concentrated using Sephadex G20, precipitated with ethanol, dialyzed and retentate purified using Sephadex G200, the size exclusion chromatography. A yield of 78.53% cellulase with an activity of 131.13 U/mg and 1.24-fold purity was obtained. The purified cellulase had optimum activity at 20% NaCl, at 40 ºC, 0.5% CMC-Na, pH 7 and 150 rpm. SDS-PAGE combined with zymographic analysis revealed the molecular weight of cellulase as 240 kDa, 40 kDa and 17.4 kDa. The activity of the enzyme was stimulated by metallic cations in the order of Ca+2 > Mn+2 > Mg+2 > SO4 2- > NH4 + and was inhibited by Ag+ > Fe+2 > Cu+2. Methanol and ethanol enhanced the cellulase activity by 6% and 26%, respectively. The haloextremozyme cellulase degraded Whatman No. 1 filter paper indicated in scanning electron micrographs, exposure of open pores and fibers without any intra connectivity corresponding to paperase activity and implicating the possible use of enzyme to bio-convert cellulosic waste. Conclusively, Halomicroarcula pellucida GUMF5 (Accession number: MH244431), globally, is the only Halomicroarcula pellucida isolated from the sediments of Dead Sea producing haloextremozyme cellulase, and hence is an important biotechnological resource.

Conversion of selenite by Haloferax alexandrinus GUSF-1 (KF796625) to pentagonal selenium nanoforms which in vitro modulates the formation of calcium oxalate crystals.

AIM: To investigate the ability of Haloferax alexandrinus GUSF-1 (KF796625) to biosynthesize non-toxic elemental selenium (Se0 ) and check their capacity in in vitro crystal structure modulation of calcium oxalate, which are implicated in the development of renal calculi. METHODS AND RESULTS: Haloferax alexandrinus GUSF-1 (KF796625) during growth in the presence of 5 mmol L-1 of selenite formed insoluble brick-red particles. Se0 formed was monitored spectrophotometrically using a combination of two assays; the ascorbic acid reduction and sodium sulphide solubilization assay. After 168 h of growth, 2.89 mmol L-1 of Se0 was formed from 4.9 mmol L-1 of selenite. Absorption bands at 1.5, 11.2 and 12.5 keV in EDX spectroscopy confirmed that the brick-red particulate matter was Se0 . Furthermore, these selenium nanoparticles (SeNPs) were pentagonal in shape in transmission electron microscopy imaging. The peak positions in X-ray diffractogram at 2θ values of 23.40°, 29.66°, 41.26°, 43.68°, 45.24°, 51.62°, 55.93° and 61.47° and the relative intensities further confirmed the formation of Se0 . In vitro addition of 50 and 100 µg ml-1 of these SeNPs to the mixture of sodium chloride, calcium chloride and sodium oxalate affected and modulated the shape and size of rectangular-shaped calcium oxalate crystals (average area of 1.23 ± 0.2 µm2 ) to smaller rectangular-shaped crystals (average area of 0.54 ± 0.2 µm2 ) and spherical-shaped crystals (average area 0.13 ± 0.005 µm2 ). CONCLUSION: Haloferax alexandrinus GUSF-1 (KF796625) transformed selenite to Se0 pentagonal nanoforms that modulated in vitro the formation of crystal shape and size of calcium oxalate. SIGNIFICANCE AND IMPACT OF STUDY: There are no reports on conversion of selenite to Se0 among the Haloferax genera, and this study involving the formation of pentagonal SeNPs with capacity to modulate the formation of calcium oxalate crystals in haloarchaea is recorded as the first report and of significance in pharmaceutical research related to formulations abetting urinary calculi.

Foot drop - an uncommon presentation of FOLFOX toxicity

A quimioterapia com FOLFOX (oxaliplatina, leucovorina e 5-fluorouracilo) é frequentemente utilizada em doentes com cancro colorretal. Os sais de platina são conhecidos por serem uma classe de quimioterápicos que comumente induzem neurotoxicidade periférica. Na toxicidade induzida pela oxaliplatina, os sintomas sensitivos são os mais frequentes. Neste artigo, apresentamos dois casos clínicos de pacientes com adenocarcinoma de cólon, ambos submetidos à quimioterapia com FOLFOX4, e que desenvolveram neurotoxicidade incomum, apresentando pé pendente após o terceiro ciclo de tratamento. Esta manifestação clínica pode ser explicada por dano axonal nos neurônios motores periféricos do nervo peroneal comum (fibular), que fornece inervação motora aos músculos do pé. A paralisia do nervo fibular causa fraqueza súbita nos músculos do pé, que parece ser temporária. Ambos os doentes recuperaram completamente do evento sem necessidade de ajustes no tratamento, nem introdução de medicamentos diferentes. A apresentação de pé pendente como toxicidade da quimioterapia ainda é pouco compreendida. Os casos relatados mostram o pé pendente como uma manifestação grave e incomum de neuropatia induzida por FOLFOX, que pode ser transitória, e não requer necessariamente intervenção específica.

Chemotherapy based on FOLFOX (oxaliplatin, leucovorin, and 5-fluorouracil) regimen is frequently used in colorectal cancer patients. Oxaliplatin and other platinum agents are known to be a class of chemotherapy drugs that commonly induce peripheral neurotoxicity. The most frequent oxaliplatin related neurotoxicity is sensitive symptoms. Here, we present two cases of patients with colon adenocarcinoma, both undergoing chemotherapy with FOLFOX4, who developed uncommon neurotoxicity, presenting with foot drop after the third treatment cycle. Foot drop may be explained by axonal damage of peripheral motor neurons of the common peroneal (fibular) nerve, which provides motor innervation to the foot muscles. Peroneal nerve palsy causes sudden weakness in the muscles of the foot that seems to be temporary. Both patients completely recovered from the event. There was no need for treatment adjustments, neither introduction of different drugs. Foot drop as chemotherapy toxicity is still poorly understood. The reported cases show foot drop as a severe and uncommon manifestation of FOLFOX-induced neuropathy, that might be transitory, and does not necessarily requires specific intervention.

Anti-Pseudomonas aeruginosa biofilm activity of tellurium nanorods biosynthesized by cell lysate of Haloferax alexandrinus GUSF-1(KF796625).

Pseudomonas aeruginosa, an opportunistic human pathogen, is a major health concern as it grows as a biofilm and evades the host's immune defenses. Formation of biofilms on catheter and endotracheal tubes demands the development of biofilm-preventive (anti-biofilm) approaches and evaluation of nanomaterials as alternatives to antibiotics. The present study reports the successful biosynthesis of tellurium nanorods using cell lysate of Haloferax alexandrinus GUSF-1 (KF796625). The black particulate matter had absorption bands at 0.5 and 3.6 keV suggestive of elemental tellurium; showed x-ray diffraction peaks at 2θ values 24.50°, 28.74°, 38.99°, 43.13°, 50.23° and displayed a crystallite size of 36.99 nm. The black nanorods of tellurium were an average size of 40 nm × 7 nm, as observed in transmission electron microscopy. To our knowledge, the use of cell lysate of Haloferax alexandrinus GUSF-1 (KF796625) as a green route for the biosynthesis of tellurium nanorods with a Pseudomonas aeruginosa biofilm inhibiting capacity is novel to haloarchaea. At 50 µg mL-1, these tellurium nanorods exhibited 75.03% in-vitro reduction of biofilms of Pseudomonas aeruginosa ATCC 9027, comparable to that of ciprofloxacin, which is used in treatment of Pseudomonas infections. Further, the observed ability of these nanoparticles to inhibit the formation of Pseudomonas biofilms is worthy of future research perusal.

Characterization of multicomponent antioxidants from Haloferax alexandrinus GUSF-1 (KF796625).

The present study was aimed to exploit the haloarchaeon Haloferax alexandrinus GUSF-1 (KF796625) for the presence of biomolecules possessing antioxidant activity. The culture produced a bright orange pigment when grown aerobically in nutrient rich medium with 25% crude solar salt. Biomolecules from cell-free supernatant and from the cells of the culture were individually extracted through the assistance of solvents of different polarities, such as ethanol, methanol and hexane, and monitored for scavenging of stable free radicals. Each of the extracts showed varying capacities to scavenge DPPH•(20, 31, and 80% DPPH• RSA; 160.19, 248.29 and 640.76 AAE µg g-1 of cells) at 1 mg mL-1. The extracellular ethanolic extract was polysaccharide in nature, equivalent to 47 µg mL-1 of glucose when assayed with the phenol-sulfuric acid method. The Fourier Transform-Infra Red spectroscopy confirmed the characteristic glycosidic peaks between 2000 and 1000 cm-1. Similarly, the glycerol diether moiety separated from hydroxylated methanolysates through thin-layer chromatography scavenged free radicals (10.47% DPPH• RSA; 80.03 AAE µg g-1 of cells). Further, the hexanolic extract exhibited spectral characteristics of red carotenoids and resolved into distinct compounds when separated by thin-layer chromatography using different developing systems. All separated compounds were positive for the DPPH• reaction (13-30% DPPH• RSA; 100-240 AAE µg g-1). Chemical profiling of the hexanolic extract using the high resolution-liquid chromatography-mass spectroscopy-diode array detector analysis confirmed the presence of different carbon length isoprenoids; C30: tetrahydrosqualene, C40: 3-hydroxyechinenone, astaxanthin, canthaxanthin, lycopene, phytofluene, phytoene and C50: bisanhydrobacterioruberin, monoanhydrobacterioruberin, bacterioruberin and haloxanthin. Thus, we conclude that the synergistic actions of all these components contribute to the antioxidant activity of the culture and that the antioxidant activity of the exopolysaccharide, glycerol dither moiety, tetrahydrosqualene, haloxanthin and 3-hydroxyechinenone is recorded as the first report for Haloferax alexandrinus GUSF-1 (KF796625). Therefore, recommended for use in microbial industrial biotechnology. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-020-02584-9.

Characterization of Extracellular Protease from the Haloarcheon Halococcus sp. Strain GUGFAWS-3 (MF425611).

Halococcus agarilyticus GUGFAWS-3 (MF425611) was isolated from a marine white sponge of Haliclona sp., inhabiting the rocks in the intertidal region of Anjuna, Goa, India. Uniquely, the microbe simultaneously produces two halo-extremozymes in 25% NaCl, namely protease and lipase at 49.5 ± 0.4 and 3.67 ± 0.02 (U mL-1), respectively. The protease is constitutively produced in starch mineral salts medium with consistent 4 ± 1.0 mm zone of enzyme production, regardless of the non-availability of protein as substrate. The ethanol precipitated enzyme on dialysis and Sephadex G-200 gel filtration chromatography was partially purified to 12.26-fold and was active between 20 and 80 °C, 0-5 M NaCl, and pH 3-13. Optimum activity, however, was at 70 °C, 3 M NaCl, and pH 7. The enzyme was thermo stable at 70 °C with 50.26 ± 2.40% of relative enzyme activity at 75 min. Furthermore, it was stable in the presence of polar and non-polar organic solvents, detergents, and hydrocarbons. Several metal cations enhanced its activity in the order of Ca2+ > Ni2+ > Fe3+ > Co2+ > Mg2+ > Cu2+ > Mn2+. Dependence of enzyme on cysteine; serine, and metal ions was confirmed by ß-mercaptoethanol; PMSF and EDTA, respectively which induced its partial inhibition. Additionally, protease inhibited in vitro biofilm formation in Staphylococcus aureus. Conclusively, the production of a neutral halo-thermophilic protease is reported for the first time in the genus Halococcus.

Review of PD-1/PD-L1 Inhibitors in Metastatic dMMR/MSI-H Colorectal Cancer.

There are a wide range of therapies for metastatic colorectal cancer (CRC) available, but outcomes remain suboptimal. Learning the role of the immune system in cancer development and progression led to advances in the treatment over the last decade. While the field is rapidly evolving, PD-1, and PD-L1 inhibitors have a leading role amongst immunomodulatory agents. They act against pathways involved in adaptive immune suppression resulting in immune checkpoint blockade. Immunotherapy has been slow to impact the management of this patient population due to disappointing results, mainly when used broadly. Nevertheless, some patients with microsatellite-instability-high (MSI-H) or mismatch repair-deficient (dMMR) CRC appear to be susceptible to checkpoint inhibitors with objective and sustained clinical responses, providing a new therapeutic option for patients with advanced disease. This article provides a comprehensive review of the early and late phase trials with the updated data of PD-1/PD-L1 inhibitors alone or in combination with other therapies (immunotherapy, targeted therapy and chemotherapy). While data is still limited, many ongoing trials are underway, testing the efficacy of these agents in CRC. Current and future challenges of PD-1 and PD-L1 inhibitors are also discussed.

Haloferax sulfurifontis GUMFAZ2 producing xylanase-free cellulase retrieved from Haliclona sp. inhabiting rocky shore of Anjuna, Goa-India.

Salt stable cellulases are implicated in detritic food webs of marine invertebrates for their role in the degradation of cellulosic material. A haloarchaeon, Haloferax sulfurifontis GUMFAZ2 producing cellulase was successfully isolated from marine Haliclona sp., a sponge inhabiting the rocky intertidal region of Anjuna, Goa. The culture produced extracellular xylanase-free cellulase with a maximum activity of 11.7 U/ml, using carboxymethylcellulose-Na (CMC-Na), as a sole source of carbon in 3.5 M NaCl containing medium, pH 7 at 40°C and produced cellobiose and glucose, detectable by thin-layer chromatography. Nondenaturing polyacrylamide gel electrophoresis of the crude enzyme, revealed a single protein band of 19.6 kDa which on zymographic analysis exhibited cellulase activity while corresponding sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a molecular weight of 46 kDa. Unlike conventional cellulases, this enzyme is active in presence of 5 M NaCl and does not have accompanying xylanase activity, hence can be considered as xylanase-free cellulase. Such enzymes from haloarchaea offer great potential for biotechnological application because of their stability at high salinity and is therefore worth pursuing.

Leiomyosarcoma of the Inferior Vena Cava: A Case Report of Complete and Sustained Response with Trabectedin.

Inferior vena cava leiomyosarcoma is a very rare tumor, accounting for only 0.5% of all soft tissue sarcomas. As the other leyomiosarcomas of vascular origin, they have a poor prognosis, and radical resection with surgical margins free of tumor is the only potentially curative treatment. We present a case of a 46 year-old woman with metastatic inferior vena cava leiomyosarcoma who progressed after anthracyclines and ifosfamide and achieved a complete and sustained response with trabectedin. Beyond progression, the patient started third line treatment with pazopanib. A brief review of literature is also given. This case supports the efectiveness of a recent therapeutic agent, with an impressive progression-free survival in a recurrent metastatic inferior vena cava leiomyosarcoma.

O leiomiossarcoma da veia cava inferior é um tumor raro, constituindo apenas 0,5% dos sarcomas de tecidos moles. À semelhança de outros leiomiossarcomas de origem vascular, estão associados a um mau prognóstico, sendo a ressecção com margens livres de tumor o único tratamento potencialmente curativo. Apresentamos um caso de uma doente de 46 anos com um leiomiossarcoma metastizado, refratário a antraciclinas e ifosfamida, e com resposta completa e prolongada sob trabectedina. Após progressão, a doente iniciou terapêutica de terceira linha com pazopanib. Será feita uma breve revisão da literatura. Este caso suporta a eficácia de uma terapêutica recente, demonstrando uma sobrevivência livre de progressão atípica num leiomiossarcoma metastático e refratário.

Evaluation of antioxidant producing potential of halophilic bacterial bionts from marine invertebrates.

Marine invertebrates exposed to high levels of reactive oxygen species in the oceans have been reported to produce antioxidants as a major defense against free radical mediated toxicity; protecting their tissues from the damage associated with the oxidative stress. In view of this, the present study was carried out to determine the antioxidant activity of 100 bacterial bionts isolated from marine sponges, corals and a single bivalve. Methanol extract of biont GUVFCFM-3 produced 67.83% scavenging of 2,2-diphenyl-2-picrylhydrazyl free radicals and 65.87% scavenging of superoxide free radicals. Preliminary tests leading to the identification of the extracellular antioxidant factor produced by GUVFCFM-3 revealed that it is a peptide. We report that the genera Chromohalobacter sp. primarily known for its unique salt tolerating abilities by virtue of the production of osmolytes is an excellent scavenger of free radicals.

Purification and molecular and biological characterisation of the 1-hydroxyphenazine, produced by an environmental strain of Pseudomonas aeruginosa.

Pseudomonas aeruginosa--an opportunistic pathogen, perhaps best known for chronic lung infections, produces wide range of pigments that possess specific activities which either assist the organism's survival or bring about changes within host. A similar blue-green diffusible pigment producing P. aeruginosa was isolated from dug-well water, so as to extract 1-hydroxyphenazine from its crude pigment. The compound was purified from the crude pigment using column chromatography followed by a preparative thin layer chromatography that showed a single yellow spot. Further molecular characterisation of the purified component was carried out using UV-Vis spectrophotometer, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and mass spectroscopy which showed respective peaks corresponding to 1-hydroxyphenazine. Biological characterisation using in vitro assays revealed that 1-hydroxyphenazine showed anti-bacterial activity only against Bacillus sp. and a concentration of 30 µg/ml induced noticeable morphological alteration in A549 human lung adenocarcinoma cells followed by cell death after 48 h. Thus, such active components within bacterial pigments can be characterized and used as possible anti-bacterial or anti-cancer agents.

Culturable bacterial flora associated with the dinoflagellate green Noctiluca miliaris during active and declining bloom phases in the Northern Arabian Sea.

A massive algal bloom of the dinoflagellate Noctiluca miliaris (green) was located in the Northern Arabian Sea by IRS-P4-2 (OCM-II) for microbiological studies, during two consecutive cruises of February-March 2009. Culturable bacterial load during bloom were ≈ 2-3-fold higher in comparison to non-bloom waters and ranged from 3.20 × 10(5) to 6.84 × 10(5) cfu ml(-1). An analysis of the dominant heterotrophs associated with Noctiluca bloom resulted in phylogenetic and a detailed metabolic characterization of 70 bacterial isolates from an overlapping active and declining bloom phase location near north-central Arabian Sea. The active phase flora was dominated by Gram-positive forms (70.59 %), a majority of which belonged to Bacillus (35.29 %) of Firmicutes. As the bloom declined, Gram-negative forms (61.11 %) emerged dominant, and these belonged to a diverse γ-proteobacterial population consisting of Shewanella (16.67 %) and equal fractions of a Cobetia-Pseudomonas-Psychrobacter-Halomonas population (36.11 %). A Unifrac-based principal coordinate analysis of partial 16S rDNA sequences showed significant differences among the active and declining phase flora and also with reported endocytic flora of Noctiluca (red). A nonparametric multidimensional scaling (NMDS) of antibiogram helped differentiation among closely related strains. The organic matter synthesized by N. miliaris appears to be quickly utilized and remineralized as seen from the high efficiency of isolates to metabolize various complex and simple C/N substrates such as carbohydrates, proteins/amino acids, lipids, sulfide production from organic matter, and solubilize phosphates. The ability of a large fraction of these strains (50-41.67 %) to further aerobically denitrify indicates their potential for nitrogen removal from these high-organic microniches of the Noctiluca bloom in the Arabian Sea, also known for high denitrification activity. The results indicate that culturable euphotic bacterial associates of Noctiluca are likely to play a critical role in the biogeochemical ramifications of these unique seasonally emerging tropical open-water blooms of the Northern Arabian Sea.

Antibacterial activity of halophilic bacterial bionts from marine invertebrates of mandapam-India.

Marine ecosystem and its organisms, particularly the invertebrates are recent targets of bioprospecting and mining for a large group of structurally unique natural products encompassing a wide variety of chemical classes such as terpenes, polyketides, acetogenins, peptides and alkaloids of varying structures, having pronounced pharmacological activities. In view of the limited reports on the antibacterials produced by bacteria, isolated from marine sponges, corals and bivalves of Indian origin, the present study is aimed at investigating the antagonistic activities of 100 heterotrophic, halophilic bacterial bionts isolated from 9 sponges, 5 corals and one bivalve. Culture broths of 46 of these bionts were active against human pathogenic bacteria namely Staphylococcus citreus, Proteus vulgaris, Serratio marcesans, Salmonella typhi, Aerobacter aerogenes and Escherichia coli. Further, the ethyl acetate extracts of cell free supernatant confirmed the presence of extracellular bioactive factor, by agar cup diffusion method. Interestingly, highest number of bionts having activity was isolated from corals followed by sponges and bivalve. The study clearly demonstrates that bacterial bionts of marine invertebrates are a rich source of bioactive secondary metabolites against human bacterial pathogens.