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Lead halide perovskite nanocrystal heterostructures have been extensively studied in the recent past for improving their photogenerated charge carriers mobility. However, most of such heterostructures are formed with random connections without having strong evidence of epitaxial relation. Perovskite-chalcohalides are the first in this category, where all-inorganic heterostructures are formed with epitaxial growth. Going beyond one facet, herein, different polyhedral nanocrystals of CsPbBr

Background: Viral diseases create one of the greatest challenges for the rapidly expanding ornamental fish culture sector. In recent years, the host-specific herpesviruses are receiving much attention due to the intensification in aquaculture globally. Cyprinid herpesvirus-2 (CyHV-2, goldfish hematopoietic necrosis virus), and Cyprinid herpesvirus-3 (CyHV-3, koi herpesvirus) are the lethal pathogens of koi carp Cyprinus carpio koi and goldfish Carassius auratus, respectively. In India, West Bengal is the leading state in ornamental fish production and export. Methods: The surveillance of CyHV-2 and CyHV-3 in koi carp and goldfish cultured in West Bengal was carried out between November 2014 and January 2017 as per Office International des Epizooties guidelines. Results: Both fish species were negative for CyHV-3. The CyHV-2 infection was detected in both gill and kidney tissues of apparently healthy and diseased C. auratus from December 2014 to March 2015. Severe necrosis was observed in the gills of infected C. auratus. Coinfection with members of the bacterial genera Aeromonas and Flavobacterium was also observed in the kidney of infected goldfish. The histopathological observations in the kidney of CyHV-2 infected C. auratus demonstrated the pathogenic potential of CyHV-2 and tissue tropism. Conclusions and Clinical relevance: Environmental stressors like low water temperature and the use of wastewater for culture played a vital role in the onset of CyHV-2 infection in the stressed goldfish. The spread of CyHV-2 can likely pose a certain degree of threat to aquaculture especially the unrestricted movement of goldfish. The results of the present study emphasize the necessity of an organized risk assessment to plan for the management strategies on the control and spread of CyHV-2 in Indian aquaculture.

Connecting nanocrystals with removal of interface ligand barriers is one of the key steps for efficient carrier transportation in optoelectronic device fabrication. Typically, ion migration for crystal deformation or connection with other nanocrystals needs a solvent as medium. However, on the contrary, this has been observed for CsPbBr3 perovskite nanocrystals in film where nanocrystals were swollen to get wider and fused with adjacent nanocrystals in self-assembly on film during solvent evaporation. Depending on precursor composition and exposed facets, again these connections could be programmed for tuning their connecting directions leading to different shapes. Aging further on solid substrate, these were also turned to continuous film of nanostructures eliminating all interparticle gaps on the film. This transformation could be ceased at any point of time, simply by heating or adding sufficient ligands. Analysis suggested that these unique and controlled connections were only observed with polyhedron shaped nanostructures with certain compositions and not with traditionally cubes. Details of this solid-surface transformation during solvent evaporation were analyzed, and an interparticle material transfer type mechanism was proposed. As these observations were not seen in chalcogenide and oxide nanocrystals and exclusively observed in perovskite nanocrystals, this would add new fundamentals to the insights of crystal growths of nanocrystals and would also help in obtaining films of connecting nanocrystals.

The excellent and extensive application of carbon dots (CDs) as drug delivery systems, bioimaging probes as well as in different optoelectronic devices with tunable emission properties influenced us to make a bridge between their drug delivery and light-emitting responses. In this scenario, we synthesized and purified CD from citric acid (CA) and urea using microwave method and thoroughly characterized them using several spectroscopic and microscopic techniques. The interesting pH dependence and pH reversibility of the synthesized CD system was studied. The loading of the anticancer drug doxorubicin hydrochloride (Dox) in CD generated white light (WL) when the pH of the solution changed from pH 12 to 2 and this WL system showed reversible “ON–OFF” photoswitching between pH 2 and 12. The probable mechanism of this WL generation was further explored to be fluorescence resonance energy transfer (FRET) between the respective components and consequently, for pH-dependent reversible photoswitching, the mechanism was established to be the pH responses of both CD and Dox. The WL system also retained its optical properties in the agarose gel matrix. Therefore, this study may open a new horizon in modelling a smart CD-based drug delivery system with interesting light-emitting properties, and thus can be applicable in constructing future drug delivery as well as light-emitting devices.

Aquaculture of tilapia is a new research venture in India. With intensification in farming practices, tilapia are increasingly susceptible to bacterial infections. This article describes the isolation and identification of pathogenic bacteria from cultured monosex Nile tilapia, Oreochromis niloticus (L.), that experienced moderate to severe mortalities in West Bengal, India between September and August 2014 and histopathological alterations in various organs. Gram-positive diplococci, identified as Streptococcus agalactiae with Streptococcus identification kits and 16S rDNA sequencing analysis, were isolated from the brain, operculum, and kidney. Other bacteria from the kidney were identified as Aeromonas sobria, A. caviae, Klebsiella pneumoniae ssp. pneumoniae, Escherichia coli, and Enterobacter cloacae. Staphylococcus epidermis was isolated from opercular hemorrhages. Histological sections of the infected tilapia brain revealed meningoencephalitis and granulomatous lesions. Sections from other organs indicated congestion, hemorrhagic and hyperplastic cells, necrosis, vacuolation, hemosiderin deposition, hypertrophic nuclei, melanomacrophage aggregation, and ruptured veins. This report is the first description of S. agalactiae as a primary pathogen causing meningoencephalitis in cultured tilapia in India. CORRESPONDING AUTHOR: H. Adikesavalu, S. Banerjee, A. Patra, T.J. Abraham [+] Department of Aquatic Animal Health, Faculty of Fishery Sciences, West Bengal University of Animal and Fishery Sciences, Chakgaria, Kolkata- 700094, West Bengal, India e-mail: abrahamtj1@gmail.com

The present study reports the first isolation of Chryseobacterium sp. and co-infection with Aeromonas hydrophila in pacu, Piaractus brachypomus fries cultured in West Bengal, India. The infected pacu fries showed white patches on gill, tail rot, skin discoloration, scale loss, skin peeling, emaciation, and kidney inflammation. The yellow pigmented colony from the kidney of pacu on selective cytophaga agar was identified as Chryseobacterium sp. based on colony pigmentation, cell morphology, phenotypic characterization, and 16S rDNA gene sequencing. Phylogenetically, the members of the genus Chryseobacterium clustered together as a separate clade and the strain PLI2 (NCBI accession number KP898212) branched with a non-type strain C. indologenes VIT-CMJ1 (accession number KJ437473 ) with high node value (100). Yet, the strain PLI2 was distinctly different from closely related type strain C. indologenes LMG 8337 (accession number LN681561) with 97% DNA homology and low (80) node value or other type strains of NCBI GenBank database. The challenge experiments indicated that Chryseobacterium sp. PLI2 can cause substantial mortalities (25%) in abraded and bath (2.2 × 107/mL) treated pacu fries. The kidney of challenged pacu became pale and inflamed. Most likely, this report is a new record on the isolation of Chryseobacterium sp. from the kidney of P. brachypomus. Statement of relevance • Co-infection of Chryseobacterium sp. and A. hydrophila in Piaractus brachypomus caused nephropathy and large scale mortalities. • The record of a new bacterial disease Chryseobacterium sp. infection in Indian aquaculture is a serious cause for concern.

“Gill rot” caused by the Gram negative, long, rod shaped bacterium Flavobacterium sp. in a sewage fed farm growing Indian major carps in West Bengal, India, is described. The phenotypic and molecular characteristics, virulence and pathology of Flavobacterium sp. strain KG3 are also documented. The infected catla Catla catla had cutaneous haemorrhages, white patches on body and gill, gill rot and excess mucus secretion. On selective cytophaga agar, the isolate produced non-rhizoid yellow pigmented colonies. Phylogenetically, the strain KG3 was distinctly different from the closely related type strains of Flavobacterium species, though it branched with type strain F. hydatis DSM 2063 (NCBI accession number AM230487 ) with low node value. Histologically, the naturally infected catla gills showed cartilaginous tissue inflammation, mucus secretion, necrosis of gill filament with associated reduction in the number of lamellae per filament, obliteration of interlamellar water channels, and fusion of lamellae. Catla catla fingerlings experienced about 57% moralities within 5 days of abrasion and immersion in a bath containing 4.7 × 106 Flavobacterium sp. cells/mL. The abraded and unchallenged fingerlings recorded 20% mortality in 3 days. These results demonstrated the virulence of Flavobacterium sp. in catla especially during the winter season, which warrants its management measures. Statement of relevance Flavobacterium spp. are emerging as major pathogens of Indian freshwater fish. They can cause chronic mortalities in fish at low water temperature. Correct diagnosis and understanding the pathology would help manage flavobacterial infection in fish.

Aquarium keeping is amongst the most popular hobbies with millions of enthusiast’s worldwide (Livengood and Chapman, 2011). Among ornamental fish, goldfish C. auratus is the most common and of international significance. A variety of diseases including bacterial diseases have been reported and characterized in gold fish (Citarasu et al., 2011). Among the bacterial diseases, flavobacteriosis is regarded as a predominant disease of ornamental fish (Moyer and Hunnicutt, 2007). Flavobacteriosis debilitates a wide ecological and phylogenetic spectrum of temperate and tropic freshwater fish (Loch and Faisal, 2015). Various commercially important fish species such as salmonids, eels, carps, goldfish, tilapia and channel catfish are also susceptible to this disease (Suomalainen et al., 2009). Flavobacteriosis in fish are caused by multiple bacterial species within the family Flavobacteriaceae and are responsible for devastating losses in wild and farmed fish stocks around the world (Loch and Faisal, 2015). Members of the genus Flavobacterium are Gram negative rods that range from 0.3 to 0.5 μm in diameter and from 1.0 to 40.0 μm in International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 5 Number 4(2016) pp. 39-46 Journal homepage: http://www.ijcmas.com

The present study attempted sequencing the 18S rRNA gene of Myxoboluscatmrigalae infecting the gill lamellae of carp, Cirrhinusmrigala and compared its genetic homology and phylogenetic characteristics with 18S rRNA genes of other Myxobolus spp. The infected fish had up to 3 small, creamy white plasmodia per gill filament with 30-50 spores each. The spore size was 17.90 ± 0.70 × 7.40 ± 0.40 μm. The sporoplasm contained two large nuclei of size 0.57 ± 0.09 μm and no iodinophilous vacuole. The DNA sequence of M.catmrigalae was clustered phylogenetically with other Myxobolus spp. infecting the gills of cyprinids available in GenBank, which showed 77-87 % homogeneity. On the phylogenetic tree, M.catmrigalae (KC933944) was clustered with M.pavlovskii (HM991164) infecting the gill lamellae of silver carp, Hypophthalmichthysmolitrix. The species most closely related to M.catmrigalae in GenBank was M.pavlovskii (AF507973) infecting the gill lamellae of big head carp, Aristichthysnobilis with 87 % homogeneity. This is the first report on molecular characterization of gill lamellae infecting M. catmrigalae.

Indian catfish production is increasing over the years so as the frequency of diseases. In this report, the isolation of Stenotrophomonas maltophilia from the kidney of Clarias gariepinus juvenile with distended abdomen along with its phenotypic, molecular and phylogenetic characteristics was described. The diseased catfish juveniles in an earthen pond (1500 m 3 ) with high stocking density (≈ 60 nos/m 3 ) had body discoloration, fin/tail rot, focal cutaneous hemorrhage, distended abdomen, inflammation of internal organs and visceral hemorrhage. The abdominal cavity was filled with transparent jelly-like mass. The bacterial strain isolated from the kidney of catfish formed a monophyletic group with other strains of S. maltophilia based on genotypic characters and phylogenetic analyses. The strain S. maltophilia SK1 (NCBI accession number KP898215) was alpha-hemolytic, protease and lipase positive and weakly pathogenic to C. gariepinus juveniles. It caused only 35 ± 5% mortality at a level of 1.40 × 10 7 cells/fish via intraperitonial injection. While the intramuscular injection caused only 10% mortality. The dead fish up on challenge had distended abdomen with jelly-like mass. Understanding the pathology and pathogenesis of this emerging pathogen in cultured catfish would help manage the disease. Statement of relevance 1 Stenotrophomonas maltophilia is considered as an opportunistic pathogen of human and fish. 2 This species is emerging as a pathogen in cultured catfish Clarias gariepinus (Burchell, 1822). 3 Understanding the pathology and pathogenesis of this species would help manage the disease.

A new bacterial disease (flectobacillosis) caused by Gram negative, long rod shaped Flectobacillus roseus in captive held carp, rohu (Labeo rohita) in West Bengal, India is described. Besides the phenotypic and molecular characterization, histopathology of F. roseus of naturally infected and challenged rohu were studied. The affected rohu had loss of mucus and scale, discoloured body, peeled skin and rotten tail, but no signs of gill damage. On selective cytophaga agar, F. roseus produced pink to rose pigmented colonies. Phylogenetically, F. roseus RF1 formed a monophyletic branch with F. roseusEU921645 (96% sequence similarity) and Flectobacillus sp. KC588923 (94% sequence similarity). It caused significant mortalities in rohu when challenged. The naturally infected rohu showed epithelial disruption, inflammation and necrosis of skeletal muscle tissue accompanied by haemocyte infiltration. The kidney of challenged rohu showed proximal and distal tubule degeneration, necrosis, thickening of epithelial layer of proximal and distal tubules, necrotised haematopoietic tissue, nephritic tubule with widened lumen, vacuolation of tubular epithelium, glomerular congestion, desquamation, glomerulopathy with dilated Bowman's space, cellular and nuclear hyperprophy, pycnotic nuclei, melano-macrophage aggregates and granuloma-like inflammatory response. These results suggest that F. roseus can produce systemic pathology in kidney similar to many other known fish pathogens.

Objective To study the association of Aeromonas salmonicida subsp. achromogenes in the haemorrhagic blister of cultured exotic carp Cyprinus carpio in West Bengal, India, its cellular fatty acid composition and antibiotic sensitivity. Methods The phenotypic characterization and antibiotic sensitivity of bacterial flora of diseased fish were performed. The whole cellular fatty acid composition of Aeromonas salmonicida ( A. salmonicida ) was determined by MIS Sherlock automatic identification system. Results Aeromonas hydrophila, A. salmonicida and Pseudomonas alcaligenes were isolated from the haemorrhagic blister. The fatty acid methyl esters pattern confirmed the A. salmonicida strain as A. salmonicida subsp. achromogenes . Unsaturated fatty acid 16:1 w7c/16:1 w6c (39.09%), saturated fatty acid 16:0 (26.84%) and the mono-unsaturated fatty acids 18:1 w7c (8.89%) and 16:1 iso I/14:0 3OH (8.49%) were the most common fatty acids, which accounted for 83.31% of the total fatty acids. A. salmonicida subsp. achromogenes was highly susceptible to broad spectrum antibiotics such as chloramphenicol, ciprofloxacin, co-trimoxazole, gentamycin, nitrofurantoin and oxytetracycline. Conclusions The finding on the presence of A. salmonicida in carps necessitates molecular level study on establishing the prevalence of this bacterium in Indian aquaculture systems especially on its free-living viable but non-culturable state.

As new pathogenic strains are emerging and threatening aquaculture development, myxosporeans (Myxozoa) are receiving much attention in recent years. Myxosporean taxonomy is traditionally based on morphology of the myxospore stage. Molecular data on Indian myxosporeans are rare. In this report, the 18S rRNA gene sequence of Myxobolus cuttacki infecting gill lamellae of minor carp Labeo bata (Ham.) and its phylogenetic relationship with other myxobolids are described for the first time. The plasmodia of M. cuttacki were 0.5-0.9 mm in size and whitish with a round to oval shape. The mean mature spore size was 16.10×7.05 μm. The 18S rRNA nucleotide sequence with 1703 bp of M. cuttacki (accession number KF465682) clustered phylogenetically with other Myxobolus spp. infecting cyprinid gills with 78-90% homogeneity. The gill lamellae infecting M. catmrigalae (KC933944) and M. orissae (KF448527) of Indian major carp Cirrhinus mrigala from India, exhibited 86% and 81% homogeneity with M. cuttacki, respectively. The infection rate was low to moderate on the gills which can have a negative impact on respiratory and physiological functions and subsequently on fish production.

Myxosporeans are best known for the diseases they cause in commercially important fish species. Identification of myxosporeans at the species-level is mainly based on conventional methods. The 18S rRNA gene sequence of morphologically identified Myxobolus orissae infecting the gill lamellae of mrigal carp Cirrhinus mrigala was characterized in the present study. The plasmodia of M. orissae were small, elongated and white to pale in colour. Phylogenetically, the 18S rDNA nucleotide sequence of M. orissae was clustered with other gill-infecting Myxobolus spp. of cyprinids. The species closely related to M. orissae was M. koi (FJ841887) infecting the gill lamellae of Cyprinus carpio with 96% similarity. The carp fin-infecting Thelohanellus caudatus (KC865607) from India exhibited only 78% DNA sequence similarity with M. orissae. Low level of M. orissae infection on gill caused thickening of epithelial cells surrounding the plasmodium. Under stressful conditions, it is likely that such infection can easily spread in confined fish and may cause serious disease outbreaks and economical losses.

This outbreak report details of a mortality event where Cyprinid herpes virus-2 (CyHV-2) was detected in association with multidrug-resistant Aeromonas hydrophila infection in goldfish, Carassius auratus, from commercial farms. The goldfish exhibited large scale haemorrhages on the body, fins and gills, lepidorthosis, necrosed gills, protruded anus and shrunken eyes. White nodular necrotic foci in spleen and kidneys were noticed, along with necrosis and fusion of gill lamellae. Transmission electron microscopy of affected tissues revealed the presence of mature virus particles. Involvement of CyHV-2 was confirmed by PCR, sequencing and observed cytopathic effect in koi carp fin cell line along with experimental infection study. A bacterium isolated from the internal organs of affected fish was found to be pathogenic Aeromonas hydrophila having resistance to more than 10 classes of antibiotics. We postulate that CyHV-2 was the primary etiological agent responsible for this outbreak with secondary infection by A. hydrophila. The experimental infection trials in Labeo rohita and koi carp by intraperitoneal challenge with CyHV-2 tissue homogenates failed to reproduce the disease in those co-cultured fish species. This is the first report of a viral disease outbreak in organised earthen ornamental fish farms in India and bears further investigation.

Aeromonas hydrophila isolated from fish (Labeo rohita), pond water, river water, raw meat of chicken and mutton and raw cow milk were characterized through Random Amplified Polymorphic DNA (RAPD) analysis and Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS PAGE) of cellular proteins. RAPD-PCR amplification of bacterial DNA was done by using ten random primers (OPA-01 to 10) and found some distinct banding pattern on agarose gel. RAPD profile was studied with each isolate and absolute polymorphism indicating its application as an ideal tool for molecular characterization. Other methods like morphological, serological and biochemical characterization gives contradictory results and total cellular protein profiling does not show any significant polymorphism for identification and discrimination.

This study describes rapid detection of Flavobacterium columnare induced columnaris disease in cultured freshwater fish, viz., Labeo rohita, Ctenopharyngodon idella, Puntius sp. and Anabas testudineus by species-specific polymerase chain reaction. Gill discolouration, yellow necrotic areas, white patches on gill, saddle back and erosion of scales were the prominent clinical signs in all diseased fish, except Puntius sp., which had typical signs of ulcer at the base of dorsal fin. Of the nine disease cases, eight were found columnaris positive through culture independent species-specific PCR. The two sets of F. columnare specific primers such as ColF, ColR and Col72F, Col1260R yielded amplicons of around 675 bp and 1000 bp, respectively in all positive samples. Phylogenetically, the nucleotide sequences of the positive samples namely, C1 and RG1 formed monophyletic group with F. columnare, thus confirmed the infection as columnaris.

The present study attempted sequencing the 18S rRNA gene of Myxobolus catmrigalae infecting the gill lamellae of carp, Cirrhinus mrigala and compared its genetic homology and phylogenetic characteristics with 18S rRNA genes of other Myxobolus spp. The infected fish had up to 3 small, creamy white plasmodia per gill filament with 30–50 spores each. The spore size was 17.90 ± 0.70 × 7.40 ± 0.40 μm. The sporoplasm contained two large nuclei of size 0.57 ± 0.09 μm and no iodinophilous vacuole. The DNA sequence of M. catmrigalae was clustered phylogenetically with other Myxobolus spp. infecting the gills of cyprinids available in GenBank, which showed 77–87 % homogeneity. On the phylogenetic tree, M. catmrigalae (KC933944) was clustered with M. pavlovskii (HM991164) infecting the gill lamellae of silver carp, Hypophthalmichthys molitrix. The species most closely related to M. catmrigalae in GenBank was M. pavlovskii (AF507973) infecting the gill lamellae of big head carp, Aristichthys nobilis with 87 % homogeneity. This is the first report on molecular characterization of gill lamellae infecting M. catmrigalae.

The supramolecular synthon namely primary ammonium dicarboxylate (PAD) synthon has been exploited to generate a new series of salt based low molecular weight gelators (LMWGs) derived from ferrocenedicarboxylic acid (FDCA) and primary amines Me–(CH2)n–NH2 (n = 3–15). While most of the salts are capable of forming gels with DMSO and DMF, nearly all of them show a tendency to form gels with at least one of the solvents studied. Structure property correlation based on single crystal and powder X-ray diffraction data in combination with optical-, scanning-, and transmission-electron microscopy reveals that the supramolecular synthon approach adopted herein for designing LMWGs is indeed useful and allows one to get an easy access to a new series of organometallic gelators.