Tasneem Fatma

Detection of biofilm formation among the clinical isolates of staphylococci: An evaluation of three different screening methods

PURPOSE The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. METHODS For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. RESULTS Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-positive phenotype under the optimized conditions in the TCP method and strains were further classified as high 22 (14.47 %) and moderate 60 (39.4 %) while in 70 (46.0 %) isolates weak or no biofilm was detected. Though TM correlated well with the TCP test for 18 (11.8 %) strongly biofilm producing strains, weak producers were difficult to discriminate from biofilm negative isolates. Screening on CRA does not correlate well with either of the two methods for detecting biofilm formation in staphylococci. CONCLUSION The TCP method was found to be most sensitive, accurate and reproducible screening method for detection of biofilm formation by staphylococci and has the advantage of being a quantitative model to study the adherence of staphylococci on biomedical devices.

Facile Algae-Derived Route to Biogenic Silver Nanoparticles: Synthesis, Antibacterial, and Photocatalytic Properties.

Biogenic synthesis of metal nanoparticles is of considerable interest, as it affords clean, biocompatible, nontoxic, and cost-effective fabrication. Driven by their ability to withstand variable extremes of environmental conditions, several microorganisms, notably bacteria and fungi, have been investigated in the never-ending search for optimal nanomaterial production platforms. Here, we present a hitherto unexplored algal platform featuring Chlorella pyrenoidosa, which offers a high degree of consistency in morphology of synthesized silver nanoparticles. Using a suite of characterization methods, we reveal the intrinsic crystallinity of the algae-derived nanoparticles and the functional moieties associated with its surface stabilization. Significantly, we demonstrate the antibacterial and photocatalytic properties of these silver nanoparticles and discuss the potential mechanisms that drive these critical processes. The blend of photocatalytic and antibacterial properties coupled with their intrinsic biocompatibility and eco-friendliness make these nanoparticles particularly attractive for wastewater treatment.

Biogenic Synthesis of Silver Nanoparticles Using Scenedesmus abundans and Evaluation of Their Antibacterial Activity

Silver nanoparticle (AgNP) was synthesized using the cell free extract of Scenedesmus abundans with AgNO3. The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and Photoluminescence. Bioreduction of Ag

Impact of environmental pollution on cyanobacterial proline content

This study describes the toxic effects of different prominent aquatic pollutants—heavy metals (Cd & Pb), pesticides (alphamethrin and deltamethrin) and salt (NaCl)—on the intracellular proline content in the cyanobacterium, Westiellopsis prolifica–Janet strain–NCCU331. Despite a reduction in growth (measured as chlorophyll a content), the intracellular proline content increased in the presence of heavy metals, pesticides and high salt concentration. The intracellular cyanobacterial proline accumulation was more pronounced under salt stress than in the presence of pesticides and heavy metals. We have also compared whether or not anionic components influence heavy metal toxicity. It was found that the chlorides of Cd and Pb were more toxic than the NO3 and the order of toxicity was CdCl2 > PbCl2 > Cd (NO3)2 > Pb (NO3)2. Among pyrethroids, deltamethrin was more toxic than alphamethrin.

Protection of Wheat Chloroplasts from Lipid Peroxidation and Loss of Photosynthetic Pigments by Quercetin under strong Illumination

Summary Exposure of chloroplasts to strong visible light in the presence of DCMU and paraquat resulted in lipid peroxidation and pigment photobleaching, which could be because of increased rates of production of active oxygen species. Quercetin and its glycoside, rutin, protected the chloroplasts from thylakoid lipid peroxidation and pigment photo-oxidation. These flavonoids more effectively protected the chloroplasts when the light treatment was given in the presence of DCMU as compared with that in the presence of paraquat. This differential protection by the flavonoids was investigated by inhibition of crocin photobleaching by quercetin and rutin, which showed that both of the flavonoids effectively quenched singlet oxygen (1O2 On the basis of our results, we suggest that singlet oxygen may be one of the predominant active species produced during strong illumination of chloroplasts, which may further be accelerated in the presence of DCMU. However, strong illumination in the presence of paraquat may lead to production of species such as superoxide and hydroxyl free radicals, which may damage the thylakoid membrane but may not be efficiently quenched by quercetin and rutin.

Cyanobacterial Polyhydroxybutyrate (PHB): Screening, Optimization and Characterization.

In modern life petroleum-based plastic has become indispensable due to its frequent use as an easily available and a low cost packaging and moulding material. However, its rapidly growing use is causing aquatic and terrestrial pollution. Under these circumstances, research and development for biodegradable plastic (bioplastics) is inevitable. Polyhydroxybutyrate (PHB), a type of microbial polyester that accumulates as a carbon/energy storage material in various microorganisms can be a good alternative. In this study, 23 cyanobacterial strains (15 heterocystous and 8 non-heterocystous) were screened for PHB production. The highest PHB (6.44% w/w of dry cells) was detected in Nostoc muscorum NCCU- 442 and the lowest in Spirulina platensis NCCU-S5 (0.51% w/w of dry cells), whereas no PHB was found in Cylindrospermum sp., Oscillatoria sp. and Plectonema sp. Presence of PHB granules in Nostoc muscorum NCCU- 442 was confirmed microscopically with Sudan black B and Nile red A staining. Pretreatment of biomass with methanol: acetone: water: dimethylformamide [40: 40: 18: 2 (MAD-I)] with 2 h magnetic bar stirring followed by 30 h continuous chloroform soxhlet extraction acted as optimal extraction conditions. Optimized physicochemical conditions viz. 7.5 pH, 30°C temperature, 10:14 h light:dark periods with 0.4% glucose (as additional carbon source), 1.0 gl-1 sodium chloride and phosphorus deficiency yielded 26.37% PHB on 7th day instead of 21st day. Using FTIR, 1H NMR and GC-MS, extracted polymer was identified as PHB. Thermal properties (melting temperature, decomposition temperatures etc.) of the extracted polymer were determined by TGA and DSC. Further, the polymer showed good tensile strength and young’s modulus with a low extension to break ratio comparable to petrochemical plastic. Biodegradability potential tested as weight loss percentage showed efficient degradation (24.58%) of PHB within 60 days by mixed microbial culture in comparison to petrochemical plastic.

Specific interaction of jacalin with phycocyanin, a fluorescent phycobiliprotein.

Recent research has shown that, like porphyrins, phycocyanin (PC) too can produce singlet oxygen upon excitation with the appropriate radiation and hence could be useful in photodynamic therapy (PDT) for cancer. Unlike porphyrins, PC has the advantage of being a non-toxic, non-carcinogenic, soluble protein. However, the challenge would be to target the fluorescent phycobiliprotein to malignant cells. We report here that the tumor-specific lectin, jacalin, binds PC specifically in a carbohydrate-independent manner and with affinities better than that for porphyrins. Hence the lectin could prove to be a useful carrier for targeted delivery of PC. The interaction involves both ionic and hydrophobic interactions and more than one contact site.

Spirulina: possible pharmacological evaluation for insulin-like protein

Diabetes mellitus is a metabolic disorder characterized by hyperglycemia, hyperlipidemia, hyperaminoacidemia, and hypoinsulinemia that leads to reduction in both insulin secretion and insulin action. Several natural products have been isolated and identified to restore the complications of diabetes. Spirulina is a naturally occurring freshwater cyanobacterium, enriched with proteins and essential nutrients. Treatment of diabetic rats with crude, aqueous extract, ethanolic extract, and insulin-like protein of Spirulina successfully ameliorated diabetic complications by increasing body weight and significantly decreasing the levels of blood glucose, glycosylated hemoglobin, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, alkaline phosphatase, total bilirubin, serum creatinine, serum uric acid, and blood urea nitrogen (p < 0.0001). Comparatively, the crude extract and insulin-like protein were found to be more effective than the aqueous and ethanolic extracts.

Heterogeneity of Alkane Chain Length in Freshwater and Marine Cyanobacteria

The potential utilization of cyanobacteria for the biological production of alkanes represents an exceptional system for the next generation of biofuels. Here, we analyzed a diverse group of freshwater and marine cyanobacterial isolates from Indian culture collections for their ability to produce both alkanes and alkenes. Among the 50 cyanobacterial isolates screened, 32 isolates; 14 freshwater and 18 marine isolates; produced predominantly alkanes. The GC-MS/MS profiles revealed a higher percentage of pentadecane and heptadecane production for marine and freshwater strains, respectively. Oscillatoria species were found to be the highest producers of alkanes. Among the freshwater isolates, Oscillatoria CCC305 produced the maximum alkane level with 0.43 μg/mg dry cell weight, while Oscillatoria formosa BDU30603 was the highest producer among the marine isolates with 0.13 μg/mg dry cell weight. Culturing these strains under different media compositions showed that the alkane chain length was not influenced by the growth medium but was rather an inherent property of the strains. Analysis of the cellular fatty acid content indicated the presence of predominantly C16 chain length fatty acids in marine strains, while the proportion of C18 chain length fatty acids increased in the majority of freshwater strains. These results correlated with alkane chain length specificity of marine and freshwater isolates indicating that alkane chain lengths may be primarily determined by the fatty acid synthesis pathway. Moreover, the phylogenetic analysis showed clustering of pentadecane-producing marine strains that was distinct from heptadecane-producing freshwater strains strongly suggesting a close association between alkane chain length and the cyanobacteria habitat.

Extracellular laccase production and its optimization from Arthrospira maxima catalyzed decolorization of synthetic dyes

In the present study laccase production potential of a photosynthetic, non nitrogen fixing cyanobacteria Arthrospira maxima (SAE-25780) was investigated for their probable use in synthetic dye decolorization which poses environmental pollution problem in aquatic bodies. A. maxima (SAE-25780) showed a constitutive production of laccase which increased up to 80% in the presence of inducer guaiacol. The optimal condition for laccase was 30 °C, 10 mM sucrose as a carbon source, 10 mM sodium nitrate as a nitrogen source, and 2 mM copper as metal activator. The partially purified laccase showed 84% and 49% decolorization potential for the two anthroquinonic dyes-Reactive Blue 4 and Remazol Brilliant Blue R, respectively (RBBR) within 96 h without any mediator. Therefore the laccase extracted from A. maxima (SAE-25780) can be used efficiently in bioremediation of synthetic dyes from paper, pulp and textile industries.