Synthesis of highly water-soluble fluorescent conjugated glycopoly(p-phenylene)s for lectin and Escherichia coli

Two facile, convenient, and versatile synthetic approaches are used to covalently attach carbohydrate residues to conjugated poly(p-phenylene)s (PPPs) for highly water-soluble PPPs bearing alpha-mannopyranosyl and beta-glucopyranosyl pendants (polymers A and B), which highly fluoresce in phosphate buffer (pH 7.0). The post-polymerization functionalization approach is to treat bromo-bearing PPP (polymer 1) with 1-thiolethyl-alpha-D-mannose tetraacetate or 1-thiol-beta-D-glucose tetraacetate in THF solution in the presence of K(2)CO(3) at room temperature through formation of thioether bridges, affording polymer 2a or 2b. The prepolymerization functionalization approach is to polymerize a well-defined sugar-carrying monomer, affording polymer 2a. Polymers 2a and 2b were deacetylated under Zemplén conditions in methanol and methylene chloride containing sodium methoxide, affording polymers A and B, respectively. The multivalent display of carbohydrates on the fluorescent conjugated glycopolymer overcomes the characteristic low binding affinity of the individual carbohydrates to their receptor proteins. Titration of concanavalin A (Con A) to alpha-mannose-bearing polymer A resulted in significant fluorescent quenching of the polymer with Stern-Volmer quenching constant of 4.5 x 10(7). Incubation of polymer A with Escherichia coli (E. coli) lead to formation of fluorescently stained bacterial clusters. Beta-glucose-bearing polymer B displayed no response to Con A and E. coli.     

Sociobiology of biodegradation and the role of predatory protozoa in biodegrading communities

Predatory protozoa are known to enhance biodegradation by bacteria in a variety of systems including rumen. This is apparently counterintuitive since many protozoa do not themselves produce extracellular degradative enzymes and prey upon bacterial degraders. We propose a mechanism of protozoal enhancement of bacterial biodegradation based on the sociobiology of biodegradation. Since extracellular enzyme production by degraders involves a cost to the bacterial cell, cheaters that do not make the enzyme will have a selective advantage. In the presence of cheaters, degraders that physically attach to water-insoluble substrate will have a selective advantage over free-floating degraders. On the other hand, cheaters will benefit by being free floaters since they consume the solubilized products of extracellular enzymes. Predatory ciliated protozoa are more likely to consume free-floating cheaters. Thus, due to protozoan predation a control is exerted on the cheater population. We illustrate the dynamics of such a system with the help of a computer simulation model. Available data on rumen and other biodegradation systems involving protozoa are compatible with the assumptions and predictions of the model.     

Testing the efficacy of hyperspectral (AVIRIS-NG), multispectral (Sentinel-2) and radar (Sentinel-1) remote sensing images to detect native and invasive non-native trees

Biological Invasions - Invasive alien species threaten tropical grasslands and native biodiversity across the globe, including in the natural mosaic of native grasslands and forests in the Shola...     

How many antibiotics are produced by the genus Streptomyces?

Streptomyces is the largest antibiotic-producing genus in the microbial world discovered so far. The number of antimicrobial compounds reported from the species of this genus per year increased almost exponentially for about two decades, followed by a steady rise to reach a peak in the 1970s, and with a substantial decline in the late 1980s and 1990s. The cumulative number shows a sigmoid curve that is much flatter than what a logistic equation would predict. We attempted to fit a mathematical model to this curve in order to estimate the number of undiscovered antimicrobials from this genus as well as to predict the trends in the near future. A model assuming that the screening efforts are encouraged by a previous year's success and that the probability of finding a new antibiotic is a function of the fraction of antibiotics undiscovered so far offered a good fit after optimizing parameters. The model estimated the total number of antimicrobial compounds that this genus is capable of producing to be of the order of a 100,000 - a tiny fraction of which has been unearthed so far. The decline in the slope appeared to be due to a decline in screening efforts rather than an exhaustion of compounds. Left to itself, the slope will become zero in the next one or two decades, but if the screening efforts are maintained constant, the rate of discovery of new compounds will not decline for several decades to come.     

Molecular analyses of methanogen diversity associated with cattle dung

Methanogen communities were characterized in cattle dung of different ages by using a culture-independent approach. Community structures were determined by the phylogenetic analyses of methyl-coenzyme M reductase A (mcrA) clones of fresh, 8-month-old, and 24-month-old-dry dung samples. The clones in the mcrA libraries of fresh and 8-month old dung samples were identified as belonging to Methanomicrobiales, Methanobacteriales, and Methanosarcinales. However, clones in the library of 24-month-old dung were not affiliated to Methanomicrobiales. Anaerobic digestion of 2-month-old dung produced only 15% less methane compared to fresh dung which indicated the possibility of using dry dung to fuel the biogas plants in areas where unavailability of fresh dung hinders their continuous functioning. Our results first time showed the presence of viable methanogens in dry cattle dung stored for prolonged periods of time.     

Evidence for the involvement of multiple pathways in the biodegradation of 1- and 2-methylnaphthalene by Pseudomonas putida CSV86

Pseudomonas putida CSV86, a soil bacterium, grows on 1- and 2-methylnaphthalene as the sole source of carbon and energy. In order to deduce the pathways for the biodegradation of 1- and 2-methylnaphthalene, metabolites were isolated from the spent medium and purified by thin layer chromatography. Emphasis has been placed on the structural characterisation of isolated intermediates by GC-MS, demonstration of enzyme activities in the cell free extracts and measurement of oxygen uptake by whole cells in the presence of various probable metabolic intermediates. The data obtained from such a study suggest the possibility of occurrence of multiple pathways in the degradation of 1- and 2-methylnaphthalene. We propose that, in one of the pathways, the aromatic ring adjacent to the one bearing the methyl moiety is oxidized leading to the formation of methylsalicylates and methylcatechols. In another pathway the methyl side chain is hydroxylated to-CH₂OH which is further converted to-CHO and-COOH resulting in the formation of naphthoic acid as the end product. In addition to this, 2-hydroxymethylnaphthalene formed by the hydroxylation of the methyl group of 2-methylnaphthalene undergoes aromatic ring hydroxylation. The resultant dihydrodiol is further oxidised by a series of enzyme catalysed reactions to form 4-hydroxymethyl catechol as the end product of the pathway.     

Exploring the utility of Deep Red Anthraquinone 5 for digital staining of ex vivo confocal micrographs of optically sectioned skin

We investigated the utility of the fluorescent dye Deep Red Anthraquinone 5 (DRAQ5) for digital staining of optically sectioned skin in comparison to acridine orange (AO). Eight fresh-frozen thawed Mohs discard tissue specimens were stained with AO and DRAQ5, and imaged using an ex vivo confocal microscope at three wavelengths (488 nm and 638 nm for fluorescence, 785 nm for reflectance). Images were overlaid (AO + Reflectance, DRAQ5 + Reflectance), digitally stained, and evaluated by three investigators for perceived image quality (PIQ) and histopathological feature identification. In addition to nuclear staining, AO seemed to stain dermal fibers in a subset of cases in digitally stained images, while DRAQ5 staining was more specific to nuclei. Blinded evaluation showed substantial agreement, favoring DRAQ5 for PIQ (82%, Cl 75%-90%, Gwet's AC 0.74) and for visualization of histopathological features in (81%, Cl 73%-89%, Gwet's AC 0.67), supporting its use in digital staining of multimodal confocal micrographs of skin.     

Real‐time video mosaicking to guide handheld in vivo microscopy

Handheld and endoscopic optical‐sectioning microscopes are being developed for noninvasive screening and intraoperative consultation. Imaging a large extent of tissue is often desired, but miniature in vivo microscopes tend to suffer from limited fields of view. To extend the imaging field during clinical use, we have developed a real‐time video mosaicking method, which allows users to efficiently survey larger areas of tissue. Here, we modified a previous post‐processing mosaicking method so that real‐time mosaicking is possible at >30 frames/second when using a device that outputs images that are 400 × 400 pixels in size. Unlike other real‐time mosaicking methods, our strategy can accommodate image rotations and deformations that often occur during clinical use of a handheld microscope. We perform a feasibility study to demonstrate that the use of real‐time mosaicking is necessary to enable efficient sampling of a desired imaging field when using a handheld dual‐axis confocal microscope.