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The cytotoxicity of Al(2)O(3) nanoparticles (NP) at very low exposure levels (1 μg/mL and less) to a dominant bacterial isolate from freshwater (lake water), Bacillus licheniformis, was examined. Sterile lake water was directly used as a test medium or matrix to simulate the freshwater environment. Exposure to 1 μg/mL Al(2)O(3) NP for 2 h caused a 17% decrease in cell viability (as determined by plate count and MTT assay). During the test period, the particles were found to be stable against aggregation in the matrix and exerted a nano-size effect on the exposed test organisms. The decrease in cell viability was proven not to be due to the release of Al(3+) ions from the nanoparticles in the dispersion. The zeta potential and FT-IR analyses suggested that the surface charge based attachment of nanoparticles on to the bacterial cell wall was responsible for flocculation leading to toxicity. The cell wall damage confirmed through SEM and the lipid peroxidation assay also contributed toward toxicity. This study warns of possible ecotoxicity of nanoparticles even at environmentally relevant concentrations. However, detailed studies need to be carried out to establish probable mechanistic aspects of this low concentration toxicity phenomenon.

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How does the Drosophila gut get colonized by the microbiota and

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Among various photoreceptors present in arthropods Drosophila eye undergoes certain modification to provide high resolution and sensitivity to the animal. Along with the compound eye Drosophila possess three ocelli for its vision, navigation and locomotion purpose. These ocelli are arranged in a triangular manner in between the compound eye. During third instar larvae, from the eye antenna imaginal disc several conserved genes and complex regulatory genetic network help in ocellar patterning. Like compound eye ocelli possess cornea, corneagenous cell, photoreceptor cells (rhabdom). The visual pigment present in ocelli is Rh2 and is responsible for the functioning of ocelli. Although rhabdomere are the photoreceptor organ of the ocelli the arrangement of the rhabdomere in ocelli differs from the compound eye. Interrhabdomereal space which is present between the rhabdomeres of photoreceptor cells are absent in ocelli. The rhabdom is confined only to the apical one-third of the ocelli whereas it expands throughout the length in compound eye. The structural difference present in the compound eye and ocelli enable us to study the functioning of one gene in different photoreceptors within an animal. Thus understanding the mechanism of ocellar development, genes involved in the functioning of ocelli will help us to understand the functioning of various genes in different photoreceptor. The current article summarises the structure, function and genes involved in the development of ocelli.

Seasonal polyphenism is a common phenomenon observed among members of the Lepidopteran subfamily Satyrinae. Melanitis leda, being a member of that subfamily, exhibits seasonal variation in terms of wing patterning. In butterflies, wing patterning is due to the nanostructural architecture of the scales, which reflects and refracts incident light, with or without the combination of pigments. The current scanning electron, fluorescence and optical microscope study divulge fine structural and signal changes that occur with different season in the scales of M. leda and give rise to the different wing pattern in butterfly. The structural and consequent signal changes are likely to be correlated with behavioural processes such as mate selection and escape from predation.

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