High-density super-resolution microscopy with an incoherent light source and a conventional epifluorescence microscope setup

We report that single-molecule superresolution microscopy can be achieved with a conventional epifluorescence microscope setup and a Mercury arc lamp. The configuration termed as Omnipresent Localisation Microscope (OLM), is an extension of Single Molecule Localisation Microscopy (SMLM) techniques and allows single molecules to be switched on and off (’blinking’), detected and localised. The use of a short burst of deep blue excitation can be further used to reactivate the blinking, once the blinking process has slowed or stopped. A resolution of 90 nm is achieved on test specimens (mouse and amphibian meiotic chromosomes). Finally, for the first time, we demonstrate that STED and OLM can be performed on the same biological sample using a simple imaging buffer. It is hoped that such a correlative imaging will provide a basis for a further enhanced resolution.Scope of the findingsDespite ten years of development, superresolution microscopy is still limited to relatively few microscopy and optics groups. This is mainly due to the significant cost of the superresolution microscopes which require high-quality lasers, high NA objective lens, a very sensitive camera, a highly precise microscope stage, and a complex post-acquisition data reconstruction and analysis. We present results that demonstrate the possibility to obtain nanoscale resolution images using a conventional microscope and an incoherent light source. We show an easyto-follow protocol that every biologist can implement in the laboratory. We hope that this finding will help any scientist to generate high-density super-resolution images even with limited budget. Lastly, the new photophysical observations reported here will pave the way for more in-depth investigations on excitation, photobleaching and photoactivation of a fluorophore.

Bacteria in Himalayan glacial ice and its relationship to dust

Concentrations and community diversity of bacteria from 50 segments of a 108.83 m ice core drilled from the East Rongbuk (ER) Glacier (28.03° N, 86.96° E, 6518 m above sea level) on the northeast slope of Mt. Qomolangma (Everest), covering the period 950–1963 AD, were investigated by epifluorescence microscope, DGGE and Shannon-Weaver index analysis. Bacteria in the ER core were identified as β, γ-proteobacteria and Firmicutes group, with γ-proteobacteria being the dominance. Different bacterial population was identified along the core, reflecting the effects of climatic and environmental changes on the bacterial distribution in the glacial ice. There are four general periods of bacterial diversity, corresponding to four phases of dust abundance revealed by Ca2+ concentrations. However, a previously suggested positive correlation between bacterial and Ca2+ concentrations was not indicated by our observations. Instead, a weak negative correlation was found between these two parameters. Our results suggest that bacterial community diversity, rather than concentrations, might be a suitable biological proxy for the reconstruction of past climatic and environmental changes preserved in glacial ice.

Bacterial diversity in Himalayan glacial ice and its relationship to dust

Concentrations and community diversity of bacteria from 50 segments of a 108.83 m ice core drilled from the East Rongbuk (ER) Glacier (28.03° N, 86.96° E, 6518 m above sea level) on the northeast slope of Mt. Qomolangma (Everest), covering the period 950–1963 AD, were investigated by epifluorescence microscope, DGGE and Shannon-Weaver index analysis. There are four general periods of bacterial diversity, corresponding to four phases of dust abundance revealed by Ca2+ concentrations. It is indicated that higher bacterial community diversity is associated with warm periods, while lower bacterial community diversity with cold periods. However, a previously suggested positive correlation between bacterial and Ca2+ concentrations was not indicated by our observations. In fact, a weakly negative correlation was found between these two parameters. Our results suggest that bacterial community diversity, rather than concentrations, might be a suitable biological proxy for the reconstruction of past climatic and environmental changes preserved in glacial ice.