Flow cytometry as a rapid analytical tool to determine physiological responses to changing O2 and iron concentration by Magnetospirillum gryphiswaldense strain MSR-1

Magnetotactic bacteria (MTB) are a diverse group of bacteria that synthesise magnetosomes, magnetic membrane-bound nanoparticles that have a variety of diagnostic, clinical and biotechnological applications. We present the development of rapid methods using flow cytometry to characterize several aspects of the physiology of the commonly-used MTB Magnetospirillum gryphiswaldense MSR-1. Flow cytometry is an optical technique that rapidly measures characteristics of individual bacteria within a culture, thereby allowing determination of population heterogeneity and also permitting direct analysis of bacteria. Scatter measurements were used to measure and compare bacterial size, shape and morphology. Membrane permeability and polarization were measured using the dyes propidium iodide and bis-(1,3-dibutylbarbituric acid) trimethine oxonol to determine the viability and ‘health’ of bacteria. Dyes were also used to determine changes in concentration of intracellular free iron and polyhydroxylakanoate (PHA), a bacterial energy storage polymer. These tools were then used to characterize the responses of MTB to different O2 concentrations and iron-sufficient or iron-limited growth. Rapid analysis of MTB physiology will allow development of bioprocesses for the production of magnetosomes, and will increase understanding of this fascinating and useful group of bacteria

Composition and seasonal variation of the barn owl Tyto alba diet in Arizona

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Identification and theoretical investigation of the SiO(2+) dication

International audienceThe gas-phase diatomic dication SiO(2+) has been observed by mass spectrometry and identified by its isotopic abundance. It was produced by energetic, high-current oxygen ((16)O ) ion beam sputtering of a silicon surface and survived a flight time of similar to 10 (5) s. In addition, a detailed theoretical study of SiO2+ has been performed. Our calculations show that SiO(2+) is a metastable species with a large potential barrier towards dissociation (similar to 1.55 eV for the SiO(2+) X ground state). We have derived a set of accurate spectroscopic constants and transition energies for SiO(2+). The adiabatic double ionization energy of SiO is similar to 31 eV. (C) 2009 Elsevier B. V. All rights reserved

Oxygen-containing gas-phase diatomic trications and tetracations: ReOz+, NbOz+ and HfOz+ (z = 3, 4)

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