Plateforme d’imagerie Cellulaire et Tissulaire

Publications

Année de publication : 2011

Wolkow N., Song Y., Wu T.D., Qian J., Guerquin-Kern J.L., Dunaief J.L. (2011 Nov 1)

Aceruloplasminemia: retinal histopathologic manifestations and iron-mediated melanosome degradation.

Archives of ophthalmology : 129 : 1466-74 : DOI : 10.1001/archophthalmol.2011.309 En savoir plus
Résumé

To examine the retinal histopathologic manifestation of aceruloplasminemia, an autosomal recessive disease caused by mutation of the ferroxidase ceruloplasmin, resulting in tissue iron overload.

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Année de publication : 2010

Byrne M.E., Ball D.A., Guerquin-Kern J.L., Rouiller I., Wu T.D., Downing K.H., Vali H., Komeili A. (2010 Jul 6)

Desulfovibrio magneticus RS-1 contains an iron- and phosphorus-rich organelle distinct from its bullet-shaped magnetosomes.

Proceedings of the National Academy of Sciences of the United States of America : 107 : 12263-8 : DOI : 10.1073/pnas.1001290107 En savoir plus
Résumé

Intracellular magnetite crystal formation by magnetotactic bacteria has emerged as a powerful model for investigating the cellular and molecular mechanisms of biomineralization, a process common to all branches of life. Although magnetotactic bacteria are phylogenetically diverse and their crystals morphologically diverse, studies to date have focused on a few, closely related species with similar crystal habits. Here, we investigate the process of magnetite biomineralization in Desulfovibrio magneticus sp. RS-1, the only reported species of cultured magnetotactic bacteria that is outside of the alpha-Proteobacteria and that forms bullet-shaped crystals. Using a variety of high-resolution imaging and analytical tools, we show that RS-1 cells form amorphous, noncrystalline granules containing iron and phosphorus before forming magnetite crystals. Using NanoSIMS (dynamic secondary ion mass spectroscopy), we show that the iron-phosphorus granules and the magnetite crystals are likely formed through separate cellular processes. Analysis of the cellular ultrastructure of RS-1 using cryo-ultramicrotomy, cryo-electron tomography, and tomography of ultrathin sections reveals that the magnetite crystals are not surrounded by membranes but that the iron-phosphorus granules are surrounded by membranous compartments. The varied cellular paths for the formation of these two minerals lead us to suggest that the iron-phosphorus granules constitute a distinct bacterial organelle.

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Duhutrel P., Bordat C., Wu T.D., Zagorec M., Guerquin-Kern J.L., Champomier-Vergès M.C. (2010 Jan 1)

Iron sources used by the nonpathogenic lactic acid bacterium Lactobacillus sakei as revealed by electron energy loss spectroscopy and secondary-ion mass spectrometry.

Applied and environmental microbiology : 76 : 560-5 : DOI : 10.1128/AEM.02205-09 En savoir plus
Résumé

Lactobacillus sakei is a lactic acid bacterium naturally found on meat. Although it is generally acknowledged that lactic acid bacteria are rare species in the microbial world which do not have iron requirements, the genome sequence of L. sakei 23K has revealed quite complete genetic equipment dedicated to transport and use of this metal. Here, we aimed to investigate which iron sources could be used by this species as well as their role in the bacterium&aquote;s physiology. Therefore, we developed a microscopy approach based on electron energy loss spectroscopy (EELS) analysis and nano-scale secondary-ion mass spectrometry (SIMS) in order to analyze the iron content of L. sakei cells. This revealed that L. sakei can use iron sources found in its natural ecosystem, myoglobin, hemoglobin, hematin, and transferrin, to ensure long-term survival during stationary phase. This study reveals that analytical image methods (EELS and SIMS) are powerful complementary tools for investigation of metal utilization by bacteria.

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