Elemental characterization of microorganism granules by EFTEM in the tube wall of a deep‐sea vent invertebrate

Abstract

Microorganisms colonizing the exoskeletons of the tube worm Riftia pachyptila are described at the ultrastructural level. The prokaryotic cells from the worm tube wall differ from those colonizing the exoskeleton outer surface in the presence of an electron dense granule. The morphology and distribution of these bacteria-like cells are described. Prokaryotic organisms are assembled in nodules which increased in size in the oldest part of the exoskeleton. The aspect, location and elemental composition of the intracellular granules are determined. Most of them (100 nm in diameter) are located close to the cell membrane and exhibit a homogeneous and amorphous content. EDX and EFTEM microanalyses show that these structures contain phosphorus, oxygen and iron. All together these data suggest that these granules are iron polyphosphates. These structures may act as energy sources for making ATP during anoxic conditions as existing in hydrothermal environments.

A public software for energy filtering transmission electron tomography (EFTET-J): Application to the study of granular inclusions in bacteria from Riftia pachyptila

“…The associated EELS-STEM analysis of granules has conWrmed the feasibility of detecting iron signal in semi-thin sections. Our results correlate well with previous data obtained in ultra-thin sections of the R. pachyptila tube in which the composition of the inorganic inclusions has been estimated as iron-polyphosphates (Lechaire et al, 2002). This validates the choice of R. pachyptila to test EFTET-J for computing 3D-chemical maps.…”

“…In a previous work, we have demonstrated by EFTEM the existence of granular inclusions in bacteria inhabiting the R. pachyptila tube (Lechaire et al, 2002). These inclusions, basically composed by iron poly-phosphates, appear as highly electron-dense objects (100 nm in diameter) in ultra-thin epon sections.…”

“…To test EFTET-J, we have applied it to the study of iron distribution in bacteria inhabiting the tube of R. pachyptila. This sample has the advantage to contain well deWned granular inclusions composed of iron polyphosphates (Lechaire et al, 2002) which can be easily observed as electron-dense particles of 100nm in diameter in Zero-loss images (Fig. 4A).…”

“…They were prepared for electron microscopy as described in Lechaire et al, 2002. Semi-thin sections (200 nm thick) of epon embedded samples were obtained from a Leica ultramicrotome (Ultracut R) and placed on 100 £ 200 mesh "oyster" copper grids.…”

Distribution of bacteria and associated minerals in the gill chamber of the vent shrimp Rimicaris exoculata and related biogeochemical processes

“…Metazoan-associated bacteria have been reported to lead to the formation of iron minerals at hydrothermal vents (Zbinden et al 2001, Lechaire et al 2002, but until now never to the formation of iron oxides. The precipitation and accumulation of iron oxides in association with bacterial cells is common in aqueous environments, where high concentrations of Fe III are produced by the oxidation of the reduced form Fe II (Juniper & Tebo 1995, Ferris et al 2000.…”