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Ultrastructure and cytochemistry of lipid granules in the many-celled magnetotactic prokaryote,‘Candidatus Magnetoglobus multicellularis’

Abstract:

Conspicuous cytoplasmic granules are reported in a magnetotactic multicellular prokaryote named ‘Candidatus Magnetoglobus multicellularis’. Unfortunately, this microorganism, which consists of an assembly of gram-negative bacterial cells, cannot yet be cultivated, limiting the biochemical analysis of the granules and preventing in vitro studies with starvation/excess of nutrients. In this scenario, light and electron microscopy techniques were used to partially address the nature of the granules. Besides magnetosomes, three types of inclusions were observed: small (mean diameter=124nm) polyhydroxyalkanoate-like (PHA) granules, large (diameters ranging from 0.11 to 2.5μm) non-PHA lipid granules, and rare phosphorus-rich granules, which probably correspond to polyphosphate bodies. The PHA granules were rounded in projection, non-reactive with OsO4, and suffered the typical plastic deformation of PHAs …