Ultrastructure and cytochemistry of lipid granules in the many-celled magnetotactic prokaryote, 'Candidatus Magnetoglobus multicellularis'.
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=124 nm) polyhydroxyalkanoate-like (PHA) granules, large (diameters ranging from 0.11 to 2.5 microm) 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 OsO(4), and suffered the typical plastic deformation of PHAs after freeze fracturing. The nature of the large granules, consisting of round globular structures (mean diameter=0.76 microm), was classified as non-PHA based on the following data: (a) multilayered structure in freeze-fracture electron microscopy, typical of non-PHA lipids; (b) Nile blue fluorescence imaging detected non-PHA lipids; (c) imidazole buffered osmium tetroxide and ruthenium red cytochemistry stained the globules, which appeared as electron-dense granules instead of electron lucent as PHAs do. Most likely, 'Candidatus Magnetoglobus multicellularis' stores carbon mainly as unusual lipid granules, together with smaller amounts of PHAs.
Silva
Karen Tavares
KT
Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil.
Abreu
Fernanda
F
Keim
Carolina N
CN
Farina
Marcos
M
Lins
Ulysses
U
D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D004577:Electron Probe Microanalysis; D005614:Freeze Fracturing; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000648:ultrastructure*; D008055:Lipids / Q000032:analysis*; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D054813:Polyhydroxyalkanoates / Q000032:analysis
D008055:Lipids; D054813:Polyhydroxyalkanoates