Article Abstract:
Three different size classes of sheath-building sulfur bacteria Thioploca spp. are present off the coast of Chile. Thioploca sheaths occur over the whole shelf area where oxygen levels are low, and many Thioploca filaments lack a visible sheath. The highest wet weight of the sheaths is at a depth of 90 m, with the bacterial filaments making up approximately 10% of the weight. The upper 1 cm of the bacterial mat contains the maximum density of filaments. The three-dimensional sheath structure indicates that Thioploca filaments are able to move from the top to the bottom of the sediments.
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Article Abstract:
Filamentous sulfur bacteria of the genus Thioploca are found as dense mats on the continental shelf off the coast of Chile and Peru. It has been suggested that these large vacuolated bacteria can oxidize sulfide by reducing their internally stored nitrate. This nitrate reduction was studied by incubation experiments of washed Thioploca sheaths with trichomes in combination with 15N compounds and mass spectrometry. Findings showed that the Thioploca species are facultative chemolithoautotrophs capable of mixotrophic growth.
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Article Abstract:
Researchers document that the sulfide-oxidizing bacterium Thioploca shuttles vertically in marine sediments between NO(sub 3)-rich bottom water and H(sub2)S-containing sediment. Bacteria containing intracellular NO(sub 3)- were found at a depth of 13 cm in sediment cores incubated in the laboratory.
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