How inappropriate to call this planet Earth when it is quite clearly Ocean.
Arthur C. Clarke
Budding is evident on these attached, elongated Thio-
margarita-like bacteria collected near a methane seep off
the coast of Costa Rica. Bar = ~1 mm. Source.
Ahhh, the delicious aroma of hydrogen sulfide. When as kids we encountered it, we would hold our nose and proclaim “yuck, rotten eggs!” It is indeed produced by something ‘rotting,’ but specifically rotting under anaerobic conditions, such as in swamps and sewers. It is also abundant in coastal marine sediments, produced by the oxygen-consuming heterotrophic decomposition of organic matter. This makes for a layer at the sea bottom that is sulfide rich but oxygen poor. Nevertheless, leaving no potential energy source untapped, some bacteria in these zones use sulfur oxidation as their energy source. They include two remarkably large γ-proteobacteria, Thioploca and Thiomargarita. Thioploca copes with the lack of oxygen by using nitrate as an alternate terminal electron acceptor, but this just exchanges one problem for another. The sulfides are in the sediment, the nitrate in the water column above. So Thioploca commutes between the two zones, as Elio described in an earlier post.
Thiomargarita namibiensis, the “Namibian sulfur pearl.”
Courtesy of the Microbiological Garden. Source.
Non-motile Thiomargarita uses a different tactic. This bacterium was first discovered in 1999 off the Namibian coast, thus was named T. namibiensis. Its cells are large spheres, arranged in chains, each chain enclosed in a mucous sheath. Average cell diameter is 180 μm, with rare individuals reaching 750 μm, which is about as big as bacterial cells get. But they do this by cheating. Most of the ‘cell’ is a large vacuole, with the cytoplasm relegated to a thin surrounding outer layer. Sulfur globules are evident in the cytoplasm. Thus the genus name, Thiomargarita, that was derived from the Greek for ‘sulfur pearl.’ Thiomargarita spp. are widespread in hydrogen sulfide-rich coastal sediments. They, too, use nitrate as their terminal electron acceptor. Their strategy is to take advantage of the occasional events that resuspend the sediment and bring abundant nitrates into the water column. They then hoard nitrate in their huge vacuoles—enough nitrate to see them through even months of scarcity.