Thioploca

Thioploca is a genus of filamentous sulphur-oxidizing bacteria, in the order Thiotrichales (class Gammaproteobacteria). They inhabit both marine and freshwater environments, forming vast communities off the Pacific coast of South America and in other areas with a high organic matter sedimentation and bottom waters rich in nitrate and poor in oxygen. Their cells contain large vacuoles that occupy more than 80% of the cellular volume, used to store nitrate to oxidize sulphur for anaerobic respiration in the absence of oxygen, an important characteristic of the genus. With cell diameters ranging from 15-40 μm, they are some of the largest bacteria known. They provide an important link between the nitrogen and sulphur cycles, because they use both sulfur and nitrogen compounds. They secrete a sheath of mucus which they use as a tunnel to travel between sulphide-containing sediment and nitrate-containing sea water.