Motility of the giant sulfur bacteria Beggiatoa in the marine environment

Beggiatoa inhabit the microoxic zone in sediments. They oxidize reduced sulfur compounds such as sulfide with oxygen or nitrate. Beggiatoa move by gliding and respond to stimuli like oxygen, light and sulfide. Using these substances for orientation, they can form dense mats on the sediment surface. Gliding motility as a function of temperature revealed that the temperature range of gliding correlated with the climatic origin of the filaments. The filaments were accordingly well adapted to the temperature regime of their origin. Consequently, an examination of Beggiatoa in arctic fjord sediments on the west coast of the archipelago Svalbard demonstrated that the filaments grow well under permanently cold conditions where they constituted even up to 15 % of the prokaryotic biomass. Observations of Beggiatoa in an artificial gradient of oxygen sulfide shed light on the mechanism used to orient in the microoxic environment. A model based on these observations was developed to explain their distribution in the sediment where Beggiatoa cannot be observed by eye.