The purple sulfur bacterium Allochromatium vinosum prefers to use polymeric sulfur over cyclo-octasulfur when taking up elemental sulfur for photosynthesis. This was discovered through X-ray absorption spectroscopy analysis, showing that Alc. vinosum only utilizes the sulfur chain fraction of elemental sulfur. The bacterium is unable to form sulfur globules from cyclo-octasulfur and requires direct contact with sulfur for uptake.