Transylvania, move over. You've got nothing on the real-life vampires in Spain.
Lake Estanya in northeastern Spain is a karstic lake, a watery sinkhole carved into limestone and rich in minerals such as sulfates. It's shaped like the figure "8" and is at most, 20 meters deep. The lake is extremely stratified: as the light transmitted through the water decreases with depth, anoxic conditions increase. The top purple layers are thick with phototrophic sulfur bacteria due to the abundant amounts of light and sulfide.
These purple sulfer bacteria are species of rod-shaped Chromatium characterized by their ability for anoygenic photosynthesis in which no oxygen is produced. Researchers anaylzing these bacteria noted that there were primarily three Chromatium species swimming around in the lake: C. okenii, C. minus, and C. vinosum. In cultures of these Chromatium species, they noticed that there were smaller bacteria attached to them.
As you increase in lake depth, less sunlight is available and Chromatium decreases viability. Surprisingly, as depth increased, so did the number of the smaller bacteria which in turn preyed on the weakened Chromatium. These small round bacteria or Vampirococci were so named because they attached to their prey through pilus structures and "sucked" it dry of cytoplasm. The Vampirococcus grows in anaerobic conditions and can only replicate while it's attached to the prey. And in the end, all that remains of the poor microbe victim after the Vampirococcus is done is the husk: the cell wall, cytoplasmic membrane, and maybe bits of leftover organelles.
