Chlorobium 

What you should know:

Chlorobium are Gram-negative rods or spirals. They are photoautotrophs and use H₂S as electron source; they are also known as the Green Sulfur Bacteria.  They are anaerobic and carry out anoxygenic photosynthesis using bacteriochlorophyll. 

Classification: 

Domain Bacteria

    Phylum Chlorobi

        Class Chlorobia 

Bergey's Manual Volume 1: The Archaea and the deeply branching and phototrophic Bacteria