The Collaborative International Dictionary of English v.0.48:

Photobacterium \Pho`to*bac*te"ri*um\
   (f[=o]`t[-o]*b[a^]k*t[=e]"r[-e]*[u^]m), n. [NL. See Photo-,
   and Bacterium.] (Bacteriol.)
   A genus including certain comma-shaped marine bacteria which
   emit bluish or greenish phosphorescence. Also, any
   microorganism of this group.
   [Webster 1913 Suppl.]