Photobacterium phosphoreum

Cell structure and metabolism

P. phosphoreum belongs to the phylum Proteobacteria. All bacteria that belong to that phylum are known to be Gram-negative. As gram-negative P. phosphoreum contain an outer membrane made of lipopolysaccharide outside and inside phospholipids, a periplasma space, a thin peptidoglycan layer and finally the plasma membrane Encyclopedia of Life Sciences.

P. phosphoreum is a chemoorganotroph which is capable of respiratory and fermentative metabolism [1]. It is a facultative anaerobe that can grow in the absence of oxygen when appropriate electron-acceptors are present. It doesn’t denitrify; in other word, it cannot use nitrogen molecules [2].

P. phosphoreum can produce blue-green light with the help of an enzyme called luciferase. “Luciferase catalyzes the reaction and uses reduced flavin mononucleotide, molecular oxygen, and a long-chain aldehyde as substrate” (Prescott, Harley and Klein 559).

Equation

FMNH₂ + O₂ + RCHO + luciferase → FMH + H₂ + RCOOH + light

When the excited flavin intermediate (FMN) moves to ground state, it emits the light which is one of the products of the reaction [3]. "The bioluminescence quantum yield has been estimated to be 10–30%" Encyclopedia of Life Sciences. If you observed in the equation, oxygen is not produce for this reason P. phosphoreum is known to have an anoxygenic photosynthesis Encyclopedia of Life Sciences.