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 have observed in the photosynthetic equation reaction, oxygen is not produce therefore P. phosphoreum is known to have an anoxygenic photosynthesis Encyclopedia of Life Sciences.