Photobacterium can be both very useful and very malignant depending from what perspective you are looking at. Below are some of these importances describes briefly.
Photobacterium (and other luminescent organisms as well) produce light by using the enzyme Luciferase in the following reaction:
FMNH2 + O2 + RCHO -------> FMN + RCOOH + H2O + LIGHT
FMN = Flavin Mononucleotide (reduced form is FMNH2)
Scientists are still 'in the dark' as to why this light-emitting system evolved in the first place. Some suggest, back in the early days of the earth when oxygen was more a toxin than anything, anaerobic cells attempted to decrease the amount of 'toxic' O2 (abeit very inefficiently) with this O2-consuming reaction.
Though the reasons are unknown, the system is, and scientists have utilized it as a wonderful biomarker in biotechnology. By combining the gene for luciferase along with another DNA segment under study, molecular biologists can test whether these genes actually inserted into another organism's DNA. Add a little luciferin as a substrate for luciferase, and your cultures may glow. This is just one very general way luminescent technology can be utilized in Biotechnology.
Ph. phosporeum as also received some fame, as it has been used as an indicatior organism in tests determining the toxicity of compounds (for example, Microtox). What better way to see toxin inhibition then by looking at light?
Photobacterium is harmless to humans, but, being a marine organism, a species or two have developed into pathogens of marine life. Since these diseases can infect commercially important fish, Phtobacterium does indirectly impact humans.
Photobacterium damselae subsp. piscicida is the causative agent of fish Pasteurellosis. Bacterial colonies grown on the infected fish's spleen and kidneys. It is a lethal disease and accounts for severe losses in some fish farming enterprises. Species of fish infected include Yellowtails, Gilt-head Sea Bream, Black Sea Bream, Striped Bass, and White Perch.
Ph. damselae subsp. damsela has been associated with ulcer-type lesions. Muscle lysis does occur in these wounds. Species of fish infected include Yellowtails, Damsel Fish, Sharks, and Turbot.
The Photobacterium genus has also been shown to degrade chitin of the Deep Sea Tanner Crab. This causes lesions on the crab's shell and is refered to as 'shell disease'.
Photobacterium can be isolated from dead fish, so certainly have some impact on spoilage. Photobacterium can produce hypoxanthine (from inosine-5-monophosphate) and also trimethylamine (smelly compounds!) in fish and shrimp. Again, though Photobacterium may like to feed on dead fish, no species have been found to effect the health of humans.