Vibrio harveyi

Vibrio harveyi is a Gram-negative, bioluminescent, marine bacterium in the genusVibrio that was first discovered by Johnson and Shunk in their 1963 publication "An interesting new species of luminous bacteria". V. harveyi is rod-shaped, motile (via polar flagella), facultatively anaerobic, halophilic, and competent for both fermentative and respiratory metabolism. It is typically found in aquatic ecosystems — particularly in warmer tropical waters (optimum growth: 30° to 35 °C) — as a free-living bacterium. However, V. harveyi can also live commensally with other marine life, form biofilms on marine surfaces, and act as a pathogen in organisms like coral and oysters. This bacterium is tolerant to fluxes in environmental conditions, a characteristic attributed to its rapid adaptation caused by mutations and Horizontal Gene Transfer. This tolerance allows V. harveyi to thrive in environments affected by climate change.

Certain strains of V. harveyi can cause disease in marine life, such as luminous vibriosis — a disease that causes commercially farmed penaeid prawns to glow in the dark. The pathogenicity of these strains can be enhanced in environments affected by climate change, primarily due to the weakening of marine hosts. Despite its harmful effects, V. harveyi plays a beneficial role in nutrient cycling by using chitin — a building block of marine invertebrate exoskeletons — as a carbon source. It does so by breaking chitin down into simpler molecules that are used and eventually returned to the aquatic system to be taken up by other organisms. This species is also thought to be the cause of the milky seas effect, in which, a uniform blue glow is emitted from seawater during the night. Some glows can cover nearly 6,000 sq mi (16,000 km²).