Vibrio harveyi
Encyclopedia
Vibrio harveyi is a species of Gram-negative
, bioluminescent
, marine bacteria
in the genus
Vibrio
. V. harveyi are rod-shaped, motile (via polar flagella), facultatively anaerobic, halophilic, and competent for both fermentative and respiratory metabolism. They do not grow at 4°C or above 35°C. V. harveyi can be found free-swimming in tropical marine waters, commensally in the gut microflora of marine
animals, and as both a primary and opportunistic pathogen of marine animals, including Gorgonian corals, oysters, prawns, lobsters, the common snook
, barramundi
, turbot
, milkfish
, and seahorses. V. harveyi is responsible for luminous vibriosis, a disease that affects commercially-farmed penaeid prawns. Additionally, based on samples taken by ocean-going ships, V. harveyi is thought to be the cause of the milky seas effect
, in which, during the night, a uniform blue glow is emitted from the seawater
. Some glows can cover nearly 6000 square miles (15,539.9 km²).
to coordinate the production of bioluminescense and virulence factors. Quorum sensing was first studied in Vibrio fischeri, a marine bacterium that uses a synthase
(LuxI) to produce a species-specific autoinducer
(AI) that binds a cognate receptor (LuxR) that regulates changes in expression. Coined "LuxI/R" quorum sensing, these systems have been identified in many other species of Gram-negative bacteria. Despite its relatedness to V. fischeri, V. harveyi lacks a LuxI/R quorum sensing system, and instead employs a hybrid quorum-sensing circuit, detecting its AI via a membrane-bound histidine kinase
and using a phosphorelay to convert information about the population size to changes in gene expression. Since their identification in V. harveyi, such hybrid systems have been identified in many other bacterial species. It was also discovered that V. harveyi uses a second AI, termed autoinducer-2
or AI-2, which is unusual because it is made and detected by a variety of different bacteria, both Gram-negative and Gram-positive. Thus, V. harveyi has been instrumental to our understanding and appreciation of interspecies bacterial communication.
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
, bioluminescent
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
, marine bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Vibrio
Vibrio
Vibrio is a genus of Gram-negative bacteria possessing a curved rod shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Typically found in saltwater, Vibrio are facultative anaerobes that test positive for oxidase and do not form...
. V. harveyi are rod-shaped, motile (via polar flagella), facultatively anaerobic, halophilic, and competent for both fermentative and respiratory metabolism. They do not grow at 4°C or above 35°C. V. harveyi can be found free-swimming in tropical marine waters, commensally in the gut microflora of marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
animals, and as both a primary and opportunistic pathogen of marine animals, including Gorgonian corals, oysters, prawns, lobsters, the common snook
Snook
Snook or Snoek may refer to:* Fish in the family** Centropomidae especially the common snook.** Gempylidae ** Percidae ** Scombridae , subfamily: Scombrinae** Sphyraenidae...
, barramundi
Barramundi
The Barramundi , also known as Asian Seabass, is a species of catadromous fish in family Latidae of order Perciformes. The native species is widely distributed in the Indo-West Pacific region from the Persian Gulf, through Southeast Asia to Papua New Guinea and Northern Australia. Known in Thai...
, turbot
Turbot
The turbot is a species of flatfish in the family Scophthalmidae. It is native to marine or brackish waters of the North Atlantic, Baltic Sea and the Mediterranean Sea.-Etymology:...
, milkfish
Milkfish
The milkfish is the sole living species in the family Chanidae. - Description and biology :...
, and seahorses. V. harveyi is responsible for luminous vibriosis, a disease that affects commercially-farmed penaeid prawns. Additionally, based on samples taken by ocean-going ships, V. harveyi is thought to be the cause of the milky seas effect
Milky seas effect
Milky seas is a condition on the open ocean where large areas of seawater are filled with bioluminescent bacteria, causing the ocean to uniformly glow an eerie blue at night...
, in which, during the night, a uniform blue glow is emitted from the seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
. Some glows can cover nearly 6000 square miles (15,539.9 km²).
Quorum sensing
Groups of V. harveyi bacteria communicate via quorum sensingQuorum sensing
Quorum sensing is a system of stimulus and response correlated to population density. Many species of bacteria use quorum sensing to coordinate gene expression according to the density of their local population. In similar fashion, some social insects use quorum sensing to determine where to nest...
to coordinate the production of bioluminescense and virulence factors. Quorum sensing was first studied in Vibrio fischeri, a marine bacterium that uses a synthase
Synthase
In biochemistry, a synthase is an enzyme that catalyses a synthesis process.Following the EC number classification, they belong to the group of ligases, with lyases catalysing the reverse reaction....
(LuxI) to produce a species-specific autoinducer
Autoinducer
Autoinducers are chemical signaling molecules that are produced and used by bacteria participating in quorum sensing. Quorum sensing is a phenomenon that allows both Gram-negative and Gram-positive bacteria to sense one another and to regulate a wide variety of physiological activities. Such...
(AI) that binds a cognate receptor (LuxR) that regulates changes in expression. Coined "LuxI/R" quorum sensing, these systems have been identified in many other species of Gram-negative bacteria. Despite its relatedness to V. fischeri, V. harveyi lacks a LuxI/R quorum sensing system, and instead employs a hybrid quorum-sensing circuit, detecting its AI via a membrane-bound histidine kinase
Histidine kinase
Histidine Kinases are multifunctional, typically transmembrane, proteins of the transferase class that play a role in signal transduction across the cellular membrane. The vast majority of HKs are homodimers that exhibit autokinase, phosphotransfer, and phosphatase activity. HKs can act as...
and using a phosphorelay to convert information about the population size to changes in gene expression. Since their identification in V. harveyi, such hybrid systems have been identified in many other bacterial species. It was also discovered that V. harveyi uses a second AI, termed autoinducer-2
Autoinducer-2
Autoinducer-2 , a furanosyl borate diester, is a member of a family of signaling molecules used in quorum sensing. AI-2 is unique in that it is one of only a few known biomolecules incorporating boron. First identified in the marine bacterium Vibrio harveyi, AI-2 is produced and recognized by many...
or AI-2, which is unusual because it is made and detected by a variety of different bacteria, both Gram-negative and Gram-positive. Thus, V. harveyi has been instrumental to our understanding and appreciation of interspecies bacterial communication.