lakes, and near deep hydrothermal vents. beggiatoa can also be found in the rhizosphere of swamp plants, in soil, marine sediments and in the mangrove lagoon too (where they contribute to the lipid pool of the sediments). the freshwater species have typical habitats in sulfur springs, ditches, puddles, wetlands, lake sediments and in rice fields, where it can grow associated with the rice plants’ roots. the beggiatoa that live in marine water can be found in regions where their source of energy (sulfide or thiosulfide) is available. it can be extracted from both inorganic or organic source and usually it is coupled with microoxic condition, therefore very low concentration of oxygen. this genus of gammaprotobacteria is also common in localizated area of anaerobic decomposition as whale carcass on the deep ocean seafloor. a beggiatoa-like bacterial mat filaments in underwater cave. vacuolated beggiatoa can be very common in coastal upwelling regions (for example peru and chile coasts), deep sea hydrothermal vents and cold vents; in these environments the floc mats (hair-like breast) can grow up and cover large areas and reach the height of 30 cm. in deep sea hydrothermal vents and cold-seeps beggiatoa can grow in filaments that can be up to 200 micrometres in diameter, which makes these ones the largest prokaryotes currently known. vacuolated beggiatoa can be found also in hypoxic seafloor, where the filaments can live inside the sediments at the depth of few cm (from 2 to 4 cm); in same cases the beggiatoa bacterial filaments can be the most abundant part of the microbial biomass in the sediments. beggiatoa can also be found in salt marshes, saline, and geothermally active underwater caves. some studies on these environments have been carried out in the underwater caves of dolomitized limestone in capo palinuro, salerno, (italy). here there are hydrothermal sulphidic springs and microbial biofilm is associated with the flow of hydrothermal fluids, whose activity is intermittent and starts during low tide. mats found in the caves were composed by filaments resembling in most part beggiatoa, thiothrix and flexibacter, and this beggiatoa-like filaments were morphologically close to those found attached to rocks and the byssus of the mussels from lucky strike hydrothermal vents on the mid-atlantic ridge. interactions with other organisms frequently, microorganisms of the genus beggiatoa can form complex microbial mats, where they live in association with many other filamentous bacteria, such as cyanobacteria. the latter usually occupy the surface layer of the mat and during the day they produce a great amount of oxygen, derived from the photosynthetic activity. conversely, beggiatoa grow along an oxic/anoxic (oxygen/sulfide) interface, beneath the phototrophs, where they produce white patches. however, during dark acclimation, the mat became anoxic, so the beggiatoa moved to the mat surface, to avoid the high levels of h2s and remain at the oxygen/sulfide interface, while cyanobacteria remained in a dense layer below. sometimes beggiatoa mats are enriched by the presence of diatoms and green euglenoids too, but also protists as ciliates and dinoflagellates have been found associated with the mats at the guaymas basin hydrothermal vent ecosystem and they likely consume a large amount of bacterial biomass. as the microbial mats can reach 3 cm in width, they can represent a source of food for many grazers. this trophic connection has been observed in mangrove systems, where beggiatoa cover part of marine sediments. it has been observed that these bacteria give an important contribution to meiofauna's diet, in particular rotifers, polychaetes, nematodes and some groups of platyhelminthes, aschelminths and gnathostomulids. a remarkable relationship has been found between nematodes and beggiatoa. in fact nematodes seem to favor development of beggiatoa mats, through the increasing of oxygen penetration and nutrient diffusion into the mat. furthermore, many carrion appear covered by mats of beggiatoa-like filamentous bacteria overlying anaerobic sulfate-reducing bacteria. they attract many metazoans scavengers, but when they break the mat, it releases hydrogen sulphide that drive away the scavengers. hence, beggiatoa can also be considered a carrion defence from the scavengers. role in biogeochemical cycles massive mats of some beggiatoa-like filaments in an underwater cave several species of white sulfur bacteria in the family beggiatoaceae are able to accumulate and transport no3−, taken from shallow coastal sediments which is fundamental in metabolism, as well as accumulate it in filaments. the reduction of no3− to ammonium implies the oxidation of h2s (except for geothermal vents, the sulphide derives from the underlying anaerobic sediment in which dissimilatory sulphate reduction occurs): this reduction leads to the formation of suboxic zones characterized by positive redox potential and only trace concentrations of free h2s. in marine environment, the presence of these species is important because they have a fundamental role in regulation of the amount of h2s and no3− : on the one hand, the regulation of free h2s concentration in marine sediments is fundamental because sulfide-depleted surface sediments are essential for survival of benthic infauna, in fact sulfide is highly toxic to bottom fauna and other organisms living in the sediment; on the other hand, no3− reduction is important for the control of eutrophication in nitrogen-limited coastal waters. beggiatoa can also accumulate phosphorus as polyphosphate and it subsequently releases phosphate in anoxic conditions. this might increase the availability of phosphorus to primary producers if the phosphate is released from the sediment to the water column. some studies about the phosphorus cycling and the release of phosphorus linked to beggiatoa have been realized in baltic sea. these studies showed that the reduction of sulfide by these bacteria may decrease the rate of iron sulfide formation in the sediments, and thus increase the phosphorus retention capability of the sediment. cultivation selective enrichments the most successful enrichments for beggiatoa spp. have been made using a shallow pan or aquarium in which it has been added few centimeters of sand, different amount of caso4 and k2hpo4, a source of complex organic polymers such as seaweed, several centimeters of sulfide-rich marine mud and seawater. the enrichment must contain the proper sulfide-oxygen interface that can be possible only if air is introduced, for example, by a slow steady flow of freshly aerated seawater. another type of enrichment associated with beggiatoa spp. is based on the use of extracted dried grass or hay in a mineral medium because the complex polymers such as cellulose residues in the material provide sulfate reduction. this also provides the hydrogen sulfide necessary to enrich for beggiatoa. pure culture isolation there are three different possible techniques to obtain isolated beggiatoa strains in pure culture: isolation on agar plates isolation using liquid media isolation and cultivation in gradient media isolation on agar plates some beggiatoa-like filaments near a tiny hole the procedure that allows to obtain isolated heterotrophic strain requires an agar plate containing dilute organic substrate such as small amount of peptone. then, it's necessary to collect tufts of beggiatoa filaments from the environment, to wash them using sterile washing solution and to place them on the agar plate. in this way there will be some growing filaments moving away from the central inoculum that can be used as inoculum for a new agar plate. for the isolation of marine beggiatoa strains (that show autotrophic growth), since they are obligate microaerophiles it's essential to provide micro-oxic conditions and to use particular agar plates made by filtered seawater supplemented with sodium sulfide and sodium acetate. on the contrary, for the freshwater strains isolation it's necessary to perform under oxic conditions (air atmosphere) using a variety of media containing a low concentration of single organic compound such as acetate, na2s or thiosulfate. isolation using liquid media liquid media are often used for enrichment, mpn enumeration and bulk cultivation of beggiatoa. in order to have a successful cultivation of heterotrophic or mixotrophic freshwater beggiatoa, liquid media has to contain little amounts of carbon substrate, either soil extracts or acetate. the type species and strain (beggiatoa alba str. b18ld) and related strains are generally grown in media that include a salt base, acetate as carbon source, and variable yeast extract and sulfide additions. some marine autotrophic beggiatoa strains are also been cultured on defined liquid mineral medium with thiosulfate, co2, micro-oxic conditions under aeration with 0.25% o2 (v/v) in the gas phase. isolation and cultivation in gradient media autotrophic strains coming from a single filament isolation on agar can easily be maintained and propagated in sulfide gradient tubes in which sulfide-rich agar plugs are overlaid with sulfide-free soft agar. tubs are loosely closed in order to permit the exchange of headspace gasses with the atmosphere. as result, two opposite layers are formed, one that contains sulfide while the other one oxygen: this allows the growth of a well-defined beggiatoa layer at the sulfide-oxygen interface. the gradient medium construction requires different amounts of j3 medium (made by agar and nahco3) supplemented with neutralized na2s placed in a screw-capped tube. here, the sulfur source is provided by the flux of sulfide. another ‘’ layer ‘’ is made by nahco3 without sulfide or thiosulfate: all of the sulfide will be below the interface between the sulfidic agar plug and the sulfide-free overlay agar while there will be another layer in the top of the tube that represents the oxygen reservoir. it begins to form a gradient shape due to the reaction between sulfide and oxygen: as results, the filaments rapidly proliferate at the sulfide-oxygen interface, forming a marked layer or “plate,” of 1 mm but it's also possible to appreciate that these bacteria can track the interface and slowly descend owing to the gradual depletion of the sulfide reservoir.