''Leucothrix'' is a genus of large, filamentous bacteria, which live as epiphytes in marine habitats.

Systematics

''Leucothrix'' Oersted, 1844 is the type genus of the family Leucothricaceae Buchanan, 1957, but has also been classified in the family

Thiotrichaceae The Thiotrichaceae are a family of Pseudomonadota, including ''Thiomargarita namibiensis'', the largest known bacterium.George M. Garrity: ''Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Volume 2: ''The Prot ...

(

Gammaproteobacteria Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota (synonym Proteobacteria). It contains about 250 genera, which makes it the most genera-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically imp ...

). There are two species described, '' L. mucor'' Oersted, 1844 (

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

) and ''L. pacifica'' Zhang et al., 2015.

Description

''Leucothrix'' is a large bacterium that forms filaments between 2-3 µm wide and up to 0.5 cm in length. They are usually found as

epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...

s on marine plants and algae, but also grow attached to other surfaces like the shells of crustaceans. Like the related genus ''

Thiothrix ''Thiothrix'' is a genus of filamentous sulfur-oxidizing bacteria, related to the genera ''Beggiatoa'' and ''Thioploca''. They are usually Gram-negative (but can be Gram-variable) and rod-shaped (0.7–1.5 µm in width by 1.2–2.5 µm i ...

'', individual cells can be released from filaments, forming " gonidia", which can disperse and colonize new surfaces. On a new surface, the gonidial cells associate, produce a holdfast, and develop into rosettes of new filaments. Filaments of ''L. mucor'' can sometimes grow into

knot A knot is an intentional complication in cordage which may be practical or decorative, or both. Practical knots are classified by function, including hitches, bends, loop knots, and splices: a ''hitch'' fastens a rope to another object; a ' ...

s when cultivated in the laboratory under certain conditions. Physiologically, ''Leucothrix'' are

chemoheterotrophic A Chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototroph ...

, which distinguishes them from ''Thiothrix'', which are able to use sulfur oxidation as a source of energy.

References

Thiotrichales {{gammaproteobacteria-stub