They inhabit both marine and freshwater environments, forming vast communities off the Pacific coast of South America and in other areas with a high organic matter sedimentation and bottom waters rich in nitrate and poor in oxygen.

[3][4] Their cells contain large vacuoles that occupy more than 80% of the cellular volume, used to store nitrate to oxidize sulphur for anaerobic respiration in the absence of oxygen, an important characteristic of the genus.

[8][9] Thioploca are defined by their filamentous morphology, aggregated into bundles enclosed in a polysaccharide sheath, with either a parallel or braided appearance.

Although some morphological and phylogenetic differences have been found between marine and non-marine species, knowledge about freshwater and brackish Thioploca is still limited, as its ecology is poorly studied so far.

[12][14] Molecular phylogenies based on 16S rRNA sequences place the genera Thioploca and Beggiatoa in a monophyletic, diverse group within Gammaproteobacteria.

The genera were initially defined morphologically, Thioploca forms a sheath around their filament bundles, while Beggiatoa does not, which do not necessarily correspond to monophyletic groups in molecular phylogenies.

Although the sheaths of Thioploca are phenotypically similar to certain cyanobacteria, such as Microcoleus, the molecular phylogenies show that they are not close relatives but belong to different bacterial phyla.

Biochemical and physiological studies with harvested Thioploca filaments need to be handled carefully in order to avoid enzymatic activities due to air exposure.

[18] They are unlikely to be methylotrophs, as previously hypothesized, because they grow in areas that are poor in methane,[3] with concentrations that would not support the metabolic activity of the large Thioploca populations observed.

[18][16] In the vacuole the concentrations of nitrate can increase up to 0.5 M.[21] They have also shown the capacity to accumulate S0 (elemental sulphur) in the cells as globules, as a result of oxidation of hydrogen sulphide.

Hypothetically they could be in competition with other sulphide oxidizing bacteria, but with the ability to accumulate nitrate they create a perfect strategy to access both electron donor and acceptor at the same moment.

These gram-negative bacteria can be described as flexible, univariate, colorless filaments made up of numerous cells and enclosed by a common gelatinous sheath.

[28] In the latter ones, sulfur globules can be found and the cell wall has a complex, four-layered structure, of which the innermost layer and the cytoplasmic membrane go across the septum.

This location has two important consequences: The filamentous sulfur oxidizers Thioploca grows at oxic/anoxic interactions on freshwater, brackish and marine sediments where sulfide of biological and geothermal origin combines with oxygen or nitrate in the overlying water column.

Extensive rugs of Thioploca can be found on the Chilean and Peruvian continental shelf, where it grows on sediments that form the basis of deoxygenated water masses of the Peru-Chile countercurrent [29].

The thioplocas thus move up and down, recharging with nitrate at the surface and oxidizing sulfide at depth, therefore  storing elemental sulfur globules as an energy reserve.

More importantly, the differentiation between Thioploca and Beggiatoa is currently based on the formation of a common sheath surrounding filament bundles, a characteristic that might vary in response to environmental conditions.

In the absence of pure cultures, it may be impossible to prove or disprove whether any natural population of vacuolated Beggiatoa will form sheath bundles in some specific environment.

This feature currently appears to be the best morphological candidate to replace sheath formation as a marker in a revised taxonomy of the group Beggiatoa–Thioploca.

A future revision of the genus Thioploca, based on the vacuolated, nitrate-respiring phenotype and corresponding 16S rRNA clade, might include these gliding filaments regardless of whether they occur in sheathed bundles.