# Wastewater Treatment with Bacterial Representatives of the _Thiothrix_ Morphotype
## 3 Methods for Identification of _Thiothrix_ in Wastewater Treatment Plants
### Enhanced Biological Removal of Phosphorus
MQ and MQH\({}_{2}\)—oxidized and reduced forms of menaquinone, respectively; NarI, NarH and NarG—distimulatory nitrate reductase (Nar) subunits with a cytoplasmically oriented active center; \(b_{L}\) and \(b_{H}\)—low-potential and high-potential cytochrome \(b\) in the membrane-spanning NarI subunit; [3 Fe-4S] and [4 Fe-4S]—redox-active iron-sulfur clusters; arrows within Nar subunits indicate the electron pathway between the redox groups. Insets: in the black dashed line on the right side of the figure—the direction of electrical potential at the cytoplasmic membrane, which is charged negatively at the cytoplasmic side and positively at the periplasmic side during the process of nitrogen respiration; in the blue dashed line in the upper left part of the figure—reactions occurring inside the cytoplasmic membrane. Figure is based on [PERSON] et al. [56], [PERSON] et al. [105]; [PERSON] et al. [111]; and [PERSON] et al. [106] under the terms of the Creative Commons Attribution 4.0 International License. _'Ca._ Thiothrix singaporensis' derived from laboratory EBPR, as well as in the genomes of _T. lacustris_ BLT, _T. calafiontis_ G1T and _T. nivea_ JP2T, the genes _phoURB_ and _pstSACB_, encoding the systems of signaling regulation and the transport of inorganic phosphate into the cell, and the genes _ppk1_ and _epp_, whose products catalyze poly-P synthesis and degradation, were identified [56]. [PERSON] et al. documented the visual mass accumulation of poly-P inclusion granules in the cells of _T. calafiontis_, corroborated by data on the presence of gene _ppk2_ in its genome [47]. To date, we have detected the presence of multiple genes _ppk2_ in the available genomes of the most identified species of the genus _Thiothrix_ (in the following, access to only one of several genes in each species is shown), namely _T. uuzii_ A1T [QTR55213.1] [94], _T. fructsoivorans_ QT [QTX11709.1] [94], _Thiothrix subterranea_ Ku-5T [WML89006.1] [19], _'Ca._ Thiothrix putei' [WGZ96527.1] [5], _'Ca._ Thiothrix singaporensis' [QLQ34282.1] [114], _T. lacustris_ BLT [WML90248.1] [19], _T. nivea_ JP2T [EI]34895.1], _T. litoralis_ AST [QTR45363.1] [94], _'Ca._ Thiothrix anitrata' A52 [QTR51311.1] [94], _'Ca._ Thiocaldithrix sulfatifiontis' [UOG93965.1] [55], _T. winogradskyi_ CT3T [UJS26581.1] [55], _'Ca._ Thiothrix sp. Deng01' [WP_324693012.1] [115] and a number of unidentified _Thiothrix_ species, as well as the members of the other _Thiothricaceae_ genera, _'Ca._ Thiocaldithrix dubininis' [WGZ92350.1] [5], _Thiothrix facile_ DSM 14,609 (formerly _Thiothrix flexilis_) [ARCL01000001.1] and _Thiolinee eikelboomii_ (formerly _Thiothrix eikelboomii_) [SKA88474.1]. According to [PERSON] et al., _Thiothrix disciformis_ (= _Thiolinea disciformis_) possesses genes for the major systems of phosphate metabolism (_ppk_, _ppx_, _pst_ and _pit_), which include two different phosphate transport systems, Pst and Pit, with high and low affinity for phosphate [11]. A metagenomic analysis performed by the research group of [PERSON] et al. also showed that the identified representatives of the genus _Thiothrix_ have the genes of phosphate transport, _pit_ and _phmcDE_ and other genes of phosphate metabolism: _phoURB_, _pst_, _ppk_[49]. Most recently, [PERSON] et al. reported that the genes encoding the systems of Pi transport into the cell (_pstDCABS_) and the signaling regulation of phosphate transport (_phoURB_), as well as the systems of poly-P synthesis and degradation, namely polyphosphate kinase (_ppk1_) and exopolyphosphatase (_ppx_), were found in the MAG-assembled genome of _'Ca._ Thiothrix namsaraei', a new member of the genus _Thiothrix_ from Lake Baikal [84]. [PERSON] et al. identified genes pstDCABS, phoURB and _epp_, as well as genes _ppk1_ and _pap_, for poly-P synthesis and hydrolysis in three species of _Thiothrix_, _T. subterranea_ sp. nov. Ku-5, _T. litoralis_ sp. nov. AS and _'Ca._ Thiothrix anitrata' sp.