Such a result underpins the hypothesis that PssP2 may function at the connection between EPS unit assembly and its polymerization and transport. PssP was shown to be indispensable for EPS production and null mutants produced no detectable amounts of EPS. Mutants with a shortened PssP protein produced more LMW EPS, and mutants with shortened PssT or PssP2 – HMW EPS with higher molecular masses than in RtTA1. PssP2 overproduction in the mutant background led to a slight increase in the amount of LMW fractions than in the wild type. Taking into account the EPS phenotypes of pssP, pssT, and pssP2 mutants, the fact that PssP did not interact with glycosyltransferases, PssP and PssP2 formed heterocomplexes,Ionomycin and both interacted with PssT, we can speculate that PssP2 and PssP may serve opposite roles in determining the extent of EPS polymerization. EPS produced by Rhizobium is generally characterized by the presence of LMW and HMW fractions. The involvement of two similar proteins in EPS polymerization would resemble involvement of the two Wzz proteins in the bimodal distribution of Oag in S. flexneri. In this case, two versions of the protein: chromosomally and plasmidencoded are engaged. The chromosomal version is responsible for S-type Oag and the plasmid-encoded version of Wzz for VL-type Oag. It was Begacestat shown that these two Wzz proteins are differentially efficient and compete to control the degree of polymerization. Moreover, in S. meliloti different paralogs of ExoP co-polymerase are involved in controlling the production of LMW and HMW EPS I under different physiological conditions. Glycosyltransferases involved in synthesis of polysaccharides were shown to form a complex in the membrane. It was proposed that the complex might interact with a flippase and a copolymerase to regulate the length of produced chains. One of the key players in such an interaction in the case of R. leguminosarum might be the priming glycosyltransferase PssA, as the interaction with the co-polymerase could regulate the flow of subunits to the polymerization centre. Following this, PssP might bridge PssL and PssT and be involved in HMW polymerization, while PssP2 could serve as a linker between glycosyltransferases and the polymerization centre, but being involved in LMW polymerization.