Involvement of phosphoesterases in tributyl phosphate degradation in Sphingobium sp. strain RSMS

Abstract

A tri- and dibutyl phosphate (TBP/DBP) non-degrading spontaneous mutant, Sphingobium SS22, was derived from the Sphingobium sp. strain RSMS (wild type). Unlike the wild type strain, Sphingobium SS22 could not grow in a minimal medium supplemented with TBP or DBP as the sole source of carbon or phosphorous. Sphingobium SS22 also did not form any of the intermediates or end products of TBP or DBP degradation, namely DBP, butanol or inorganic phosphate. Proteomic analysis revealed the absence of three prominent proteins in Sphingobium SS22 as compared to wild type. These proteins were identified by MALDI mass spectrometry, and they showed similarities to phosphohydrolase- and exopolyphosphatase-like proteins from other bacteria, which belong to the class of phosphoesterases. Cellular proteins of Sphingobium SS22 showed none or negligible phosphodiesterase (PDE) and phosphomonoesterase (PME) activities at pH 7 and displayed approximately five- and approximately twofold less DBP and monobutyl phosphate (MBP) degradation activity, respectively, in comparison to the wild type strain. In-gel zymographic analysis revealed two PDE and PME activity bands in the wild type strain, one of which was absent in the Sphingobium SS22 mutant. The corresponding proteins from the wild type strain could degrade DBP and MBP. The results demonstrate the involvement of phosphoesterase enzymes in the TBP degradation pathway elucidated earlier.

Response of soil bacteria to PUREX chemicals suggests biomarker utility and bioremediation potential

“…It is best characterized in Sphingomonas sp. RSMS (25,26), which is clearly distinct from the incomplete pathway characterization for Rhodopseudomonas palustris (24). As a result, the phosphostriesterase genes we observed as potentially involved with tributyl phosphate degradation may represent a novel pathway.…”

“…RSMS (25). Therefore, we focused on phosphoesterase genes which may be involved in degrading tributyl phosphate to dibutyl phosphate (phosphotriesterases), dibutyl phosphate to monobutyl phosphate (phosphodiesterases) and monobutyl phosphate to butanol and inorganic phosphate (phosphomonoesterase or acid phosphatase) (25,26). Potential phosphtriesterases were identified, and their distribution across MAGs supports their role in promoting growth in response to tributyl phosphate.…”

Microbe-assisted biodegradation, bioremediation and metabolic engineering

“…strain RSMS, capable of degrading tributyl phosphate (TBP) and utilizing it as carbon and phosphorus source resulting in complete mineralization of this recalcitrant organic solvent of U and Pu in nuclear industry (Rangu et al, 2014). The biochemical pathway of TBP degradation was elucidated and techniques developed to simultaneously degrade TBP and use the phosphate released for precipitation of traces of uranium still present in TBP (Rangu et al, 2016).…”

Isolation and characterization of a recombinant class C acid phosphatase from Sphingobium sp. RSMS strain

“…Sphingobium sp. RSMS strain has been identified for its ability to degrade TBP efficiently [16] . The final products of TBP degradation are n-butanol and inorganic phosphate.…”

“…These are phosphotriesterase, phosphodiesterase and phosphomonoesterase (popularly called as phosphatases), which sequentially catalyze the conversion of TBP to dibutyl phosphate (DBP), DBP to monobutyl phosphate (MBP) and MBP to n-butanol and inorganic phosphate, respectively. So far, the genetic pathway for TBP degradation has not been identified in any of the TBP-degrading bacteria [ [16] , [18] ].…”