Degradation of Multiple Peptides by Microcystin-Degrader Paucibacter toxinivorans (2C20)

Abstract

Since conventional drinking water treatments applied in different countries are inefficient at eliminating potentially toxic cyanobacterial peptides, a number of bacteria have been studied as an alternative to biological filters for the removal of microcystins (MCs). Here, we evaluated the degradation of not only MCs variants (-LR/DM-LR/-RR/-LF/-YR), but also non-MCs peptides (anabaenopeptins A/B, aerucyclamides A/D) by Paucibactertoxinivorans over 7 days. We also evaluated the degradation rate of MC-LR in a peptide mix, with all peptides tested, and in the presence of M. aeruginosa crude extract. Furthermore, biodegradation was assessed for non-cyanobacterial peptides with different chemical structures, such as cyclosporin A, (Glu1)-fibrinopeptide-B, leucine-enkephalin, and oxytocin. When cyanopeptides were individually added, P. toxinivorans degraded them (99%) over 7 days, except for MC-LR and -RR, which decreased by about 85 and 90%, respectively. The degradation rate of MC-LR decreased in the peptide mix compared to an individual compound, however, in the presence of the Microcystis extract, it was degraded considerably faster (3 days). It was noted that biodegradation rates decreased in the mix for all MCs while non-MCs peptides were immediately degraded. UPLC–QTOF–MS/MS allowed us to identify two linear biodegradation products for MC-LR and MC-YR, and one for MC-LF. Furthermore, P. toxinivorans demonstrated complete degradation of non-cyanobacterial peptides, with the exception of oxytocin, where around 50% remained after 7 days. Thus, although P. toxinivorans was previously identified as a MC-degrader, it also degrades a wide range of peptides under a range of conditions, which could be optimized as a potential biological tool for water treatment.

Quantification of microcystin production and biodegradation rates in the western basin of Lake Erie

“…The literature on bacteria‐mediated microcystin degradation dates back to the 1990s (Jones et al 1994; Dziga et al 2017), and two primary pathways, the mlr + and mlr − , have been identified for microcystin biodegradation (Bourne et al 2001; Santos et al 2021). The mlr + biodegradation has been linked genetically to Sphingophyxis sp.…”

The Western Lake Erie Culture Collection: A promising resource for evaluating the physiological and genetic diversity ofMicrocystisand its associated microbiome

“…Additionally, most cultures lack mcy genes and MC producing potential, but still encode for the synthesis of other secondary metabolites (Fig 3). A recent study has demonstrated the ability of mlr -bacteria to degrade both MCs and other cyanobacterial peptides (Santos et al, 2021) suggesting that associated bacteria within the WLECC may be capable of degrading other cyanopeptides beside MC through unknown pathways. Future research should address the substrate specificity of mlr- encoded enzymes, as well as cryptic pathways beyond mlr that can degrade MCs and/or other cyanobacterial peptides.…”