Nisha Vishwanathan

Borosins are ribosomally synthesized and post-translationally modified peptides (RiPPs) with α-N-methylations installed on the peptide backbone that impart unique properties like proteolytic stability to these natural products. The borosin RiPP family was initially reported only in fungi until our recent discovery and characterization of a Type IV split borosin system in the metal-respiring bacterium Shewanella oneidensis. Here, we used hidden Markov models and sequence similarity networks to identify over 1600 putative pathways that show split borosin biosynthetic gene clusters are widespread in bacteria. Noteworthy differences in precursor and α-N-methyltransferase open reading frame sizes, architectures, and core peptide properties allow further subdivision of the borosin family into six additional discrete structural types, of which five have been validated in this study.

ABSTRACTOne of the major challenges for the bioremediation application of microbial N2O reduction is its oxygen sensitivity. While a few strains were reported capable of reducing N2O under aerobic conditions, the N2O reduction kinetics of phylogenetically diverse N2O reducers are not well understood. Here we analyzed and compared the kinetics of Clade I and Clade II N2O-reducing bacteria in the presence or absence of O2by using a whole-cell assay with N2O and O2microsensors. Among the seven strains tested, N2O reduction ofStutzerimonas stutzeriTR2 and ZoBell were not inhibited by oxygen (i.e., oxygen tolerant).Paracoccus denitrificans, Azospirillum brasilense, andGemmatimonas aurantiacareduced N2O in the presence of O2but slower than in the absence of O2(i.e., oxygen sensitive). N2O reduction ofPseudomonas aeruginosaandDechloromonas aromaticadid not occur when O2was present (i.e., oxygen intolerant). Amino acid sequences and predicted structures of NosZ were highly similar among the...

Borosins are ribosomally synthesized and post-translationally modified peptides (RiPPs) with α-N-methylations installed on the peptide backbone that impart unique properties like proteolytic stability to these natural products. The borosin RiPP family was initially reported only in fungi until our recent discovery and characterization of a Type IV split borosin system in the metal-respiring bacterium Shewanella oneidensis. Here, we used hidden Markov models and sequence similarity networks to identify over 1,600 putative pathways that show split borosin biosynthetic gene clusters are widespread in bacteria. Noteworthy differences in precursor and α-N-methyltransferase open reading frame sizes, architectures, and core peptide properties allow further subdivision of the borosin family into six additional discrete structural types, of which five have been validated in this study.Abstract Figure