The biotechnological relevance of Rhodococcus rhodochrous. The complete genomic sequence of nitrile biocatalyst strain ATCC BAA-870

Background Rhodococci are industrially important soil-dwelling Gram-positive bacteria that are well known for both nitrile hydrolysis and oxidative metabolism of aromatics. Rhodococcus rhodochrous ATCC BAA-870 is capable of metabolising a wide range of aliphatic and aromatic nitriles and amides. The expressed nitrilase, nitrile hydratase and amidase activities have shown stereoselective preferences for beta-substituted nitrile compounds. The genome of the organism was sequenced and analysed in order to better understand this whole cell biocatalyst. Results The genome of R. rhodochrous ATCC BAA-870 is the first Rhodococcus genome fully sequenced using Nanopore sequencing. The circular genome contains 5.9 megabase pairs (Mbp) and includes a 0.53 Mbp linear plasmid, that together encode 7548 predicted protein sequences according to BASys annotation, and 5535 predicted protein sequences according to RAST annotation. The genome contains numerous oxidoreductases, 15 identified antibiotic and secondary metabolite gene clusters, and several terpene and nonribosomal peptide synthetase clusters, as well as 6 putative clusters of unknown type. The 0.53 Mbp plasmid encodes 677 predicted genes and contains the nitrile converting gene cluster. Based on COG functional categories of proteins using RAST annotation, the main distributions of predicted annotated genes belong to known subsystems encoding amino acids and derivatives (19.7%), carbohydrates (13.4%), fatty acids, lipids and isoprenoids (12.2%), and cofactors, vitamins, prosthetic groups and pigments (9.4%). However, 74% of RAST annotated genes are not assigned clear functional roles within known metabolic pathways, and 38% of genes are annotated as hypothetical. BASys annotation predicts that 55% of annotated genes have an unknown function. The R. rhodochrous ATCC BAA-870 genome contains one possible CRISPR, identified by CRISPRCasFinder. Conclusions The sequence and comprehensive description of the R. rhodochrous ATCC BAA-870 genome will facilitate the additional exploitation of rhodococci for biotechnological applications, as well as enable further characterisation of this model organism. The genome encodes a wide range of enzymes, many with unknown substrate specificities supporting potential applications in biotechnology, including monooxygenases, cytochrome P450s, reductases, proteases, lipases, and transaminases. The capacity of this strain to hydrolyse nitriles resides upon a plasmid, containing a nitrilase, a low molecular weight nitrile hydratase, and an enantioselective amidase.