Improving key gene expression and di-n-butyl phthalate (DBP) degrading ability in a novel Pseudochrobactrum sp. XF203 by ribosome engineering.

Di-n-butyl phthalate (DBP) is one of the important phthalates detected commonly in soils and crops, posing serious threat to human health. Pseudochrobactrum sp. XF203 (XF203), a new strain related with DBP biodegradation, was first identified from a natural habitat lacking human disturbance. Genomic analysis coupled with gene expression comparison assay revealed this strain harbors the key aromatic ring-cleaving gene catE203 (encoding catechol 2,3-dioxygenase/C23O) involved DBP biodegradation. Following intermediates identification and enzymatic analysis also indicated a C23O dependent DBP lysis pathway in XF203. The gene directed ribosome engineering was operated and to generate a desirable mutant strain XF203R with highest catE203 gene expression level and strong DBP degrading ability. The X203R removed DBP in soil jointly by reassembling bacterial community. These results demonstrate a great value of XF203R for the practical DBP bioremediation application, highlighting the important role of the key gene-directed ribosome engineering in mining multi-pollutants degrading bacteria from natural habitats where various functional genes are well conserved.

[Advances in the biosynthesis of cyclodipeptide type natural products derived from actinomycetes].

Cyclodipeptide (CDP) composed of two amino acids is the simplest cyclic peptide. These two amino acids form a typical diketopiperazine (DKP) ring by linking each other with peptide bonds. This characteristic stable ring skeleton is the foundation of CDP to display extensive and excellent bioactivities, which is beneficial for CDPs' pharmaceutical research and development. The natural CDP products are well isolated from actinomycetes. These bacteria can synthesize DKP backbones with nonribosomal peptide synthetase (NRPS) or cyclodipeptide synthase (CDPS). Moreover, actinomycetes could produce a variety of CDPs through different enzymatic modification. The presence of these abundant and diversified catalysis indicates that actinomycetes are promising microbial resource for exploring CDPs. This review summarized the pathways for DKP backbones biosynthesis and their post-modification mechanism in actinomycetes. The aim of this review was to accelerate the genome mining of CDPs and their isolation, purification and structure identification, and to facilitate revealing the biosynthesis mechanism of novel CDPs as well as their synthetic biology design.