Micromonospora zhangzhouensis sp. nov., a Novel Actinobacterium Isolated from Mangrove Soil, Exerts a Cytotoxic Activity in vitro

Geyi Fu,Huan Qi,Min Wu,Ruijun Wang,Hui Zhang,Jinglin Ding,Jidong Wang,Zhenglian Xue,Zhe Zhao,Can Chen

doi:10.1038/s41598-020-60677-0

Abstract

A new bacterial strain, designated HM134T, was isolated from a sample of soil collected from a Chinese mangrove Avicennia marina forest. Assessed by a polyphasic approach, the taxonomy of strain HM134T was found to be associated with a range of phylogenetic and chemotaxonomic properties consistent with the genus Micromonospora. Phylogenetic analysis based on the 16s rRNA gene sequence indicated that strain HM134T formed a distinct lineage with the most closely related species, including M. rifamycinica AM105T, M. wenchangensis CCTCC AA 2012002T and M. mangrovi 2803GPT1-18T. The ANI values between strain HM134T and the reference strains ranged from 82.6% to 95.2%, which was below the standard criteria for classifying strains as the same species (96.5%). Strain HM134T and related species shared in silico dDDH similarities values below the recommended 70% cut-off for the delineation of species (range from 25.7–62.6%). The DNA G+C content of strain HM134T was 73.2 mol%. Analysis of phylogenetic, genomic, phenotypic and chemotaxonomic characteristics revealed that strain HM134T is considered to represent a novel species of the genus Micromonospora, for which the name M. zhangzhouensis sp. nov. is proposed. The extract of strain HM134T was demonstrated to exhibit cytotoxic activity against the human cancer cell lines HepG2, HCT-116 and A549. Active substance presented in the fermentation broth of strain HM134T was isolated by bioassay-guided analysis and purified afterwards. A new derivative of diterpenoid was identified through electrospray ionizing mass spectrometry (MS) and nuclear magnetic resonance (NMR). The compound showed different cytotoxic activities against cancer cells, with the highest cytotoxicity against HCT-116, corresponding to IC50 value of 38.4 μg/mL.

Highlights

The genus Micromonospora, which belongs to the family Micromonosporaceae was first proposed by Ørskov[1] with Micromonospora chalcea as its type species
According to the neighbor-joining, maximum-parsimony and maximum-like methods, strain HM134T stably formed a distinct lineage with the following related species: M. rifamycinica AM105T, M. wenchangensis CCTCC AA 2012002T and M. mangrovi 2803GPT1-18T
The phylogentic tree using ARB program indicated that strain HM134T fell in the clade with M. wenchangensis CCTCC AA 2012002T and M. rifamycinica AM105T

Summary

Introduction

The genus Micromonospora, which belongs to the family Micromonosporaceae was first proposed by Ørskov[1] with Micromonospora chalcea as its type species. Strains representing species of the genus Micromonospora have been recognized as important sources of bioactive secondary metabolites: gentamicin, sagamicin, sisomicin, verdamicin, everninomicin, lupinacidins A-C, netamicin, tetrocracin A, diazepinomicin and yangpumicin[11,12,23,24]. These findings suggested that the genus Micromonospora should remain a focus of research for the discovery of new bioactive metabolites. A novel strain of the genus Micromonospora collected from the rhizosphere soil of the mangrove in Fujian, China was discovered. The extract from this novel strain exerted antitumor activity, in addition the activity compound present in the extract was characterized

Methods

Results

Conclusion