Isolation, Phylogenetic and Gephyromycin Metabolites Characterization of New Exopolysaccharides-Bearing Antarctic Actinobacterium from Feces of Emperor Penguin.

Hui-Min Gao,Xiao-Ling Zhang,Qiao Yang,Peng-Fei Xie

doi:10.3390/md19080458

Abstract

A new versatile actinobacterium designated as strain NJES-13 was isolated from the feces of the Antarctic emperor penguin. This new isolate was found to produce two active gephyromycin analogues and bioflocculanting exopolysaccharides (EPS) metabolites. Phylogenetic analysis based on pairwise comparison of 16S rRNA gene sequences showed that strain NJES-13 was closely related to Mobilicoccus pelagius Aji5-31T with a gene similarity of 95.9%, which was lower than the threshold value (98.65%) for novel species delineation. Additional phylogenomic calculations of the average nucleotide identity (ANI, 75.9–79.1%), average amino acid identity (AAI, 52.4–66.9%) and digital DNA–DNA hybridization (dDDH, 18.6–21.9%), along with the constructed phylogenomic tree based on the up-to-date bacterial core gene (UBCG) set from the bacterial genomes, unequivocally separated strain NJES-13 from its close relatives within the family Dermatophilaceae. Hence, it clearly indicated that strain NJES-13 represented a putative new actinobacterial species isolated from the gut microbiota of mammals inhabiting the Antarctic. The obtained complete genome of strain NJES-13 consisted of a circular 3.45 Mb chromosome with a DNA G+C content of 67.0 mol%. Furthering genome mining of strain NJES-13 showed the presence of five biosynthetic gene clusters (BGCs) including one type III PKS responsible for the biosynthesis of the core of gephyromycins, and a series of genes encoding for bacterial EPS biosynthesis. Thus, based on the combined phylogenetic and active metabolites characterization presented in this study, we confidently conclude that strain NJES-13 is a novel, fresh actinobacterial candidate to produce active gephyromycins and microbial bioflocculanting EPS, with potential pharmaceutical, environmental and biotechnological implications.

Highlights

Actinobacteria are a unique prokaryote group and a virtually unlimited source due to their extraordinary abilities to deliver a multitude of novel bioactive lead compounds with medical, pharmaceutical, industrial and ecological significance [1,2]
We present the isolation of a novel versatile actinobacterium designated strain NJES-13 from the feces of antarctic emperor penguin
Cells of strain NJES-13 were observed to form yellow colonies when grown on marine R2A plates at 28 ◦C for 2 days

Summary

Introduction

Actinobacteria are a unique prokaryote group and a virtually unlimited source due to their extraordinary abilities to deliver a multitude of novel bioactive lead compounds with medical, pharmaceutical, industrial and ecological significance [1,2]. They are widespread in nature and have been recovered from a wide variety of terrestrial or aquatic habitats, as saprophytes, symbionts or pathogens [3]. The family Dermatophilaceae was first described by Van Saceghem in 1915 with Dermatophilus as the genus [5] This family was reclassified into the newly proposed order Dermatophilales in the newly proposed class Actinobacteria [6]. No bacterial strain belonging to this family has been reported from the Antarctic habitat yet

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Conclusion