AUTHOR=Zheng Yu , Saitou Ayana , Wang Chiung-Mei , Toyoda Atsushi , Minakuchi Yohei , Sekiguchi Yuji , Ueda Kenji , Takano Hideaki , Sakai Yasuteru , Abe Keietsu , Yokota Akira , Yabe Shuhei 

TITLE=Genome Features and Secondary Metabolites Biosynthetic Potential of the Class Ktedonobacteria

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00893

DOI=10.3389/fmicb.2019.00893

ISSN=1664-302X

ABSTRACT=<p>The prevalence of antibiotic resistance and the decrease in novel antibiotic discovery in recent years necessitates the identification of potentially novel microbial resources to produce natural products. <italic>Ktedonobacteria</italic>, a class of deeply branched bacterial lineage in the ancient phylum <italic>Chloroflexi</italic>, are ubiquitous in terrestrial environments and characterized by their large genome size and complex life cycle. These characteristics indicate <italic>Ktedonobacteria</italic> as a potential active producer of bioactive compounds. In this study, we observed the existence of a putative “megaplasmid,” multiple copies of ribosomal RNA operons, and high ratio of hypothetical proteins with unknown functions in the class <italic>Ktedonobacteria</italic>. Furthermore, a total of 104 antiSMASH-predicted putative biosynthetic gene clusters (BGCs) for secondary metabolites with high novelty and diversity were identified in nine <italic>Ktedonobacteria</italic> genomes. Our investigation of domain composition and organization of the non-ribosomal peptide synthetase and polyketide synthase BGCs further supports the concept that class <italic>Ktedonobacteria</italic> may produce compounds structurally different from known natural products. Furthermore, screening of bioactive compounds from representative <italic>Ktedonobacteria</italic> strains resulted in the identification of broad antimicrobial activities against both Gram-positive and Gram-negative tested bacterial strains. Based on these findings, we propose the ancient, ubiquitous, and spore-forming <italic>Ktedonobacteria</italic> as a versatile and promising microbial resource for natural product discovery.</p>