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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Cell. Infect. Microbiol. | doi: 10.3389/fcimb.2019.00183

A first study of the virulence potential of a Bacillus subtilis isolate from deep-sea hydrothermal vent

  • 1Key Laboratory of Experimental Marine Biology, Institute of Oceanology (CAS), China
  • 2Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, China
  • 3University of Chinese Academy of Sciences (UCAS), China

Bacillus subtilis is the best studied Gram-positive bacterium, primarily as a model of cell differentiation and industrial exploitation. To date, little is known about the virulence of B. subtilis. In this study, we examined the virulence potential of a B. subtilis strain (G7) isolated from the Iheya North hydrothermal field of Okinawa Trough. G7 is aerobic, motile, endospore-forming, and requires NaCl for growth. The genome of G7 is composed of one circular chromosome of 4,216,133 base pairs with an average GC content of 43.72%. G7 contains 4,416 coding genes, 27.5% of which could not be annotated, and the remaining 72.5% were annotated with known or predicted functions in 25 different COG categories. Ten sets of 23S, 5S, and 16S ribosomal RNA operons, 86 tRNA and 14 sRNA genes, 50 tandem repeats, 41 mini-satellites, one microsatellite, and 42 transposons were identified in G7. Comparing to the genome of the B. subtilis wild type strain NCIB 3610T, G7 genome contains many genomic translocations, inversions, and insertions, and twice the amount of genomic Islands (GIs), with 42.5% of GI genes encoding hypothetical proteins. G7 possesses abundant putative virulence genes associated with adhesion, invasion, dissemination, anti-phagocytosis, and intracellular survival. Experimental studies showed that G7 was able to cause mortality in fish and mice following intramuscular/intraperitoneal injection, resist the killing effect of serum complement, and replicate in mouse macrophages and fish peripheral blood leukocytes. Taken together, our study indicates that G7 is a B. subtilis isolate with unique genetic features and can be lethal to vertebrate animals once being introduced into the animals by artificial means. These results provide the first insight into the potential harmfulness of deep-sea B. subtilis.

Keywords: Bacillus subtilis, deep-sea, hydrothermal vent, Genome, Virulence

Received: 10 Dec 2018; Accepted: 13 May 2019.

Edited by:

Vincenzo Scarlato, Department of Pharmacy and Biotechnology, University of Bologna, Italy

Reviewed by:

Marcelo Brocchi, Campinas State University, Brazil
Andrea Vannini, University of Bologna, Italy  

Copyright: © 2019 Gu, Sun, Luo, Zhang and Sun. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Li Sun, Key Laboratory of Experimental Marine Biology, Institute of Oceanology (CAS), Qingdao, 266071, Shandong Province, China, lsun@qdio.ac.cn