Research Papers:
Comparative genome analysis of Streptococcus iniae DX09 reveals new insights into niche adaptation and competitive host colonisation ability
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Tao Liu1,2,*, Yajun Wang1,4,* and Kaiyu Wang1,3
1Department of Basic Veterinary, Veterinary Medicine College, Sichuan Agricultural University, Sichuan, Chengdu 611134, P.R. China
2Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Sichuan, Chengdu 611134, P.R. China
3Department of Aquaculture, College of Animal Science & Technology, Sichuan Agricultural University, Sichuan 611134, Cheng’du, P.R. China
4Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Key Laboratory of Fishery Drug Development, Ministry of Agriculture, Key Laboratory of Aquatic Animal Immune Technology, Guangzhou 510380, Guangdong, P.R. China
*These authors contributed equally to this work
Correspondence to:
Kaiyu Wang, email: [email protected]
Keywords: Streptococcus iniae; whole-genome sequencing; comparative genome analysis; pathogenic
Received: September 22, 2017 Accepted: December 01, 2017 Published: December 08, 2017
ABSTRACT
Streptococcus iniae is a significant pathogen in a variety of marine and freshwater cultured fish species. Previous investigations on S. iniae have been limited to a single virulence gene or genome. However, different strains are associated with varying pathogenicity and niche adaptation properties. For comprehensive characterization of the genetic variations in S. iniae, whole-genome sequencing of S. iniae DX09 (isolated from diseased catfish) was performed and comparative genome analysis with eight S. iniae strains conducted to determine the virulence evolution patterns. Comparative analysis of all sequenced S. iniae revealed genome-genome variations, mainly in two plasticity zones, within genes encoding specific functions, such as the Ess/type VII secretion system and phosphoenolpyruvate-carbohydrate phosphotransferase system, reflecting adaptation to colonisation of specific host habitats. The plasticity zones analyzed in the S. iniae genome may be a paradigm rather than a unique combination of horizontal gene transfer and underlie the emergence of pathogenic Gram-positive bacteria.