title: Capsule of Streptococcus equi subsp. zooepidemicus hampers the adherence and invasion of epithelial and endothelial cells and is attenuated during internalization.
abstract: Direct interaction between pathogens and host cells often is a prerequisite for colonization, infection and dissemination. Regulated production of capsular polysaccharide (CPS), which is made of hyaluronic acid, is essential for the pathogenicity of Streptococcus equi subsp. Zooepidemicus (SEZ). Here, we constructed a CPS-deleted mutant and analyzed it along with the parental wild-type strain in attachment and invasion of mammalian epithelial and endothelial cell lines. The CPS-deleted mutant exhibited significant increase in adherence and invasion by several orders of magnitude compared with the wild-type strain through quantitative analysis and electron microscopy observation. After the wild-type strain was recovered from invaded cells, its morphology was analyzed by visual methods and scanning electron microscopy, which revealed that its capsule was almost completely absent. Capsule measurements showed a similar result in which CPS production was nearly attenuated to the same extent as in the CPS-deleted mutant. qPCR assays revealed a marked reduction in the transcriptional levels of the CPS biosynthesis genes, has operon. Moreover, the repression in capsular production was stable inheritance. Our findings indicate that SEZ is a facultative intracellular bacterium, capsule attenuation in SEZ contributes to attachment and invasion in interactions with host cells, and the active regulation of capsule breakdown is controlled by SEZ during internalization.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Pei
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Yiqi
authors.initials: Y
authors.lastname: Su
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Ma
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, China fhj@njau.edu.cn.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Fan
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D016667:Bacterial Capsules / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D018938:Caco-2 Cells; D002460:Cell Line; D042783:Endothelial Cells / Q000382:microbiology*; D004847:Epithelial Cells / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D006820:Hyaluronic Acid; D008855:Microscopy, Electron, Scanning; D009876:Operon; D011135:Polysaccharides, Bacterial / Q000235:genetics / Q000378:metabolism; D018502:Streptococcus equi / Q000166:cytology / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*
chemical_list: D011135:Polysaccharides, Bacterial; D006820:Hyaluronic Acid
keywords: Streptococcus equi subsp. zooepidemicus; adherence; attenuation; capsule; invasion; morphology