Identification of conditionally essential genes for Streptococcus suis infection in pigs

Abstract

Streptococcus suis is a Gram-positive bacterium and zoonotic pathogen that causes meningitis and sepsis in pigs and humans. The aim of this study was to identify genes required for S. suis infection. We created Tn-Seq libraries in a virulent S. suis strain 10, which was used to inoculate pigs in an intrathecal experimental infection. Comparative analysis of the relative abundance of mutants recovered from different sites of infection (blood, cerebrospinal fluid, and meninges of the brain) identified 361 conditionally essential genes, i.e. required for infection, which is about 18% of the genome. The conditionally essential genes were primarily involved in metabolic and transport processes, regulation, ribosomal structure and biogenesis, transcription, and cell wall membrane and envelope biogenesis, stress defenses, and immune evasion. Directed mutants were created in a set of 10 genes of different genetic ontologies and their role was determined in ex vivo models. Mutants showed different levels of sensitivity to survival in whole blood, serum, cerebrospinal fluid, thermic shock, and stress conditions, as compared to the wild type. Additionally, the role of three selected mutants was validated in co-infection experiments in which pigs were infected with both wild type and isogenic mutant strains. The genetic determinants of infection identified in this work contribute to novel insights in S. suis pathogenesis and could serve as targets for novel vaccines or antimicrobial drugs.

FASTQINS and ANUBIS: two bioinformatic tools to explore facts and artifacts in transposon sequencing and essentiality studies

“…After several rounds of division, cells in which an E gene has been disrupted will disappear from the population and only NE genes will have insertions. Remarkably, essentiality in an organism may vary between different genetic and/or environmental conditions like during infection ( 5 ). Transposon insertion sites are commonly identified by ultra-deep sequencing in a technique known as Transposon sequencing (Tn-seq) ( 6–8 ).…”

Identification and characterization of the cell division protein MapZ from Streptococcus suis

“…The putative mapZ gene of strain 10 had been previously identified as a conditionally essential gene for survival in the blood (Arenas et al, 2020 ). Alignment of the predicted MapZ protein of strain 10 revealed an overall homology of 40% with S .…”

“…Its isogenic mapZ ‐deficient mutant, hereafter called 10∆ mapZ , was constructed by the insertion of a spectinomycin cassette in the corresponding putative mapZ gene (locus tag GPW51_RS02050). The generation of mutants in strain 10 has been previously described (Arenas et al, 2020 ). In brief, a spectinomycin‐resistance cassette and the flanking regions of the mapZ gene were amplified from the genomic DNA of strain 10.…”

“…In a recent study using intrathecal infection of pigs with a transposon library of S. suis, the locus SSU0375 was identified as conditionally essential for survival in the blood (Arenas et al, 2020). Its predicted protein sequence shows homologies with the mid-cellanchored protein Z of S. pneumoniae.…”

A Markerless Gene Deletion System in Streptococcus suis by Using the Copper-Inducible Vibrio parahaemolyticus YoeB Toxin as a Counterselectable Marker

“…A number of virulence-related factors have been described in S. suis [15,16]. Recently, in vivo transcriptomes and transposon mutant libraries have been applied to identify genes involved in the virulence traits of S. suis [17][18][19]. Usually, studies related to the physiology and pathogenesis of S. suis rely on gene deletion mutants.…”