Identification and characterization of novel virulence factors of Staphylococcus aureus USA300 using silkworm model.

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K16653
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 49050:Bacteriology-related
• Research Institution: Hokkaido University (2020-2021); Teikyo University (2019)
• Principal Investigator: Paudel Atmika 北海道大学, 人獣共通感染症国際共同研究所, 助教 (80832774)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: pathogenesis / virulence / virulence factor / silkworm / infection / Bombyx mori / Bacillus cereus

Outline of Final Research Achievements

We screened Nebraska Transposon Mutant Library of USA300 and found that 8 mutants with reduced virulence in silkworm and mice infection models. The pathogenicity was not restored by introduction of one of the genes: yjbI, while the introduction of the downstream gene yjbH complemented the pathogenicity in silkworms and mice. RNA-seq analysis of yjbI::Tn and yjbH::Tn mutants revealed that disruption of both genes significantly affected the expression of > 200 genes including downregulation of several virulence genes. We,theb, established silkworm infection models of Bacillus anthracis and B. cereus. Constructing a mutant library of Bacillus cereus, we found one gene X to have role in virulence in silkworm. We then used the mutants with transposon inserted in the gene X from the NTML library of S. aureus and found that the disruption of the gene X made S. aureus hyper virulent. Thus, we found that although the gene was conserved among S. aureus and B. cereus and had role in virulence.

Free Research Field

Bacteriology

Academic Significance and Societal Importance of the Research Achievements

The research identified novel virulence factors of a Gram-positive bacteria, methicillin-resistant Staphylococcus aureus, using silkworm infection model and deepened our understanding of its pathogenicity.