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Role of the type III secretion system in a hypervirulent lineage of Bordetella bronchiseptica.

ABSTRACT: Despite the fact that closely related bacteria can cause different levels of disease, the genetic changes that cause some isolates to be more pathogenic than others are generally not well understood. We use a combination of approaches to determine which factors contribute to the increased virulence of a Bordetella bronchiseptica lineage. A strain isolated from a host with B. bronchiseptica-induced disease, strain 1289, was 60-fold more virulent in mice than one isolated from an asymptomatically infected host, strain RB50. Transcriptome analysis and quantitative reverse transcription-PCR showed that the type III secretion system (TTSS) genes were more highly expressed by strain 1289 than strain RB50. Compared to strain RB50, strain 1289 exhibited greater TTSS-mediated cytotoxicity of a mammalian cell line. Additionally, we show that the increase in virulence of strain 1289 compared to that of RB50 was partially attributable to the TTSS. Using multilocus sequence typing, we identified another strain from the same lineage as strain 1289. Similar to strain 1289, we implicate the TTSS in the increased virulence of this strain. Together, our data suggest that the TTSS is involved in the increased virulence of a B. bronchiseptica lineage which appears to be disproportionately associated with disease. These data are consistent with the view that B. bronchiseptica lineages can have different levels of virulence, which may contribute to this species' ability to cause different severities of respiratory disease.

SUBMITTER: Buboltz AM

PROVIDER: S-EPMC2738013 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Role of the type III secretion system in a hypervirulent lineage of Bordetella bronchiseptica.

Buboltz Anne M AM Nicholson Tracy L TL Weyrich Laura S LS Harvill Eric T ET

Infection and immunity 20090713 9

Despite the fact that closely related bacteria can cause different levels of disease, the genetic changes that cause some isolates to be more pathogenic than others are generally not well understood. We use a combination of approaches to determine which factors contribute to the increased virulence of a Bordetella bronchiseptica lineage. A strain isolated from a host with B. bronchiseptica-induced disease, strain 1289, was 60-fold more virulent in mice than one isolated from an asymptomatically ...[more]

PMID: 19596779

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Project description:Bordetella pertussis uses a type III secretion system (T3SS) to inject virulence proteins into host cells. Although the B. pertussis T3SS was presumed to be involved in host colonization, efficient secretion of type III secreted proteins from B. pertussis has not been observed. To investigate the roles of type III secreted proteins during infection, we attempted to optimize culture conditions for the production and secretion of a type III secreted protein, BteA, in B. pertussis We observed that B. pertussis efficiently secretes BteA in ascorbic acid-depleted (AsA-) medium. When L2 cells, a rat lung epithelial cell line, were infected with B. pertussis cultured in the AsA- medium, BteA-dependent cytotoxicity was observed. We also performed an immunofluorescence assay of L2 cells infected with B. pertussis Clear fluorescence signals of Bsp22, a needle structure of T3SS, were detected on the bacterial surface of B. pertussis cultured in the AsA- medium. Since ascorbic acid is known as a reducing agent, we cultured B. pertussis in liquid medium containing other reducing agents such as 2-mercaptoethanol and dithioerythritol. Under these reducing conditions, the production of type III secreted proteins was repressed. These results suggest that in B. pertussis, the production and secretion of type III secreted proteins are downregulated under reducing conditions.IMPORTANCE The type III secretion system (T3SS) of Bordetella pertussis forms a needlelike structure that protrudes from the bacterial cell surface. B. pertussis uses a T3SS to translocate virulence proteins called effectors into host cells. The culture conditions for effector production in B. pertussis have not been investigated. We attempted to optimize culture medium compositions for producing and secreting type III secreted proteins. We found that B. pertussis secretes type III secreted proteins in reducing agent-deprived liquid medium and that BteA-secreting B. pertussis provokes cytotoxicity against cultured mammalian cells. These results suggest that redox signaling is involved in the regulation of B. pertussis T3SS.

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Role of the type III secretion system in a hypervirulent lineage of Bordetella bronchiseptica.

Publications

Role of the type III secretion system in a hypervirulent lineage of Bordetella bronchiseptica.

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