SPI-9 of Salmonella enterica serovar typhi is constituted by an operon positively regulated by RpoS and contributes to adherence to epithelial cells in culture

Juan C. Velásquez, Alejandro A. Hidalgo, Nicolás Villagra, Carlos A. Santiviago, Guido C. Mora, Juan A. Fuentes

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

The genomic island 9 (SPI-9) from Salmonella enterica serovar Typhi (S. Typhi) carries three ORFs (STY2876, STY2877, STY2878) presenting 98% identity with a type 1 secretory apparatus (T1SS), and a single ORF (STY2875) similar to a large RTX-like protein exhibiting repeated Ig domains. BapA, the Salmonella enterica serovar Enteritidis orthologous to S. Typhi STY2875, has been associated with biofilm formation, and is described as a virulence factor in mice. Preliminary in silico analyses revealed that S. Typhi STY2875 ORF has a 600 bp deletion compared with S. Enteritidis bapA, suggesting that S. Typhi STY2875 might be non-functional. At present, SPI-9 has not been studied in S. Typhi. We found that the genes constituting SPI-9 are arranged in an operon whose promoter was up-regulated in high osmolarity and low pH in a RpoS-dependent manner. All the proteins encoded by S. Typhi SPI-9 were located at the membrane fraction, consistent with their putative role as T1SS. Furthermore, SPI-9 contributed to adherence of S. Typhi to epithelial cells when bacteria were grown under high osmolarity or low pH. Under the test conditions, S. Typhi SPI-9 did not participate in biofilm formation. SPI-9 is functional in S. Typhi and encodes an adhesin induced under conditions normally found in the intestine, such as high osmolarity. Hence, this is an example of a locus that might be designated a pseudogene by computational approaches but not by direct biological assays.

Original languageEnglish
Pages (from-to)1367-1378
Number of pages12
JournalMicrobiology (United Kingdom)
Volume162
Issue number8
DOIs
Publication statusPublished - Aug 2016

ASJC Scopus subject areas

  • Microbiology

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