| Autor: |
Velásquez JC; Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile., Hidalgo AA; Laboratorio de Patogénesis Molecular y Antimicrobianos, Facultad de Medicina, Universidad Andres Bello, Echaurren 183, Santiago, Chile., Villagra N; Laboratorio de Patogénesis Molecular y Antimicrobianos, Facultad de Medicina, Universidad Andres Bello, Echaurren 183, Santiago, Chile., Santiviago CA; Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santos Dumont 964, Independencia, Santiago, Chile., Mora GC; Laboratorio de Patogénesis Molecular y Antimicrobianos, Facultad de Medicina, Universidad Andres Bello, Echaurren 183, Santiago, Chile., Fuentes JA; Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile. |
| Abstrakt: |
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. |
