Fig 2.
The GFP-positive fraction was represented mainly by one promoter construct. A mixed-inoculum pool (1:1:1:1:1:1:1) of WITS of S. Enteritidis having specific promoter constructs was used to infected a group of five streptomycin-pretreated C57BL/6 mice, whose cecal contents were analyzed at day 2 p.i. (A) Cecum samples were collected and suspended in 500 μl PBST solution. The suspension was diluted 1:100, passed through a 50-μm sieve, and FACS sorted to collect GFPPos and GFPNeg bacterial fractions from the third and fourth quadrants, respectively, during FACS sorting. The FACS was calibrated with a negative-control strain bearing plasmid pM968. (B) Relative WITS counts of GFPPos (●) and GFPNeg (○) fractions of cecal contents. Collected GFP fractions were enriched in LB medium supplemented with an appropriate antibiotic. Genomic DNA was isolated from the culture, and qPCR was performed for WITS. Most of the GFPPos fraction was represented by strain M1525/pM2155. *, P < 0.001 (Kruskal-Wallis test). (C) Statistics of FACS-sorted GFPPos and GFPNeg fractions obtained from cecal contents on a logarithmic scale showing higher expression of GFP through promoter construct pM2155 than the positive control pM975 in the mouse cecum.