Antibody selections were performed against L. acidophilus using two methods. In the first, the bacteria were coated on Immunotubes (Nunc),

while, in the second, selection was carried out by centrifugation. For each selection we used a previously described naïve scFv library displayed on M13 filamentous phage [36]. Two to three rounds of selection, with increasing stringency, were performed prior to re-cloning enriched scFvs into pEP-GFP11 CHIR-99021 order [37] for screening. This vector generates scFv proteins in fusion with two different detection tags: SV5, recognized by a monoclonal antibody [38] and S11, a split green fluorescent protein (GFP) tag that fluoresces when complemented with GFP1-10 [39]. The simultaneous use of both tags enhances signal-to-noise ratio when testing putative clones for binding activity against L. acidophilus in flow cytometry. ScFv culture supernatant was incubated with L. acidophilus followed by staining and the L. acidophilus bacteria analyzed using an LSRII flow cytometer (Becton Dickinson). Sequencing revealed one unique scFv (α-La1) from the immunotube selection, and three unique scFvs (α-La2, α-La3, and α-La4) from the selection by centrifugation (Additional file 1). The α-La1 selleck inhibitor scFv was found to be highly specific for L.

acidophilus, binding to all tested L. acidophilus strains (ATCC strains 4356 and 832), but not to a panel of other gut bacteria, including Bifidobacterium sp., Peptoniphilus sp., E. coli, and six different species of Lactobacillus (Figure 1 and Table 1). Our analysis this website included Lactobacillus helveticus, the closest species to L. acidophilus, the 16S rRNA sequence of which shares >98% identity [40]. The other three α-La scFvs showed similar degrees of specificity. We proceeded with the α-La1 scFv for the remainder of the study due to greater expression and apparent

affinity relative to the other α-La scFvs (Additional file 2). The specificity of the α-La1 scFv was also further validated using the AMNIS Image-Stream Mark II flow cytometer (Amnis Corporation), which captures microscope images in a flow cytometric configuration (Figure 1B). Figure 1 A phage display derived single chain fragment (scFv) was selected that binds Lactobacillus acidophilus (L.a.) specifically. Various bacterial species (see Table 1 for abbreviations) were mixed with the α-La scFv-SV5-GFP-s11 fusion protein and stained with α-SV5-IgG-PE and/or GFP1-10. Binding specificity was confirmed using both standard (A) and imaging (B) flow cytometry (BF = Bright Field, GFP = Green Fluorescent Protein, PE = Phycoerytherin).