## 9 Role of PPCs in the Molecular Adaptation of _Lactobacillus_ to Host Environments
#### 9.2.3 Surface and Moonlighting Proteins  
Analysis of differential whole-cell and surface proteomes of the probiotic _L. acidophilus_ NCFM strain revealed that ferulic acid, revextrol, tannic acid, and caffeic acid varied the abundance of moonlighting proteins engaged in adhesion [109] (Table 4). These profiles were associated with variations in the adhesive capacity of this strain triggered by these PPCs. The abundance of some of these moonlighting proteins including EF-P, pyruvate kinase, and EF-Tu correlated well with binding capabilities to HT-29 cells triggered by RSV or caffeic acid. Although adhesion capacities have not been tested in presence of rutin, _L. acidophilus_ NCFM also overexpressed EF-P and pyruvate kinase (as well as GAPDH and EF-G) in the presence of this flavonoid glycoside [45]. In this regard, the same positive correlation between rutin and _L. acidophilus_ adhesive capacity could be expected. However, it must be noted that abundance of GAPDH or EF-G did not fit with the good adhesion capacities of this strain stimulated by RSV or TA, respectively [109]. The expression of two moonlighting proteins implicated in adhesion, EF-GreA [110] (appregulated) and LuxS [111] (downregulated), was also of different tendency in response to tannic acid in _L. plantarum_ WCFSI [37] (Table 4). Overall, these results show that abundance of moonlighting proteins with potential adhesion capacity cannot always be directly correlated with improved adhesion induced by these PPCs, indicating that mutant approaches are necessary to complete these studies. Other candidate proteins with moonlighting functionality have been implicated in adhesion to host cells [112; 113; 114]. Among these, the oligopeptide-binding protein Opp [115] or some molecular chaperones [116; 117; 118], are markedly induced in presence of some PPCs. The _oppA_ gene is markedly overexpressed in the presence of _p_-CA or OLE (Table 4). GroEL and small heat-shock proteins (HSPs) are induced by several PPCs (Table 4) and even though these proteins participate in the binding of _L. johnsonii_ and _L. plantarum_ WCFSI to host cells, respectively, adhesion assays in the presence of PPCs and mutant approaches are also required to show which among these moonlighting proteins induced by specific PPCs improve the adhesion to host cells. The _msa_ gene from _L. plantarum_ encodes a mannose-specific adhesion factor [67] that is overexpressed in the presence of RSV (Table 4). Since improved adhesion to mannose-containing intestinal cells is believed to be important for the health-promoting effects of probiotics [119], induction of _msa_ by RSV may help in improving the adhesion capacity and probiotics effects of _L. plantarum_. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Locus Tags** & **Species** & \begin{tabular}{c} **PPC Effector** \\ **(Ref.)****a** \\ \end{tabular}  & **Effect** & \begin{tabular}{c} **Phenotype Involved** \\ **(Ref.)****b** \\ \end{tabular}  \\ \hline \multicolumn{5}{c}{**Surface polysaccharide biosynthesis**} \\ _lp\_1177 through_ & _cps1A-I_: polysaccharide biosynthesis & _L plantarum_ & _p_-CA [25] & – & \ \begin{tabular}{c} Reduced SPS levels \\ [69; 104; 105] \\ _lp\_1220-lp\_1221_ \\ \end{tabular}