AI-2 activity and biofilm formation of B. longum NCC2705 can be increased by homologous over-expression of LuxS_NCC.

<p>(A) AI-2 activity in the culture supernatant of <i>V. harveyi</i> BB170 (Vh), <i>B. longum</i> NCC2705 (WT) or its <i>luxS</i> overexpressing derivative <i>B. longum</i> NCC2705 pMgap_LuxS_NCC (OE). (B) Biofilm formation of WT or OE grown in MRSc with (+) or without (−) supplementation with 10% filter-sterilized culture supernatant of OE. Values are mean ± SD of one representative culture per strain measured in four (A) or eight (B) replicates and similar results were obtained with supernatants of three independent cultures. Data was analysed by pair-wise comparison to the wildtype controls (WT) or as indicated by the bars using Student's <i>t</i>-test (**: <i>p</i><0.01; ***: <i>p</i><0.001).