FIG 4

FIG 4

Colonization of germ-free zebrafish larvae by LGG wild-type and ΔluxS strain. (A–B) Analysis of LGG colonization in zebrafish gut on 7, 8 and 9 dpf by fluorescence microscopy, n = 9-12. Scale bar: 500 px. (C) Analysis of LGG colonization in zebrafish gut on 6 dpf by transmission electron microscopy. The figure shows germ-free zebrafish (GF), as well as germ-free zebrafish immersed in WT and ΔluxS. Red arrows point to microvilli and bacteria, respectively. Scale bar: 2 μm or 1 μm. (D) Colony-forming unit (CFU) counts of zebrafish larvae in the presence or absence of exogenous, synthesized AI-2 (1 μM), n = 6. (E) Determination of AI-2 content in zebrafish on 7, 8 and 9 dpf by HPLC-FLD, n = 3. AI-2, autoinducer-2; WT, wild type; ΔluxS, luxS mutant; WT/AI-2, wild-type strain supplemented with AI-2; ΔluxS/AI-2, ΔluxS strain supplemented with AI-2. P < 0.05 (*), P < 0.01 (**) and P < 0.001 (***). A negative value in the figure indicates that its concentration is too low and did not meet the detection baseline.