Many Pseudoalteromonas strains can produce bioactive compounds with antimicrobial activities. This study focused on a probiotic candidate P.flavipulchra CDM8 to reveal its novel antibacterial mechanism and risks for antibiotic resistance dissemination. Strain CDM8 could form floating biofilm, displayed strikingly broad antibacterial activities against multiple Vibrio and Bacillus species, and decreased the competitor’s concentration in their co-cultures in the microtiter plate tests. It could also form vesicle/pilus-like structures on the outer surface, which were indicated to participate in the bactericidal activity and represent a novel antibacterial mechanism of CDM8, according to the scanning electron microscopic observation. However, CDM8 displayed multi-antibiotic resistance, conferred by the multidrug resistance regions in hotspot 4 and variable region III of a novel SXT/R391-like integrative and conjugative element (ICEPflCDM8). Summing up, our results provided a better understanding of the bactericidal mechanism of P. flavipulchra and highlighted the role of SXT/R391-like ICEs in conferring multidrug resistance phenotype of probiotic P. flavipulchra candidates.

许多假单胞菌菌株可以产生具有抗菌活性的生物活性化合物。这项研究的重点益生菌候选P。flavipulchra CDM8揭示了其新颖的抗菌机制和传播抗生素耐药性的风险。菌株CDM8可以形成漂浮的生物膜，对多种弧菌和芽孢杆菌显示出惊人的广泛抗菌活性种，并在微量滴定板测试中降低了竞争对手在其共培养物中的浓度。根据扫描电子显微镜观察，它还可以在外表面上形成囊泡/菌毛样结构，表明它们参与了杀菌活性并代表了CDM8的新型抗菌机制。然而，CDM8显示出多种抗生素抗性，这是由新型SXT / R391样整合和结合元件（ICE Pf1 CDM8）的热点4和可变区III中的多药抗性区域赋予的。综上所述，我们的结果更好地了解了黄萎病菌的杀菌机理，并强调了SXT / R391样ICE在赋予益生菌多药耐药表型方面的作用。P. flavipulchra候选人。