Rice Scott A, Tan Chuan Hao, Mikkelsen Per Jensen, Kung Vanderlene, Woo Jerry, Tay Martin, Hauser Alan, McDougald Diane, Webb Jeremy S, Kjelleberg Staffan
The School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia.
ISME J. 2009 Mar;3(3):271-82. doi: 10.1038/ismej.2008.109. Epub 2008 Nov 13.
Mature Pseudomonas aeruginosa biofilms undergo specific developmental events. Using a bacteriophage mutant, generated by deletion of the entire filamentous Pf4 prophage, we show that the phage is essential for several stages of the biofilm life cycle and that it significantly contributes to the virulence of P. aeruginosa in vivo. Here, we show for the first time that biofilms of the Pf4 phage-deficient mutant did not develop hollow centres or undergo cell death, typical of the differentiation process of wild-type (WT) P. aeruginosa PAO1 biofilms. Furthermore, microcolonies of the Pf4 mutant were significantly smaller in size and less stable compared with the WT biofilm. Small colony variants (SCVs) were detectable in the dispersal population of the WT biofilm at the time of dispersal and cell death, whereas no SCVs were detected in the effluent of the Pf4 mutant biofilm. This study shows that at the time when cell death occurs in biofilms of the WT, the Pf4 phage converts into a superinfective form, which correlates with the appearance of variants in the dispersal population. Unexpectedly, mice infected with the Pf4 mutant survived significantly longer than those infected with its isogenic WT strain, showing that Pf4 contributes to the virulence of P. aeruginosa. Hence, a filamentous prophage is a major contributor to the life cycle and adaptive behaviour of P. aeruginosa and offers an explanation for the prevalence of phage in this organism.
成熟的铜绿假单胞菌生物膜会经历特定的发育过程。我们利用通过缺失整个丝状Pf4原噬菌体产生的噬菌体突变体，证明该噬菌体对于生物膜生命周期的多个阶段至关重要，并且它对铜绿假单胞菌在体内的毒力有显著贡献。在此，我们首次表明，Pf4噬菌体缺陷突变体的生物膜不会形成野生型（WT）铜绿假单胞菌PAO1生物膜分化过程中典型的中空中心或发生细胞死亡。此外，与WT生物膜相比，Pf4突变体的微菌落尺寸明显更小且稳定性更低。在WT生物膜分散和细胞死亡时，在其分散群体中可检测到小菌落变体（SCV），而在Pf4突变体生物膜的流出物中未检测到SCV。这项研究表明，在WT生物膜发生细胞死亡时，Pf4噬菌体转变为超感染形式，这与分散群体中变体的出现相关。出乎意料的是，感染Pf4突变体的小鼠存活时间明显长于感染其同基因WT菌株的小鼠，表明Pf4有助于铜绿假单胞菌的毒力。因此，丝状原噬菌体是铜绿假单胞菌生命周期和适应性行为的主要贡献者，并为该生物体中噬菌体的普遍存在提供了解释。
