Mooij Marlies J, Drenkard Eliana, Llamas María A, Vandenbroucke-Grauls Christina M J E, Savelkoul Paul H M, Ausubel Frederick M, Bitter Wilbert
Department of Medical Microbiology and Infection Control, VU medical centre, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.
Department of Genetics, Harvard Medical School and Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA.
Microbiology (Reading). 2007 Jun;153(Pt 6):1790-1798. doi: 10.1099/mic.0.2006/003533-0.
Bacteriophages play an important role in bacterial virulence and phenotypic variation. It has been shown that filamentous bacteriophage Pf4 of Pseudomonas aeruginosa strain PAO1 mediates the formation of small-colony variants (SCVs) in biofilms. This morphology type is associated with parameters of poor lung function in cystic fibrosis patients, and SCVs are often more resistant to antibiotics than wild-type cells. P. aeruginosa strain PA14 also contains a Pf1-like filamentous prophage, which is designated Pf5, and is highly homologous to Pf4. Since P. aeruginosa PA14 produces SCVs very efficiently in biofilms grown in static cultures, the role of Pf5 in SCV formation under these conditions was investigated. The presence of the Pf5 replicative form in total DNA from SCVs and wild-type cells was detected, but it was not possible to detect the Pf5 major coat protein by immunoblot analysis in PA14 SCV cultures. This suggests that the Pf5 filamentous phage is not present at high densities in the PA14 SCVs. Consistent with these results, we were unable to detect coaB expression in SCV cultures and SCV colonies. The SCV variants formed under static conditions were not linked to Pf5 phage activity, since Pf5 insertion mutants with decreased or no production of the Pf5 RF produced SCVs as efficiently as the wild-type strain. Finally, analysis of 48 clinical P. aeruginosa isolates showed no association between the presence of Pf1-like filamentous phages and the ability to form SCVs under static conditions; this suggests that filamentous phages are generally not involved in the emergence of P. aeruginosa SCVs.
噬菌体在细菌毒力和表型变异中发挥着重要作用。已有研究表明，铜绿假单胞菌PAO1菌株的丝状噬菌体Pf4介导生物膜中小菌落变体（SCV）的形成。这种形态类型与囊性纤维化患者肺功能不佳的参数相关，并且SCV通常比野生型细胞对抗生素更具抗性。铜绿假单胞菌PA14菌株也含有一种类似Pf1的丝状原噬菌体，命名为Pf5，与Pf4高度同源。由于铜绿假单胞菌PA14在静态培养的生物膜中能非常高效地产生SCV，因此研究了Pf5在这些条件下SCV形成中的作用。在SCV和野生型细胞的总DNA中检测到了Pf5复制形式，但通过免疫印迹分析在PA14 SCV培养物中无法检测到Pf5主要衣壳蛋白。这表明Pf5丝状噬菌体在PA14 SCV中不存在高密度状态。与这些结果一致，我们在SCV培养物和SCV菌落中未能检测到coaB表达。在静态条件下形成的SCV变体与Pf5噬菌体活性无关，因为Pf5 RF产生减少或不产生的Pf5插入突变体产生SCV的效率与野生型菌株一样高。最后，对48株临床铜绿假单胞菌分离株的分析表明，类似Pf1的丝状噬菌体的存在与在静态条件下形成SCV的能力之间没有关联；这表明丝状噬菌体通常不参与铜绿假单胞菌SCV的出现。
