Gardiner Melissa, Fernandes Neil D, Nowakowski Dennis, Raftery Mark, Kjelleberg Staffan, Zhong Ling, Thomas Torsten, Egan Suhelen
School of Biotechnology and Biomolecular Sciences, Centre for Marine Bio-Innovation, The University of New South Wales Sydney, NSW, Australia.
Bioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical Centre, The University of New South Wales Sydney, NSW, Australia.
Front Microbiol. 2015 Oct 13;6:1130. doi: 10.3389/fmicb.2015.01130. eCollection 2015.
There is increasing evidence to suggest that macroalgae (seaweeds) are susceptible to infectious disease. However, to date, little is known about the mechanisms that facilitate the colonization and virulence of microbial seaweed pathogens. One well-described example of a seaweed disease is the bleaching of the red alga Delisea pulchra, which can be caused by the bacterium Nautella italica R11, a member of the Roseobacter clade. This pathogen contains a unique luxR-type gene, varR, which we hypothesize controls its colonization and virulence. We show here that a varR knock-out strain is deficient in its ability to cause disease in D. pulchra and is defective in biofilm formation and attachment to a common algal polysaccharide. Moreover complementation of the varR gene in trans can restore these functions to the wild type levels. Proteomic analysis of bacterial cells in planktonic and biofilm growth highlight the potential importance of nitrogen scavenging, mobilization of energy reserves, and stress resistance in the biofilm lifestyle of N. italica R11. Moreover, we show that VarR regulates the expression of a specific subset of biofilm-associated proteins. Taken together these data suggest that VarR controls colonization and persistence of N. italica R11 on the surface of a macroalgal host and that it is an important regulator of virulence.
越来越多的证据表明大型海藻（海藻）易受传染病影响。然而，迄今为止，对于促进微生物海藻病原体定殖和毒力的机制知之甚少。一个描述详尽的海藻疾病例子是红藻美丽德氏藻的白化病，它可能由玫瑰杆菌属的意大利纳氏菌R11引起。这种病原体含有一个独特的luxR型基因varR，我们推测它控制着病原体的定殖和毒力。我们在此表明，varR基因敲除菌株在对美丽德氏藻致病的能力上存在缺陷，并且在生物膜形成以及附着于一种常见藻类多糖方面存在缺陷。此外，通过反式互补varR基因可将这些功能恢复到野生型水平。对浮游和生物膜生长状态下细菌细胞的蛋白质组分析突出了氮清除、能量储备动员以及抗逆性在意大利纳氏菌R11生物膜生活方式中的潜在重要性。此外，我们表明VarR调节生物膜相关蛋白特定子集的表达。综合这些数据表明，VarR控制着意大利纳氏菌R11在大型海藻宿主表面的定殖和持久性，并且它是毒力的重要调节因子。
