Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Int Microbiol. 2010 Mar;13(1):1-7. doi: 10.2436/20.1501.01.105.
This article reviews the latest findings on how extracellular signaling controls cell fate determination during the process of biofilm formation by Bacillus subtilis in the artificial setting of the laboratory. To complement molecular genetic approaches, surface-associated communities in settings as diverse as the pitcher plant Sarracenia purpurea and the human lung were investigated. The study of the pitcher plant revealed that the presence or absence of a mosquito larva in the pitcher plant controlled bacterial diversity in the ecosystem inside the pitcher plant. Through the analysis of the respiratory tract microbiota of humans suffering from cystic fibrosis (CF) a correlation between lung function and bacterial community diversity was found. Those that had lungs in good condition had also more diverse communities, whereas patients harboring Pseudomonas aeruginosa-the predominant CF pathogen-in their lungs had less diverse communities. Further studies focused on interspecies and intraspecies relationships at the molecular level in search for signaling molecules that would promote biofilm formation. Two molecules were found that induced biofilm formation in B. subtilis: nystatin-released by other species-and surfactin-released by B. subtilis itself. This is a role not previously known for two molecules that were known for other activities-nystatin as an antifungal and surfactin as a surfactant. In addition, surfactin was found to also trigger cannibalism under starvation. This could be a strategy to maintain the population because the cells destroyed serve as nutrients for the rest. The path that led the author to the study of microbial biofilms is also described.
本文综述了最新研究成果，阐述了枯草芽孢杆菌在实验室人工环境中形成生物膜的过程中，细胞命运决定与细胞外信号传递的关系。除了分子遗传学方法外，本研究还调查了猪笼草Sarracenia purpurea 和人类肺部等不同环境中表面相关群落。对猪笼草的研究表明，蚊子幼虫的存在与否控制了猪笼草内部生态系统中的细菌多样性。通过对囊性纤维化（CF）患者呼吸道微生物群的分析，发现肺功能与细菌群落多样性之间存在相关性。肺部状况良好的患者具有更多样化的群落，而肺部携带铜绿假单胞菌（CF 的主要病原体）的患者群落多样性则较低。进一步的研究集中在物种间和种内关系的分子水平上，以寻找促进生物膜形成的信号分子。发现了两种能够诱导枯草芽孢杆菌生物膜形成的分子：多烯类抗生素制霉菌素（由其他物种释放）和表面活性剂素（由枯草芽孢杆菌自身释放）。这是两种先前已知具有其他活性（制霉菌素作为抗真菌剂，表面活性剂素作为表面活性剂）的分子的新作用。此外，还发现表面活性剂素在饥饿时会引发自噬。这可能是一种维持种群的策略，因为被破坏的细胞可以为其他细胞提供营养。作者研究微生物生物膜的路径也进行了描述。
