细菌捕食者Bdellovibrio细菌被认为是强制性的猎物(宿主)依赖性(H-D),因此无法形成生物膜。然而,自发的宿主非依赖性(H-I)变体轴突生长,可以形成强大的生物膜。对350个H-I突变体的筛选表明,定子基因fliL或motA中的单个突变足以产生鞭毛运动性缺陷的H-I菌株,该菌株能够粘附到表面但无法形成生物膜。这些变异在与鞭毛相关的基因中显示出很大的转录变化,猎物入侵,和环状di-GMP(CdG),以及CdG细胞浓度相对于H-D亲本的巨大变化。引入亲本FIL等位基因导致完全逆转为H-D表型,但是我们认为定子蛋白之间的特定相互作用阻止了FLIL旁系同源物的功能互补。相比之下,菌毛相关蛋白(Bd0108)突变背景中的特定突变是生物膜形成所必需的,包括细胞外DNA(eDNA)的分泌,蛋白质,和多糖基质成分。值得注意的是,翻转破坏强烈地减少了生物膜的发展。所有H-I变体在没有猎物的情况下生长相似,在猎物悬浮液中显示出毒株特异性的捕食能力降低,但在猎物生物膜中保持了类似的高效率。全人群等位基因测序建议了宿主独立性的其他途径。因此,定子和侵袭极依赖性信号控制H-D和H-I生物膜形成表型,单一突变凌驾于猎物需求之上,实现从义务掠夺到临时掠夺的转变,对社区动态有潜在影响。我们关于导致兼性捕食的设施和变化的发现也挑战了Bdellovibrio和类似生物是专属性捕食者的概念。
目的:细菌形成生物膜的能力是生物学的中心研究主题,医学,和环境。我们证明了专性(宿主依赖性)“孤立”掠食性细菌Bdellovibrio细菌的培养物,没有猎物就不能复制,可以使用各种遗传途径自发产生不依赖宿主的(H-I)变体,这些变体以轴溶方式生长(作为单个物种,在没有猎物的情况下),并表现出各种表面附着表型,包括生物膜的形成。这些途径包括影响生物膜形成的鞭毛定子基因的单突变,引起运动不稳定和大的运动缺陷,并破坏环状di-GMP细胞内信号。H-I菌株在悬浮液中也表现出降低的捕食效率,但在猎物生物膜中表现出很高的效率。这些变化超越了对猎物的要求,实现从义务掠夺到临时掠夺的转变,对社区动态有潜在影响。
The bacterial predator Bdellovibrio bacteriovorus is considered to be obligatorily prey (host)-dependent (H-D), and thus unable to form biofilms. However, spontaneous host-independent (H-I) variants grow axenically and can form robust biofilms. A screen of 350 H-I mutants revealed that single mutations in stator genes fliL or motA were sufficient to generate flagellar motility-defective H-I strains able to adhere to surfaces but unable to develop biofilms. The variants showed large transcriptional shifts in genes related to flagella, prey-invasion, and cyclic-di-GMP (CdG), as well as large changes in CdG cellular concentration relative to the H-D parent. The introduction of the parental fliL allele resulted in a full reversion to the H-D phenotype, but we propose that specific interactions between stator proteins prevented functional complementation by fliL paralogs. In contrast, specific mutations in a pilus-associated protein (Bd0108) mutant background were necessary for biofilm formation, including secretion of extracellular DNA (eDNA), proteins, and polysaccharides matrix components. Remarkably, fliL disruption strongly reduced biofilm development. All H-I variants grew similarly without prey, showed a strain-specific reduction in predatory ability in prey suspensions, but maintained similar high efficiency in prey biofilms. Population-wide allele sequencing suggested additional routes to host independence. Thus, stator and invasion pole-dependent signaling control the H-D and the H-I biofilm-forming phenotypes, with single mutations overriding prey requirements, and enabling shifts from obligate to facultative
predation, with potential consequences on community dynamics. Our findings on the facility and variety of changes leading to facultative
predation also challenge the concept of Bdellovibrio and like organisms being obligate predators.
OBJECTIVE: The ability of bacteria to form biofilms is a central research theme in biology, medicine, and the environment. We show that cultures of the obligate (host-dependent) \"solitary\" predatory bacterium Bdellovibrio bacteriovorus, which cannot replicate without prey, can use various genetic routes to spontaneously yield host-independent (H-I) variants that grow axenically (as a single species, in the absence of prey) and exhibit various surface attachment phenotypes, including biofilm formation. These routes include single mutations in flagellar stator genes that affect biofilm formation, provoke motor instability and large motility defects, and disrupt cyclic-di-GMP intracellular signaling. H-I strains also exhibit reduced predatory efficiency in suspension but high efficiency in prey biofilms. These changes override the requirements for prey, enabling a shift from obligate to facultative
predation, with potential consequences on community dynamics.