A New Front in Microbial Warfare-Delivery of Antifungal Effectors by the Bacterial Type VI Secretion System

细菌和真菌在自然界中无处不在，并在许多环境生态位中共同定居。就人类宿主而言，这种跨界相互作用在人类微生物群中很普遍，通常与生物膜和医学相关感染有关。VI型分泌系统（T6SS）被细菌广泛用于向邻近的靶细胞直接发射各种效应蛋白。在细菌间的竞争中，许多细菌病原体利用t6ss作为一种有效的武器，将抗菌效应蛋白传递到对手细菌细胞中。然而。最近令人兴奋的发现是，这种“抗菌”T6SS也是一种有效的抗真菌武器，引发抗真菌效应物，能够杀死致病真菌物种。我们的实验数据表明，t6ss依赖的抗真菌活性广泛存在，并由多种不同的抗真菌效应物介导，类似于抗细菌的t6ss。由于细菌和真菌物种共存于人类微生物组和致病感染中，我们预测抗真菌t6ss将塑造许多与人类健康相关的不同微生物群落。本项目的目标是通过研究T6SS介导的抗真菌活性的医学重要性和分子基础，在建立这一令人兴奋的新研究领域中迈出关键的一步。确定T6SS介导的抗真菌活性的分子基础将在Jan Quinn教授的实验室进行。具体技术包括t6ss中毒真菌细胞的RNA-Seq，以确定特定效应物引发的全基因组真菌转录反应，SGA遗传筛选将生成每个效应物的遗传相互作用网络。这种无偏见的方法将指导后续的分子和生化实验，以确定效应物杀死真菌细胞目标的精确机制。为了探索T6SS介导的抗真菌活性的生理相关性，将采用Chris stewart博士实验室建立的独特的离体人类肠道类肠（“迷你肠道”）模型来探索抗真菌T6SS如何影响人类肠道细菌-真菌共定殖的性质和结果。这一点很重要，因为肠道微生物群的改变与人类健康和许多疾病有关(3)，最近研究人员描述了T6SS在肠道群落中共生菌和致病菌成功繁殖中的作用。

Bacteria and fungi are ubiquitous in nature and co-colonise numerous environmental niches. Focussing on the human host, such cross-kingdom interactions are prevalent within the human microbiota, and are commonly associated with biofilms and medically relevant infections. The type VI secretion system (T6SS) is widely used by bacteria to fire diverse effector proteins directly into neighbouring target cells. Many bacterial pathogens employ T6SSs as a potent weapon to deliver antibacterial effector proteins into rival bacterial cells during inter-bacterial competition. However. recently the exciting discovery was made that this 'anti-bacterial' T6SS is also a potent anti-fungal weapon, eliciting anti-fungal effectors that are able to kill pathogenic fungal species. Our pilot data indicate that T6SS-dependent anti-fungal activity is widespread, and mediated by a variety of different anti-fungal effectors, similar to anti-bacterial T6SSs. As bacterial and fungal species co-exist in the human microbiome and disease-causing infections, we predict that anti-fungal T6SSs will shape many diverse microbial communities relevant to human health. The goal of this current project is to take key steps in establishing this exciting new research field by investigating the medical importance and molecular basis of T6SS mediated anti-fungal activity. Defining the molecular basis of T6SS mediated anti-fungal activity will be undertaken in Prof Jan Quinn's laboratory. Specific techniques include RNA-Seq of T6SS-intoxicated fungal cells to define the genome-wide fungal transcriptional responses elicited by specific effectors, and SGA genetic screens will generate the genetic interaction network for each effector. Such non-biased approaches will direct subsequent molecular and biochemical experiments to define the precise mechanism employed by effectors to kill the fungal cell target. To explore the physiological relevance of T6SS mediated anti-fungal activity, a unique ex vivo human intestinal enteroid ("mini guts") model established in Dr Chris Stewarts's laboratory will be employed to explore how anti-fungal T6SSs can influence the nature and outcome of bacterial-fungal co-colonisation of the human gut. This is important as alterations in the intestinal microbiome are associated with human health and many diseases (3), and roles for the T6SS in the success of both commensal and pathogenic bacteria within gut communities have been recently described.