RpoS (σ(S)), the stationary phase/stress σ factor, controls the expression of a large number of genes involved in cellular responses to a variety of stresses. However, the role of RpoS appears to differ in different bacteria. While RpoS is an important regulator of flagellum biosynthesis, it is associated with biofilm development in Edwardsiella tarda. Biofilms are dense communities formed by bacteria and are important for microbe survival under unfavorable conditions. The type VI secretion system (T6SS) discovered recently is reportedly associated with several phenotypes, ranging from biofilm formation to stress sensing. For example, Vibrio anguillarum T6SS was proposed to serve as a sensor for extracytoplasmic signals and modulates RpoS expression and stress response. In this study, we investigated the physiological roles of RpoS in Yersinia pseudotuberculosis, including bacterial survival under stress conditions, flagella formation, biofilm development and T6SS expression. We found that RpoS is important in resistance to multiple stressors-including H2O2, acid, osmotic and heat shock-in Y. pseudotuberculosis. In addition, our study showed that RpoS not only modulates the expression of T6SS but also regulates flagellum formation by positively controlling the flagellar master regulatory gene flhDC, and affects the formation of biofilm on Caenorhabditis elegans by regulating the synthesis of exopolysaccharides. Taken together, these results show that RpoS plays a central role in cell fitness under several adverse conditions in Y. pseudotuberculosis.
Bacterial type VI secretion systems (T6SSs) inject toxic effectors into adjacent eukaryotic and prokaryotic cells. It is generally thought that this process requires physical contact between the two cells. Here, we provide evidence of contact-independent killing by a T6SS-secreted effector. We show that the pathogen Yersinia pseudotuberculosis uses a T6SS (T6SS-3) to secrete a nuclease effector that kills other bacteria in vitro and facilitates gut colonization in mice. The effector (Tce1) is a small protein that acts as a Ca2+- and Mg2+-dependent DNase, and its toxicity is inhibited by a cognate immunity protein, Tci1. As expected, T6SS-3 mediates canonical, contact-dependent killing by directly injecting Tce1 into adjacent cells. In addition, T6SS-3 also mediates killing of neighboring cells in the absence of cell-to-cell contact, by secreting Tce1 into the extracellular milieu. Efficient contact-independent entry of Tce1 into target cells requires proteins OmpF and BtuB in the outer membrane of target cells. The discovery of a contact-independent, long-range T6SS toxin delivery provides a new perspective for understanding the physiological roles of T6SS in competition. However, the mechanisms mediating contact-independent uptake of Tce1 by target cells remain unclear.
These results reveal that CgPrx functions as a multifunctional protein crucial for adapting appropriate responses to different levels of oxidative challenge in C. glutamicum. Antioxid. Redox Signal. 26, 1-14.
Diatom frustules, considered as novel bio-functional materials, display a diversity of patterns and unique micro-and nanostructures which may be useful in many areas of application. Existing devices directly use the original structure of the biosilica frustules, limiting their function and structural scale. Current research into the shapes, materials and structural properties of frustules are considered; a series of frustule processing methods including structure processing, material modification, bonding and assembly techniques are reviewed and discussed. The aim is to improve the function of diatom frustules allowing them to meet the design requirements of different types of micro devices. In addition, the importance of the comprehensive use of diatom processing methods in device research is discussed using biosensors and solar cells as examples, and the potential of bio-manufacturing technology based on diatom frustules is examined. Nature presents a wide range of functional structures. Particularly at the micro-and nanoscale, the complexity and functionality of biological structures are far greater than those of equivalent artificial devices, making these biological structures an appropriate subject for biotechnology and bio-manufacturing [1,2]. In our previous studies, we have reported bio-limited forming [3] and bio-replication forming [4,5] methods for manufacturing functional particles or surface morphology from biological structures. Micro devices with highly desirable structure and characteristics could be produced from biological micro-or nanostructures. Single-celled diatoms are widely distributed in rivers, lakes and other water bodies, and have a fast (exponential) reproductive rate. The cell wall of a diatom known as the frustule, has a transparent structure composed of amorphous silica [6]. The frustule has good mechanical strength [7,8], a variety of three-dimensional (3D) shapes [9,10], multi-level nanopores and microstructures [11,12], large surface area and unique optical properties [13][14][15], making it a potential novel functional material for bio-manufacturing. Studies on theoretical understanding, manufacturing methods and functionalization of diatom frustules are ongoing. In the last two centuries, the importance of diatom frustules in the field of micro-and nanotechnology has become increasingly evident. The potential of frustules has been extensively explored by academics and for commercial application. The resulting new theories and techniques have found wide application, leading to the formation of a new interdisciplinary area of research called diatom-based bio-nanotechnology (or diatom nanotechnology) [16][17][18][19][20][21]. The potential for diatoms in device applications, such as high-sensitivity gas sensors [22], drug delivery devices [23], biocarriers for biosensors [24][25][26][27], micro-filters [12,28], solar cells, battery electrodes and electroluminescent display devices [19] has been examined. However, the direct
The type VI secretion system (T6SS) is a versatile secretion system widely distributed in Gram-negative bacteria that delivers multiple effector proteins into either prokaryotic or eukaryotic cells, or into the extracellular milieu. T6SS participates in various physiological processes including bacterial competition, host infection, and stress response. Three pathogenic Yersinia species, namely Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica, possess different copies of T6SSs with distinct biological functions. This review summarizes the pathogenic, antibacterial, and stress-resistant roles of T6SS in Yersinia and the ion-transporting ability in Y. pseudotuberculosis. In addition, the T6SS-related effectors and regulators identified in Yersinia are discussed.
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