EcoSal Plus最新文献

EcoSal Plus (ESP) is the authoritative online review journal that publishes an ever-growing body of expert reviews covering virtually all aspects of Escherichia coli, Salmonella, and other members of the order Enterobacterales and their use as model microbes for biological explorations. This review will cover the history of ESP, starting with its origins as multi-volume printed books entitled Escherichia coli and Salmonella: Cellular and Molecular Biology that became "the Bible" for information on the physiology, metabolism, genetics, and other aspects of E. coli and Salmonella. After two printed editions, this resource moved online as EcoSal in an era when electronic publishing was still in its infancy. Progress in establishing EcoSal was slow due to technical issues of online publishing and difficulties in recruiting authors to produce new material. This venture was relaunched in 2013 as EcoSal Plus in a completely new web platform that was much more user (and author) friendly and with an expanded scope to include other members of the order Enterobacterales. EcoSal Plus will be ending as a standalone publication but will merge with Microbiology and Molecular Biology Reviews to continue providing high-quality, authoritative reviews on E. coli, Salmonella, and related organisms.

Siderophore cephalosporins are designed to exploit bacterial nutrient uptake systems to gain accelerated uptake across the outer membrane of Gram-negative bacteria. They contain iron (III) binding motifs that allow them to form complexes that will be recognized as potential substrates by iron-siderophore transport systems. Research during the last five decades has culminated in the approval for clinical use of the siderophore cephalosporin cefiderocol, which incorporates accumulated learning from investigations of structural features that enhance resistance toward hydrolysis by β-lactamases, that promote bacterial membrane permeability, and that confer long pharmacokinetic half-life in the human host.

The homologous recombination (HR) system of bacteriophage T4 plays critical, direct roles in the replication and repair of the phage genome. This review covers the classic, UvsX-dependent HR pathway in T4, focusing on recent findings on the mechanisms of central HR proteins UvsX, UvsY, and Gp32, plus the key helicase and nuclease enzymes that affect HR and promote its coupling to T4 recombination-dependent replication and repair processes. The T4 HR pathways are paradigmatic, since they are highly conserved in all orders of viral and cellular life. Therefore, the study of T4 recombination is highly relevant to biomedicine and to environmental microbiology. At the same time, the tractability of the T4 recombination system for biochemical studies has led to the development of novel, isothermal DNA amplification technologies based on the activities of UvsX, UvsY, and Gp32, which are discussed herein. Globally, the recent revolution in metagenomics has demonstrated that T4-like phages, most encoding the genes and proteins of the T4 HR system, are abundant and widespread in the environment, where they play important roles in the dynamics of diverse microbiomes, from the earth's oceans to the animal gut. Accordingly, we discuss the conservation of T4 HR genes in representatives of T4-like jumbo phages and cyanophages. As a paradigm for HR in diverse organisms, as a source of novel technologies, and as a window on the importance of bacteriophages in the environment, the T4 HR system continues to provide new insights and reagents for a better understanding of life on earth.

Escherichia coli has been a vital model organism for studying chromosomal structure, thanks, in part, to its small and circular genome (4.6 million base pairs) and well-characterized biochemical pathways. Over the last several decades, we have made considerable progress in understanding the intricacies of the structure and subsequent function of the E. coli nucleoid. At the smallest scale, DNA, with no physical constraints, takes on a shape reminiscent of a randomly twisted cable, forming mostly random coils but partly affected by its stiffness. This ball-of-spaghetti-like shape forms a structure several times too large to fit into the cell. Once the physiological constraints of the cell are added, the DNA takes on overtwisted (negatively supercoiled) structures, which are shaped by an intricate interplay of many proteins carrying out essential biological processes. At shorter length scales (up to about 1 kb), nucleoid-associated proteins organize and condense the chromosome by inducing loops, bends, and forming bridges. Zooming out further and including cellular processes, topological domains are formed, which are flanked by supercoiling barriers. At the megabase-scale both large, highly self-interacting regions (macrodomains) and strong contacts between distant but co-regulated genes have been observed. At the largest scale, the nucleoid forms a helical ellipsoid. In this review, we will explore the history and recent advances that pave the way for a better understanding of E. coli chromosome organization and structure, discussing the cellular processes that drive changes in DNA shape, and what contributes to compaction and formation of dynamic structures, and in turn how bacterial chromatin affects key processes such as transcription and replication.

Salmonella enterica is a diverse species that infects both humans and animals. S. enterica subspecies enterica consists of more than 1,500 serovars. Unlike typhoidal Salmonella serovars which are human host-restricted, non-typhoidal Salmonella (NTS) serovars are associated with foodborne illnesses worldwide and are transmitted via the food chain. Additionally, NTS serovars can cause disease in livestock animals causing significant economic losses. Salmonella is a well-studied model organism that is easy to manipulate and evaluate in animal models of infection. Advances in genetic engineering approaches in recent years have led to the development of Salmonella vaccines for both humans and animals. In this review, we focus on current progress of recombinant live-attenuated Salmonella vaccines, their use as a source of antigens for parenteral vaccines, their use as live-vector vaccines to deliver foreign antigens, and their use as therapeutic cancer vaccines in humans. We also describe development of live-attenuated Salmonella vaccines and live-vector vaccines for use in animals.

Type IV pili (T4Ps) are surface filaments widely distributed among bacteria and archaea. T4Ps are involved in many cellular functions and contribute to virulence in some species of bacteria. Due to the diversity of T4Ps, different properties have been observed for homologous proteins that make up T4Ps in various organisms. In this review, we highlight the essential components of T4Ps, their functions, and similarities to related systems. We emphasize the unique T4Ps of enteric pathogens within the Enterobacteriaceae family, which includes pathogenic strains of Escherichia coli and Salmonella. These include the bundle-forming pilus (BFP) of enteropathogenic E. coli (EPEC), longus (Lng) and colonization factor III (CFA/III) of enterotoxigenic E. coli (ETEC), T4P of Salmonella enterica serovar Typhi, Colonization Factor Citrobacter (CFC) of Citrobacter rodentium, T4P of Yersinia pseudotuberculosis, a ubiquitous T4P that was characterized in enterohemorrhagic E. coli (EHEC), and the R64 plasmid thin pilus. Finally, we highlight areas for further study.

Toxin-antitoxin systems are ubiquitous in the prokaryotic world and widely distributed among chromosomes and mobile genetic elements. Several different toxin-antitoxin system types exist, but what they all have in common is that toxin activity is prevented by the cognate antitoxin. In type I toxin-antitoxin systems, toxin production is controlled by an RNA antitoxin and by structural features inherent to the toxin messenger RNA. Most type I toxins are small membrane proteins that display a variety of cellular effects. While originally discovered as modules that stabilize plasmids, chromosomal type I toxin-antitoxin systems may also stabilize prophages, or serve important functions upon certain stress conditions and contribute to population-wide survival strategies. Here, we will describe the intricate RNA-based regulation of type I toxin-antitoxin systems and discuss their potential biological functions.

Promoter-specific activation of transcript initiation provides an important regulatory device in Escherichia coli and Salmonella. Here, we describe the different mechanisms that operate, focusing on how they have evolved to manage the "housekeeping" bacterial transcription machinery. Some mechanisms involve assisting the bacterial DNA-dependent RNA polymerase or replacing or remodeling one of its subunits. Others are directed to chromosomal DNA, improving promoter function, or relieving repression. We discuss how different activators work together at promoters and how the present complex network of transcription factors evolved.