The most common quorum sensing (QS) system in Gram-negative bacteria occurs via N-acyl homoserine lactone (AHLs) signals. An archetypical system consists of a LuxI-family protein synthesizing the AHL signal which binds at quorum concentrations to the cognate LuxR-family transcription factors which then control gene expression by binding to specific sequences in target gene promoters. QS LuxR-family proteins are approximately 250 amino acids long and made up of two domains; at the N-terminus there is an autoinducer-binding domain whereas the C-terminus contains a DNA-binding helix-turn-helix (HTH) domain. QS LuxRs display surprisingly low similarities (18-25%) even if they respond to structurally similar AHLs. 95% of LuxRs share 9 highly conserved amino acid residues; six of these are hydrophobic or aromatic and form the cavity of the AHL-binding domain and the remaining three are in the HTH domain. With only very few exceptions, the luxI/R cognate genes of AHL QS systems are located adjacent to each other. The sequencing of many bacterial genomes has revealed that many proteobacteria also possess LuxRs that do not have a cognate LuxI protein associated with them. These LuxRs have been called orphans and more recently solos. LuxR solos are widespread in proteobacterial species that possess a canonical complete AHL QS system as well as in species that do not. In many cases more than one LuxR solo is present in a bacterial genome. Scientists are beginning to investigate these solos. Are solos responding to AHL signals? If present in a bacterium which possesses a canonical AHL QS system are solos an integral part of the regulatory circuit? Are LuxR solos eavesdropping on AHLs produced by neighboring bacteria? Have they evolved to respond to different signals instead of AHLs, and are these signals endogenously produced or exogenously provided? Are they involved in interkingdom signaling by responding to eukaryotic signals? Recent studies have revealed that LuxR solos are involved in several mechanisms of cell-cell communication in bacteria implicating them in bacterial intraspecies and interspecies communication as well as in interkingdom signaling by responding to molecules produced by eukaryotes. LuxR solos are likely to become major players in signaling since they are widespread among proteobacterial genomes and because initial studies highlight their different roles in bacterial communication. This Research Topic allows scientists studying or interested in LuxR solos to report their data and/or express their hypotheses and thoughts on this important and currently understudied family of signaling proteins.

This book provides an essential update on the startling array of novel insecticidal toxins and drugs produced by the fascinating bacterium Photorhabdus. The respective chapters describe everything from the detailed molecular biology of the ‘Toxin complexes’ or Tc’s to the complexity of insect immune response in relation to both the bacterium and its nematode vector. The volume covers both primary (toxin production and regulation) and secondary (natural product synthesis and regulation) metabolism and emphasises the potential use of toxins and drugs in both agriculture and medicine. It also discusses in detail two totally novel quorum sensing mechanisms and the likely role of LuxR solos in sensing the presence of different bacterial hosts. Lastly, the book explores the unique case of P. asymbiotica, which seems to have evolved the ability to infect both insects and humans. This synthesis proves that Photorhabdus truly does offer a ‘gold mine’ for the discovery of novel insecticidal proteins and novel natural products with potential uses in agriculture and medicine alike.

The book on Trends in Quorum Sensing and Quorum Quenching: New Perspectives and Applications focuses on the recent advances in the field of quorum sensing in bacteria and the novel strategies developed for quorum sensing inhibition. The topics covered are multidisciplinary and wide-ranging,and includes quorum sensing phenomenon in pathogenic bacteria, food spoilers, and agriculturally relevant bacteria. The applications of quorum sensing inhibitors such as small molecules, bioactives, natural compounds, and quorum quenching enzymes in controlling bacterial infections in clinical settings, agriculture and aquaculture are discussed. The potential use of quorum quenching enzymes for mitigating biofouling is also covered. Special focus is given to exploring quorum sensing inhibitors from microbes and flora inhabiting biodiversity rich regions including tropical rain forests and marine environments. Key features: Covers the fundamental aspects, the progress and challenges in the field of quorum sensing and quorum quenching Reviews quorum sensing in Gram-positive and Gram-negative bacteria of clinical, agricultural, and industrial relevance Discusses the application and future trends of quorum sensing inhibitors from lab to clinical and environmental settings Provides comprehensive coverage on molecular mechanisms in bacterial signaling

Background Bacteria use quorum sensing (QS) circuits to coordinate various activities (among which biofilm formation and the expression of virulence factors) based on the presence of signaling molecules. Different families of signal molecules have been identified in Gram positive and Gram negative bacteria (e.g. autoinducer peptides and acyl homoserine lactones). Similarly, different quorum sensing antagonists interfering with these system have been found in nature, promoting a new and promising field of research, quorum sensing interference. One of the most intensively studied applications of quorum sensing interference is its use as an alternative or synergycally with antibiotics to fight (antibiotic-resistant) bacterial pathogens. Many studies have been published claiming quorum sensing inhibitory activity of natural and synthetic compounds. However, after decades of research, several questions regarding the suitability of this approach to fight bacterial pathogens remain unanswered, including the risk that pathogens will develop resistance against quorum quenching. Meanwhile, the interest in quorum sensing has increased considerably, and this has broadened the fields where it can find biotechnological, environmental and industrial applications, such as anti biofouling, steering fermentations, bioremediation and wastewater treatment. Goal and scope The goal of this Research Topic is to broaden the knowledge of the phenotypes regulated by quorum sensing and the advances in quorum sensing interference. Deciphering microorganism language and the different phenotypes regulated by microbial signalling systems is a frontier for the development of new tools for the management of microorganisms to fulfil human needs with a broad application in different areas such as medicine, environmental sciences and industry.

Providing a comprehensive insight into cellular signaling processes in bacteria with a special focus on biotechnological implications, this is the first book to cover intercellular as well as intracellular signaling and its relevance for biofilm formation, host pathogen interactions, symbiotic relationships, and photo- and chemotaxis. In addition, it deals in detail with principal bacterial signaling mechanisms -- making this a valuable resource for all advanced students in microbiology. Dr. Krämer is a world-renowned expert in intracellular signaling and its implications for biotechnology processes, while Dr. Jung is an expert on intercellular signaling and its relevance for biomedicine and agriculture.

This book illustrates the importance and significance of Quorum sensing (QS), it’s critical roles in regulating diverse cellular functions in microbes, including bioluminescence, virulence, pathogenesis, gene expression, biofilm formation and antibiotic resistance. Microbes can coordinate population behavior with small molecules called autoinducers (AHL) which serves as a signal of cellular population density, triggering new patterns of gene expression for mounting virulence and pathogenesis. Therefore, these microbes have the competence to coordinate and regulate explicit sets of genes by sensing and communicating amongst themselves utilizing variety of signals. This book descry emphasizes on how bacteria can coordinate an activity and synchronize their response to external signals and regulate gene expression. The chapters of the book provide the recent advancements on various functional aspects of QS systems in different gram positive and gram negative organisms. Finally, the book also elucidates a comprehensive yet a representative description of a large number of challenges associated with quorum sensing signal molecules viz. virulence, pathogenesis, antibiotic synthesis, biosurfactants production, persister cells, cell signaling and biofilms, intra and inter-species communications, host-pathogen interactions, social interactions & swarming migration in biofilms.

Summarizes the science and recent research developments of chemical communication among bacteria

In this book international experts discuss the state-of-the-art in the biological degradation of hydrocarbons to meet remedial or disposal goals. The work focuses on practical applications, often on globally important scales including the remediation of some of the world’s largest crude oil spills. Other related chapters discuss important implications of microbial transformation of hydrocarbons, including treatment of high fat processing wastes, impacts of microbial biodegradation activity on industrial processes, and the implications of microbial oil degradation in relation to modern oil extraction processes like hydraulic fracturing of shales and extraction of oil sands.

Many potential applications of synthetic and systems biology are relevant to the challenges associated with the detection, surveillance, and responses to emerging and re-emerging infectious diseases. On March 14 and 15, 2011, the Institute of Medicine's (IOM's) Forum on Microbial Threats convened a public workshop in Washington, DC, to explore the current state of the science of synthetic biology, including its dependency on systems biology; discussed the different approaches that scientists are taking to engineer, or reengineer, biological systems; and discussed how the tools and approaches of synthetic and systems biology were being applied to mitigate the risks associated with emerging infectious diseases. The Science and Applications of Synthetic and Systems Biology is organized into sections as a topic-by-topic distillation of the presentations and discussions that took place at the workshop. Its purpose is to present information from relevant experience, to delineate a range of pivotal issues and their respective challenges, and to offer differing perspectives on the topic as discussed and described by the workshop participants. This report also includes a collection of individually authored papers and commentary.

This book addresses the diversity of tropical microorganisms and its applications in agriculture, renewable energy production and environmental protection. It covers several tropical habitats such as rain forests, mangroves, sea and river waters and describes how microorganisms isolated from these regions can be used to control insects and plant diseases, to improve sugar cane and biofuels production among other applications. The book also aims to bring researchers’ attention to the potential of tropical microorganisms for biotechnological purposes, an area that is still far from being well explored.