Brucella: Molecular Microbiology and Genomics
"a must-have for anyone interested in Brucella" (J. Vet. Med. Assoc.)
"recommended to microbiologists, immunologists, veterinarians, and clinicians" Int. Micro.
Caister Academic Press
and David O'Callaghan2
1Departamento de Microbiología, Instituto de Salud Tropical, Universidad de Navarra, 31008 Pamplona (Navarra), Spain;
2INSERM U1047 , Université de Montpellier 1, UFR Médecine, 30908 Nimes Cedex 2, France
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Brucella is a genus of Gram-negative, facultative, intracellular bacteria that are highly pathogenic for a variety of mammals, including humans. Recently the WHO cited brucellosis to be the world's most widespread zoonosis. An important feature of the pathogenicity of these organisms is their ability to survive and replicate within the host macrophages. However the mechanism for this is unclear. In addition, none of the classical bacterial virulence factors found in other bacterial pathogens have been found in the genomes of the forty Brucella species and biovars analysed to date. Nevertheless the application of systems biology approaches in recent years has transformed research, permitting fascinating new insights into Brucella molecular biology and genomics.
Written by highly acclaimed Brucella scientists, this book comprehensively reviews the most important advances in the field. Opening chapters focus on genetic diversity within Brucella, covering both classical and new species. Particular emphasis is given to how comparative genomics has led to advances in molecular diagnostics, taxonomy and phylogeny. Following chapters cover proteomic analysis, transcriptomic analysis, the VirB type IV secretion system, signalling complexes, e.g. the BvrR/BvrS two-component regulatory system and quorum sensing. These chapters highlight the intricate interplay between factors involved in virulence. Another chapter discusses the role of the Brucella cell envelope in bacterial virulence and evasion of host defences. The final two chapters review the current strategies for the development of novel antibacterial agents and improved vaccines.
This volume is essential reading for everyone with an interest in Brucella and brucellosis. It is also recommended reading for the wider body of scientists, veterinarians and MDs with an interest in microbial diagnostics, microbial pathogenesis, host-parasite interactions, cellular microbiologists and immunologists and vaccine development scientists.
"a must-have for anyone interested in Brucella spp and brucellosis ... a comprehensive and detailed review of the most recent advances regarding Brucella ... This well-referenced book will be a welcome addition to the libraries of researchers, laboratory workers, molecular biologists, microbiologists, and veterinarians ... For those looking for a single, detailed reference on Brucella organisms, purchasing this book will be money well spent." from J. Vet. Med. Assoc. (2012) 240: 686.
"The book ... introduces the reader to what is known thus far and to the current challenges in the taxonomy, genomics and proteomics, diagnosis and epidemiology, vaccine development, virulence mechanisms, and life cycle posed by these enigmatic bacteria. The authors of the 13 chapters are experts in the field ... (the book)can be recommended to microbiologists, immunologists, veterinarians, and clinicians with an interest in microbial pathogenesis, host-bacterium interactions, and microbial diagnosis." from International Microbiology (2011) 14: 235-236
Table of contents
1. Brucella: Relationship to Other Alphaproteobacteria Current Taxonomy and the Emergence of New Species
Holger C. Scholz, Peter Kämpfer and Axel Cloeckaert
The genus Brucella belongs to the class Alphaproteobacteria which is one of the largest and diverse groups within the phylum Proteobacteria. Comparative genome analysis revealed that Brucella is genetically related to plant-associated symbionts and pathogens. The genus Ochrobactrum, consisting of saprophytes that occasionally infect humans, is the closest phylogenetic neighbour. For many years, the taxonomy of Brucella remained unchanged. The recent development of new molecular typing methods and comparative genome analysis however, has resulted in rapid advances in the understanding of Brucella diversity and, after many years of stagnancy, a process of expansion of the genus is in progress. The recent increased occurrence of novel atypical Brucella strains and novel species poses a new challenge to the characterization, classification and nomenclature of the genus Brucella. Genome sequencing projects of these new isolates have been initiated to obtain a better understanding of biology (including pathogenicity) and evolution of members of the genus Brucella.
2. Comparative Genomics and Phylogenomics of Brucella
Bruno W. Sobral and Alice R. Wattam
Brucella species are characterized by extremely high levels of nucleotide similarity and yet vary in microbial and disease phenotypes, as well as in pathogenicity and host preference. These variations initially resulted in classification of six species; B. abortus, B. canis, B. melitensis, B. neotomae, B. ovis and B. suis. The lack of sequence diversity has inhibited molecular studies, but the development of new techniques and the recent availability of genome sequences have revealed interesting differences, including the expansion of the known Brucella species.
3. TheBrucella Genomic Islands
The genomic islands (GIs) are DNA sequences of several kilobases (kb) that contain genes conferring adaptive advantages to the host bacteria. Despite the enclosed intracellular lifestyle, the sequence analysis of Brucella has revealed the presence of various GIs scattered through its genome, a fact that strongly suggests the acquisition of DNA by horizontal transfer events. In addition, the analysis of the genetic content of these regions indicates that they might represent a source of virulence factors. Recently, it has been demonstrated that some predicted GIs are unstable and can be excised from the chromosome by recombination. This experimental evidence points out the foreign origin of such loci and suggests an explanation for the polymorphism related to these large chromosomal regions exhibited by Brucellae.This chapter summarizes the advances in the identification and characterization of Brucella GIs. A detailed analysis of their genetic content and its relation to pathogenicity is also included. Recent data obtained for GI instability is discussed in the context of genome plasticity and virulence attenuation observed in smooth Brucellae.
4. Recent Advances in Molecular Approaches to Brucella Diagnostics And Epidemiology
Adrian M. Whatmore and Krishna K. Gopaul
For many years, the diagnosis of brucellosis depended on tried and tested cultural and serological approaches. However, whilst these techniques have been instrumental in successful control and eradication schemes such as the one undertaken in Great Britain, these methods are not ideal. As a highly infectious zoonotic pathogen culture of Brucella is hazardous whilst serological tests targeting lipopolysaccharide can be compromised by non-specific cross-reactions. With rapid advances in molecular biology, and driven by the need for improved diagnostic and epidemiological approaches, novel techniques based on the genetic component of the pathogen have become more popular in recent years. In this chapter we will discuss the current status of development and implementation of such techniques applied to Brucella whilst also looking forward at potential avenues for further molecular advancement.
5. The Exploration of Brucella Transcriptome, From the ORFeome to RNAseq
Juan M. García-Lobo, María C. Rodríguez, Asunción Seoane, Félix J. Sangari, and Ignacio López-Goñi
In this chapter we will analyze the results available on the characterization of the Brucella transcriptome. After a summary of earlier work on transcription, two technical approaches will be mainly described, on one side the use microarrays, specially that derived from the Brucella ORFeome that allows hybridization with mRNA derived cDNA to determine the relative abundance of transcripts from each B. melitensis ORF. On the other, RNAseq, consisting in the massive sequencing of cDNA libraries derived from mRNA obtained from B. abortus grown in culture medium. Sequencing with the Illumina Genome-Analyzer II platform, produced 3 millions of 35 nt long reads that annealed with single copy coding regions of the genome. This allowed a good coverage for every CDS and produced a new dataset on the transcription of Brucella. We obtained a good correlation for the set of highly expressed genes from the microarrays and confirmed the observations obtained on the asymmetry between chromosome transcription. Preliminary conclusions on intracellular transcription have been drawn from RT-PCR on selected candidate genes and from microarray datasets obtained from virulence related conditions.The RNAseq derived data allowed more versatile data mining giving some new details on transcription from pseudogenes or intergenic regions.
6. What Have We Learned From Brucella Proteomics?
Esteban Chaves-Olarte, Caterina Guzmán-Verri, Eustache Paramithiotis, and Edgardo Moreno
Members of the genus Brucella infect and cause disease in a wide variety of mammals, including humans. Despite this host diversity, the clinical and pathological manifestations of brucellosis seem to be conserved within certain range, being the reproductive tract the main target of infection. The pathogenesis of brucellosis is dependent on the ability of the bacterium to invade and replicate within the endoplasmic reticulum of epithelial and phagocytic cells. From this perspective, the use of comprehensive system biology approaches, like proteomics, has contributed to dissect and unravel some aspects of the life cycle of Brucella organisms. In this review, we describe the advantages and limitations of the proteomic approaches employed in the field of brucellosis to discern, at the cellular and the molecular level, the pathogenesis of brucellosis. The emerging picture is that of a pathogen that does not rely on discrete virulence determinants to establish successful infections, but rather of a microbe that utilizes synchronized complex metabolic and signaling systems to reach its replicating niche at the endoplasmic reticulum of host cells. These systems include secretion machineries like the type IV secretion VirB system and signaling complexes like the two component regulatory BvrR/BvrS system and the quorum sensing transcriptional regulator VjbR, all of which have a profound impact on the metabolic state of the bacterium and particularly on the homeostasis of the cell envelope. In addition, we also discuss how the systematic comparison at the proteomic level of different strains, species and mutants within the Brucella genus has improved the experimental approaches used for diagnosis, taxonomy and phylogeny.
7. Biology and Genetics of the Brucella Outer Membrane
Nieves Vizcaíno and Axel Cloeckaert
The particular characteristics of the Brucella outer membrane (OM) are considered to importantly contribute to the biological properties of these bacteria that are able to survive in the hostile environment of phagocytes and cause persistent infections in diverse mammals. This contrasts with theBrucella's closest relatives in the genus Ochrobactrum which are only occasionally associated to opportunistic infections. High hydrophobicity, resistance to complement, bactericidal cationic peptides, detergents or EDTA, resistance to macrophage degradation or the protection against the host immune response are characteristics related to the Brucella OM. The O-polysaccharide chains of the smooth lipopolysaccharide (S-LPS) are a key component for the virulence of smooth strains but, since naturally rough B. canis and B. ovis that lack O-chains in the LPS are virulent in their respective natural hosts, other traits must have a significant role in virulence. Heterogeneity in LPS, OM proteins, and phospholipids draw a particular OM for each Brucellaa species (in some instances at the biovar or strain level) with a definite composition and topology. This variability leads to modifications in the antigenic and functional properties that could affect the interaction with the host and be related to the differences in pathogenicity and host tropism among the Brucellae.
8. Brucella Quorum Sensing: Much More Than Sensing Quorum
Matthieu Terwagne, Sophie Uzureau, and Jean-Jacques Letesson
Quorum sensing is a regulatory system that allows bacteria to coordinate gene expression according to the local population density. Recently, we demonstrated that the virulence of the facultative intracellular bacteria Brucella depends on quorum sensing. Similar to other Gram negative bacteria, Brucellaquorum sensing utilizes the production and detection of N-acyl homoserine lactone as a signal. However, in Brucella, N-acyl homoserine lactone could serve to monitor the confinement state, a situation in which a single bacterium enclosed in a vacuole can be the quorum. Here, we present a current review covering the intricacies of quorum sensing in Brucella, highlighting the abilities of quorum sensing to influence both Brucella virulence and metabolism.
9. Metal acquisition by Brucella strains
R. Martin Roop II, Eric Anderson, Jenifer Ojeda, David Martinson, Evan Menscher and Daniel W. Martin
Like most other living organisms, Brucella strains require a variety of metals as micronutrients to serve as co-factors and structural components of enzymes and other cellular proteins. Genetic studies have shown that the efficient transport of iron, magnesium, manganese, and zinc are essential for the virulence of Brucella strains in experimental and natural hosts. This chapter will review what is presently known about the metal acquisition and homeostasis systems in Brucella strains.
10. The Two Component System BvrR/BvrS: A Master Regulator of Brucella Virulence
Recent results from proteomic and transcriptomic analyses show that the two component system BvrR/BvrS of Brucella is an global regulator capable of interacting with other regulators, by controlling the synthesis of components of the cell envelope and outer membrane, metabolism of carbon and nitrogen, and of other genes related to the virulence of the bacteria. In this way, the bacteria may sense when they enter a eukaryotic host cell and thus control the expression of a set of genes which allows them to develop during this intracellular phase of their life cycle.
11. The Brucella VirB type IV Secretion System
Renee M. Tsolis and David O'Callaghan
The type IV secretion system (T4SS) encoded by the virB operon is a key pathogenicity determinant that is highly conserved among Brucella species, and is one of the few "classical" virulence factors identified to date. Since its first description in 1999, work on the VirB T4SS has focused on its role in intracellular survival and persistence, its architecture and assembly in the cell envelope, on the signals that induce its expression and function within the infected host cell, on identification of T4SS substrates, and on its effect on the host response to infection. In this chapter, we review the advances in our understanding of structure/function relationships of the T4SS, and of its function in infection by Brucella species.
12. Novel Targets for Antibacterial Agents in Brucella sp.
Christian Baron, Jean-Yves Winum and Stephan Köhler
Novel strategies for the treatment of bacterial infectious diseases are urgently needed. In this chapter we will discuss two complementary approaches aimed at targeting Brucella species during the intracellular growth phase: depriving them of essential amino acid biosynthetic enzymes and disarmament by inhibiting type IV secretion system function that is essential for virulence. Small molecules targeting these functions that are essential exclusively during intracellular growth could serve as leads for the development of novel anti-infective and anti-virulence drugs, respectively. Since such drugs would not kill Brucella during extracellular growth, it is anticipated that the selection pressure for resistant mutants would be reduced. In addition, such specific molecules would not disrupt the human microbiome and thereby avoid side effects of conventional antibiotic treatments. Following similar approaches, anti-infective and anti-virulence drugs could be developed to treat infections caused by a wide variety of bacterial pathogens.
13. Molecular and Chemical Approaches to Brucella Vaccine Development
Thomas A. Ficht and Allison C. Rice-Ficht
Development of improved Brucella vaccines has focused on the identification of the genes that support intracellular survival and those encoding antigens capable of stimulating immune protection. Evaluation of live, attenuated vaccines and subunit vaccines expressed using numerous vector-based systems has provided two general results: i) vaccines providing little protection with elevated safety, and ii) vaccines exhibiting excellent protection that are of questionable safety. In order to address the limitations associated with Brucella vaccinology a fresh look at the interactions between host and pathogen may provide renewed insight. This chapter attempts to reconcile the varied results reported in the literature related to the host response to the invading pathogen and the mechanisms used by the organism to avoid both innate and adaptive immune responses. By reviewing and summarizing the current literature we expect to reveal focal points for new investigations and that inconsistencies limiting such development may be identified and dealt with constructively.
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(EAN: 9781904455936 9781912530519 Subjects: [microbiology] [bacteriology] [medical microbiology] [molecular microbiology] [genomics] )