Differences in the repertoire, regulation and function of Toll-like Receptors and inflammasome-forming Nod-like Receptors between human and mouse.
Abstract Ilya Metchnikoff's use of starfish larvae to discover phagocytosis, and Bruno Lemaitre's and Jules Hoffmann's identification of host defence functions for Drosophila Toll provide compelling examples of the utility of model organisms for discovery of human innate immune pathways. Bruce Beutler's mapping of lipopolysaccharide non-responsiveness in C3H/HeJ mice to the Toll-like Receptor 4 gene similarly highlights the power of the mouse as a model. Models have limitations however, and characterising the functional relevance of human innate immune responses not conserved in the mouse presents both a challenge...
Source: Current Opinion in Microbiology - March 26, 2013 Category: Microbiology Authors: Ariffin JK, Sweet MJ Tags: Curr Opin Microbiol Source Type: research

Antimicrobial functions of inflammasomes.
This article reviews cytokine-dependent and cytokine-independent host defence pathways engaged by inflammasomes during infection. Such inflammatory and antimicrobial mechanisms include the recruitment and activation of immune cells, the production of lipid mediators and complement proteins, the induction of the acute-phase and fever responses, the modulation of serum metallic ion content and the release of intracellular bacteria by pyroptotic cell death. PMID: 23466299 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - March 2, 2013 Category: Microbiology Authors: Chen KW, Schroder K Tags: Curr Opin Microbiol Source Type: research

Ribosome heterogeneity: another level of complexity in bacterial translation regulation.
Abstract Translation of the mRNA-encoded genetic information into proteins is catalyzed by the intricate ribonucleoprotein machine, the ribosome. Historically, the bacterial ribosome is viewed as an unchangeable entity, constantly equipped with the entire complement of RNAs and proteins. Conversely, several lines of evidence indicate the presence of functional selective ribosomal subpopulations that exhibit variations in the RNA or the protein components and modulate the translational program in response to environmental changes. Here, we summarize these findings, which raise the functional status of the ribosome ...
Source: Current Opinion in Microbiology - February 14, 2013 Category: Microbiology Authors: Byrgazov K, Vesper O, Moll I Tags: Curr Opin Microbiol Source Type: research

Expanding control in bacteria: interplay between small RNAs and transcriptional regulators to control gene expression.
Abstract Small regulatory RNAs (sRNAs) are now considered as major post-transcriptional regulators of gene expression in bacteria. Their importance is related to their variety in probably all bacterial species as well as to the extreme diversity of physiological functions of their target genes. An increasing amount of data point to an intimate connection between sRNAs and transcriptional regulatory networks to control multiple functions as important as motility or group behavior. The resulting mixed circuits unravel novel regulatory links and their properties are just starting to be characterized. PMID: 23415...
Source: Current Opinion in Microbiology - February 13, 2013 Category: Microbiology Authors: Mandin P, Guillier M Tags: Curr Opin Microbiol Source Type: research

Uropathogenic Escherichia coli virulence and innate immune responses during urinary tract infection.
Abstract Urinary tract infections (UTI) are among the most common infectious diseases of humans and are the most common nosocomial infections in the developed world. It is estimated that 40-50% of women and 5% of men will develop a UTI in their lifetime, and UTI accounts for more than 1million hospitalizations and $1.6 billion in medical expenses each year in the USA. Uropathogenic Escherichia coli (UPEC) is the primary cause of UTI. This review presents an overview of recent discoveries related to the primary virulence factors of UPEC and major innate immune responses to infection of the lower urinary tract. New ...
Source: Current Opinion in Microbiology - February 8, 2013 Category: Microbiology Authors: Ulett GC, Totsika M, Schaale K, Carey AJ, Sweet MJ, Schembri MA Tags: Curr Opin Microbiol Source Type: research

High-throughput approaches to understanding gene function and mapping network architecture in bacteria.
Abstract Advances in sequencing technology have provided an unprecedented view of bacterial diversity, along with a daunting number of novel genes. Within this new reality lies the challenge of developing large-scale approaches to assign function to the new genes and place them in pathways. Here, we highlight recent advances on this front, focusing on how high-throughput gene-gene, gene-drug and drug-drug interactions can yield functional and mechanistic inferences in bacteria. PMID: 23403119 [PubMed - as supplied by publisher] (Source: Current Opinion in Microbiology)
Source: Current Opinion in Microbiology - February 8, 2013 Category: Microbiology Authors: Brochado AR, Typas A Tags: Curr Opin Microbiol Source Type: research

The battle with the host over microbial size.
Abstract An eponymous feature of microbes is their small size, and size affects their pathogenesis. The recognition of microbes by host factors, for example, is often dependent on the density and number of molecular interactions occurring over a limited surface area. As a consequence, certain antimicrobial substances, such as complement, appear to target particles with a larger surface area more effectively. Although microbes may inhibit these antimicrobial activities by minimizing their effective size, the host uses defenses such as agglutination by immunoglobulin to counteract this microbial evasion strategy. So...
Source: Current Opinion in Microbiology - February 7, 2013 Category: Microbiology Authors: Weiser JN Tags: Curr Opin Microbiol Source Type: research

Cellular organization of the transfer of genetic information.
Abstract Each step involved in the transfer of genetic information is spatially regulated in eukaryotic cells, as transcription, translation and mRNA degradation mostly occur in distinct functional compartments (e.g., nucleus, cytoplasm and P-bodies). At first glance in bacteria, these processes seem to take place in the same compartment - the cytoplasm - because of the conspicuous absence of membrane-enclosed organelles. However, it is becoming increasingly evident that mRNA-related processes are also spatially organized inside bacterial cells, and that this organization affects cellular function. The aims of thi...
Source: Current Opinion in Microbiology - February 6, 2013 Category: Microbiology Authors: Campos M, Jacobs-Wagner C Tags: Curr Opin Microbiol Source Type: research

Genomic transition of enterococci from gut commensals to leading causes of multidrug-resistant hospital infection in the antibiotic era.
Abstract The enterococci evolved over eons as highly adapted members of gastrointestinal consortia of a wide variety of hosts, but for reasons that are not entirely clear, emerged in the 1970s as leading causes of multidrug resistant hospital infection. Hospital-adapted pathogenic isolates are characterized by the presence of multiple mobile elements conferring antibiotic resistance, as well as pathogenicity islands, capsule loci and other variable traits. Enterococci may have been primed to emerge among the vanguard of antibiotic resistant strains because of their occurrence in the GI tracts of insects and simple...
Source: Current Opinion in Microbiology - February 5, 2013 Category: Microbiology Authors: Gilmore MS, Lebreton F, van Schaik W Tags: Curr Opin Microbiol Source Type: research

Roles of adaptor proteins in regulation of bacterial proteolysis.
Abstract Elimination of non-functional or unwanted proteins is critical for cell growth and regulation. In bacteria, ATP-dependent proteases target cytoplasmic proteins for degradation, contributing to both protein quality control and regulation of specific proteins, thus playing roles parallel to that of the proteasome in eukaryotic cells. Adaptor proteins provide a way to modulate the substrate specificity of the proteases and allow regulated proteolysis. Advances over the past few years have provided new insight into how adaptor proteins interact with both substrates and proteases and how adaptor functions are ...
Source: Current Opinion in Microbiology - January 30, 2013 Category: Microbiology Authors: Battesti A, Gottesman S Tags: Curr Opin Microbiol Source Type: research

Exploiting social evolution in biofilms.
Abstract Bacteria are highly social organisms that communicate via signaling molecules, move collectively over surfaces and make biofilm communities. Nonetheless, our main line of defense against pathogenic bacteria consists of antibiotics-drugs that target individual-level traits of bacterial cells and thus, regrettably, select for resistance against their own action. A possible solution lies in targeting the mechanisms by which bacteria interact with each other within biofilms. The emerging field of microbial social evolution combines molecular microbiology with evolutionary theory to dissect the molecular mecha...
Source: Current Opinion in Microbiology - January 25, 2013 Category: Microbiology Authors: Boyle KE, Heilmann S, van Ditmarsch D, Xavier JB Tags: Curr Opin Microbiol Source Type: research

Determinants of specificity in two-component signal transduction.
Abstract Maintaining the faithful flow of information through signal transduction pathways is critical to the survival and proliferation of organisms. This problem is particularly challenging as many signaling proteins are part of large, paralogous families that are highly similar at the sequence and structural levels, increasing the risk of unwanted cross-talk. To detect environmental signals and process information, bacteria rely heavily on two-component signaling systems comprised of sensor histidine kinases and their cognate response regulators. Although most species encode dozens of these signaling pathways, ...
Source: Current Opinion in Microbiology - January 23, 2013 Category: Microbiology Authors: Podgornaia AI, Laub MT Tags: Curr Opin Microbiol Source Type: research

Terminator still moving forward: expanding roles for Rho factor.
Abstract Rho factor is a molecular motor that translocates along nascent RNA and acts on the transcription elongation complex to promote termination. Besides contributing to transcriptional punctuation of the bacterial genome, Rho can act intragenically under conditions that perturb coupling of translation and transcription. Recent advances have shed new light onto several aspects of Rho function, including the translocation mechanism, the avoidance of potential conflicts between DNA replication and transcription, suppression of pervasive antisense transcription and recruitment in riboswitch and small RNA-dependen...
Source: Current Opinion in Microbiology - January 21, 2013 Category: Microbiology Authors: Boudvillain M, Figueroa-Bossi N, Bossi L Tags: Curr Opin Microbiol Source Type: research

The dynamic influence of commensal bacteria on the immune response to pathogens.
Abstract Alterations in the composition of commensal bacterial communities are associated with enhanced susceptibility to multiple inflammatory, allergic, metabolic and infectious diseases in humans. In the context of infection, commensal bacteria-derived signals can influence the host immune response to invasive pathogens by acting as an adjuvant to boost the immune response to infection or by providing tonic stimulation to induce basal expression of factors required for host defense. Conversely, some pathogens have evolved mechanisms that can utilize commensal bacteria to establish a replicative advantage within...
Source: Current Opinion in Microbiology - January 16, 2013 Category: Microbiology Authors: Abt MC, Artis D Tags: Curr Opin Microbiol Source Type: research

Brucella T4SS: the VIP pass inside host cells.
Abstract For many Gram-negative bacteria, like Brucella, the type IV secretion system (T4SS) has a critical role in bacterial virulence. In Brucella, the VirB T4SS permits the injection of bacterial effectors inside host cells, leading to subversion of signaling pathways and favoring bacterial growth and pathogenesis. The virB operon promoter is tightly regulated by a combination of transcriptional activators and repressors that are expressed according to the environmental conditions encountered by Brucella. Recent advances have shed light on the Brucella T4SS regulatory mechanisms and also its substrates. Charact...
Source: Current Opinion in Microbiology - January 11, 2013 Category: Microbiology Authors: Lacerda TL, Salcedo SP, Gorvel JP Tags: Curr Opin Microbiol Source Type: research

Tips and tricks about Shigella invasion of epithelial cells.
Abstract Shigella, the causative agent of bacillary dysentery, invades the colonic epithelium where it elicits an intense inflammation leading to tissular destruction. Key to bacterial virulence, type III effectors injected into host cells reorganize the actin cytoskeleton and regulate inflammatory responses. Much progress has been made recently in the characterization of these type III effectors. These findings have reshaped our view of Shigella invasion, suggesting a strategy to invade epithelial cells 'discretely' as an initial route of invasion, contrasting with the devastating inflammatory response associated...
Source: Current Opinion in Microbiology - January 11, 2013 Category: Microbiology Authors: Carayol N, Tran Van Nhieu G Tags: Curr Opin Microbiol Source Type: research

Inflammasomes and host defenses against bacterial infections.
Abstract The inflammasome has emerged as an important molecular protein complex which initiates proteolytic processing of pro-IL-1β and pro-IL-18 into mature inflammatory cytokines. In addition, inflammasomes initiate pyroptotic cell death that may be independent of those cytokines. Inflammasomes are central to elicit innate immune responses against many pathogens, and are key components in the induction of host defenses following bacterial infection. Here, we review recent discoveries related to NLRP1, NLRP3, NLRC4, NLRP6, NLRP7, NLRP12 and AIM2-mediated recognition of bacteria. Mechanisms for inflammasome a...
Source: Current Opinion in Microbiology - January 11, 2013 Category: Microbiology Authors: Vladimer GI, Marty-Roix R, Ghosh S, Weng D, Lien E Tags: Curr Opin Microbiol Source Type: research

Microbial amyloids - functions and interactions within the host.
Abstract The aggregation of proteins into amyloid fibers is a common characteristic of many neurodegenerative disorders including Alzheimer's, Parkinson's, and prion diseases. Amyloid formation was originally characterized in these systems and is traditionally viewed as a consequence of protein misfolding and aggregation. An emerging field of study brings functional amyloids, like those produced by bacteria, into the scientific mainstream, and demonstrates a ubiquitous role for amyloids in living systems. This review aims to summarize what is known about the bacterial amyloids and their interactions within various...
Source: Current Opinion in Microbiology - January 9, 2013 Category: Microbiology Authors: Schwartz K, Boles BR Tags: Curr Opin Microbiol Source Type: research

Salmonella T3SSs: successful mission of the secret(ion) agents.
sse S Abstract Bacteria of the genus Salmonella express nanosyringe-like organelles called type three secretion systems (T3SSs). These systems promote the secretion of bacterial compounds and their translocation into host cells. Pathogenic Salmonella use two distinct T3SSs, with specialized functions, having the purpose to modify the biology of the host organism and to ensure a successful infection. The bacterial proteins translocated through the first T3SS (T3SS-1) facilitate the entry of Salmonella into host cells, whereas T3SS-2 is an important factor for shaping the intracellular replication niche. In addition...
Source: Current Opinion in Microbiology - January 5, 2013 Category: Microbiology Authors: Moest TP, Méresse S Tags: Curr Opin Microbiol Source Type: research

The impact of Toll-like receptors on bacterial virulence strategies.
Abstract The mammalian immune system has evolved in the presence of microbes, both pathogenic and commensal. The consequences of microbial recognition by the host has led to the development of compensatory mechanisms by both the host and microbe to either resist or tolerate the existence of the other. In this review we discuss examples of this co-evolutionary relationship. Because of space considerations and for conceptual clarity, we have focused on detection of bacteria by the Toll-like receptor (TLR) family and highlight examples of bacterial strategies to evade, subvert and in some cases even utilize these rec...
Source: Current Opinion in Microbiology - January 3, 2013 Category: Microbiology Authors: Arpaia N, Barton GM Tags: Curr Opin Microbiol Source Type: research

The evolutionary pressures that have molded Mycobacterium tuberculosis into an infectious adjuvant.
Abstract Mycobacterium tuberculosis (Mtb) is highly immunogenic and appears to have evolved to preserve its antigenicity. The retention of antigenicity is important to the maintenance of a robust immune response that contributes greatly to the late-stage tissue damage required for transmission and completion of the pathogen's life cycle. Bacterial persistence is achieved through the remodeling of the tissue at site of infection and maintaining the lymphocytes at a distance from the infected macrophages in the granuloma core. The tissue metabolism within the granuloma leads to lipid sequestration that supports bact...
Source: Current Opinion in Microbiology - January 2, 2013 Category: Microbiology Authors: Russell DG Tags: Curr Opin Microbiol Source Type: research

Deadly syringes: type VI secretion system activities in pathogenicity and interbacterial competition.
Abstract Among specialized bacterial secretion systems, the most widespread is the type VI secretion system (T6SS). This transports effector molecules into target cells in a single, cell-contact dependent step. T6SSs are structurally related to the cell-puncturing device of tailed bacteriophages and predicted to function as contractile injection machineries that perforate eukaryotic and prokaryotic target membranes for effector delivery. Activities of T6SSs can play important roles in virulence by modifying the eukaryotic host cytoskeleton through actin crosslinking. They are also efficient weaponry in interbacter...
Source: Current Opinion in Microbiology - January 2, 2013 Category: Microbiology Authors: Kapitein N, Mogk A Tags: Curr Opin Microbiol Source Type: research