A New Highly Conserved Antibiotic Sensing/Resistance Pathway in Firmicutes Involves an ABC Transporter Interplaying with a Signal Transduction System

Signal transduction systems and ABC transporters often contribute jointly to adaptive bacterial responses to environmental changes. In Bacillus subtilis, three such pairs are involved in responses to antibiotics: BceRSAB, YvcPQRS and YxdJKLM. They are characterized by a histidine kinase belonging to the intramembrane sensing kinase family and by a translocator possessing an unusually large extracytoplasmic loop. It was established here using a phylogenomic approach that systems of this kind are specific but widespread in Firmicutes, where they originated. The present phylogenetic analyses brought to light a highly dynamic evolutionary history involving numerous horizontal gene transfers, duplications and lost events, leading to a great variety of Bce-like repertories in members of this bacterial phylum. Based on these phylogenetic analyses, it was proposed to subdivide the Bce-like modules into six well-defined subfamilies. Functional studies were performed on members of subfamily IV comprising BceRSAB from B. subtilis, the expression of which was found to require the signal transduction system as well as the ABC transporter itself. The present results suggest, for the members of this subfamily, the occurrence of interactions between one component of each partner, the kinase and the corresponding translocator. At functional and/or structural levels, bacitracin dependent expression of bceAB and bacitracin resistance processes require the presence of the BceB translocator loop. Some other members of subfamily IV were also found to participate in bacitracin resistance processes. Taken together our study suggests that this regulatory mechanism might constitute an important common antibiotic resistance mechanism in Firmicutes. [Supplemental material is available online at http://www.genome.org.

L'aminopeptidase N d'E. coli : sequence nucleotidique du gene pepN et analyse fonctionnelle de sa region regulatrice

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

La régulation des facteurs de virulence chez Pseudomonas aeruginosa (Quorum Sensing et synthèse d'alginate)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Stress Signaling in Cyanobacteria: A Mechanistic Overview

International audienceCyanobacteria are highly diverse, widely distributed photosynthetic bacteria inhabiting various environments ranging from deserts to the cryosphere. Throughout this range of niches, they have to cope with various stresses and kinds of deprivation which threaten their growth and viability. In order to adapt to these stresses and survive, they have developed several global adaptive responses which modulate the patterns of gene expression and the cellular functions at work. Sigma factors, two-component systems, transcriptional regulators and small regulatory RNAs acting either separately or collectively, for example, induce appropriate cyanobacterial stress responses. The aim of this review is to summarize our current knowledge about the diversity of the sensors and regulators involved in the perception and transduction of light, oxidative and thermal stresses, and nutrient starvation responses. The studies discussed here point to the fact that various stresses affecting the photosynthetic capacity are transduced by common mechanisms

Le régulateur global Mta de Bacillus subtilis (régulon et conséquences de son absence)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Evidence that the PatB (CnfR) factor acts as a direct transcriptional regulator to control heterocyst development and function in the cyanobacterium <i>Nostoc</i> PCC 7120

International audienceNumerous multicellular cyanobacteria are able to form specialized cells that acquire new properties to fulfill specific tasks: atmospheric nitrogen fixation for heterocysts, motility for hormogonia, and dormancy for akinetes. In addition, in the case of heterocysts, mutual interactions occur between vegetative and differentiated cells, making from these prokaryotes exciting models to investigate cell differentiation and its connection to multicellularity (Flores & Herrero, 2010). Like any differentiation, heterocyst formation follows a precise temporal dynamic in which each step is orchestrated through often interconnected transcriptional regulators. Since the early 1990s, the regulation of this process has been extensively studied in the model bacterium Nostoc (Anabaena) PCC7120 (hereafter Nostoc). When the combined nitrogen source (ammonium or nitrate) becomes limiting, this bacterium differentiates heterocyst with a semi-regular pattern along the filaments. Heterocyts are micro-oxic, non-dividing cells, that provide a suitable environmen

The CcdB toxin is an efficient selective marker for CRISPR-plasmids developed for genome editing in cyanobacteria

International audienc

Interaction network among factors involved in heterocyst-patterning in cyanobacteria

International audienceThe genetically regulated pattern of heterocyst formation in multicellular cyanobacteria represents the simplest model to address how patterns emerge and are established, the signals that control them, and the regulatory pathways that act downstream. Although numerous factors involved in this process have been identified, the mechanisms of action of many of them remain largely unknown. The aim of this study was to identify specific relationships between 14 factors required for cell differentiation and pattern formation by exploring their putative physical interactions in the cyanobacterium model Nostoc sp. PCC 7120 and by probing their evolutionary conservation and distribution across the cyanobacterial phylum. A bacterial two-hybrid assay indicated that 10 of the 14 factors studied here are engaged in more than one protein–protein interaction. The transcriptional regulator PatB was central in this network as it showed the highest number of binary interactions. A phylum-wide genomic survey of the distribution of these factors in cyanobacteria showed that they are all highly conserved in the genomes of heterocyst-forming strains, with the PatN protein being almost restricted to this clade. Interestingly, eight of the factors that were shown to be capable of protein interactions were identified as key elements in the evolutionary genomics analysis. These data suggest that a network of 12 proteins may play a crucial role in heterocyst development and patterning. Unraveling the physical and functional interactions between these factors during heterocyst development will certainly shed light on the mechanisms underlying pattern establishment in cyanobacteria

Resistance to Bacitracin in Bacillus subtilis: Unexpected Requirement of the BceAB ABC Transporter in the Control of Expression of Its Own Structural Genes▿ †

The Bacillus subtilis BceAB ABC transporter involved in a defense mechanism against bacitracin is composed of a membrane-spanning domain and a nucleotide-binding domain. Induction of the structural bceAB genes requires the BceR response regulator and the BceS histidine kinase of a signal transduction system. However, despite the presence of such a transduction system and of bacitracin, no transcription from an unaltered bceA promoter is observed in cells lacking the BceAB transporter. Expression in trans of the BceAB transporter in these bceAB cells restores the transcription from the bceA promoter. Cells possessing a mutated nucleotide-binding domain of the transporter are also no longer able to trigger transcription from the bceA promoter in the presence of bacitracin, although the mutated ABC transporter is still bound to the membrane. In these cells, expression of the bceA promoter can no longer be detected, indicating that the ABC transporter not only must be present in the cell membrane, but also must be expressed in a native form for the induction of the bceAB genes. Several hypotheses are discussed to explain the simultaneous need for bacitracin, a native signal transduction system, and an active BceAB ABC transporter to trigger transcription from the bceA promoter