A natural single nucleotide mutation in the small regulatory RNA ArcZ of Dickeya solani switches off the antimicrobial activities against yeast and bacteria.

The necrotrophic plant pathogenic bacterium Dickeya solani emerged in the potato agrosystem in Europe. All isolated strains of D. solani contain several large polyketide synthase/non-ribosomal peptide synthetase (PKS/NRPS) gene clusters.

Structural basis for recognition of transcriptional terminator structures by ProQ/FinO domain RNA chaperones.

The ProQ/FinO family of RNA binding proteins mediate sRNA-directed gene regulation throughout gram-negative bacteria. Here, we investigate the structural basis for RNA recognition by ProQ/FinO proteins, through the crystal structure of the ProQ/FinO domain of the Legionella pneumophila DNA uptake regulator, RocC, bound to the transcriptional terminator of its primary partner, the sRNA RocR. The structure reveals specific recognition of the 3' nucleotide of the terminator by a conserved pocket involving a β-turn-α-helix motif, while the hairpin portion of the terminator is recognized by a conserved α-helical N-cap motif.

Diverse conjugative elements silence natural transformation in species.

Natural transformation (i.e., the uptake of DNA and its stable integration in the chromosome) is a major mechanism of horizontal gene transfer in bacteria.

RNA Chaperones Step Out of Hfq's Shadow.

The stability and function of regulatory small RNAs (sRNAs) often require a specialized RNA-binding protein called an RNA chaperone. Recent findings show that proteins containing a ProQ/FinO domain constitute a new class of RNA chaperones that could play key roles in post-transcriptional gene regulation throughout bacterial species.

Silently transformable: the many ways bacteria conceal their built-in capacity of genetic exchange.

Bacteria can undergo genetic transformation by actively integrating genetic information from phylogenetically related or unrelated organisms. The original function of natural transformation remains a subject of debate, but it is well established as a major player in genome evolution. Naturally transformable bacteria use a highly conserved DNA uptake system to internalize DNA and integrate it in their chromosome by homologous recombination.

Silencing of natural transformation by an RNA chaperone and a multitarget small RNA.

A highly conserved DNA uptake system allows many bacteria to actively import and integrate exogenous DNA. This process, called natural transformation, represents a major mechanism of horizontal gene transfer (HGT) involved in the acquisition of virulence and antibiotic resistance determinants. Despite evidence of HGT and the high level of conservation of the genes coding the DNA uptake system, most bacterial species appear non-transformable under laboratory conditions.

Natural transformation occurs independently of the essential actin-like MreB cytoskeleton in Legionella pneumophila.

Natural transformation is the process by which bacteria can actively take up and integrate exogenous DNA thereby providing a source of genetic diversity. Under specific growth conditions the coordinated expression of several genes--a situation referred to as "competence"--allows bacteria to assemble a highly processive and dedicated system that can import high molecular weight DNA. Within the cell these large imported DNA molecules are protected from degradation and brought to the chromosome for recombination.

The ParB-parS Chromosome Segregation System Modulates Competence Development in Streptococcus pneumoniae.

Unlabelled: ParB proteins bind centromere-like DNA sequences called parS sites and are involved in plasmid and chromosome segregation in bacteria. We previously showed that the opportunistic human pathogen Streptococcus pneumoniae contains four parS sequences located close to the origin of replication which are bound by ParB. Using chromatin immunoprecipitation (ChIP), we found here that ParB spreads out from one of these parS sites, parS(-1.

Control of transcription elongation by GreA determines rate of gene expression in Streptococcus pneumoniae.

Transcription by RNA polymerase may be interrupted by pauses caused by backtracking or misincorporation that can be resolved by the conserved bacterial Gre-factors. However, the consequences of such pausing in the living cell remain obscure. Here, we developed molecular biology and transcriptome sequencing tools in the human pathogen Streptococcus pneumoniae and provide evidence that transcription elongation is rate-limiting on highly expressed genes.

Antibiotic-induced replication stress triggers bacterial competence by increasing gene dosage near the origin.

Streptococcus pneumoniae (pneumococcus) kills nearly 1 million children annually, and the emergence of antibiotic-resistant strains poses a serious threat to human health. Because pneumococci can take up DNA from their environment by a process called competence, genes associated with antibiotic resistance can rapidly spread. Remarkably, competence is activated in response to several antibiotics.

Role of the single-stranded DNA-binding protein SsbB in pneumococcal transformation: maintenance of a reservoir for genetic plasticity.

Bacteria encode a single-stranded DNA (ssDNA) binding protein (SSB) crucial for genome maintenance. In Bacillus subtilis and Streptococcus pneumoniae, an alternative SSB, SsbB, is expressed uniquely during competence for genetic transformation, but its precise role has been disappointingly obscure. Here, we report our investigations involving comparison of a null mutant (ssbB(-)) and a C-ter truncation (ssbBΔ7) of SsbB of S.

SMC is recruited to oriC by ParB and promotes chromosome segregation in Streptococcus pneumoniae.

Segregation of replicated chromosomes is an essential process in all organisms. How bacteria, such as the oval-shaped human pathogen Streptococcus pneumoniae, efficiently segregate their chromosomes is poorly understood. Here we show that the pneumococcal homologue of the DNA-binding protein ParB recruits S.

RadC, a misleading name?

The pfam04002 annotation describes RadC as a bacterial DNA repair protein. Although the radC gene is expressed specifically during competence for genetic transformation in Streptococcus pneumoniae, we report that radC mutants exhibit normal uptake and processing of transforming DNA. They also display normal sensitivity to DNA-damaging agents, providing no support for the rad epithet.

Identification of the major protein component of the pneumococcal eclipse complex.

During genetic transformation of Streptococcus pneumoniae, single strands from native donor DNA enter competent cells, where they associate with an unidentified protein with a molecular mass of 15 to 20 kDa to form the eclipse complex. Using Western blotting, we identify the principal protein cofractionating with donor DNA in this complex as SsbB.

Antibiotic stress induces genetic transformability in the human pathogen Streptococcus pneumoniae.

Natural transformation is a widespread mechanism for genetic exchange in bacteria. Aminoglycoside and fluoroquinolone antibiotics, as well as mitomycin C, a DNA-damaging agent, induced transformation in Streptococcus pneumoniae. This induction required an intact competence regulatory cascade.