Las islas de patogenicidad de Saphylococcus aureus son capaces de controlar factores de virulencia cromosómicos

Trabajo presentado en la X Reunión de Microbiología Molecular, celebrada en Segovia del 9 al 11 de junio de 2014.Staphylococcus aureus es una importante bacteria patógena, debido a la enorme variedad de infecciones que es capaz de producir. La enorme versatilidad de S. aureus se debe a su habilidad para persistir y multiplicarse en diferentes ambientes junto con su capacidad para producir una gran variedad de factores de virulencia, algunos de las cuales están codificadas en elementos genéticos móviles (EGMs), como bacteriófagos e islas de patogenicidad (SaPI) (1). Sobre el 90% de las cepas de S. aureus aisladas de infecciones humanas están pigmentadas. Staphyloxanthin (STX) es un carotenoide considerado como factor de virulencia, ya que contribuye a la evasión del sistema inmune. Por otro lado, la N-acetiltransferasa (GNAT) está implicada en resistencia a antibióticos. En este trabajo describimos como las SaPIs son capaces de regular la producción de factores de virulencia como son STX y GNAT.Peer Reviewe

A super-family of transcriptional activators regulates bacteriophage packaging and lysis in Gram-positive bacteria

The propagation of bacteriophages and other mobile genetic elements requires exploitation of the phage mechanisms involved in virion assembly and DNA packaging. Here, we identified and characterized four different families of phage-encoded proteins that function as activators required for transcription of the late operons (morphogenetic and lysis genes) in a large group of phages infecting Gram-positive bacteria. These regulators constitute a super-family of proteins, here named late transcriptional regulators (Ltr), which share common structural, biochemical and functional characteristics and are unique to this group of phages. They are all small basic proteins, encoded by genes present at the end of the early gene cluster in their respective phage genomes and expressed under cI repressor control. To control expression of the late operon, the Ltr proteins bind to a DNA repeat region situated upstream of the ter S gene, activating its transcription. This involves the C-terminal part of the Ltr proteins, which control specificity for the DNA repeat region. Finally, we show that the Ltr proteins are the only phage-encoded proteins required for the activation of the packaging and lysis modules. In summary, we provide evidence that phage packaging and lysis is a conserved mechanism in Siphoviridae infecting a wide variety of Gram-positive bacteria.Funding for open access charge: Ministerio de Ciencia e Innovación (MICINN) [Consolider-Ingenio CSD2009-00006, BIO2011-30503-C02-01 and Eranet-pathogenomics PIM2010EPA-00606 to J.R.P]; Cardenal Herrera-CEU University [Copernicus-Santander program to J.R.P.]; Insituto Nacional de Investigaciones Agrarias (INIA) [DR08-0093 to M.A.T-M.]; National Institute of Health [R56AI081837 to G.E.C, R01AI022159-23A2 to R.P.N.]

RinA controls phage-mediated packaging and transfer of virulence genes in Gram-positive bacteria

Phage-mediated transfer of microbial genetic elements plays a crucial role in bacterial life style and evolution. In this study, we identify the RinA family of phage-encoded proteins as activators required for transcription of the late operon in a large group of temperate staphylococcal phages. RinA binds to a tightly regulated promoter region, situated upstream of the terS gene, that controls expression of the morphogenetic and lysis modules of the phage, activating their transcription. As expected, rinA deletion eliminated formation of functional phage particles and significantly decreased the transfer of phage and pathogenicity island encoded virulence factors. A genetic analysis of the late promoter region showed that a fragment of 272 bp contains both the promoter and the region necessary for activation by RinA. In addition, we demonstrated that RinA is the only phage-encoded protein required for the activation of this promoter region. This region was shown to be divergent among different phages. Consequently, phages with divergent promoter regions carried allelic variants of the RinA protein, which specifically recognize its own promoter sequence. Finally, most Gram-postive bacteria carry bacteriophages encoding RinA homologue proteins. Characterization of several of these proteins demonstrated that control by RinA of the phage-mediated packaging and transfer of virulence factor is a conserved mechanism regulating horizontal gene transfer

Las islas de patogenicidad regulan genes cromosómicos mediante de virulencia en Staphylococcus aureus

Trabajo presentado en la XI Reunión del Grupo de Microbiología Molecular de la Sociedad Española de Microbiología (SEM), celebrada en Sevilla del 6 al 8 de septiembre de 2016.Peer reviewe

Las islas de patogenicidad de Staphylococcus aureus controlan genes cromosómicos mediante un sistema de antiterminación.

Trabajo presentado en el XXV Congreso Nacional de Microbiología (SEM 2015), celebrado en Logroño del 7 al 10 de julio de 2015.Peer Reviewe

Moonlighting bacteriophage proteins derepress staphylococcal pathogenicity islands

5 p., 1 table, 3 figures and bibliographyStaphylococcal superantigen-carrying pathogenicity islands (SaPIs) are discrete, chromosomally integrated units of 15 kilobases that are induced by helper phages to excise and replicate. SaPI DNA is then efficiently encapsidated in phage-like infectious particles, leading to extremely high frequencies of intra- as well as intergeneric transfer1–3. In the absence of helper phage lytic growth, the island is maintained in a quiescent prophage-like state by a global repressor, Stl, which controls expression of most of the SaPI genes4. Here we show that SaPI derepression is effected by a specific, non-essential phage protein that binds to Stl, disrupting the Stl–DNA complex and thereby initiating the excision-replication-packaging cycle of the island. Because SaPIs require phage proteins to be packaged5,6, this strategy assures that SaPIs will be transferred once induced. Several different SaPIs are induced by helper phage 80a and, in each case, the SaPI commandeers a different non-essential phage protein for its derepression. The highly specific interactions between different SaPI repressors and helper-phage-encoded antirepressors represent a remarkable evolutionary adaptation involved in pathogenicity island mobilization.This work was supported by grants Consolider-Ingenio CSD2009-00006, BIO2005-08399-C02-02, BIO2008-05284-C02-02 and BIO2008-00642-E/C from the Ministerio de Ciencia e Innovacio´n (MICINN), grants from the Cardenal Herrera-CEU University (PRCEU-UCH25/08 and Copernicus program), from the Conselleria de Agricultura, Pesca i Alimentació (CAPiA) and from the Generalitat Valenciana (ACOMP07/258) to J.R.P.; grants BFU2008-01078 from the MICINN and 2009SGR1106 from the Generalitat de Catalunya to J.B.; NIH grant R21AI067654 and a grant-in-aid from the A. D. Williams Trust and the Baruch Foundation Trust to G.E.C.; and NIH grant R01AI022159-23A2 to R.P.N. Fellowship support for M.A.T.-M. from the Generalitat Valenciana is gratefully acknowledged.Peer reviewe

A super-family of transcriptional activators regulates bacteriophage packaging and lysis in Gram-positive bacteria

The propagation of bacteriophages and other mobile genetic elements requires exploitation of the phage mechanisms involved in virion assembly and DNA packaging. Here, we identified and characterized four different families of phage-encoded proteins that function as activators required for transcription of the late operons (morphogenetic and lysis genes) in a large group of phages infecting Gram-positive bacteria. These regulators constitute a super-family of proteins, here named late transcriptional regulators (Ltr), which share common structural, biochemical and functional characteristics and are unique to this group of phages. They are all small basic proteins, encoded by genes present at the end of the early gene cluster in their respective phage genomes and expressed under cI repressor control. To control expression of the late operon, the Ltr proteins bind to a DNA repeat region situated upstream of the ter S gene, activating its transcription. This involves the C-terminal part of the Ltr proteins, which control specificity for the DNA repeat region. Finally, we show that the Ltr proteins are the only phage-encoded proteins required for the activation of the packaging and lysis modules. In summary, we provide evidence that phage packaging and lysis is a conserved mechanism in Siphoviridae infecting a wide variety of Gram-positive bacteria

Phage dUTPases control transfer of virulence genes by a proto-oncogenic G protein-like mechanism

dUTPases (Duts) have emerged as promising regulatory molecules controlling relevant cellular processes. However, the mechanism underlying this regulatory function remains enigmatic. Using staphylococcal pathogenicity island (SaPI) repression as a model, we report here that phage Duts induce the transfer of SaPI-encoded virulence factors by switching between active (dUTP-bound) and inactive (apo state) conformations, a conversion catalyzed by their intrinsic dUTPase activity. Crystallographic and mutagenic analyses demonstrate that binding to dUTP reorders the C-terminal motif V of the phage-encoded Duts, rendering these proteins into the active conformation required for SaPI derepression. By contrast, the conversion to the apo state conformation by hydrolysis of the bound dUTP generates a protein that is unable to induce the SaPI cycle. Because none of the requirements involving Duts in SaPI transfer are exclusive to the phage-encoded proteins, we propose that Duts are widespread cellular regulators acting in a manner analogous to the eukaryotic G proteins