Virus satellites drive viral evolution and ecology

Virus satellites are widespread subcellular entities, present both in eukaryotic and in prokaryotic cells. Their modus vivendi involves parasitism of the life cycle of their inducing helper viruses, which assures their transmission to a new host. However, the evolutionary and ecological implications of satellites on helper viruses remain unclear. Here, using staphylococcal pathogenicity islands (SaPIs) as a model of virus satellites, we experimentally show that helper viruses rapidly evolve resistance to their virus satellites, preventing SaPI proliferation, and SaPIs in turn can readily evolve to overcome phage resistance. Genomic analyses of both these experimentally evolved strains as well as naturally occurring bacteriophages suggest that the SaPIs drive the coexistence of multiple alleles of the phage-coded SaPI inducing genes, as well as sometimes selecting for the absence of the SaPI depressing genes. We report similar (accidental) evolution of resistance to SaPIs in laboratory phages used for Staphylococcus aureus typing and also obtain the same qualitative results in both experimental evolution and phylogenetic studies of Enterococcus faecalis phages and their satellites viruses. In summary, our results suggest that helper and satellite viruses undergo rapid coevolution, which is likely to play a key role in the evolution and ecology of the viruses as well as their prokaryotic hosts

High atmospheric demand for water can limit forest carbon uptake and transpiration as severely as dry soil

When stressed by low soil water content (SWC) or high vapor pressure deficit (VPD), plants close stomata, reducing transpiration and photosynthesis. However, it has historically been difficult to disentangle the magnitudes of VPD compared to SWC limitations on ecosystem-scale fluxes. We used a 13 year record of eddy covariance measurements from a forest in south central Indiana, USA, to quantify how transpiration and photosynthesis respond to fluctuations in VPD versus SWC. High VPD and low SWC both explained reductions in photosynthesis relative to its long-term mean, as well as reductions in transpiration relative to potential transpiration estimated with the Penman-Monteith equation. Flux responses to typical fluctuations in SWC and VPD had similar magnitudes. Integrated over the year, VPD fluctuations accounted for significant reductions of GPP in both nondrought and drought years. Our results suggest that increasing VPD under climatic warming could reduce forest CO2 uptake regardless of changes in SWC

Phage inducible islands in the gram-positive cocci

The SaPIs are a cohesive subfamily of extremely common phage-inducible chromosomal islands (PICIs) that reside quiescently at specific att sites in the staphylococcal chromosome and are induced by helper phages to excise and replicate. They are usually packaged in small capsids composed of phage virion proteins, giving rise to very high transfer frequencies, which they enhance by interfering with helper phage reproduction. As the SaPIs represent a highly successful biological strategy, with many natural Staphylococcus aureus strains containing two or more, we assumed that similar elements would be widespread in the Gram-positive cocci. On the basis of resemblance to the paradigmatic SaPI genome, we have readily identified large cohesive families of similar elements in the lactococci and pneumococci/streptococci plus a few such elements in Enterococcus faecalis. Based on extensive ortholog analyses, we found that the PICI elements in the four different genera all represent distinct but parallel lineages, suggesting that they represent convergent evolution towards a highly successful lifestyle. We have characterized in depth the enterococcal element, EfCIV583, and have shown that it very closely resembles the SaPIs in functionality as well as in genome organization, setting the stage for expansion of the study of elements of this type. In summary, our findings greatly broaden the PICI family to include elements from at least three genera of cocci

The Grizzly, April 15, 1983

Second Attack: Improvements Sought for Security • New Senior Fund • Seminar Planned • The A\u27s Come to Helfferich Hall • Letter to the Editor: Most Abominable Act • Faculty Promotions Approved • President\u27s Corner • Sexual Assault in Quad • Security Tips • Nuclear Freeze Concert • Ursinus Representatives at UN • Ice Cream Night at Bear\u27s Den • Final Exam Schedule • Republicans for Rock! • Escape From Ursinus • Bear Batsmen Drop Slugfest • Men\u27s Track Evens Up • Men\u27s Tennis Nets Two Wins • Girls\u27 Nets Optimistic • Men\u27s Lacrosse Victorioushttps://digitalcommons.ursinus.edu/grizzlynews/1098/thumbnail.jp

Solonamide B Inhibits Quorum Sensing and Reduces Staphylococcus aureus Mediated Killing of Human Neutrophils

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a serious human pathogen, and particularly the spread of community associated (CA)-MRSA strains such as USA300 is a concern, as these strains can cause severe infections in otherwise healthy adults. Recently, we reported that a cyclodepsipeptide termed Solonamide B isolated from the marine bacterium, Photobacterium halotolerans strongly reduces expression of RNAIII, the effector molecule of the agr quorum sensing system. Here we show that Solonamide B interferes with the binding of S. aureus autoinducing peptides (AIPs) to sensor histidine kinase, AgrC, of the agr two-component system. The hypervirulence of USA300 has been linked to increased expression of central virulence factors like α-hemolysin and the phenol soluble modulins (PSMs). Importantly, in strain USA300 Solonamide B dramatically reduced the activity of α-hemolysin and the transcription of psma encoding PSMs with an 80% reduction in toxicity of supernatants towards human neutrophils and rabbit erythrocytes. To our knowledge this is the first report of a compound produced naturally by a Gram-negative marine bacterium that interferes with agr and affects both RNAIII and AgrA controlled virulence gene expression in S. aureus

Killing niche competitors by remote-control bacteriophage induction

A surprising example of interspecies competition is the production by certain bacteria of hydrogen peroxide at concentrations that are lethal for others. A case in point is the displacement of Staphylococcus aureus by Streptococcus pneumoniae in the nasopharynx, which is of considerable clinical significance. How it is accomplished, however, has been a great mystery, because H2O2 is a very well known disinfectant whose lethality is largely due to the production of hyperoxides through the abiological Fenton reaction. In this report, we have solved the mystery by showing that H2O2 at the concentrations typically produced by pneumococci kills lysogenic but not nonlysogenic staphylococci by inducing the SOS response. The SOS response, a stress response to DNA damage, not only invokes DNA repair mechanisms but also induces resident prophages, and the resulting lysis is responsible for H2O2 lethality. Because the vast majority of S. aureus strains are lysogenic, the production of H2O2 is a very widely effective antistaphylococcal strategy. Pneumococci, however, which are also commonly lysogenic and undergo SOS induction in response to DNA-damaging agents such as mitomycin C, are not SOS-induced on exposure to H2O2. This is apparently because they are resistant to the DNAdamaging effects of the Fenton reaction. The production of an SOS-inducing signal to activate prophages in neighboring organisms is thus a rather unique competitive strategy, which we suggest may be in widespread use for bacterial interference. However, this strategy has as a by-product the release of active phage, which can potentially spread mobile genetic elements carrying virulence genes.This work was supported by Comisión Interministerial de Ciencia y Tecnología Grants BIO2005-08399-C02-02, BIO2008-05284-C02-02, and BIO2008-00642-E/C; Cardenal Herrera-CEU University Grants PRCEUUCH25/ 08 and Copernicus program; and by Conselleria de Agricultura, Pesca i Alimentació (CAPiA), and from the Generalitat Valenciana (ACOMP07/258) (J.R.P.). L.S. and D.V. were supported by Cardenal Herrera-CEU University fellowships

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

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.]

Patient Satisfaction with Primary Care Office-Based Buprenorphine/Naloxone Treatment

BACKGROUND: Factors associated with satisfaction among patients receiving primary care–based buprenorphine/naloxone are unknown. OBJECTIVE: To identify factors related to patient satisfaction in patients receiving primary care–based buprenorphine/naloxone that varied in counseling intensity (20 vs 45 minutes) and office visit frequency (weekly vs thrice weekly). DESIGN AND PARTICIPANTS: One hundred and forty-two opioid-dependent subjects. MEASUREMENTS: Demographics, drug treatment history, and substance use status at baseline and during treatment were collected. The primary outcome was patient satisfaction at 12 weeks. RESULTS: Patients’ mean overall satisfaction score was 4.4 (out of 5). Patients were most satisfied with the medication and ancillary services and indicated strong willingness to refer a substance-abusing friend for the same treatment. Patients were least satisfied with their interactions with other opioid-dependent patients, referrals to Narcotics Anonymous, and the inconvenience of the treatment location. Female gender (β = .17, P = .04) and non-White ethnicity/race (β = .17, P = .04) independently predicted patient satisfaction. Patients who received briefer counseling and buprenorphine/naloxone dispensed weekly had greater satisfaction than those whose medication was dispensed thrice weekly (mean difference 4.9, 95% confidence interval 0.08 to 9.80, P = .03). CONCLUSIONS: Patients are satisfied with primary care office-based buprenorphine/naloxone. Providers should consider the identified barriers to patient satisfaction