CCD Photometry of the globular cluster M2. RR Lyrae physical parameters and new variables

We report the results of CCD V and R photometry of the RR Lyrae stars in M2. The periodicities of most variables are revised and new ephemerides are calculated. Light curve decomposition of the RR Lyrae stars was carried out and the corresponding mean physical parameters [Fe/H] = -1.47, Teff = 6276 K, log L = 1.63 Lsun and Mv = 0.71 from nine RRab and [Fe/H] = -1.61, M = 0.54 Msun, Teff = 7215 K, log L = 1.74 Lsun and Mv = 0.71 from two RRc stars were calculated. A comparison of the radii obtained from the above luminosity and temperature with predicted radii from nonlinear convective models is discussed. The estimated mean distance to the cluster is 10.49 +- 0.15 kpc. These results place M2 correctly in the general globular cluster sequences Oosterhoff type, mass, luminosity and temperature, all as a function of the metallicity. Mean relationships for M, log L/Lsun, Teff and Mv as a function of [Fe/H] for a family of globular clusters are offered. These trends are consistent with evolutionary and structural notions on the horizontal branch. Eight new variables are reported.Comment: 13 Pages, 10 Figures, Accepted for publication in MNRA

Fitness of Isogenic Colony Morphology Variants of Pseudomonas aeruginosa in Murine Airway Infection

Chronic lung infections with Pseudomonas aeruginosa are associated with the diversification of the persisting clone into niche specialists and morphotypes, a phenomenon called ‘dissociative behaviour’. To explore the potential of P. aeruginosa to change its morphotype by single step loss-of–function mutagenesis, a signature-tagged mini-Tn5 plasposon library of the cystic fibrosis airway isolate TBCF10839 was screened for colony morphology variants under nine different conditions in vitro. Transposon insertion into 1% of the genome changed colony morphology into eight discernable morphotypes. Half of the 55 targets encode features of primary or secondary metabolism whereby quinolone production was frequently affected. In the other half the transposon had inserted into genes of the functional categories transport, regulation or motility/chemotaxis. To mimic dissociative behaviour of isogenic strains in lungs, pools of 25 colony morphology variants were tested for competitive fitness in an acute murine airway infection model. Six of the 55 mutants either grew better or worse in vivo than in vitro, respectively. Metabolic proficiency of the colony morphology variant was a key determinant for survival in murine airways. The most common morphotype of self-destructive autolysis did unexpectedly not impair fitness. Transposon insertions into homologous genes of strain PAO1 did not reproduce the TBCF10839 mutant morphotypes for 16 of 19 examined loci pointing to an important role of the genetic background on colony morphology. Depending on the chosen P. aeruginosa strain, functional genome scans will explore other areas of the evolutionary landscape. Based on our discordant findings of mutant phenotypes in P. aeruginosa strains PAO1, PA14 and TBCF10839, we conclude that the current focus on few reference strains may miss modes of niche adaptation and dissociative behaviour that are relevant for the microevolution of complex traits in the wild

The Genome of Anopheles darlingi, the main neotropical malaria vector

Anopheles darlingi is the principal neotropical malaria vector, responsible for more than a million cases of malaria per year on the American continent. Anopheles darlingi diverged from the African and Asian malaria vectors ∼100 million years ago (mya) and successfully adapted to the New World environment. Here we present an annotated reference A. darlingi genome, sequenced from a wild population of males and females collected in the Brazilian Amazon. A total of 10 481 predicted protein-coding genes were annotated, 72% of which have their closest counterpart in Anopheles gambiae and 21% have highest similarity with other mosquito species. In spite of a long period of divergent evolution, conserved gene synteny was observed between A. darlingi and A. gambiae. More than 10 million single nucleotide polymorphisms and short indels with potential use as genetic markers were identified. Transposable elements correspond to 2.3% of the A. darlingi genome. Genes associated with hematophagy, immunity and insecticide resistance, directly involved in vectorhuman and vectorparasite interactions, were identified and discussed. This study represents the first effort to sequence the genome of a neotropical malaria vector, and opens a new window through which we can contemplate the evolutionary history of anopheline mosquitoes. It also provides valuable information that may lead to novel strategies to reduce malaria transmission on the South American continent. The A. darlingi genome is accessible at www.labinfo.lncc.br/index.php/anopheles- darlingi. © 2013 The Author(s)

Electrophoresis

Burkholderia cepacia H111, an important pathogen for persons suffering from cystic fibrosis, employs a quorum-sensing (QS) system, cep, to control expression of virulence factors as well as the formation of biofilms. The QS system is thought to ensure that pathogenic traits are only expressed when the bacterial population density is high enough to overwhelm the host before it is able to mount an efficient response. In this study, we compared the protein pattern of the intracellular, extracellular, and surface protein fractions of an AHL- deficient cep/mutant with the one of the parent strain H111 by means of two-dimensional gel electrophoresis (2-DE). Our analysis showed that 55 proteins out of 985 detected spots were differentially expressed; these are expected to represent QS- controlled gene products. Addition of the respective signal molecules to the growth medium of the cep mutant fully restored the wild-type protein expression profile. In total about 5% of the B. cepacia proteome was downregulated and 1% upregulated in the cep/mutant, indicating that quorum sensing represents a global regulatory system. Nineteen proteins were identified with high confidence by N-terminal sequence analysis

Analysis of the quorum-sensing regulon of the opportunistic pathogen Burkholderia cepacia H111 by proteomics

Burkholderia cepacia H111, an important pathogen for persons suffering from cystic fibrosis, employs a quorum-sensing (QS) system, cep, to control expression of virulence factors as well as the formation of biofilms. The QS system is thought to ensure that pathogenic traits are only expressed when the bacterial population density is high enough to overwhelm the host before it is able to mount an efficient response. In this study, we compared the protein pattern of the intracellular, extracellular, and surface protein fractions of an AHL- deficient cep/mutant with the one of the parent strain H111 by means of two-dimensional gel electrophoresis (2-DE). Our analysis showed that 55 proteins out of 985 detected spots were differentially expressed; these are expected to represent QS- controlled gene products. Addition of the respective signal molecules to the growth medium of the cep mutant fully restored the wild-type protein expression profile. In total about 5% of the B. cepacia proteome was downregulated and 1% upregulated in the cep/mutant, indicating that quorum sensing represents a global regulatory system. Nineteen proteins were identified with high confidence by N-terminal sequence analysis