What Does It Mean to Be Musical?

Music can be seen as a model system for understanding gene × environment interactions and how these can influence neurocognitive development. The concept of musicality, however, is underspecified and not well understood. Here, I propose a framework for defining musicality to provide a foundation for studying the contributions of biological and environmental factors.     

What can Dictyostelium bring to the study of Pseudomonas infections?

Bacterial infections are complex events. They are studied in a variety of simple model systems, using mammalian or non-mammalian hosts, all of which fail to reproduce fully the situation in infected patients. Each model presents a combination of conceptual, practical, and ethical advantages and disadvantages. In this review, we detail the use of Dictyostelium discoideum amoebae as a model to study Pseudomonas aeruginosa. More specifically, our aim is to explore what this additional model system can bring to our understanding of Pseudomonas infections. The study of interactions between Dictyostelium amoebae and Pseudomonas provides a view of the selection pressures exerted by environmental predators on Pseudomonas. It also represents a unique system to assess the virulence of very large numbers of Pseudomonas strains.     

The type-4 pilus is the major virulence-associated adhesin of Pseudomonas aeruginosa – a review

Pseudomonas aeruginosa (Pa) produces several surface-associated adherence factors or adhesins which promote attachment to epithelial cells and contribute to the virulence of this pathogen. Among them, the type-4 pilus accounts for about 90% of the adherence capability of Pa to human lung pneumocyte A549 cells. Furthermore, it is responsible for more than 90% of the virulence in AB.Y/SnJ mice. Pa type-4 pili display a tip-base differentiation with the adherence function located at the tip of the pilus. All Pa pili prototypes characterized so far contain an intrachain disulfide loop (DSL) of 12 to 17 semi-conserved amino acid residues at the C-terminus of pilin. In Pa, this DSL comprises the epithelial cell-binding domain. Despite little sequence homology, DSL-containing peptides of different pilin prototypes seemingly reveal striking structural similarities. Two β-turns within the loop and the disulfide bridge impose significant structural rigidity on the DSL pilin peptide, suggesting a conformationally conserved binding domain. Insertions of C-terminal pilin peptides with disrupted DSL displayed on the surface of bacterial S-layer mediate the same receptor binding characteristics as pili, indicating that a DSL is not essential in maintaining the functionality of the binding domain. Pa pili bind specifically to the carbohydrate moiety of the glycosphingolipids (GSL) asialo-G_M1 and asialo-G_M2 and, to a much weaker extent, to lactosyl ceramide and ceramide trihexoside. The disaccharide sequence GalNAcβ(1-4)Gal, common in both asialo-G_M1 and asialo-G_M2, likely represents the minimal structural receptor motif recognized by the pili. Pa pili also bind to surface-localized proteins of human epithelial cells and other cell types, suggesting that non-sialylated GSL and (glyco)proteins function as receptors of pili. In addition to the major pilus adhesin, exoenzyme S and, as recent studies indicate, flagella, are further protein adhesins of Pa with GSL receptor binding specificities similar to those of pili.     

The Genome of Streptococcus mitis B6 - What Is a Commensal?

Streptococcus mitis is the closest relative of the major human pathogen S. pneumoniae. The 2,15 Mb sequence of the Streptococcus mitis B6 chromosome, an unusually high-level beta-lactam resistant and multiple antibiotic resistant strain, has now been determined to encode 2100 genes. The accessory genome is estimated to represent over 40%, including 75 mostly novel transposases and IS, the prophage φB6 and another seven phage related regions. Tetracycline resistance mediated by Tn5801, and an unusual and large gene cluster containing three aminoglycoside resistance determinants have not been described in other Streptococcus spp. Comparative genomic analyses including hybridization experiments on a S. mitis B6 specific microarray reveal that individual S. mitis strains are almost as distantly related to the B6 strain as S. pneumoniae. Both species share a core of over 900 genes. Most proteins described as pneumococcal virulence factors are present in S. mitis B6, but the three choline binding proteins PcpA, PspA and PspC, and three gene clusters containing the hyaluronidase gene, ply and lytA, and the capsular genes are absent in S. mitis B6 and other S. mitis as well and confirm their importance for the pathogenetic potential of S. pneumoniae. Despite the close relatedness between the two species, the S. mitis B6 genome reveals a striking X-alignment when compared with S. pneumoniae.     

The Pseudomonas aeruginosa membranes: a target for a new amphiphilic aminoglycoside derivative?

Aminoglycosides are among the most potent antimicrobials to eradicate Pseudomonas aeruginosa. However, the emergence of resistance has clearly led to a shortage of treatment options, especially for critically ill patients. In the search for new antibiotics, we have synthesized derivatives of the small aminoglycoside, neamine. The amphiphilic aminoglycoside 3',4',6-tri-2-naphtylmethylene neamine (3',4',6-tri-2NM neamine) has appeared to be active against sensitive and resistant P. aeruginosa strains as well as Staphylococcus aureus strains (Baussanne et al., 2010). To understand the molecular mechanism involved, we determined the ability of 3',4',6-tri-2NM neamine to alter the protein synthesis and to interact with the bacterial membranes of P. aeruginosa or models mimicking these membranes. Using atomic force microscopy, we observed a decrease of P. aeruginosa cell thickness. In models of bacterial lipid membranes, we showed a lipid membrane permeabilization in agreement with the deep insertion of 3',4',6-tri-2NM neamine within lipid bilayer as predicted by modeling. This new amphiphilic aminoglycoside bound to lipopolysaccharides and induced P. aeruginosa membrane depolarization. All these effects were compared to those obtained with neamine, the disubstituted neamine derivative (3',6-di-2NM neamine), conventional aminoglycosides (neomycin B and gentamicin) as well as to compounds acting on lipid bilayers like colistin and chlorhexidine. All together, the data showed that naphthylmethyl neamine derivatives target the membrane of P. aeruginosa. This should offer promising prospects in the search for new antibacterials against drug- or biocide-resistant strains.     

The primary structure of the β-subunit of protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa

The complete amino acid sequence of the β-subunit of protocatechuate 3,4-dioxygenase was determined. The β-subunit contained four methionine residues. Thus, five peptides were obtained after cleavage of the carboxymethylated β-subunit with cyanogen bromide, and were isolated on Sephadex G-75 column chromatography. The amino acid sequences of the cyanogen bromide peptides were established by characterization of the peptides obtained after digestion with trypsin, chymotrypsin, thermolysin, or Staphylococcus aureus protease. The major sequencing techniques used were automated and manual Edman degradations. The five cyanogen bromide peptides were aligned by means of the amino acid sequences of the peptides containing methionine purified from the tryptic hydrolysate of the carboxymethylated β-subunit. The amino acid sequence of all the 238 residues was as follows: ProAlaGlnAspAsnSerArgPheValIleArgAsp ArgAsnTrpHis ProLysAlaLeuThrPro-Asp — TyrLysThrSerIleAlaArg SerProArgGlnAla LeuValSerIleProGlnSer — IleSerGluThrThrGly ProAsnPheSerHisLeu GlyPheGlyAlaHisAsp-His — AspLeuLeuLeuAsnPheAsn AsnGlyGlyLeu ProIleGlyGluArgIle-Ile — ValAlaGlyArgValValAsp GlnTyrGlyLysPro ValProAsnThrLeuValGluMet — TrpGlnAlaAsnAla GlyGlyArgTyrArg HisLysAsnAspArgTyrLeuAlaPro — LeuAspProAsn PheGlyGlyValGly ArgCysLeuThrAspSerAspGlyTyrTyr — SerPheArg ThrIleLysProGlyPro TyrProTrpArgAsnGlyProAsnAsp — TrpArgProAla HisIleHisPheGlyIle SerGlyProSerIleAlaThr-Lys — LeuIleThrGlnLeuTyr PheGluGlyAspPro LeuIleProMetCysProIleVal — LysSerIleAlaAsn ProGluAlaValGlnGln LeuIleAlaLysLeuAspMetAsnAsn — AlaAsnProMet AsnCysLeuAlaTyr ArgPheAspIleValLeuArgGlyGlnArgLysThrHis PheGluAsnCys. The sequence published earlier in summary form (Iwaki et al., 1979, J. Biochem.86, 1159–1162) contained a few errors which are pointed out in this paper.     

Does Streptococcus mitis,a neonatal oropharyngeal bacterium,influence the pathogenicity of Pseudomonas aeruginosa?

Microorganisms in a biofilm might promote or suppress each other. We previously found that Pseudomonas aeruginosa (P. aeruginosa) and the normal colonized bacteria in the oropharynx, Streptococcus mitis (S. mitis), were the most common bacteria in the biofilm found on newborns' endotracheal tubes. Here, we found that S. mitis enhanced the adhesion and biofilm formation of P. aeruginosa. Furthermore, it alleviated the immune response induced by P. aeruginosa. These findings remind us that we should not ignore the role of traditionally viewed non-pathogenic bacteria in biofilms and provide new insights into exploring bacterial interaction mechanisms in biofilm related infections.     

Susceptibility of Pseudomonas aeruginosa to catechol-substituted cephalosporin is unrelated to the pyochelin–Fe transporter FptA

Previously it has been postulated that the pyochelin–Fe outer membrane transporter, FptA, is involved in the uptake of catechol-substituted cephalosporins in Pseudomonas aeruginosa. Iron uptake and antibacterial activity studies on different mutants showed clearly that FptA is unable to bind and transport these antibiotics.     

Mutational Analysis of the Pseudomonas aeruginosa Myovirus ?KZ Morphogenetic Protease gp175

Pseudomonas aeruginosa myovirus ϕKZ has a 270-kb genome within a T=27 icosahedral capsid that contains a large, unusual, and structurally well-defined protein cylindrical inner body (IB) spanning its interior. Proteolysis forms a pivotal stage in ϕKZ head and IB morphogenesis, with the protease gp175 cleaving at least 19 of 49 different head proteins, including the major capsid protein and five major structural IB proteins. Here we show that the purified mature form of gp175 is active and cleaves purified IB structural proteins gp93 and gp89. Expression vector synthesis and purification of the zymogen/precursor yielded an active, mature-length protease, showing independent C-terminal gp175 self-cleavage autoactivation. Mutation of either the predicted catalytic serine or histidine inactivated mature gp175, supporting its classification as a serine protease and representing the first such direct biochemical demonstration with purified protease and substrate proteins for any phage protease. These mutations also blocked self-cleavage of the precursor while allowing intermolecular gp175 processing. To confirm the cleavage specificity of gp175, we mutated three cleavage sites in gp93, which blocked proteolysis at these sites. The N-terminal propeptide of gp93 was shown to undergo more extensive proteolysis than previously identified. We found that proteolysis in gp93 progressed from the N to C terminus, while blocking cleavage sites slowed but did not eliminate downstream proteolysis. These findings were shown by informatics to be relevant to the head morphogenesis of numbers of other related IB-containing giant phages as well as to T4 and herpesviruses, which have homologous proteases.     

Quantification of Excluded Volume Effects on the Folding Landscape of Pseudomonas aeruginosa Apoazurin In?Vitro

Proteins fold and function inside cells that are crowded with macromolecules. Here, we address the role of the resulting excluded volume effects by in vitro spectroscopic studies of Pseudomonas aeruginosa apoazurin stability (thermal and chemical perturbations) and folding kinetics (chemical perturbation) as a function of increasing levels of crowding agents dextran (sizes 20, 40, and 70 kDa) and Ficoll 70. We find that excluded volume theory derived by Minton quantitatively captures the experimental effects when crowding agents are modeled as arrays of rods. This finding demonstrates that synthetic crowding agents are useful for studies of excluded volume effects. Moreover, thermal and chemical perturbations result in free energy effects by the presence of crowding agents that are identical, which shows that the unfolded state is energetically the same regardless of method of unfolding. This also underscores the two-state approximation for apoazurin’s unfolding reaction and suggests that thermal and chemical unfolding experiments can be used in an interchangeable way. Finally, we observe increased folding speed and invariant unfolding speed for apoazurin in the presence of macromolecular crowding agents, a result that points to unfolded-state perturbations. Although the absolute magnitude of excluded volume effects on apoazurin is only on the order of 1–3 kJ/mol, differences of this scale may be biologically significant.     

Monalysin,a Novel ?-Pore-Forming Toxin from the Drosophila Pathogen Pseudomonas entomophila,Contributes to Host Intestinal Damage and Lethality

Pseudomonas entomophila is an entomopathogenic bacterium that infects and kills Drosophila. P. entomophila pathogenicity is linked to its ability to cause irreversible damages to the Drosophila gut, preventing epithelium renewal and repair. Here we report the identification of a novel pore-forming toxin (PFT), Monalysin, which contributes to the virulence of P. entomophila against Drosophila. Our data show that Monalysin requires N-terminal cleavage to become fully active, forms oligomers in vitro, and induces pore-formation in artificial lipid membranes. The prediction of the secondary structure of the membrane-spanning domain indicates that Monalysin is a PFT of the ß-type. The expression of Monalysin is regulated by both the GacS/GacA two-component system and the Pvf regulator, two signaling systems that control P. entomophila pathogenicity. In addition, AprA, a metallo-protease secreted by P. entomophila, can induce the rapid cleavage of pro-Monalysin into its active form. Reduced cell death is observed upon infection with a mutant deficient in Monalysin production showing that Monalysin plays a role in P. entomophila ability to induce intestinal cell damages, which is consistent with its activity as a PFT. Our study together with the well-established action of Bacillus thuringiensis Cry toxins suggests that production of PFTs is a common strategy of entomopathogens to disrupt insect gut homeostasis.     

Somatic antigens of Pseudomonas aeruginosa. The structure of the O-specific polysaccharide chains of P. aeruginosa O11 (Lányi) lipopolysaccharides

Lipopolysaccharides were isolated from the phenol layer on aqueous phenol extraction of cells of Pseudomonas aeruginosa O11 (Lányi classification), strains 170021 and 170040. On mild acid degradation of the lipopolysaccharides, with the subsequent gel-filtration on Sephadex G-50, neutral O-specific polysaccharides made up of 6-deoxysugars alone were obtained. Two 2-acetamido-2,6-dideoxy-L-galactose (LFucNAc), 2-acetamido-2,6-dideoxy-D-glucose (DQuiNAc) and L-rhamnose (LRha) residues were found to be the components of the strain 170021 polysaccharide repeating units; those of strain 170040 contained the same monosaccharides, but, instead of 2-acetamido-2,6-dideoxy-D-glucose residue, that of 2-acetamido-2,6-dideoxy-D-galactose (DFucNAc) was present. On the basis of the 13C nuclear magnetic resonance data, methylation analysis and three successive Smith degradations the following structures were determined for the polysaccharide repeating units: strain 170021----2) LRha(alpha 1----3)LFucNAc(alpha 1----3)LFucNAc(alpha 1----3)DQuiNAc(beta 1----; strain 170040,----2)LRha(alpha 1----3)LFucNAc-(alpha 1----3)LFucNAc(alpha 1----3)DFucNAc(beta 1----; differing from one another by configuration of C-4 of 2-acetamido-2,6-dideoxy-D-hexopyranose only.     

Presence of qacEΔ1 gene and susceptibility to a hospital biocide in clinical isolates of Pseudomonas aeruginosa resistant to antibiotics

Biocides play an important role in healthcare-associated infection control by either minimizing or preventing microorganism dissemination. This study evaluated the susceptibility of Pseudomonas aeruginosa clinical isolates to a quaternary ammonium (QAC) disinfectant and antibiotics, and verified the presence of qacEΔ1, a determinant of resistance to QAC. The disinfectant test was the Association of Official Analytical Chemists Use-Dilution Test, and polymerase chain reaction was used to examine for qacEΔ1. The qacEΔ1 gene was detected in 48% of the isolates. Eighty-eight percent of the multiresistant isolates carried qacEΔ1 gene, while 35% of the non-multiresistant isolates was positive to this gene, and multiresistance well correlated with its presence. Among isolates tested for the disinfectant, 46% showed a reduced susceptibility to the disinfectant. qacEΔ1 gene was present in 70% of the susceptible isolates to the biocide, whereas 90% of the less susceptible strains harbored this gene. Reduced susceptibility to the disinfectant was independent of presence of qacEΔ1 suggesting that it does not play an important role in biocide resistance in P. aeruginosa. As far as we know, it is the first report confirming this fact and testing with disinfectant at its in-use concentration. The evidence of less susceptible strains than the reference bacterium used in disinfectant testing, and the high percentage of qacEΔ1 gene detected are of special concern and suggests continued investigation in laboratory and in situ, not only in healthcare settings, but also in all areas of biocide usage, including different micro-organisms and biocides.     

Why Be Vigilant? The Case of the Alpha Animal

We compared patterns of vigilance behavior in a male- and a female-dominant species—white-faced capuchins and ring-tailed lemurs—and used the results to test four hypotheses to explain vigilance behavior in primates. Adult male white-faced capuchins spent significantly more time vigilant than females did, and much male vigilance appeared to be directed toward males from other social groups. This finding supports the protection of paternity hypothesis. No sex difference existed in vigilance behavior among the ring-tailed lemurs, and subjects of both sexes exhibited more vigilance toward predators/potential predators than toward extragroup conspecifics, which supports the predator detection hypothesis. A trade-off argument, suggesting that females tolerate males in a group in return for greater male vigilance, does not apply to ring-tailed lemurs in our study. In both the male-dominant capuchins and the female-dominant ring-tailed lemurs, the alpha subject in the majority of the study groups was significantly more vigilant than other group members were. In white-faced capuchins, the alpha male mates more often than subordinate males do; therefore, the greater degree of vigilance exhibited by the alpha male may correspond to the protection of his reproductive investment. In ring-tailed lemurs, there can be more than one matriline in a group. Thus, the greater amount of vigilance behavior exhibited by the alpha female may be related to protection of her matriline, which could ultimately lead to greater inclusive fitness. Alpha subjects in our study groups exhibited certain behaviors more frequently or exclusively. Accordingly, there may be a constellation of behaviors characteristic of alpha animals.