Tolerance of low pH exposure by the eggs of Odonata (dragonflies and damselflies)

The development times and hatching success of the eggs of four species of Odonata (Ischnura verticalis, Lestes congener, Libellula lydia, and Sympetrum vicinum) were unaffected by exposure to soft water at pH 5.1 and 3.5. Tolerance of low pH, soft water conditions by Odonata eggs may in part account for the widespread distribution of Odonata in potentially acid-stressed regions.     

A role for collagen IV cross-links in conferring immune privilege to the Goodpasture autoantigen: structural basis for the crypticity of B cell epitopes

The detailed structural basis for the cryptic nature (crypticity) of a B cell epitope harbored by an autoantigen is unknown. Because the immune system may be ignorant of the existence of such "cryptic" epitopes, their exposure could be an important feature in autoimmunity. Here we investigated the structural basis for the crypticity of the epitopes of the Goodpasture autoantigen, the alpha3alpha4alpha5 noncollagenous-1 (NC1) hexamer, a globular domain that connects two triple-helical molecules of the alpha3alpha4alpha5 collagen IV network. The NC1 hexamer occurs in two isoforms as follows: the M-isoform composed of monomer subunits in which the epitopes are accessible to autoantibodies, and the D-isoform composed of both monomer and dimer subunits in which the epitopes are cryptic. The D-isoform was characterized with respect to quaternary structure, as revealed by mass spectrometry of dimer subunits, homology modeling, and molecular dynamics simulation. The results revealed that the D-isoform contains two kinds of cross-links as follows: S-hydroxylysyl-methionine and S-lysyl-methionine cross-links, which stabilize the alpha3alpha5-heterodimers and alpha4alpha4-homodimers, respectively. Construction and analysis of a three-dimensional model of the D-isoform of the alpha3alpha4alpha5 NC1 hexamer revealed that crypticity is a consequence of the following: (a) sequestration of key residues between neighboring subunits that are stabilized by domain-swapping interactions, and (b) by cross-linking of subunits at the trimer-trimer interface, which stabilizes the structural integrity of the NC1 hexamer and protects against binding of autoantibodies. The sequestrated epitopes and cross-linked subunits represent a novel structural mechanism for conferring immune privilege at the level of quaternary structure. Perturbation of the quaternary structure may be a key factor in the etiology of Goodpasture disease.     

Pseudomonas aeruginosa PqsA is an anthranilate-coenzyme A ligase

Pseudomonas aeruginosa is an opportunistic human pathogen which relies on several intercellular signaling systems for optimum population density-dependent regulation of virulence genes. The Pseudomonas quinolone signal (PQS) is a 3-hydroxy-4-quinolone with a 2-alkyl substitution which is synthesized by the condensation of anthranilic acid with a 3-keto-fatty acid. The pqsABCDE operon has been identified as being necessary for PQS production, and the pqsA gene encodes a predicted protein with homology to acyl coenzyme A (acyl-CoA) ligases. In order to elucidate the first step of the 4-quinolone synthesis pathway in P. aeruginosa, we have characterized the function of the pqsA gene product. Extracts prepared from Escherichia coli expressing PqsA were shown to catalyze the formation of anthraniloyl-CoA from anthranilate, ATP, and CoA. The PqsA protein was purified as a recombinant His-tagged polypeptide, and this protein was shown to have anthranilate-CoA ligase activity. The enzyme was active on a variety of aromatic substrates, including benzoate and chloro and fluoro derivatives of anthranilate. Inhibition of PQS formation in vivo was observed for the chloro- and fluoroanthranilate derivatives, as well as for several analogs which were not PqsA enzymatic substrates. These results indicate that the PqsA protein is responsible for priming anthranilate for entry into the PQS biosynthetic pathway and that this enzyme may serve as a useful in vitro indicator for potential agents to disrupt quinolone signaling in P. aeruginosa.     

Civilian and military genetics: nondiscrimination policy in a post-GINA world

Evidence is emerging of a growing societal consensus about appropriate and inappropriate uses of genetic information. The Genetic Information Nondiscrimination Act of 2008 provides new legal protections to Americans by prohibiting the discriminatory use of genetic information by health insurers and employers. Additionally, the United States military recently created new policies for fair use of genetic information in the determination of benefits for servicemen and servicewomen leaving military service. Although critical issues remain, such as the potential for genetic information to be used to deny people other forms of insurance, and how the military will use genetic medicine overall, significant progress has been made.     

Pathogen interactions, population cycles, and phase shifts

Interspecific pathogen interactions can profoundly affect pathogen population dynamics and the efficacy of control strategies. However, many pathogens exhibit cyclic abundance patterns (e.g., seasonality), and temporal asynchrony between interacting pathogens could reduce the impact of those interactions. Here we use an extension of our previously published model to investigate the effects of cycles on pathogen interaction. We demonstrate that host immune memory can maintain the impact of an interaction, even when the effector pathogen abundance is low or the pathogen is absent. Paradoxically, immune memory can result in pathogens interacting more strongly when temporally out of phase. We find that interactions between species can result in changes to the temporal pattern of the affected species. We further demonstrate that this may be observed in a natural host-pathogen system. Given the continuing debate regarding the relevance of pathogen interactions in natural systems and increasing concern about treatment strategies for coinfections, both the discovery of a shift in cycle in empirical data and the mechanism by which we identified it are important. Finally, because the model structure used here is analogous to models of a simple predator-prey system, we also consider the consequences of these findings in the context of that system.     

Benefits of foundress associations in the paper wasp Polistes dominulus: increased productivity and survival, but no assurance of fitness returns

Successful Polistes dominulus nests can be started by one ormore nest founding queens (foundresses). Consequently, thereis much interest in the specific benefits that induce cooperationamong foundresses. Here, we experimentally demonstrate one majorbenefit of cooperation, namely that multiple foundresses increasecolony productivity. This increase is close to the value predictedby subtracting the productivity of undisturbed single-foundresscolonies from the productivity of undisturbed multiple-foundresscolonies. However, we found no evidence that an associatingfoundress' contribution to colony growth is preserved if shedisappears (assured fitness returns). Our correlational datasuggest that cooperation provides survival benefits, multiple-foundresscolonies are more likely to survive to produce offspring thanare single-foundress colonies, and individual foundresses inmultiple-foundress groups are less likely to disappear beforeworker emergence than foundresses nesting alone. Therefore,association provides substantial productivity and survival benefitsfor cooperating foundresses.