Identification and characterization of 10 polymorphic microsatellite loci in the German cockroach,Blattella germanica

Primer sequences and initial characterization are presented for 10 microsatellite loci isolated from the German cockroach, Blattella germanica. In a sample of 30 individuals from a single population sample, all loci were polymorphic with two to 12 alleles segregating per locus and levels of observed heterozygosity ranging from 0.27 to 0.92. One locus showed a deficit of heterozygotes. Experimental conditions are described for polymerase chain reaction multiplexing, which enables the genotyping of eight loci in three electrophoretic runs consisting of one set of three and two sets of two markers. Seven primer sets cross‐amplify in the related Blattella asahinai.     

Crystal structures of two intermediates in the assembly of the papillomavirus replication initiation complex

Initiation of DNA replication of the papillomavirus genome is a multi-step process involving the sequential loading of viral E1 protein subunits onto the origin of replication. Here we have captured structural snapshots of two sequential steps in the assembly process. Initially, an E1 dimer binds to adjacent major grooves on one face of the double helix; a second dimer then binds to another face of the helix. Each E1 monomer has two DNA-binding modules: a DNA-binding loop, which binds to one DNA strand and a DNA-binding helix, which binds to the opposite strand. The nature of DNA binding suggests a mechanism for the transition between double- and single-stranded DNA binding that is implicit in the progression to a functional helicase.     

Pulsed EPR investigations of the Mo(V) centers of the R55Q and R55M variants of sulfite dehydrogenase from Starkeya novella

Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopy have been used to characterize two variants of bacterial sulfite dehydrogenase (SDH) from Starkeya novella in which the conserved active-site arginine residue (R55) is replaced by a neutral amino acid residue. Substitution by the hydrophobic methionine residue (SDH^R55M) has essentially no effect on the pH dependence of the EPR properties of the Mo(V) center, even though the X-ray structure of this variant shows that the methionine residue is rotated away from the Mo center and a sulfate anion is present in the active-site pocket (Bailey et al. in J Biol Chem 284:2053–2063, 2009). For SDH^R55M only the high-pH form is observed, and samples prepared in H₂ ¹⁷O-enriched buffer show essentially the same ¹⁷O hyperfine interaction and nuclear quadrupole interaction parameters as SDH^WT enzyme. However, the pH dependence of the EPR spectra of SDH^R55Q, in which the positively charged arginine is replaced by the neutral hydrophilic glutamine, differs significantly from that of SDH^WT. For SDH^R55Q the blocked form with bound sulfate is generated at low pH, as verified by ³³S couplings observed upon reduction with ³³S-labeled sulfite. This observation of bound sulfate for SDH^R55Q supports our previous hypothesis that sulfite-oxidizing enzymes can exhibit multiple pathways for electron transfer and product release (Emesh et al. in Biochemistry 48:2156–2163, 2009). At pH ≥ 8 the high-pH form dominates for SDH^R55Q.     

Reshaping of sandstone surfaces by cryptoendolithic cyanobacteria: bioalkalization causes chemical weathering in arid landscapes

We report a novel weathering mechanism in South African sandstone formations, where cryptoendolithic cyanobacteria induce weathering by substrate alkalization during photosynthesis. As a result, the upper rock part is loosened and then eroded away by physical forces such as wind, water, trampling. This special type of ‘exfoliation’ is widely distributed and affects the geomorphology of whole sandstone mountain ranges and outcrops across several biomes. We show, that this weathering type is initiated by bioalkalization because of the photosynthesis of cryptoendolithic (i.e. those organisms living in small tight open spaces between the sand grains) cyanobacteria causing pH values high enough to enhance silica solution in the cryptoendolithic zone. As modern cyanobacteria are the initial photoautotrophic colonizers of bare rocks in arid and semiarid landscapes, it is possible that they may also have played a significant role in shaping sandstone landscapes in the geological past.     

Linear and threshold-dependent expression of secondary sexual traits in the same individual: insights from a horned beetle (Coleoptera: Scarabaeidae)

Elaborate horns or horn‐like structures in male scarab beetles commonly scale with body size either (a) in a linear fashion with horn size increasing relatively faster than body size or (b) in a threshold‐dependent, sigmoid fashion; that is, males smaller than a certain critical body size develop no or only rudimentary horns, whereas males larger than the threshold size express fully developed horns. The development of linear vs. sigmoid scaling relationships is thought to require fundamentally different regulatory mechanisms. Here we show that such disparate regulatory mechanisms may co‐occur in the same individual. Large males of the south‐east Asian Onthophagus (Proagoderus) watanabei (Ochi & Kon) (Scarabaeidae, Onthophagini) develop a pair of long, curved head horns as well as a single thoracic horn. We show that unlike paired head horns in a large number of Onthophagus species, in O. watanabei the relationship between head horns and body size is best explained by a linear model. Large males develop disproportionately longer horns than small males, but the difference in relative horn sizes across the range of body sizes is small compared to other Onthophagus species. However, the scaling relationship between the thoracic horn and body size is best explained by a strongly sigmoid model. Only males above a certain body size threshold express a thoracic horn and males smaller than this threshold express no horn at all. We found a significant positive correlation between head and thoracic horn length residuals, contrary to what would be expected if a resource allocation tradeoff during larval development would influence the length of both horn types. Our results suggest that the scaling relationship between body size and horn length, and the developmental regulation underlying these scaling relationships, may be quite different for different horns, even though these horns may develop in the same individual. We discuss our results in the context of the developmental biology of secondary sexual traits in beetles. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83 , 473–480.     

Combined monte carlo and molecular dynamics simulation of fully hydrated dioleyl and palmitoyl-oleyl phosphatidylcholine lipid bilayers

We have applied a new equilibration procedure for the atomic level simulation of a hydrated lipid bilayer to hydrated bilayers of dioleyl-phosphatidylcholine (DOPC) and palmitoyl-oleyl phosphatidylcholine (POPC). The procedure consists of alternating molecular dynamics trajectory calculations in a constant surface tension and temperature ensemble with configurational bias Monte Carlo moves to different regions of the configuration space of the bilayer in a constant volume and temperature ensemble. The procedure is applied to bilayers of 128 molecules of POPC with 4628 water molecules, and 128 molecules of DOPC with 4825 water molecules. Progress toward equilibration is almost three times as fast in central processing unit (CPU) time compared with a purely molecular dynamics (MD) simulation. Equilibration is complete, as judged by the lack of energy drift in 200-ps runs of continuous MD. After the equilibrium state was reached, as determined by agreement between the simulation volume per lipid molecule with experiment, continuous MD was run in an ensemble in which the lateral area was restrained to fluctuate about a mean value and a pressure of 1 atm applied normal to the bilayer surface. Three separate continuous MD runs, 200 ps in duration each, separated by 10,000 CBMC steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of POPC and DOPC. Analysis of the hydration environment in the headgroups supports a mechanism by which unsaturation contributes to reduced transition temperatures. In this view, the relatively horizontal orientation of the unsaturated bond increases the area per lipid, resulting in increased water penetration between the headgroups. As a result the headgroup-headgroup interactions are attenuated and shielded, and this contributes to the lowered transition temperature.