Adhesion of Acinetobacter spp. to para-xylene

Hydrophobicity of 200 of Acinetobacter spp. strains was defined by the BATH (Bacterial Adhesion to Hydrocarbon Test) method of Rosenberg et al. 48.0% strains of Acinetobacter spp. adhered to para-xylene. 40.0% of strains showed waek hydrophobicity, 7.5% moderate and one strain strongly adhered to para-xylene. A. baumannii strains adhered in 52.2%, A. junii in 42.1% and 20.0% in A. haemolyticus. Significantly we find weak adhesion to para-xylene than mild and strong. Mostly adhesion was discovered in A. baumannii and A. junii than in A. haemolyticus. Results show that Acinetobacter spp. has adhesive properties to para-xylene.     

The Activity of Hyaluronan Synthase 2 Is Regulated by Dimerization and Ubiquitination

Hyaluronan is a component of the extracellular matrix, which affects tissue homeostasis. In this study, we investigated the regulatory mechanisms of one of the hyaluronan-synthesizing enzymes, HAS2. Ectopic expression of Flag- and 6myc-HAS2 in COS-1 cells followed by immunoprecipitation and immunoblotting revealed homodimers; after co-transfection with Flag-HAS3, also heterodimers were seen. Furthermore, the expressed HAS2 was ubiquitinated. We identified one acceptor site for ubiquitin on lysine residue 190. Mutation of this residue led to inactivation of the enzymatic activity of HAS2. Interestingly, K190R-mutated HAS2 formed dimers with wt HAS2 and quenched the activity of wt HAS2, thus demonstrating a functional role of the dimeric configuration.     

Structural determination of the Nod factors produced by Rhizobium gallicum bv. gallicum R602

Rhizobium gallicum is a fast-growing bacterium found in European, Australian and African soils; it was first isolated in France. It is a microsymbiont which is able to nodulate plants of the genus Phaseolus. Rhizobium gallicum bv. gallicum R602 produces four extracellular signal molecules consisting of a linear backbone of N-acetyl glucosamine, bearing on the nonreducing terminal residue an N-methyl group and different N-acyl substituents. The four acyloligosaccharides terminate with a sulfated N-acetylglucosaminitol. This unit may be also acetylated. These structures were determined using carbohydrate and methylation analysis, mass spectrometric analysis and one-dimensional- and two-dimensional-nuclear magnetic resonance experiments. This work establishes the common structure that a lipochito-oligosaccharide must have so that the Rhizobium that produces and excretes it is able to nodulate plants of Phaseolus vulgaris. The substituents common to all the molecules are an N-methyl group and a C(18:1) fatty acid on the nonreducing terminal residue.     

Adenylate cyclase influences filamentous haemagglutinin-mediated attachment of Bordetella pertussis to epithelial alveolar cells

Attachment to epithelial cells in the respiratory tract is a key event in Bordetella pertussis colonization. Filamentous haemagglutinin (FHA) is an important virulence factor mediating adhesion to host cells. In this study, the relevance of the interaction between FHA and adenylate cyclase toxin (ACT) during bacterial attachment was investigated. Mutants lacking either FHA or ACT showed significantly decreased adherence to epithelial respiratory cells. The use of several ACT-specific monoclonal antibodies and antiserum showed that the decrease in attachment of strains lacking ACT expression could not be explained by the adhesin-like activity of ACT, or a change of any of the biological activities of ACT. Immunoblot analysis showed that the lack of ACT expression did not interfere with FHA localization. An heparin-inhibitable carbohydrate-binding site is crucial in the process of FHA-mediated bacterial binding to epithelial cells. In the presence of heparin attachment of wild-type B. pertussis, but not of the isogenic ACT defective mutant, to epithelial cells was significantly decreased. These results suggest that ACT enhances the adhesive functions of FHA, and modifies the performance of the FHA heparin-inhibitable carbohydrate binding site. We propose that the presence of ACT in the outer membrane of B. pertussis to play a role in the functionality of FHA.     

A caudal mRNA gradient controls posterior development in the wasp Nasonia

One of the earliest steps of embryonic development is the establishment of polarity along the anteroposterior axis. Extensive studies of Drosophila embryonic development have elucidated mechanisms for establishing polarity, while studies with other model systems have found that many of these molecular components are conserved through evolution. One exception is Bicoid, the master organizer of anterior development in Drosophila and higher dipterans, which is not conserved. Thus, the study of anteroposterior patterning in insects that lack Bicoid can provide insight into the evolution of the diversity of body plan patterning networks. To this end, we have established the long germ parasitic wasp Nasonia vitripennis as a model for comparative studies with Drosophila. Here we report that, in Nasonia, a gradient of localized caudal mRNA directs posterior patterning, whereas, in Drosophila, the gradient of maternal Caudal protein is established through translational repression by Bicoid of homogeneous caudal mRNA. Loss of caudal function in Nasonia results in severe segmentation defects. We show that Nasonia caudal is an activator of gap gene expression that acts far towards the anterior of the embryo, placing it atop a cascade of early patterning. By contrast, activation of gap genes in flies relies on redundant functions of Bicoid and Caudal, leading to a lack of dramatic action on gap gene expression: caudal instead plays a limited role as an activator of pair-rule gene expression. These studies, together with studies in short germ insects, suggest that caudal is an ancestral master organizer of patterning, and that its role has been reduced in higher dipterans such as Drosophila.     

Demographic Expansion and Subtle Differentiation in the Long-Tailed Hake Macruronus magellanicus: Evidence from Microsatellite Data

The impact of geographic heterogeneity and historical demographic factors on genetic diversity in the commercially exploited hake Macruronus magellanicus was examined applying microsatellite markers. A total of 450 fish from 6 different sites, collected in Atlantic Patagonia, were genotyped at 6 polymorphic loci. While analysis of variance-based methods (Fst-Rst) failed to detect differentiation, the exact test for genic differentiation and factorial correspondence analysis revealed subtle differences between coastal and continental shelf edge samples. Data suggest that M. magellanicus has been subjected to a demographic expansion 2.6 to 5 times its original size thatoccurred approximately 100,000 to 200,000 years ago. Another more recent expansion seems to have occurred a few generations ago. Implications of subtle structuring and demographic instability are discussed.