Measurement of binding forces intrinsic to adhesion molecules is necessary to assess their contribution to the maintenance of the anatomical integrity of multicellular organisms. Atomic force microscopy was used to measure the binding strength between cell adhesion proteoglycans from a marine sponge. Under physiological conditions, the adhesive force between two cell adhesion molecules was found to be up to 400 piconewtons. Thus a single pair of molecules could hold the weight of 1600 cells. High intermolecular binding forces are likely to form the basis for the integrity of the multicellular sponge organism.

The approach of combining different mechanisms of antibacterial action by designing hybrid nanomaterials provides a new paradigm in the fight against resistant bacteria. Here, we present a new method for the synthesis of silver nanoparticles enveloped in the biopolymer chitosan. The method aims at the production of bionanocomposites with enhanced antibacterial properties. We find that chitosan and silver nanoparticles act synergistically against two strains of Gram-positive Staphylococcus aureus (S. aureus). As a result the bionanocomposites exhibit higher antibacterial activity than any component acting alone. The minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations of the chitosan-silver nanoparticles synthesized at 0 °C were found to be lower than those reported for other types of silver nanoparticles. Atomic force microscopy (AFM) revealed dramatic changes in morphology of S. aureus cells due to disruption of bacterial cell wall integrity after incubation with chitosan-silver nanoparticles. Finally, we demonstrate that silver nanoparticles can be used not only as antibacterial agents but also as excellent plasmonic substrates to identify bacteria and monitor the induced biochemical changes in the bacterial cell wall via surface enhanced Raman scattering (SERS) spectroscopy.

The recent discovery of a vestigial, nonphotosynthetic plastid (“apicoplast”) in the Apicomplexa has considerably modified our perception of the evolutionary origin of these parasites. Phylogenetic analysis and the presence of four surrounding membranes of the apicoplast provide important support for the hypothesis that apicomplexans have acquired their apicoplast by secondary endosymbiosis, probably from a green alga. This suggests that genes encoding predicted homologs of proteins of green algae or related photosynthetic lineages could have entered the nucleus of apicomplexan parasites by transfer from the ancestor harboring the apicoplast. We describe here complementary DNAs encoding two Toxoplasma gondii glycolytic enzymes, glucose-6-phosphate isomerase (G6-PI) and enolase, which have considerable identities with land plant counterparts. Both cDNAs of T. gondii complementEscherichia coli mutants lacking G6-PI and enolase genes and lead to the expression of active enzymes. In the drug untreatable encysted bradyzoites of T. gondii, G6-PI and enolase genes are overexpressed or exclusively expressed at both transcriptional and protein levels. Moreover, three-dimensional models and protein phylogeny confirmed that G6-PIs and enolases of T. gondii,Plasmodium falciparum, and land plants are closely related. Because these glycolytic enzymes are plant homologs, which differ from those of animals, they will be useful to trace the evolutionary origin of Apicomplexa and might offer novel chemotherapeutic targets in diseases caused by apicomplexan parasites.