DNA Uptake by Type IV Filaments

Bacterial uptake of DNA through type IV filaments is an essential component of natural competence in numerous gram-positive and gram-negative species. Recent advances in the field have broadened our understanding of the structures used to take up extracellular DNA. Here, we review seminal experiments in the literature describing DNA binding by type IV pili, competence pili and the flp pili of Micrococcus luteus; collectively referred to here as type IV filaments. We compare the current state of the field on mechanisms of DNA uptake for these three appendage systems and describe the current mechanistic understanding of both DNA-binding and DNA-uptake by these versatile molecular machines

DNA Uptake by Type IV Filaments

Bacterial uptake of DNA through type IV filaments is an essential component of natural competence in numerous gram-positive and gram-negative species. Recent advances in the field have broadened our understanding of the structures used to take up extracellular DNA. Here, we review seminal experiments in the literature describing DNA binding by type IV pili, competence pili and the flp pili of Micrococcus luteus; collectively referred to here as type IV filaments. We compare the current state of the field on mechanisms of DNA uptake for these three appendage systems and describe the current mechanistic understanding of both DNA-binding and DNA-uptake by these versatile molecular machines

\u3ci\u3eClostridium perfringens\u3c/i\u3e Adhesion Through Type IV Pili

Bacteria infect host cells through several mechanisms, one of which is a surface protein called a type IV pilus. Type IV pili are thin, hair-like protein fibers on the bacterial surface capable of being extended and retracted from a bacterial cell; they are used for functions including motility, biofilm formation, and adherence to host cells. Clostridium perfringens is a Gram-positive bacterium best known as a food pathogen that is believed to use type IV pili for host cell adherence. These pili are poorly characterized and understanding how C. perfringens uses type IV pili will provide a model for how these pili are used in similar Clostridia species. This project has produced crystals of the PilA2 pilin protein from C. perfringens that can diffract with X-ray crystallography, though these crystals did not diffract with enough resolution for structure elucidation. Pending the production of crystals with better diffraction, this diffraction data will be used to solve the structure of the pilin protein and construct a model of type IV pili in C. perfringens

Comment on Martinez-Garcia et al. 'Heavy metals in human bones in different historical epochs'.

Martínez-García et al. (Sci. Tot Env. 348:51–72) have examined heavy metal exposure of humans in the Cartagena region using analysis of archaeological bones. An analysis of the lead and iron levels they report shows that they are physiologically implausible and must therefore result from diagenesis. This, and analogy with the known diagenetic origin of certain other elements, suggests that the other metal analyses they report are also unlikely to be in vivo concentrations. Lifetime heavy metal exposure cannot be deduced from diagenetically altered concentrations