Pseudomonas aeruginosa is capable of natural transformation in biofilms

Abstract Natural transformation is a mechanism that enables competent bacteria to acquire naked, exogenous DNA from the environment. It is a key process that facilitates the dissemination of antibiotic resistance and virulence determinants throughout bacterial populations. Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that produces large quantities of extracellular DNA (eDNA) that is required for biofilm formation. P. aeruginosa has a remarkable level of genome plasticity and diversity that suggests a high degree of horizontal gene transfer and recombination but is thought to be incapable of natural transformation. Here we show that P. aeruginosa possesses homologs of all proteins known to be involved in natural transformation in other bacterial species. We found that P. aeruginosa in biofilms is competent for natural transformation of both genomic and plasmid DNA. Furthermore, we demonstrate that type IV pili (T4P) facilitate but are not absolutely essential for natural transformation in P. aeruginosa

From photons to protons in the photocycle of bacterial reaction center

The detailed knowledge of the atomic coordinates of the bacterial reaction center (RC) has permitted a close scrutiny of structure/function relationships not only of the quinones but of the protein itself with its internal water structure. Protonatable groups were identified as intrinsic part of the redox reactions, providing charge compensation and forming channels for the movement of hydrogen ions to QB2-. The nature and position of these groups give rise to electrostatic profiles that determine the kinetics and energetics of proton transport. Fine tuning or dramatic variations of protein delivery pathways can adapt the photocycle to changes in bulk phase pH value, buffering capacities and primary structure of the RC

Explosive cell lysis as a mechanism for the biogenesis of bacterial membrane vesicles and biofilms

Many bacteria produce extracellular and surface-associated components such as membrane vesicles (MVs), extracellular DNA and moonlighting cytosolic proteins for which the biogenesis and export pathways are not fully understood. Here we show that the explosive cell lysis of a sub-population of cells accounts for the liberation of cytosolic content in Pseudomonas aeruginosa biofilms. Super-resolution microscopy reveals that explosive cell lysis also produces shattered membrane fragments that rapidly form MVs. A prophage endolysin encoded within the R- and F-pyocin gene cluster is essential for explosive cell lysis. Endolysin-deficient mutants are defective in MV production and biofilm development, consistent with a crucial role in the biogenesis of MVs and liberation of extracellular DNA and other biofilm matrix components. Our findings reveal that explosive cell lysis, mediated through the activity of a cryptic prophage endolysin, acts as a mechanism for the production of bacterial MVs

Master athletes have higher miR-7, SIRT3 and SOD2 expression in skeletal muscle than age-matched sedentary controls.

Regular physical exercise has health benefits and can prevent some of the ageing-associated muscle deteriorations. However, the biochemical mechanisms underlying this exercise benefit, especially in human tissues, are not well known. To investigate, we assessed this using miRNA profiling, mRNA and protein levels of anti-oxidant and metabolic proteins in the vastus lateralis muscle of master athletes aged over 65 years and age-matched controls. Master athletes had lower levels of miR-7, while mRNA or protein levels of SIRT3, SIRT1, SOD2, and FOXO1 levels were significantly higher in the vastus lateralis muscle of master athletes compared to muscles of age-matched controls. These results suggest that regular exercise results in better cellular metabolism and antioxidant capacity via maintaining physiological state of mitochondria and efficient ATP production and decreasing ageing-related inflammation as indicated by the lower level of miR-7 in master athletes

Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412)

The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified radionuclides include: 40K, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 234U, 238U, 239Pu, 239+240Pu and 241Am for IAEA-410 and 40K, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 235U, 238U, 239Pu, 240Pu and 239+240Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes in the analysis of radionuclides in sediments, for development and validation of analytical methods and for staff training