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

Ravens remember the nature of a single reciprocal interaction sequence over 2 days and even after a month

To explain reciprocity, direct or indirect, several proximate mechanisms have been proposed, yet little attention has been given to the specific underlying cognitive mechanisms. Regardless of what proximate rules underlie reciprocity, some kind of memory would be paramount. Corvids in general, and ravens, Corvus corax, specifically, have been shown to possess an array of sophisticated cognitive mechanisms involved in memory. In this study, we tested the memory of nine ravens in an exchange paradigm where they could exchange a low-quality for a high-quality food item. Specifically, we tested whether they remembered who was a reliable ‘fair’ experimenter and who would not reliably exchange (the ‘unfair’ experimenter), and whether they would subsequently choose to interact with the former when given the choice. In addition, we tested whether ravens that observed the initial seeding of information about who was ‘fair’ or ‘unfair’ could transform bystander information into first-person interactions, i.e. also preferring to interact with the ‘fair’ experimenter when given the choice. The results show that ravens with first-hand experience were more likely to interact with experimenters with whom they had had a positive previous experience, and that this memory lasted at least 1 month. In contrast, observers did not distinguish between the experimenters when given the choice to interact with them. Previous first-hand experience with the paradigm, however, seemed to help observers to be more successful in solving the task, albeit not significantly above chance. In sum, this study shows memory for direct reciprocity in ravens, and tentatively suggests memory for indirect reciprocity. Accordingly, these results provide hints for the underlying mechanism of memory in raven social interactions.FSW – Publicaties zonder aanstelling Universiteit Leide

Dziedzictwo mistrzów: uwagi o życiu i pracy z Profesorami Carolyn Ellis i Arthurem P. Bochnerem

On January 25th, 2019, The University of South Florida sponsored an event to honor the legacy of Carolyn Ellis and Arthur Bochner as they retire after more than 85 years (combined) teaching. In this paper, research collaborators, students, and friends present their testimonials commemorating their shared lives with Professors Ellis and Bochner. A collection of short stories reveals “official” and “non-official” (in some cases very personal) experiences as they were lived through, inviting readers to see how academic intergenerational relationships might develop as contextually situated and morally important.  25 stycznia 2019 r., w Uniwersytecie Południowej Florydy miało miejsce uroczyste spotkanie poświęcone aktywności akademickiej Carolyn Ellis i Arthura Bochnera, którzy po ponad osiemdziesięciu pięciu latach (łącznie) pracy dydaktycznej przeszli na emeryturę. Tekst został przygotowany przez naukowych współpracowników, studentów oraz przyjaciół Profesorów Ellis i Bochnera, by upamiętnić i uhonorować Ich dzieło, i stanowi zbiór krótkich historii. Ukazuje on zarówno „oficjalne”, jak i „nieoficjalne” (w niektórych wypadkach bardzo osobiste) doświadczenia związane z życiem i pracą Profesorów. Opowieści te zapraszają czytelników do świata akademickich relacji międzypokoleniowych, uwikłanych kontekstowo i ważnych z etycznego punktu widzenia. &nbsp

Pseudomonas aeruginosa is capable of natural transformation in biofilms

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 homologues 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

Fate of anthropogenic radionuclides (90Sr, 137Cs, 238Pu, 239Pu, 240Pu, 241Am) in seawater in the northern Benguela upwelling system off Namibia

A baseline study on anthropogenic radioactivity in the Namibian marine ecosystem, which is part of the northern Benguela upwelling system, known as one of the most productive ocean areas in the world, has been performed. A scientific cruise carried out in 2014 covering inshore and offshore areas, exhibiting different oceanographic features, has provided a basis for better understanding the distributions, ratios and inventories of six anthropogenic radionuclides (Sr, Cs, Pu, Pu, Pu and Am) in seawater. Although H was also measured, due to extremely low levels, its behaviour was not studied. The main source of Sr, Cs, Pu, Pu and Am in the samples analysed was proven to be global fallout, a finding further confirmed by Pu/Pu and Sr/Cs ratios. Furthermore, the Pu SNAP-9A satellite accident signal was confirmed once again through the determination of the Pu/Pu activity ratio. Inshore and offshore samples showed different patterns due to the unique oceanographic features of this upwelling system. The levels of anthropogenic radionuclides, comprehensively assessed for the first time in this region, are comparable with the few existing data and filled a critical gap for the Southern Atlantic Ocean.This work has been partly financed through the project PGC 2018-094546-B-I00 provided by the Spanish Government (Ministerio de Ciencia, Innovación y Universidades)

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

Chimpanzees (Pan troglodytes) Fail a What-Where-When Task but Find Rewards by Using a Location-Based Association Strategy

Recollecting the what-where-when of an episode, or episodic-like memory, has been established in corvids and rodents. In humans, a linkage between remembering the past and imagining the future has been recognised. While chimpanzees can plan for the future, their episodic-like memory has hardly been investigated. We tested chimpanzees (Pan troglodytes) with an adapted food-caching paradigm. They observed the baiting of two locations amongst four and chose one after a given delay (15 min, 1 h or 5 h). We used two combinations of food types, a preferred and a less preferred food that disappeared at different rates. The subjects had to base their choices on the time elapsed since baiting, and on their memory of which food was where. They could recover either their preferred food or the one that remained present. All animals failed to obtain the preferred or present foods above chance levels. They were like-wise unsuccessful at choosing baited cups above chance levels. The subjects, thus, failed to use any feature of the baiting events to guide their choices. Nonetheless, their choices were not random, but the result of a developed location-based association strategy. Choices in the second half of the study correlated with the rewards obtained at each location in the first half of the study, independent from the choices made for each location in the first half of the study. This simple location-based strategy yielded a fair amount of food. The animals' failure to remember the what-where-when in the presented set-up may be due to the complexity of the task, rather than an inability to form episodic-like memories, as they even failed to remember what was where after 15 minutes

Seasonal patterns and relationships among coccidian infestations, measures of oxidative physiology, and immune function in free-living house sparrows over an annual cycle

Temporal variation in oxidative physiology and its associated immune function may occur as a result of changes in parasite infection over the year. Evidence from field and laboratory studies suggests links between infection risk, oxidative stress, and the ability of animals to mount an immune response; however, the importance of parasites in mediating seasonal change in physiological makeup is still debated. Also, little is known about the temporal consistency of relationships among parasite infestation, markers of oxidative status and immune function in wild animals, and whether variation in oxidative measures can be viewed as a single integrated system. To address these questions, we sampled free-living house sparrows (Passer domesticus) every 2 mo over a complete year and measured infestation with coccidian parasites as well as nine traits that reflect condition, oxidative physiology, and immune function. We found significant seasonal variation in coccidian infestation and in seven out of nine condition and physiological variables over the year. However, we found little support for parasite-mediated change in condition, oxidative physiology, and immune functions in house sparrows. In accordance with this, we found no temporal consistency in relationships between the intensity of infestation and physiology. Among measures of oxidative physiology, antioxidants (measured as the total antioxidant capacity and the concentration of uric acid in the plasma) and oxidative damage (measured through the level of malondialdehyde in plasma) positively and consistently covaried over the year, while no such associations were found for the rest of traits (body mass, total glutathione, and leukocyte numbers). Our results show that natural levels of chronic coccidian infection have a limited effect on the seasonal change of physiological traits, suggesting that the variation of the latter is probably more affected by short-term disturbances, such as acute infection and/or season-specific stress stimuli

Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil : results of the IAEA–UNESCO SGD project

Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Environmental Radioactivity 99 (2008): 1596-1610, doi:10.1016/j.jenvrad.2008.06.010.Results of groundwater and seawater analyses for radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes are presented together with in situ spatial mapping and time-series 222Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d-1 to 360 cm d-1; the unit represents cm3/cm2/day), as well as during a few hours (from 0 cm d-1 to 110 cm d-1), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous 222Rn measurements is 17±10 cm d-1. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7x103 m3 d-1 per km of the coast. The isotopic composition (δ2H and δ18O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time-series measurements of 222Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1-2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.This research was supported by IAEA and UNESCO (IOC and IHP) in the framework of the joint SGD project. Science support for some U.S. investigators was provided by grants from the National Science Foundation (OCE03-50514 to WCB and OCE02-33657 to WSM)

Risk factors for suicide in Hungary: a case-control study

<p>Abstract</p> <p>Background</p> <p>Hungary previously had one of the highest suicide rates in the world, but experienced major social and economic changes from 1990 onwards. We aimed to investigate the antecedents of suicide in Hungary. We hypothesised that suicide in Hungary would be associated with both risk factors for suicide as identified in Western studies, and experiences related to social and economic restructuring.</p> <p>Methods</p> <p>We carried out a controlled psychological autopsy study. Informants for 194 cases (suicide deaths in Budapest and Pest County 2002–2004) and 194 controls were interviewed by clinicians using a detailed schedule.</p> <p>Results</p> <p>Many of the demographic and clinical risk factors associated with suicide in other settings were also associated with suicide in Hungary; for example, being unmarried or having no current relationship, lack of other social contacts, low educational attainment, history of self-harm, current diagnosis of affective disorder (including bipolar disorder) or personality disorder, and experiencing a recent major adverse life event. A number of variables reflecting experiences since economic restructuring were also associated with suicide; for example, unemployment, concern over work propects, changes in living standards, practising religion. Just 20% of cases with evidence of depression at the time of death had received antidepressants.</p> <p>Conclusion</p> <p>Suicide rates in Hungary are falling. Our study identified a number of risk factors related to individual-level demographic and clinical characteristics, and possibly recent societal change. Improved management of psychiatric disorder and self-harm may result in further reductions in suicide rates.</p