Natural Shifts in Endosymbionts' Occurrence and Relative Frequency in Their Ciliate Host Population

The role of bacterial endosymbionts harbored by heterotrophic Paramecium species is complex. Obligate intracellular bacteria supposedly always inflict costs as the host is the only possible provider of resources. However, several experimental studies have shown that paramecia carrying bacterial endosymbionts can benefit from their infection. Here, we address the question which endosymbionts occur in natural paramecia populations isolated from a small lake over a period of 5 years and which factors might explain observed shifts and persistence in the symbionts occurrence. One hundred and nineteen monoclonal strains were investigated and approximately two-third harbored intracellular bacteria. The majority of infected paramecia carried the obligate endosymbiotic “Candidatus Megaira polyxenophila”, followed by Caedimonas varicaedens, and Holospora undulata. The latter was only detected in a single strain. While “Ca. M. polyxenophila” was observed in seven out of 13 samplings, C. varicaedens presence was limited to a single sampling occasion. After the appearance of C. varicaedens, “Ca. M. polyxenophila” prevalence dramatically dropped with some delay but recovered to original levels at the end of our study. Potential mechanisms explaining these observations include differences in infectivity, host range, and impact on host fitness as well as host competitive capacities. Growth experiments revealed fitness advantages for infected paramecia harboring “Ca. M. polyxenophila” as well as C. varicaedens. Furthermore, we showed that cells carrying C. varicaedens gain a competitive advantage from the symbiosis-derived killer trait. Other characteristics like infectivity and overlapping host range were taken into consideration, but the observed temporal persistence of “Ca. M. polyxenophila” is most likely explained by the positive effect this symbiont provides to its host.

A Peptide-Based Assay Discriminates Individual Antibody Response to the COVID-19 Pfizer/BioNTech mRNA Vaccine

The coronavirus disease 2019 (COVID-19) mRNA vaccine developed by Pfizer/BioNTech has been shown to be capable of developing an excellent antibody response against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein, with good production of neutralizing antibodies. Herein, we analyzed differences in the antibody response elicited by inoculation of the Pfizer/BioNTech vaccine through a peptide-based enzyme-linked immunosorbent assay (ELISA) that utilizes synthetic peptides derived from the spike protein in the immuno-adsorbent phase. Immunoreactivity against synthetic peptides was measured at different time points from vaccination and was also correlated with the SARS-CoV-2 neutralizing capacity. Our results indicate that all vaccinated subjects except one show reactive antibodies to at least one peptide at both 30 and 60 days after injection of the first dose. Only one of the 19 analyzed subjects showed no antibody response toward any of the selected peptides, consistently with a lower neutralizing capacity. More importantly, our data showed that the antibody response elicited by inoculation of the two doses of the Pfizer vaccine appears to be qualitatively individual, both in the type of recognized peptides and in the temporal persistence of the antibody response. Together with previous published data, our findings suggest that for effective pandemic control, it is important to constantly monitor the antibody protection in the population, and the assay described here could be a valid tool for this purpose.

Optimal monitoring of the ocean surface by observing the transport crossroads

<p>In the context of tracer transport in the ocean, we introduce a quantity, the crossroadness [1], which allows identifying the optimal disposition of a set of locations in order to monitor a given ocean surface region. The optimization is performed so that these sites observe the largest amount of water coming from the region and, at the same time, monitor waters coming from separate parts of the ocean. These are key criteria when deploying a marine observing network. Considering surface circulation, crossroadness measures at any location the extent of the ocean surface which transits in its neighborhood in a given time window. When the analysis is performed backward in time, this method allows us to identify the major sources which feed a target region. The method is first applied to a minimalistic model of a mesoscale eddy field, and then to realistic satellite-derived ocean currents in the Kerguelen area. In this region, we identify the optimal location of fixed stations capable of intercepting the trajectories of 43 surface drifters. We then illustrate the temporal persistence of the stations determined in this way. Finally, we identify possible hotspots of micro-nutrient enrichment for the recurrent spring phytoplanktonic bloom occurring there. Promising applications to other fields, such as larval connectivity or contaminant detection are discussed.</p><p>[1] A. Baudena, E. Ser-Giacomi, C. López, E. Hernández-García, F. d’Ovidio, Crossroads of the mesoscale circulation, Journal of Marine Systems 192, 1-14 (2019).</p>

Propaganda and Protest in Autocracies

Does propaganda reduce the rate of popular protest in autocracies? To answer this question, we draw on an original dataset of state-run newspapers from thirty countries, encompassing six languages and over four million articles. We find that propaganda diminishes the rate of protest, and that its effects persist over time. By increasing the level of pro-regime propaganda by one standard deviation, autocrats have reduced the odds of protest the following day by 15%. The half-life of this effect is between five and ten days, and very little of the initial effect persists after one month. This temporal persistence is remarkably consistent with campaign advertisements in democracies.

“It’s Raining Bits”: Patterns in Directional Precipitation Persistence across the United States

The spatial and temporal ordering of precipitation occurrence impacts ecosystems, streamflow, and water availability. For example, both large-scale climate patterns and local landscapes drive weather events, and the typical speeds and directions of these events moving across a basin dictate the timing of flows at its outlet. We address the predictability of precipitation occurrence at a given location, based on the knowledge of past precipitation at surrounding locations. We identify “dominant directions of precipitation influence” across the continental United States based on a gridded daily dataset. Specifically, we apply information theory–based measures that characterize dominant directions and strengths of spatial and temporal precipitation dependencies. On a national average, this dominant direction agrees with the prevalent direction of weather movement from west to east across the country, but regional differences reflect topographic divides, precipitation gradients, and different climatic drivers of precipitation. Trends in these information relationships and their correlations with climate indices over the past 70 years also show seasonal and spatial divides. This study expands upon a framework of information-based predictability to answer questions about spatial connectivity in addition to temporal persistence. The methods presented here are generally useful to understand many aspects of weather and climate variability.

Temporal Persistence of Bromadiolone in Decomposing Bodies of Common Kestrel (Falco tinnunculus)

Bromadiolone is a second generation anticoagulant rodenticide (SGAR) used to control pest rodents worldwide. SGARs are frequently involved in secondary poisoning in rodent predators due to their persistence and toxicity. This study aims to evaluate the persistence of bromadiolone in liver at different stages of carcass decomposition in experimentally-dosed common kestrels (Falco tinnunculus) to understand the possibility of detecting bromadiolone in cases of wildlife poisoning and the potential risk of tertiary poisoning. Twelve individuals were divided into the bromadiolone-dose group (dosed with 55 mg/kg b.w) and the control group. Hepatic bromadiolone concentrations found in each stage of decomposition were: 3000, 2891, 4804, 4245, 8848, and 756 ng/g dry weight at 1–2 h (fresh carcass), 24 h (moderate decomposition), 72 h, 96 h (advanced decomposition), seven days (very advanced decomposition), and 15 days (initial skeletal reduction) after death, respectively. Liver bromadiolone concentrations in carcasses remained relatively stable over the first four days and raised on day 7 of decomposition under the specific conditions of this experiment, presenting a risk of causing tertiary poisoning. However, at the initial skeletal reduction stage, liver bromadiolone concentration declined, which should be considered to interpret toxicological analyses and for proper diagnosis. This experimental study provides for the first time some light to better understand the degradation of SGARs in carcasses in the wild.