Microbial population dynamics and evolutionary outcomes under extreme energy limitation

Microorganisms commonly inhabit energy-limited ecosystems where cellular maintenance and reproduction is highly constrained. To gain insight into how individuals persist under such conditions, we derived demographic parameters from a collection of 21 heterotrophic bacterial taxa by censusing 100 populations in an effectively closed system for 1,000 d. All but one taxon survived prolonged resource scarcity, yielding estimated times to extinction ranging over four orders of magnitude from 100 to 105 y. Our findings corroborate reports of long-lived bacteria recovered from ancient environmental samples, while providing insight into mechanisms of persistence. As death rates declined over time, lifespan was extended through the scavenging of dead cells. Although reproduction was suppressed in the absence of exogenous resources, populations continued to evolve. Hundreds of mutations were acquired, contributing to genome-wide signatures of purifying selection as well as molecular signals of adaptation. Consistent ecological and evolutionary dynamics indicate that distantly related bacteria respond to energy limitation in a similar and predictable manner, which likely contributes to the stability and robustness of microbial life.

Neural and computational mechanisms of momentary fatigue and persistence in effort-based choice

From a gym workout, to deciding whether to persevere at work, many activities require us to persist in deciding that rewards are ‘worth the effort’ even as we become fatigued. However, studies examining effort-based decisions typically assume that the willingness to work is static. Here, we use computational modelling on two effort-based tasks, one behavioural and one during fMRI. We show that two hidden states of fatigue fluctuate on a moment-to-moment basis on different timescales but both reduce the willingness to exert effort for reward. The value of one state increases after effort but is ‘recoverable’ by rests, whereas a second ‘unrecoverable’ state gradually increases with work. The BOLD response in separate medial and lateral frontal sub-regions covaried with these states when making effort-based decisions, while a distinct fronto-striatal system integrated fatigue with value. These results provide a computational framework for understanding the brain mechanisms of persistence and momentary fatigue.

Epidemiological and clinical trends of sexually transmitted infections. Literature review

This article presents modern data on epidemiological trends, pathogenesis, and mechanisms of persistence and acquisition of antibiotic resistance of the most common sexually transmitted infections (STIs): chlamydial infection, gonorrhea, trichomoniasis. Data on the frequency of chlamydial infection, gonorrhea, trichomoniasis detection in the DILA medical laboratory in the period from 2018–2020 are also presented.Analysis of epidemiological and microbiological studies indicates a significant increase in the STIs incidence in countries with high economic development and the need for constant revision of diagnostic and treatment approaches, based on new data on the pathogens physiology, mechanisms and levels of antibiotic resistance, possibilities of laboratory diagnostics. Analysis of the DILA data on the chlamydial infection, gonorrhea, trichomoniasis detection is coinciding with the world trends in the increase of their prevalence. At the same time, the analysis of the DILA data demonstrated an interesting clinical phenomenon as a presence of 2 STIs peaks in women: the first at 21–25 years and the second at 51–55 years old.Clinical manifestations of STIs are increasingly losing their typical features today. This indicates the need for a laboratory search for all common STIs in the region. Knowledge of the etiological factor of the inflammatory process allows choosing the correct antibiotic therapy and preventing the further development of antibiotic resistance. This article presents data on the various methods of STIs laboratory tests. Regular visits of women for cervical cancer screening are a good opportunity to screen for STIs. The ability to detect STIs in biomaterial in liquid cytology makes this option more accessible.Thus, since vaccines against common bacterial and protozoa STIs pathogens have not yet been developed, the promotion of hygiene of sexual behavior and timely detection of infected persons during examination or screening with subsequent etiopathogenetic treatment are the basis of the STIs control systems and their consequences prevention.

Gene expression in tonsils in swine following infection with porcine reproductive and respiratory syndrome virus

Background Porcine reproductive and respiratory syndrome (PRRS) is a threat to pig production worldwide. Our objective was to understand mechanisms of persistence of PRRS virus (PRRSV) in tonsil. Transcriptome data from tonsil samples collected at 42 days post infection (dpi) were generated by RNA-seq and NanoString on 51 pigs that were selected to contrast the two PRRSV isolates used, NVSL and KS06, high and low tonsil viral level at 42 dpi, and the favorable and unfavorable genotypes at a genetic marker (WUR) for the putative PRRSV resistance gene GBP5. Results The number of differentially expressed genes (DEGs) differed markedly between models with and without accounting for cell-type enrichments (CE) in the samples that were predicted from the RNA-seq data. This indicates that differences in cell composition in tissues that consist of multiple cell types, such as tonsil, can have a large impact on observed differences in gene expression. Based on both the NanoString and the RNA-seq data, KS06-infected pigs showed greater activation, or less inhibition, of immune response in tonsils at 42 dpi than NVSL-infected pigs, with and without accounting for CE. This suggests that the NVSL virus may be better than the KS06 virus at evading host immune response and persists in tonsils by weakening, or preventing, host immune responses. Pigs with high viral levels showed larger CE of immune cells than low viral level pigs, potentially to trigger stronger immune responses. Presence of high tonsil virus was associated with a stronger immune response, especially innate immune response through interferon signaling, but these differences were not significant when accounting for CE. Genotype at WUR was associated with different effects on immune response in tonsils of pigs during the persistence stage, depending on viral isolate and tonsil viral level. Conclusions Results of this study provide insights into the effects of PRRSV isolate, tonsil viral level, and WUR genotype on host immune response and into potential mechanisms of PRRSV persistence in tonsils that could be targeted to improve strategies to reduce viral rebreaks. Finally, to understand transcriptome responses in tissues that consist of multiple cell types, it is important to consider differences in cell composition.

The long-term effects of war exposure on civic engagement

What are the legacies of war exposure on civic engagement? Recent evidence suggests that domestic war may have short-term effects on participation in social organizations. Yet, it is unclear whether these effects will be present in internationalized conflicts and persist over long periods of time. Further, the pathways of persistence by which war exposure leads to greater civic engagement in the long term are even less understood. In this paper, I contribute to both questions using unique evidence from the Vietnam War. Empirically, I combine a unique US military dataset containing bombing intensity with respondents’ wartime place of residence to generate an objective indicator of conflict intensity. Then, I exploit the distance to the arbitrarily drawn border at the 17th parallel as an instrument for conflict intensity. The results show that individuals who lived in a province heavily affected by the conflict during the war tend to be more engaged in social organizations and hold greater expressive values, at least 26 y later. Further, I empirically explore the mechanisms of persistence. The empirical evidence suggests that both persistence within individuals and community-wide transmission jointly account for the long-term increase of civic engagement after conflict.

Microbial population dynamics and evolutionary outcomes under extreme energy-limitation

As the most abundant and diverse form of life on Earth, microorganisms commonly inhabit energy-limited environments where cellular maintenance and growth is highly constrained. To gain insight into how microorganisms persist under such conditions, we derived demographic parameters from a diverse collection of bacteria by censusing 100 populations in a closed system for 1,000 days. All but one taxon survived prolonged resource scarcity, yielding estimated times-to-extinction ranging over four orders of magnitude from 100 – 105 years. These findings corroborate reports of long-lived bacteria that have been recovered from ancient environmental samples, while providing insight into mechanisms of persistence. Critically, we found that as death rates declined over time, lifespan was extended through the scavenging of dead cells. Although growth and reproduction were dramatically suppressed in the absence of an exogenous resource supply, bacterial populations continued to evolve. Hundreds of mutations were acquired, contributing to genome-wide signatures of negative selection as well as molecular signals of adaptation. Remarkable consistency in the ecological and evolutionary dynamics indicate that distantly related bacteria respond to energy-limitation in a similar and predictable manner, which likely contributes to the stability and robustness of microbial life.

EttA is likely non-essential in Staphylococcus aureus persistence, fitness or resistance to antibiotics

Background Tolerance to antibiotics and persistence are associated with antibiotic treatment failures, chronic-relapsing infections, and emerging antibiotic resistance in various bacteria, including Staphylococcus aureus. Mechanisms of persistence are largely unknown, yet have been linked to physiology under low-ATP conditions and the metabolic-inactive state. EttA is an ATP-binding cassette protein, linked in Eschrechia coli to ribosomal hibernation and fitness in stationary growth phase, yet its role in S. aureus physiology is unknown. Results Using whole genome sequencing (WGS) of serial clinical isolates, we identified an EttA-negative S. aureus mutant (ettAstop), and its isogenic wild-type counterpart. We used these two isogenic clones to investigate the role of ettA in S. aureus physiology in starvation and antibiotic stress, and test its role in persistence and antibiotic tolerance. ettAstop and its WT counterpart were similar in their antibiotic resistance profiles to multiple antibiotics. Population dynamics of ettAstop and the WT were similar in low-nutrient setting, with similar recovery from stationary growth phase or starvation. Supra-bacteriocidal concentration of cefazolin had the same killing effect on ettAstop and WT populations, with no difference in persister formation. Conclusions Lack of ettA does not affect S. aureus antibiotic resistance, beta-lactam tolerance, resilience to starvation or fitness following starvation. We conclude the role of ettA in S. aureus physiology is limited or redundant with another, unidentified gene. WGS of serial clinical isolates may enable investigation of other single genes involved in S. aureus virulence, and specifically persister cell formation.

Floristic similarity between adult and saplings strata of Caatinga hyperxerophilous woody vegetation – a Brazilian seasonally tropical dry forest

In the Caatinga, the maintenance of forest ecosystems depends on natural regeneration and several factors that can act in two ways: 1) provide the perpetuation of communities composheed of few species that dominate the adult and saplings strata, resulting in floristic similarities; 2) provide local differentiation between adult and saplings strata. However, these relationships remain poorly understood, as it is not known whether the factors acting on a local scale favor the floristic similarity between the adult and saplings strata or if these patterns are found in conserved and anthropized areas. This work evaluated the floristic similarity between the adult and saplings strata of hyperxerophilous caatinga woody-shrubby vegetation in conserved and anthropized areas. In two areasof conserved and anthropized hyperxerophilous Caatinga, adult and saplings individuals were measured and floristic richness and qualitative floristic similarity were evaluated. The floristic similarity between the adult and saplings strata was statistically compared using the Chao-Sørensen index. In both sites, although there was a large number of species exclusive to the adult stratum, the Chao-Sørensen index indicates high floristic similarity between strata. The analysis of this behavior together with the assessment of community structure shows that few species can be responsible for the key processes that structure and control the main mechanisms of persistence of these ecosystems. This can be attributed to the existence of locally uniform conditions that can define the dominance of adapted species groups.