Bacterial symbionts can play a key role in the interactions between trophic levels. Certain symbionts are known to confer protection against natural enemies of their arthropod hosts. However, whether ...natural enemies evolve and adapt to prey symbionts is not well understood.
In this study, we found that a free‐living strain of aphid symbiont Serratia symbiotica, SsMj, was the most discriminative biomarker of the aphid feeding in the microbiota of aphidophagous (aphid‐feeding) ladybirds. Moreover, SsMj persisted in the digestive tract of starved ladybirds and did not decay together with ingested aphid materials, suggesting horizontal transmission across trophic levels.
We further found that SsMj did not necessarily exhibit a negative impact on aphidophagous ladybirds of the Coccinellini tribe in contrast with other, non‐aphidophagous, ladybirds. First, starvation did not significantly change SsMj relative abundance or alpha microbiota diversity of an aphidophagous ladybird. Second, diets containing SsMj did not decrease the performance of the aphidophagous ladybirds. Third, infection with SsMj through injection had a minor impact on the survival of aphidophagous ladybirds.
Together, our evidence suggests that the aphid symbiont S. symbiotica can be horizontally transmitted to ladybird predators. At the same time, the group of ladybirds that have adapted to feeding on aphids have also evolved to establish a nearly neutral relationship with S. symbiotica, suggesting adaptation to a prey symbiont.
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细菌共生菌可以在不同营养级间生物的相互作用中起关键作用。其中一些共生菌可以帮助它们的节肢动物宿主抵御天敌。但是，我们仍不清楚天敌是否进化去适应它们猎物的共生菌。
本研究，我们发现一株营自由生活的蚜虫共生菌Serratia symbiotica(命名为SsMj)，是瓢虫取食蚜虫后瓢虫微生物组中相对丰度上升程度最大的细菌。不仅如此，SsMj不会随蚜虫一起被瓢虫消化掉，而是留存在瓢虫的消化道，说明它发生跨营养级的传播。
我们进一步发现SsMj不一定对蚜食性的瓢虫有负面的影响。首先，饥饿不会显著影响蚜食性瓢虫体内的SsMj相对丰度和微生物组的alpha多样性。然后，蚜食性的瓢虫不会因为取食添加SsMj的食物而表现力下降。最后，通过注射感染SsMj较轻微地降低蚜食性瓢虫的存活率。相对而言，SsMj对其它瓢虫有显著的负面影响。
总的来说，我们的证据表明一种蚜虫的共生菌S. symbiotica可以水平传播至蚜虫的捕食者瓢虫。另一方面，瓢虫中一个偏好食蚜的支系则通过适应进化，与S. symbiotica建立了一种近乎中性的关系。
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A tightly coupled integrated navigation system (TCINS) for hypersonic vehicles is proposed when the satellite signals are disturbed. Firstly, the architecture of the integrated navigation system for ...the hypersonic vehicle is introduced. This system applies fiber SINS, BeiDou satellite receiver (BDS) and System On a Parogrammable Chip (SOPC) missile-born computer. Subsequently, the SINS mechanization for hypersonic vehicle is presented. The J2 model is employed for the normal gravity of the near space. An algorithm for updating the attitude, velocity and position is designed. State equations and measurement equations of SINS/BDS tightly coupled integrated navigation for hypersonic vehicle are given, and a scheme of validity for satellite data is designed. Finally, the SINS/BDS tightly coupled vehicle field tests and hardware-in-the-loop (HWIL) simulation tests are carried out. The vehicle field test and HWIL simulation results show that the heading angle error of tightly coupled integrated navigation is within 0.2°, the pitch and roll angle errors are within 0.05°, the maximum velocity error is 0.3 m/s, and the maximum position error is 10 m.
The COVID-19 pandemic disrupted health systems and economies throughout the world during 2020 and was particularly devastating for the United States, which experienced the highest numbers of reported ...cases and deaths during 2020
. Many of the epidemiological features responsible for observed rates of morbidity and mortality have been reported
; however, the overall burden and characteristics of COVID-19 in the United States have not been comprehensively quantified. Here we use a data-driven model-inference approach to simulate the pandemic at county-scale in the United States during 2020 and estimate critical, time-varying epidemiological properties underpinning the dynamics of the virus. The pandemic in the United States during 2020 was characterized by national ascertainment rates that increased from 11.3% (95% credible interval (CI): 8.3-15.9%) in March to 24.5% (18.6-32.3%) during December. Population susceptibility at the end of the year was 69.0% (63.6-75.4%), indicating that about one third of the US population had been infected. Community infectious rates, the percentage of people harbouring a contagious infection, increased above 0.8% (0.6-1.0%) before the end of the year, and were as high as 2.4% in some major metropolitan areas. By contrast, the infection fatality rate fell to 0.3% by year's end.
Hepatitis D virus (HDV) is a defective virus that completes its life cycle only with hepatitis B virus (HBV). The HBV with HDV super-infection has been considered as one of the most severe forms of ...the chronic viral hepatitis. However, there is a scarcity of data on the global burden of HDV infection.
We searched PubMed, Embase, Cochrane Library and China Knowledge Resource Integrated databases from 1 January 1977 to 31 December 2016. We included studies with a minimum sample size of 50 patients. Our study analysed data from a total of 40 million individuals to estimate the prevalence of HDV by using Der-Simonian Laird random-effects model. The data were further categorised according to risk factors.
From a total of 2717 initially identified studies, only 182 articles from 61 countries and regions met the final inclusion criteria. The overall prevalence of HDV was 0.98% (95% CI 0.61 to 1.42). In HBsAg-positive population, HDV pooled prevalence was 14.57% (95% CI 12.93 to 16.27): Seroprevalence was 10.58% (95% CI 9.14 to 12.11) in mixed population without risk factors of intravenous drug use (IVDU) and high-risk sexual behaviour (HRSB). It was 37.57% (95% CI 29.30 to 46.20) in the IVDU population and 17.01% (95% CI 10.69 to 24.34) in HRSB population.
We found that approximately 10.58% HBsAg carriers (without IVDU and HRSB) were coinfected with HDV, which is twofold of what has been estimated before. We also noted a substantially higher HDV prevalence in the IVDU and HRSB population. Our study highlights the need for increased focus on the routine HDV screening and rigorous implementation of HBV vaccine programme.
For influenza forecasts generated using dynamical models, forecast inaccuracy is partly attributable to the nonlinear growth of error. As a consequence, quantification of the nonlinear error ...structure in current forecast models is needed so that this growth can be corrected and forecast skill improved. Here, we inspect the error growth of a compartmental influenza model and find that a robust error structure arises naturally from the nonlinear model dynamics. By counteracting these structural errors, diagnosed using error breeding, we develop a new forecast approach that combines dynamical error correction and statistical filtering techniques. In retrospective forecasts of historical influenza outbreaks for 95 US cities from 2003 to 2014, overall forecast accuracy for outbreak peak timing, peak intensity and attack rate, are substantially improved for predicted lead times up to 10 weeks. This error growth correction method can be generalized to improve the forecast accuracy of other infectious disease dynamical models.Inaccuracy of influenza forecasts based on dynamical models is partly due to nonlinear error growth. Here the authors address the error structure of a compartmental influenza model, and develop a new improved forecast approach combining dynamical error correction and statistical filtering techniques.
Abstract
Background
Nonpharmaceutical interventions (NPIs) have been implemented to suppress transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Evidence indicates that NPIs ...against coronavirus disease 2019 (COVID-19) may also have effects on transmission of seasonal influenza.
Methods
In this study, we use an absolute humidity-driven susceptible-infectious-recovered-susceptible (SIRS) model to quantify the reduction of influenza incidence and transmission in the United States and US Department of Health and Human Services regions after implementation of NPIs in 2020. We investigate long-term effect of NPIs on influenza incidence by projecting influenza transmission at the national scale over the next 5 years, using the SIRS model.
Results
We estimate that incidence of influenza A/H1 and B, which circulated in early 2020, was reduced by more than 60% in the United States during the first 10 weeks following implementation of NPIs. The reduction of influenza transmission exhibits clear geographical variation. After the control measures are relaxed, potential accumulation of susceptibility to influenza infection may lead to a large outbreak, the scale of which may be affected by length of the intervention period and duration of immunity to influenza.
Conclusions
Healthcare systems need to prepare for potential influenza patient surges and advocate vaccination and continued precautions.
Incidence of influenza A/H1 and B were reduced by more than 60% in the United States during the first 10 weeks following implementation of NPIs. Potential large outbreaks of influenza may occur after the relaxation of NPIs.
Improved understanding of the effects of meteorological conditions on the transmission of SARS-CoV-2, the causative agent for COVID-19 disease, is needed. Here, we estimate the relationship between ...air temperature, specific humidity, and ultraviolet radiation and SARS-CoV-2 transmission in 2669 U.S. counties with abundant reported cases from March 15 to December 31, 2020. Specifically, we quantify the associations of daily mean temperature, specific humidity, and ultraviolet radiation with daily estimates of the SARS-CoV-2 reproduction number (R
) and calculate the fraction of R
attributable to these meteorological conditions. Lower air temperature (within the 20-40 °C range), lower specific humidity, and lower ultraviolet radiation were significantly associated with increased R
. The fraction of R
attributable to temperature, specific humidity, and ultraviolet radiation were 3.73% (95% empirical confidence interval eCI: 3.66-3.76%), 9.35% (95% eCI: 9.27-9.39%), and 4.44% (95% eCI: 4.38-4.47%), respectively. In total, 17.5% of R
was attributable to meteorological factors. The fractions attributable to meteorological factors generally were higher in northern counties than in southern counties. Our findings indicate that cold and dry weather and low levels of ultraviolet radiation are moderately associated with increased SARS-CoV-2 transmissibility, with humidity playing the largest role.
Transition metal-catalyzed organic electrochemistry is a rapidly growing research area owing in part to the ability of metal catalysts to alter the selectivity of a given transformation. This ...conversion mainly focuses on transition metal-catalyzed anodic oxidation and cathodic reduction and great progress has been achieved in both areas. Typically, only one of the half-cell reactions is involved in the organic reaction while a sacrificial reaction occurs at the counter electrode, which is inherently wasteful since one electrode is not being used productively. Recently, transition metal-catalyzed paired electrolysis that makes use of both anodic oxidation and cathodic reduction has attracted much attention. This perspective highlights the recent progress of each type of electrochemical reaction and relatively focuses on the transition metal-catalyzed paired electrolysis, showcasing that electrochemical reactions involving transition metal catalysis have advantages over conventional reactions in terms of controlling the reaction activity and selectivity and figuring out that transition metal-catalyzed paired electrolysis is an important direction of organic electrochemistry in the future and offers numerous opportunities for new and improved organic reaction methods.
Transition metal-catalyzed organic electrochemistry is a rapidly growing research area owing in part to the ability of metal catalysts to alter the selectivity of a given transformation.
Estimation of the prevalence and contagiousness of undocumented novel coronavirus severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infections is critical for understanding the overall ...prevalence and pandemic potential of this disease. Here, we use observations of reported infection within China, in conjunction with mobility data, a networked dynamic metapopulation model, and Bayesian inference, to infer critical epidemiological characteristics associated with SARS-CoV-2, including the fraction of undocumented infections and their contagiousness. We estimate that 86% of all infections were undocumented 95% credible interval (CI): 82-90% before the 23 January 2020 travel restrictions. The transmission rate of undocumented infections per person was 55% the transmission rate of documented infections (95% CI: 46-62%), yet, because of their greater numbers, undocumented infections were the source of 79% of the documented cases. These findings explain the rapid geographic spread of SARS-CoV-2 and indicate that containment of this virus will be particularly challenging.
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