Long-term experimental evolution decouples size and production costs in Escherichia coli.

Body size covaries with population dynamics across life's domains. Metabolism may impose fundamental constraints on the coevolution of size and demography, but experimental tests of the causal links remain elusive. We leverage a 60,000-generation experiment in which Escherichia coli populations evolved larger cells to examine intraspecific metabolic scaling and correlations with demographic parameters. Over the course of their evolution, the cells have roughly doubled in size relative to their ancestors. These larger cells have metabolic rates that are absolutely higher, but relative to their size, they are lower. Metabolic theory successfully predicted the relations between size, metabolism, and maximum population density, including support for Damuth's law of energy equivalence, such that populations of larger cells achieved lower maximum densities but higher maximum biomasses than populations of smaller cells. The scaling of metabolism with cell size thus predicted the scaling of size with maximum population density. In stark contrast to standard theory, however, populations of larger cells grew faster than those of smaller cells, contradicting the fundamental and intuitive assumption that the costs of building new individuals should scale directly with their size. The finding that the costs of production can be decoupled from size necessitates a reevaluation of the evolutionary drivers and ecological consequences of biological size more generally.

Elevated co2 has Differential Effects on Five Species of Microalgae from a Subtropical Freshwater Lake: Possible Implications for Phytoplankton Species Composition.

Rising atmospheric CO2 concentrations are predicted to have a significant impact on global phytoplankton populations. Of particular interest in freshwater systems are those species that produce toxins or impact water quality, though evidence for how these species, and many others, will respond is limited. This study investigated the effects of elevated CO2 (1,000 ppm) relative to current atmospheric CO2 partial pressures (400 ppm), on growth, cell size, carbon acquisition, and photophysiology of five freshwater phytoplankton species including a toxic cyanophyte, Raphidiopsis raciborskii, from Lake Wivenhoe, Australia. Effects of elevated CO2 on growth rate varied between species; notably growth rate was considerably higher for Staurastrum sp. and significantly lower for Stichococcus sp. with a trend to lower growth rate for R. raciborskii. Surface area to volume ratio was significantly lower with elevated CO2 , for all species except Cyclotella sp. Timing of maximum cell concentrations of those genera studied in monoculture occurred in the lake in order of CO2 affinity when free CO2 concentrations dropped below air equilibrium. The results presented here suggest that as atmospheric levels of CO2 rise, R. raciborskii may become less of a problem to water quality, while some species of chlorophytes may become more dominant. This has implications for stakeholders of many freshwater systems.

The mental health status of asylum seekers in middle- to high-income countries: a synthesis of current global evidence.

INTRODUCTION: The last 5 years have witnessed a significant increase in the number of people fleeing their countries of origin and seeking refuge in host countries. By the end of 2018, there were 3.5 million asylum seekers awaiting outcomes on their applications, the majority of whom were hosted by middle- to high-income countries. This review aimed to identify and synthesize current knowledge regarding the mental health status of asylum seekers in middle- to high-income countries. SOURCES OF DATA: A search was conducted across various databases for research literature published within the last 5 years (2014-2019). The final review and synthesis included 25 articles. AREAS OF AGREEMENT: Findings highlighted significant differences in the mental health status of asylum seekers compared to those with refugee status and permanent residence. AREAS OF CONTROVERSY: Guidelines from the World Health Organization and the United Nations High Commissioner for Refugees emphasize the need to understand and address mental health issues. Instead, there have been policy changes in many host countries regarding asylum applications, and the associated effects of these changes have been shown to negatively impact mental health. GROWING POINTS: The synthesized findings from the present review provide information regarding the current mental health status of asylum seekers hosted by middle- to high-income countries. Areas of intervention and resource allocation were also identified. AREAS TIMELY FOR DEVELOPING RESEARCH: Future research should consider the impact of large-scale, low-cost interventions to support the mental health of those seeking asylum.

Carbon acquisition characteristics of six microalgal species isolated from a subtropical reservoir: potential implications for species succession.

CO2 levels in freshwater systems can fluctuate widely, potentially influencing photosynthetic rates and growth of phytoplankton. Given the right conditions, this can lead to bloom formation and affect water quality. This study investigated the acquisition of dissolved inorganic carbon (DIC) by six species of microalgae, a cyanobacterium Cylindrospermopsis raciborskii, the diatoms Cyclotella sp., Nitzschia sp., and the green algae Stichococcus sp., Staurastrum sp., and Monoraphidium sp., all isolated from a subtropical reservoir in Australia. Carbon acquisition characteristics, specifically the affinity for DIC, internal pH, and internal DIC concentrations were measured. Affinities for CO2 ( K0.5(CO2) ) ranged between 0.7 and 6 µM CO2 . This was considerably lower than air-equilibrated surface water CO2 concentrations, and below reported affinities for CO2 of RuBisCO suggesting operation of active carbon dioxide concentrating mechanisms (CCMs) in all species. Internal pH was lowest for Cyclotella sp. at 7.19, and highest for Staurastrum sp., at 7.71. At 180 µM external DIC, ratios of internal:external CO2 ranged from 2.5 for Nitzschia sp. to 14 in C. raciborskii. Internal HCO3- concentration showed a linear relationship with surface area to biovolume ratio (SA:Vol). We hypothesized that species with a higher SA:Vol suffer more from diffusive escape of CO2 , thus storage of DIC as bicarbonate is favored in these strains. For C. raciborskii, under stratified summer conditions, its strong CCM, and resilient photosynthetic characteristics may contribute to its bloom forming capacity.

Atmospheric trace gases support primary production in Antarctic desert surface soil.

Cultivation-independent surveys have shown that the desert soils of Antarctica harbour surprisingly rich microbial communities. Given that phototroph abundance varies across these Antarctic soils, an enduring question is what supports life in those communities with low photosynthetic capacity. Here we provide evidence that atmospheric trace gases are the primary energy sources of two Antarctic surface soil communities. We reconstructed 23 draft genomes from metagenomic reads, including genomes from the candidate bacterial phyla WPS-2 and AD3. The dominant community members encoded and expressed high-affinity hydrogenases, carbon monoxide dehydrogenases, and a RuBisCO lineage known to support chemosynthetic carbon fixation. Soil microcosms aerobically scavenged atmospheric H2 and CO at rates sufficient to sustain their theoretical maintenance energy and mediated substantial levels of chemosynthetic but not photosynthetic CO2 fixation. We propose that atmospheric H2, CO2 and CO provide dependable sources of energy and carbon to support these communities, which suggests that atmospheric energy sources can provide an alternative basis for ecosystem function to solar or geological energy sources. Although more extensive sampling is required to verify whether this process is widespread in terrestrial Antarctica and other oligotrophic habitats, our results provide new understanding of the minimal nutritional requirements for life and open the possibility that atmospheric gases support life on other planets.

Effects of quercetin and EGCG on mitochondrial biogenesis and immunity.

PURPOSE: To test the influence of 1000 mg of quercetin (Q) with or without 120 mg of epigallocatechin 3-gallate (EGCG), 400 mg of isoquercetin, and 400 mg of eicosapentaenoic acid and docosahexaenoic acid (Q-EGCG) on exercise performance, muscle mitochondrial biogenesis, and changes in measures of immunity and inflammation before and after a 3-d period of heavy exertion. METHODS: Trained cyclists (N = 39) were randomized to placebo (P), Q, or Q-EGCG and ingested supplements in a double-blinded fashion for 2 wk before, during, and 1 wk after a 3-d period in which subjects cycled for 3 h x d(-1) at approximately 57% Wmax. Blood, saliva, and muscle biopsy samples were collected before and after 2 wk of supplementation and immediately after the exercise bout on the third day. Blood and saliva samples were also collected 14 h after exercise. RESULTS: Two-week supplementation resulted in a significant increase in plasma quercetin for Q and Q-EGCG and granulocyte oxidative burst activity (GOBA) in Q-EGCG. Immediately after the third exercise bout, significant decreases for C-reactive protein (CRP), and plasma interleukin 6 (IL-6) and interleukin 10 (IL-10) were measured in Q-EGCG compared with P. Granulocyte colony-stimulating factor and CRP were reduced in Q-EGCG 14 h after exercise. No group differences were measured in muscle messenger RNA expression for peroxisome proliferator-activated receptor gamma coactivator alpha, citrate synthase, or cytochrome c. CONCLUSIONS: Two-week supplementation with Q-EGCG was effective in augmenting GOBA andin countering inflammation after 3 d of heavy exertion in trained cyclists.

Suspected statin-induced respiratory muscle myopathy during long-term inspiratory muscle training in a patient with diaphragmatic paralysis.

BACKGROUND AND PURPOSE: Abnormal lipids are associated with the development of coronary heart disease; for this reason, lipid-lowering agents have become a standard of care. The purposes of this case report are: (1) to highlight the association of impaired inspiratory muscle performance (IMP) with statin therapy and (2) to describe potentially useful methods of examining and treating people with known or suspected statin-induced skeletal myopathies (SISMs). CASE DESCRIPTION: The patient had breathlessness on exertion and a restrictive lung disorder from a right hemidiaphragmatic paralysis, for which he was prescribed high-intensity inspiratory muscle training (IMT). He had a secondary diagnosis of hyperlipidemia, which was treated with 40 mg of simvastatin after 5(1/2) months of IMT. OUTCOMES: The improvements in IMP, symptoms, and functional status obtained from almost 6 months of high-intensity IMT were lost after the commencement of simvastatin. However, 3 weeks after termination of simvastatin combined with high-intensity IMT, the patient's IMP, symptoms, and functional status exceeded pre-statin levels. DISCUSSION: This case report suggests that high-intensity IMT can be used effectively in a patient with impaired diaphragmatic function and during recovery from a respiratory SISM. The marked reduction in IMP and inability to perform IMT resolved with the cessation of statin therapy. The case report also highlights the potential effects of SISMs in all skeletal muscle groups. The clinical implications of this case report include the potential role of physical therapy in monitoring and possibly facilitating the spontaneous recovery of an SISM, as well as the need to investigate the IMP of a person with dyspnea and fatigue who is taking a statin.