How FtsEX localizes to the Z ring and interacts with FtsA to regulate cell division

In Escherichia coli, FtsEX, a member of the ABC transporter superfamily, is involved in regulating the assembly and activation of the divisome to couple cell wall synthesis to cell wall hydrolysis at the septum. Genetic studies indicate FtsEX acts on FtsA to begin the recruitment of the downstream division proteins but blocks septal PG synthesis until a signal is received that divisome assembly is complete. However, the details of how FtsEX localizes to the Z ring and how it interacts with FtsA are not clear. Our results show that recruitment of FtsE and FtsX is codependent and suggest that the FtsEX complex is recruited through FtsE interacting with the conserved tail of FtsZ (CCTP), thus adding FtsEX to a growing list of proteins that interacts with the CCTP of FtsZ. Furthermore, we find that the N‐terminus of FtsX is not required for FtsEX localization to the Z ring but is required for its functions in cell division indicating that it interacts with FtsA. Taken together, these results suggest that FtsEX first interacts with FtsZ to localize to the Z ring and then interacts with FtsA to promote divisome assembly and regulate septal PG synthesis.     

Phytoplankton size distribution and community structure: influence of nutrient input and sedimentary loss

This study examines the effects of nutrient availability andsedimentary loss on the dynamics of freshwater phytoplankton,from the physiological state at the cellular level to the competitionissue at the community level. We studied the separated and combinedresponses to nutrient inputs and mixing, of a phytoplanktoncommunity, in terms of size fractionated photosynthetic activityand biomass, exported biomass and species composition. The communitywas composed of two dominant species, which differed in theirsinking velocity. Experiments were conducted during 8 days in12 water columns of 50 L, in light and temperature controlledconditions. The nutrient input was found to be the predominantfactor affecting sedimentary fluxes and community composition,but mixing had also a significant effect on the community structureand sedimentary fluxes when combined with nutrient inputs. Inthis latter case, the large sinking species, Tribonema sp. (Xanthophyceae),developed, due to both a decrease of sedimentary loss by upwardadvection and the enhanced growth from nutrient inputs, as indicatedby the higher photosynthetic activity measured using chlorophylla in vivo fluorescence. The combined effect of both factorsreduced the difference between growth and loss rates and increasedthe viability of the sinking populations.     

Methodology matters when estimating deer abundance: a global systematic review and recommendations for improvements

Deer (Cervidae) are key components of many ecosystems and estimating deer abundance or density is important to understanding these roles. Many field methods have been used to estimate deer abundance and density, but the factors determining where, when, and why a method was used, and its usefulness, have not been investigated. We systematically reviewed journal articles published during 2004–2018 to evaluate spatio-temporal trends in study objectives, methodologies, and deer abundance and density estimates, and determine how they varied with biophysical and anthropogenic attributes. We also reviewed the precision and bias of deer abundance estimation methods. We found 3,870 deer abundance and density estimates. Most estimates (58%) were for white-tailed deer (Odocoileus virginianus), red deer (Cervus elaphus), and roe deer (Capreolus capreolus). The 6 key methods used to estimate abundance and density were pedestrian sign (track or fecal) counts, pedestrian direct counts, vehicular direct counts, aerial direct counts, motion-sensitive cameras, and harvest data. There were regional differences in the use of these methods, but a general pattern was a temporal shift from using harvest data, pedestrian direct counts, and aerial direct counts to using pedestrian sign counts and motion-sensitive cameras. Only 32% of estimates were accompanied by a measure of precision. The most precise estimates were from vehicular spotlight counts and from capture–recapture analysis of images from motion-sensitive cameras. For aerial direct counts, capture–recapture methods provided the most precise estimates. Bias was robustly assessed in only 16 studies. Most abundance estimates were negatively biased, but capture–recapture methods were the least biased. The usefulness of deer abundance and density estimates would be substantially improved by 1) reporting key methodological details, 2) robustly assessing bias, 3) reporting the precision of estimates, 4) using methods that increase and estimate detection probability, and 5) staying up to date on new methods. The automation of image analysis using machine learning should increase the accuracy and precision of abundance estimates from direct aerial counts (visible and thermal infrared, including from unmanned aerial vehicles [drones]) and motion-sensitive cameras, and substantially reduce the time and cost burdens of manual image analysis.     

Light Response of Seedlings of a Central African Timber Tree Species,Lophira alata (Ochnaceae), and the Definition of Light Requirements

Light is of primary importance in structuring tropical tree communities. Light exposure at seedling and adult stages has been used to characterize the ecological profile of tropical trees, with many implications in forest management and restoration ecology. Most shade‐tolerance classification systems have been proposed based on empirical observations in a specific area and thus result in contradictions among categories assigned to a given species. In this study, we aimed to quantify the light requirements for seedling growth of a Central African timber tree, Lophira alata (Ochnaceae), taking into account effects of population origin. In two controlled experiments: a light response experiment and a comparative population experiment, conducted in southwestern Cameroon, using seeds collected from four populations (three from Cameroon and one from Gabon), we examined the quantitative responses to irradiance of seedlings. After 2 years, mortality was very low (<3%), even in extremely low irradiance. Growth and biomass allocation patterns varied in response to light, with intermediate irradiance (24–43%) providing optimal conditions. Light response differed between populations. The Boumba population in the northeastern edge of the species' distribution exhibited the highest light requirements, suggesting a local adaptation. As a result of positive growth at low irradiance and maximum growth at intermediate irradiance, we concluded that L. alata exhibits characteristics of both non‐pioneer and pioneer species. Implications of our results to propose an objective way to assign the light requirement for tropical tree species are discussed.     

Is the Relationship between Common Mental Disorder and Adiposity Bidirectional? Prospective Analyses of a UK General Population-Based Study

The direction of the association between mental health and adiposity is poorly understood. Our objective was to empirically examine this link in a UK study. This is a prospective cohort study of 3 388 people (men) aged ≥ 18 years at study induction who participated in both the UK Health and Lifestyle Survey at baseline (HALS-1, 1984/1985) and the re-survey (HALS-2, 1991/1992). At both survey examinations, body mass index, waist circumference and self-reported common mental disorder (the 30-item General Health Questionnaire, GHQ) were measured. Logistic regression models were used to compute odds ratios (OR) and accompanying 95% confidence intervals (CI) for the associations between (1) baseline common mental disorder (QHQ score > 4) and subsequent general and abdominal obesity and (2) baseline general and abdominal obesity and re-survey common mental disorders. After controlling for a range of covariates, participants with common mental disorder at baseline experienced greater odds of subsequently becoming overweight (women, OR: 1.30, 1.03 – 1.64; men, 1.05, 0.81 – 1.38) and obese (women, 1.26, 0.82 – 1.94; men, OR: 2.10, 1.23 – 3.55) than those who were free of common mental disorder. Similarly, having baseline common mental health disorder was also related to a greater risk of developing moderate (1.57, 1.21 – 2.04) and severe (1.48, 1.09 – 2.01) abdominal obesity (women only). Baseline general or abdominal obesity was not associated with the risk of future common mental disorder. These findings of the present study suggest that the direction of association between common mental disorders and adiposity is from common mental disorder to increased future risk of adiposity as opposed to the converse.     

Plasticity in Vegetative Growth over Contrasted Growing Sites of an F1 Olive Tree Progeny during Its Juvenile Phase

Climatic changes impact fruit tree growth and severely limit their production. Investigating the tree ability to cope with environmental variations is thus necessary to adapt breeding and management strategies in order to ensure sustainable production. In this study, we assessed the genetic parameters and genotype by environment interaction (GxE) during the early tree growth. One hundred and twenty olive seedlings derived from the cross ‘Olivière’ x ‘Arbequina’ were examined across two sites with contrasted environments, accounting for ontogenetic trends over three years. Models including the year of growth, branching order, environment, genotype effects, and their interactions were built with variance function and covariance structure of residuals when necessary. After selection of a model, broad sense heritabilities were estimated. Despite strong environmental effect on most traits, no GxE was found. Moreover, the internal structure of traits co-variation was similar in both sites. Ontogenetic growth variation, related to (i) the overall tree form and (ii) the growth and branching habit at growth unit scale, was not altered by the environment. Finally, a moderate to strong genetic control was identified for traits at the whole tree scale and at internode scale. Among all studied traits, the maximal internode length exhibited the highest heritability (H² = 0.74). Considering the determinant role of this trait in tree architecture and its stability across environments, this study consolidates its relevance for breeding.     

Dissemination of IncF-type plasmids in multiresistant CTX-M-15-producing Enterobacteriaceae isolates from surgical-site infections in Bangui,Central African Republic

Background

Surgical-site infection is the most frequent health care-associated infection in the developing world, with a strikingly higher prevalence than in developed countries We studied the prevalence of resistance to antibiotics in Enterobacteriaceae isolates from surgical-site infections collected in three major tertiary care centres in Bangui, Central African Republic. We also studied the genetic basis for antibiotic resistance and the genetic background of third-generation cephalosporin-resistant (3GC-R) Enterobacteriaceae.

Results

Between April 2011 and April 2012, 195 patients with nosocomial surgical-site infections were consecutively recruited into the study at five surgical departments in three major tertiary care centres. Of the 165 bacterial isolates collected, most were Enterobacteriaceae (102/165, 61.8%). Of these, 65/102 (63.7%) were 3GC-R, which were characterized for resistance gene determinants and genetic background. The bla_CTX-M-15 and aac(6′)-Ib-cr genes were detected in all strains, usually associated with qnr genes (98.5%). Escherichia coli, the most commonly recovered species (33/65, 50.8%), occurred in six different sequence types, including the pandemic B2-O25b-ST131 group (12/33, 36.4%). Resistance transfer was studied in one representative strain of the resistance gene content in each repetitive extragenic palindromic and enterobacterial repetitive intergenic consensus sequence-PCR banding pattern. Plasmids were characterized by PCR-based replicon typing and sub-typing schemes. In most isolates (18/27, 66.7%), bla_CTX-M-15 genes were found in incompatibility groups F/F31:A4:B1 and F/F36:A4:B1 conjugative plasmids. Horizontal transfer of both plasmids is probably an important mechanism for the spread of bla_CTX-M-15 among Enterobacteriaceae species and hospitals. The presence of sets of antibiotic resistance genes in these two plasmids indicates their capacity for gene rearrangement and their evolution into new variants.

Conclusions

Diverse modes are involved in transmission of resistance, plasmid dissemination probably playing a major role.     

Combined Effects of Time Spent in Physical Activity,Sedentary Behaviors and Sleep on Obesity and Cardio-Metabolic Health Markers: A Novel Compositional Data Analysis Approach

The associations between time spent in sleep, sedentary behaviors (SB) and physical activity with health are usually studied without taking into account that time is finite during the day, so time spent in each of these behaviors are codependent. Therefore, little is known about the combined effect of time spent in sleep, SB and physical activity, that together constitute a composite whole, on obesity and cardio-metabolic health markers. Cross-sectional analysis of NHANES 2005–6 cycle on N = 1937 adults, was undertaken using a compositional analysis paradigm, which accounts for this intrinsic codependence. Time spent in SB, light intensity (LIPA) and moderate to vigorous activity (MVPA) was determined from accelerometry and combined with self-reported sleep time to obtain the 24 hour time budget composition. The distribution of time spent in sleep, SB, LIPA and MVPA is significantly associated with BMI, waist circumference, triglycerides, plasma glucose, plasma insulin (all p<0.001), and systolic (p<0.001) and diastolic blood pressure (p<0.003), but not HDL or LDL. Within the composition, the strongest positive effect is found for the proportion of time spent in MVPA. Strikingly, the effects of MVPA replacing another behavior and of MVPA being displaced by another behavior are asymmetric. For example, re-allocating 10 minutes of SB to MVPA was associated with a lower waist circumference by 0.001% but if 10 minutes of MVPA is displaced by SB this was associated with a 0.84% higher waist circumference. The proportion of time spent in LIPA and SB were detrimentally associated with obesity and cardiovascular disease markers, but the association with SB was stronger. For diabetes risk markers, replacing SB with LIPA was associated with more favorable outcomes. Time spent in MVPA is an important target for intervention and preventing transfer of time from LIPA to SB might lessen the negative effects of physical inactivity.     

Anthrax toxin evades Toll-like receptor recognition, whereas its cell wall components trigger activation via TLR2/6 heterodimers

Bacillus anthracis is a Gram-positive bacillus that is the causative agent of anthrax. The virulence of the bacillus is partly due to the production of a tripartite virulence factor: protective antigen (PA), lethal factor (LF) and edema factor (EF). Recognition of the bacillus and its toxins by the innate immune system is likely to play a key role following infection. In this study we set out to investigate whether anthrax cell wall (ACW) components as well as the lethal toxin are sensed by Toll-like receptors (TLRs). Our data suggest that ACW components as well as PA are sensed by TLR2/6 heterodimers triggering an inflammatory response. This recognition takes place on the cell surface within specialized microdomains for ACW, whereas PA seems to trigger responses intracellularly. Interestingly, LF does not trigger a pro-inflammatory response, and when combined with PA, the complex is not sensed by the innate immune system. Overall our data suggest that TLR2/6 heterodimers are responsible for sensing the ACW and PA, whereas the formation of the subsequent toxin (LF + PA) seems to evade detection by the innate immune system contributing to the virulence of the toxin.