Nitrogen Forms Influence Microcystin Concentration and Composition via Changes in Cyanobacterial Community Structure

The eutrophication of freshwaters is a global health concern as lakes with excess nutrients are often subject to toxic cyanobacterial blooms. Although phosphorus is considered the main element regulating cyanobacterial biomass, nitrogen (N) concentration and more specifically the availability of different N forms may influence the overall toxicity of blooms. In this study of three eutrophic lakes prone to cyanobacterial blooms, we examined the effects of nitrogen species and concentrations and other environmental factors in influencing cyanobacterial community structure, microcystin (MC) concentrations and MC congener composition. The identification of specific MC congeners was of particular interest as they vary widely in toxicity. Different nitrogen forms appeared to influence cyanobacterial community structure leading to corresponding effects on MC concentrations and composition. Total MC concentrations across the lakes were largely explained by a combination of abiotic factors: dissolved organic nitrogen, water temperature and ammonium, but Microcystis spp. biomass was overall the best predictor of MC concentrations. Environmental factors did not appear to affect MC congener composition directly but there were significant associations between specific MC congeners and particular species. Based on redundancy analyses (RDA), the relative biomass of Microcystis aeruginosa was associated with MC-RR, M. wesenbergii with MC-LA and Aphanizomenon flos-aquae with MC-YR. The latter two species are not generally considered capable of MC production. Total nitrogen, water temperature, ammonium and dissolved organic nitrogen influenced the cyanobacterial community structure, which in turn resulted in differences in the dominant MC congener and the overall toxicity.     

Risky Drinking Patterns Are Being Continued into Pregnancy: A Prospective Cohort Study

Background

Risky patterns of alcohol use prior to pregnancy increase the risk of alcohol-exposed pregnancies and subsequent adverse outcomes. It is important to understand how consumption changes once women become pregnant.

Objective

The aim of this study was to describe the characteristics of women that partake in risky drinking patterns before pregnancy and to examine how these patterns change once they become pregnant.

Methods

A sample of 1577 women from the 1973–78 cohort of the Australian Longitudinal Study on Women’s Health were included if they first reported being pregnant in 2000, 2003, 2006, 2009 and reported risky drinking patterns prior to that pregnancy. Multinomial logistic regression was used to determine which risky drinking patterns were most likely to continue into pregnancy.

Results

When reporting risky drinking patterns prior to pregnancy only 6% of women reported weekly drinking only, whereas 46% reported binge drinking only and 48% reported both. Women in both binge categories were more likely to have experienced financial stress, not been partnered, smoked, used drugs, been nulliparous, experienced a violent relationship, and were less educated. Most women (46%) continued these risky drinking patterns into pregnancy, with 40% reducing these behaviors, and 14% completely ceasing alcohol consumption. Once pregnant, women who binged only prior to pregnancy were more likely to continue (55%) rather than reduce drinking (29%). Of the combined drinking group 61% continued to binge and 47% continued weekly drinking. Compared with the combined drinking group, binge only drinkers prior to pregnancy were less likely to reduce rather than continue their drinking once pregnant (OR = 0.37, 95% CI  =  0.29, 0.47).

Conclusions

Over a third of women continued risky drinking into pregnancy, especially binge drinking, suggesting a need to address alcohol consumption prior to pregnancy.     

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

A “sheath” fluid passing through a microfluidic channel at low Reynolds number can be directed around another “core” stream and used to dictate the shape as well as the diameter of a core stream. Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid. By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed. Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid. Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers. Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light. Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components.     

Marked Microevolution of a Unique Mycobacterium tuberculosis Strain in 17 Years of Ongoing Transmission in a High Risk Population

The transmission and persistence of Mycobacterium tuberculosis within high risk populations is a threat to tuberculosis (TB) control. In the current study, we used whole genome sequencing (WGS) to decipher the transmission dynamics and microevolution of M. tuberculosis ON-A, an endemic strain responsible for an ongoing outbreak of TB in an urban homeless/under-housed population. Sixty-one M. tuberculosis isolates representing 57 TB cases from 1997 to 2013 were subjected to WGS. Sequencing data was integrated with available epidemiological information and analyzed to determine how the M. tuberculosis ON-A strain has evolved during almost two decades of active transmission. WGS offers higher discriminatory power than traditional genotyping techniques, dividing the M. tuberculosis ON-A strain into 6 sub-clusters, each defined by unique single nucleotide polymorphism profiles. One sub-cluster, designated ON-A^NM (Natural Mutant; 26 isolates from 24 cases) was also defined by a large, 15 kb genomic deletion. WGS analysis reveals the existence of multiple transmission chains within the same population/setting. Our results help validate the utility of WGS as a powerful tool for identifying genomic changes and adaptation of M. tuberculosis.     

A resource of vectors and ES cells for targeted deletion of microRNAs in mice

The 21-23 nucleotide, single-stranded RNAs classified as microRNAs (miRNA) perform fundamental roles in diverse cellular and developmental processes. In contrast to the situation for protein-coding genes, no public resource of miRNA mouse mutant alleles exists. Here we describe a collection of 428 miRNA targeting vectors covering 476 of the miRNA genes annotated in the miRBase registry. Using these vectors, we generated a library of highly germline-transmissible C57BL/6N mouse embryonic stem (ES) cell clones harboring targeted deletions for 392 miRNA genes. For most of these targeted clones, chimerism and germline transmission can be scored through a coat color marker. The targeted alleles have been designed to be adaptable research tools that can be efficiently altered by recombinase-mediated cassette exchange to create reporter, conditional and other allelic variants. This miRNA knockout (mirKO) resource can be searched electronically and is available from ES cell repositories for distribution to the scientific community.     

Characterizing homologues of crop domestication genes in poorly described wild relatives by high‐throughput sequencing of whole genomes

Wild crop relatives represent a source of novel alleles for crop genetic improvement. Screening biodiversity for useful or diverse gene homologues has often been based upon the amplification of targeted genes using available sequence information to design primers that amplify the target gene region across species. The crucial requirement of this approach is the presence of sequences with sufficient conservation across species to allow for the design of universal primers. This approach is often not successful with diverse organisms or highly variable genes. Massively parallel sequencing (MPS) can quickly produce large amounts of sequence data and provides a viable option for characterizing homologues of known genes in poorly described genomes. MPS of genomic DNA was used to obtain species‐specific sequence information for 18 rice genes related to domestication characteristics in a wild relative of rice, Microlaena stipoides. Species‐specific primers were available for 16 genes compared with 12 genes using the universal primer method. The use of species‐specific primers had the potential to cover 92% of the sequence of these genes, while traditional universal primers could only be designed to cover 80%. A total of 24 species‐specific primer pairs were used to amplify gene homologues, and 11 primer pairs were successful in capturing six gene homologues. The 23 million, 36‐base pair (bp) paired end reads, equated to an average of 2X genome coverage, facilitated the successful amplification and sequencing of six target gene homologues, illustrating an important approach to the discovery of useful genes in wild crop relatives.     

Control of pancreatic β cell regeneration by glucose metabolism

Recent studies revealed a surprising regenerative capacity of insulin-producing β cells in mice, suggesting that regenerative therapy for human diabetes could in principle be achieved. Physiologic β cell regeneration under stressed conditions relies on accelerated proliferation of surviving β cells, but the factors that trigger and control this response remain unclear. Using islet transplantation experiments, we show that β cell mass is controlled systemically rather than by local factors such as tissue damage. Chronic changes in β cell glucose metabolism, rather than blood glucose levels per se, are the main positive regulator of basal and compensatory β cell proliferation in vivo. Intracellularly, genetic and pharmacologic manipulations reveal that glucose induces β cell replication via metabolism by glucokinase, the first step of glycolysis, followed by closure of K(ATP) channels and membrane depolarization. Our data provide a molecular mechanism for homeostatic control of β cell mass by metabolic demand.     

The prevalence of Campylobacter amongst a free-range broiler breeder flock was primarily affected by flock age

Campylobacter successfully colonizes broiler chickens, but little is known about the longer term natural history of colonization, since most flocks are slaughtered at an immature age. In this study, the prevalence and genetic diversity of Campylobacter colonizing a single free-range broiler breeder flock was investigated over the course of a year. The age of the flock was the most important factor in determining both the prevalence and diversity of Campylobacter over time. There was no correlation with season, temperature, the amount of rain and sunshine, or the dynamics of colonization amongst geographically and temporally matched broiler flocks. The higher prevalence rates coincided with the age at which broiler chickens are typically slaughtered, but then in the absence of bio-security or other intervention methods, and despite changes in flock management, the prevalence fell to significantly lower levels for the remainder of the study. The genetic diversity of Campylobacter increased as the flock aged, implying that genotypes were accumulated within the flock and may persist for a long time. A better understanding of the ecology of Campylobacter within commercial chicken flocks will allow the design of more effective farm-based interventions.