Link projections and flypes

Let \Pi be a link projection in S^2. John Conway and later Francis Bonahon and Larry Siebenmann undertook to split $\Pi$ into canonical pieces. These pieces received different names: basic or polyhedral diagrams on one hand, rational, algebraic, bretzel, arborescent diagrams on the other hand. This paper proposes a thorough presentation of the theory, known to happy fews. We apply the existence and uniqueness theorem for the canonical decomposition to the classification of Haseman circles and to the localisation of the flypes

Application of genetically encoded redox biosensors to measure dynamic changes in the glutathione, bacillithiol and mycothiol redox potentials in pathogenic bacteria

Gram-negative bacteria utilize glutathione (GSH) as their major LMW thiol. However, most Gram-positive bacteria do not encode enzymes for GSH biosynthesis and produce instead alternative LMW thiols, such as bacillithiol (BSH) and mycothiol (MSH). BSH is utilized by Firmicutes and MSH is the major LMW thiol of Actinomycetes. LMW thiols are required to maintain the reduced state of the cytoplasm, but are also involved in virulence mechanisms in human pathogens, such as Staphylococcus aureus, Mycobacterium tuberculosis, Streptococcus pneumoniae, Salmonella enterica subsp. Typhimurium and Listeria monocytogenes. Infection conditions often cause perturbations of the intrabacterial redox balance in pathogens, which is further affected under antibiotics treatments. During the last years, novel glutaredoxin-fused roGFP2 biosensors have been engineered in many eukaryotic organisms, including parasites, yeast, plants and human cells for dynamic live-imaging of the GSH redox potential in different compartments. Likewise bacterial roGFP2-based biosensors are now available to measure the dynamic changes in the GSH, BSH and MSH redox potentials in model and pathogenic Gram-negative and Gram-positive bacteria. In this review, we present an overview of novel functions of the bacterial LMW thiols GSH, MSH and BSH in pathogenic bacteria in virulence regulation. Moreover, recent results about the application of genetically encoded redox biosensors are summarized to study the mechanisms of host-pathogen interactions, persistence and antibiotics resistance. In particularly, we highlight recent biosensor results on the redox changes in the intracellular food-borne pathogen Salmonella Typhimurium as well as in the Gram-positive pathogens S. aureus and M. tuberculosis during infection conditions and under antibiotics treatments. These studies established a link between ROS and antibiotics resistance with the intracellular LMW thiol-redox potential. Future applications should be directed to compare the redox potentials among different clinical isolates of these pathogens in relation to their antibiotics resistance and to screen for new ROS-producing drugs as promising strategy to combat antimicrobial resistance

Direct, biomimetic synthesis of (+)-artemone via a stereoselective, organocatalytic cyclization

We present a four-step synthesis of (+)-artemone from (–)- linalool, featuring iminium organocatalysis of a doubly diastereoselective conjugate addition reaction. The strategy follows a proposed biosynthetic pathway, rapidly generates stereochemical complexity, uses no protecting groups, and minimizes redox manipulations

Shrimp farming vulnerability and adaptation to climate change in CA MAU, Vietnam

Shrimp farming is the livelihood for thousands of inhabitants in the Ca Mau of Vietnam, but these shrimp farmers are facing significant risks arising from climate change events. The research aimed to discover the adverse effects of climate change to shrimp production, and the vulnerability and adaptation of the shrimp farmers to climate change events. It was based in the main on the perspectives of shrimp farmers themselves from four shrimp farming systems (rice-shrimp rotation farming- RSRF, integrated shrimp-mangrove farming- ISMF, separated shrimp-mangrove farming- SSMF, and intensive shrimp farming- ISF) along with local experts working in the region. Findings from interviews and focus groups with these stakeholders were subsequently benchmarked against original or already published data. Three research questions guided the study: How might climate change events be affecting shrimp farming in Ca Mau Province? How is shrimp farming in different systems vulnerable to climate change events? How can Ca Mau Province shrimp farmers adapt to the climate change events? Climate change events in this research include extreme climate events (e.g. tropical storms), sea level rise and high tide, temperature changes, rainfall changes, and irregular weather. The researcher interviewed eleven local experts, surveyed 100 farmer households, documented the relationship between climate parameters and shrimp productivity, and conducted focus group discussions with representatives of the four shrimp farming systems to access the vulnerability of shrimp production. Key findings regarding the three research questions follow. First, adverse effects of climate change events on shrimp farming have already been occurring according to respondents in the Ca Mau region of Vietnam. The literature likewise provides evidence of this. The five climate change events ranked as most affecting shrimp production during the last decade and similarly identified for the future were seasonal pattern changes, increased intensity or irregular rain, sea level rise and high tides, and extreme climate events. Differences in climate change effects were recorded for different shrimp farming systems. Although ISMF and SSMF farmers (on the coast) were more concerned about extreme climate events, sea level rise and high tides than ISF farmers (further inland), a significantly strong positive relationship between water level and shrimp production suggests there are more benefits for shrimp farming from a higher water level; at least for such rises recorded to date. On the other hand, RSRF farmers were most concerned with seasonal pattern changes and intense rain or irregular rain; here, a significantly negative relationship between rainfall and shrimp production may suggest more severe impacts arising from these climate changes in the future. These findings contrast with existing published accounts regarding aquaculture in the Mekong Delta in that high water temperature was ranked as the greatest risk in shrimp production. Second, several contrasting findings regarding vulnerability and adaptation of shrimp farmers to climate change were evident. While the majority of shrimp farmers hoped that their children would change occupation, many nevertheless wished for them to become shrimp farmers and most of these farmers themselves in the four systems expect to continue with shrimp farming in the future, even though shrimp production would likely be seriously impacted by climate change in the future. Intensive shrimp farming operations with higher cultivation levels and greater diversity of income sources for the families involved were found to be the least vulnerable to the perceived current and future effects of climate change. Integrated shrimp-mangrove farming was found to be less vulnerable than rice-shrimp rotation and the separated shrimp-mangrove approach. Higher income shrimp farmers were found to be more likely to already be undertaking adaptation measures to address the consequences of climate change events and those with greater social involvement were more likely to have better adaption capacity to climate change events. While it was found that shrimp farmers had taken responses to the adverse effects of climate change event in the last decade, there were no clear strategies in place for the future. Taken together, these research findings suggest that intensification, integration, and cooperation would be good adaptation options for shrimp farmers in Ca Mau Province in the face of future climate change events. This research makes an original contribution to knowledge through capturing: (i) the perspectives of shrimp farmers themselves on how climate change affects their operations in the four farming systems; (ii) the climate change events most affecting shrimp production in the last decade and posing the greatest threat in the future; (iii) the significant relationship between shrimp productivity and rainfall and water level; (iv) the variable vulnerability in the four farming approaches; and (v) suggestions for shrimp farming intensification, integration, and increased farmer cooperation as key adaptation options to future climate change. The research findings have important policy implications for decision makers who want to support the shrimp farming system to be less vulnerable to existing and expected climate change impacts. The results of this study also have implications for the provincial governments, residents in the Mekong Delta, and in other brackish aquaculture farming regions to gain a better understanding of climate change risks to shrimp production. One such strategy might be to both enhance shrimp farmer resilience to the adverse effects of climate change events and improve cultivation techniques for farmers in different shrimp farming systems

Staphylococcus aureus Uses the Bacilliredoxin (BrxAB)/Bacillithiol Disulfide Reductase (YpdA) Redox Pathway to Defend Against Oxidative Stress Under Infections

Staphylococcus aureus is a major human pathogen and has to cope with reactive oxygen and chlorine species (ROS, RCS) during infections. The low molecular weight thiol bacillithiol (BSH) is an important defense mechanism of S. aureus for detoxification of ROS and HOCl stress to maintain the reduced state of the cytoplasm. Under HOCl stress, BSH forms mixed disulfides with proteins, termed as S-bacillithiolations, which are reduced by bacilliredoxins (BrxA and BrxB). The NADPH-dependent flavin disulfide reductase YpdA is phylogenetically associated with the BSH synthesis and BrxA/B enzymes and was recently suggested to function as BSSB reductase (Mikheyeva et al., 2019). Here, we investigated the role of the complete bacilliredoxin BrxAB/BSH/YpdA pathway in S. aureus COL under oxidative stress and macrophage infection conditions in vivo and in biochemical assays in vitro. Using HPLC thiol metabolomics, a strongly enhanced BSSB level and a decreased BSH/BSSB ratio were measured in the S. aureus COL ΔypdA deletion mutant under control and NaOCl stress. Monitoring the oxidation degree (OxD) of the Brx-roGFP2 biosensor revealed that YpdA is required for regeneration of the reduced BSH redox potential (EBSH) upon recovery from oxidative stress. In addition, the ΔypdA mutant was impaired in H2O2 detoxification as measured with the novel H2O2-specific Tpx-roGFP2 biosensor. Phenotype analyses further showed that BrxA and YpdA are required for survival under NaOCl and H2O2 stress in vitro and inside murine J-774A.1 macrophages in infection assays in vivo. Finally, NADPH-coupled electron transfer assays provide evidence for the function of YpdA in BSSB reduction, which depends on the conserved Cys14 residue. YpdA acts together with BrxA and BSH in de-bacillithiolation of S-bacillithiolated GapDH. In conclusion, our results point to a major role of the BrxA/BSH/YpdA pathway in BSH redox homeostasis in S. aureus during recovery from oxidative stress and under infections

A forward genetic screen identifies host factors that influence the lysis-lysogeny decision in phage lambda

The lysis‐lysogeny decision made by bacteriophage lambda is one of the classic problems of molecular biology. Shortly after infecting a cell, the virus can either go down the lytic pathway and make more viruses, or go down the lysogenic pathway and integrate itself into the host genome. While much is known about how this decision takes place, the extent to which host physiology influences this decision and the mechanisms by which this influence takes place has remained mysterious. To answer this question, we performed a forward genetic screen to systematically identify all of the genes in E. coli that influence the lysis‐lysogeny decision. Our results demonstrate previously unknown links between host physiology and viral decision making and shed new light on this classic system