The role of the phosphopantetheinyltransferase enzyme, PswP, in the biosynthesis of antimicrobial secondary metabolites by <em>Serratia marcescens </em>Db10

Phosphopantetheinyltransferase (PPTase) enzymes fulfil essential roles in primary and secondary metabolism in prokaryotes, archaea and eukaryotes. PPTase enzymes catalyse the essential modification of the carrier protein domain of fatty acid synthases, polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs). In bacteria and fungi, NRPS and PKS enzymes are often responsible for the biosynthesis of secondary metabolites with clinically relevant properties; these secondary metabolites include a variety of antimicrobial peptides. We have previously shown that in the Gram-negative bacterium Serratia marcescens Db10, the PPTase enzyme PswP is essential for the biosynthesis of an NRPS-PKS dependent antibiotic called althiomycin. In this work we utilize bioinformatic analyses to classify PswP as belonging to the F/KES subfamily of Sfp type PPTases and to putatively identify additional NRPS substrates of PswP, in addition to the althiomycin NRPS-PKS, in Ser. marcescens Db10. We show that PswP is required for the production of three diffusible metabolites by this organism, each possessing antimicrobial activity against Staphylococcus aureus. Genetic analyses identify the three metabolites as althiomycin, serrawettin W2 and an as-yet-uncharacterized siderophore, which may be related to enterobactin. Our results highlight the use of an individual PPTase enzyme in multiple biosynthetic pathways, each contributing to the ability of Ser. marcescens to inhibit competitor bacteria by the production of antimicrobial secondary metabolites

The insect pathogen Serratia marcescens Db10 uses a hybrid non-ribosomal peptide synthetase-polyketide synthase to produce the antibiotic althiomycin

There is a continuing need to discover new bioactive natural products, such as antibiotics, in genetically-amenable micro-organisms. We observed that the enteric insect pathogen, Serratia marcescens Db10, produced a diffusible compound that inhibited the growth of Bacillis subtilis and Staphyloccocus aureus. Mapping the genetic locus required for this activity revealed a putative natural product biosynthetic gene cluster, further defined to a six-gene operon named alb1-alb6. Bioinformatic analysis of the proteins encoded by alb1-6 predicted a hybrid non-ribosomal peptide synthetase-polyketide synthase (NRPS-PKS) assembly line (Alb4/5/6), tailoring enzymes (Alb2/3) and an export/resistance protein (Alb1), and suggested that the machinery assembled althiomycin or a related molecule. Althiomycin is a ribosome-inhibiting antibiotic whose biosynthetic machinery had been elusive for decades. Chromatographic and spectroscopic analyses confirmed that wild type S. marcescens produced althiomycin and that production was eliminated on disruption of the alb gene cluster. Construction of mutants with in-frame deletions of specific alb genes demonstrated that Alb2-Alb5 were essential for althiomycin production, whereas Alb6 was required for maximal production of the antibiotic. A phosphopantetheinyl transferase enzyme required for althiomycin biosynthesis was also identified. Expression of Alb1, a predicted major facilitator superfamily efflux pump, conferred althiomycin resistance on another, sensitive, strain of S. marcescens. This is the first report of althiomycin production outside of the Myxobacteria or Streptomyces and paves the way for future exploitation of the biosynthetic machinery, since S. marcescens represents a convenient and tractable producing organism

Cell Death and Reproductive Regression in Female Schistosoma mansoni

The vitellarium is a highly proliferative organ, producing cells which are incorporated along with a fertilized ovum into the schistosome egg. Vitellarial growth fails to occur in virgin female schistosomes in single sex (female-only) infections, and involution of this tissue, which is accompanied by physical shrinkage of the entire worm, occurs when mature females sexually regress upon removal from their male partners. We have found that upon removal from their hosts into tissue culture, female parasites regress whether they are mated or not, but that cessation of egg production and a decline in expression of the vitelline gene p14 is delayed by mating. We used BrdU labeling to investigate whether there was a loss of proliferation in the vittelarium that might account for regression and found that the proliferation rate declined equally in paired and singled females once placed into culture. However, TUNEL staining and Caspase 3 activity measurements indicate that the loss of vitrellarial cellularity associated with regression is associated with profound apoptotic vitelline cell death, which is not apparent in the vitellaria of paired females immediately ex vivo, and which develops in vitro regardless of whether males are present or not. Furthermore, primordial vitellaria in virgin females have a high frequency of apoptotic cells but are characterized by a proliferation rate that is indistinguishable from that in fully developed vitellaria in mature paired females. Taken together, our data suggest that the vitelline proliferation rate is independent of pairing status. In contrast, the survival of vitelline cells, and therefore the development of the vitellarium, is highly male-dependent. Both processes are negatively affected by removal from the host regardless of whether male worms are present or not, and are unsustainable using standard tissue culture approaches

Omega-3 and Omega-6 Fatty acids and risk of psychotic outcomes in the ALSPAC birth cohort

Background Long chain polyunsaturated fatty acid (PUFA) levels have been implicated in the pathology of psychotic disorders. We investigated the relationship between childhood PUFA levels and later psychotic experiences (PE's) in a large birth cohort. Methods Plasma levels of Ω-3 and Ω-6 fatty acids (FA's) were assayed at ages 7 and 16 years. PE's were assessed at ages 12 and 18 years using a semi-structured interview. Primary outcome was any PE's at 18 years; sensitivity analyses examined incident PE's between ages 12 and 18 years, persistent PE's (at 12 and 18) and psychotic disorder at 18 years. Genetic instruments for Ω-3 and Ω-6 were derived and used in a multivariable Mendelian Randomization analysis. Results Higher levels of Ω-6 FA's AA, OA and AdA at age 7 years were weakly associated with a reduced risk for PE's at 18 years, however, effect sizes were small and attenuated after adjusting for confounders (strongest evidence for OA; adjusted OR, 0.842; 95% CI, 0.711, 0.998; p, 0.048). Total Ω-6 levels at age 16 years were associated with an increased odds of psychotic disorder at age 18 years. However, there was no association between Ω-6/Ω-3 ratio and psychosis outcomes, nor with genetic instruments of total Ω-3 or Ω-6 levels. Conclusions There is no strong evidence that total plasma Ω-3 FA levels or Ω-6/Ω-3 ratios in childhood and mid-adolescence are associated with increased risk for PE's or psychotic disorder, but very marginal evidence that alterations in the Ω-6 pathway at developmental time points might influence risk2

Merging enzymes with chemocatalysis for amide bond synthesis

Amides are one of the most fundamental chemical bonds in nature. In addition to proteins and other metabolites, many valuable synthetic products comprise amide bonds. Despite this, there is a need for more sustainable amide synthesis. Herein, we report an integrated next generation multi-catalytic system, merging nitrile hydratase enzymes with a Cu-catalysed N-arylation reaction in a single reaction vessel, for the construction of ubiquitous amide bonds. This synergistic one-pot combination of chemo- and biocatalysis provides an amide bond disconnection to precursors, that are orthogonal to those in classical amide synthesis, obviating the need for protecting groups and delivering amides in a manner unachievable using existing catalytic regimes. Our integrated approach also affords broad scope, very high (molar) substrate loading, and has excellent functional group tolerance, telescoping routes to natural product derivatives, drug molecules, and challenging chiral amides under environmentally friendly conditions at scale

Manipulation of P-TEFb control machinery by HIV: recruitment of P-TEFb from the large form by Tat and binding of HEXIM1 to TAR

Basal transcription of the HIV LTR is highly repressed and requires Tat to recruit the positive transcription elongation factor, P-TEFb, which functions to promote the transition of RNA polymerase II from abortive to productive elongation. P-TEFb is found in two forms in cells, a free, active form and a large, inactive complex that also contains 7SK RNA and HEXIM1 or HEXIM2. Here we show that HIV infection of cells led to the release of P-TEFb from the large form. Consistent with Tat being the cause of this effect, transfection of a FLAG-tagged Tat in 293T cells caused a dramatic shift of P-TEFb out of the large form to a smaller form containing Tat. In vitro, Tat competed with HEXIM1 for binding to 7SK, blocked the formation of the P-TEFb–HEXIM1–7SK complex, and caused the release P-TEFb from a pre-formed P-TEFb–HEXIM1–7SK complex. These findings indicate that Tat can acquire P-TEFb from the large form. In addition, we found that HEXIM1 binds tightly to the HIV 5′ UTR containing TAR and recruits and inhibits P-TEFb activity. This suggests that in the absence of Tat, HEXIM1 may bind to TAR and repress transcription elongation of the HIV LTR

Development of a new, combined rapid method using phage and PCR for detection and identification of viable Mycobacterium paratuberculosis bacteria within 48 hours

The FASTPlaqueTB assay is an established diagnostic aid for the rapid detection of Mycobacterium tuberculosis from human sputum samples. Using the FASTPlaqueTB assay reagents, viable Mycobacterium avium subsp. paratuberculosis cells were detected as phage plaques in just 24 h. The bacteriophage used does not infect M. avium subsp. paratuberculosis alone, so to add specificity to this assay, a PCR-based identification method was introduced to amplify M. avium subsp. paratuberculosis-specific sequences from the DNA of the mycobacterial cell detected by the phage. To give further diagnostic information, a multiplex PCR method was developed to allow simultaneous amplification of either M. avium subsp. paratuberculosis or M. tuberculosis complex-specific sequences from plaque samples. Combining the plaque PCR technique with the phage-based detection assay allowed the rapid and specific detection of viable M. avium subsp. paratuberculosis in milk samples in just 48 h

A Mendelian randomization study of the causal association between anxiety phenotypes and schizophrenia

Schizophrenia shows a genetic correlation with both anxiety disorder and neuroticism, a trait strongly associated with anxiety. However, genetic correlations do not discern causality from genetic confounding. We therefore aimed to investigate whether anxiety-related phenotypes lie on the causal pathway to schizophrenia using Mendelian randomization (MR). Four MR methods, each with different assumptions regarding instrument validity, were used to investigate casual associations of anxiety and neuroticism related phenotypes on schizophrenia, and vice versa: inverse variance weighted (IVW), weighted median, weighted mode, and, when appropriate, MR Egger regression. MR provided evidence of a causal effect of neuroticism on schizophrenia (IVW odds ratio [OR]: 1.33, 95% confidence interval [CI]: 1.12-1.59), but only weak evidence of a causal effect of anxiety on schizophrenia (IVW OR: 1.10, 95% CI: 1.01-1.19). There was also evidence of a causal association from schizophrenia liability to anxiety disorder (IVW OR: 1.28, 95% CI: 1.18-1.39) and worry (IVW beta: 0.05, 95% CI: 0.03-0.07), but effect estimates from schizophrenia to neuroticism were inconsistent in the main analysis. The evidence of neuroticism increasing schizophrenia risk provided by our results supports future efforts to evaluate neuroticism- or anxiety-based therapies to prevent onset of psychotic disorders

Derivation and validation of a novel prognostic scale (modified–stroke subtype, Oxfordshire Community Stroke Project classification, age, and prestroke modified Rankin) to predict early mortality in acute stroke

Background and Purpose The stroke subtype, Oxfordshire Community Stroke Project classification, age, and prestroke modified Rankin (SOAR) score is a prognostic scale proposed for early mortality prediction after acute stroke. We aimed to evaluate whether including a measure of initial stroke severity (National Institutes of Health Stroke Scale and modified-SOAR [mSOAR] scores) would improve the prognostic accuracy. Methods Using Anglia Stroke and Heart Clinical Network data, 2008 to 2011, we assessed the performance of SOAR and mSOAR against in-hospital mortality using area under the receiver operating curve statistics. We externally validated the prognostic utility of SOAR and mSOAR using an independent cohort data set from Glasgow. We described calibration using Hosmer–Lemeshow goodness-of-fit test. Results A total of 1002 patients were included in the derivation cohort, and 105 (10.5%) died as inpatients. The area under the receiver operating curves for outcome of early mortality derived from the SOAR and mSOAR scores were 0.79 (95% confidence interval, 0.75–0.84) and 0.83 (95% confidence interval, 0.79–0.86), respectively (P=0.001). The external validation data set contained 1012 patients with stroke; of which, 121 (12.0%) patients died within 90 days. The mSOAR scores identified the risk of early mortality ranging from 3% to 42%. External validation of mSOAR score yielded an area under the receiver operating curve of 0.84 (95% confidence interval, 0.82–0.88) for outcome of early mortality. Calibration was good (P=0.70 for the Hosmer–Lemeshow test). Conclusions—Adding National Institutes of Health Stroke Scale data to create a modified-SOAR score improved prognostic utility in both derivation and validation data sets. The mSOAR may have clinical utility by using easily available data to predict mortality