Age-related and species-specific methylation changes in the protein-coding marmoset sperm epigenome.

The sperm epigenome is thought to affect the developmental programming of the resulting embryo, influencing health and disease in later life. Age-related methylation changes in the sperm of old fathers may mediate the increased risks for reproductive and offspring medical problems. The impact of paternal age on sperm methylation has been extensively studied in humans and, to a lesser extent, in rodents and cattle. Here, we performed a comparative analysis of paternal age effects on protein-coding genes in the human and marmoset sperm methylomes. The marmoset has gained growing importance as a non-human primate model of aging and age-related diseases. Using reduced representation bisulfite sequencing, we identified age-related differentially methylated transcription start site (ageTSS) regions in 204 marmoset and 27 human genes. The direction of methylation changes was the opposite, increasing with age in marmosets and decreasing in humans. None of the identified ageTSS was differentially methylated in both species. Although the average methylation levels of all TSS regions were highly correlated between marmosets and humans, with the majority of TSS being hypomethylated in sperm, more than 300 protein-coding genes were endowed with species-specifically (hypo)methylated TSS. Several genes of the glycosphingolipid (GSL) biosynthesis pathway, which plays a role in embryonic stem cell differentiation and regulation of development, were hypomethylated (<5%) in human and fully methylated (>95%) in marmoset sperm. The expression levels and patterns of defined sets of GSL genes differed considerably between human and marmoset pre-implantation embryo stages and blastocyst tissues, respectively.

The dynamics of colicin E9 release from Escherichia coli in native conditions.

Colicin (Col) plasmid contains colicin encoding genes arranged in an operon controlled by an SOS inducible promoter. Therefore, any external stresses to the host cell can induce the expression of the downstream genes in the Col operon, including a lysis gene. The lysis protein is involved in the extracellular release of colicin through lysis of the producer cells, which causes a decline in culture turbidity. However, it is not yet known that E. coli cells with the native pColE9-J plasmid hold the same level of cell death at the population level following a set of induced conditions. In this study, using a mitomycin C sensitivity assay along with a live dead staining method of detection, we showed that the native pColE9-J plasmid, which unusually carries an extended Col operon (ColE9) containing two lysis genes, did not confer a rapid decline in the culture turbidity following induction with mitomycin C. Interestingly a subset of the cells suffered perturbation of their outer membrane, which was not observed from single lysis mutant (∆celE or ∆celI) cells. This observed heterogeneity in the colicin E9 release leading to differential outer membrane perforation may bring a competitive advantage to these cells in a mixed population.

Rat post-implantation epiblast-derived pluripotent stem cells produce functional germ cells.

In mammals, pluripotent cells transit through a continuum of distinct molecular and functional states en route to initiating lineage specification. Capturing pluripotent stem cells (PSCs) mirroring in vivo pluripotent states provides accessible in vitro models to study the pluripotency program and mechanisms underlying lineage restriction. Here, we develop optimal culture conditions to derive and propagate post-implantation epiblast-derived PSCs (EpiSCs) in rats, a valuable model for biomedical research. We show that rat EpiSCs (rEpiSCs) can be reset toward the naive pluripotent state with exogenous Klf4, albeit not with the other five candidate genes (Nanog, Klf2, Esrrb, Tfcp2l1, and Tbx3) effective in mice. Finally, we demonstrate that rat EpiSCs retain competency to produce authentic primordial germ cell-like cells that undergo functional gametogenesis leading to the birth of viable offspring. Our findings in the rat model uncover principles underpinning pluripotency and germline competency across species.

mRNA-based generation of marmoset PGCLCs capable of differentiation into gonocyte-like cells.

Primate germ cell development remains largely unexplored due to limitations in sample collection and the long duration of development. In mice, primordial germ cell-like cells (PGCLCs) derived from pluripotent stem cells (PSCs) can develop into functional gametes by in vitro culture or in vivo transplantation. Such PGCLC-mediated induction of mature gametes in primates is highly useful for understanding human germ cell development. Since marmosets generate functional sperm earlier than other species, recapitulating the whole male germ cell development process is technically more feasible. Here, we induced the differentiation of iPSCs into gonocyte-like cells via PGCLCs in marmosets. First, we developed an mRNA transfection-based method to efficiently generate PGCLCs. Subsequently, to promote PGCLC differentiation, xenoreconstituted testes (xrtestes) were generated in the mouse kidney capsule. PGCLCs show progressive DNA demethylation and stepwise expression of developmental marker genes. This study provides an efficient platform for the study of marmoset germ cell development.

Origin and segregation of the human germline.

Human germline-soma segregation occurs during weeks 2-3 in gastrulating embryos. Although direct studies are hindered, here, we investigate the dynamics of human primordial germ cell (PGCs) specification using in vitro models with temporally resolved single-cell transcriptomics and in-depth characterisation using in vivo datasets from human and nonhuman primates, including a 3D marmoset reference atlas. We elucidate the molecular signature for the transient gain of competence for germ cell fate during peri-implantation epiblast development. Furthermore, we show that both the PGCs and amnion arise from transcriptionally similar TFAP2A-positive progenitors at the posterior end of the embryo. Notably, genetic loss of function experiments shows that TFAP2A is crucial for initiating the PGC fate without detectably affecting the amnion and is subsequently replaced by TFAP2C as an essential component of the genetic network for PGC fate. Accordingly, amniotic cells continue to emerge from the progenitors in the posterior epiblast, but importantly, this is also a source of nascent PGCs.

Epigenetic resetting in the human germ line entails histone modification remodeling.

Epigenetic resetting in the mammalian germ line entails acute DNA demethylation, which lays the foundation for gametogenesis, totipotency, and embryonic development. We characterize the epigenome of hypomethylated human primordial germ cells (hPGCs) to reveal mechanisms preventing the widespread derepression of genes and transposable elements (TEs). Along with the loss of DNA methylation, we show that hPGCs exhibit a profound reduction of repressive histone modifications resulting in diminished heterochromatic signatures at most genes and TEs and the acquisition of a neutral or paused epigenetic state without transcriptional activation. Efficient maintenance of a heterochromatic state is limited to a subset of genomic loci, such as evolutionarily young TEs and some developmental genes, which require H3K9me3 and H3K27me3, respectively, for efficient transcriptional repression. Accordingly, transcriptional repression in hPGCs presents an exemplary balanced system relying on local maintenance of heterochromatic features and a lack of inductive cues.

Heterogeneity in the spontaneous induction of the promoter of the ColE9 operon in Escherichia coli.

Spontaneous production of E colicins is known to occur in only a small fraction of colicinogenic population. The current study aimed to determine if the same holds true for the production of colicin E9 in real time, by investigating the induction dynamics of the promoter of the ColE9 operon which results in the expression of the ColE9 activity and functional genes. A novel fluorescent reporter was constructed which carries the fusion of the ColE9 promoter and the gfpmut2 gene in a low copy number plasmid that was compatible with the native ColE9-J plasmid. Using the fluorescent reporter construct in the non colicinogenic E. coli cells, the induction of the ColE9 promoter was investigated. The current study demonstrates that the spontaneous induction of the ColE9 promoter occurs in a heterogenous manner and this heterogeneity is maintained in a bacterial population for several generations suggesting that it is unlikely due to any irreversible mutation in the bacterial culture. Furthermore, the same investigations were repeated using the colicin E9 producing E. coli cells. Flow cytometry analysis revealed that 7.1 ± 0.68% of the colicin E9 producing E. coli cells expressed GFP albeit only 2.45 ± 0.30% was observed from non colicinogenic E. coli cells. The considerable increase in the number of the fluorescent cells was likely due to the DNase activity of colicin E9 produced by their clonemates, resulting the auto-induction, which can be abolished with the inactivation of the DNase activity of the colicin E9.

Microgel culture and spatial identity mapping elucidate the signalling requirements for primate epiblast and amnion formation.

The early specification and rapid growth of extraembryonic membranes are distinctive hallmarks of primate embryogenesis. These complex tasks are resolved through an intricate combination of signals controlling the induction of extraembryonic lineages and, at the same time, safeguarding the pluripotent epiblast. Here, we delineate the signals orchestrating primate epiblast and amnion identity. We encapsulated marmoset pluripotent stem cells into agarose microgels and identified culture conditions for the development of epiblast- and amnion-spheroids. Spatial identity mapping authenticated spheroids generated in vitro by comparison with marmoset embryos in vivo. We leveraged the microgel system to functionally interrogate the signalling environment of the post-implantation primate embryo. Single-cell profiling of the resulting spheroids demonstrated that activin/nodal signalling is required for embryonic lineage identity. BMP4 promoted amnion formation and maturation, which was counteracted by FGF signalling. Our combination of microgel culture, single-cell profiling and spatial identity mapping provides a powerful approach to decipher the essential cues for embryonic and extraembryonic lineage formation in primate embryogenesis.

An integrated atlas of human placental development delineates essential regulators of trophoblast stem cells.

The trophoblast lineage safeguards fetal development by mediating embryo implantation, immune tolerance, nutritional supply and gas exchange. Human trophoblast stem cells (hTSCs) provide a platform to study lineage specification of placental tissues; however, the regulatory network controlling self-renewal remains elusive. Here, we present a single-cell atlas of human trophoblast development from zygote to mid-gestation together with single-cell profiling of hTSCs. We determine the transcriptional networks of trophoblast lineages in vivo and leverage probabilistic modelling to identify a role for MAPK signalling in trophoblast differentiation. Placenta- and blastoid-derived hTSCs consistently map between late trophectoderm and early cytotrophoblast, in contrast to blastoid-trophoblast, which correspond to trophectoderm. We functionally assess the requirement of the predicted cytotrophoblast network in an siRNA-screen and reveal 15 essential regulators for hTSC self-renewal, including MAZ, NFE2L3, TFAP2C, NR2F2 and CTNNB1. Our human trophoblast atlas provides a powerful analytical resource to delineate trophoblast cell fate acquisition, to elucidate transcription factors required for hTSC self-renewal and to gauge the developmental stage of in vitro cultured cells.

Spatial profiling of early primate gastrulation in utero.

Gastrulation controls the emergence of cellular diversity and axis patterning in the early embryo. In mammals, this transformation is orchestrated by dynamic signalling centres at the interface of embryonic and extraembryonic tissues1-3. Elucidating the molecular framework of axis formation in vivo is fundamental for our understanding of human development4-6 and to advance stem-cell-based regenerative approaches7. Here we illuminate early gastrulation of marmoset embryos in utero using spatial transcriptomics and stem-cell-based embryo models. Gaussian process regression-based 3D transcriptomes delineate the emergence of the anterior visceral endoderm, which is hallmarked by conserved (HHEX, LEFTY2, LHX1) and primate-specific (POSTN, SDC4, FZD5) factors. WNT signalling spatially coordinates the formation of the primitive streak in the embryonic disc and is counteracted by SFRP1 and SFRP2 to sustain pluripotency in the anterior domain. Amnion specification occurs at the boundaries of the embryonic disc through ID1, ID2 and ID3 in response to BMP signalling, providing a developmental rationale for amnion differentiation of primate pluripotent stem cells (PSCs). Spatial identity mapping demonstrates that primed marmoset PSCs exhibit the highest similarity to the anterior embryonic disc, whereas naive PSCs resemble the preimplantation epiblast. Our 3D transcriptome models reveal the molecular code of lineage specification in the primate embryo and provide an in vivo reference to decipher human development.

A hexa-species transcriptome atlas of mammalian embryogenesis delineates metabolic regulation across three different implantation modes.

Mammalian embryogenesis relies on glycolysis and oxidative phosphorylation to balance the generation of biomass with energy production. However, the dynamics of metabolic regulation in the postimplantation embryo in vivo have remained elusive due to the inaccessibility of the implanted conceptus for biochemical studies. To address this issue, we compiled single-cell embryo profiling data in six mammalian species and determined their metabolic dynamics through glycolysis and oxidative phosphorylation associated gene expression. Strikingly, we identify a conserved switch from bivalent respiration in the late blastocyst towards a glycolytic metabolism in early gastrulation stages across species, which is independent of embryo implantation. Extraembryonic lineages followed the dynamics of the embryonic lineage, except visceral endoderm. Finally, we demonstrate that in vitro primate embryo culture substantially impacts metabolic gene regulation by comparison to in vivo samples. Our work reveals a conserved metabolic programme despite different implantation modes and highlights the need to optimise postimplantation embryo culture protocols.

Nuclear transfer system for the direct induction of embryonic transcripts from intra- and cross-species nuclei using mouse 4-cell embryos.

Reprogramming of somatic nuclei toward the embryonic state has been studied using nuclear transfer (NT) to an oocyte at the metaphase II (MII) stage. In this NT, a somatic nucleus transplanted into an MII oocyte of the same species undergoes DNA replication and cell division before activating embryonic genes. Here, we describe a direct NT protocol using 4-cell stage mouse embryos that enables reprogramming of intra- and cross-species nuclei to express embryonic genes without requiring DNA replication and cell division. For complete details on the use and execution of this protocol, please refer to Tomikawa et al. (2021).

Sequential enhancer state remodelling defines human germline competence and specification.

Germline-soma segregation is a fundamental event during mammalian embryonic development. Here we establish the epigenetic principles of human primordial germ cell (hPGC) development using in vivo hPGCs and stem cell models recapitulating gastrulation. We show that morphogen-induced remodelling of mesendoderm enhancers transiently confers the competence for hPGC fate, but further activation favours mesoderm and endoderm fates. Consistently, reducing the expression of the mesendodermal transcription factor OTX2 promotes the PGC fate. In hPGCs, SOX17 and TFAP2C initiate activation of enhancers to establish a core germline programme, including the transcriptional repressor PRDM1 and pluripotency factors POU5F1 and NANOG. We demonstrate that SOX17 enhancers are the critical components in the regulatory circuitry of germline competence. Furthermore, activation of upstream cis-regulatory elements by an optimized CRISPR activation system is sufficient for hPGC specification. We reveal an enhancer-linked germline transcription factor network that provides the basis for the evolutionary divergence of mammalian germlines.

Mapping the biogenesis of forward programmed megakaryocytes from induced pluripotent stem cells.

Platelet deficiency, known as thrombocytopenia, can cause hemorrhage and is treated with platelet transfusions. We developed a system for the production of platelet precursor cells, megakaryocytes, from pluripotent stem cells. These cultures can be maintained for >100 days, implying culture renewal by megakaryocyte progenitors (MKPs). However, it is unclear whether the MKP state in vitro mirrors the state in vivo, and MKPs cannot be purified using conventional surface markers. We performed single-cell RNA sequencing throughout in vitro differentiation and mapped each state to its equivalent in vivo. This enabled the identification of five surface markers that reproducibly purify MKPs, allowing us insight into their transcriptional and epigenetic profiles. Last, we performed culture optimization, increasing MKP production. Together, this study has mapped parallels between the MKP states in vivo and in vitro and allowed the purification of MKPs, accelerating the progress of in vitro-derived transfusion products toward the clinic.

Cell division- and DNA replication-free reprogramming of somatic nuclei for embryonic transcription.

Nuclear transfer systems represent the efficient means to reprogram a cell and in theory provide a basis for investigating the development of endangered species. However, conventional nuclear transfer using oocytes of laboratory animals does not allow reprogramming of cross-species nuclei owing to defects in cell divisions and activation of embryonic genes. Here, we show that somatic nuclei transferred into mouse four-cell embryos arrested at the G2/M phase undergo reprogramming toward the embryonic state. Remarkably, genome-wide transcriptional reprogramming is induced within a day, and ZFP281 is important for this replication-free reprogramming. This system further enables transcriptional reprogramming of cells from Oryx dammah, now extinct in the wild. Thus, our findings indicate that arrested mouse embryos are competent to induce intra- and cross-species reprogramming. The direct induction of embryonic transcripts from diverse genomes paves a unique approach for identifying mechanisms of transcriptional reprogramming and genome activation from a diverse range of species.

Building a stem cell-based primate uterus.

The uterus is the organ for embryo implantation and fetal development. Most current models of the uterus are centred around capturing its function during later stages of pregnancy to increase the survival in pre-term births. However, in vitro models focusing on the uterine tissue itself would allow modelling of pathologies including endometriosis and uterine cancers, and open new avenues to investigate embryo implantation and human development. Motivated by these key questions, we discuss how stem cell-based uteri may be engineered from constituent cell parts, either as advanced self-organising cultures, or by controlled assembly through microfluidic and print-based technologies.

Time-series transcriptomics reveals a BBX32-directed control of acclimation to high light in mature Arabidopsis leaves.

The photosynthetic capacity of mature leaves increases after several days' exposure to constant or intermittent episodes of high light (HL) and is manifested primarily as changes in chloroplast physiology. How this chloroplast-level acclimation to HL is initiated and controlled is unknown. From expanded Arabidopsis leaves, we determined HL-dependent changes in transcript abundance of 3844 genes in a 0-6 h time-series transcriptomics experiment. It was hypothesized that among such genes were those that contribute to the initiation of HL acclimation. By focusing on differentially expressed transcription (co-)factor genes and applying dynamic statistical modelling to the temporal transcriptomics data, a regulatory network of 47 predominantly photoreceptor-regulated transcription (co-)factor genes was inferred. The most connected gene in this network was B-BOX DOMAIN CONTAINING PROTEIN32 (BBX32). Plants overexpressing BBX32 were strongly impaired in acclimation to HL and displayed perturbed expression of photosynthesis-associated genes under LL and after exposure to HL. These observations led to demonstrating that as well as regulation of chloroplast-level acclimation by BBX32, CRYPTOCHROME1, LONG HYPOCOTYL5, CONSTITUTIVELY PHOTOMORPHOGENIC1 and SUPPRESSOR OF PHYA-105 are important. In addition, the BBX32-centric gene regulatory network provides a view of the transcriptional control of acclimation in mature leaves distinct from other photoreceptor-regulated processes, such as seedling photomorphogenesis.

Consensus-based antimicrobial resistance and stewardship competencies for UK undergraduate medical students.

BACKGROUND: In the UK there is limited coverage of antimicrobial stewardship across postgraduate curricula and evidence that final year medical students have insufficient and inconsistent antimicrobial stewardship teaching. A national undergraduate curriculum for antimicrobial resistance and stewardship is required to standardize an adequate level of understanding for all future doctors. OBJECTIVES: To provide a UK national consensus on competencies for antimicrobial resistance and stewardship for undergraduate medical education. METHODS: Using the modified Delphi method over two online survey rounds, an expert panel comprising leads for infection teaching from 25 UK medical schools reviewed competency descriptors for antimicrobial resistance and stewardship education. RESULTS: There was a response rate of 100% with all 28 experts who agreed to take part completing both survey rounds. Following the first-round survey, of the initial 55 descriptors, 43 reached consensus (78%). The second-round survey included the 12 descriptors from the first round in which agreement had not been reached, four amended descriptors and 12 new descriptors following qualitative feedback from the panel members. Following the second-round survey, a total of 58 consensus-based competency descriptors within six overarching domains were identified. CONCLUSIONS: The consensus-based competency descriptors defined here can be used to inform standards, design curricula, develop assessment tools and direct UK undergraduate medical education.

Early enteral nutrition within 24 hours of lower gastrointestinal surgery versus later commencement for length of hospital stay and postoperative complications.

BACKGROUND: This is an update of the review last published in 2011. It focuses on early postoperative enteral nutrition after lower gastrointestinal surgery. Traditional management consisted of 'nil by mouth', where patients receive fluids followed by solids after bowel function has returned. Although several trials have reported lower incidence of infectious complications and faster wound healing upon early feeding, other trials have shown no effect. The immediate advantage of energy intake (carbohydrates, protein or fat) could enhance recovery with fewer complications, and this warrants a systematic evaluation. OBJECTIVES: To evaluate whether early commencement of postoperative enteral nutrition (within 24 hours), oral intake and any kind of tube feeding (gastric, duodenal or jejunal), compared with traditional management (delayed nutritional supply) is associated with a shorter length of hospital stay (LoS), fewer complications, mortality and adverse events in patients undergoing lower gastrointestinal surgery (distal to the ligament of Treitz). SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, the Cochrane Library 2017, issue 10), Ovid MEDLINE (1950 to 15 November 2017), Ovid Embase (1974 to 15 November 2017). We also searched for ongoing trials in ClinicalTrials.gov and World Health Organization International Clinical Trials Registry Platform (15 November 2017). We handsearched reference lists of identified studies and previous systematic reviews. SELECTION CRITERIA: We included randomised controlled trials (RCT) comparing early commencement of enteral nutrition (within 24 hours) with no feeding in adult participants undergoing lower gastrointestinal surgery. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed study quality using the Cochrane 'Risk of bias' tool tailored to this review and extracted data. Data analyses were conducted according to the Cochrane recommendations.We rated the quality of evidence according to GRADE.Primary outcomes were LoS and postoperative complications (wound infections, intraabdominal abscesses, anastomotic dehiscence, pneumonia).Secondary outcomes were: mortality, adverse events (nausea, vomiting), and quality of life (QoL).LoS was estimated using mean difference (MD (presented as mean +/- SD). For other outcomes we estimated the common risk ratio (RR) and calculated the associated 95% confidence intervals. For analysis, we used an inverse-variance random-effects model for the primary outcome (LoS) and Mantel-Haenszel random-effects models for the secondary outcomes. We also performed Trial Sequential Analyses (TSA). MAIN RESULTS: We identified 17 RCTs with 1437 participants undergoing lower gastrointestinal surgery. Most studies were at high or unclear risk of bias in two or more domains. Six studies were judged as having low risk of selection bias for random sequence generation and insufficient details were provided for judgement on allocation concealment in all 17 studies. With regards to performance and deception bias; 14 studies reported no attempt to blind participants and blinding of personnel was not discussed either. Only one study was judged as low risk of bias for blinding of outcome assessor. With regards to incomplete outcome data, three studies were judged to be at high risk because they had more than 10% difference in missing data between groups. For selective reporting, nine studies were judged as unclear as protocols were not provided and eight studies had issues with either missing data or incomplete reporting of results.LOS was reported in 16 studies (1346 participants). The mean LoS ranged from four days to 16 days in the early feeding groups and from 6.6 days to 23.5 days in the control groups. Mean difference (MD) in LoS was 1.95 (95% CI, -2.99 to -0.91, P < 0.001) days shorter in the early feeding group. However, there was substantial heterogeneity between included studies (I2 = 81, %, Chi2 = 78.98, P < 0.00001), thus the overall quality of evidence for LoS is low. These results were confirmed by the TSA showing that the cumulative Z-curve crossed the trial sequential monitoring boundary for benefit.We found no differences in the incidence of postoperative complications: wound infection (12 studies, 1181 participants, RR 0.99, 95%CI 0.64 to 1.52, very low-quality evidence), intraabdominal abscesses (6 studies, 554 participants, RR 1.00, 95%CI 0.26 to 3.80, low-quality evidence), anastomotic leakage/dehiscence (13 studies, 1232 participants, RR 0.78, 95%CI 0.38 to 1.61, low-quality evidence; number needed to treat for an additional beneficial outcome (NNTB) = 100), and pneumonia (10 studies, 954 participants, RR 0.88, 95%CI 0.32 to 2.42, low-quality evidence; NNTB = 333).Mortality was reported in 12 studies (1179 participants), and showed no between-group differences (RR = 0.56, 95%CI, 0.21 to 1.52, P = 0.26, I2 = 0%, Chi2 = 3.08, P = 0.96, low-quality evidence). The most commonly reported cause of death was anastomotic leakage, sepsis and acute myocardial infarction.Seven studies (613 participants) reported vomiting (RR 1.23, 95%CI, 0.96 to 1.58, P = 0.10, I2 = 0%, Chi2 = 4.98, P = 0.55, low-quality evidence; number needed to treat for an additional harmful outcome (NNTH) = 19), and two studies (118 participants) reported nausea (RR 0.95, 0.71 to 1.26, low-quality evidence). Four studies reported combined nausea and vomiting (RR 0.94, 95%CI 0.51 to 1.74, very low-quality evidence). One study reported QoL assessment; the scores did not differ between groups at 30 days after discharge on either QoL scale EORTC QLQ-C30 or EORTC QlQ-OV28 (very low-quality evidence). AUTHORS' CONCLUSIONS: This review suggests that early enteral feeding may lead to a reduced postoperative LoS, however cautious interpretation must be taken due to substantial heterogeneity and low-quality evidence. For all other outcomes (postoperative complications, mortality, adverse events, and QoL) the findings are inconclusive, and further trials are justified to enhance the understanding of early feeding for these. In this updated review, only a few additional studies have been included, and these were small and of poor quality.To improve the evidence, future trials should address quality issues and focus on clearly defining and measuring postoperative complications to allow for better comparison between studies. However due to the introduction of fast track protocols which already include an early feeding component, future trials may be challenging. A more feasible trial may be to investigate the effect of differing postoperative energy intake regimens on relevant outcomes.

Competition in Biofilms between Cystic Fibrosis Isolates of Pseudomonas aeruginosa Is Shaped by R-Pyocins.

Pseudomonas aeruginosa is an opportunistic pathogen and the leading cause of morbidity and mortality in cystic fibrosis (CF) patients. P. aeruginosa infections are difficult to treat due to a number of antibiotic resistance mechanisms and the organism's propensity to form multicellular biofilms. Epidemic strains of P. aeruginosa often dominate within the lungs of individual CF patients, but how they achieve this is poorly understood. One way that strains of P. aeruginosa can compete is by producing chromosomally encoded bacteriocins, called pyocins. Three major classes of pyocin have been identified in P. aeruginosa: soluble pyocins (S types) and tailocins (R and F types). In this study, we investigated the distribution of S- and R-type pyocins in 24 clinical strains isolated from individual CF patients and then focused on understanding their roles in interstrain competition. We found that (i) each strain produced only one R-pyocin type, but the number of S-pyocins varied between strains, (ii) R-pyocins were generally important for strain dominance during competition assays in planktonic cultures and biofilm communities in strains with both disparate R- and S-pyocin subtypes, and (iii) purified R-pyocins demonstrated significant antimicrobial activity against established biofilms. Our work provides support for a role played by R-pyocins in the competition between P. aeruginosa strains and helps explain why certain strains and lineages of P. aeruginosa dominate and displace others during CF infection. Furthermore, we demonstrate the potential of exploiting R-pyocins for therapeutic gains in an era when antibiotic resistance is a global concern.IMPORTANCE A major clinical problem caused by Pseudomonas aeruginosa, is chronic biofilm infection of the lungs in individuals with cystic fibrosis (CF). Epidemic P. aeruginosa strains dominate and displace others during CF infection, but these intraspecies interactions remain poorly understood. Here we demonstrate that R-pyocins (bacteriocins) are important factors in driving competitive interactions in biofilms between P. aeruginosa strains isolated from different CF patients. In addition, we found that these phage-like pyocins are inhibitory against mature biofilms of susceptible strains. This highlights the potential of R-pyocins as antimicrobial and antibiofilm agents at a time when new antimicrobial therapies are desperately needed.