Analysis of the effectiveness of hygiene measures and COVID-19 vaccination at a tertiary-care university hospital during the first two years of the SARS-CoV-2 pandemic.

Objective: Assessment of the effectiveness of protective measures at a tertiary-care hospital during the SARS-CoV-2 infection waves to provide advice for future pandemics. Design: Retrospective cohort study among hospital staff using in-house surveillance data. Setting: University Hospital Erlangen (UKER), a tertiary-care provider in Bavaria, Germany. Methods: We outline the preventive measures introduced at UKER and retrospectively assess their effectiveness using anonymized monitoring data that were collected during the SARS-CoV-2 pandemic from February 2020 to the end of January 2022. Analysed data includes the incidence of SARS-CoV-2 infections among employees, the frequency of high-risk contacts with infected patients or staff members and breakthrough infections considering the context of exposure. Results: The cumulative incidence of SARS-CoV-2 infections among UKER employees was higher before, but lower after the vaccination campaign when compared to the general population. Healthcare workers (HCW), notably physicians and nurses, were especially at risk of infection compared to other UKER employees with less direct patient contact (OR 1.36 [95% CI 1.18-1.57 p < 0.001]). Breakthrough infections mostly occurred after exposure during private life, i.e. in situations without protective equipment. The frequency of high-risk contacts during direct patient care remained stable after SARS-CoV-2 vaccination. Prior to vaccination, 5.2% of HCW with direct patient care tested positive for SARS-CoV-2 within 14 days. After vaccination until the onset of the Omicron wave, conversion rate dropped to 0%. Conclusions: This study provides real-world data on the effectiveness of vaccination, contact tracing, personal protective equipment and general hygiene measures during the SARS-CoV-2 pandemic. Based on our findings, we recommend a protective approach combining all these preventive measures.

Analytical Validation of an Immunohistochemical 7-Biomarker Prognostic Assay (immunoprint®) for Early-Stage Cutaneous Melanoma in Archival Tissue of Patients with AJCC v8 T2-T3 Disease.

Selected patients with early-stage melanoma have a "hidden high risk" of poor oncologic outcomes. They might benefit from clinical trials, and ultimately, if warranted by trial results, judicious everyday use of adjuvant therapy. A promising tool to identify these individuals is the immunoprint® assay. This immunohistochemical 7-biomarker prognostic test was clinically validated in three independent cohorts (N = 762) to classify early-stage patients as high-risk or low-risk regarding melanoma recurrence and mortality. Using College of American Pathologists (CAP) recommendations, we analytically validated this assay in primary melanoma specimens (N = 20 patients). We assessed assay precision by determining consistency of risk classification under repeated identical conditions (repeatability) or across varying conditions (reproducibility), involving separate assay runs, operators (laboratory scientists), and/or observers (e.g., dermatopathologists). Reference classification was followed by five analytical validation phases: intra-run/intra-operator, intra-observer, inter-run, inter-operator, and inter-observer. Concordance of classifications in each phase was assessed via Fleiss' kappa (primary endpoint) and percent agreement (secondary endpoint). Seven-marker signature classification demonstrated high consistency across validation categories (Fleiss' kappa 0.864-1.000; overall percent agreement 95-100%), in 9/10 cases, exceeding, and in 1/10 cases, closely approaching, CAP's recommended 0.9 level. The 7-marker assay has now been verified to provide excellent repeatability, reproducibility, and precision, besides having been clinically validated.

An optimized protocol for isolation of hepatic leukocytes retrieved from murine and NASH liver biopsies.

Immune dysregulation and inflammation by hepatic-resident leukocytes is considered a key step in disease progression of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis toward cirrhosis and hepatocellular carcinoma. Here, we provide a protocol for isolation and characterization of liver-resident immune cells from fine-needle biopsies obtained from a rodent model and humans. We describe steps for isolating leukocytes, cell sorting, and RNA extraction and sequencing. We then detail procedures for low-input mRNA sequencing analyses.

Glucocorticoids regulate lipid mediator networks by reciprocal modulation of 15-lipoxygenase isoforms affecting inflammation resolution.

Glucocorticoids (GC) are potent anti-inflammatory agents, broadly used to treat acute and chronic inflammatory diseases, e.g., critically ill COVID-19 patients or patients with chronic inflammatory bowel diseases. GC not only limit inflammation but also promote its resolution although the underlying mechanisms are obscure. Here, we reveal reciprocal regulation of 15-lipoxygenase (LOX) isoform expression in human monocyte/macrophage lineages by GC with respective consequences for the biosynthesis of specialized proresolving mediators (SPM) and their 15-LOX-derived monohydroxylated precursors (mono-15-OH). Dexamethasone robustly up-regulated pre-mRNA, mRNA, and protein levels of ALOX15B/15-LOX-2 in blood monocyte-derived macrophage (MDM) phenotypes, causing elevated SPM and mono-15-OH production in inflammatory cell types. In sharp contrast, dexamethasone blocked ALOX15/15-LOX-1 expression and impaired SPM formation in proresolving M2-MDM. These dexamethasone actions were mimicked by prednisolone and hydrocortisone but not by progesterone, and they were counteracted by the GC receptor (GR) antagonist RU486. Chromatin immunoprecipitation (ChIP) assays revealed robust GR recruitment to a putative enhancer region within intron 3 of the ALOX15B gene but not to the transcription start site. Knockdown of 15-LOX-2 in M1-MDM abolished GC-induced SPM formation and mono-15-OH production. Finally, ALOX15B/15-LOX-2 upregulation was evident in human monocytes from patients with GC-treated COVID-19 or patients with IBD. Our findings may explain the proresolving GC actions and offer opportunities for optimizing GC pharmacotherapy and proresolving mediator production.

Synthesis and biological evaluation of simplified ajudazol derivatives reveal potent 5-lipoxygenase inhibition and considerable apoptotic activity in neuroblastoma cells.

Simplified analogues of the myxobacterial polyketide ajudazol were obtained by synthesis and evaluated for their biological activities. Potent simplified 5-lipoxygenase inhibitors were identified. Moreover, strong antiproliferative and apoptotic activities were observed in brain cancer cell lines at low nano- to micromolar concentrations.

Anti-Inflammatory Activities of Arnica montana Planta Tota versus Flower Extracts: Analytical, In Vitro and In Vivo Mouse Paw Oedema Model Studies.

Arnica montana is well known for its anti-inflammatory properties. While the anti-inflammatory activity of Arnica flowers (Arnicae flos) has been extensively studied, that of the whole plant (Arnicae planta tota) is less characterized. We compared the ability of Arnicae planta tota and Arnicae flos extracts to inhibit the pro-inflammatory NF-κB-eicosanoid pathway, using several in vitro and in vivo assays. We showed that Arnicae planta tota inhibited NF-κB reporter activation, with an IC50 of 15.4 µg/mL (vs. 52.5 µg/mL for Arnicae flos). Arnicae planta tota also inhibited LPS-induced expression of ALOX5 and PTGS2 genes in human differentiated macrophages. ALOX5 and PTGS2 encode the 5-lipoxygenase (5-LO) and cyclooxygenase-2 (COX-2) enzymes that initialize the conversion of arachidonic acid into leukotrienes and prostaglandins, respectively. Arnicae planta tota inhibited 5-LO and COX-2 enzymatic activity in vitro and in human primary peripheral blood cells, with lower IC50 compared to Arnicae flos. Finally, Arnicae planta tota applied topically reduced carrageenan-induced mouse paw oedema more efficiently than Arnicae flos. Altogether, Arnicae planta tota displayed a superior anti-inflammatory activity compared to Arnicae flos, suggesting that Arnicae-planta-tota-containing products might be more effective in alleviating the manifestations of acute inflammation than those based on Arnicae flos alone.

Adult alcohol drinking and emotional tone are mediated by neutral sphingomyelinase during development in males.

Alcohol use, abuse, and addiction, and resulting health hazards are highly sex-dependent with unknown mechanisms. Previously, strong links between the SMPD3 gene and its coded protein neutral sphingomyelinase 2 (NSM) and alcohol abuse, emotional behavior, and bone defects were discovered and multiple mechanisms were identified for females. Here we report strong sex-dimorphisms for central, but not for peripheral mechanisms of NSM action in mouse models. Reduced NSM activity resulted in enhanced alcohol consumption in males, but delayed conditioned rewarding effects. It enhanced the acute dopamine response to alcohol, but decreased monoaminergic systems adaptations to chronic alcohol. Reduced NSM activity increased depression- and anxiety-like behavior, but was not involved in alcohol use for the self-management of the emotional state. Constitutively reduced NSM activity impaired structural development in the brain and enhanced lipidomic sensitivity to chronic alcohol. While the central effects were mostly opposite to NSM function in females, similar roles in bone-mediated osteocalcin release and its effects on alcohol drinking and emotional behavior were observed. These findings support the view that the NSM and multiple downstream mechanism may be a source of the sex-differences in alcohol use and emotional behavior.

Modulation of Inflammation-Related Lipid Mediator Pathways by Celastrol During Human Macrophage Polarization.

Background and Purpose: Celastrol (CS) is a major active ingredient of the Chinese/Asian herb Tripterygium wilfordii that is frequently used as phytomedicine to treat inflammation and autoimmune diseases. We showed before that short-term exposure to CS (1 µM) favorably impacts the biosynthesis of inflammation-related lipid mediators (LM) in human polarized macrophages by modulating the activities of different lipoxygenases (LOXs). However, whether CS regulates the expression of LOXs and other related LM-biosynthetic enzymes during macrophage polarization is unknown. Here, we investigated how CS affects LM-biosynthetic enzyme expression on the protein level and studied concomitant LM signature profiles during polarization of human monocyte-derived macrophages (MDM) towards M1- and M2-like phenotypes. Methods and Results: We used LM metabololipidomics to study the long-term effects of CS on LM profile signatures after manipulation of human monocyte-derived macrophages (MDM) during polarization. Exposure of MDM to low concentrations of CS (ie, 0.2 µM) during polarization to an inflammatory M1 phenotype potently suppressed the formation of pro-inflammatory cyclooxygenase (COX)- and 5-LOX-derived LM, especially prostaglandin (PG)E2. Notably, gene and enzyme expression of COX-2 and microsomal PGE2 synthase (mPGES)-1 as well as M1 markers were strongly decreased by CS during M1-MDM polarization, along with impaired activation of nuclear factor-κB and p38 mitogen-activated protein kinase. During IL-4-induced M2 polarization, CS decreased the capacity of the resulting M2-MDM to generate pro-inflammatory COX and 5-LOX products as well but it also reduced the formation of 12/15-LOX products and specialized pro-resolving mediators, without affecting the levels of liberated fatty acid substrates. Conclusion: Depending on the timing and concentration, CS not only favorably affects LOX activities in macrophages but also the expression of LM-biosynthetic enzymes during macrophage polarization connected to changes of inflammation-related LM which might be of relevance for potential application of CS to treat inflammatory disorders.

Combined Clinical, Epidemiological, and Genome-Based Analysis Identified a Nationwide Outbreak of Burkholderia cepacia Complex Infections Caused by Contaminated Mouthwash Solutions.

Background: In September 2018, Burkholderia cepacia complex (BCC) infections in 3 patients associated with exposure to a mouthwash solution (MWS) were reported to the Robert Koch Institute (RKI). As the product was still on the market and the scale of the outbreak was unclear, a nation-wide investigation was initiated. Methods: We aimed to investigate BCC infections/colonizations associated with MWS. Hospitals, laboratories, and public health services were informed that BCC isolates should be sent to the RKI. These isolates were typed by pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS) including development of an ad hoc core genome MLST (cgMLST) scheme. Results: In total, 36 patients from 6 hospitals met the case definition, the last patient in November 2018. Twenty-nine isolates from 26 of these patients were available for typing. WGS analysis revealed 2 distinct cgMLST clusters. Cluster 1 (Burkholderia arboris) contained isolates from patients and MWS obtained from 4 hospitals and isolates provided by the manufacturer. Patient and MWS isolates from another hospital were assigned to cluster 2 (B. cepacia). Conclusions: The combined clinical, epidemiological, and microbiological investigation, including whole-genome analysis, allowed for uncovering a supraregional BCC outbreak in health care settings. Strains of B. arboris and B. cepacia were identified as contaminating species of MWS bottles and subsequent colonization and putative infection of patients in several hospitals. Despite a recall of the product by the manufacturer in August 2018, the outbreak lasted until December 2018. Reporting of contaminated medical products and recalls should be optimized to protect patients.

Natural chalcones elicit formation of specialized pro-resolving mediators and related 15-lipoxygenase products in human macrophages.

Specialized pro-resolving mediators (SPMs) comprise lipid mediators (LMs) produced from polyunsaturated fatty acids (PUFAs) via stereoselective oxygenation particularly involving 12/15-lipoxygenases (LOXs). In contrast to pro-inflammatory LMs such as leukotrienes formed by 5-LOX and prostaglandins formed by cyclooxygenases, the SPMs have anti-inflammatory and inflammation-resolving properties. Although glucocorticoids and non-steroidal anti-inflammatory drugs (NSAIDs) that block prostaglandin production are still prime therapeutics for inflammation-related diseases despite severe side effects, novel concepts focus on SPMs as immunoresolvents for anti-inflammatory pharmacotherapy. Here, we studied the natural chalcone MF-14 and the corresponding dihydrochalcone MF-15 from Melodorum fruticosum, for modulating the biosynthesis of LM including leukotrienes, prostaglandins, SPM and their 12/15-LOX-derived precursors in human monocyte-derived macrophage (MDM) M1- and M2-like phenotypes. In MDM challenged with Staphylococcus aureus-derived exotoxins both compounds (10 µM) significantly suppressed 5-LOX product formation but increased the biosynthesis of 12/15-LOX products, especially in M2-MDM. Intriguingly, in resting M2-MDM, MF-14 and MF-15 strikingly evoked generation of 12/15-LOX products and of SPMs from liberated PUFAs, along with translocation of 15-LOX-1 to membranous compartments. Enhanced 12/15-LOX product formation by the chalcones was evident also when exogenous PUFAs were supplied, excluding increased substrate supply as sole underlying mechanism. Rather, MF-14 and MF-15 stimulate the activity of 15-LOX-1, supported by experiments with HEK293 cells transfected with either 5-LOX, 15-LOX-1 or 15-LOX-2. Together, the natural chalcone MF-14 and the dihydrochalcone MF-15 favorably modulate LM biosynthesis in human macrophages by suppressing pro-inflammatory leukotrienes but stimulating formation of SPMs by differential interference with 5-LOX and 15-LOX-1.

Neutral sphingomyelinase mediates the co-morbidity trias of alcohol abuse, major depression and bone defects.

Mental disorders are highly comorbid and occur together with physical diseases, which are often considered to arise from separate pathogenic pathways. We observed in alcohol-dependent patients increased serum activity of neutral sphingomyelinase. A genetic association analysis in 456,693 volunteers found associations of haplotypes of SMPD3 coding for NSM-2 (NSM) with alcohol consumption, but also with affective state, and bone mineralisation. Functional analysis in mice showed that NSM controls alcohol consumption, affective behaviour, and their interaction by regulating hippocampal volume, cortical connectivity, and monoaminergic responses. Furthermore, NSM controlled bone-brain communication by enhancing osteocalcin signalling, which can independently supress alcohol consumption and reduce depressive behaviour. Altogether, we identified a single gene source for multiple pathways originating in the brain and bone, which interlink disorders of a mental-physical co-morbidity trias of alcohol abuse-depression/anxiety-bone disorder. Targeting NSM and osteocalcin signalling may, thus, provide a new systems approach in the treatment of a mental-physical co-morbidity trias.

Analysis of Boswellic Acid Contents and Related Pharmacological Activities of Frankincense-Based Remedies That Modulate Inflammation.

Extracts of frankincense, the gum resin of Boswellia species, have been extensively used in traditional folk medicine since ancient times and are still of great interest as promising anti-inflammatory remedies in Western countries. Despite their common therapeutic use and the intensive pharmacological research including studies on active ingredients, modes of action, bioavailability, pharmacokinetics, and clinical efficacy, frankincense preparations are available as nutraceuticals but have not yet approved as a drug on the market. A major issue of commercially available frankincense nutraceuticals is the striking differences in their composition and quality, especially related to the content of boswellic acids (BAs) as active ingredients, mainly due to the use of material from divergent Boswellia species but also because of different work-up and extraction procedures. Here, we assessed three frequently used frankincense-based preparations for their BA content and the interference with prominent pro-inflammatory actions and targets that have been proposed, that is, 5-lipoxygenase and leukotriene formation in human neutrophils, microsomal prostaglandin E2 synthase-1, and inflammatory cytokine secretion in human blood monocytes. Our data reveal striking differences in the pharmacological efficiencies of these preparations in inflammation-related bioassays which obviously correlate with the amounts of BAs they contain. In summary, high-quality frankincense extracts display powerful anti-inflammatory effectiveness against multiple targets which can be traced back to BAs as bioactive ingredients.

14,17,18-Trihydroxy-Eicosatetraenoic Acid: A Novel Pro-Resolving Lipid Mediator from Marine Microalgae.

Specialized pro-resolving mediators (SPMs) are enzymatically oxygenated derivatives of polyunsaturated fatty acids that function as central immunoregulators in mammals. Among them are resolvins (Rvs) that stimulate the clearance of harmful stimuli and limit pro-inflammatory processes. Because of their beneficial features and their high potency, SPMs are promising molecules for anti-inflammatory therapy. Besides mammals, also marine algae form lipid mediators such as prostaglandins and leukotrienes. In particular, microalgae are attractive candidates for the production of bioactive high-value metabolites. Here, we identified the diatom Cylindrotheca closterium as a prolific producer of SPMs. The diatom forms RvE3 and novel structurally related eicosanoids, including 14S/R,17R,18R-trihydroxy-eicosatetraenoic acid, which displays inflammation-resolving and anti-inflammatory bioactivities. This pro-resolving compound might enable advancements in anti-inflammatory therapy in mammals.

Effect of 158 herbal remedies on human TRPV1 and the two-pore domain potassium channels KCNK2, 3 and 9.

BACKGROUND AND AIM: Herbal medicines are used to treat a broad number of maladies. However, the pharmacological profile of most remedies is poorly understood. We investigated the effect of herbal remedies from kampo, traditional Chinese medicine (TCM) and other phytotherapies on human two-pore domain potassium channels (KCNK channels; TREK-1, TASK-1 and TASK-3) as well as the human TRPV1 channel. KCNK channels are responsible for the background potassium current of excitable cells, thus essential for the maintenance of the resting membrane potential. Hence, modulators of KCNK channels are of medical significance, e.g. for the treatment of sleep disorders and pain. The transient receptor potential channel TRPV1 is a pain detector for noxious heat. Agonists of this receptor are still used for the treatment of pain in ectopic applications. EXPERIMENTAL PROCEDURE: We evaluated the effect of 158 herbal remedies on these channels in a heterologous expression system (Xenopus laevis oocytes) using the two-electrode voltage-clamp technique with the aim of increasing the comprehension of their pharmacological profile. RESULTS AND CONCLUSION: Some remedies with modulating effects were identified such as Angelica pubescens (radix), which inhibit TASK-1 and TASK-3 channels. Furthermore, the modulatory effects of the most effective remedies on the two TASK family members TASK-1 and TASK-3 correlate positively, reflecting their close relation. For the TRPV1 channel Terminalia chebula and Alchemilla xanthochlora were identified as potentiators. This study identifies a variety of herbal remedies as modulators of human K2P and TRPV1 channels and gives new insights into the pharmacological profile of these herbal remedies.

Synergism between IL7R and CXCR4 drives BCR-ABL induced transformation in Philadelphia chromosome-positive acute lymphoblastic leukemia.

Ph+ acute lymphoblastic leukemia (ALL) is characterized by the expression of an oncogenic fusion kinase termed BCR-ABL1. Here, we show that interleukin 7 receptor (IL7R) interacts with the chemokine receptor CXCR4 to recruit BCR-ABL1 and JAK kinases in close proximity. Treatment with BCR-ABL1 kinase inhibitors results in elevated expression of IL7R which enables the survival of transformed cells when IL7 was added together with the kinase inhibitors. Importantly, treatment with anti-IL7R antibodies prevents leukemia development in xenotransplantation models using patient-derived Ph+ ALL cells. Our results suggest that the association between IL7R and CXCR4 serves as molecular platform for BCR-ABL1-induced transformation and development of Ph+ ALL. Targeting this platform with anti-IL7R antibody eliminates Ph+ ALL cells including those with resistance to commonly used ABL1 kinase inhibitors. Thus, anti-IL7R antibodies may provide alternative treatment options for ALL in general and may suppress incurable drug-resistant leukemia forms.

Whole-genome analysis of vancomycin-resistant Enterococcus faecium causing nosocomial outbreaks suggests the occurrence of few endemic clonal lineages in Bavaria, Germany.

OBJECTIVES: Infections caused by vancomycin-resistant Enterococcus faecium (VREfm) represent a major public health concern due to limited treatment options. Among invasive isolates of VREfm, ST117, ST80 and ST78 represent the most frequently detected STs by MLST in Germany. In this study, we investigated the genetic diversity of isolates of VREfm recovered from different nosocomial outbreaks in Bavaria, Germany, by WGS. METHODS: Between January 2018 and April 2019, 99 non-replicate isolates of VREfm originating from nosocomial outbreaks at eight different hospitals in Bavaria were investigated for genetic diversity by WGS. In detail, complex types (CTs) were identified by core-genome MLST. Furthermore, an SNP analysis was performed for all VREfm strains. RESULTS: Most of the isolates of this study (76%) belonged to three major clonal groups, which occurred in at least three hospitals: ST80/CT1065 vanB (n = 45; six hospitals), ST117/CT71 vanB (n = 11; four hospitals) and ST78/CT894like vanA (n = 19; three hospitals). Moreover, isolates of the predominant lineage ST80/CT1065 vanB showed a maximum difference of 36 SNPs as revealed by SNP analysis. CONCLUSIONS: Whole-genome analysis of VREfm causing nosocomial outbreaks suggests the occurrence of few endemic clonal lineages in Bavarian hospital settings, namely ST80/CT1065 vanB, ST117/CT71 vanB and ST78/CT894like vanA. Further studies are needed for a better understanding of the factors affecting the successful spread of the above-mentioned lineages.

Communication between human macrophages and epithelial cancer cell lines dictates lipid mediator biosynthesis.

In tumors, cancer cells coexist and communicate with macrophages that can promote tumorigenesis via pro-inflammatory signals. Lipid mediators (LMs), produced mainly by cyclooxygenases (COXs) or lipoxygenases (LOs), display a variety of biological functions with advantageous or deleterious consequences for tumors. Here, we investigated how the communication between human monocyte-derived M2-like macrophages (MDM) and cancer cells affects LM biosynthesis using LM metabololipidomics. Coculture of human MDM with human A549 epithelial lung carcinoma cells, separated by a semipermeable membrane, increased LM formation by MDM upon subsequent activation. Strongest effects were observed on 5-LO-derived LM. While expression of the 5-LO pathway was not altered, p38 MAPK and the downstream MAPKAPK-2 that phosphorylates and stimulates 5-LO were more susceptible for activation in MDM upon precedent coculture with A549 cells as compared to monocultures. Accordingly, the p38 MAPK inhibitor Skepinone-L selectively prevented this increase in 5-LO product formation. Also, 5-LO-/15-LO-derived LM including lipoxin A4, resolvin D2 and D5 were elevated after coculture with A549 cells, correlating to increased 15-LO-1 protein levels. In contrast to cancer cells, coincubation with non-transformed human umbilical vein endothelial cells (HUVEC) did not affect LM production in MDM. Vice versa, MDM increased COX-2 protein expression and COX-mediated prostanoid formation in cancer cells. Conclusively, our data reveal that the communication between MDM and cancer cells can strikingly modulate the biosynthetic capacities to produce bioactive LM with potential relevance for tumor biology.

15-Hydroperoxy-PGE2 : Intermediate in Mammalian and Algal Prostaglandin Biosynthesis.

Arachidonic-acid-derived prostaglandins (PGs), specifically PGE2 , play a central role in inflammation and numerous immunological reactions. The enzymes of PGE2 biosynthesis are important pharmacological targets for anti-inflammatory drugs. Besides mammals, certain edible marine algae possess a comprehensive repertoire of bioactive arachidonic-acid-derived oxylipins including PGs that may account for food poisoning. Described here is the analysis of PGE2 biosynthesis in the red macroalga Gracilaria vermiculophylla that led to the identification of 15-hydroperoxy-PGE2 , a novel precursor of PGE2 and 15-keto-PGE2 . Interestingly, this novel precursor is also produced in human macrophages where it represents a key metabolite in an alternative biosynthetic PGE2 pathway in addition to the well-established arachidonic acid-PGG2 -PGH2 -PGE2 route. This alternative pathway of mammalian PGE2 biosynthesis may open novel opportunities to intervene with inflammation-related diseases.

Associated Bacteria Affect Sexual Reproduction by Altering Gene Expression and Metabolic Processes in a Biofilm Inhabiting Diatom.

Diatoms are unicellular algae with a fundamental role in global biogeochemical cycles as major primary producers at the base of aquatic food webs. In recent years, chemical communication between diatoms and associated bacteria has emerged as a key factor in diatom ecology, spurred by conceptual and technological advancements to study the mechanisms underlying these interactions. Here, we use a combination of physiological, transcriptomic, and metabolomic approaches to study the influence of naturally co-existing bacteria, Maribacter sp. and Roseovarius sp., on the sexual reproduction of the biofilm inhabiting marine pennate diatom Seminavis robusta. While Maribacter sp. severely reduces the reproductive success of S. robusta cultures, Roseovarius sp. slightly enhances it. Contrary to our expectation, we demonstrate that the effect of the bacterial exudates is not caused by altered cell-cycle regulation prior to the switch to meiosis. Instead, Maribacter sp. exudates cause a reduced production of diproline, the sexual attraction pheromone of S. robusta. Transcriptomic analyses show that this is likely an indirect consequence of altered intracellular metabolic fluxes in the diatom, especially those related to amino acid biosynthesis, oxidative stress response, and biosynthesis of defense molecules. This study provides the first insights into the influence of bacteria on diatom sexual reproduction and adds a new dimension to the complexity of a still understudied phenomenon in natural diatom populations.