Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation.

Turritopsis dohrnii is the only metazoan able to rejuvenate repeatedly after its medusae reproduce, hinting at biological immortality and challenging our understanding of aging. We present and compare whole-genome assemblies of T. dohrnii and the nonimmortal Turritopsis rubra using automatic and manual annotations, together with the transcriptome of life cycle reversal (LCR) process of T. dohrnii. We have identified variants and expansions of genes associated with replication, DNA repair, telomere maintenance, redox environment, stem cell population, and intercellular communication. Moreover, we have found silencing of polycomb repressive complex 2 targets and activation of pluripotency targets during LCR, which points to these transcription factors as pluripotency inducers in T. dohrnii. Accordingly, we propose these factors as key elements in the ability of T. dohrnii to undergo rejuvenation.

Calibration and Uncertainty Quantification for Single-Ended Raman-Based Distributed Temperature Sensing: Case Study in a 800 m Deep Coaxial Borehole Heat Exchanger.

Raman-based distributed temperature sensing (DTS) is a valuable tool for field testing and validating heat transfer models in borehole heat exchanger (BHE) and ground source heat pump (GSHP) applications. However, temperature uncertainty is rarely reported in the literature. In this paper, a new calibration method was proposed for single-ended DTS configurations, along with a method to remove fictitious temperature drifts due to ambient air variations. The methods were implemented for a distributed thermal response test (DTRT) case study in an 800 m deep coaxial BHE. The results show that the calibration method and temperature drift correction are robust and give adequate results, with a temperature uncertainty increasing non-linearly from about 0.4 K near the surface to about 1.7 K at 800 m. The temperature uncertainty is dominated by the uncertainty in the calibrated parameters for depths larger than 200 m. The paper also offers insights into thermal features observed during the DTRT, including a heat flux inversion along the borehole depth and the slow temperature homogenization under circulation.

Legionella pneumophila PPIase Mip Interacts with the Bacterial Proteins SspB, Lpc2061, and FlaA and Promotes Flagellation.

The peptidyl-prolyl-cis/trans-isomerase (PPIase) macrophage infectivity potentiator (Mip) contributes to the pathogenicity and fitness of L. pneumophila, the causative agent of Legionnaires' disease. Here, we identified the stringent starvation protein SspB, hypothetical protein Lpc2061, and flagellin FlaA as bacterial interaction partners of Mip. The macrolide FK506, which inhibits the PPIase activity of Mip, interfered with the binding of Lpc2061. Moreover, we demonstrated that the N-terminal dimerization region and amino acid Y185 in the C-terminal PPIase domain of Mip are required for the binding of Lpc2061 and FlaA. The modeling of the interaction partners and global docking with Mip suggested nonoverlapping binding interfaces, and a molecular dynamic simulation predicted an increased stability for the tripartite interaction of Lpc2061, Mip, and FlaA. On the functional level, we demonstrated that Mip promotes L. pneumophila flagellation, which is positively influenced by the binding of Lpc2061 and reduced by FK506. Also, L. pneumophila mutants expressing the Y185A or the monomeric Mip variant, which bind less Lpc2061, were nonmotile, were less flagellated, and yielded less FlaA when quantified. To our knowledge, this is the first report in which a PPIase and its bacterial interaction partners were demonstrated to influence flagellation.

Cellular adaptation of Clostridioides difficile to high salinity encompasses a compatible solute-responsive change in cell morphology.

Infections by the pathogenic gut bacterium Clostridioides difficile cause severe diarrhoeas up to a toxic megacolon and are currently among the major causes of lethal bacterial infections. Successful bacterial propagation in the gut is strongly associated with the adaptation to changing nutrition-caused environmental conditions; e.g. environmental salt stresses. Concentrations of 350 mM NaCl, the prevailing salinity in the colon, led to significantly reduced growth of C. difficile. Metabolomics of salt-stressed bacteria revealed a major reduction of the central energy generation pathways, including the Stickland-fermentation reactions. No obvious synthesis of compatible solutes was observed up to 24 h of growth. The ensuing limited tolerance to high salinity and absence of compatible solute synthesis might result from an evolutionary adaptation to the exclusive life of C. difficile in the mammalian gut. Addition of the compatible solutes carnitine, glycine-betaine, γ-butyrobetaine, crotonobetaine, homobetaine, proline-betaine and dimethylsulfoniopropionate restored growth (choline and proline failed) under conditions of high salinity. A bioinformatically identified OpuF-type ABC-transporter imported most of the used compatible solutes. A long-term adaptation after 48 h included a shift of the Stickland fermentation-based energy metabolism from the utilization to the accumulation of l-proline and resulted in restored growth. Surprisingly, salt stress resulted in the formation of coccoid C. difficile cells instead of the typical rod-shaped cells, a process reverted by the addition of several compatible solutes. Hence, compatible solute import via OpuF is the major immediate adaptation strategy of C. difficile to high salinity-incurred cellular stress.

Predictive Model and Risk Score for In-Hospital Mortality in Patients with All-Cause Cardiogenic Shock.

Cardiogenic shock (CS) is a condition associated with high morbidity and mortality. Our study aimed to perform a risk score for in-hospital mortality that allows for stratifying the risk of death in patients with CS.This is a retrospective analysis, which included 135 patients from a Spanish university hospital between 2011 and 2020. The Santiago Shock Score (S3) was created using clinical, analytical, and echocardiographic variables obtained at the time of admission.The in-hospital mortality rate was 41.5%, and acute coronary syndrome (ACS) was the responsible cause of shock in 60.7% of patients. Mitral regurgitation grade III-IV, age, ACS etiology, NT-proBNP, blood hemoglobin, and lactate at admission were included in the score. The S3 had good accuracy for predicting in-hospital mortality area under the receiver operating characteristic curve (AUC) 0.85 (95% confidence interval (CI) 0.78-0.90), higher than the AUC of the CardShock score, which was 0.74 (95% CI 0.66-0.83). Predictive power in a cohort of 131 patients with profound CS was similar to that of CardShock with an AUC of 0.601 (95% CI 0.496-0.706) versus an AUC of 0.558 (95% CI 0.453-0.664). Three risk categories were created according to the S3: low (scores 0-6), intermediate (scores 7-10), and high (scores 11-16) risks, with an observed mortality of 12.9%, 49.1%, and 87.5% respectively (P < 0.001).The S3 score had excellent predictive power for in-hospital mortality in patients with nonprofound CS. It could aid the initial risk stratification of patients and thus, guide treatment and clinical decision making in patients with CS.

On The Randomized Schmitter Problem.

We revisit the classical Schmitter problem in ruin theory and consider it for randomly chosen initial surplus level U. We show that the computational simplification that is obtained for exponentially distributed U allows to connect the problem to m-convex ordering, from which simple and sharp analytical bounds for the ruin probability are obtained, both for the original (but randomized) problem and for extensions involving higher moments. In addition, we show that the solution to the classical problem with deterministic initial surplus level can conveniently be approximated via Erlang(k)-distributed U for sufficiently large k, utilizing the computational advantages of the advocated randomization approach.

Plant holobiont interactions mediated by the type VI secretion system and the membrane vesicles: promising tools for a greener agriculture.

A deeper understanding of the complex relationship between plants and their microbiota is allowing researchers to appreciate a plethora of possibilities to improve crops using chemical-free alternatives based on beneficial microorganisms. An increase in crop yield from the promotion of plant growth or even simultaneous protection of the plants from the attack of phytopathogens can be achieved in the presence of different plant-associated microorganisms known as plant-growth-promoting rhizobacteria (PGPR) and biocontrol agents (BCAs), respectively. Thus, the study of the great diversity of plant-microbe and microbe-microbe interactions is an attention-grabbing topic covering studies of interactions since the plant seed and through all developmental stages, from root to shoot. The intricate communication systems that plant holobionts co-evolved has resulted in many different strategies and interplays between these organisms shaping the bacterial communities and the plant fitness simultaneously. Herein, we emphasize two understudied delivery systems existing in plant-associated bacteria: the type VI secretion system (T6SS) and the membrane vesicles with a huge potential to boost a highly demanded and necessary green agriculture.

Long term prognostic benefit of complete revascularization in elderly presenting with NSTEMI: real world evidence.

The benefit of complete revascularization in elderly patients with non-ST elevation myocardial infarction (NSTEMI), and multivessel disease remains debated (MVD). The aim of our study was to determine the current long-term prognostic benefit of complete revascularization in this population. A retrospective cohort study of 1722 consecutive elderly NSTEMI patients was performed. Among the study participants 30.4% (n = 524) were completed revascularizated and in 69.6% (n = 1198) culprit vessel only revascularization was performed. A propensity score analysis was performed and we divided the study population into two groups: complete revascularization (n = 500) and culprit vessel only revascularization (n = 500). The median follow-up was 45.7 months, the all cause mortality (44.5% vs 30.5%, p < 0.001) (HR 0.74 (0.57-0.97); p = 0.035) and cardiovascular mortality (32.6% vs 17.4%, p < 0.001) (HR = 0.67 (0.47-0.94); p = 0.021) were significantly lower in patients with complete revascularization. In our study, we observed a long-term benefit of complete revascularization in elderly NSTEMI and MVD patients. Elderly patients should also be managed according to current guidelines to improve their long-term prognosis.

Mg-protoporphyrin IX monomethyl ester cyclase from Rhodobacter capsulatus: radical SAM-dependent synthesis of the isocyclic ring of bacteriochlorophylls.

During bacteriochlorophyll a biosynthesis, the oxygen-independent conversion of Mg-protoporphyrin IX monomethyl ester (Mg-PME) to protochlorophyllide (Pchlide) is catalyzed by the anaerobic Mg-PME cyclase termed BchE. Bioinformatics analyses in combination with pigment studies of cobalamin-requiring Rhodobacter capsulatus mutants indicated an unusual radical S-adenosylmethionine (SAM) and cobalamin-dependent BchE catalysis. However, in vitro biosynthesis of the isocyclic ring moiety of bacteriochlorophyll using purified recombinant BchE has never been demonstrated. We established a spectroscopic in vitro activity assay which was subsequently validated by HPLC analyses and H218O isotope label transfer onto the carbonyl-group (C-131-oxo) of the isocyclic ring of Pchlide. The reaction product was further converted to chlorophyllide in the presence of light-dependent Pchlide reductase. BchE activity was stimulated by increasing concentrations of NADPH or SAM, and inhibited by S-adenosylhomocysteine. Subcellular fractionation experiments revealed that membrane-localized BchE requires an additional, heat-sensitive cytosolic component for activity. BchE catalysis was not sustained in chimeric experiments when a cytosolic extract from E. coli was used as a substitute. Size-fractionation of the soluble R. capsulatus fraction indicated that enzymatic activity relies on a specific component with an estimated molecular mass between 3 and 10 kDa. A structure guided site-directed mutagenesis approach was performed on the basis of a three-dimensional homology model of BchE. A newly established in vivo complementation assay was used to investigate 24 BchE mutant proteins. Potential ligands of the [4Fe-4S] cluster (Cys204, Cys208, Cys211), of SAM (Phe210, Glu308 and Lys320) and of the proposed cobalamin cofactor (Asp248, Glu249, Leu29, Thr71, Val97) were identified.

The different roles for the advanced glycation end products axis in heart failure and acute coronary syndrome settings.

AIMS: This work aimed to compare the behavior of the advanced glycation end products (AGEs) and their soluble receptor (sRAGE) in two cohorts of patients: those with heart failure (HF) and acute coronary syndrome (ACS). METHODS AND RESULTS: A unicentric observational clinical study was performed in 102 patients with ACS and 102 patients with chronic HF matched by age and gender. At inclusion, fluorescent AGEs were measured by quantitative fluorescence spectroscopy of plasma, and total sRAGE and endogenous secretory RAGE (esRAGE) levels were determined by enzyme-linked immunosorbent assay kits. A 5-year follow-up period was established for recording cardiac death (primary endpoint) and the incidence of non-fatal myocardial infarction or HF readmission (secondary endpoints). Higher glycation parameters were observed in HF patients, whereas no differences in sRAGE forms were found between HF and ACS cohorts, except for cRAGE, which was higher in HF. Associations between glycation parameters and sRAGE forms were observed in HF, but not in ACS. Differences were also evidenced in the long-term prognosis of each cohort: esRAGE showed an independent prognostic value for cardiac death or non-fatal cardiovascular events in HF, but none of the AGE-RAGE variables were predictors in ACS. CONCLUSIONS: A different role for the AGE-RAGE axis was observed in HF and ACS. All the sRAGE forms were directly related with glycation parameters in HF, but not in ACS. The independent value of the sRAGE forms on each cardiovascular disease was supported by esRAGE being an independent predictor of bad long-term prognosis only for HF.

Exploiting the natural poly(3-hydroxyalkanoates) production capacity of Antarctic Pseudomonas strains: from unique phenotypes to novel biopolymers.

Extreme environments are a unique source of microorganisms encoding metabolic capacities that remain largely unexplored. In this work, we isolated two Antarctic bacterial strains able to produce poly(3-hydroxyalkanoates) (PHAs), which were classified after 16S rRNA analysis as Pseudomonas sp. MPC5 and MPC6. The MPC6 strain presented nearly the same specific growth rate whether subjected to a temperature of 4 °C 0.18 (1/h) or 30 °C 0.2 (1/h) on glycerol. Both Pseudomonas strains produced high levels of PHAs and exopolysaccharides from glycerol at 4 °C and 30 °C in batch cultures, an attribute that has not been previously described for bacteria of this genus. The MPC5 strain produced the distinctive medium-chain-length-PHA whereas Pseudomonas sp. MPC6 synthesized a novel polyoxoester composed of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3-hydroxydecanoate-co-3-hydroxydodecanoate). Batch bioreactor production of PHAs in MPC6 resulted in a titer of 2.6 (g/L) and 1.3 (g/L), accumulating 47.3% and 34.5% of the cell dry mass as PHA, at 30 and 4 °C, respectively. This study paves the way for using Antarctic Pseudomonas strains for biosynthesizing novel PHAs from low-cost substrates such as glycerol and the possibility to carry out the bioconversion process for biopolymer synthesis without the need for temperature control.

Relevance of Dementia in Atrial Fibrillation Patients within a Specific European Health Care Area.

INTRODUCTION: Atrial fibrillation might increase the risk of dementia. We aim to test the hypothesis that dementia could reclassify the actual risk of stroke and death predicted by the CHA2DS2-VASc in patients with atrial fibrillation (AF). METHODS: A prospective study performed in a specific health care area. RESULTS: From our health care area (n = 348,985), throughout 2013, AF was codified in 7,990 (2.08%). Mean age was 76.83 ± 10.5, mean CHA2DS2-VASc = 3.5, 4,056 (50.8%) were females and 287 (3.6%) were diagnosed to have dementia. Patients with dementia were older and presented a higher rate of all the components of the CHA2DS2-VASc-expect vasculopathy. Differences in overall mortality were observed but not in stroke and haemorrhagic events. After propensity score matched analysis, dementia was independently associated with all-cause mortality. Addition of dementia to CHA2DS2-VASc reclassified 7.7 and 16.6% of the cohort with regard to thromboembolic events and death risk respectively. CONCLUSIONS: Patients with dementia presented a more adverse risk profile, with significant differences in all-cause mortality.

Pharmacological Potential of Phylogenetically Diverse Actinobacteria Isolated from Deep-Sea Coral Ecosystems of the Submarine Avilés Canyon in the Cantabrian Sea.

Marine Actinobacteria are emerging as an unexplored source for natural product discovery. Eighty-seven deep-sea coral reef invertebrates were collected during an oceanographic expedition at the submarine Avilés Canyon (Asturias, Spain) in a range of 1500 to 4700 m depth. From these, 18 cultivable bioactive Actinobacteria were isolated, mainly from corals, phylum Cnidaria, and some specimens of phyla Echinodermata, Porifera, Annelida, Arthropoda, Mollusca and Sipuncula. As determined by 16S rRNA sequencing and phylogenetic analyses, all isolates belong to the phylum Actinobacteria, mainly to the Streptomyces genus and also to Micromonospora, Pseudonocardia and Myceligenerans. Production of bioactive compounds of pharmacological interest was investigated by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) techniques and subsequent database comparison. Results reveal that deep-sea isolated Actinobacteria display a wide repertoire of secondary metabolite production with a high chemical diversity. Most identified products (both diffusible and volatiles) are known by their contrasted antibiotic or antitumor activities. Bioassays with ethyl acetate extracts from isolates displayed strong antibiotic activities against a panel of important resistant clinical pathogens, including Gram-positive and Gram-negative bacteria, as well as fungi, all of them isolated at two main hospitals (HUCA and Cabueñes) from the same geographical region. The identity of the active extracts components of these producing Actinobacteria is currently being investigated, given its potential for the discovery of pharmaceuticals and other products of biotechnological interest.

Paulomycin G, a New Natural Product with Cytotoxic Activity against Tumor Cell Lines Produced by Deep-Sea Sediment Derived Micromonospora matsumotoense M-412 from the Avilés Canyon in the Cantabrian Sea.

The present article describes a structurally novel natural product of the paulomycin family, designated as paulomycin G (1), obtained from the marine strain Micromonospora matsumotoense M-412, isolated from Cantabrian Sea sediments collected at 2000 m depth during an oceanographic expedition to the submarine Avilés Canyon. Paulomycin G is structurally unique since-to our knowledge-it is the first member of the paulomycin family of antibiotics lacking the paulomycose moiety. It is also the smallest bioactive paulomycin reported. Its structure was determined using HRMS and 1D and 2D NMR spectroscopy. This novel natural product displays strong cytotoxic activities against different human tumour cell lines, such as pancreatic adenocarcinoma (MiaPaca_2), breast adenocarcinoma (MCF-7), and hepatocellular carcinoma (HepG2). The compound did not show any significant bioactivity when tested against a panel of bacterial and fungal pathogens.

Protein Network of the Pseudomonas aeruginosa Denitrification Apparatus.

UNLABELLED: Oxidative phosphorylation using multiple-component, membrane-associated protein complexes is the most effective way for a cell to generate energy. Here, we systematically investigated the multiple protein-protein interactions of the denitrification apparatus of the pathogenic bacterium Pseudomonas aeruginosa During denitrification, nitrate (Nar), nitrite (Nir), nitric oxide (Nor), and nitrous oxide (Nos) reductases catalyze the reaction cascade of NO(3-)→ NO(2-)→ NO → N2O → N2 Genetic experiments suggested that the nitric oxide reductase NorBC and the regulatory protein NosR are the nucleus of the denitrification protein network. We utilized membrane interactomics in combination with electron microscopy colocalization studies to elucidate the corresponding protein-protein interactions. The integral membrane proteins NorC, NorB, and NosR form the core assembly platform that binds the nitrate reductase NarGHI and the periplasmic nitrite reductase NirS via its maturation factor NirF. The periplasmic nitrous oxide reductase NosZ is linked via NosR. The nitrate transporter NarK2, the nitrate regulatory system NarXL, various nitrite reductase maturation proteins, NirEJMNQ, and the Nos assembly lipoproteins NosFL were also found to be attached. A number of proteins associated with energy generation, including electron-donating dehydrogenases, the complete ATP synthase, almost all enzymes of the tricarboxylic acid (TCA) cycle, and the Sec system of protein transport, among many other proteins, were found to interact with the denitrification proteins. This deduced nitrate respirasome is presumably only one part of an extensive cytoplasmic membrane-anchored protein network connecting cytoplasmic, inner membrane, and periplasmic proteins to mediate key activities occurring at the barrier/interface between the cytoplasm and the external environment. IMPORTANCE: The processes of cellular energy generation are catalyzed by large multiprotein enzyme complexes. The molecular basis for the interaction of these complexes is poorly understood. We employed membrane interactomics and electron microscopy to determine the protein-protein interactions involved. The well-investigated enzyme complexes of denitrification of the pathogenic bacterium Pseudomonas aeruginosa served as a model. Denitrification is one essential step of the universal N cycle and provides the bacterium with an effective alternative to oxygen respiration. This process allows the bacterium to form biofilms, which create low-oxygen habitats and which are a key in the infection mechanism. Our results provide new insights into the molecular basis of respiration, as well as opening a new window into the infection strategies of this pathogen.

Three Pseudomonas putida FNR Family Proteins with Different Sensitivities to O2.

The Escherichia coli fumarate-nitrate reduction regulator (FNR) protein is the paradigm for bacterial O2-sensing transcription factors. However, unlike E. coli, some bacterial species possess multiple FNR proteins that presumably have evolved to fulfill distinct roles. Here, three FNR proteins (ANR, PP_3233, and PP_3287) from a single bacterial species, Pseudomonas putida KT2440, have been analyzed. Under anaerobic conditions, all three proteins had spectral properties resembling those of [4Fe-4S] proteins. The reactivity of the ANR [4Fe-4S] cluster with O2 was similar to that of E. coli FNR, and during conversion to the apo-protein, via a [2Fe-2S] intermediate, cluster sulfur was retained. Like ANR, reconstituted PP_3233 and PP_3287 were converted to [2Fe-2S] forms when exposed to O2, but their [4Fe-4S] clusters reacted more slowly. Transcription from an FNR-dependent promoter with a consensus FNR-binding site in P. putida and E. coli strains expressing only one FNR protein was consistent with the in vitro responses to O2. Taken together, the experimental results suggest that the local environments of the iron-sulfur clusters in the different P. putida FNR proteins influence their reactivity with O2, such that ANR resembles E. coli FNR and is highly responsive to low concentrations of O2, whereas PP_3233 and PP_3287 have evolved to be less sensitive to O2.

Glucose and Inflammatory Cells Decrease Adiponectin in Epicardial Adipose Tissue Cells: Paracrine Consequences on Vascular Endothelium.

Epicardial adipose tissue (EAT) is a source of energy for heart that expresses the insulin-sensitizer, anti-inflammatory and anti-atherogenic protein, adiponectin. But, in coronary artery disease, adiponectin production declines. Our objective was to determine its regulation by glucose and inflammation in stromal cells from EAT and subcutaneous adipose tissue (SAT) and its paracrine effect on endothelial cells. Stromal cells of EAT and SAT were obtained from patients who underwent cardiac surgery. Adipogenesis was induced at 117, 200, or 295 mg/dl glucose, with or without macrophage-conditioned medium (MCM). Expression of adiponectin, GLUT-4 and the insulin receptor was analyzed by real-time PCR. The paracrine effect of stromal cells was determined in co-cultures with endothelial cells, by exposing them to high glucose and/or MCM, and, additionally, to leukocyte-conditioned medium from patients with myocardial infarction. The endothelial response was determined by analyzing vascular adhesion molecule expression. Our results showed a U-shaped dose-response curve of glucose on adiponectin in EAT, but not in SAT stromal cells. Conversely, MCM reduced the adipogenesis-induced adiponectin expression of EAT stromal cells. The presence of EAT stromal increased the inflammatory molecules of endothelial cells. This deleterious effect was emphasized in the presence of inflammatory cell-conditioned medium from patients with myocardial infarction. Thus, high glucose and inflammatory cells reduced adipogenesis-induced adiponectin expression of EAT stromal cells, which induced an inflammatory paracrine process in endothelial cells. This inflammatory effect was lower in presence of mature adipocytes, producers of adiponectin. These results contribute to understanding the role of EAT dysfunction on coronary atherosclerosis progression.

Body size-based trophic structure of a deep marine ecosystem.

Nitrogen stable isotope ratios (δ15N) and body size were used to describe the size-based trophic structure of a deep-sea ecosystem, the Avilés submarine Canyon (Cantabrian Sea, Southern Bay of Biscay). We analyzed δ15N of specimens collected on a seasonal basis (March 2012, October 2012, and May 2013), from a variety of zones (benthic, pelagic), taxa (from zooplankton through invertebrates and fishes to giant squids and cetaceans), or depths (from surface to 4700 m) that spanned nine orders of magnitude in body mass. Our data reveal a strong linear dependence of trophic level on body size when data were considered either individually, aggregated into taxonomical categories, or binned into size classes. The three approaches render similar results that were not significantly different and yielded predator:prey body mass ratios (PPMR) of 1156:1, 3792:1 and 2718:1, respectively. Thus, our data represent unequivocal evidence of interspecific, size-based trophic structure of a whole ecosystem based on taxonomic/functional categories. We studied the variability in δ15N not explained by body mass (W) using linear mixed modeling and found that the δ15N vs. log10 W relationship holds for both pelagic and benthic systems, with benthic organisms isotopically enriched relative to pelagic organisms of the same size. However there is a marked seasonal variation potentially related to the recycling state of the system.

Atmospheric Dispersal of Bioactive Streptomyces albidoflavus Strains Among Terrestrial and Marine Environments.

Members of the Streptomyces albidoflavus clade, identified by 16S rRNA sequencing and phylogenetic analyses, are widespread among predominant terrestrial lichens (Flavoparmelia caperata and Xanthoria parietina) and diverse intertidal and subtidal marine macroalgae, brown red and green (Phylum Heterokontophyta, Rhodophyta, and Chlorophyta) from the Cantabrian Cornice. In addition to these terrestrial and coastal temperate habitats, similar strains were also found to colonize deep-sea ecosystems and were isolated mainly from gorgonian and solitary corals and other invertebrates (Phylum Cnidaria, Annelida, Echinodermata, Arthropoda, and Porifera) living up to 4700-m depth and at a temperature of 2-4 °C in the submarine Avilés Canyon. Similar strains have been also repeatedly isolated from atmospheric precipitations (rain drops, snow, and hailstone) collected in the same area throughout a year observation time. These ubiquitous strains were found to be halotolerant, psychrotolerant, and barotolerant. Bioactive compounds with diverse antibiotic and cytotoxic activities produced by these strains were identified by high-performance liquid chromatography (HPLC) and database comparison. These include antibacterials (paulomycins A and B), antifungals (maltophilins), antifungals displaying also cytotoxic activities (antimycins and 6-epialteramides), and the antitumor compound fredericamycin. A hypothetical dispersion model is here proposed to explain the biogeographical distribution of S. albidoflavus strains in terrestrial, marine, and atmospheric environments.

A Periplasmic Complex of the Nitrite Reductase NirS, the Chaperone DnaK, and the Flagellum Protein FliC Is Essential for Flagellum Assembly and Motility in Pseudomonas aeruginosa.

UNLABELLED: Pseudomonas aeruginosa is a ubiquitously occurring environmental bacterium and opportunistic pathogen responsible for various acute and chronic infections. Obviously, anaerobic energy generation via denitrification contributes to its ecological success. To investigate the structural basis for the interconnection of the denitrification machinery to other essential cellular processes, we have sought to identify the protein interaction partners of the denitrification enzyme nitrite reductase NirS in the periplasm. We employed NirS as an affinity-purifiable bait to identify interacting proteins in vivo. Results obtained revealed that both the flagellar structural protein FliC and the protein chaperone DnaK form a complex with NirS in the periplasm. The interacting domains of NirS and FliC were tentatively identified. The NirS-interacting stretch of amino acids lies within its cytochrome c domain. Motility assays and ultrastructure analyses revealed that a nirS mutant was defective in the formation of flagella and correspondingly in swimming motility. In contrast, the fliC mutant revealed an intact denitrification pathway. However, deletion of the nirF gene, coding for a heme d1 biosynthetic enzyme, which leads to catalytically inactive NirS, did not abolish swimming ability. This pointed to a structural function for the NirS protein. FliC and NirS were found colocalized with DnaK at the cell surface of P. aeruginosa. A function of the detected periplasmic NirS-DnaK-FliC complex in flagellum formation and motility was concluded and discussed. IMPORTANCE: Physiological functions in Gram-negative bacteria are connected with the cellular compartment of the periplasm and its membranes. Central enzymatic steps of anaerobic energy generation and the motility mediated by flagellar activity use these cellular structures in addition to multiple other processes. Almost nothing is known about the protein network functionally connecting these processes in the periplasm. Here, we demonstrate the existence of a ternary complex consisting of the denitrifying enzyme NirS, the chaperone DnaK, and the flagellar protein FliC in the periplasm of the pathogenic bacterium P. aeruginosa. The dependence of flagellum formation and motility on the presence of an intact NirS was shown, structurally connecting both cellular processes, which are important for biofilm formation and pathogenicity of the bacterium.