East Asian summer monsoon delivers large abundances of very-short-lived organic chlorine substances to the lower stratosphere.

Deep convection in the Asian summer monsoon is a significant transport process for lifting pollutants from the planetary boundary layer to the tropopause level. This process enables efficient injection into the stratosphere of reactive species such as chlorinated very-short-lived substances (Cl-VSLSs) that deplete ozone. Past studies of convective transport associated with the Asian summer monsoon have focused mostly on the south Asian summer monsoon. Airborne observations reported in this work identify the East Asian summer monsoon convection as an effective transport pathway that carried record-breaking levels of ozone-depleting Cl-VSLSs (mean organic chlorine from these VSLSs ~500 ppt) to the base of the stratosphere. These unique observations show total organic chlorine from VSLSs in the lower stratosphere over the Asian monsoon tropopause to be more than twice that previously reported over the tropical tropopause. Considering the recently observed increase in Cl-VSLS emissions and the ongoing strengthening of the East Asian summer monsoon under global warming, our results highlight that a reevaluation of the contribution of Cl-VSLS injection via the Asian monsoon to the total stratospheric chlorine budget is warranted.

The alternative sigma factor RpoS regulates Pseudomonas aeruginosa quorum sensing response by repressing the pqsABCDE operon and activating vfr.

Pseudomonas aeruginosa is an important opportunistic pathogen. Several of its virulence-related processes, including the synthesis of pyocyanin (PYO) and biofilm formation, are controlled by quorum sensing (QS). It has been shown that the alternative sigma factor RpoS regulates QS through the reduction of lasR and rhlR transcription (encoding QS regulators). However, paradoxically, the absence of RpoS increases PYO production and biofilm development (that are RhlR dependent) by unknown mechanisms. Here, we show that RpoS represses pqsE transcription, which impacts the stability and activity of RhlR. In the absence of RpoS, rhlR transcript levels are reduced but not the RhlR protein concentration, presumably by its stabilization by PqsE, whose expression is increased. We also report that PYO synthesis and the expression of pqsE and phzA1B1C1D1E1F1G1 operon exhibit the same pattern at different RpoS concentrations, suggesting that the RpoS-dependent PYO production is due to its ability to modify PqsE concentration, which in turn modulates the activation of the phzA1 promoter by RhlR. Finally, we demonstrate that RpoS favors the expression of Vfr, which activates the transcription of lasR and rhlR. Our study contributes to the understanding of how RpoS modulates the QS response in P. aeruginosa, exerting both negative and positive regulation.

Defining the regulatory mechanisms of sigma factor RpoS degradation in Azotobacter vinelandii and Pseudomonas aeruginosa.

In several Gram-negative bacteria, the general stress response is mediated by the alternative sigma factor RpoS, a subunit of RNA polymerase that confers promoter specificity. In Escherichia coli, regulation of protein levels of RpoS involves the adaptor protein RssB, which binds RpoS for presenting it to the ClpXP protease for its degradation. However, in species from the Pseudomonadaceae family, RpoS is also degraded by ClpXP, but an adaptor has not been experimentally demonstrated. Here, we investigated the role of an E. coli RssB-like protein in two representative Pseudomonadaceae species such as Azotobacter vinelandii and Pseudomonas aeruginosa. In these bacteria, inactivation of the rssB gene increased the levels and stability of RpoS during exponential growth. Downstream of rssB lies a gene that encodes a protein annotated as an anti-sigma factor antagonist (rssC). However, inactivation of rssC in both A. vinelandii and P. aeruginosa also increased the RpoS protein levels, suggesting that RssB and RssC work together to control RpoS degradation. Furthermore, we identified an in vivo interaction between RssB and RpoS only in the presence of RssC using a bacterial three-hybrid system. We propose that both RssB and RssC are necessary for the ClpXP-dependent RpoS degradation during exponential growth in two species of the Pseudomonadaceae family.

Pseudomonas aeruginosa strains belonging to phylogroup 3 frequently exhibit an atypical quorum sensing response: the case of MAZ105, a tomato rhizosphere isolate.

Pseudomonas aeruginosa is a widespread γ-proteobacterium and an important opportunistic pathogen. The genetically diverse P. aeruginosa phylogroup 3 strains are characterized by producing the pore-forming ExlA toxin and by their lack of a type III secretion system. However, like all strains of this species, they produce several virulence-associated traits, such as elastase, rhamnolipids and pyocyanin, which are regulated by quorum sensing (QS). The P. aeruginosa QS response comprises three systems (Las, Rhl and Pqs, respectively) that hierarchically regulate these virulence factors. The Pqs QS system is composed of the PqsR transcriptional factor, which, coupled with the alkyl-quinolones HHQ or PQS, activates the transcription of the pqsABCDE operon. The products of the first four genes of this operon produce HHQ, which is then converted to PQS by PqsH, while PqsE forms a complex with RhlR and stabilizes it. In this study we report that mutations affecting the Pqs system are particularly common in phylogroup 3 strains. To better understand QS in phylogroup 3 strains we studied strain MAZ105 isolated from tomato rhizosphere and showed that it contains mutations in the central QS transcriptional regulator, LasR, and in the gene encoding the PqsA enzyme involved in the synthesis of PQS. However, it can still produce QS-regulated virulence factors and is virulent in Galleria mellonella and mildly pathogenic in the mouse abscess/necrosis model; our results show that this may be due to the expression of pqsE from a different PqsR-independent promoter than the pqsA promoter. Our results indicate that using anti-virulence therapy based on targeting the PQS system will not be effective against infections by P. aeruginosa phylogroup 3 strains.

Unraveling the regulation of pyocyanin synthesis by RsmA through MvaU and RpoS in Pseudomonas aeruginosa ID4365.

Pyocyanin is a phenazine with redox activity produced by Pseudomonas aeruginosa that is harmful to other bacteria and eukaryotic organisms by generating reactive oxygen species. Gene regulation of pyocyanin synthesis has been addressed in the PAO1 and PA14 strains and involves the three-quorum sensing systems Las, Rhl, and Pqs; the regulators RsaL, MvaU, and RpoS, and the posttranscriptional Rsm system, among others. Here, we determined how RsmA regulates pyocyanin synthesis in P. aeruginosa ID4365, an overproducer strain. We found that, in the protease peptone glucose ammonium salts medium, rsmA inactivation increases pyocyanin production compared with the wild-type strains ID4365, PAO, and PA14. We showed that RsmA regulates inversely the expression of both phz operons involved in pyocyanin synthesis; particularly the phz2 operon is positively regulated at the transcriptional level indirectly through MvaU. In addition, we found that the phz1 operon contributes mainly to pyocyanin synthesis and that RsmA negatively regulates phzM and phzS expression. Finally, we showed that translation of the sigma factor RpoS is positively regulated by RsmA, and the expression of rpoS under an independent promoter decreases pyocyanin production in the IDrsmA strain. These results indicate that RsmA regulates not only the genes for pyocyanin production but also their regulators.

Biotechnological applications of marine bacteria in bioremediation of environments polluted with hydrocarbons and plastics.

Marine ecosystems are some of the most adverse environments on Earth and contain a considerable portion of the global bacterial population, and some of these bacterial species play pivotal roles in several biogeochemical cycles. Marine bacteria have developed different molecular mechanisms to address fluctuating environmental conditions, such as changes in nutrient availability, salinity, temperature, pH, and pressure, making them attractive for use in diverse biotechnology applications. Although more than 99% of marine bacteria cannot be cultivated with traditional microbiological techniques, several species have been successfully isolated and grown in the laboratory, facilitating investigations of their biotechnological potential. Some of these applications may contribute to addressing some current global problems, such as environmental contamination by hydrocarbons and synthetic plastics. In this review, we first summarize and analyze recently published information about marine bacterial diversity. Then, we discuss new literature regarding the isolation and characterization of marine bacterial strains able to degrade hydrocarbons and petroleum-based plastics, and species able to produce biosurfactants. We also describe some current limitations for the implementation of these biotechnological tools, but also we suggest some strategies that may contribute to overcoming them. KEY POINTS: • Marine bacteria have a great metabolic capacity to degrade hydrocarbons in harsh conditions. • Marine environments are an important source of new bacterial plastic-degrading enzymes. • Secondary metabolites from marine bacteria have diverse potential applications in biotechnology.

Real-world prevalence and consequences of potential drug-drug interactions in the first-wave COVID-19 treatments.

WHAT IS KNOWN AND OBJECTIVE: Initial treatment recommendations of COVID-19 were based on the use of antimicrobial drugs and immunomodulators. Although information on drug interactions was available for other pathologies, there was little evidence in the treatment of COVID-19. The objective of this study was to analyse the potential drug-drug interactions (pDDIs) derived from the medication used in COVID-19 patients in the first pandemic wave and to evaluate the real consequences of such interactions in clinical practice. METHODS: Cohort, retrospective and single-centre study carried out in a third-level hospital. Adult patients, admitted with suspected COVID-19, that received at least one dose of hydroxychloroquine, lopinavir/ritonavir, interferon beta 1-b or tocilizumab and with any pDDIs according to "Liverpool Drug Interaction Group" between March and May 2020 were included. The possible consequences of pDDIs at the QTc interval level or any other adverse event according to the patient's medical record were analysed. A descriptive analysis was carried out to assess possible factors that may affect the QTc interval prolongation. RESULTS AND DISCUSSION: Two hundred and eighteen (62.3%) patients of a total of 350 patients admitted with COVID-19 had at least one pDDI. There were 598 pDDIs. Thirty-eight pDDIs (6.3%) were categorized as not recommended or contraindicated. The mean value difference between baseline and pDDI posterior ECG was 412.3 ms ± 25.8 ms vs. 426.3 ms ± 26.7 ms; p < 0.001. Seven patients (5.7%) had a clinically significant alteration of QTc. A total of 44 non-cardiological events (7.3%) with a possible connection to a pDDI were detected. WHAT IS NEW AND CONCLUSION: The number of pDDIs in patients admitted for COVID-19 in the first pandemic wave was remarkably high. However, clinical consequences occurred in a low percentage of patients. Interactions involving medications that would be contraindicated for concomitant administration are rare. Knowledge of these pDDIs and their consequences could help to establish appropriate therapeutic strategies in patients with COVID-19 or other diseases with these treatments.

Outer membrane protein I is associated with poly-ß-hydroxybutyrate granules and is necessary for optimal polymer accumulation in Azotobacter vinelandii on solid medium.

Azotobacter vinelandii is a soil bacterium that is able to synthesize poly-ß-hydroxybutyrate (PHB), a polymer used to produce biodegradable plastic. PHB is stored in the cytoplasm as granules surrounded by several proteins such as the major phasin PhbP, PHB synthase and PHB depolymerase, among others. Many studies have reported the presence of membrane proteins on PHB granules due to contamination during the polymer extraction procedures. Previously, the outer membrane protein I (OprI) was detected on the polymer granules in A. vinelandii. In this study, by using random transposon mutagenesis, we identified that a mutation in the oprI gene diminished PHB accumulation in A. vinelandii on solid medium. Electron microscopy confirmed the low polymer production by the oprI mutant. Analysis of PHB granules by Tricine-SDS-PAGE revealed that the absence of OprI affected the protein profile of the granules, suggesting that OprI could have a structural role in A. vinelandii. Thus, some membrane proteins on PHB granules may not be artefacts as previously described.

Unphosphorylated EIIANtr induces ClpAP-mediated degradation of RpoS in Azotobacter vinelandii.

The nitrogen-related phosphotransferase system (PTSNtr ) is composed of the EINtr , NPr and EIIANtr proteins that form a phosphorylation cascade from phosphoenolpyruvate. PTSNtr is a global regulatory system present in most Gram-negative bacteria that controls some pivotal processes such as potassium and phosphate homeostasis, virulence, nitrogen fixation and ABC transport activation. In the soil bacterium Azotobacter vinelandii, unphosphorylated EIIANtr negatively regulates the expression of genes related to the synthesis of the bioplastic polyester poly-ß-hydroxybutyrate (PHB) and cyst-specific lipids alkylresorcinols (ARs). The mechanism by which EIIANtr controls gene expression in A. vinelandii is not known. Here, we show that, in presence of unphosphorylated EIIANtr , the stability of the stationary phase sigma factor RpoS, which is necessary for transcriptional activation of PHB and ARs synthesis related genes, is reduced, and that the inactivation of genes coding for ClpAP protease complex in strains that carry unphosphorylated EIIANtr , restored the levels and in vivo stability of RpoS, as well as the synthesis of PHB and ARs. Taken together, our results reveal a novel mechanism, by which EIIANtr globally controls gene expression in A. vinelandii, where the unphosphorylated EIIANtr induces the degradation of RpoS by the proteolytic complex ClpAP.

Two-component system CbrA/CbrB controls alginate production in Azotobacter vinelandii.

Azotobacter vinelandii, belonging to the Pseudomonadaceae family, is a free-living bacterium that has been considered to be a good source for the production of bacterial polymers such as alginate. In A. vinelandii the synthesis of this polymer is regulated by the Gac/Rsm post-transcriptional regulatory system, in which the RsmA protein binds to the mRNA of the biosynthetic algD gene, inhibiting translation. In several Pseudomonas spp. the two-component system CbrA/CbrB has been described to control a variety of metabolic and behavioural traits needed for adaptation to changing environmental conditions. In this work, we show that the A. vinelandii CbrA/CbrB two-component system negatively affects alginate synthesis, a function that has not been described in Pseudomonas aeruginosa or any other Pseudomonas species. CbrA/CbrB was found to control the expression of some alginate biosynthetic genes, mainly algD translation. In agreement with this result, the CbrA/CbrB system was necessary for optimal rsmA expression levels. CbrA/CbrB was also required for maximum accumulation of the sigma factor RpoS. This last effect could explain the positive effect of CbrA/CbrB on rsmA expression, as we also showed that one of the promoters driving rsmA transcription was RpoS-dependent. However, although inactivation of rpoS increased alginate production by almost 100 %, a cbrA mutation increased the synthesis of this polymer by up to 500 %, implying the existence of additional CbrA/CbrB regulatory pathways for the control of alginate production. The control exerted by CbrA/CbrB on the expression of the RsmA protein indicates the central role of this system in regulating carbon metabolism in A. vinelandii.

Posttranscriptional regulation of PhbR, the transcriptional activator of polyhydroxybutyrate synthesis, by iron and the sRNA ArrF in Azotobacter vinelandii.

Azotobacter vinelandii is a Gram-negative bacterium able to synthesize poly-ß-hydroxybutyrate (PHB), a biodegradable plastic of industrial interest. The phbBAC operon encodes the enzymes of PHB synthesis and is activated by the transcriptional regulator PhbR and the sigma factor RpoS. Iron limitation has been previously reported to increase PHB accumulation in A. vinelandii; however, the mechanism by which iron controls PHB synthesis is unknown. Under iron starvation in Escherichia coli, the RyhB sRNA modulates the translation of genes involved in iron homeostasis. ArrF is the RyhB analogue in A. vinelandii and similarly increases in quantity during Fe(2+) depletion. In this study, we evaluate the effect of iron and ArrF on PHB accumulation, and on phbR and phbBAC expression in A. vinelandii strain UW136. Using transcriptional and translational fusions of phbR and phbB with gusA reporter gene, we found that iron limitation increased the expression of phbBAC at the transcriptional level and posttranscriptionally increased the expression of phbR. We also found that the ArrF sRNA is a positive regulator of phbR expression at the posttranscriptional level. Collectively, these data suggest that iron limitation increases the translation of phbR through ArrF.

XTT assay for detection of bacterial metabolic activity in water-based polyester polyurethane.

Cellular metabolic activity can be detected by tetrazolium-based colorimetric assays, which rely on dehydrogenase enzymes from living cells to reduce tetrazolium compounds into colored formazan products. Although these methods have been used in different fields of microbiology, their application to the detection of bacteria with plastic-degrading activity has not been well documented. Here, we report a microplate-adapted method for the detection of bacteria metabolically active on the commercial polyester polyurethane (PU) Impranil®DLN using the tetrazolium salt 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT). Bacterial cells that are active on PU reduce XTT to a water-soluble orange dye, which can be quantitatively measured using a microplate reader. We used the Pseudomonas putida KT2440 strain as a study model. Its metabolic activity on Impranil detected by our novel method was further verified by Fourier-transform infrared spectroscopy (FTIR) analyses. Measurements of the absorbance of reduced XTT at 470 nm in microplate wells were not affected by the colloidal properties of Impranil or cell density. In summary, we provide here an easy and high-throughput method for screening bacteria active on PU that can be adapted to other plastic substrates.

A Novel Thermo-Alkaline Stable GDSL/SGNH Esterase with Broad Substrate Specificity from a Deep-Sea Pseudomonas sp.

Marine environments harbor a plethora of microorganisms that represent a valuable source of new biomolecules of biotechnological interest. In particular, enzymes from marine bacteria exhibit unique properties due to their high catalytic activity under various stressful and fluctuating conditions, such as temperature, pH, and salinity, fluctuations which are common during several industrial processes. In this study, we report a new esterase (EstGoM) from a marine Pseudomonas sp. isolated at a depth of 1000 m in the Gulf of Mexico. Bioinformatic analyses revealed that EstGoM is an autotransporter esterase (type Va) and belongs to the lipolytic family II, forming a new subgroup. The purified recombinant EstGoM, with a molecular mass of 67.4 kDa, showed the highest hydrolytic activity with p-nitrophenyl octanoate (p-NP C8), although it was also active against p-NP C4, C5, C10, and C12. The optimum pH and temperature for EstGoM were 9 and 60 °C, respectively, but it retained more than 50% of its activity over the pH range of 7-11 and temperature range of 10-75 °C. In addition, EstGoM was tolerant of up to 1 M NaCl and resistant to the presence of several metal ions, detergents, and chemical reagents, such as EDTA and ß-mercaptoethanol. The enzymatic properties of EstGoM make it a potential candidate for several industrial applications.

Physicochemical Stability of Hospital Parenteral Nutrition Solutions: Effect of Changes in Composition and Storage Protocol.

(1) Background: Parenteral nutrition (PN) is a technique used for the administration of nutrients to patients for whom traditional routes cannot be used. It is performed using solutions with extremely complex compositions, which can give rise to a large number of interactions. These interactions can impact their stability and put the patient's life at risk. The aim of this study is to determine how changes in composition and storage protocol affect the stability of NP solutions. (2) Methods: Twenty-three samples were prepared according to routine clinical practice, with modifications to the concentration of some components. The samples were stored at room temperature (RT) and refrigerated (4 °C). Measurements of the droplet diameter, pH, density and viscosity were performed for both storage protocols on days 1, 3, 10 and 14. (3) Results: The samples with the lowest concentration of lipids (PN13-17) and proteins (PN18-22) showed a larger droplet diameter than the rest of the samples throughout the experiments. The USP limits were exceeded for some of the measurements of these sample groups. The pH density and viscosity remained relatively constant under the conditions studied. (4) Conclusions: The PN samples were considered stable and safe for administration under real-world conditions, but the samples with the lowest concentrations of lipids and proteins showed a tendency towards emulsion instability.

Electron Microscopy for the Stability Assessment of Parenteral Nutrition Admixtures: Focus on Precipitation.

(1) Background: parenteral nutrition (PN) is indispensable for patients unable to receive oral or enteral feeding. However, the complexity of PN solutions presents challenges regarding stability and compatibility. Precipitation reactions may occur. The most frequent is the formation of calcium phosphate (Ca-P). The different factors influencing these reactions must be considered to ensure patient safety. (2) Methods: eight paediatric PN solutions were prepared, following standard protocols. Samples were stored at room temperature and in a refrigerator. Electron microscopy, coupled with energy dispersive X-ray spectroscopy (EDS), was employed. Precipitates were analysed for composition and morphology. (3) Results: precipitates were observed in all samples, even at day 0. Crystalline structures, predominantly composed of calcium or magnesium, sometimes associated with chlorine or phosphorus, were detected. Additionally, amorphous precipitates, contained heterogeneous compositions, including unexpected elements, were identified. (4) Conclusions: various precipitates, primarily calcium- or magnesium-based, can form in PN solutions, although it is not expected that they can form under the real conditions of use. Calcium oxalate precipitation has been characterised, but the use of organic calcium and phosphate salts appears to mitigate calcium phosphate precipitation. Electron microscopy provides interesting results on NP precipitation, but sample preparation may present technical limitations that affect the interpretation of the results.

Evaluation of the Stability of Newborn Hospital Parenteral Nutrition Solutions.

(1) Background: parenteral nutrition (PN) solutions are an extremely complex mixture. It is composed of a multitude of chemical elements that can give rise to a large number of interactions that condition its stability and safety. The aim of this study was to evaluate the stability of PN solutions for preterm infants. (2) Methods: eight samples were prepared according to the protocol for prescribing PN in preterm infants. Samples PN1-PN7 had the normal progression of macronutrients and standard amounts of micronutrients for a 1 kg preterm infant. The PN8 sample had a high concentration of electrolytes, with the idea of forcing stability limits. Samples were stored both at room temperature and under refrigeration. Measurements of globule size, pH, density, and viscosity were performed in both storage protocols on different days after processing. (3) Results: the changes in the composition of the samples did not affect the evolution of the stability at the different measurement times and temperatures. Viscosity was affected by the compositional changes made in the PN samples, but no alterations due to time or temperature were observed. Density and pH remained stable, without significant changes due to time, storage temperature, or different composition. (4) Conclusion: all samples remained stable during the study period and did not undergo significant alterations due to compositional changes or different experimental conditions.

Hypothesized role of pregnancy hormones on HER2+ breast tumor development.

Breast cancer incidence rates have declined among older but not younger women; the latter are more likely to be diagnosed with breast cancers carrying a poor prognosis. Epidemiological evidence supports an increase in breast cancer incidence following pregnancy with risk elevated as much as 10 years post-partum. We investigated the association between years since last full-term pregnancy at the time of diagnosis (≤10 or >10 years) and breast tumor subtype in a case series of premenopausal Hispanic women (n = 627). Participants were recruited in the United States, Mexico, and Spain. Cases with known estrogen receptor (ER), progesterone receptor (PR), and HER2 status, with one or more full-term pregnancies ≥1 year prior to diagnosis were eligible for this analysis. Cases were classified into three tumor subtypes according to hormone receptor (HR+ = ER+ and/or PR+; HR- = ER- and PR-) expression and HER2 status: HR+/HER2-, HER2+ (regardless of HR), and triple negative breast cancer. Case-only odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated for HER2+ tumors in reference to HR+/HER2- tumors. Participants were pooled in a mixed-effects logistic regression model with years since pregnancy as a fixed effect and study site as a random effect. When compared to HR+/HER2- cases, women with HER2+ tumors were more likely be diagnosed in the post-partum period of ≤10 years (OR = 1.68; 95 % CI, 1.12-2.52). The effect was present across all source populations and independent of the HR status of the HER2+ tumor. Adjusting for age at diagnosis (≤45 or >45 years) did not materially alter our results (OR = 1.78; 95 % CI, 1.08-2.93). These findings support the novel hypothesis that factors associated with the post-partum breast, possibly hormonal, are involved in the development of HER2+ tumors.

Sleep quality and perinatal depression in pregnant women treated in a primary care centre in Lima, Peru.

OBJECTIVE: The aim is to evaluate the association between sleep quality and perinatal depression in pregnant women between the 12th week of gestation and the 36th week of gestation in a maternity and child centre in Lima. METHODS: Analytical cross-sectional study in pregnant women cared for in a primary care centre between August and December 2019. The data were collected through a self-administered survey. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality. The evaluation of perinatal depression was performed with the Edinburgh Postnatal Depression Scale (EPDS). For the multivariate analysis, Poisson regression with robust variances was used to calculate the crude and adjusted prevalence ratios and their respective confidence intervals. RESULTS: The sample was composed of 200 participants. The median [IQR] age was 26 [22-32] years, and 111 (55.5%) pregnancies were unplanned. 52% presented a poor quality of sleep and the risk of perinatal depression was 31.5%. Poor quality of sleep was associated with a significantly higher frequency of perinatal depression (aPR = 4.8 for those with poor quality of sleep warranting medical attention, and aPR = 6.6 for those with poor quality of sleep warranting medical attention and treatment). CONCLUSIONS: There is a possible association between poor sleep quality and perinatal depression in pregnant women between weeks 12 and 36 of gestation. Operational research should be promoted to assess whether interventions to improve sleep quality could have a positive impact on reducing perinatal depression.

Draft genome sequence of Pseudomonas sp. GOM6, a lipolytic strain isolated from seawater of the Gulf of Mexico.

We report here the draft genome sequence of a marine Pseudomonas sp. novel species with lipase activity isolated from a deep-sea water sample of the Gulf of Mexico. The genome consists of 4.3 Mbp in 48 contigs.

Genomic and phenotypic characterization of Pseudomonas sp. GOM7, a novel marine bacterial species with antimicrobial activity against multidrug-resistant Staphylococcus aureus.

Antimicrobial resistance (AMR) represents a serious threat to global health. The development of new drugs to combat infections caused by bacteria resistant to multiple or even all available antibiotics is urgent. Most antibiotics used up to date have been identified from soil microorganisms. The marine environment represents an alternative source with great potential for the identification of microorganisms that produce bioactive molecules, including antibiotics. In this study, we analyzed the antibacterial activity of a collection of 82 bacterial strains isolated from marine water and sediment samples collected from the Southwestern Gulf of Mexico. Eight of the marine isolates inhibited the growth of different pathogenic bacteria, seven of which were identified as presumptive Pseudomonas aeruginosa. Interestingly, genome sequencing and phylogenetic analysis revealed that the remaining marine isolate showing antibacterial activity is a novel Pseudomonas species that we denominated Pseudomonas sp. GOM7, which was not pathogenic in the Galleria mellonella infection model in the conditions tested. Notably, Pseudomonas sp. GOM7 inhibited the growth of multidrug and methicillin-resistant strains of the priority pathogen Staphylococcus aureus. Our results show that the anti-S. aureus compound(s) produced by Pseudomonas sp. GOM7 can be extracted from the culture supernatant of this bacterium with the organic solvent ethyl acetate. Annotation of the Pseudomonas sp. GOM7 genome revealed the presence of several biosynthetic gene clusters predicted to code for possible antimicrobial compounds. Our results further highlight the potential of bacteria from the Gulf of Mexico as a source of novel antimicrobials.