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Streptomyces albusJ1074 is one of the most popular heterologous expression platforms among streptomycetes. Identification of new genes and mutations that influence specialized metabolism in this species is therefore of great applied interest. Here, we describe S. albusKO-1304 that was isolated as a spontaneous lincomycin-resistant variant of double rpsLR94GrsmGR15SG40Emutant KO-1295. Besides altered antibiotic resistance profile, KO-1304 exhibited increased antibiotic activity as compared to its parental strains. KO-1304 genome sequencing revealed mutations within gene XNR_2147encoding putative TetR-like protein. Gene XNR_2146for efflux protein is the most likely target of repressing action of Xnr_2147. Our data agree with the scenario where lincomycin resistance phenotype of KO-1304 arose from inability of mutated Xnr_2147 protein to repress XNR_2146. Introduction of additional copy of XNR_2146into wild type strain increased antibiotic activity of the latter, attesting to the practical value of transporter genes for strain improvement.

Soil bacteria from the genus Streptomyces, phylum Actinobacteria, feature a complex metabolism and diverse adaptations to environmental stress. These characteristics are consequences of variable nutrition availability in the soil and allow survival under changing nitrogen conditions. Streptomyces coelicoloris a model organism for Actinobacteria and is able to use nitrogen from a variety of sources including unusual compounds originating from the decomposition of dead plant and animal material, such as polyamines or monoamines (like ethanolamine). Assimilation of nitrogen from these sources in S. coelicolorremains largely unstudied. Using microbiological, biochemical and in silico approaches, it was recently possible to postulate polyamine and monoamine (ethanolamine) utilization pathways in S. coelicolor.Glutamine synthetase-like enzymes (GS-like) play a central role in these pathways. Extensive studies have revealed that these enzymes are able to detoxify polyamines or monoamines and allow the survival of S. coelicolorin soil containing an excess of these compounds. On the other hand, at low concentrations, polyamines and monoamines can be utilized as nitrogen and carbon sources. It has been demonstrated that the first step in poly-/monoamine assimilation is catalyzed by GlnA3 (a γ-glutamylpolyamine synthetase) and GlnA4 (a γ-glutamylethanolamide synthetase), respectively. First insights into the regulation of polyamine and ethanolamine metabolism have revealed that the expression of the glnA3and the glnA4gene are controlled on the transcriptional level.

Extracts from Streptomycessp. S4.7 isolated from the rhizosphere of edelweiss, an alpine medicinal plant, exhibited activity against Gram-positive bacteria. LC-HRMS analyses of the extracts resulted in the detection of two unknown, structurally related lipopeptides that were assumed to be responsible for the antibiotic activity. LC-MS guided isolation and structure elucidation of viennamycins A and B (1and 2) by HR-MS/MS, 1D and 2D NMR, and Marfey’s analyses revealed them to be novel compounds, with viennamycin A containing cysteic acid, a unique feature for lipopeptides. Tests for antibacterial, antifungal, and cytotoxic activities of purified viennamycins, both with and without divalent cations, did not reveal any bioactivity, suggesting that their biological function, which could not be determined in the tests used, is atypical for lipopeptides. The genome of Streptomycessp. S4.7 was sequenced and analyzed, revealing the viennamycin biosynthetic gene cluster. Detailed bioinformatics-based analysis of the viennamycin gene cluster allowed elucidation of the biosynthetic pathway for these lipopeptides.

Tsolis et al., reveal that the regulation of protein secretion in a Gram positive bacterial model is complex. Some of this regulation is transcriptional but a lot occurs post-transcriptionally and affects different exported proteins in different ways. Main Sec and chaperone machineries are not part of this regulation.

The proteogenomes and secretomes of dominant human and zoonotic S. aureuslineages CC8, CC22 and CC398 were compared revealing genomic and regulatory differences in the secretion of 869 proteins. In the core secretome, 101 secreted or cell surface anchored virulence factors contribute with 82.4% to total secretome abundance. CC398 isolates showed higher secretion of α- and ß-hemolysins and lower secretion of surface proteins resulting in strong hemolysis and decreased biofilm formation because of lower SigB activity compared to human-specific CC8 and CC22.

Male sex represents one of the major risk factors for severe COVID-19 outcome. However, underlying mechanisms that mediate sex-dependent disease outcome are as yet unknown. Here, we identify the CYP19A1gene encoding for the testosterone-to-estradiol metabolizing enzyme CYP19A1 (also known as aromatase) as a host factor that contributes to worsened disease outcome in SARS-CoV-2-infected males. We analyzed exome sequencing data obtained from a human COVID-19 cohort (n = 2,866) using a machine-learning approach and identify a CYP19A1-activity-increasing mutation to be associated with the development of severe disease in men but not women. We further analyzed human autopsy-derived lungs (n = 86) and detect increased pulmonary CYP19A1expression at the time point of death in men compared with women. In the golden hamster model, we show that SARS-CoV-2 infection causes increased CYP19A1expression in the lung that is associated with dysregulated plasma sex hormone levels and reduced long-term pulmonary function in males but not females. Treatment of SARS-CoV-2-infected hamsters with a clinically approved CYP19A1 inhibitor (letrozole) improves impaired lung function and supports recovery of imbalanced sex hormones specifically in males. Our study identifies CYP19A1as a contributor to sex-specific SARS-CoV-2 disease outcome in males. Furthermore, inhibition of CYP19A1 by the clinically approved drug letrozole may furnish a new therapeutic strategy for individualized patient management and treatment.

A genome reduction can be a good starting point for optimizing a wild-type strain for use in an industrial process. In a genome reduction, a selection of genes is removed with the intention of obtaining a robust strain with enhanced production properties. The complex soil bacterium Streptomyces lividansTK24 produces many compounds that can hinder the industrial objective. Genome reduction is often based on phylogenetic conservation and absolute gene expression. Here, flux balance analysis is proposed as an additional and complementary method for identifying potential targets for genome reduction. The effect of deletions of single metabolic genes and selected groups of adjacent metabolic genes on bacterial growth is simulated in a high throughput fashion. Targets identified through this method show lower gene expression and are less likely to be conserved between different Streptomycesstrains. Gene expression data are used for assessing the effect of gene deletions in silico to improve prediction accuracy.

Streptomyces cyanogenusS136 is the only known producer of landomycin A (LaA), one of the founding members of angucycline family of aromatic polyketides. LaA displays potent anticancer activities which has made this natural product a target of numerous chemical and cell biological studies. Little is known about the potential of S136 strain to produce other secondary metabolites. Here we report complete genome sequence of LaA producer and how we used this sequence to evaluate for this species its phylogenetic position and diversity of gene clusters for natural product biosynthesis.

Glycopeptide antibiotics (GPAs) are last defense line drugs against multidrug-resistant Gram-positive pathogens. Natural GPAs teicoplanin and vancomycin, as well as semisynthetic oritavancin, telavancin, and dalbavancin, are currently approved for clinical use. Although these antibiotics remain efficient, emergence of novel GPA-resistant pathogens is a question of time. Therefore, it is important to investigate the natural variety of GPAs coming from so-called “rare” actinobacteria. Herein we describe a novel GPA producer—Nonomuraea coxensisDSM 45129. Its de novosequenced and completely assembled genome harbors a biosynthetic gene cluster (BGC) similar to the dbvBGC of A40926, the natural precursor to dalbavancin. The strain produces a novel GPA, which we propose is an A40926 analogue lacking the carboxyl group on the N-acylglucosamine moiety. This structural difference correlates with the absence of dbv29—coding for an enzyme responsible for the oxidation of the N-acylglucosamine moiety. Introduction of dbv29into N. coxensisled to A40926 production in this strain. Finally, we successfully applied dbv3and dbv4heterologous transcriptional regulators to trigger and improve A50926 production in N. coxensis, making them prospective tools for screening other Nonomuraeaspp. for GPA production. Our work highlights genus Nonomuraeaas a still untapped source of novel GPAs.

ABSTRACTSalmonellapathogenicity island (SPI) 2 type three secretion system (T3SS)-mediated effector molecules facilitate bacterial survival in phagocytes but their role in the intestinal epithelium in vivoremains ill-defined. Using our neonatal murine infection model in combination with SPI2 reporter technology and RNA-Seq of sorted primary enterocytes, we demonstrate expression of SPI2 effector molecules by intraepithelial SalmonellaTyphimurium (S. Typhimurium). Contrary to expectation, immunostaining revealed that infection with SPI2 T3SS-mutants resulted in significantly enlarged intraepithelial Salmonella-containing vacuoles (SCV) with altered cellular positioning, suggesting impaired apical to basolateral transmigration. Also, infection with isogenic tagged S. Typhimurium strains revealed a reduced spread of intraepithelial SPI2 T3SS mutant S. Typhimurium to systemic body sites. These results suggest that SPI2 T3SS effector molecules contribute to enterocyte apical to basolateral transmigration of the SCV during the early stage of the infection.