Discovery of new natural products and biosynthetic gene clusters encoded in the genome of Streptomyces albus subsp. chlorinus

Streptomyces genomes encode numerous gene clusters able to synthesize secondary metabolites with potential pharmaceutical applications. However, a great number of these genes remain unexpressed under standard laboratory growth conditions, therefore hiding a rich reservoir of natural products in their encoded metabolic pathways. In this work, we applied two strategies to induce the expression of silent gene clusters from Streptomyces albus subsp. chlorinus: heterologous expression and in situ ribosome engineering. In the first approach, a cryptic gene cluster encoded by S. albus subsp. chlorinus genome was heterologously expressed in the chassis strain Streptomyces albus Del14. The resulting strain produced the previously known antibiotic nybomycin, which is potently active against quinolone-resistant Staphylococcus aureus. Expression of the nybomycin cluster in S. albus Del14 also resulted in the biosynthesis of the novel compound benzanthric acid, which might be the product of interaction between the nybomycin pathway and the host´s metabolism. In the second approach, we selected a highly streptomycin-resistant mutant derived from S. albus subsp. chlorinus. This strain exhibited enhanced expression of a type II PKS gene cluster compared to the wild type strain, leading to overproduction of the novel compound fredericamycin C2. A point mutation leading to lack of RsmG protein is likely to be responsible for the mutant phenotype.Das Chromosom von Streptomyceten enthält zahlreiche Gencluster, welche die Baupläne für die Synthese von Naturstoffen und potentiellen Therapeutika beinhalten. Dennoch kann unter Standard-Laborbedingungen oftmals nur eine unzureichende Expression dieser Gene erzielt werden. Eine bedeutende Anzahl von Naturstoffen bleibt somit unentdeckt. In dieser Arbeit haben wir zwei unterschiedliche Strategien angewandt, um die Expression von stillen Genclustern des Stammes Streptomyces albus subsp. chlorinus zu aktivieren: Heterologe Expression und in situ Ribosom-Engineering. Im ersten Ansatz wurde ein kryptisches Gencluster aus S. albus subsp. chlorinus im Wirt Streptomyces albus Del14 exprimiert. Die Mutante produzierte Nybomycin, ein bereits bekanntes Antibiotikum mit hoher Aktivität gegen Chinolon-resistenten Staphylococcus aureus. Die Expression des Nybomycin-Genclusters in S. albus Del14 stimulierte außerdem die Synthese des neuen Naturstoffs Benzanthric Acid - einem Produkt aus der Interaktion des Nybomycin-Stoffwechsels mit dem Wirtsmetabolismus. Für den zweiten Ansatz wurde eine stark Streptomycin-resistente Mutante von S. albus subsp. chlorinus gewählt, die im Vergleich zum Wildtyp eine erhöhte Expression eines Type II PKS Genclusters aufwies. Dies führte zur Produktionssteigerung der neuen Substanz Fredericamycin C2. Ursächlich für diesen Phänotyp ist das Fehlen des RsmG-Proteins ausgelöst durch eine Punktmutation

Bonsecamin: A New Cyclic Pentapeptide Discovered through Heterologous Expression of a Cryptic Gene Cluster

The intriguing structural complexity of molecules produced by natural organisms is uncontested. Natural scaffolds serve as an important basis for the development of molecules with broad applications, e.g., therapeutics or agrochemicals. Research in recent decades has demonstrated that by means of classic metabolite extraction from microbes only a small portion of natural products can be accessed. The use of genome mining and heterologous expression approaches represents a promising way to discover new natural compounds. In this paper we report the discovery of a novel cyclic pentapeptide called bonsecamin through the heterologous expression of a cryptic NRPS gene cluster from Streptomyces albus ssp. chlorinus NRRL B-24108 in Streptomyces albus Del14. The new compound was successfully isolated and structurally characterized using NMR. The minimal set of genes required for bonsecamin production was determined through bioinformatic analysis and gene deletion experiments. A biosynthetic route leading to the production of bonsecamin is proposed in this paper

Dudomycins: New Secondary Metabolites Produced after Heterologous Expression of an Nrps Cluster from Streptomyces albus ssp. Chlorinus Nrrl B-24108

Since the 1950s, natural products of bacterial origin were systematically developed to be used as drugs with a wide range of medical applications. The available treatment options for many diseases are still not satisfying, wherefore, the discovery of new structures has not lost any of its importance. Beyond the great variety of already isolated and characterized metabolites, Streptomycetes still harbor uninvestigated gene clusters whose products can be accessed using heterologous expression in host organisms. This works presents the discovery of a set of structurally novel secondary metabolites, dudomycins A to D, through the expression of a cryptic NRPS cluster from Streptomyces albus ssp. Chlorinus NRRL B-24108 in the heterologous host strain Streptomyces albus Del14. A minimal set of genes, required for the production of dudomycins, was defined through gene inactivation experiments. This paper also proposes a model for dudomycin biosynthesis

A New Approach to Detecting and Measuring Changes in the Feeding Behaviour Habits of Group-Housed Growing-Finishing Pigs

The present work aims to estimate the methods of repeatability and of a new non-parametric approach based on typifying individuals into classes and quantifying (%) the pigs in a group that show similar feeding behaviour habits (FBHs) in consecutive periods ("maintenance"). Both methods were estimated over six consecutive 14-day periods in two trials of group-housed growing-finishing pigs (n = 60 each). The first trial started in summer and ended in autumn, and pigs were fed a pelleted diet (HT-P). The second trial started in spring and ended in summer, and the same diet was fed mash (TH-M). The average daily feed intake obtained the lowest repeatability and maintenance values, and it progressively decreased as pigs grew, independent of environmental conditions or physical feed form, whereas the maintenance and repeatability of the number of feeder visits and the visit size decreased when environmental conditions changed from temperate to hot, and mash-fed pigs had higher maintenance and repeatability values for the time spent eating than pellet-fed pigs. In conclusion, the new approach (maintenance) is a tool that is complementary to the classic repeatability concept and is useful for analysing the evolution of FBHs across periods of time at the individual level

The Feeding Behaviour Habits of Growing-Finishing Pigs and Its Effects on Growth Performance and Carcass Quality: A Review

Based on the available data of feeding behaviour habits (FBHs), this work aimed to discuss which type of pig, according to its FBHs, performs better and is more efficient. As pigs grow, average daily feed intake, meal size, and feeding rate increase, whereas small variations or even decreases in time spent eating and daily feeder visits have been reported. Moreover, the sex, breed, space allowance, feeder design, feed form, diet composition, and environmental conditions modify FBHs. On the other hand, the literature indicates the existence of four types of pigs: pigs that eat their daily feed intake in many short meals (nibblers) or in few large meals (meal eaters) combined with eating fast (faster eaters) or slow (slow eaters). The available scientific literature about ad libitum fed pigs suggests that pigs eating faster with bigger meals eat more, gain more weight, and are fatter than pigs eating less, slower, and with smaller meals. However, the feeding rate and the meal size do not influence feed efficiency. In conclusion, studies comparing growing-finishing pigs with similar feed intake, but different feeding rate and meal size are needed to better understand the influence of FBHs on feed efficiency

Novel Fredericamycin Variant Overproduced by a Streptomycin-Resistant Streptomyces albus subsp. chlorinus Strain

Streptomycetes are an important source of natural products potentially applicable in the pharmaceutical industry. Many of these drugs are secondary metabolites whose biosynthetic genes are very often poorly expressed under laboratory cultivation conditions. In many cases, antibiotic-resistant mutants exhibit increased production of natural drugs, which facilitates the identification and isolation of new substances. In this study, we report the induction of a type II polyketide synthase gene cluster in the marine strain Streptomyces albus subsp. chlorinus through the selection of streptomycin-resistant mutants, resulting in overproduction of the novel compound fredericamycin C2 (1). Fredericamycin C2 (1) is structurally related to the potent antitumor drug lead fredericamycin A

Miramides A–D : Identification of Detoxin-like Depsipeptides after Heterologous Expression of a Hybrid NRPS-PKS Gene Cluster from Streptomyces mirabilis Lu17588

Natural products derived from plants, fungi or bacteria have been used for years in the medicine, agriculture and food industries as they exhibit a variety of beneficial properties, such as antibiotic, antifungal, anticancer, herbicidal and immunosuppressive activities. Compared to synthetic compounds, natural products possess a greater chemical diversity, which is a reason why they are profitable templates for developing pharmaceutical drug candidates and ongoing research on them is inevitable. Performing heterologous expression with unknown gene clusters is the preferred method to activate gene clusters that are not expressed in the wild-type strain under laboratory conditions; thus, this method offers a way to discover new interesting metabolites. Here, we report the gene cluster assembly of a hybrid NRPS-PKS gene cluster from Streptomyces mirabilis Lu17588, which was heterologously expressed in Streptomyces albus Del14. Four new compounds were produced by the obtained strain, which were named miramides A–D. Isolation and structure elucidation revealed similarity of the isolated compounds to the known depsipeptides rimosamides/detoxins

Is it Possible to Assess the Two-Domain Definition of the Broad Autism Phenotype Using the Available Measurement Tools?

Although, the operationalization of the autism spectrum disorder has been updated around two domains, the broad autism phenotype (BAP) one has not. Additionally, the items of the three common BAP measures, the Broad Autism Phenotype Questionnaire (BAPQ), the Autism Quotient, and the Social Responsiveness Scale (SRS), remain organized around a non-consensual number of factors. We explored whether the items of these measures matched with the two-domain operationalization through a parallel analysis, which has suggested two main components, and two expert judgments which have assessed item wording, relevance, and construct representativeness. A remaining pool of 48 BAP-relevant items suggested a possible under-representation of two subdomains. Despite the relevance of all the BAPQ items, only the SRS ones tapped in all subdomains

Psychometric Properties of the Spanish Version of the Broad Autism Phenotype Questionnaire: Strengths, Weaknesses, and Future Improvements

The Broad autism phenotype (BAP) refers to a set of subclinical behavioural characteristics qualitatively similar to those presented in Autism spectrum disorders (ASDs). The BAP questionnaire (BAPQ) has been widely used to assess the BAP both in relatives of ASD people and within the general population. The current study presents the first Spanish version of the BAPQ (BAPQ-SP) and analyses its psychometric properties, including validity evidences based on the BAPQ scores relationship with other variables. Our results only support the use of the Aloof and Rigid sub-scales to assess this phenotype, whereas Pragmatic Language sub-scale seems to be the main source of misfit. This research represents a first step in the study of the BAP features in the Spanish population