Producing Strain Research Articles

Production of gamma-aminobutyric acid by lactic acid bacteria of marine origin from Vietnam

Gamma-aminobutyric acid (GABA) is a non-proteinogenic amino acid, which functions as a neurotransmitter in the central nervous system. GABA has been shown to have several positive effects on human health, including reducing anxiety and promoting relaxation. In this study, various fermented fish products were screened for their ability to produce GABA. A total of 35 acid lactic producing strains were isolated from 8 samples of marine organism, 10 strains were found to have GABA-producing abilities. These strains were identified using 16S rDNA sequencing. The GABA concentrations produced by the 10 isolates ranged from 725 to 5590 mg/L. Lactobacillus brevis GB111 is the best isolated GABA producing strain, with a conversion rate up to 90.3%, which suggests that these strains may have potential applications in the food and pharmaceutical industries as a source of GABA.

Obtaining a strain-producer of the recombinant rbd antigen of the SARS-CoV-2 virus

The SARS-CoV-2 virus is a new coronavirus that caused the worldwide pandemic of the human respiratory disease COVID-19. To detect the SARS-CoV-2 virus in environmental objects and in clinical samples, molecular genetic (PCR), immunological (ELISA, IHA), virological research methods are used. The purpose of this study was to obtain a strain-producer of the recombinant protein Spike_RBD, with an introduced hex histidine label, for its subsequent development, chromatographic purification and use in the development of experimental kits for the immunological diagnosis of COVID-19 in humans and to assess the intensity of the cellular and humoral immune response to the SARS-CoV-2 virus. To achieve the goal, the following tasks were set: 1) to create a genetic construct for the expression of Spike RBD antigen in Escherichia coli cells; 2) to obtain a Spike RBD antigen producer strain; 3) to evaluate the effectiveness of Spike RBD antigen expression by a producer strain. The relevance of the work is related to the production and use of recombinant RBD antigen of the SARS-CoV-2 virus, as well as to the development of diagnostic test systems.

Computation-aided studies related to the induction of specialized metabolite biosynthesis in microbial co-cultures: An introductory overview

Co-cultivation is an effective method of inducing the production of specialized metabolites (SMs) in microbial strains. By mimicking the ecological interactions that take place in natural environment, this approach enables to trigger the biosynthesis of molecules which are not formed under monoculture conditions. Importantly, microbial co-cultivation may lead to the discovery of novel chemical entities of pharmaceutical interest. The experimental efforts aimed at the induction of SMs are greatly facilitated by computational techniques. The aim of this overview is to highlight the relevance of computational methods for the investigation of SM induction via microbial co-cultivation. The concepts related to the induction of SMs in microbial co-cultures are briefly introduced by addressing four areas associated with the SM induction workflows, namely the detection of SMs formed exclusively under co-culture conditions, the annotation of induced SMs, the identification of SM producer strains, and the optimization of fermentation conditions. The computational infrastructure associated with these areas, including the tools of multivariate data analysis, molecular networking, genome mining and mathematical optimization, is discussed in relation to the experimental results described in recent literature. The perspective on the future developments in the field, mainly in relation to the microbiome-related research, is also provided.

Bioprotective cultures and bacteriocins as food preservatives.

Food preservation technologies face the challenge of extending product shelf life applying different factors to prevent the microbiological spoilage of food and inhibit/inactivate food borne pathogens maintaining or even enhancing its quality. One such preservation strategy is the application of bacteriocins or bacteriocin-producer cultures as a kind of food biopreservation. Bacteriocins are ribosomally synthesized small polypeptide molecules that exert antagonistic activity against closely related and unrelated bacteria without harming the producing strain by specific immunity proteins. This chapter aims to contribute to current knowledge about innovative natural preservative agents and their application in the food industry. Specifically, its purpose is to analyze the classification of bacteriocins from lactic acid bacteria (LAB), desirable characteristics of bacteriocins that position them in a privileged place in food biopreservation technology, their success story as well as the bacteriocinogenic LAB in various food systems. Finally, challenges and barrier strategies used to enhance the efficiency of the bacteriocins antimicrobial effect are presented in this chapter.

Evaluation of Biofilm Forming Potential and Antimicrobial Resistance Profile of S. aureus and P. aeruginosa Isolated from Peripheral Venous Catheters and Urinary Catheters In Algeria, in vitro Study

Abstract Pseudomonas aeruginosa and Staphylococcus aureus are prominent pathogens responsible for device-associated infections that pose a significant challenge in clinical management. The biofilm-forming ability of these bacteria is a major factor contributing to treatment failures and the recurrence of infections. This study was conducted to evaluate the biofilm production potential of these bacteria isolated from urinary and peripheral venous catheters. Additionally, the study aimed to determine the antibiotic resistance pattern of biofilm producers and non-biofilm producers strains. The identification of bacteria followed conventional microbiological procedures, while the detection of biofilm production involved both qualitative and quantitative methods using Congo red agar (CRA) and Tissue Culture Plate (TCP) techniques, respectively. Antibiotic susceptibility was determined through the Kirby-Bauer disc diffusion method. Of the 22 strains of P. aeruginosa and 29 strains of S. aureus isolated from 116 Peripheral venous catheters and 20 urinary catheters, the CRA method identified 27.27% of P. aeruginosa and 24.14% of S. aureus strains as strong biofilm producers. Meanwhile, 9.09% of P. aeruginosa and 51.72% of S. aureus strains were moderate biofilm producers. The TCP method detected 9.09% of P. aeruginosa and 37.93% of S.aureus strains as strong biofilm producers, while 54.55% of P. aeruginosa and 48.28% of S. aureus strains were moderate biofilm producers. The antibiotic susceptibility test revealed that biofilm-producing bacteria were mostly more resistant to antibiotics than nonbiofilm producers. All S. aureus strains, were resistant to Penicillin (100%), but susceptible to Vancomycin (100%) and Teicoplanin (100%). All P. aeruginosa strains were susceptible to almost all groups of antibiotics, except for Ticarcillin (18.18%), Piperacillin (27.27%), Imipenem (100%), and Rifampicin (100%). Our findings showed that biofilm-producer strains exhibited high resistance rates to only some antibiotics, and emphasized the importance of seeking new strategies to prevent biofim formation and combat the emergence of antibiotic resistance.

ACCUMULATION OF EXOPOLYSACCHARIDES BY YEASTS OF RHODOTORULA SP.

The work is devoted to the search and assessment of the possibility of using alternative carbon sources for the production of exopolysaccharides by yeasts of the genus Rhodotorula sp. Exopolysaccharides (EPS) are high-molecular polymer metabolites of microorganisms produced on the outside of cells. They have a high ability to gel, emulsify, and suspend. The ability to synthesize EPS has been found in many microorganisms, but their level varies widely both for different EPS producers and for one producer under different cultivation conditions. Therefore, the search for active producer strains, alternative nutrient media, and the development of effective microbial exopolysaccharide technologies is an urgent task of biotechnology. The capabilities of three species of the genus Rhodotorula were evaluated: R.rubra, R.minuta, R.glutinis to secrete and accumulate exopolysaccharides (EPS) on classical Sabouraud's medium with glucose was evaluated. The maximum amount of EPS in the culture fluid of R. minuta was determined. Differential diagnostic Hiss media with maltose, lactose and mannitol were used to determine the use of different carbon-containing substrates by yeast cultures. The ability of all three studied yeast species to use maltose and mannitol as a carbon source was established. Accordingly, these substrates were added to the Sabouraud medium in the amount of 20 g/l, 40 g/l or 60 g/l. It was noted that the maximum amount of EPS in the culture liquid of R. rubra and R. minuta accumulates under the conditions of using 60 g/l of mannitol as a carbon source. For R.glutinis, the highest EPS indicator was established on a medium with 60 g/l of glucose.

Isolation, Identification And Toxin Production From Vaginal Clinical Isolates Of Candida Albicans

Thirty two isolates of candida albican were sequestered from female patients with vaginal ulcer (lying in marjan hospital hillia city) .The vaginal swap were cultured on  sabouraud dextrose broth and agar plate respectively . for differential identification of C. albican, hi chrome candida agar was used. Gram staining used to smear of vaginal scrapings. suspected isolates of C.albican then immunized on corn meal agar  mediocre for chlamydospore, formation , for germ tube formation the isolates of  Caliban was cultured in human serum .Carbohydrate assimilation and fe mentation  tests also used for further identification . four identification s trains of C.albican namely (  CA1, CA2, CA3, CA4) were selected according to their antagonistic activity against  standard strain of bacteria E.coli NCTC5933 and staphylococcus aureus NCTC6571 ;  To produced extracellular toxin of glycoprotein nature in solid media and fermentation  liquid media . The toxin which produced (secondary metabolites) don’t effecting the producers strains of C.albican (CA1,CA2,CA3,CA4) ,but the produced toxin was  inhibited the growth of standard strain of candida albicans ATcc8201( sensitive ).  Simple method used for toxin extraction by using ethanol 90%. And the extracted toxin  from free cells supernatant . cytotoxicity of toxin against human blood cells were 6 ppm also, the stability of producing toxin was determined.

Phenotypical Detection of β-Lactamases in a Multidrug-Resistant and Extensively Drug-Resistant Chryseobacterium indologens: A Rare Human Pathogen With Special References to Risk Factor.

Chryseobacterium indologenes is gram-negative bacteria that cause infection in humans. It is less frequently isolated in the laboratory. The development of drug-resistant and its intrinsic ability to resist a wide range of antimicrobials enables them to cause mortality in an immunocompromised patient with a longer hospital stay. Our study objectives are to investigate antimicrobial-resistant patterns, drug-resistant enzymes, and the risk factor analysis associated with multidrug-resistant (MDR), extensively drug-resistant (XDR), and Pan-drug resistant (PDR) within 2 years. Altogether 53 strains of Chryseobacterium indologens were obtained from 5000 specimens that were processed for routine bacterial culture. The bacterial identification was done using conventional techniques (colony morphology, gram staining, flexirubin test, and biochemical tests) as well as the VITEK-2 System to further confirm. The bacterial isolate were processed to observe antimicrobial susceptibility test (AST) using disk diffusion method. MDR XDR and PDR were classified following European Centre for Disease Prevention and Control guidelines. C. indologens strains with beta-lactamases such as extended-spectrum beta-lactamases (ESBL), metallo beta-lactamases (MBL), and Amp-C beta-lactamases (Amp-C) were detected phenotypically. The highest isolation of C. indologens was observed in a sputum sample. In vitro antimicrobial susceptibility test revealed susceptibility to tigecycline followed by levofloxacin, cotrimoxazole, and piperacillin-tazobactam. From 53 isolates of C. indologens, MDR accounts for 56.60% and 22.64% for XDR. Combined antimicrobial therapy and longer hospital stay were found to be the leading risk factor. All 53 C. indologenes strains were detected as MBL. Total ESBL was detected in 16.98% of MBL producer strains and Amp-C was observed in 13.20% of MBL-producing strains. All 3 enzyme co-oproducers were seen in only 5.66% of C. indologens. Although it is rarely encountered in the laboratory, it showed a remarkable effect in patients with underlying predisposing factors and prolonged hospital stays. The presence of betalactamases determined the drug-resistant activity on a wide spectrum of tested antibiotics.

DYNAMICS OF INFLUENCE OF SOME HEAVY METALS ON THE BIOSYNTHETIC CAPACITY OF STREPTOMYCES RECEFENSIS VAR. LYTICUS 2P-15 FOR THE SYNTHESIS OF AMYLOLYTIC ENZYMES

Modern biotechnology of enzymes is a promising and rapidly developing branch of industrial biotechnology, which requires new promising research in the aspect of optimizing the conditions of biosynthesis of enzymes. Modulation of the biosynthetic activity of producer strains allows to significantly increase the economic output of production. The most important factor in increasing efficiency is the composition of the nutrient medium, which can be optimized depending on the needs of the microorganisms. Within the framework of a complex study of the optimization of the composition of the nutrient medium by the simplex method of mathematical modeling, the aim of the work is to study the effect of some heavy metal ions on the biosynthetic capacity of the strain Streptomyces recefensis var. lyticus 2P-15. The influence of some heavy metal ions on the biosynthetic capacity of the strain Streptomyces recefensis var. lyticus 2P-15 in terms of synthesis of amylolytic enzymes, accumulation of biomass and protein. The object of the study is the strain Streptomyces recefensis var. lyticus 2P-15, obtained by three-stage selection of the producer. The simplex method of selecting the composition of the environment was used for the research. Standard methods for determining biomass and amylolytic activity were used to analyze biosynthetic activity. It was established that adding Co, Mo, and Cd ions at a concentration of 0.00001 and 0.0005 mg/ml inhibits the growth of biomass, but increases the protein content by 13-57%, respectively. It was determined that the addition of Co, Mo, Cd ions in different concentrations helps to increase both the quantitative and qualitative composition of the synthesized enzymes, and the best response was an increase in amylolytic activity by 354% compared to the control. The prospect of further research into the optimization of the biosynthesis of actinomycetes simplex by the method of other aspects of its regulation will increase the biosynthetic capacity of the studied strain, which will positively affect the economic output of the production of amylolytic enzyme preparations by obtaining microbial synthesis.

Production of Recombinant Biopharmaceuticals in Chlamydomonas reinhardtii

This review aimed to present Chlamydomonas reinhardtii as an alternative for heterologous protein production, especially for biopharmaceuticals, and its general characteristics when compared with other expression systems. The need to produce heterologous proteins for industrial interest, therapeutic ends, and diagnostic kits has led to the development of recombinant microalgal technology. This technology presents some interesting features, such as rapid growth and low transgene dispersion compared to plants, the ability to fold complex proteins compared to bacteria, and low production costs compared to other expression systems, such as yeast and mammalian cells. Overall, C. reinhardtii heterologous protein expression is coming of age with several research groups focused on developing an optimal producer strain.

Ethanol tolerance of Clostridium thermocellum: the role of chaotropicity, temperature and pathway thermodynamics on growth and fermentative capacity

BackgroundClostridium thermocellum is a promising candidate for consolidated bioprocessing of lignocellulosic biomass to ethanol. The low ethanol tolerance of this microorganism is one of the remaining obstacles to industrial implementation. Ethanol inhibition can be caused by end-product inhibition and/or chaotropic-induced stress resulting in increased membrane fluidization and disruption of macromolecules. The highly reversible glycolysis of C. thermocellum might be especially sensitive to end-product inhibition. The chaotropic effect of ethanol is known to increase with temperature. This study explores the relative contributions of these two aspects to investigate and possibly mitigate ethanol-induced stress in growing and non-growing C. thermocellum cultures.ResultsTo separate chaotropic from thermodynamic effects of ethanol toxicity, a non-ethanol producing strain AVM062 (Pclo1313_2638::ldh* ∆adhE) was constructed by deleting the bifunctional acetaldehyde/alcohol dehydrogenase gene, adhE, in a lactate-overproducing strain. Exogenously added ethanol lowered the growth rate of both wild-type and the non-ethanol producing mutant. The mutant strain grew quicker than the wild-type at 50 and 55 °C for ethanol concentrations ≥ 10 g L−1 and was able to reach higher maximum OD600 at all ethanol concentrations and temperatures. For the wild-type, the maximum OD600 and relative growth rates were higher at 45 and 50 °C, compared to 55 °C, for ethanol concentrations ≥ 15 g L−1. For the mutant strain, no positive effect on growth was observed at lower temperatures. Growth-arrested cells of the wild-type demonstrated improved fermentative capacity over time in the presence of ethanol concentrations up to 40 g L−1 at 45 and 50 °C compared to 55 °C.ConclusionPositive effects of temperature on ethanol tolerance were limited to wild-type C. thermocellum and are likely related to mechanisms involved in the ethanol-formation pathway and redox cofactor balancing. Lowering the cultivation temperature provides an attractive strategy to improve growth and fermentative capacity at high ethanol titres in high-cellulose loading batch cultivations. Finally, non-ethanol producing strains are useful platform strains to study the effects of chaotropicity and thermodynamics related to ethanol toxicity and allow for deeper understanding of growth and/or fermentation cessation under industrially relevant conditions.

Evolutionary and reverse engineering in Saccharomyces cerevisiae reveals a Pdr1p mutation-dependent mechanism for 2-phenylethanol tolerance

Background2-Phenylethanol (2-PE), a higher alcohol with a rose-like odor, inhibits growth of the producer strains. However, the limited knowledge regarding 2-PE tolerance mechanisms renders our current knowledge base insufficient to inform rational design.ResultsTo improve the growth phenotype of Saccharomyces cerevisiae under a high 2-PE concentration, adaptive laboratory evolution (ALE) was used to generate an evolved 19–2 strain. Under 2-PE stress, its OD600 and growth rate increased by 86% and 22% than that of the parental strain, respectively. Through whole genome sequencing and reverse engineering, transcription factor Pdr1p mutation (C862R) was revealed as one of the main causes for increased 2-PE tolerance. Under 2-PE stress condition, Pdr1p mutation increased unsaturated fatty acid/saturated fatty acid ratio by 42%, and decreased cell membrane damage by 81%. Using STRING website, we identified Pdr1p interacted with some proteins, which were associated with intracellular ergosterol content, reactive oxygen species (ROS), and the ATP-binding cassette transporter. Also, the results of transcriptional analysis of genes encoded these proteins confirmed that Pdr1p mutation induced the expression of these genes. Compared with those of the reference strain, the ergosterol content of the PDR1_862 strain increased by 72%–101%, and the intracellular ROS concentration decreased by 38% under 2-PE stress. Furthermore, the Pdr1p mutation also increased the production of 2-PE (11% higher).ConclusionsIn the present work, we have demonstrated the use of ALE as a powerful tool to improve yeast tolerance to 2-PE. Based on the reverse engineering, transcriptional and physiological analysis, we concluded that Pdr1p mutation significantly enhanced the 2-PE tolerance of yeast by regulating the fatty acid proportion, intracellular ergosterol and ROS. It provides new insights on Pdr1p mediated 2-PE tolerance, which could help in the design of more robust yeasts for natural 2-PE synthesis.

Engineering the Phenylpropanoid Pathway in Rhodosporidium toruloides for Naringenin Production from Tyrosine by Leveraging on its Native PAL Gene

Flavonoids are valued for their beneficial properties. This was a proof-of-concept study to show that the PAL gene in Rhodosporidium toruloides (R. toruloides) could be harnessed and only two genes 4CL and CHS needed to be inserted to create the naringenin producing strain, CBS-N. The growth of CBS-N reached a higher OD600 86.1 compared to 31.8 by wildtype. High-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC–MS) confirmed CBS-N successfully produced 0.038 mg/L naringenin and 16.9 mg/L p-coumaric acid via its PAL/TAL activity when supplemented with tyrosine, although the conversion efficiency of 4CL and CHS genes was the limiting factor. Metabolic profiling by gas chromatography–mass spectrometry (GC–MS) showed that, in the CBS-N strain, metabolic flux was toward glycolysis and the TCA cycle to produce malonyl CoA, the precursor for naringenin synthesis, and away from fatty acids synthesis pathway. Our study showed that microorganisms containing a native PAL gene, such as R. toruloides, could be harnessed for flavonoids production via precision fermentation.

Bacteriophages as an alternative for biological control of biofilm-forming Salmonella enterica.

Salmonellosis is one of the most common foodborne diseases worldwide. Surface adherence and biofilm formation are among the main strategies evolved by Salmonella to survive under harsh conditions and are risk factors for its spread through the food chain. Owing to the increase in antimicrobial resistance, there is a growing need to develop other methods to control foodborne pathogens, and bacteriophages have been suggested as a potential alternative for this purpose. The aim of this study was to evaluate bacteriophages as a biological control of Salmonella enterica serotypes to inhibit and remove bacterial biofilms. A total of 12 S. enterica isolates were selected for this study, all of which were biofilm producers. Seven bacteriophages were tested, individually and in a cocktail, for their host range and efficiency of plating (EOP). The phage cocktail was evaluated for its antibiofilm effect against the Salmonella biofilms. Phages UPF_BP1, UPF_BP2, UPF_BP3, UPF_BP6, and 10:2 possessed a broad lytic spectrum and could infect all S. enterica strains. Phages 10:2, UPF_BP6, and UPF_BP3 had high EOP in 10, 9, and 9 out of the 12 S. enterica strains, respectively. The cocktail was able to infect all S. enterica strains and had a high EOP in 10 out of 12 S. enterica isolates, presenting a broader host range than any of the tested single phages. A wide variation of inhibition among strains was observed, ranging from 14.72% to 88.53%. Multidrug-resistant and strong biofilm producer strains showed high biofilm inhibition levels by phage cocktail. Our findings demonstrate the ability of the cocktail to prevent biofilm formation and remove formed biofilms of Salmonella. These results indicate that the phage cocktail is a promising candidate to be used as an alternative for the control of Salmonella biofilms through surface conditioning.

Current and Emerging Treatment Options for Multidrug Resistant Escherichia coli Urosepsis: A Review.

Escherichia coli is a versatile commensal and pathogenic member of the human microflora. As the primary causative pathogen in urosepsis, E. coli places an immense burden on healthcare systems worldwide. To further exacerbate the issue, multi drug resistance (MDR) has spread rapidly through E. coli populations, making infections more troublesome and costlier to treat. This paper aimed to review the literature concerning the development of MDR in uropathogenic E. coli (UPEC) and explore the existing evidence of current and emerging treatment strategies. While some MDR strains maybe treated with β-lactam-β-lactamase inhibitor combinations as well as cephalosporins, cephamycin, temocillin and fosfomycin, current treatment strategies for many MDR UPEC strains are reliant on carbapenems. Carbapenem overreliance may contribute to the alarming dissemination of carbapenem-resistance amongst some UPEC communities, which has ushered in a new age of difficult to treat infections. Alternative treatment options for carbapenem resistant UPEC may include novel β-lactam-β-lactamase or carbapenemase inhibitor combinations, cefiderocol, polymyxins, tigecycline, aminoglycosides or fosfomycin. For metallo-β-lactamase producing strains (e.g., NDM, IMP-4), combinations of cefazidime-avibacam with aztreonam have been used. Additionally, the emergence of new antimicrobials brings new hope to the treatment of such infections. However, continued research is required to successfully bring these into the clinic for the treatment of MDR E. coli urosepsis.

144. Gram Negative Bacteria with Increased Minimal Inhibitory Concentration for Cefiderocol among Pediatric Patients in a Northern Italy Hospital.

Abstract Background Cefiderocol is a siderophore cephalosporin active against Gram negative (GN) carbapenem resistant bacteria, approved in Italy in September 2020 for adult patients. In pediatric population off label use is allowed when severe infections from multidrug resistance (MDR) GN bacteria occur. Recently, some authors reported the emergence, among strains of Enterobacterales resistant to ceftazidime avibactam, of cross-resistance with cefiderocol. The aim of this study is to describe GN strains with increased Minimal Inhibitory Concentration (MIC) for cefiderocol isolated in our hospital. Methods This is a retrospective, single-center study conducted in Istituto Giannina Gaslini Pediatric Hospital (Genoa, Italy) from 1st January 2020 to 31st April 2022. We collected all strains of MDR GN bacteria whit increased MIC for cefiderocol isolated in our hospital. Cefiderocol susceptibility testing was performed by disk diffusion assay with the disk of 30 μg (Kirby-Bauer method, KB) according to EUCAST’s recommendations and KB breakpoints. We collected demographical data, previous colonization (if note), carbapenemases production, clinical outcomes (infections from MDR; death at 7 and 30 days; ICU admission). Results Overall, 10 GN strains with increased MIC for cefiderocol were collected. 9/10 were Enterobacterales (4 Escherichia coli, 2 Enterobacter cloacae complex, 3 Klebsiella pneumoniae), one was Acinetobacter baumannii. 8/10 patients were admitted to other hospital in the six months before admission in our hospital, data about previous colonization were unknown. All MDR isolated produced metallo-β-lactamase [MBL] (5/10 New Delhi metallo-β-lactamase [NDM], 5/10 Verona integron-encoded metallo β-lactamase [VIM]). Four patients developed infection due to MDR (2 urinary tract infections, 1 bloodstream infection, 1 surgical wound), 2/4 patients died during the hospitalization. Conclusion Our study confirms that MDR producing MBL carbapenemases may have reduce susceptibility to cefiderocol, even if never exposed to this siderophore cephalosporin. Due to the possibility of cross resistance with MDR resistant to ceftazidime/avibactam, cefiderocol should be carefully prescribe in empirical treatment of MBL producers strains. Disclosures All Authors: No reported disclosures.

Copper selects for siderophore-mediated virulence in Pseudomonas aeruginosa

BackgroundIron is essential for almost all bacterial pathogens and consequently it is actively withheld by their hosts. However, the production of extracellular siderophores enables iron sequestration by pathogens, increasing their virulence. Another function of siderophores is extracellular detoxification of non-ferrous metals. Here, we experimentally link the detoxification and virulence roles of siderophores by testing whether the opportunistic pathogen Pseudomonas aeruginosa displays greater virulence after exposure to copper. To do this, we incubated P. aeruginosa under different environmentally relevant copper regimes for either two or twelve days. Subsequent growth in a copper-free environment removed phenotypic effects, before we quantified pyoverdine production (the primary siderophore produced by P. aeruginosa), and virulence using the Galleria mellonella infection model.ResultsCopper selected for increased pyoverdine production, which was positively correlated with virulence. This effect increased with time, such that populations incubated with high copper for twelve days were the most virulent. Replication of the experiment with a non-pyoverdine producing strain of P. aeruginosa demonstrated that pyoverdine production was largely responsible for the change in virulence.ConclusionsWe here show a direct link between metal stress and bacterial virulence, highlighting another dimension of the detrimental effects of metal pollution on human health.

Exploring Micromonospora as Phocoenamicins Producers.

Over the past few years, new technological and scientific advances have reinforced the field of natural product discovery. The spirotetronate class of natural products has recently grown with the discovery of phocoenamicins, natural actinomycete derived compounds that possess different antibiotic activities. Exploring the MEDINA's strain collection, 27 actinomycete strains, including three marine-derived and 24 terrestrial strains, were identified as possible phocoenamicins producers and their taxonomic identification by 16S rDNA sequencing showed that they all belong to the Micromonospora genus. Using an OSMAC approach, all the strains were cultivated in 10 different media each, resulting in 270 fermentations, whose extracts were analyzed by LC-HRMS and subjected to High-throughput screening (HTS) against methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis H37Ra and Mycobacterium bovis. The combination of LC-UV-HRMS analyses, metabolomics analysis and molecular networking (GNPS) revealed that they produce several related spirotetronates not disclosed before. Variations in the culture media were identified as the most determining factor for phocoenamicin production and the best producer strains and media were established. Herein, we reported the chemically diverse production and metabolic profiling of Micromonospora sp. strains, including the known phocoenamicins and maklamicin, reported for the first time as being related to this family of compounds, as well as the bioactivity of their crude extracts. Although our findings do not confirm previous statements about phocoenamicins production only in unique marine environments, they have identified marine-derived Micromonospora species as the best producers of phocoenamicins in terms of both the abundance in their extracts of some major members of the structural class and the variety of molecular structures produced.

Evaluation of Barley and Wheat Germplasm for Resistance to Head Blight and Mycotoxin Production by Fusarium asiaticum and F. graminearum.

Fusarium head blight (FHB) is one of the most serious diseases in barley and wheat, as it is usually accompanied by the production of harmful mycotoxins in the grains. To identify FHB-resistant breeding resources, we evaluated 60 elite germplasm accessions of barley (24) and wheat (36) for FHB and mycotoxin accumulation. Assessments were performed in a greenhouse and five heads per accession were inoculated with both Fusarium asiaticum (Fa73, nivalenol producer) and F. graminearum (Fg39, deoxynivalenol producer) strains. While the accessions varied in disease severity and mycotoxin production, four wheat and one barley showed <20% FHB severity repeatedly by both strains. Mycotoxin levels in these accessions ranged up to 3.9 mg/kg. FHB severity was generally higher in barley than in wheat, and Fa73 was more aggressive in both crops than Fg39. Fg39 itself, however, was more aggressive toward wheat and produced more mycotoxin in wheat than in barley. FHB severity by Fa73 and Fg39 were moderately correlated in both crops (r = 0.57/0.60 in barley and 0.42/0.58 in wheat). FHB severity and toxin production were also correlated in both crops, with a stronger correlation for Fa73 (r = 0.42/0.82 in barley, 0.70 in wheat) than for Fg39.

STUDY THE PRODUCTION OF PEDIOCIN BY PEDIOCOCCUS ACIDILACTICI IN REPEATED FED-BATCH FERMENTATION MODE ON MEAT PROCESSING WASTE

Objective: The production of pediocin has been studied in a repeated fed-batch reactor with intermittent feeding. The producer strain of pediocin was Pediococcus acidilctici. Meat processing waste was used as nutrient in growth media. Methods: Repeated fed-batch fermentation has been conducted in a bioreactor with three recycle ratio, such as 0.1, 0.2 and 0.3. A mathematical model has been developed for the prediction of reactor behaviour. The antimicrobial activity of pediocin was expressed as arbitrary units per millilitre (AU/ml). The concentrations of biomass, lactic acid, glucose and protein have also been measured with respect to time. Results: The experimental results were matched well with predicted data. The correlation coefficient (R2) was in between 0.95 to 0.97. The maximum productivity of pediocin was obtained 457,200 AU/h for 0.2 recycle ratio. Conclusion: The model was validated for high-accuracy prediction. The study should be applicable for large-scale pediocin production.