Efficiency of Saccharothrix algeriensis NRRL B-24137 and its produced antifungal dithiolopyrrolones compounds to suppress fusarium oxysporum-induced wilt disease occurring in some cultivated crops

Saccharothrix algeriensis NRRL B-24137 (SA) is a well-studied actinobacterium strain for its ability to produce numerous bioactive dithiolopyrrolone derivatives with appreciable antifungal properties. Our study aimed to investigate the possible usefulness of SA and its produced compounds to control several formae speciales of Fusarium oxysporum, which affect different important crops. Such is the case of F. oxysporum f. sp. lini (FOLi), F. oxysporum f. sp. lentis (FOLe), F. oxysporum f. sp. ciceris (FOC) and F. oxysporum f. sp. lycopersici (FOLy) which cause devastating wilt to flax, lentil, chickpea and tomato, respectively. Antagonistic properties of the strain SA have been primarily evaluated in vitro. This screening showed the significant antifusarium activity of the actinobacteria strain against FOLi, FOC, FOLe and FOLy. Consecutively, strain SA and FOLi soil development has been assessed. The SA soil treatment permitted an important decrease (threefold) in the FOLi infestation. Moreover, the actinobacteria soil density seemed maintained after 7-week treatment at an appreciable level of 44×106 CFU/gram of dry soil (gds). Through different pot experiments, soil pre-treatment with the SA strain significantly reduced the disease incidence of FOLi, FOLe, FOC and FOLy by 71.0, 73.3, 61.2 and 59.7%, respectively. However, the treatment with pure dithiolopyrrolones appeared less effective with about 50% of FOLi disease impact reduction, which thus suggested the involvement of more than direct antibiosis in the whole SA biocontrol performance. Globally, significant correlation between the in vitro antagonistic properties of SA and its capacity to reduce the disease occurrence (r=0.81, P≤0.05) has been highlighted

Saccharothrix algeriensis NRRL B-24137, the first non-Streptomyces actinobacterium, produces holomycin after cystine feeding

Saccharothrix algeriensis NRRL B-24137 is an actinobacterium isolated from Algerian Saharan soil. This strain has the ability to produce several dithiolopyrrolone antibiotic derivatives depending on the precursors added to the culture medium. This group of antibiotics is known for their potent antimicrobial and anticancer activities. Holomycin is a member of the dithiolopyrrolone group of antibiotics, and has already been isolated from several species of actinobacteria belonging to the genus Streptomyces and also from some Gram-negative bacteria. In this study, holomycin was produced for the first time in the culture broth of a non-Streptomyces actinobacteria. This antibiotic was induced by adding 5 mM of L-cystine as precursor to the semi-synthetic fermentation broth of Sa. algeriensis NRRL B-24137 and then fully identified after HPLC purification. The minimum inhibitory concentrations (MIC) of holomycin were determined against several pathogenic microorganisms, including Escherichia coli ATCC 10536 Klebsiella pneumoniae CIP 82.91, Listeria monocytogenes CIP 82110, Staphylococcus aureus CIP 7625, Aspergillus carbonarius M333, Fusarium culmorum FC1, Candida albicans IPA 200. This antibiotic showed a broad-spectrum antimicrobial activity, inhibiting a variety of Gram-positive and Gram-negative bacteria, and micro-fungi

Deoxynivalenol-producing ability of Fusarium culmorum strains and their impact on infecting barley in Algeria

The cereal-pathogenic Fusarium culmorum (W.G. Smith), causal agent of various blights and rot diseases, is considered as a chronic fungus of economic concern worldwide including North African countries such as Algeria. This pathogen produces a wide range of mycotoxins, amongst which the type B-trichothecene deoxynivalenol (DON). In addition to its acute and chronic side effects in livestock and humans, DON is believed to play a determinant role in the pathogenesis toward Triticeae. However, regardless its significant occurrence and impact, little is known about trichothecenes-producing ability of F. culmorum infecting cereals in Algeria. The PCR assay based on Tri genes of 12 F. culmorum strains (designated Fc1-Fc12), which were recovered from several cropping areas of North Algeria, revealed their trichothecenes-producing ability with 3-AcDON genotype. The molecular prediction was confirmed by HPLC analysis. All strains were able to produce the toxin at detectable levels. Strains Fc1 and Fc12 were the highest producers of this mycotoxin with 220 and 230 µg g(-1), respectively. The evaluation of pathogenic ability of strains through a barley infesting experiment exhibited the significant disease impact of most strains. Significant correlation between the DON-producing ability of strains and the increase in both disease severity (r = 0.88, P = 0.05) and disease occurrence (r = 0.70, P = 0.05) was observed. Chemotyping of F. culmorum isolates and evaluation of their pathogenic ability are reported for the first time for isolates from Algeria, and highlights the important potential of F. culmorum to contaminate cultivated cereal with DON trichothecenes

Biocontrol and plant growth promoting properties of Streptomyces mutabilis strain IA1 isolated from a Saharan soil on wheat seedlings and visualization of its niches of colonization

In this study, the biocontrol ability and colonization behavior of a highly antagonistic Streptomyces mutabilis strain, named IA1, recently isolated from a Saharan soil, were assessed on wheat seedlings. In this study we showed that strain IA1 secretes IAA and GA3 and is able to enhance growth of wheat seedlings. Using DOPE-FISH coupled with confocal laser scanning microscopy (CLSM), we observed moreover that following caryopsis inoculation and plant growth the strain can colonize the rhizoplane, the surface of caryopsis as well as the endorhiza, crossing from the rhizodermis up to the vascular system. Interestingly, further visualizations revealed that the actinobacterial strain could also be endophytic inside the caryopsis up to the endocarp layer (the dried fruit part, not the seed part of grain). Disease caused by Fusariumculmorum was further evaluated on seedlings and results showed that coated seeds with strain IA1 can reduce both disease occurrence (64.7%) and decrease severity (79.6%). This study showed that strain IA1 derived from a Saharan soil could protect a temperate crop from F. culmorum seedling blight, promote growth and colonize various niches on the surfaces of the phytosphere (roots, seeds) as well as plant endosphere compartments

A new dithiolopyrrolone antibiotic triggered by a long fermentation of Saccharothrix algeriensis NRRL B‐24137 in sorbic acid‐amended medium

Saccharothrix algeriensis NRRL B‐24137 is an actinobacterium isolated from Algerian Saharan soil. It produces bioactive compounds belonging to the dithiolopyrrolone class of antibiotics, which are characterized by the possession of a unique pyrrolinonodithiole nucleus. Dithiolopyrrolones are known for their strong antibacterial and antifungal activities. This class of antibiotics generated great interest after the discovery of their anticancer properties. In this study, an antibiotic named PR11, produced after a long bacterial fermentation (11 days) in sorbic acid‐containing culture broth, was characterized as a new dithiolopyrrolone derivative. After HPLC analysis and purification, the chemical structure of this antibiotic was determined by 1H‐ and 13C‐nuclear magnetic resonance, mass and UV‐visible data. PR11 was thus characterized as an iso‐hexanoyl‐pyrrothine, a novel dithiolopyrrolone derivative. The minimum inhibitory concentrations of the new induced antibiotic were determined against several pathogenic micro‐organisms. A moderate to strong activity was noted against all Gram‐positive bacteria, filamentous fungi and yeasts tested

Effective biosynthesis of benzoyl-pyrrothine dithiolopyrrolone antibiotic by cinnamic acid-precursor addition in culture of Saccharothrix algeriensis NRRL B-24137

Dithiolopyrrolone antibiotics, produced by several micro‐organisms, are known for their strong antimicrobial and antitumor activities. Among of this micro‐organisms, Saccharothrix algeriensis NRRL B‐24137, a rare actinobacterium, has the ability to produce several dithiolopyrrolones derivatives depending on precursors added in the culture medium. After 10 days of strain fermentation on semi‐synthetic medium supplemented with cinnamic acid and HPLC purification, biosynthesis of benzoyl‐pyrrothine dithiolopyrrolone was evidenced through complete spectroscopic (UV–visible and 1H and 13C NMR) and spectrometric (electron impact mass spectrum) analyses. The pure molecule showed appreciable minimum inhibitory concentration values against several Gram‐positive bacteria and filamentous fung

Early events induced by the toxin deoxynivalenol lead to programmed cell death in Nicotiana tabacum cells

Deoxynivalenol (DON) is a mycotoxin affecting animals and plants. This toxin synthesized by Fusarium culmorum and Fusarium graminearum is currently believed to play a decisive role in the fungal phytopathogenesis as a virulence factor. Using cultured cells of Nicotiana tabacum BY2, we showed that DON-induced programmed cell death (PCD) could require transcription and translation processes, in contrast to what was observed in animal cells. DON could induce different cross-linked pathways involving (i) reactive oxygen species (ROS) generation linked, at least partly, to a mitochondrial dysfunction and a transcriptional down-regulation of the alternative oxidase (Aox1) gene and (ii) regulation of ion channel activities participating in cell shrinkage, to achieve PCD