Isolation and Identification of Antibiotic-Producing Halophilic Bacteria from Dagh Biarjmand and Haj Aligholi Salt Deserts, Iran

Background: Halophilic bacteria are potent organisms in production of novel bioactive antimicrobial compounds which might be considered in drug innovation and control of plant pathogens. Salt deserts in Semnan province are of the most permanent hypersaline areas in the North of Iran. Despite the importance of these areas, there is no scientific report regarding the biodiversity and potency of their halophilic bacteria. Thus, aforementioned areas were selected to detect the halophilic bacteria. Methods: Here, seven strains were isolated and cultured on their molecular and biochemical properties were characterized. To determine the antibiotic potency of the isolates, agar well diffusion method was conducted. Phylogenetic analysis was done to reveal the isolates relationship with previously known strains. Results: As a result, growth of the strains in the medium containing 5 to 20% (w/v) NaCl determined that the majority of the isolates were moderately halophile. Catalase activity of all strains was positive. The results represented that D6A, Dar and D8B have antimicrobial effects against different plant and human pathogens. Phylogenic tree analysis also showed that two strains of D6A and Dar are belonged to Bacillus subtilis and D8B is belonged to Virgibacillus olivae. The bacteria extracts were evaluated for their antifungal and antibacterial activities on human and Plant pathogenic strains. The MIC of the extract B. subtilis against was found active against human pathogenic fungi and Plant pathogenic bacteria and fungi, ranging from 12.5 to 25 µg/mL. Conclusion: This study highlights the therapeutic and prophylactic potential of B. subtilis extracts as antibacterial and antifungal agents

Data from: Migration patterns and changes in population biology associated with the worldwide spread of the oilseed rape pathogen Leptosphaeria maculans

Pathogen introductions into novel areas can lead to the emergence of new fungal diseases of plants. Understanding the origin, introduction pathways, possible changes in reproductive system and population size of fungal pathogens is essential in devising an integrated strategy for the control of these diseases. We used minisatellite markers to infer the worldwide invasion history of the fungal plant pathogen Leptosphaeria maculans, which causes stem canker (blackleg) of oilseed and vegetable brassicas. Clustering analyses partitioned genotypes into distinct populations corresponding to major geographic regions, along with two differentiated populations in Western Canada. Comparison of invasion scenarios using Approximate Bayesian Computation suggested an origin of the pathogen in the USA, the region where epidemics were first recorded, and independent introductions from there over the last few decades into Eastern Canada (Ontario), Europe and Australia. The population in Western Canada appeared to be founded from a source in Ontario and the population in Chile resulted from an admixture between multiple sources. A bottleneck was inferred for the introduction into Western Canada but not into Europe, Ontario or Australia. Clonality appeared high in Western Canada, possibly because environmental conditions there were less conducive to sexual reproduction. Leptosphaeria maculans is a model invasive pathogen with contrasting features in different regions: shallow population structure, high genetic variability and regular sexual recombination in some regions, by comparison with reduced genetic variability, high rates of asexual multiplication, strong population structure or admixture in others

AT-rich isochores as ecological niches for effectors in the genome of Leptosphaeria maculans

International audienceAT-rich isochores as ecological niches for effectors in the genome of Leptosphaeria maculans The genome of the ascomycete Leptosphaeria maculans shows the unusual characteristics to be organized in isochores. GC-equilibrated isochores (average 52% GC) are gene-rich whereas AT-rich isochores (40–43% GC) are mostly devoid of active sequences and are made up of mosaics of intermingled and degenerated repeated elements. The three avirulence (AvrLm) genes identified so far in this species are isolated in the middle of large AT-rich isochores. Our postulate thus was that AT-rich isochores were specific “ecological niches” for avirulence genes and effectors in L. maculans. This was firstly validated by analysis of three genes lying in the same genome environment (LmCys genes) and showing the same characteristics as AvrLm genes (low GC content, strong overexpression at the onset of plant infection, encoding for small secreted proteins -SSP- often rich in cysteines). Of these, one, LmCys2, was shown to act as an effector, probably contributing to suppression of plant defense. A systematic search for SPP as effector candidates was performed using bioinformatics. 455 AT-rich isochores were extracted from the genome data and their repeat content masked using the L. maculans repeat database. Non-repeated regions were then investigated with a pipe-line dedicated to the identification of SSP. This provided us with three datasets: 529 SSP-encoding genes in GC-equilibrated isochores, 498 non- SSP- and 122 SSP-encoding genes in AT-rich isochores. Part of this latter set of genes was analyzed for their occurrence in natural populations and expression data in culture and in planta. Finally, the 122 AT-SSP putative proteins showed structural features reminiscent of the AvrLm and LmCys genes. Possible diversification mechanisms as a function of genome location will be discussed

minisatellite data

Minisatellite data on each Leptosphaeria maculans individual [indiv ID, sampling location, genotype at the 14 minisatellite loci min 555, min632, mini967, mini1368, min1334, min1377, min1721, min1838, min2451, min935-, minLm3, minLm5, minLm6and minLm