title: Impact of bacterial biocontrol agents on aflatoxin biosynthetic genes, aflD and aflR expression, and phenotypic aflatoxin B₁ production by Aspergillus flavus under different environmental and nutritional regimes.
abstract: The objectives of this study were to examine the efficacy of four bacterial antagonists against Aspergillus flavus using 50:50 ratio of bacterial cells/conidia for the control of aflatoxin B1 (AFB1) production on two different nutritional matrices, nutrient and maize-based media at different water availabilities (0.98, 0.94 water activity (aw) on nutrient medium; 0.995, 0.98 aw on maize meal agar medium) at 35°C. The indicators of efficacy used were the relative expression of one structural and regulatory gene in the biosynthetic pathway (aflD and aflR respectively) and the production of AFB1. These studies showed that some of the bacterial species could significantly inhibit the relative expression of the aflD and aflR genes at both 0.98 and 0.94 aw on nutrient agar. On maize-based media some of the bacterial antagonists reduced the activity of both genes at 0.94 aw and some at 0.995 aw. However, the results for AFB1 production were not consistent with the effects on gene expression. Some bacterial species stimulated AFB1 production on both nutrient and maize-based media regardless of aw. However, some bacterial treatments did inhibit AFB1 production significantly when compared to the control. Overall, this study suggests that temporal studies are required on the biosynthetic genes under different environmental and nutritional conditions to evaluate the potential of antagonists to control AFB1.
authors.affiliation: University of Basrah, College of sciences, Dept. of Biology, Iraq.
authors.forename: Labeed A
authors.initials: LA
authors.lastname: Al-Saad
authors.affiliation: University of Basrah, College of sciences, Dept. of Biology, Iraq.
authors.forename: Adnan I
authors.initials: AI
authors.lastname: Al-Badran
authors.affiliation: University of Karbala, College of Applied Medical Sciences, Iraq.
authors.forename: Sami A
authors.initials: SA
authors.lastname: Al-Jumayli
authors.affiliation: Cranfield University, AgriFood Department, Applied Mycology Group, UK.
authors.forename: Naresh
authors.initials: N
authors.lastname: Magan
authors.affiliation: Cranfield University, AgriFood Department, Applied Mycology Group, UK. Electronic address: aliciarj@unex.es.
authors.forename: Alicia
authors.initials: A
authors.lastname: Rodríguez
mesh_terms: D016604:Aflatoxin B1 / Q000096:biosynthesis*; D001231:Aspergillus flavus / Q000254:growth & development / Q000378:metabolism*; D001412:Bacillus subtilis / Q000254:growth & development*; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D004777:Environment; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D005809:Genes, Regulator; D011551:Pseudomonas fluorescens / Q000254:growth & development*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014867:Water / Q000378:metabolism; D003313:Zea mays / Q000382:microbiology
chemical_list: C113837:AFLR protein, Aspergillus; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D014157:Transcription Factors; D014867:Water; D016604:Aflatoxin B1
keywords: Aflatoxin B(1); Aspergillus flavus; Bacillus subtilis; Gene expression; Pseudomonas fluorescens; Water activity; aflD; aflR