Expression of genes encoding cellulolytic enzymes in some Aspergillus species.

Fermentation is an important industrial process for microbial metabolite development and has wide applications in various fields. Aspergillus is the most important genus of fungi used for the production of microbial enzymes such as cellulase. The Aspergillus genome encodes various cellulolytic enzymes. In this study, we assayed the gene expression and cellulolytic enzyme production of three isolates: A. niger (KSU009), A. terreus (KC462061), and A. flavus (KSU014). Two fermentation systems, submerged fermentation and biofilm fermentation (BF), were used for this purpose. Gene expression analysis by RT-PCR showed that cbhB, exo, eglA, eglB, eglC, and ß-actin genes were differentially expressed in the two fermentation systems for these three isolates during enzyme production. Furthermore, the expression of all genes was found to be higher in the BF system. The six genes were not expressed in the isolates with no cellulolytic enzyme production. The isolates were identified by morphological and molecular methods, which were based on macroscopic characteristics and sequence analysis of ITS1, ITS2, and the 5.8S regions of rDNA.

Genetic diversity analysis of Aspergillus flavus isolates from plants and air by ISSR markers.

Aspergillus flavus is one of the most abundant and widely distributed fungi on earth. A. flavus produces aflatoxins (AFs), which are toxic secondary metabolites. AFs have harmful effects on public health (humans and animals) and agricultural crops. Inter-simple sequence repeat (ISSR) markers were used to analyze the genetic diversity of 30 A. flavus isolates from five agricultural crops and air. Genetic similarity coefficients (GSC) ranged from 0.51 to 0.10 based on three ISSR markers for the isolates tested. A. flavus isolates grouped into 6, 5, and 3 clusters using the unweighted pair-group method with arithmetic average of three ISSR markers. This study suggests that ISSR biotechnology is a highly useful tool for characterizing genetic diversity of A. flavus isolated from different sources.

Molecular characterization of Aspergillus flavus and aflatoxin contamination of wheat grains from Saudi Arabia.

Twelve species belonging to six fungal genera were found to be associated with wheat (Triticum aestivum L.) grain samples collected from three main regions in Saudi Arabia. The most common genera (average frequency) were Aspergillus (14.3%), Fusarium (29.1%), Penicillium (9.3%), and Alternaria (8.2%). Nineteen isolates of Aspergillus flavus were screened for their ability to produce aflatoxins using HPLC. Thirteen isolates produced aflatoxins ranging from 0.5 to 2.6 µg/kg. Inter-simple sequence repeats (ISSR), and random amplified polymorphic DNA (RAPD) molecular markers were used, with the aim of genetically characterizing strains of A. flavus to discriminate between aflatoxigenic and non-aflatoxigenic isolates. RAPD and ISSR analysis revealed a high level of genetic diversity in the A. flavus population, useful for genetic characterization. Clustering based on RAPD and ISSR dendograms was unrelated to geographic origin. RAPD and ISSR markers were not suitable to discriminate aflatoxigenic and non-aflatoxigenic isolates, but ISSR primers were better compared to RAPD.

Molecular characterization of the pathogenic plant fungus Rhizoctonia solani (Ceratobasidiaceae) isolated from Egypt based on protein and PCR-RAPD profiles.

Twenty-one isolates of Rhizoctonia solani were categorized into three anastomosis groups consisting of AG-4-HG-I (eight isolates), AG-2-2 (nine isolates) and AG-5 (four isolates). Their pathogenic capacities were tested on cotton cultivar Giza 86. Pre-emergence damping-off varied in response to the different isolates; however, the differences were not significant. Soluble proteins of the fungal isolates were electrophoresed using SDS-PAGE and gel electrophoreses. A dendrogram of the protein banding patterns by the UPGMA of arithmetic means placed the fungal isolates into distinct groups. There was no evidence of a relationship between protein dendrogram, anastomosis grouping or level of virulence or geographic origin. The dendrogram generated from these isolates based on PCR analysis with five RAPD-PCR primers showed high levels of genetic similarity among the isolates from the same geographical locations. There was partially relationship between the genetic similarity and AGs or level of virulence or geographic origin based on RAPD dendrogram. These results demonstrate that RAPD technique is a useful tool in determining the genetic characterization among isolates of R. solani.