Diversity of rhizobacteria associated to plant roots as affected by culturing media and related methodology / Mohamed Sabry Mohamed Sarhan ; Supervised Nabil Abrahim Hegazi , Mohamed Fayez Fouad

Thesis (M.Sc..) - Cairo University - Faculty of Agriculture - Department of Microbiology

The crude plant slurry homogenates, juices and saps are found to support culturability and growth of rhizobacteria. For ease of application and practicability, here we present vegetative plant materials of trifolium alexandrinum, and paspalum vaginatumin the form of dehydrated powders and packed in teabags to obtain liquid infusions necessary to prepare culture media for rhizobacteria. The resulting plant based culture media supported very good growth of pure isolates of azotobacter spp., bacillus spp., burkholderia spp., enterobacter spp., klebsiella spp., and Psuedomonas spp. More importantly, they were capable to efficiently recover rhizobacteria associated to the roots of maize and clover. Quantitatively, the culturable rhizobacteria population developed on the plant based culture media represented 28-35% of the total bacteria cells detected by quantitative real-time PCR on root samples; compared to only 16-18% retrieved on the chemically-synthetic culture media (e.g. nutrient agar). PCR-DGGE of 16S rDNA amplicons and sequencing were used to compare the community composition of rhizobacteria cultured on both plant-based and chemically- synthetic culture media, as well as those obtained from plant roots. Highest diversity of rhizobacteria was detected on maize roots (shannon-wiener index, H=2.968), followed by CFUs cultured on plant-based culture media (H=2.662-2.685), and chemically-synthetic culture media (H=2.398). The PCR-DGGE band pattern composition was significantly different among rhizobacteria communities cultured on chemically-synthetic media and plant-based culture media, as well as those found on root samples

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