Nabil Hegazi

North Sinai deserts were surveyed for the predominant plant cover and for the culturable bacteria nesting their roots and shoots. Among 43 plant species reported, 13 are perennial (e.g. Fagonia spp., Pancratium spp.) and 30 annuals (e.g. Bromus spp., Erodium spp.). Eleven species possessed rhizo-sheath, e.g. Cyperus capitatus, Panicum turgidum and Trisetaria koelerioides. Microbiological analyses demonstrated: the great diversity and richness of associated culturable bacteria, in particular nitrogen-fixing bacteria (diazotrophs); the majority of bacterial residents were of true and/or putative diazotrophic nature; the bacterial populations followed an increasing density gradient towards the root surfaces; sizeable populations were able to reside inside the root (endorhizosphere) and shoot (endophyllosphere) tissues. Three hundred bacterial isolates were secured from studied spheres. The majority of nitrogen-fixing bacilli isolates belonged to Bacillus megaterium,Bacillus pumilus, Bacillus polymexa,Bacillus macerans,Bacillus circulans and Bacillus licheniformis. The family Enterobacteriaceae represented by Enterobacter agglomerans,Enterobacter sackazakii, Enterobacter cloacae, Serratia adorifera,Serratia liquefaciens and Klebsiella oxytoca. The non-Enterobacteriaceae population was rich in Pantoae spp., Agrobacterium rdiobacter, Pseudomonas vesicularis, Pseudomonas putida, Stenotrophomonas maltophilia, Ochrobactrum anthropi, Sphingomonas paucimobilis and Chrysemonas luteola.Gluconacetobacter diazotrophicus were reported inside root and shoot tissues of a number of tested plants. The dense bacterial populations reported speak well to the very possible significant role played by the endophytic bacterial populations in the survival, in respect of nutrition and health, of existing plants. Such groups of diazotrophs are good candidates, as bio-preparates, to support the growth of future field crops grown in deserts of north Sinai and irrigated by the water of El-Salam canal.

The exclusive use of plant juices, not as a mere supplement to synthetic culture media, for culturing rhizospheric microorganisms (RMO) is introduced here. Juices were prepared from desert (Mesembryanthemum crystallinum L., Zygophyllum album L., Carpobrotus edulis L.) as well as cultivated (Trifolium alexandrinum L., Beta vulgaris L.) plants. Colonies of RMO (Azospirillum brasilense, Enterobacter agglomerans and Klebsiella pneumoniae) nicely developed on surface-inoculated agar plates prepared from crude and diluted juice of M. crystallinum (ice plant). Furthermore, hundreds of RMO colonies developed on various standard culture media were replicated (>90%) on agar plates of different plant juices. RMO cells grew nicely in liquid ice plant juice, with doubling times comparable to those grown in the reference culture medium. RMO populations resident in various host plants were able to develop on culture media prepared from homologous and heterologous juices. The application of a thin semi-solid overlay agar on the surfaces of inoculated agar plates significantly increased the recovery of micro-colonies on agar plates, particularly those prepared from plant juices.