Nabil A. Hegazi

Production of biofertilizers using baker's yeast effluent and their application to wheat and barley grown in north Sinai deserts

Abstract Effluent from the bakers yeast industry was experimented on as a culture medium for the growth and biomass production of diazotrophs. The effluent supported good growth of Azotobacter chroococcum, Enterobacter agglomerans and Klebsiella pneuomoniae, Azospirillum brasilense, Bacillus polymyxa and Pseudomonas putida and strongly proposed for biofertilizers production of associative diazotrophs. Slurry preparations containing natural polymers, e.g. Arabic gum (5%), pero-dextrin (20%), starch granules (10%) or gelatine (20%) were impregnated with cells of tested diazotrophs. With storage, entrapped cells of B. polymyxa were viable up to 160 days, while gradual decreases in Azospirillum numbers were recorded. Pero-dextrin, a by-product of the starch industry, was selected as the appropriate biocarrier accommodating diazotroph cells and maintaining prolonged survival rates and nitrogenase activity. Cell cultures of A. brasilense, A. chroococcum, B. polymyxa, E. agglomerans and P. putida were equally mixed and entrapped into pero-dextrin slurry biofertilizer formulation named as “BIOGRAMINA”. Tested diazotrophs successfully survived (ca. 108 cfu ml−1) in such formulation up to 6 months at both ambient and cold temperatures. The response of wheat and barley to “BIOGRAMINA” in the presence or absence of N fertilizers was evaluated in greenhouse and field trials. Highest total biological yields were recorded for inoculated plants simultaneously supplemented with rational N fertilizer dose.

Diversity of bacteria nesting the plant cover of north Sinai deserts, Egypt

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 effect of some pesticides on asymbiotic N2-fixation in Egyptian soil

The effect of the application of a group of pesticides (Temik®, Stomp®, Dinoseb, Nata®, Dursban®, and Simazine 1 on N2-ase activity in Giza clay-loam soil under maize cultivation was investigated in the presence of 1 to 2% glucose or malate amendments. Field concentrations of all pesticides showed different inhibitory effects, and the effects increased with increased doses (10-and 100-fold) and incubation period (11 days). Temik and Stomp more seriously inhibited N2-ase activity than Dinoseb and Nata; Simazine and Dursban had the lowest effect. The effect of the field dose of Stomp on the patterns of N2-ase activity and development of N2-fixing spirilla and azotobacters in soil amended with glucose or malate was followed for a period of one month. Inhibitory effects on N2-ase activity as well as numbers of asymbiotic N2-fixers were marked during the first week of incubation, followed by a step wise recovery to normal levels by the end of the experiment. The deleterious effect of the tested pesticides was repeated in pure cultures of certain isolates of N2-fixing spirilla and azotobacters.

Biodiversity of diazotrophs associated to the plant cover of north sinai deserts: Biodiversität diazotropher assoziiert mit der pflanendecke der wüsten nordsinais

Efforts are made to record biodiversity of microflora and diazotrophs associated with the plant cover of the major agricultural development areas in north Sinai, around the El-Salam canal, a newly-constructed canal that brings Nile water westward across the Suez canal. Natural plant communities were collected from three major areas. Ectorhizosphere, endorhizosphere and phyllosphere samples were examined for total microbial population and diazotrophs. The vegetation of South Qantara (area I) is characterized by the dominance of Stipagrostis scoparia followed by Nitraria retusa, Convolvulus lanatus, Cornulaca monacantha and Filago desertorum. Rabaa-Bir El Abd (area II) is dominated by Artemisia monosperma, Panicum turgidum and Zygophyllum album. Euphorbia terracina, Oligomeris linifolia, Astragalus kahiricus, Hyoscyamus muticus and Thymelea hirsuta represent the major plants of El Ser and Al Quarir (area III). Microorganisms colonized root surfaces of all tested plants ranging from > 105 to 1010 cfu g − 1. Diazotrophs were common residents (1010 cfu g − 1), invaded the root tissue and established endophytically (102 – 106 cfu g − 1). Fifty-one N2-fixing isolates were obtained. Among the 32 bacilli isolates, Bacillus polymyxa and Bacillus circulans were more common compared to Bacillus macerans. BNF Gram-negative isolates belonged to Enterobacter agglomerans, Enterobacter gergoviae, Enterobacter amnigenus, Klebsiella pneumoniae, Pseudomonas luteola, Pseudomonas cepacia, Agrobacterium radiobacter and Azospirillum spp.

Plant-based culture media: Efficiently support culturing rhizobacteria and correctly mirror their in-situ diversity

Our previous publications and the data presented here provide evidences on the ability of plant-based culture media to optimize the cultivability of rhizobacteria and to support their recovery from plant-soil environments. Compared to the tested chemically-synthetic culture media (e.g. nutrient agar and N-deficient combined-carbon sources media), slurry homogenates, crude saps, juices and powders of cactus (Opuntia ficus-indica) and succulent plants (Aloe vera and Aloe arborescens) were rich enough to support growth of rhizobacteria. Representative isolates of Enterobacter spp., Klebsiella spp., Bacillus spp. and Azospirillum spp. exhibited good growth on agar plates of such plant-based culture media. Cell growth and biomass production in liquid batch cultures were comparable to those reported with the synthetic culture media. In addition, the tested plant-based culture media efficiently recovered populations of rhizobacteria associated to plant roots. Culturable populations of >106–108 cfu g−1 were recovered from the ecto- and endo-rhizospheres of tested host plants. More than 100 endophytic culture-dependent isolates were secured and subjected to morphophysiological identification. Factor and cluster analyses indicated the unique community structure, on species, genera, class and phyla levels, of the culturable population recovered with plant-based culture media, being distinct from that obtained with the chemically-synthetic culture media. Proteobacteria were the dominant (78.8%) on plant-based agar culture medium compared to only 31% on nutrient agar, while Firmicutes prevailed on nutrient agar (69%) compared to the plant-based agar culture media (18.2%). Bacteroidetes, represented by Chryseobacterium indologenes, was only reported (3%) among the culturable rhizobacteria community of the plant-based agar culture medium.

Bio-preparates support the productivity of potato plants grown under desert farming conditions of north Sinai: Five years of field trials

Organic agriculture as well as good agricultural practices (GAPs) intrigues the concern of both consumers and producers of agricultural commodities. Bio-preparates of various rhizospheric microorganisms (RMOs) are potential sources of biological inputs supporting plant nutrition and health. The response of open-field potatoes to the application of RMO bio-preparates, the biofertilizer “Biofertile” and the bioagent “Biocontrol”, were experimented over 5 successive years under N-hunger of north Sinai desert soils. Both vegetative and tuber yields of a number of tested cultivars were significantly improved due to rhizobacterial treatments. In the majority of cases, the biofertilizer “Biofertile” did successfully supply ca. 50% of plant N requirements, as the yield of full N-fertilized plants was comparable to those received 50% N simultaneously with bio-preparates treatment. The magnitude of inoculation was cultivar-dependent; cvs. Valor and Oceania were among the most responsive ones. Bio-preparate introduction to the plant–soil system was successful via soaking of tubers and/or spraying the plant canopy. The “Biocontrol” formulation was supportive in controlling plant pathogens and significantly increased the fruit yields. The cumulative effect of both bio-preparates resulted in tuber yield increases of ca. 25% over control.

Effect of incorporation of crop residues on development of diazotrophs and patterns of acetylene-reducing activity in Nile Valley soils

Acetylene-reducing activity and populations of diazotrophs were estimated simultaneously in Giza soils after harvest of wheat and maize crops. Amendment of soil with residues of either crop together with flood irrigation enhanced the development of diazotrophs and nitrogenase activities in the soil. Bacterial numbers and acetylene-reducing activity decreased as soils dried following flood irrigation. Activities decreased progressively with each cycle of irrigation following the original incorporation of organic matter. Nitrogenase activity in the soil was greater in the cooler winter than in summer.

Plant powder teabags: a novel and practical approach to resolve culturability and diversity of rhizobacteria.

We have developed teabags packed with dehydrated plant powders, without any supplements, for preparation of plant infusions necessary to develop media for culturing rhizobacteria. These bacteria are efficiently cultivated on such plant teabag culture media, with better progressive in situ recoverability compared to standard chemically synthetic culture media. Combining various plant-based culture media and incubation conditions enabled us to resolve unique denaturing gradient gel electrophoresis (DGGE) bands that were not resolved by tested standard culture media. Based on polymerase chain reaction PCR-DGGE of 16S rDNA fingerprints and sequencing, the plant teabag culture media supported higher diversity and significant increases in the richness of endo-rhizobacteria, namely Gammaproteobacteria (Enterobacteriaceae) and predominantly Alphaproteobacteria (Rhizobiaceae). This culminated in greater retrieval of the rhizobacteria taxa associated with the plant roots. We conclude that the plant teabag culture medium by itself, without any nutritional supplements, is sufficient and efficient for recovering and mirroring the complex and diverse communities of rhizobacteria. Our message to fellow microbial ecologists is: simply dehydrate your plant canopy, teabag it and soak it to prepare your culture media, with no need for any additional supplementary nutrients.

Biodiversity of microorganisms in semi-arid soils of north sinai deserts

North Sinai environment is currently subjected to changes due to the major agricultural development project of El-Salam canal which brings Nile water to the arid deserts of Sinai. Therefore, intensive efforts are made to record biodiversity of natural microflora and diazotrophs associated to the plant-soil system of the major agricultural development areas around the canal. Fourteen soil profiles were made, during the seasons 1997-2000, representing major sites of the area investigated (South Qantara, Rabaa-Bir El-Abd and El-Ser and Al-Quarir). Physico-chemical and microbiological properties of soils tested are presented. Microbiological profiling included total population of Gram positive and Gram negative bacteria, sporeformers, thermophiles, diazotrophs and spore-forming diazotrophs. Results obtained are discussed to relate physico-chemical properties to soil biofertility in an effort to categorize general fertility levels of soils under investigation.

Biological nitrogen fixation to maximize productivity of intercropped legumes and non‐legumes: Ten years of field experimentations in semi‐arid deserts of egypt

A number of field trials was executed in semi‐arid deserts of Ismailia, Egypt, to experiment growth and productivity of sole or mixed canopies of legumes (soybean, leucaena, sesbania, berseem and grasspea) and non‐legumes (corn, Rhodes grass, elephant grass, ryegrass and barley) when inoculated with N2‐fixing bacteria (diazotrophs) in presence or absence of N fertilizers. An average estimate of > 20 Kg N acre−1 was transferred to neighbouring unfertilized corn, and land equivalent ratio (LER) reached 1.35. Rhodes grass mixed with sesbania or leucaena produced higher biomass yield compared to pure N‐fertilized stands; increases of 66–91% and 22–29% were reported for inoculated and non‐inoculated plants respectively. In mixed canopy with berseem, dry matter yield of the non‐legume partner increased compared to that in pure stands, being higher for barley (120–255%) compared to ryegrass (62–115%). Similar trends were scored with N yield. Response of elephant grass to inoculation with associative diazotrophs was more pronounced when intercropped with leucaena as increases over pure stand in dry matter production approximated 40%. On the other hand, both grasspea and barley were negatively affected by intercropping. Total biomass and N‐yields of barley were more affected than grasspea.