Abdel-Wahab Elsadek El-Enany

Cyanobacteria as a biosorbent of heavy metals in sewage water

The effect of sewage water on some physiological activities of cyanobacteria was studied. Metal-tolerant cyanobacterium (Nostoc linckia) and metal-sensitive (Nostoc rivularis) were grown at three levels of sewage water (25, 50 and 75%). The growth rate showed significant stimulation in low and moderate levels (50% for N. linckia and 25% for N. rivularis). Not only the number of cells was elevated but also, the time required to reach the exponential and the stationary phases was reduced. Also, low levels of sewage water increased chl.a content, photosynthetic O(2)-evolution, respiration and protein content. Similarly, heterocyst frequency as well as nitrogenase activity were increased in cyanobacteria grown at low and moderate levels (25 and 50% sewage). On the other hand, the high level of waste (75%) reduced growth and metabolic activities of the two species. N. linckia accumulated about 30-fold of Zn and ten-fold of Cd than those of growth medium (50% sewage water). Also, N. rivularis accumulated about ten-fold of Zn and two-fold of Cd. The distribution of Cd and Zn in cells were investigated. About 65-60% of Cd or Zn were found in pellets (sediment) as insoluble form in the two species. The soluble form (cytosolic fraction) after being fractionated on sephadex G-(75-100) revealed two peaks with molecular weights of 70-75 and 40-45 kDa. These peaks were in coincidence with Cd and Zn maxima. Nostoc rivulais showed more sensitivity to heavy metals than N. linckia, and accumulated less amount of metal-binding proteins. Nostoc linckia seems to be tolerant to heavy metals (Zn and Cd) and is able to accumulate this metal by adsorption on the pellets (cell surface) and/or through sequestration via metal-binding protein. Therefore it can be recommended it to be employed in the purification of waste contaminated with these heavy metals.

Effect of NaCl salinity on growth, pigment and mineral element contents, and gas exchange of broad bean and pea plants

Increasing salinity of growth medium induced a reduction in growth and transpiration rate. The concentrations of chlorophylls and carotenoids were increased in most cases in broad bean leaves while in pea plants they remained more or less unchanged with the rise of salinization up to 80mM NaCl. Thereabove a significant decrease in these contents was observed. A stimulation of the net photosynthetic rate of pea was observed at the lowest levels of NaCl but at the highest levels inhibitory effect was recorded. In broad bean all salinization levels inhibited photosynthetic activity, but dark respiration of both plant species was stimulated. The content of Na+ in the roots and shoots of both species increased at increasing salinity. In broad bean, Ca2+ concentration in shoots and K+ and Ca2+ contents of roots increased at increasing salinization, while in pea plants, the content of K+ and Ca2+ was almost unaffected by salinity. Salinity induced an increase in the content of these ions in pea roots. Mg2+ content in shoots and roots of both broad bean and pea decreased at increasing salinity except in roots of pea, where it was generally increased.

Synergistic interaction of Rhizobium leguminosarum bv. viciae and arbuscular mycorrhizal fungi as a plant growth promoting biofertilizers for faba bean (Vicia faba L.) in alkaline soil

Egyptian soils are generally characterized by slightly alkaline to alkaline pH values (7.5-8.7) which are mainly due to its dry environment. In arid and semi-arid regions, salts are less concentrated and sodium dominates in carbonate and bicarbonate forms, which enhance the formation of alkaline soils. Alkaline soils have fertility problems due to poor physical properties which adversely affect the growth and the yield of crops. Therefore, this study was devoted to investigating the synergistic interaction of Rhizobium and arbuscular mycorrhizal fungi for improving growth of faba bean grown in alkaline soil. A total of 20 rhizobial isolates and 4 species of arbuscular mycorrhizal fungi (AMF) were isolated. The rhizobial isolates were investigated for their ability to grow under alkaline stress. Out of 20 isolates 3 isolates were selected as tolerant isolates. These 3 rhizobial isolates were identified on the bases of the sequences of the gene encoding 16S rRNA and designated as Rhizobium sp. Egypt 16 (HM622137), Rhizobium sp. Egypt 27 (HM622138) and Rhizobium leguminosarum bv. viciae STDF-Egypt 19 (HM587713). The best alkaline tolerant was R. leguminosarum bv. viciae STDF-Egypt 19 (HM587713). The effect of R. leguminosarum bv. viciae STDF-Egypt 19 and mixture of AMF (Acaulospora laevis, Glomus geosporum, Glomus mosseae and Scutellospora armeniaca) both individually and in combination on nodulation, nitrogen fixation and growth of Vicia faba under alkalinity stress were assessed. A significant increase over control in number and mass of nodules, nitrogenase activity, leghaemoglobin content of nodule, mycorrhizal colonization, dry mass of root and shoot was recorded in dual inoculated plants than plants with individual inoculation. The enhancement of nitrogen fixation of faba bean could be attributed to AMF facilitating the mobilization of certain elements such as P, Fe, K and other minerals that involve in synthesis of nitrogenase and leghaemoglobin. Thus it is clear that the dual inoculation with Rhizobium and AMF biofertilizer is more effective for promoting growth of faba bean grown in alkaline soils than the individual treatment, reflecting the existence of synergistic relationships among the inoculants.

Role of kinetin in alleviation of copper and zinc toxicity in Lupinus termis plants

The effect of exogenous kinetin application on the growth and some physiological processes of Lupinus termis plants growing in metal containing solutions with excess concentrations of Cu and Zn ion were studied. Generally, plants growing in these solutions had a lower chlorophyll (Chl.) content, leaf relative water content (RWC) and produced less biomass than the control plants. Proline content was higher in metal-treated plants than in untreated controls. Chromatography of cell-free-extracts of roots and shoots indicated three main protein peaks with molecular weights about 170, 75--70 and 5--45 kDa. These peaks were coincident with Cu or Zn maxima. Addition of kinetin reduced the decline in Chl. content in metal-treated plants, improved water status of the plants and enhanced growth of the shoots and roots. The Cu or Zn content expressed on a per mg protein basis was raised when kinetin was applied to the growing shoots. Kinetin (Kin), Cu and Zn, singly and in the presence of kinetin (Cu × Kin and Zn × Kin), significantly affected the parameters tested. Only the effects of Cu × Kin and Zn × Kin interactions on shoot fresh weight and Cu × Kin on root length were statistically insignificant. Based on the calculated coefficient of determination (η2) the roles of Cu and Zn in affecting Chl. content and growth were dominant in comparison to kinetin. Kinetin effect was dominant for root length and proline content, but the role of the interaction was subdominant. The results of this study indicate that kinetin can alleviate the harmful effects of Cu and Zn on the growth of lupin plants through stimulation of Cu and Zn incorporation into metal-binding proteins.

Acetone-butanol-ethanol production from substandard and surplus dates by Egyptian native Clostridium strains.

One hundred and seven mesophilic isolates of Clostridium were isolated from agricultural soils cultivated with different plants in Assuit Governorate, Egypt. Eighty isolates (out of 107) showed the ability to produce ABE (Acetone, butanol and ethanol) on T6 medium ranging from 0.036 to 31.89 g/L. The highest numbers of ABE producing isolates were obtained from soil samples of potato contributing 27 isolates, followed by 18 isolates from wheat and 10 isolates from onion. On the other hand, there were three native isolates that produced ABE more than those produced by the reference isolate Clostridium acetobutylicum ATCC 824 (11.543 g/L). The three isolates were identified based on phenotypic and gene encoding 16S rRNA as Clostridium beijerinckii ASU10 (KF372577), Clostridium chauvoei ASU55 (KF372580) and Clostridium roseum ASU58 (KF372581). The highest ABE level from substandard and surplus dates was produced by C. beijerinckii ASU10 (24.07 g/L) comprising butanol 67.15% (16.16 g/L), acetone 30.73% (7.4 g/L) and ethanol 2.12% (0.51 g/L), while C. roseum ASU58 and C. chauvoei ASU55 produced ABE contributing 20.20 and 13.79 g/L, respectively. ABE production by C. acetobutylicum ATCC 824 was 15.01 g/L. This study proved that the native strains C. beijerinckii ASU10 and C. roseum ASU58 have high competitive efficacy on ABE production from economical substrate as substandard and surplus date fruits. Additionally, using this substrate without any nutritional components is considered to be a commercial substrate for desired ABE production.

ALLEVIATION OF CADMIUM TOXICITY ON MAIZE SEEDLINGS BY CALCIUM

The rate of germination, radicle and plumule length, fresh and dry mass of maize seedlings were increased as Ca2+ was added to the nutrient solution, which contained different levels of Cd2+, especially at low concentration of Ca2+ (5 mM) and high concentrations of Cd2+ (1.4 and 1.8 mM). The biosynthesis of pigments, respiration rate and content of soluble saccharides in endosperm were reduced sharply as the concentration of Cd2+ in the medium increased. This effects was alleviated by Ca2+ addition. Cd2+ content in seedlings was increased as the Cd2+ concentration in medium was increased and decreased sharply as Ca2+ was present in the culture medium. The study suggests liming of soil with CaCO3 to improve the yield of many crops.

Alleviating the inhibitory effect of salinity stress on nod gene expression in Rhizobium tibeticum – fenugreek (Trigonella foenum graecum) symbiosis by isoflavonoids treatment

Rhizobia-legume symbiosis depends on molecular dialog, which involves the production of specific plant flavonoid compounds as signal molecules. Rhizobium tibeticum was recovered from the root nodule of fenugreek and identified by sequencing the 16S rRNA gene. The effect of salinity stress on nod gene expression was measured in terms of β-galactosidase activity. R. tibeticum containing Escherichia coli lacZ gene fusions to specific nodulation (nod) genes were used to determine β-galactosidase activity. Combination of hesperetin (7.5 µM) and apigenin (7.5 µM) significantly increased β-galactosidase activity more than the single application of hesperetin or apigenin. Preincubation of R. tibeticum with hesperetin and apigenin combination significantly alleviates the adverse effect of salinity on nod gene expression and therefore, enhances nodulation and nitrogen fixation of fenugreek.

Interactive effects of plant hormones (GA3 or ABA) and salinity on growth and some metabolites of wheat seedlings

Pre-soaking wheat (Sakha 92) seeds in GA3 increased the germination potential especially at moderate salinization levels. On the other hand, ABA did not increase the germination potential of the tested seeds at all salinization levels. Fresh and dry matter yields of wheat seedlings decreased at high salinization levels and 90 mM NaCl represented the threshold of salinity. Pre-soaking wheat seeds in GA3 caused marked increases in fresh and dry matter yields of the salinized seedlings. While ABA treatment resulted in non-significant changes in dry matter production of stressed seedlings, the fresh matter production at most salinization levels tended to increase. GA3 or ABA treatment generally increased the soluble carbohydrates and total protein contents of salt stressed seedlings. The stimulatory effect of NaCl salinity on protein synthesis was additionally enhanced as a result of GA3 at all salinization levels or due to ABA treatment especially at high salt levels. The stimulatory effects of salt stress on the accumulation of free amino acids other than proline in the seedlings increased, with the application of GA3, while the activated synthesis of proline was partially attenuated. Application of GA3 was sufficient to attenuate partially the stimulatory effect of NaCl supply on proline biosynthesis, while ABA treatment failed to play this role.

Shoot regeneration and protein synthesis in tomato tissue cultures

Shoot regenerations from hypocotyls and cotyledons of tomato(Lycopersicon esculentum Mill.) was inhibited by NaCl (100 and 150 mM).Shoot fresh and dry masses were also reduced. Addition of proline (100 mgdm-3) counteracted the inhibitory effect of NaCl. SDS-PAGE analyses of extracted proteins, revealed that in cultures grown in medium with 25 mM NaCl plus proline, extra polypeptides of Mr 190, 58, 45 and 26 kDa accumulated. As NaCl was increased in the medium a new protein of Mr 67 kDa also accumulated.

Glutathione metabolism in soybean callus-cultures as affected by salinity

Induction and growth of soybean callus cultures were influenced by NaCl, especially at the highest concentration tested (150 mM). Protein content was raised as NaCl was increased in the Murashige and Skoog medium. Total sulfhydryl group (-SH) and glutathione (GSH) concentrations were also increased in NaCl treated cultures. The affinity (Km) of glutathione reductase (GR) for oxidized glutathione (GSSG) was gradually increased as NaCl level was raised in the medium. The GSH/GSSG ratio was raised significantly as the result of GR activity. The increase in GR activity may constitute an adaptive response of soybean callus to NaCl.