Performance of Pseudomonas spp. containing ACC-deaminase for improving growth and yield of maize (Zea mays L.) in the presence of nitrogenous fertilizer

Some plant-growth-promoting rhizobacteria (PGPR) promote plant growth by lowering the endogenous ethylene synthesis in the roots through their 1-aminocylopropane-1-carboxylate (ACC)-deaminase activity. However, in the vicinity of the roots may decrease the efficiency of these PGPR by stimulating ACC-oxidase activity resulting in greater ethylene production by the roots. This study was designed to assess the performance of PGPR containing ACC-deaminase for improving growth and yield of maize grown in N-amended soil. Several strains of rhizobacteria containing ACC-deaminase were screened for their growth-promoting activity in maize roots under gnotobiotic conditions. Six strains were selected and their effectiveness in soil amended with N at a concentration of 175 kg ha⁻¹ (1050 mg pot⁻¹) was investigated by conducting a pot trial on maize. Significant increases in plant height, root weight and total biomass were observed in response to inoculation. Based upon the results of pot trials, the three most efficient strains were selected and tested in the field for their effectiveness in the presence and absence of N fertilizer. Results of the field trial revealed that the inoculum performed relatively better in the absence of N-fertilizer application. Pseudomonas fluorescens biotype G (N₃) was the most effective strain both in the presence and absence of N fertilizer. Results may imply that even in the presence of optimum levels of nitrogenous fertilizers, inoculation with rhizobacteria containing ACC-deaminase activity could be effective to improve the growth and yield of inoculated plants.     

Congener-specific evaluation of biota-sediment accumulation factor model for HCHs and DDTs under small-scale in situ riverine condition

Purpose

The congener-specific biota-sediment accumulation factors (BSAFs) model for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) was evaluated for four different freshwater fish species (Orienus plagiostomus, Tor putitora, Glyptothorax punjabensis, and Cyprinus carpio) in in situ riverine conditions of Kabul River, Pakistan.

Materials and methods

The congeners of HCH and DDT were quantified using gas chromatograph (GC-ECD). The BSAF for each congener (HCHs and DDTs) was calculated from paired observation of congener’s measured concentrations in fish and sediment taken at the same site. Pearson’s correlation and linear regression analyses were performed to determine the influence of sediment organic carbon fraction (f _soc ) and organism lipid fraction (f _lipid ) on BSAF, and the relationship between BSAFs and logarithm of octanol-water partition coefficients (log K _ows) of HCH and DDT congeners, respectively.

Results and discussion

The BSAFs for total HCH (t-HCH) and total DDT (t-DDT) ranged from 0.6 to 1.5 and from 0.2 to 1.6, respectively. The model was significantly influenced by both fish (p = 0.004) and chemical types (p = 0.002) at 95 % confidence level. The sediment organic carbon fraction (f _soc ) and fish lipid fraction (f _lipid ) had not-too-weak effects on BSAF values for all fish species. The BSAF values were linearly fitted with logarithmic octanol-water partition coefficients (log K _ows) of HCH and DDT congeners, despite the different chemical structures, and different compound class significant negative correlations between log K _ows and BSAF values were found, indicating that hydrophobicity is one of the key factors influencing the bioaccumulation potential of the investigated compounds.

Conclusions

The present study confirmed the applicability of the BSAF model as a screening tool for predicting bioaccumulation of sediment-associated HCH and DDT congeners in investigated fish species under small-scale in situ riverine conditions of Kabul River and suite the model for benthic fish (G. punjabensis) on the basis of the 25th and 75th percentiles of congener-specific BSAF values.

     

Comparative effectiveness of Pseudomonas and Serratia sp. containing ACC-deaminase for coinoculation with Rhizobium leguminosarum to improve growth, nodulation, and yield of lentil

Three plant growth-promoting rhizobacteria strains containing ACC-deaminase (Pseudomonas jessenii, Pseudomonas fragi, and Serratia fonticola) and Rhizobium leguminosarum were selected and characterized by conducting some experiments under axenic condition. The selected isolates had the potential to improve the growth of lentil seedlings under axenic conditions. Pot and field experiments were conducted to evaluate the potential of these selected strains for improving growth and yield of lentil under natural conditions. A classical triple response (reduction of stem elongation, swelling of hypocotyle, and change in the direction of growth) bioassay was also conducted to evaluate the effect of high ethylene concentration on the growth of etiolated lentil seedlings, and the performance of coinoculation was evaluated to reduce the classical triple response in comparison with cobalt (Co²⁺), a chemical inhibitor of ethylene. Results showed that coinoculation of Pseudomonas and Serratia sp. with R. leguminosarum significantly increased the growth and yield of lentil. However, synergistic/coinoculation effect of P. jessenii with R. leguminosarum was more pronounced compared to that with P. fragi and S. fonticola. It increased the number of pods per plant, number of nodules per plant, dry nodule weight, grain yield, and straw yield up to 76%, 196%, 109%, 150%, and 164% under pot and up to 98%, 98%, 100%, 82%, and 78%, respectively, under field conditions as compared to uninoculated control. Similarly, combined inoculation significantly increased N concentration of grains under both pot and field conditions. The results from classical triple response assay showed that the effects of classical triple response decreased due to coinoculation in etiolated lentil seedlings and due to a decrease in the ethylene concentration. It is suggested that the strategy adopted by Pseudomonas sp. containing ACC-deaminase with Rhizobium to promote nodulation and yield by adjusting ethylene levels could be exploited as an effective tool for improving growth, nodulation, and yield of lentil.     

High rates of domestic sewage sludge on a calcareous soil and their effect on wheat growth using a pot experiment

A pot experiment was carried out to explore the use of high loading rates of domestic sewage sludge from Jeresh (Jordan) on a calcareous soil. Sludge was mixed with soil in volume ratios of 1:8, 1:6, 1:4, 1:2, 1:1, 2:1, and 4:1 with the unamended soil as a control. Wheat (Triticum durum L.) was grown in the pots for 60 days. The addition of sludge at a ratio of 1:8 increased wheat growth significantly; 1:6 ratio resulted in better growth than the control, although the increase was not significant at the 5% probability level. Other ratios suppressed wheat growth. The analysis of sludge-soil mixtures indicated that the addition of sludge increased the extractable P, K, Fe, Zn, Mn, and Cu in the mixtures. The addition of sludge to soil increased N and P in wheat tissue to optimum levels, but decreased K content. Iron and Zinc increased in wheat tissue due to the addition of sludge to soil, however Mn and Cu were not much affected.     

Comparative Analysis of CD4+ and CD8+ T Cells in Tumor Tissues,Lymph Nodes and the Peripheral Blood from Patients with Breast Cancer

Background: CD4+ and CD8+ T cells are the main types of lymphocytes in cell-mediated immunity and play a central role in the induction of efficient immune responses against tumors. The frequencies of T cell subtypes in the peripheral blood and tumor tissues, and draining lymph nodes (dLN) can be considered as useful markers for evaluation of the immune system in cancers. Methods: In this study, the frequencies of CD4+ and CD8+ T cells in blood, tumor tissues, and dLN samples of breast cancer patients were compared with each other and with similar tissues from normal individuals. Immunophenotyping was carried out by flow cytometry and the expression levels of CXCL10, granzyme B, and mammaglobin were evaluated by real-time PCR. Results: In the peripheral blood, there were no differences in the T cell subsets between the patients and the normal individuals. The frequency of CD8+ T cells was significantly higher in tumor tissue than normal breast tissues while granzyme B expression was similar. Based on mammaglobin expression levels, dLN have been classified into micro- and macro-metastatic dLN. We found significantly lower frequency of CD4+ in macro-metastatic dLN than micro-metastatic dLN. CD8+ frequency was similar in both dLN; however, granzyme B expression was higher in micro-metastatic ones. There was not any significant difference in CXCL10 expression between the two types of dLN. Conclusion: Based on our results, although the tumor does not affect the systemic immunity, tumoral cells affect the local immune system in the tumoral tissues and the metastatic dLN. Key Words: Breast neoplasms, CD4+ T lymphocyte, CD8+ T lymphocytes, CXCL10, Granzymes     

Effect of the nitrification inhibitor nitrapyrin on the fate of nitrogen applied to a soil incubated under laboratory conditions

The aim of this study was to examine the effect of the nitrification inhibitor nitrapyrin on the fate and recovery of fertilizer nitrogen (N) and on N mineralization from soil organic sources. Intact soil cores were collected from a grassland field. Diammonium phosphate (DAP) and urea were applied as N sources. Cores were equilibrated at –5 kPa matric potential and incubated at 20 °C for 42 to 56 days. Changes in NH₄⁺‐N, accumulation of NO₃^–‐N, apparent recovery of applied N, and emission of N₂O (acetylene was used to block N₂O reductase) were examined during the study. A significant increase in NH₄⁺‐N released through mineralization was recorded when nitrapyrin was added to the control soil without N fertilizer application. In the soils to which N was added either as urea or DAP, 50–90 % of the applied N disappeared from the NH₄⁺‐N pool. Some of this N (8–16 %) accumulated as NO₃^–‐N, while a small proportion of N (1 %) escaped as N₂O. Addition of nitrapyrin resulted in a decrease and delay of NH₄⁺‐N disappearance, accumulation of much lower soil NO₃^–‐N contents, a substantial reduction in N₂O emissions, and a 30–40 % increase in the apparent recovery of added N. The study indicates that N recovery can be increased by using the nitrification inhibitor nitrapyrin in grassland soils at moisture condition close to field capacity.     

Efficiency of Dry Matter and Nitrogen Accumulation and Redistribution in Wheat as Affected by Tillage and Nitrogen Management

Field experiments were conducted over 2 years with the hypothesis that farmyard manure (FYM), soybean residue (SR) as sole and/or in combination with urea under different tillage practices has similar effects on crop nitrogen (N) status and accumulation of dry matter (DM). Conventional ploughed plots had higher DM than other. Post anthesis accumulation of DM for minimum tillage (MT) was 4% higher than DT. Incorporation of 20 tons FYM ha^?1 combined with 30 or 60 kg ha^?1 had higher DM and N partitioned to leaves, stem, and spike than control. Leaves accumulated more DM at anthesis stage than other, whereas stem and spike at maturity than earlier stages. Fertilized plots had higher DM and N redistribution efficiency than control. However, N remobilization increased linearly with increasing DM accumulation (r² = 22%). It was concluded that FYM coupled with N under MT showed marked variations for DM partition and N status in wheat than other treatments.     

Application of redox mediator to accelerate selenate reduction to elemental selenium by Enterobacter taylorae

Acceleration of bacterial reduction of selenate [Se(VI)] to insoluble elemental Se [Se(0)] plays an important role in Se bioremediation. Anthraquinone-2,6-disulfonate (AQDS), a redox mediator, was assessed for its ability to enhance the reduction of Se(VI) (2000 microg/L) to Se(0) by Enterobacter taylorae in various media. The results showed that addition of AQDS did not increase Se(VI) reduction in the media containing 50 and 250 mg/L yeast extract, suggesting that E. taylorae cannot directly use anthrahydroquinone-2,6-disulfonate (AHQDS, a reduced form of AQDS) to respire Se(VI). An increase of yeast extract concentration from 50 to 250 mg/L in the medium dramatically enhanced the AQDS function for rapid reduction of selenite [Se(IV)] to Se(0). During an 8-day experiment, 85-91% of the added Se was reduced to Se(0) in the AQDS-amended medium in comparison to formation of 46% of Se(0) in the medium without AQDS. These results show that redox mediators have great application potential in bioremediation of Se in Se-contaminated water.