Identification and characterization of novel bacterial polyaromatic hydrocarbon-degrading enzymes as potential tools for cleaning up hydrocarbon pollutants from different environmental sources.

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant hazardous environmental contaminants. Various strategies, including chemical and physical like oxidation, fixation, leaching, and electrokinetic or biological-based techniques are used for remediation of polluted sites. Bioremediation of PAHs, via PAH-degrading endophytic and rhizospheric microbes, represent a time-/cost-effective way for ecorestoration. Four bacterial strains were isolated from contaminated soil on MSM supplemented with anthracene, alpha-naphthalene or catechol as sole carbon sources. These isolates were identified with 16S rRNA as Bacillus anthracis, B. cereus, B. mojavensis and B. subtilis. The degradation efficiency on the selected aromatic compounds was tested by HPLC analysis. B. subtilis showed the highest degradation efficiency of anthracene (99%) after five days of incubation. B. subtilis showed the highest catechol 1, 2 dioxygenase activity in MSM supplemented with anthracene. The enzyme was purified by gel filtration chromatography and characterized (70 kD, Km 2.7 µg and Vmax 178U/mg protein). The catechol 1,2 dioxygenase gene from the identified four bacterial strains were isolated and submitted to GenBank (accession numbers MG255165-MG255168). The gene expression level of catechol 1,2 dioxygenase was upregulated 23.2-fold during the 72 h of incubation period. Furthermore, B. subtilis is a promising strain to be used in bioremediation of aromatic compounds-contaminated environments.

An efficient and reproducible protocol for the production of salt tolerant transgenic wheat plants expressing the Arabidopsis AtNHX1 gene.

We present an efficient method for the production of transgenic salt tolerant hexaploid wheat plants expressing the Arabidopsis AtNHX1 gene. Wheat mature zygotic embryos were isolated from two hexaploid bread wheat (Triticum aestivum) cultivars (namely: Gemmeiza 9 and Gemmeiza 10) and were transformed with the A. tumefaciens LBA4404 harboring the pBI-121 vector containing the AtNHX1 gene. Transgenic wheat lines that express the gus intron was obtained and used as control. The results confirmed that npt-II gene could be transmitted and expressed in the T2 following 3:1 Mendelian segregation while the control plant couldn't. The data indicate that, the AtNHX1 gene was integrated in a stable manner into the wheat genome and the corresponding transcripts were expressed. The transformation efficiency was 5.7 and 7.5% for cultivars Gemmeiza 10 and Gemmeiza 9, respectively. A greenhouse experiment was conducted to investigate the effect of AtNHX1 gene in wheat salt tolerance. The transgenic wheat lines could maintain high growth rate under salt stress condition (350 mM NaCl) while the control plant couldn't. The results confirmed that Na(+)/H(+) antiporter gene AtNHX1 increased salt tolerance by increasing Na(+) accumulation and keeping K+/Na(+) balance. Thus, transgenic plants showed high tolerance to salt stress and can be considered as a new genetic resource in breeding programs.