Browsing by Author "Aziz R.K."

Now showing 1 - 2 of 2

Biofilm formation in enterococci: Genotype-phenotype correlations and inhibition by vancomycin
(Nature Publishing Group, 2017) Hashem Y.A.; Amin H.M.; Essam T.M.; Yassin A.S.; Aziz R.K.; Department of Microbiology and Immunology; Faculty of Pharmacy; British University in Egypt (BUE); Shorouk City; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; October University for Modern Sciences and Arts; 6 October City; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; Cairo University; Cairo; Egypt
Enterococci are nosocomial pathogens that can form biofilms, which contribute to their virulence and antibiotic resistance. Although many genes involved in biofilm formation have been defined, their distribution among enterococci has not been comprehensively studied on a genome scale, and their diagnostic ability to predict biofilm phenotypes is not fully established. Here, we assessed the biofilm-forming ability of 90 enterococcal clinical isolates. Major patterns of virulence gene distribution in enterococcal genomes were identified, and the differentiating virulence genes were screened by polymerase chain reaction (PCR) in 31 of the clinical isolates. We found that detection of gelE in Enterococcus faecalis is not sufficient to predict gelatinase activity unless fsrAB, or fsrB alone, is PCR-positive (P = 0.0026 and 0.0012, respectively). We also found that agg is significantly enriched in isolates with medium and strong biofilm formation ability (P = 0.0026). Additionally, vancomycin, applied at sub minimal inhibitory concentrations, inhibited biofilm in four out of five strong biofilm-forming isolates. In conclusion, we suggest using agg and fsrB genes, together with the previously established gelE, for better prediction of biofilm strength and gelatinase activity, respectively. Future studies should explore the mechanism of biofilm inhibition by vancomycin and its possible use for antivirulence therapy. � 2017 The Author(s).
Thermal stability of a mercuric reductase from the Red Sea Atlantis II hot brine environment as analyzed by site-directed mutagenesis
(American Society for Microbiology, 2019) Maged M.; Hosseiny A.E.; Saadeldin M.K.; Aziz R.K.; Ramadan E.; Department of Biology; School of Sciences and Engineering; The American University in Cairo; New Cairo; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; Cairo University; Cairo; Egypt; Faculty of Pharmacy; The British University in Egypt (BUE); El Shorouk; Egypt; Science and Technology Research Center; School of Sciences and Engineering; The American University in Cairo; New Cairo; Egypt; Faculty of Biotechnology; October University for Modern Sciences and Arts; 6th October City; Cairo; Egypt
The lower convective layer (LCL) of the Atlantis II brine pool of the Red Sea is a unique environment in terms of high salinity, temperature, and high concentrations of heavy metals. Mercuric reductase enzymes functional in such extreme conditions could be considered a potential tool in the environmental detoxification of mercurial poisoning and might alleviate ecological hazards in the mining industry. Here, we constructed a mercuric reductase library from Atlantis II, from which we identified genes encoding two thermostable mercuric reductase (MerA) isoforms: one is halophilic (designated ATII-LCL) while the other is not (designated ATII-LCLNH). The ATII-LCL MerA has a short motif composed of four aspartic acids (4D414- 417) and two characteristic signature boxes that played a crucial role in its thermal stability. To further understand the mechanism behind the thermostability of the two studied enzymes, we mutated the isoform ATII-LCL-NH and found that the substitution of 2 aspartic acids (2D) at positions 415 and 416 enhanced the thermal stability, while other mutations had the opposite effect. The 2D mutant showed superior thermal tolerance, as it retained 81% of its activity after 10 min of incubation at 70�C. A three-dimensional structure prediction revealed newly formed salt bridges and H bonds in the 2D mutant compared to the parent molecule. To the best of our knowledge, this study is the first to rationally design a mercuric reductase with enhanced thermal stability, which we propose to have a strong potential in the bioremediation of mercurial poisoning. � 2019 American Society for Microbiology.