RESUMEN
Heavy metals are considered as dangerous pollutants even in relatively low concentrations. Biosorption is an ecofriendly technology that uses microbial biomasses for adsorbing heavy metals from wastewater on their surfaces based on physicochemical pathways. Ten agricultural wastewater samples were collected from different sites in Sohag Governorate, Egypt. One hundred and nineteen zinc and cadmium-resistant bacterial isolates were recovered from the water samples. Interestingly, the isolate R1 was selected as the most resistant to Zn2+ and Cd2+. This isolate was morphologically and biochemically characterized and identified by sequencing of 16S rRNA gene as Priestia megaterium, and then deposited in the GenBank database under the accession number PRJNA526404. Studying the effects of pH and contact time on the biosorption process revealed that the maximum biosorption was achieved within 50 min at pH 7 and 8 for Zn2+ and Cd2+, respectively, by the living and lyophelized biomass of Priestia megaterium PRJNA526404. The preliminary characterization of the main chemical groups present on the cell wall, which are responsible for heavy metal biosorption, was performed by Infrared analysis (IR). Kinetics studies revealed that data were fitted towards the models hypothesized by Langmuir and Freundlich isotherm equations. The maximum capacity values (qmax) for biosorption of zinc and cadmium reached by using living and lyophelized biomass were 196.08; 227.27 and 178.57; 212.777 mg/g, respectively, and it was indicated that lyophilization improved efficiency of the biomass to heavy metals compared to living cells. The results indicated that Priestia megaterium PRJNA526404 had good application prospect in cadmium and zinc water remediation.
RESUMEN
Contamination by heavy metals is one of the major environmental problems in many countries and these contaminants reach from various sources such as traffic cars and other activities. Soil and phylloplane samples were collected from eight traffic and two non-traffic sites in Sohag city, Egypt. Heavy metal contents of Cd²âº, Zn²âº and Pb²âº of soil and phylloplane samples were determined and revealed high levels of Zn²âº and Pb²âº in traffic samples. A total of 112 bacterial and 62 fungal isolates were obtained from soil and phylloplane. Bacterial isolates were characterized on the basis of morphological, physicochemical and biochemical characteristics; and 16S rRNA gene sequences. Fungal isolates were identified according to morphological characterization. Minimal inhibitory concentrations (MICs) of Cd²âº, Zn²âº and Pb²âº for each isolate were detected. All bacterial and fungal isolates demonstrated resistance to lead with MICs >0.528 mM and >0.211, respectively. Moreover, the maximum MICs of cadmium and zinc for bacteria were 0.821 mM and 1.471 mM, respectively, where as, MICs for fungi were 0.328 mM and 0.588 mM, respectively. The most resistant bacterial and fungal isolates were Pseudomonas aeruginosa RA65 and Penicillium corylophyllum, respectively. Therefore, P. aeruginosa RA65 was selected for further investigations. Growth curve study showed that 0.264 mM lead had no efficiently effect on the growth of P. aeruginosa RA65. Plasmid isolation evidenced by transformation studies indicated that P. aeruginosa RA65 harbored a single plasmid (~9.5 kb) which mediated heavy meal resistance. Consequently, these microbial isolates could be potentially used in bioremediation of heavy metal-contaminated environment.
Asunto(s)
Bacterias/aislamiento & purificación , Hongos/aislamiento & purificación , Metales Pesados/farmacología , Hojas de la Planta/química , Pseudomonas aeruginosa/aislamiento & purificación , Microbiología del Suelo , Suelo/química , Bacterias/efectos de los fármacos , Biodegradación Ambiental , Cadmio/análisis , Cadmio/farmacología , Egipto , Hongos/efectos de los fármacos , Plomo/análisis , Plomo/farmacología , Metales Pesados/análisis , Pruebas de Sensibilidad Microbiana , Penicillium/efectos de los fármacos , Penicillium/aislamiento & purificación , Hojas de la Planta/microbiología , Plásmidos , Pseudomonas aeruginosa/efectos de los fármacos , ARN Ribosómico 16S , Contaminantes del Suelo/análisis , Contaminantes del Suelo/farmacología , Zinc/análisis , Zinc/farmacologíaRESUMEN
Solar-degrading bacteria, Pseudomonas aeruginosa strains, were isolated from Egyptian soil by Mineral Salt Medium (MSM) supplemented with Solar (motor fuel) from different oil-contaminated sites in Sohag province. The strain AA301 of Pseudomonas aeruginosa showed appreciable growth in MSM medium containing high concentrations of Solar ranging from 0.5 to 3% (v/v), with optimum concentration at 1.5%. Solar was used as a sole carbon source and a source of energy by the bacterium. The ability to degrade Solar was found to be associated with a single 60-kb plasmid designated pSOL15. The plasmid-cured variant, which was obtained by culturing in LB broth with kanamycin, lost the plasmid indicative the ability to degrade Solar must depend on this plasmid. The wild type isolate, Pseudomonas aeruginosa AA301 and transformant strain, have maximum growth (OD600 = approximately 2) on Solar, however the plasmid-cured variant did not have any significant growth on Solar. Moreover, resistance to a wide range of heavy metals such as Mn2+, Hg2+, Mg2+, Cd2+, Zn2+, and Ni2+ was also 60-kb plasmid-mediated. Therefore, the strain AA301 could be good candidate for remediation of some heavy metals and oil hydrocarbons in heavily polluted sites.