The Comparative Study of telluride removal by a moderately halophilous bacterium, Halomonas elongate, a halotolerant bacterium, Enterococcus faecalis and a non-halophilous bacterium, Pseudomonas aeruginosa

Subject Areas : environmental management

Zeynab Sadat Motesharrei ¹ , Mohammad Ali Amoozegar ²

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Received: 2008-04-08 Accepted : 2008-08-31 Published : 2010-04-03

Keywords: Halomonas elongate DSM 2581, Enterococcus faecalis PTCC 123, Pseudomonas aeruginosa PTCC 10, tellurite, Selenooxyanions, arsenate,

Abstract :

Halophilous, halotolerant and non-halophilous microorganisms have important roles in bioremediation and transformation of toxic metal compounds in polluted environments. Identification of toxic metal-tolerant strains and their removal patterns are the first steps of applying them in the bioremediation processes. In the current study, telluride removal in three moderately halophilous, halotolerant and non-halophilous bacteria, Halomonas elongate DSM 2581, Enterococcus faecalis PTCC1237 and Pseudomonas aeruginosa PTCC1074, respectively, and the effects of selenooxyanions and arsenate on this removal, were determined by means of a colorimetric method using di-ethyl thio-carbamate. The strains H. elongate, E. faecalis and Ps. aeruginosa showed the maximum MIC to telluride as 0.25, 8 and 0.25 mM, respectively. In halophilous microorganism, H. elongata, selenooxyanions had a positive effect on increasing the telluride resistance, since K-telluride plus 25 mM  Na-Selenite or Na-selenate were added together into the medium, tolerance to telluride was increased from 0.25 mM to 18 mM and from 0.25 mM to 3 mM, respectively , telluride tolerance in halotolerant strain ,E. faecalis, in the presence of 25 mM Se (IV) or 5 mM Se (VI) or 0.1 mM As (V) was increased and reached to 80 mM , 16 mM and 16 mM , respectively,but in Non-halophilous bacterium, Ps. aeruginosa adding 25 mM Se (IV) or 5 mM Se (VI) or 5 mM As (V) did not cause increasing of MIC of telluride. The ability of halophilous strain to telluride removal was increased in comparison of control condition (medium containing of just telluride) by 48/21% and 25.74% , when 0.1 mM Te(IV) plus 50 mM Se (IV) or 1 mM Se (VI) was used respectively. 0.2 mM Te (IV) plus 1 mM Se (IV) or 1 mM Se (VI) or 0.1 mM As (V) in E. faecalis can give rise 2.2% , 7.33%  and 75% increase in Telluride removal, as well. The most positive effect of Selenite and Selenate in Telluride removal was observed in              H. elongata and the lowest of it was observed in E. faecalis. A unique characteristic of E. faecalis in removing of Tellurite by 75% in the presence of Arsenate was the thing which observed only in E. faecalis but not in two other bacteria studied here. In the case of P. aeruginosa, 8 mM Se (IV) or 1 mM Se (VI) plus 0.1 mM Te (IV) can also cause higher increase in telluride removal by 34.35% and 11.82%, respectively. X-ray fluorescence (XRF) studies and scanning transmission electron microscopy examination using an EDS analysis system, demonstrated that the black and red deposits formed in bacterial cells, was metallic tellurium and selenium