Cobalt separation by Alphaproteobacterium MTB-KTN90: magnetotactic bacteria in bioremediation.

Bioremediation of toxic metals by magnetotactic bacteria and magnetic separation of metal-loaded magnetotactic bacteria are of great interest. This bioprocess technique is rapid, efficient, economical, and environmentally friendly. In this study, cobalt removal potential of a novel isolated magnetotactic bacterium (Alphaproteobacterium MTB-KTN90) as a new biosorbent was investigated. The effects of various environmental parameters in the cobalt removal and the technique of magnetic separation of cobalt-loaded bacterial cells were studied. Cobalt removal by MTB-KTN90 was very sensitive to pH solution; higher biosorption capacity was observed around pH 6.5-7.0. When biomass concentration increased from 0.009 to 0.09 g/l, the biosorption efficiency increased from 13.87 % to 19.22 %. The sorption of cobalt by MTB-KTN90 was rapid during the first 15 min (859.17 mg/g dry weight). With the increasing of cobalt concentrations from 1 to 225 mg/l, the specific cobalt uptake increased. Maximum cobalt removal (1160.51 ± 15.42 mg/g dry weight) took place at optimum conditions; pH 7.0 with initial cobalt concentration of 115 mg/l at 60 min by 0.015 g/l of dry biomass. The results showed maximum values for constants of Langmuir and Freundlich models so far. The biosorption mechanisms were studied with FTIR, PIXE, and FESEM analysis. Cobalt-loaded MTB-KTN90 had ability to separate from solution by a simple magnetic separator. Magnetic response in MTB-KTN90 is due to the presence of unique intracellular magnetic nanoparticles (magnetosomes). The orientation magnetic separation results indicated that 88.55 % of cobalt was removed from solution. Consequently, Alphaproteobacterium MTB-KTN90 as a new biosorbent opens up good opportunities for the magnetic removal of cobalt from the polluted aquatic environments.

Isolation and Characterization of a Novel Magnetotactic Bacterium From Iran: Iron Uptake and Producing Magnetic Nanoparticles in Alphaproteobacterium MTB-KTN90.

BACKGROUND: Magnetotactic bacteria (MTB) have the ability to biomineralize unique intracellular magnetic nanosize particles. These bacteria and their magnetosomes are under special attraction because of their great useful potential in nano-biotechnological and biomedical applications. MTB are ubiquitous in aquatic environments, but their isolation and axenic cultivation in pure culture is very difficult and only a limited number of them have been isolated in pure culture. OBJECTIVES: The main goal of this study was screening, isolation and cultivation of a new strain of these fastidious bacteria in pure culture from Iran to use them and their magnetosomes. MATERIALS AND METHODS: Thirty samples were collected from various aquatic habitats. Most important physicochemical environmental factors that are involved in growth of MTB in the microcosms were investigated using inductively coupled plasma atomic emission spectroscopy (ICP-AES), portable dissolved oxygen meter, etc. Capillary racetrack technique and magnetic separation were used to purify and enrich MTB. Various isolation media were simultaneously used for isolation of a new magnetotactic bacterium in pure culture. Two imaging techniques were used to visualize the characterizations and cell division: transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM). Polymerase chain reaction (PCR), ChromasPro software and MEGA5 were applied for sequence analysis of the 16S rRNA gene. RESULTS: The results revealed a correlation of important physicochemical factors such as pH and iron with growth and blooms of these bacteria in the microcosms. New strain MTB-KTN90 was isolated in a modified isolation medium at microaerophilic zone from Anzali lagoon, Iran and cultured in a modified growth medium subsequently. The phylogenetic analysis showed that the strain belongs to Alphaproteobacteria. Growth and iron uptake studies indicated an important role by this bacterium in the iron biogeochemical cycle. For the first time, this paper introduced a cultured magnetotactic Alphaproteobacterium, able to synthesize magnetosomes in the temperatures above 30°C and reduce selenate oxyanion. CONCLUSIONS: This paper may serve as a guide to screening, isolation, and cultivation of more new MTB. The new isolated strain opens up good opportunities for biotechnological applications such as medicine to bioremediation processes due to its unique abilities.