Characterization of a novel Idiomarina loihiensis strain isolated from the westernmost Mediterranean: heavy-metal resistance and biomineralization capability

This communication presents the identification of a bacterial strain, MAH1, isolated from a seawater sample collected from the westernmost Mediterranean surface waters. This strain was characterized using polyphasic taxonomy. It is Gram-negative, growing between 2--43 ºC (optimum 28-37 ºC), heterotrophic, aerobic and required NaCl for growth (0.7-20.0%, optimum being 2%). This strain is rod-shaped slightly curved with a single polar flagellum. Results of phylogenetic analyses evidenced that the strain belongs to Idiomarina loihiensis species (Donachie et al., 2003). The strain MAH1 displays a DNA base composition in G+C of the 48.2 mol%. The similarity of the 16S rDNA sequence and of the DNA-DNA hybridization to I. loihiensis (AF288370) is 100% and 96.1% respectively. Polar lipids were predominantly odd-numbered and iso-branched (15 and 17). According to these data we propose that the isolated MAH1 is a strain of the I. loihiensis species.
A preliminary study of the MAH1 strain mineralization capability and heavy metal resistance has also been performed. When the MAH1 strain is cultivated in a sea water solid medium (yeast extract 0.5%, triptone 1%, purified agar-agar 2% in seawater, pH 7.6) produces carbonates and phosphates. On the other hand, the minimal inhibitory concentrations of Ag, Cd, Pb, U, Ni, Cu, Cr, Mn and Zn for the growth of this bacterial strain are (concentration expressed as mM) 0.125, 0.125, 8.00, 8.00, 4.00, 4.00, 1.00, 8.00 and 2.00, respectively.
The obtained results are especially interesting in relation to the Idiomarina genus (Ivanova et al 2000), a member of the family Alteromonadaceae (Ivanova and Mikhailov, 2001) belonging to the subclases of the Proteobacteria.

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