| Magnetotactic bacteria were collected from the sediment of Yellow Sea, East-China Sea and Huiquan Bay (Qingdao, China). Maximum abundance of magnetotactic bacteria was up to 105 cells/cm3.The results obtained with the magnetotactic bacteria from the intertial zone are intriguing. Virtually only magnetotactic ovoidal-cocci were observed. Magnetotactic bacteria collected from the subtidal zone displayed various cell shapes. Although morphotypes, including cocci, oviform, rods, vibrios and spirilla were observed under the transmission electron microscope, the coccoid shape was most abundant. The magnetosomes were arranged in one, two or multiple chains. Irregular arrangement of magnetosomes was also evident. Morphology of magnetosome crystals was homogenous in a given cell, but displayed various shapes, including square, cubo-octahedron, parallelepiped, elongated hexagonal prismatic, bullet-shaped and tooth-shaped in different cells. Coccoid morphotype was the dominant cell-shape.The morphological diversity of marine magnetotactic bacteria was confirmed by RFLP and sequence analysis of 16S rDNA. Phylogenetic analysis showed that three of the subgroups from the intertial zone were probably affiliated with Alpha-proteobacteria. Pair-wise comparison revealed that 16S rDNA sequence identity showed >98% sequence identity. Phylogenetic analysis showed that nine of the subgroups from the subtidal zone were probably affiliated with Alpha-proteobacteria, whereas one with Gamma-proteobacteria. The physical and chemical environment factors are the dominant cause. At present, cultivation of these cells was unsuccessful as most magnetotactic bacteria reported in literature.A widely accepted concept in microbial taxonomy is that 16S rDNA sequences belong to the same species with similarity values >97%, and to the same genus with similarity values >93-95%. Therefore, these data strongly suggest that strains of the magnetotactic bacteria from Huiquan Bay affiliate with a new genus.
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