Architecture of flagellar apparatus of marine magnetotactic cocci from Qingdao
青岛海洋趋磁球菌QH-3 的鞭毛特征

Magnetotactic bacteria can align and swim along the geomagnetic field lines. The motility is propelled by the rotation of semi-rigid flagellar filaments. In this study, we reported the motility and ultrastructure of marine magnetotactic cocci isolated from intertidal zone in Qingdao city. Results obtained by optical microscopy and transmission electron microscopy showed that these ovoid-shaped bacteria, QH-3, possessed two bundles of flagella. Each bundle with a diameter of about 62 nm ±9 nm consists of seven flagellar filaments enveloped in a sheath. The architecture of flagellar apparatus was similar to that of Mediterranean magneto-ovoid bacteria MO-1. However, QH-3 synthesized two chains of rectangular magnetosomes instead of one chain found in MO-1 cells. Such flagellar architecture has been reported only for some magnetotactic cocci. This observation suggests that the typical structure of the flagellar apparatus may be required for the magnetotactic motility of this group of microbes.