Diversity Of Magnetotactic Bacteria In Sediments Of Different Marine Habitats

Magnetotactic bacteria(MTB) are Gram-negative, producing magnetosomes, motile prokaryotes that can orient and migrate along the geomagnetic lines of force. They are ubiquitous in sediments and stratified water column, distributing predominantly in the oxic-anoxic transition zone(OATZ). MTB have a lot of morphological types, including cocci, rods, vibrios, spirilla and multicellular magnetotactic prokaryotes. Usually, cocci are the dominant magnetotactic morphology. Variable phylogenetic relatedness of MTB has been confirmed on the basis of 16 S r RNA genes. All MTB discovered are affiliated to Alphaproteobacteria Class, Gammaproteobacteria Class, Deltaproteobacteria Class, Nitrosoira Phylum and Candidate division OP3. MTB can biomineralize iron oxide and/or iron sulfide magnetosomes, which cause MTB to align and swim along the magnetic field lines. In most MTB, magnetosomes are organized in chain(s).In this study, a combination of ecological investigation and experimental technique, such as light microscopic observation, transmission electron microscopic observation, and molecular biological techniques, were utilized to study the distribution and diversity of marine MTB inhabiting in sediments of three China Seas. The sampling sites in Taiping bay in Qingdao was an intertidal zone of the Yellow Sea. The sampling sites in Tanyahaijiao in Sanya was an intertidal zone of the South China Sea. East China Sea sediments were in seafoor. This study revealed the diversity of MTB in these three areas.A certain amount of magnetotactic bacteria were in the intertidal zone of Taiping Bay both in spring and autumn and Tianyahaijiao in Hainan Island. The dominant morphology of MTB in intertidal zone was cocci. Other morphology can hardly be observed. The magnetosomes of these MTB were mainly organized in chain(s), including one chain, two chains, and multiple chains. The chemical composition of crystals of magnetosomes of these MTB was magnetite. In addition, the MTB in these three area contained phosphorus granules in different sizes. 16 S rRNA gene analysis revealed that the MTB discovered in Taiping Bay in spring belonged to thirteen OTUs, nine of which represented potential new species and five represented potential new genus, and were affiliated to Alphaproteobacteria Class. The MTB discovered in Taiping Bay in autumn belonged to eleven OTUs, six of which represented potential new species and two represented potential new genus, and were also affiliated to Alphaproteobacteria Class. The MTB discovered in Tianyahaijiao in Hainan Island belonged to nine OTUs, eight of which represented potential new species and five represented potential new genus, and eight OTUs were affiliated to Alphaproteobacteria Class while one was affiliated to Gammaproteobacteria Class.MTB were found in the sediments of nineteen sampling sites in the East China Sea. The MTB in most sampling sites were cocci and one large rod-shaped magnetotactic bacterium was observed in the sediments of sampling site 8-5. The length of this MTB was about 5 μm,average width was 0.8 μm. There were two vesicle with the diameter of about 0.75 μm in the thick end of its cell. It had one magnetosome chain(containing forty-nine magnetosomes) parallel to its long axis.This report discovered new area where MTB distributed and potential novel MTB species, and enriched the diversity of MTB. It can enhance the understanding of the spatial and temporal differences of MTB communities.