Diversity of Magnetotactic Bacteria from a French Pristine Mediterranean Area

Abstract

Magnetotactic bacteria synthesize intracellular magnetite and/or greigite magnetosome crystals. They play a significant role in both iron and sulfur cycles in sedimentary aquatic environments. To get insight into the bio-geochemical contribution of MTB, more studies concerning their ecology and their distribution in diverse habitats are necessary. The MTB community of an oil-industry polluted area of the French Mediterranean coast has been previously investigated. Here, we investigate the MTB community from coastal sediments of a Mediterranean pristine area using optical and transmission electron microscopy and phylogenetic analysis based on 16S rRNA gene sequences. A particularly high diversity of MTB was observed, with cocci phylogenetically distributed across the order Magnetococcales, including a novel cluster with sequences from the Mediterranean Sea designated as "Med group", and novel morphotypes.

Analysis of a population of magnetotactic bacteria of the Gulf of Gabès, Tunisia

“…At 10-cm-depth sediments, dissolved oxygen concentration was at 10 % atm, redox potential was at 350 mV, and no H 2 S was detected. Iron was detected only under the Fe(III) form, at 0.3 (±0.1) mM, which correspond to a low concentration by comparison to 40 mM detected on the Northern Mediterranean areas (Fuduche et al 2015;Postec et al 2012). Nitrate concentration was 2.0 (±0.1) mM and sulfate was 30 (±2.0) mM, which is consistent with concentrations frequently found in marine environments.…”

“…1b), as previously observed and suggested (Jögler et al 2010;Keim et al 2005). The MTB community of this Tunisian Southern Mediterranean area was morphologically less diversified than the MTB communities previously investigated on the French Northern Mediterranean coast (Fuduche et al 2015;Postec et al 2012). …”

“…It has been the case for samples from the Northern Mediterranean coast, either in polluted or nonpolluted areas (Fuduche et al 2015;Postec et al 2012). Based on their sequence identities, the 33 OTUs may represent 9 different families (less than 95 % identity) and 10 different genera (less than 97 % identity).…”

“…MMPs density was estimated to 10 2 -10 3 per mL. Their morphology was similar to that of the mulberry-like MMPs from the Yellow Sea in China, from Salt Pond in USA, and from the Northern Mediterranean coast (Fuduche et al 2015;Lefèvre et al 2007;Simmons et al 2004;Zhou et al 2013). Fig.…”

“…Previous studies have investigated the MTB community of the North Mediterranean coast in polluted and non-polluted areas (Fuduche et al 2015;Postec et al 2012). The Gulf of Gabès locates in the south-eastern coast of Tunisia.…”