A Novel Highly Efficient Device for Growing Micro-Aerophilic Microorganisms.

This work describes a novel, simple and cost-effective culture system, named the Micro-Oxygenated Culture Device (MOCD), designed to grow microorganisms under particularly challenging oxygenation conditions. Two microaerophilic magnetotactic bacteria, a freshwater Magnetospirillum gryphiswaldense strain MSR-1 and a marine Magnetospira sp. strain QH-2, were used as biological models to prove the efficiency of the MOCD and to evaluate its specifications. Using the MOCD, growth rates of MSR-1 and QH-2 increased by four and twofold, respectively, when compared to traditional growing techniques using simple bottles. Oxystat-bioreactors have been typically used and specifically designed to control low dissolved oxygen concentrations, however, the MOCD, which is far less sophisticated was proven to be as efficient for both MSR-1 and QH-2 cultures with regard to growth rate, and even better for MSR-1 when looking at cell yield (70% increase). The MOCD enables a wide range of oxygenation conditions to be studied, including different O2-gradients. This makes it an innovative and ingenious culture device that opens up new parameters for growing microaerobic microorganisms.

Magnetotactic bacteria population in a pristine French Atlantic lagoon.

In this study, we report for the first time the presence of magnetotactic bacteria (MTB) on the Northeastern Atlantic coast. Microscopy observations indicated a heterogeneous population of MTB morphotypes. The analysis of the 16S rDNA by pyrosequencing technology revealed four operational taxonomic sequence units affiliated within the Magnetococcales order, class Alphaproteobacteria. One of them was closely related to sequences of MTB from the Tunisian coast, central Mediterranean Sea. This work offers information on anew environmental context and on biogeography of MTB, highlights the putative impact that marine currents may have on MTB distribution on Earth, and underlines the role that pristine or polluted areas may play on the structure of the MTB communites.

Diversity of magnetotactic bacteria from a French pristine Mediterranean area.

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.