The temperature ranged from 15 to 17 °C. The concentrations of oxygen in surface sediments in which MTB were enriched were 0.29 and 0.10 mg L−1, respectively, for microcosms MY8 and MY11 in April, indicating

microaerobic conditions. Overall, the concentrations of most anions and cations of MY8 decreased over time, and yet the corresponding changes of MY11 were rather irregular. MY8a had higher concentrations of Cl− (18.8 μg mL−1), Na+ (24.5 μg mL−1), K+ (4.25 μg mL−1), Mg2+ (20.5 μg mL−1) and iron (626 μg L−1) than the other samples, whereas MY11c was highly enriched in SO42− (128 μg mL−1) and Ca2+ (42.4 μg mL−1). The concentrations of NO3− of MY8 (0.39–0.74 μg mL−1) were higher than that Selleck CP-868596 of MY11 (≤0.24 μg mL−1). The concentrations of F− were relatively constant for all samples. Thirteen OTUs were identified from a total of 132 clones after eliminating the putative learn more non-MTB contaminations (23 clones) and putative chimeras (five clones). 16S rRNA genes from microcosm MY8 (libraries MY8a, MY8b and MY8c) could be divided into five OTUs, as follows: OTU 8 (58.57% of the total

clones), OTU 1 (35.71%), OTU 2 (2.86%), OTU 29 (1.43%) and OTU 50 (1.43%) (Fig. 2a). The average distance between these OTUs was 15%, and all sequences were ≤94% identical. All OTUs except OTU 1 were within the Alphaproteobacteria and most related to magnetotactic coccus strains (Fig. 3). OTU 2 was the closest relative to Magnetococcus clone CF22 recovered from a freshwater habitat in Northern Germany (Flies et al., 2005b) with 97.25% similarity. OTU 8 and 50 were 96.64% and 97.38%, respectively,

similar to Magnetococcus clone CF2, which was detected in lake ‘Waller See’ in Bremen (Flies et al., 2005a). OTU 29 was found to share high similarity (98.36%) Thymidylate synthase to Magnetococcus clone MYG-22, which was previously recovered from the same place (Lin et al., 2008). Phylogenetic analysis of OTU 1 had shown that it clustered within the Nitrospira phylum and was 99.53% similar to the ‘Magnetobacterium bavaricum’-like clone OTU C (Lin et al., 2009). Eight OTUs were identified from microcosm MY11 (libraries MY11a, MY11b and MY11c). OTU 51 was encountered most frequently and represented 59.02% of the total clones (Fig. 2a). The other OTUs included OTU 13 (3.28%), OTU 14 (14.75%), OTU 15 (3.28%), OTU 17 (8.20%), OTU 21 (6.55%), OTU 52 (1.64%) and OTU 53 (3.28%, Fig. 2a). All OTUs from microcosm MY11 were affiliated with Alphaproteobacteria and showed ≤98% similar (Fig. 3). OTUs 13 and 14 had 97.47% and 96.92% sequence identities, respectively, with magnetotactic coccus CS308 (Spring et al., 1992). OTUs 52 and 53 were closely related to Magnetococcus clone CF23 (98.76% and 97.74%, respectively) (Flies et al., 2005b). OTUs 15, 17 and 21 were 96.85%, 89.04% and 97.06% identical to Magnetococcus clones MYG-22, XSE-42 and CF2, respectively. Furthermore, OTU 51 was found to share high identity (99.66%) to Magnetococcus clone OTU A, which was recovered from the same site previously (Lin et al., 2009).