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Serpentinizing hydrothermal systems result from water circulating into the subsurface and interacting with mantle-derived rocks notably near mid-ocean ridges or continental ophiolites. Serpentinization and associated reactions produce alkaline fluids enriched in molecular hydrogen, methane, and small organic molecules that are assumed to feed microbial inhabitants. In this study, we explored the relationships linking serpentinization to associated microbial communities by comparative metagenomics of serpentinite-hosted systems, basalt-hosted vents, and hot springs. The shallow Prony bay hydrothermal field (PBHF) microbiome appeared to be more related to those of ophiolitic sites than to the Lost City hydrothermal field (LCHF) microbiome, probably because of the meteoric origin of its fluid, like terrestrial alkaline springs. This study emphasized the ubiquitous importance of a set of genes involved in the catabolism of phosphonates and highly enriched in all serpentinizing sites compared to other ecosystems. Because most of the serpentinizing systems are depleted in inorganic phosphate, the abundance of genes involved in the carbon-phosphorus lyase pathway suggests that the phosphonates constitute a source of phosphorus in these ecosystems. Additionally, hydrocarbons such as methane, released upon phosphonate catabolism, may contribute to the overall budget of organic molecules in serpentinizing systems. IMPORTANCE This first comparative metagenomic study of serpentinite-hosted environments provides an objective framework to understand the functioning of these peculiar ecosystems. We showed a taxonomic similarity between the PBHF and other terrestrial serpentinite-hosted ecosystems. At the same time, the LCHF microbial community was closer to deep basalt-hosted hydrothermal fields than continental ophiolites, despite the influence of serpentinization. This study revealed shared functional capabilities among serpentinite-hosted ecosystems in response to environmental stress, the metabolism of abundant dihydrogen, and the metabolism of phosphorus. Our results are consistent with the generalized view of serpentinite environments but provide deeper insight into the array of factors that may control microbial activities in these ecosystems. Moreover, we show that metabolism of phosphonate is widespread among alkaline serpentinizing systems and could play a crucial role in phosphorus and methane biogeochemical cycles. This study opens a new line of investigation of the metabolism of reduced phosphorus compounds in serpentinizing environments.

Doxycycline has been proposed for the treatment of malnourished children in developing countries, and its use has been associated with weight gain in healthy volunteers. No previous studies have assessed abnormal weight gain as a putative side effect of long-term doxycycline treatment; thus, the objective of the present study was to characterize this phenomenon. We also analyzed the role of the gut microbiota in this effect. We assessed changes in the body mass index in Q fever endocarditis patients treated with doxycycline and hydroxychloroquine and healthy individuals with no antibiotic treatment. Abnormal weight gain was defined as a gain in weight above that of the controls. The fecal samples were examined using molecular assays for Methanobrevibacter smithii, Bacteroidetes, Firmicutes, Escherichia coli, Lactobacillus, Lactobacillus reuteri, and total bacterial concentrations. We examined 82 patients, including 48 patients with Q fever endocarditis and 34 controls. Approximately 23% of the treated patients showed abnormal weight gain (P = 0.001). Patients treated with doxycycline and hydroxychloroquine presented significantly lower concentrations of Bacteroidetes (P = 0.002), Firmicutes (P = 0.01), and Lactobacillus (P = 0.02). The linear regression analysis revealed that the duration of treatment was significantly associated with a decrease in Bacteroidetes (P = 0.0001), Firmicutes (P = 0.002), and total bacteria (P < 0.00001). Abnormal weight gain is a side effect of long-term doxycycline and hydroxychloroquine treatment. Gut microbiota modifications at the phylum level could play an instrumental role in this effect. We highlight the need for specific nutritional care in patients undergoing long-term antibiotic treatment, particularly treatment involving the use of doxycycline., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

We report the draft genome sequence of Lactobacillus ingluviei strain Autruche 4 (CSURP209) isolated from an ostrich. L. ingluviei is associated with weight gain in mice. This genome sequence may help us understand the obesity-induced mechanisms of intestinal bacteria.