New insights in bacterial and eukaryotic diversity of microbial mats inhabiting exploited and abandoned salterns at the Ré Island (France).

In order to understand the effect of human practices on microbial mats organisation, the study aimed to investigate the biodiversity within microbial mats from exploited and abandoned salterns. Despite several attempts, archaeal 16S rRNA gene fragment sequences were not obtained, indicating that microbial mats were probably dominated by Bacteria with very low abundance of Archaea (< 1%). Thus, the study compared the bacterial and meiofaunal diversity of microbial mats from abandoned and exploited salterns. The higher salinity (101 ± 3.7 psu vs. 51.1 ± 0.7 psu; Welch t-test p < 0.05) of the exploited site maintained lower bacterial diversity in comparison to the abandoned site where the salinity gradient was no longer maintained. However, the microbial mats exhibited similar bacterial class composition while the eukaryotic diversity was significantly higher in the exploited saltern. The abandoned saltern was dominated by sulfate-reducing bacteria and Nematoda, while the exploited saltern was characterized by the presence of halophilic bacteria belonging to Marinobacter, Salinivibrio and Rhodohalobacter genera, and the larger abundance of Hypotrichia (ciliates). Such bacterial and eukaryotic diversity difference might be explained by human actions for salt recovery in exploited salterns such as scraping the surface of microbial mat and increasing salinity renewing the microbial mat each year. Such action decreases the bacterial diversity changing the food web structure that favour the presence of a larger diversity of eukaryotic organisms. Our study provides new insights on microbial mat communities inhabiting salterns, especially the consequences of abandoning saltern exploitation.

Geological gas-storage shapes deep life.

Around the world, several dozen deep sedimentary aquifers are being used for storage of natural gas. Ad hoc studies of the microbial ecology of some of them have suggested that sulfate reducing and methanogenic microorganisms play a key role in how these aquifers' communities function. Here, we investigate the influence of gas storage on these two metabolic groups by using high-throughput sequencing and show the importance of sulfate-reducing Desulfotomaculum and a new monophyletic methanogenic group. Aquifer microbial diversity was significantly related to the geological level. The distance to the stored natural gas affects the ratio of sulfate-reducing Firmicutes to deltaproteobacteria. In only one aquifer, the methanogenic archaea dominate the sulfate-reducers. This aquifer was used to store town gas (containing at least 50% H2 ) around 50 years ago. The observed decrease of sulfates in this aquifer could be related to stimulation of subsurface sulfate-reducers. These results suggest that the composition of the microbial communities is impacted by decades old transient gas storage activity. The tremendous stability of these gas-impacted deep subsurface microbial ecosystems suggests that in situ biotic methanation projects in geological reservoirs may be sustainable over time.

Cytoreductive surgery of colorectal peritoneal metastases: outcomes after complete cytoreductive surgery and systemic chemotherapy only.

BACKGROUND: Cytoreductive peritoneal surgery (CRS) associated with hyperthermic peritoneal chemotherapy (HIPEC) has long been considered the standard treatment for colorectal peritoneal metastases (CPM). However, although efficacy of surgery has been demonstrated, evidence supporting HIPEC's role is less certain. METHOD: Overall survival (OS), progression-free survival (PFS) and morbidity were analysed retrospectively for fifty consecutively included patients treated for colorectal CPM with complete CRS and systemic chemotherapy only. RESULTS: Median peritoneal cancer index (PCI) was 8 (range 1-24). 23 patients had liver or lung metastases (LLM). 22 patients had synchronous CPM. 27 complications occurred (12 Grade 1/2, 14 Grade 3, 1 Grade 4a, 0 Grade 5). Median follow-up was 62.5 months (95 %CI 45.4-81.3), median survival 32.4 months (21.5-41.7). Three- and 5-year OS were 45.5% (0.31-0.59) and 29.64% (0.17-0.44) respectively. Presence of LLMs associated with peritoneal carcinomatosis was significantly associated with poorer prognosis, with survival at 5 years of 13.95% (95 %CI 2.9-33.6) vs. 43.87% (22.2-63.7) when no metastases were present (P= 0.018). Median PFS was 9.5 months (95 %CI 6.2-11.1). CONCLUSION: With an equivalent PCI range and despite one of the highest rates of LLM in the literature, our survival data of CRS + systemic chemotherapy only compare well with results reported after additional HIPEC. Tolerance was better with acceptable morbidity without any mortality. Extra-hepatic metastasis (LLM) is a strong factor of poor prognosis. Awaiting the results of the randomized PRODIGE trial, these results indicate that CRS + systemic chemotherapy only is a robust hypothesis to treat colorectal CPM.