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Most members of the family Treponemataceae (Spirochaetales) are associated with vertebrate hosts. However, a diverse clade of uncultured, putatively free-living treponemes comprising several genus-level lineages is present in other anoxic environments. The only cultivated representative to date is Treponema zuelzerae, isolated from freshwater mud. Here, we describe the isolation of strain RmG11 from the intestinal tract of cockroaches. The strain represents a novel genus-level lineage of Treponemataceae and is metabolically distinct from T. zuelzerae. While T. zuelzerae grows well on various sugars, forming acetate and H(2) as major fermentation products, strain RmG11 grew poorly on glucose, maltose, and starch, forming mainly ethanol and only small amounts of acetate and H(2). In contrast to the growth of T. zuelzerae, that of strain RmG11 was strongly inhibited at high H(2) partial pressures but improved considerably when H(2) was removed from the headspace. Cocultures of strain RmG11 with the H(2)-consuming Methanospirillum hungatei produced acetate and methane but no ethanol. Comparative genomic analysis revealed that strain RmG11 possesses only a single, electron-confurcating hydrogenase that forms H(2) from NADH and reduced ferredoxin, whereas T. zuelzerae also possesses a second, ferredoxin-dependent hydrogenase that allows the thermodynamically more favorable formation of H(2) from ferredoxin via the Rnf complex. In addition, we found that T. zuelzerae utilizes xylan and possesses the genomic potential to degrade other plant polysaccharides. Based on phenotypic and phylogenomic evidence, we describe strain RmG11 as Brucepastera parasyntrophica gen. nov., sp. nov. and Treponema zuelzerae as Teretinema zuelzerae gen. nov., comb. nov. IMPORTANCE Spirochetes are widely distributed in various anoxic environments and commonly form molecular hydrogen as a major fermentation product. Here, we show that two closely related members of the family Treponemataceae differ strongly in their sensitivity to high hydrogen partial pressure, and we explain the metabolic mechanisms that cause these differences by comparative genome analysis. We demonstrate a strong boost in the growth of the hydrogen-sensitive strain and a shift in its fermentation products to acetate during cocultivation with a H(2)-utilizing methanogen. Our results add a hitherto unrecognized facet to the fermentative metabolism of spirochetes and also underscore the importance of interspecies hydrogen transfer in not-obligately-syntrophic interactions among fermentative and hydrogenotrophic guilds in anoxic environments.

Additional file 2: Figure S1. Time-calibrated phylogenetic tree of termites inferred from mitochondrial genome sequences. Figure S2. Relative abundance of archaeal and bacterial phyla inferred from the termite gut metagenomes and the 16S rRNA amplicon data of 74 termite samples. Figure S3. Maximum likelihood phylogenetic tree inferred from 43 single-copy marker genes of 654 metagenome-assembled genomes (MAGs). The completeness and contamination of MAGs was inferred with CheckM [103]. Detailed information about each MAG is available in Table S9. Figure S4. Protein sequence alignment of predicted uricases from 53 termite transcriptomes previously published in Bucek et al. [27].

A first study by Pierre Sabatier and colleagues (co-funded by the OHM Littoral Caraïbe, APR 2018 and 2019) analyzed core sediments from both Guadeloupe and Martinique (French West Indies), and showed that the widespread use of a non-specific systemic herbicide (glyphosate) at the end of the years 1990 has induced an unprecedented rise in soil erosion and a major release of persistent chlordecone pesticides that were trapped in banana field soils. We have now studied the implications of these agricultural usages and environmental consequences on the dynamics of the eukaryotic biodiversity using a metabarcoding approach. We show that both the OTU richness and the diversity were significantly higher in samples corresponding to the period 2001-2017 which is characterized by a fast sedimentation rate (FSR), compared to the period 1950-2000 which is characterized by a slow sedimentation rate (SSR). Temporal analyses demonstrated that during the FSR period the relative read abundances of several classes were significant increasing over time while over were decreasing. On the contrary the same classes demonstrated a relative stability over the second half of the 20th century. Combined to temporal analyses of the alpha and beta diversity we could capture the ongoing temporal changes in eukaryotic community composition in a way that probably reflects the ecological processes and the ecosystem functions that are involved. Overall, our results show a correlation between concentration of pollutants from agricultural usages, modifications of the land erosion processes and compositional reorganizations over the two last decades in a critical transition zone located close to the most anthropized area of Guadeloupe, Des premières études de Pierre Sabatier et ses collègues (cofinancées par l'OHM Littoral Caraïbe, APR 2018 et 2019) qui ont analysé des carottes de sédiments à la fois en Guadeloupe et en Martinique (Antilles Françaises), ont montré que l'utilisation généralisée d'un herbicide systémique non spécifique (le glyphosate) à la fin des années 1990 a induit une augmentation sans précédent de l'érosion des sols et une libération importante de pesticides persistants de type chlordécone qui étaient piégés dans les sols des champs de bananes. Nous avons maintenant étudié les implications de ces usages agricoles et des conséquences environnementales sur la dynamique de la biodiversité eucaryote en utilisant une approche de métabarcodage. Nous montrons que la richesse en OTU et la diversité sont significativement plus élevées dans les échantillons correspondant à la période 2001-2017 qui est caractérisée par un taux de sédimentation rapide (FSR), par rapport à la période 1950-2000 qui est caractérisée par un taux de sédimentation lent (SSR). Des analyses temporelles ont démontré que durant la période FSR, les abondances relatives en lecture de plusieurs classes augmentaient significativement dans le temps alors que pour d’autres classes nous observions une diminution. A l’inverse, ces mêmes classes présentent une stabilité relative au cours de la seconde moitié du 20ème siècle. En combinant des analyses temporelles de la diversité alpha et bêta, nous avons pu capturer des changements temporels dans la composition des assemblages eucaryotes d'une manière qui reflète probablement les processus écologiques et les fonctions de l'écosystème qui sont impliqués. Globalement, nos résultats montrent une corrélation entre la concentration de polluants issus des usages agricoles, les modifications des processus d'érosion des sols et les réorganisations de la composition au cours des deux dernières décennies dans une zone de transition critique située à proximité de la zone la plus anthropisée de la Guadeloupe.