CaveThiovulaceaediffer metabolically and genomically from marine species

Abstract

Life in Movile Cave (Romania) relies entirely on primary carbon fixation by bacteria oxidizing sulfide, methane and ammonia with oxygen, nitrate, sulfate, and ferric iron. There, large spherical-ovoid bacteria (12-16 µm diameter), rich in intracellular sulfur globules, dominate the stable microbial community in the surface water of a hypoxic Air Bell. These were identified as Thiovulum sp. (Campylobacterota). We obtained a closed genome of this Thiovulum and compared it to that of Thiovulum ES. The genes for oxidizing sulfide to sulfate are absent, therefore, Thiovulum likely avoids constant accumulation of elemental sulfur either by oxidizing sulfide to sulfite which is then excreted, or via dissimilatory nitrate reduction to ammonia using the formate-dependent nitrite reductase or hydroxylamine oxidoreductase. Thus, Thiovulum, found also in other caves, is likely important to both S and N cycles in subterranean aquatic ecosystems. Additionally, using electron microscopy, we suggest that in absence of motor-like structures along the membrane, the peritrichous flagella-like structures are type IV pili, for which genes were found in both Thiovulum genomes. These pili may play a role in veil formation, connecting adjacent cells. The force exerted by coordinated movement of such pili may partly explain the exceptionally fast swimming of these bacteria.

Competition-cooperation in the chemoautotrophic ecosystem of Movile Cave: first metagenomic approach on sediments

“…Similar metabolic traits were found for the recently characterized Thiovulum sp. that dominates Movile Cave's hypoxic Air Bells microbial mat [22]. Moreover, Arcobacteraceae family was found dominant in the white filaments from the thermal sulfidic spring of Fetida Cave, Italy [56].…”

“…Here, an active redox interface is created on both the water's surface and cave walls, colonized by floating microbial mats and biofilms. Most of our knowledge of this ecosystem comes from studies of trophic chain components such as microbial mats associated with the surface of the hydrothermal water and its close proximity [19][20][21][22]. In addition, the rich endemic invertebrates of Movile Cave live in the proximity of the sulfidic water.…”

Competition-cooperation in the chemoautotrophic ecosystem of Movile Cave – first metagenomic approach on sediments

“…Similar metabolic traits were found for the recently characterized Thiovulum sp. isolated from Movile Cave’s hypoxic Air Bells microbial mat [22]. Moreover, Arcobacteraceae family was found dominant in the white filaments from the thermal sulfidic spring of Fetida Cave, Italy [56].…”

“…Here, an active redox interface is created on both the water's surface and the walls of the cave, which are colonized by floating microbial mats and biofilms. Most of our understanding of this ecosystem comes from studies on trophic chain components such as microbial mats associated with the hydrothermal water surface and its close proximity [19][20][21][22]. In addition, the rich endemic invertebrate fauna of Movile Cave gravitates in the proximity of the sulfidic water, being most abundant in the Air-Bells and Lake Room [15,19] where the redox potential is higher, particularly in the Air-Bells water surface [23].…”

Development of chemosynthetic microbial communities in organic falls deployed in the deep Southwest Atlantic Ocean

“…Campylobacterota was also found to be a dominant group in the only microbiological survey on whale fall performed in the south Atlantic Ocean to date (Cavalett et al 2017). The authors reported that sediment samples collected underneath a whale carcass found at 4200 m contained high proportions of Epsilonproteobacteria - the taxa previously assigned to this class are now included in the phylum Campylobacterota, according Silva v. 138 (Bizic et al 2020). We also detected Gammaproteobacteria S-oxidisers, mainly from the family Thiomicrospiraceae.…”