Candidatus Nitrosocaldus cavascurensis, an Ammonia Oxidizing, Extremely Thermophilic Archaeon with a Highly Mobile Genome

Sophie S. Abby, Michael Melcher, Melina Kerou, Mart Krupovic, Michaela Stieglmeier, Claudia Rossel, Kevin Pfeifer, Christa Schleper
2018 Frontiers in Microbiology  
24 Ammonia oxidizing archaea (AOA) of the phylum Thaumarchaeota are widespread in 25 moderate environments but their occurrence and activity has also been demonstrated in 26 hot springs. Here we present the first cultivated thermophilic representative with a 27 sequenced genome, which allows to search for adaptive strategies and for traits that 28 shape the evolution of Thaumarchaeota. Candidatus Nitrosocaldus cavascurensis has 29 been cultivated from a hot spring in Ischia, Italy. It grows
more » ... mally at 68°C under 30 chemolithoautotrophic conditions on ammonia or urea converting ammonia 31 stoichiometrically into nitrite with a generation time of approximately 25h. Phylogenetic 32 analyses based on ribosomal proteins place the organism as a sister group to all known 33 mesophilic AOA. The 1.58 Mb genome of Ca. N. cavascurensis harbors an amoAXCB 34 gene cluster encoding ammonia monooxygenase, genes for a 3-hydroxypropionate/4-35 hydroxybutyrate pathway for autotrophic carbon fixation, but also genes that indicate 36 potential alternative energy metabolisms. Although a bona fide gene for nitrite 37 reductase is missing, the organism is sensitive to NO-scavenging, underlining the 38 importance of this compound for AOA metabolism. Ca. N. cavascurensis is distinct 39 from all other AOA in its gene repertoire for replication, cell division and repair. Its 40 genome has an impressive array of mobile genetic elements and other recently acquired 41 gene sets, including conjugative systems, a provirus, transposons and cell appendages. 42 Some of these elements indicate recent exchange with the environment, whereas others 43 seem to have been domesticated and might convey crucial metabolic traits. 44 45 not peer-reviewed)
doi:10.3389/fmicb.2018.00028 pmid:29434576 pmcid:PMC5797428 fatcat:frbtb3wpufbq3h7oaytbaya4yq