Draft Genome Sequences of Facultative Methylotrophs, Gemmobacter sp. Strain LW1 and Mesorhizobium sp. Strain 1M-11, Isolated from Movile Cave, Romania.

Facultative methylotrophs belonging to the genera Gemmobacter and Mesorhizobium were isolated from microbial mat and cave water samples obtained from the Movile Cave ecosystem. Both bacteria can utilize methylated amines as their sole carbon and nitrogen source. Here, we report the draft genome sequences of Gemmobacter sp. strain LW1 and Mesorhizobium sp. strain IM1.

GENOME ANNOUNCEMENT

Movile Cave (Mangalia, Romania) is a hypogenic cave ecosystem that has been isolated from the surface for 5.5 million years and is devoid of any input of organic carbon from above (1). Invertebrates present in the cave are adapted to life in the dark and are supported by chemolithoautotrophic primary producers that derive energy from the oxidation of inorganic compounds (hydrogen sulfide, hydrogen, and methane) (2, 3). Degradation of the microbial mats floating on the surface of the cave water probably produces large amounts of methylated amines (MA), as indicated by the apparent abundance and activity of MA degraders (4, 5). Here, we report the draft genome sequences of two facultative methylotrophs, Gemmobacter sp. strain LW1 and Mesorhizobium sp. strain 1M-11, isolated from cave water and a microbial mat, respectively (5). DNA from the isolates was obtained using the phenol-chloroform method (6). The draft genome sequences were generated at The Genome Analysis Centre (TGAC), Norwich, United Kingdom, using the Illumina platform. The raw sequences were assembled using ABySS version 1.3.4 (7) using a range of k-mer sizes. The best-performing assembly (k-mer-wise and filtered versus unfiltered) was selected based on the assembly metrics and was subsequently scaffolded further using SSPACE version 2.0 (8). GapCloser-1.12 was then used to close any gaps in the scaffolded assembly. All reads were quality trimmed using Sickle version 1.1 (GitHub) based on a Q30 quality score. Genome annotation was performed using the RAST annotation server (9).

Gemmobacter sp. LW1 belongs to the family Rhodobacteraceae, and the genus Gemmobacter includes only five validated species, which were recently reassigned from the genus Catellibacterium (10). The genome includes 4,256 coding sequences (CDSs) and 79 tRNAs, and it is 4.35 Mb in size. Mesorhizobium sp. 1M-11 (family Phyllobacteriaceae; 6,592 CDSs, 79 tRNAs, and 6.69 Mb in size), closely related to Mesorhizobium loti, based on 16S rRNA gene sequence identity (11), is the only known member of the genus Mesorhizobium to grow methylotrophically. Even though M. loti possesses genes (i.e., gmaS) involved in the N-methylglutamate pathway, this organism cannot grow methylotrophically on methylated amines (12). The gene clusters responsible for methylamine utilization, through both methylamine dehydrogenase (13) and N-methylglutamate pathways (14, 15), were identified in the genomes of both isolates. Also, genes encoding the enzyme trimethylamine monooxygenase (Tmm) (16) are present in both the genomes, with the metabolic potential confirmed by growth on trimethylamine as the sole carbon and nitrogen source (5). Genes encoding enzymes of the pentose phosphate pathway, Entner-Doudoroff (a variant of the ribulose monophosphate [RuMP] pathway) pathway, the tricarboxylic acid (TCA), and serine cycles were also predicted. The gene folD, encoding the enzyme 5,10 methylene-tetrahydrofolate dehydrogenase/cyclohydrolase, is present in these genomes, suggesting that formaldehyde is utilized through tetrahydrofolate (H4F) (genes encoding key enzymes in the tetrahydromethanopterin [H4MPT]-mediated C1 oxidation pathway are absent) (17). While genes coding for sulfur oxidation pathways are present in both isolate genomes, genes involved in denitrification (nirS-type), propane (prmA), and carbon monoxide (coxL) oxidation were predicted only in the genome of Gemmobacter sp. LW1. In summary, these genome sequences present a metabolic blueprint for these two methylotrophic isolates from Movile Cave, and they provide excellent model organisms for understanding methylotrophy in this unusual ecosystem.

Nucleotide sequences accession numbers.

This whole-genome shotgun project has been deposited at GenBank under the accession numbers LJSC00000000 and LJSD00000000. The versions described in this paper are versions LJSC01000000 and LJSD01000000.