Draft Genome Sequences of a Putative Prokaryotic Consortium (IPPAS B-1204) Consisting of a Cyanobacterium (Leptolyngbya sp.) and an Alphaproteobacterium (Porphyrobacter sp.)

A new presumably simple consortium of a Leptolyngbya sp. and a Porphyrobacter sp. was isolated from Tolbo Lake in Mongolia. The draft genome sequences of both species are reported.

A consortium consisting of two species, a Leptolyngbya sp. and a Porphyrobacter sp., was isolated from Tolbo Lake, an alpine lake of glacial origin (West Mongolia, 48°32=56ЉN 90°03=03ЉE, 2,079 meters above sea level). The consortium was deposited in the Collection of Microalgae and Cyanobacteria of the Institute of Plant Physiology of the Russian Academy of Sciences (IPPAS) under the accession number IPPAS B-1204 (http://www.cellreg.org/Catalog/Catalog%20NEW/IPPAS%20B-1204.html).
The consortium was grown photoautotrophically in BG-11 medium under 50 mol m Ϫ2 · s Ϫ1 photons of cool white light aerated by air enriched with 1.5% CO 2 (vol/vol). DNA was isolated as previously described (1)(2)(3). Sequencing was performed twice using the Ion PGM and Illumina MiSeq platforms. For the Ion PGM, 500-bp DNA fragments were prepared using the Ion PGM template IA 500 kit and sequenced using Hi-Q View chemistry on an Ion 316 Chip v2 (Thermo Fisher Scientific). For Illumina MiSeq 2 ϫ 300-bp paired-end reads, the library was prepared using the Nextera XT DNA library prep kit.
The draft genomic assembly of the Leptolyngbya sp. consisted of 187 scaffolds, an N 50 value of 1.5 ϫ 10 5 nucleotides (nt), and a total size of 8.2 Mbp with an average read coverage of 65ϫ. This genome contained 7,204 genes, with 6,725 coding DNA sequences (CDSs) and 81 RNAs. For the Porphyrobacter sp., the assembly consisted of 9 scaffolds, an N 50 value of 1.1 ϫ 10 6 nt, and a total size of 3.5 Mbp with an average read coverage of 50ϫ. The Porphyrobacter genome contained 3,327 genes, with 3,197 CDSs and 51 RNAs.
The genome of the Leptolyngbya sp. was analyzed with antiSMASH, which located gene clusters for biosynthesis of unusual carotenoids, alkaloids, antibiotics, the molluscicidal agent barbamide, nostopeptolide, nostophycin, yersiniabactin, lasso peptides, and nitrogen fixation.
The assumption that we were working with a consortium rather than two separate species in the same culture was supported by preliminary evidence similar to that described in reference 13. First, we were unable to isolate the axenic cyanobacterial component. Second, we found that the Leptolyngbya sp. negatively affected the growth of its partner, suggesting antibiosis. We also demonstrated a significant spatial proximity of the Leptolyngbya sp. and the Porphyrobacter sp. in IPPAS B-1204 ( Fig. 1C and  D), which implies putative trophic and biochemical interactions between the species. We are going to conduct a detailed polyphasic analysis (14) of these coexisting microorganisms in the future.  indicates trichomes visualized by blue and red) closely interacting with the Porphyrobacter sp. (asterisk indicates individual cells outlined by membranes stained green). Bar ϭ 5 m. Images were acquired using three channels of an Axio Imager Z2 epifluorescence microscope equipped with an AxioCam MRm high-resolution monochrome charge-coupled-device (CCD) camera and merged using AxioVision v4.8 software (Carl Zeiss, Göttingen, Germany). For the first channel, filter set 49 was used (excitation G 365, emission BP 445/50), and epifluorescence images of DAPI-DNA complexes were assigned a blue pseudocolor; for the second channel, filter set 44 was used (excitation BP 475/40, emission BP 530/50), and images of cell membranes stained with FM 1-43 were assigned a green pseudocolor; for the third channel, filter set 45 was used (excitation BP 560/40, emission BP 630/75), and cyanobacterial chlorophyll autofluorescence was assigned a red pseudocolor. Scale bar ϭ 5 m.