- Short genome report
- Open Access
Complete genome sequence of Salinicoccus halodurans H3B36, isolated from the Qaidam Basin in China
Standards in Genomic Sciences volume 10, Article number: 116 (2015)
Salinicoccus halodurans H3B36 is a moderately halophilic bacterium isolated from a sediment sample of Qaidam Basin at 3.2 m vertical depth. Strain H3B36 accumulate N α-acetyl-α-lysine as compatible solute against salinity and heat stresses and may have potential applications in industrial biotechnology. In this study, we sequenced the genome of strain H3B36 using single molecule, real-time sequencing technology on a PacBio RS II instrument. The complete genome of strain H3B36 was 2,778,379 bp and contained 2,853 protein-coding genes, 12 rRNA genes, and 61 tRNA genes with 58 tandem repeats, six minisatellite DNA sequences, 11 genome islands, and no CRISPR repeat region. Further analysis of epigenetic modifications revealed the presence of 11,000 m4C-type modified bases, 7,545 m6A-type modified bases, and 89,064 other modified bases. The data on the genome of this strain may provide an insight into the metabolism of N α-acetyl-α-lysine.
Moderately halophilic bacteria are a group of halophilic microorganisms that grow optimally in media containing between 3 % and 15 % (w/v) NaCl. These bacteria exhibit strong salt tolerance and are widely distributed in different high-salt habitats, such as hypersaline soils and lakes, solar salterns, and salted foods [1, 2]. To cope with the hyperosmotic conditions, these microorganisms accumulate large quantities of inorganic ions, such as K+ and Cl−, or a particular group of organic osmolytes [3, 4], such as sugars (trehalose and sucrose), sugar derivatives (glucosylglycerol and mannosylglycerate), polyols (glycerol and arabitol), phosphodiesters (di-myo-inositol phosphate), amino acids (proline, α-glutamate, and β-glutamate), and derivatives (betaine and ectoine) [5–8]. In strain H3B36, which was isolated from subsurface saline soil (3.2-m depth) in Qaidam Basin in the Qinghai province, China, we detected a special compound, N α-acetyl-α-lysine, that acts as an organic osmolyte and thermolyte (authors’ unpublished observation). The amount of N α-acetyl-α-lysine in the cell was increased and could be accumulated to a high level when strain H3B36 was subjected to salt stress or heat stress. Unlike other compatible solutes, N α-acetyl-α-lysine has only been found to date in Salinibacter ruber to date, and the molecular mechanisms through which this compound is synthesized and stored are unclear [9, 10].
Based on analysis of the 16S rRNA gene sequence, this strain is most closely related to Salinicoccus halodurans W24T (= CGMCC 1.6501T = DSM 19336T ) . The genus Salinicoccus , which was first described by Ventosa et al. [12, 13], belongs to the family Staphylococcaceae . To date, 16 validly named species of Salinicoccus have been identified; however, only six genome sequences are available. All species of the genus Salinicoccus are defined as moderately halophilic bacteria. These organisms may have potential applications in various fields, including as additives in the food industry; for production of polymer compounds, enzymes, and stress protectants; and in environmental protection and biodegradation [14–19].
To obtain insights into the metabolic pathway of N α-acetyl-α-lysine and explore the genome of the Salinicoccus spp, we performed complete genome sequence analysis and annotation of Salinicoccus halodurans H3B36.
Classification and features
Strain H3B36 (Table 1) was isolated from a subsurface saline soil sample (3.2 m depth) from the Qaidam Basin of China by enriching in liquid medium at 37 °C and then plating on agar medium until single colonies were obtained. The 16S rRNA gene sequence of strain H3B36 and other available 16S rRNA gene sequences of closely related species collected from the EzTaxon-e database were used to construct a phylogenetic tree (Fig. 1) . CLUSTAL_X was used to generate alignments . After trimming, the alignments were converted to the MEGA format, and a phylogenetic tree was constructed. The evolutionary history was inferred using the maximum likelihood method based on the Kimura 2-parameter model within MEGA software version 5.10 [22, 23]. Taxonomic analysis showed that strain H3B36 was most closely related to Salinicoccus halodurans W24 T with 99.9 % 16S rRNA gene sequence identity, and as such, strain H3B36 was classified as a strain of Salinicoccus halodurans .
The cell morphology of strain H3B36 was determined using scanning electron microscopy (Fig. 2). Microscopically, cells of strain H3B36 were spherical and measured approximately 0.9 μm in diameter. Cells occurred singly or in pairs, tetrads, or irregular clumps at early growth stages. Colonies on GMH agar medium were white, opaque, circular, and slight convex. Cells were able to grow at a temperature range from 4 to 42 °C, with optimum growth observed around 30 °C in GMH medium. Analysis of growth in GMH medium with different NaCl concentrations, the strain grew well when NaCl ranged from 2 to 18 % (w/v) and could not grow in medium without NaCl or with NaCl at concentrations of more than 20 % (w/v). Optimal growth occurred between 4 % and 6 % (w/v) NaCl.
Genome sequencing information
Genome project history
Salinicoccus halodurans H3B36 was selected for genome sequencing because we observed the presence of a unique compatible solute for protection and potential industrial applications. The complete genome sequence has been deposited in GenBank under the accession number CP011366. Sequencing, annotation, and analysis were performed at WUHAN Institute of Biotechnology, China. The project information and its association with MIGS version 2.0 are shown in Table 2.
Growth conditions and genomic DNA preparation
Salinicoccus halodurans H3B36 was grown aerobically in GMH medium containing 5 g/L casamino acid, 5 g/L yeast extract, 4 g/L MgSO4 · 7H2O, 2 g/L KCl, 0.036 g/L FeSO4 · 7H2O, 0.36 mg/L MnCl2 · 7H2O, and 60 g/L NaCl, at pH 7.0 (titrated with 1 M NaOH). Genomic DNA from freshly grown cells harvested in the exponential growth phase was extracted using the QIAGEN Genomic DNA Buffer Set and QIAGEN Genomic-tip 100/G according to the manufacturer’s protocols. The prepared DNA was evaluated on a 0.75 % agarose gel to verify the integrity of the molecular weight fragments. Qualification and quantification of the prepared DNA sample was measured with a NanoDrop instrument (Thermo Scientific, Wilmington, MA, USA) and Qubit (Life Technologies, Grand Island, NY, USA) to confirm the suitability of the DNA sample for high-throughput next-generation sequencing.
Genome sequencing and assembly
The genome of Salinicoccus halodurans H3B36 was sequenced using third-generation sequencing technology on a PacBio RS II instrument. The analysis produced a total of 573,153,827 bp, and 54,457 post-filter reads with a mean length of 10,524 bp were obtained. The Hierarchical Genome Assembly Processing pipeline, version 2.2.0, was used to assemble the genome [24–26]. Long reads were selected as the seed sequences for constructing preassemblies, and the other short reads were mapped to the seeds using BLASTR software for alignment, which corrected the errors in the long reads and thus increased the accuracy rating of bases more than 99 %. Based on this analysis, we obtained 95.7 M high-quality reads with an average length of 12,910 bp. Using the overlap-layout-consensus (OLC) algorithms to debug the parameters, we adopted Celera assembler software for assembly. To improve the assembly, the raw data were mapped to the assembled reference sequence to remove any fine-scale errors using Quiver software. Low-depth contigs were then removed, and the rest of the contigs were connected using Minumus2 software. Finally, the data were assembled de novo to one final 2,778,378-bp complete contig with 212 × depth of coverage.
The RAST Prokaryotic Genome Annotation Server was used to predict protein-coding open reading frames, tRNAs, and structural RNA genes . The Cluster of Orthologous Groups, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, Swiss-Prot, and Non-Redundant Protein databases were used to annotate the predicted genes [28–32]. Pfam databases were used to predicted genes with conserved domains . Transmembrane helices and signal peptides were identified using TMHMM and SignalP, version4.1, respectively [34, 35]. Tandem Repeat Finder software was used to predict tandem repeat sequences, and Misa software was used to find the minisatellite DNA sequences . Genome islands were analyzed using IslandViewer software, which integrates three software programs (IslandPick, SIGI-HMM, and IslandPath-DIMOB) and combines the Virulence Factor and Antibiotic Resistance Gene databases [37, 38]. In addition, the CRISPR motif was identified using CRISPR II software . Analysis of the raw data was performed to identify loci having epigenetic modifications (i.e., m4C, m6A, and other modification) due to the dynamic characteristics of the raw data [40, 41]. The Restriction Enzyme Database was used to identify the genes involved in the restriction modification system .
The complete genome sequence of Salinicoccus halodurans H3B36 was found to be 2,778,378 bp and had a G + C content of 44.54 %. No plasmids were found. RAST predicted 2,853 coding sequences, 61 tRNA genes, and 16 structural RNA genes. The predicted CDSs represented 88.79 % of the total genome sequence, with an average length of 864.72 bp. Genome analysis showed that the genome of strain H3B36 contained 58 tandem repeats, six minisatellite DNA sequences, and 11 genome islands. Further analysis of epigenetic modifications revealed 11,000 m4C-type modified bases, 7,545 m6A-type modified bases, and 89,064 other modified bases in the genome. Furthermore, several restriction modification genes were found, with eight belonging to the type I system, three belonging to the type II system, and one belonging to the type IV system. The genome statistics and gene distributions into COG functional categories are presented in Tables 3 and 4, respectively. The circular representation of the bacterial genome was drawn using CGview software (Fig. 3) .
Insights from the genome sequence
Genome analysis showed that Salinicoccus halodurans H3B36 contained many genes related to the stress response, such as choline and betaine transporters, glycerol uptake facilitator protein, cold-shock protein, chaperones proteins, and others. These genes allowed the strain to cope with different environmental stresses. Experimentation and additional analysis of these genes may help to elucidate the mechanisms mediating the stress response and facilitate the development of Salinicoccus halodurans H3B36 for use in industry applications. In addition, several genes encoding hydrolases, including amylase (1), protease (19), pullulanase (2), lipase (3), phosphoesterase (5), and glucosidase (4), were identified in the genome. Hydrolases are highly valuable resources for some specific industrial processes, and hydrolases from various extremophiles may have many advantages [14, 19]. These results indicated that Salinicoccus halodurans H3B36 might have the potential for application in industrial biotechnology as a producer of miscellaneous hydrolases.
N α-acetyl-α-lysine was found play a key role in protecting Salinicoccus halodurans H3B36 cells under different stresses (unpublished observation by Kai Jiang, Yanfen Xue and Yanhe Ma). Genome annotations showed that lysine may be synthesized through the acetyl-dependent diaminopimelic acid pathway in Salinicoccus halodurans H3B36. One 8-kb gene cluster containing eight genes was predicted to be involved in N α-acetyl-α-lysine biosynthesis. Six genes in the cluster map to enzymes in the acetyl-dependent diaminopimelic acid pathway, including the genes encoding aspartokinase, aspartate-semialdehyde dehydrogenase, dihydrodipicolinate synthase, dihydrodipicolinate reductase, 2,3,4,5-tetrahydropyridine-2,6-dicarboxylate N-acetyltransferase and diaminopimelate decarboxylase. N α-acetyl-α-lysine is a derivative of lysine, so this gene cluster may participate in the synthesis of N α-acetyl-α-lysine. Further studies are required to verify this assumption and identify the metabolic pathway mediating N α-acetyl-α-lysine biosynthesis in Salinicoccus halodurans H3B36.
This is the first report describing the genome sequence of Salinicoccus halodurans . The genome size of Salinicoccus halodurans H3B36 (2.78 M) is larger than the other sequenced members of genus Salinicoccus including Salinicoccus sp. SV-16 (2.59 M), Salinicoccus luteus DSM 17002T (2.55 M), Salinicoccus albus DSM 19776T (2.64 M), Salinicoccus carnicancri CrmT (2.67 M), and Salinicoccus roseus W12 (2.56 M). Salinicoccus halodurans H3B36 has a G + C content (44.5 %) higher than Salinicoccus albus DSM 19776T but lower than those of Salinicoccus carnicancri CrmT, Salinicoccus sp. SV-16, Salinicoccus luteus DSM 17002T , and Salinicoccus roseus strain W12 (47.9 %, 48.7 %, 49.1 % and 50.0 %, respectively). Further comparative genomic study shows that the N α-acetyl-α-lysine related gene cluster is also found in other sequenced members of genus Salinicoccus . The gene cluster in Salinicoccus sp. SV-16, Salinicoccus luteus DSM 17002T , Salinicoccus carnicancri CrmT, and Salinicoccus roseus W12 containing eight genes are similar to that in Salinicoccus halodurans H3B36. Salinicoccus albus DSM 19776T has a slight discrepancy, which lacks aspartokinase in its gene cluster. The genome of Salinicoccus halodurans H3B36 provides important insights into our understanding of the metabolism of N α-acetyl-α-lysine. Furthermore, the sequence of Salinicoccus halodurans H3B36 provides useful information and may contribute to facilitate applications of genus Salinicoccus in industrial biotechnology.
The Hierarchical Genome Assembly Processing
Rapid Annotation using Subsystem Technology
Kushner DJ, Kamekura M. Physiology of halophilic eubacteria. In: Rodriguez-Valera F, editor. Halophilic bacteria. Boca Ratón: CRC Press; 1988. p. 109–40.
Ventosa A. Taxonomy of moderately halophilic heterotrophic eubacteria. In: Rodriguez-Valera F, editor. Halophilic bacteria. Boca Ratón: CRC Press; 1988. p. 71–84.
Galinski EA, Trüper HG. Microbial behaviour in salt-stressed ecosystems. FEMS Microbiol Rev. 1994;15:95–108.
Roberts MF. Organic compatible solutes of halotolerant and halophilic microorganisms. Saline Systems. 2005;1:5.
Severin J, Wohlfarth A, Galinski EA. The predominant role of recently discovered tetrahydropyrimidines for the osmoadaptation of halophilic eubacteria. J Gen Microbiol. 1992;138:1629–38.
da Costa MS, Santos H, Galinski EA. An overview of the role and diversity of compatible solutes in Bacteria and Archaea. Adv Biochem Eng Biotechnol. 1998;61:117–53.
Oren A. Microbial life at high salt concentrations: phylogenetic and metabolic diversity. Saline Systems. 2008;4:2.
Klahn S, Hagemann M. Compatible solute biosynthesis in cyanobacteria. Environ Microbiol. 2011;13:551–62.
Oren A, Heldal M, Norland S, Galinski EA. Intracellular ion and organic solute concentrations of the extremely halophilic bacterium Salinibacter ruber. Extremophiles. 2002;6:491–8.
Antón J, Oren A, Benlloch S, Rodríquez-Valera F, Amann R, Rosselló-Mora R. Salinibacter ruber gen. nov., sp. nov., a novel, extremely halophilic member of the Bacteria from saltern crystallizer ponds. Int J Syst Evol Microbiol. 2002;52:485–91.
Wang XW, Xue YF, Yuan SQ, Zhou C, Ma YH. Salinicoccus halodurans sp. nov., a moderate halophile from saline soil in China. Int J Syst Evol Microbiol. 2008;58:1537–41.
Validation List no. 34. Validation of the publication of new names and new combinations previously effectively published outside the IJSB. Int J Syst Bacteriol. 1990;40:320–321. http://dx.doi.org/10.1099/00207713-40-3-320.
Ventosa A, Márquez MC, Ruizberraquero MC, Kocur M. Salinicoccus roseus gen. nov, sp. Nov, a new moderately halophilic gram-positive coccus. Syst Appl Microbiol. 1990;13:29–33.
Margesin R, Schinner F. Potential of halotolerant and halophilic microorganisms for biotechnology. Extremophiles. 2001;5:73–83.
Tokunaga H, Ishibashi M, Arakawa T, Tokunaga M. Highly efficient renaturation of beta-lactamase isolated from moderately halophilic bacteria. Febs Letters. 2004;558:7–12.
Le Borgne S, Paniagua D, Vazquez-Duhalt R. Biodegradation of organic pollutants by halophilic bacteria and archaea. J Mol Microbiol Biotechnol. 2008;15:74–92.
Harishchandra RK, Wulff S, Lentzen G, Neuhaus T, Galla HJ. The effect of compatible solute ectoines on the structural organization of lipid monolayer and bilayer membranes. Biophys Chem. 2010;150:37–46.
Lentzen G, Schwarz T. Extremolytes: Natural compounds from extremophiles for versatile applications. Appl Microbiol Biotechnol. 2006;72:623–34.
Ventosa A, Nieto JJ. Biotechnological applications and potentialities of halophilic microorganisms. World J Microbiol Biotechnol. 1995;11:85–94.
Kim OS, Cho YJ, Lee K, Yoon SH, Kim M, Na H, et al. Introducing EzTaxon-e: a prokaryotic 16S rRNA gene sequence database with phylotypes that represent uncultured species. Int J Syst Evol Microbiol. 2012;62:716–21.
Thompson JD, Higgins DG, Gibson TJ. CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Res. 1994;22:4673–80.
Felsenstein J. Evolutionary trees from DNA sequences: a maximum likelihood approach. J Mol Evol. 1981;17:368–76.
Tamura K, Peterson D, Peterson N, Stecher G, Nei M, Kumar S. MEGA5: Molecular Evolutionary Genetics Analysis using Maximum Likelihood, Evolutionary Distance, and Maximum Parsimony Methods. Mol Biol Evol. 2011;128:2731–9.
Chin CS, Alexander DH, Marks P, Klammer AA, Drake J, Heiner C, et al. Nonhybrid, finished microbial genome assemblies from long-read SMRT sequencing data. Nat Methods. 2013;10:563–9.
Chaisson MJ, Tesler G. Mapping single molecule sequencing reads using basic local alignment with successive refinement (BLASR): application and theory. BMC Bioinformatics. 2012;13(1):238.
Miller JR, Delcher AL, Koren S, Venter E, Walenz BP, Brownley A, et al. Aggressive assembly of pyrosequencing reads with mates. Bioinformatics. 2008;24(24):2818–24.
Aziz RK, Bartels D, Best AA, DeJongh M, Disz T, Edwards RA, et al. The RAST Server: rapid annotations using subsystems technology. BMC Genomics. 2008;9(1):75.
Tatusov RL, Galperin MY, Natale DA, Koonin EV. The COG database: a tool for genome-scale analysis of protein functions and evolution. Nucleic Acids Res. 2000;28:33–6.
Ashburner M, Ball CA, Blake JA, Botstein D, Butler H, Cherry JM, et al. Gene Ontology: tool for the unification of biology. Nat Genet. 2000;25:25–9.
Kanehisa M, Goto S, Kawashima S, Okuno Y, Hattori M. The KEGG resource for deciphering the genome. Nucleic Acids Res. 2004;32 suppl 1:D277–80.
Magrane M, Consortium U. UniProt Knowledgebase: a hub of integrated protein data. Database J. Biol Databases Curation. 2011; 2011: bar009.
Pruitt KD, Tatusova T, Brown GR, Maglott DR. NCBI Reference Sequences (RefSeq): current status, new features and genome annotation policy. Nucleic Acids Res. 2012;40:D130–5.
Finn RD, Mistry J, Tate J, Coggill P, Heger A, Pollington JE, et al. The Pfam protein families database. Nucleic Acids Res. 2010;38:D211–22.
Krogh A, Larsson B, von Heijne G, Sonnhammer ELL. Predicting transmembrane protein topology with a hidden Markov model: application to complete genomes. J Mol Biol. 2001;305:567–80.
Petersen TN, Brunak S, von Heijne G, Nielsen H. SignalP 4.0: discriminating signal peptides from transmembrane regions. Nat Methods. 2011;8:785–6.
Benson G. Tandem repeats finder: a program to analyze DNA sequences. Nucleic Acids Res. 1999;27(2):573–80.
Langille MGI, Brinkman FSL. IslandViewer: an integrated interface for computational identification and visualization of genomic islands. Bioinformatics. 2009;25(5):664–5.
Juhas M, van der Meer JR, Gaillard M, Harding RM, Hood DW, Crook DW. Genomic islands: tools of bacterial horizontal gene transfer and evolution. FEMS Microbiol Rev. 2009;33(2):376–93.
Grissa I, Vergnaud G, Pourcel C. The CRISPRdb database and tools to display CRISPRs and to generate dictionaries of spacers and repeats. BMC Bioinformatics. 2007;8(1):172.
Flusberg BA, Webster DR, Lee JH, Travers KJ, Olivares EC, Clark TA, et al. Direct detection of DNA methylation during single-molecule, real-time sequencing. Nat Methods. 2010;7(6):461–U72.
Davis BM, Chao MC, Waldor MK. Entering the era of bacterial epigenomics with single molecule real time DNA sequencing. Curr Opin Microbiol. 2013;16(2):192–8.
Roberts RJ, Vincze T, Posfai J, Macelis D. REBASE-a database for DNA restriction and modification: enzymes, genes and genomes. Nucleic Acids Res. 2015;43:D298–9.
Stothard P, Wishart DS. Circular genome visualization and exploration using CGView. Bioinformatics. 2005;21(4):537–9.
Field D, Garrity G, Gray T, Morrison N, Selengut J, Sterk P, et al. The minimum information about a genome sequence (MIGS) specification. Nat Biotechnol. 2008;26:541–7.
Woese CR, Kandler O, Wheelis ML. Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya. Proc Natl Acad Sci U S A. 1990;87:4576–9.
Gibbons NE, Murray RGE. Proposals concerning the higher taxa of bacteria. Int J Syst Bacteriol. 1978;28:1–6.
Murray RGE. The Higher Taxa, or, a Place for Everything…? Bergey's Manual of Systematic Bacteriology. 1984;1:31–4.
Validation List 132. List of new names and new combinations previously effectively, but not validly, published. Int J Syst Evol Microbiol. 2010;60:469–472.
Hauderoy P, Ehringer G, Guillot G, Magrou J, Prévot AR, Rossetti D, et al. Dictionnaire des Bactéries Pathogènes. 2nd ed. Paris: Masson et Cie; 1953. http://dx.doi.org/10.1099/ijs.0.022855-0.
Skerman VBD, McGowan V, Sneath PHA. Approved Lists of Bacterial Names. Int J Syst Bacteriol. 1980;30:225–420.
Schleifer KH, Bell JA. Family VIII. Staphylococcaceae fam. nov. In: De Vos P, Garrity G, Jones D, Krieg NR, Ludwig W, Rainey FA, et al., editors. Bergey's Manual of Systematic Bacteriology. New York: Springer; 2009. p. 392.
This work was supported by the Ministry of Sciences and Technology of China (grant nos. 2011CBA00800, 2013CBA733900, 2012AA022100, and 2011AA02A206).
The authors have declared that no competing interests exist.
KJ, YFX and YHM designed research and wrote the manuscript. KJ characterized strain H3B36 and performed the experiments. All authors read and approved the final manuscript.
About this article
Cite this article
Jiang, K., Xue, Y. & Ma, Y. Complete genome sequence of Salinicoccus halodurans H3B36, isolated from the Qaidam Basin in China. Stand in Genomic Sci 10, 116 (2015) doi:10.1186/s40793-015-0108-8
- Qaidam Basin
- Moderately halophilic
- Salinicoccus halodurans strain
- Genome sequencing