Open Access

Complete genome sequence of and proposal of Thermofilum uzonense sp. nov. a novel hyperthermophilic crenarchaeon and emended description of the genus Thermofilum

  • Stepan V. Toshchakov1Email author,
  • Aleksei A. Korzhenkov1,
  • Nazar I. Samarov1,
  • Ilia O. Mazunin1,
  • Oleg I. Mozhey1,
  • Ilya S. Shmyr2,
  • Ksenia S. Derbikova3,
  • Evgeny A. Taranov3,
  • Irina N. Dominova1,
  • Elizaveta A. Bonch-Osmolovskaya3,
  • Maxim V. Patrushev1,
  • Olga A. Podosokorskaya3 and
  • Ilya V. Kublanov3
Standards in Genomic Sciences201510:122

https://doi.org/10.1186/s40793-015-0105-y

Received: 6 July 2015

Accepted: 2 November 2015

Published: 9 December 2015

Abstract

A strain of a hyperthermophilic filamentous archaeon was isolated from a sample of Kamchatka hot spring sediment. Isolate 1807-2 grew optimally at 85 °C, pH 6.0-6.5, the parameters being close to those at the sampling site. 16S rRNA gene sequence analysis placed the novel isolate in the crenarchaeal genus Thermofilum; Thermofilum pendens was its closest valid relative (95.7 % of sequence identity). Strain 1807-2 grew organothrophically using polysaccharides (starch and glucomannan), yeast extract or peptone as substrates. The addition of other crenarchaea culture broth filtrates was obligatory required for growth and could not be replaced by the addition of these organisms’ cell wall fractions, as it was described for T. pendens. The genome of strain 1807-2 was sequenced using Illumina and PGM technologies. The average nucleotide identities between genome of strain 1807-2 and T. pendens strain HRK 5T and “T. adornatus” strain 1910b were 85 and 82 %, respectively. On the basis of 16S rRNA gene sequence phylogeny, ANI calculations and phenotypic differences we propose a novel species Thermofilum uzonense with the type strain 1807-2T (= DSM 28062T = JCM 19810T). Project information and genome sequence was deposited in Genbank under IDs PRJNA262459 and CP009961, respectively.

Keywords

Thermofilum Crenarchaeota hyperthermophileKamchatkaPhylogenyPolysaccharides hydrolysis

Introduction

Currently, the archaeal phylum Crenarchaeota comprises five orders: Thermoproteales , Sulfolobales , Desulfurococcales , Acidilobales and Fervidicoccales [1]. Thermoproteales representatives are characterized as rod-shaped extreme thermophiles and hyperthermophiles, growing either auto- or heterotrophically, using different redox pairs to gain energy as well as performing fermentation of organic substrates [2]. The order consists of two families: Thermoproteaceae [3], and Thermofilaceae [4]; the second one is a deeply branching lineage, consisting so far only one validly published genus and species, Thermofilum pendens isolated from a solfataric hot spring in Iceland [5] and characterized as an anaerobic hyperthermophilic, moderately acidophilic chemoorganotrophic archaeon utilizing peptides as the energy source and sulfur as the electron acceptor. Its growth is obligatory dependent on Thermoproteus tenax polar lipid fraction. Other T. pendens strains were isolated from solfataras of Yellowstone National Park (USA) and Vulcano Island (Italy) [4]. Notably, one of them described non-validly as a separate species “Thermofilum librum” has 100 % 16S rRNA gene sequence identity with T. pendens , but does not require the addition of other organisms’ cell components [6]. Recently, another species “Thermofilum adornatus” strain 1910b was isolated from a black mud pit (Kamchatka, Russia) and its genome was sequenced [7].

Here we describe another Thermofilum strain 1807-2, report its genomic sequence, what allow us to propose a novel species Thermofilum uzonense strain 1807-2T. This new data expands the knowledge on physiology and diversity of this deep lineage in archaeal domain.

Organism Information

Classification and features

In 2008, a gray mud sample was collected from the hot spring (T 83 °C, pH 6.2) located in Orange Thermal Field, Uzon Caldera, Kamchatka, Russia (54.30 N 160.00 E). An enrichment culture was obtained using strictly anaerobic modified freshwater Pfennig medium with cellobiose and yeast extract (2 g l−1 and 1 g l−1, respectively) as substrates [8]. After 4 days of incubation at 84 °C at pH 5.8 two different types of cells – extremely thin rods and regular small cocci – were detected in the enrichment culture.

Strain 1807-2T was purified by serial dilution technique on the same medium in the presence of 1/100 (v/v) Fervidicoccus fontis strain 1910a culture broth as it was performed for “Thermofilum adornatus” strain 1910b [7].

Cells of strain 1807-2T were non-motile thin straight or curved filaments (Fig. 1), 0.15–0.3 μm width and 2–100 μm length.
Fig. 1

Electron micrograph of Thermofilum uzonense strain 1807-2T. Bar, 0.5 μm. Electron micrograph of negatively stained cell of Thermofilum uzonense strain 1807-2T. Cells were grown on glucose containing medium at 85 °C and incubated for two days (late exponential phase of growth). Bar, 0.5 μm

Strain 1807-2T was a hyperthermophile and obligate anaerobe. It grew optimally at 85 °C and pH 6.0–6.5 without sodium chloride in the medium. In the presence of 10 g l−1 NaCl growth of the strain ceased completely. Addition of at least 25 mg l−1 of yeast extract was mandatory. Peptone, yeast extract, starch and glucomannan were used as substrates for growth while amorphous cellulose [9] and filter paper, mannan, amorphous chitin [10], chitosan, glycerol and carbon monoxide did not support it (Table 1). Addition of 1/100 (v/v) of culture broth filtrates of other Crenarchaeota ( Fervidicoccus fontis , Desulfurococcus kamchatkensis or Pyrobaculum sp.) which served, most probably, as a source of growth factors, was obligatory required for growth of strain 1807-2T. Filtrates could not be replaced by cell wall-fractions of these organisms, or bacterial (Caldicellulosiruptor kronotskyensis) culture broth filtrates.

Strain 1807-2T was deposited in DSMZ (German collection of microorganisms and cell cultures) under accession number DSM 28062, and in JCM (Japan Collection of Microorganisms) under accession number JCM 19810.

16S rRNA gene-based phylogenetic analysis of strain 1807-2T placed it into Thermofilaceae family being most closely related to Thermofilum pendens Hrk5T showing 95.7 % sequence identity according to calculations, considered used substitution model (Fig. 2). For the analysis a complete 16S rRNA gene of strain 1807-2T and almost complete (>1300 nt) sequences of its 50 best BLAST hits from GenBank nr/nt database, filtered through 100 % identity filter were used (final dataset included 38 sequences). 13 representative of Thermoproteaceae were used as an outgroup for the analysis (Additional file 5).
Fig. 2

16S rRNA gene Maximal-likelihood phylogenetic tree of representatives of Thermofilaceae family. The tree was constructed using the Maximum Likelihood method based on the Tamura-Nei model [39]. The tree with the highest log likelihood (−5739.3765) is shown. The percentage of trees in which the associated taxa clustered together (bootstrap test of 1000 replications) is shown next to the nodes. Initial tree(s) for the heuristic search were obtained by applying the Neighbor-Joining method to a matrix of pairwise distances estimated using the Maximum Composite Likelihood (MCL) approach. A discrete Gamma distribution was used to model evolutionary rate differences among sites (4 categories (+G, parameter = 0.2411)). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 38 nucleotide sequences; all were longer than 1300 nucleotides. All positions containing gaps and missing data were eliminated. There was a total of 1.227 positions in the final dataset. Evolutionary analyses were conducted in MEGA6 [40]. Thermoproteaceae branch includes 13 sequences (Additional file 5). Cultivated strains are underlined. Thermofilum uzonense strain 1807-2T is in bold. Complete 16S rRNA gene of Desulfurococcus kamchatkensis (NC_011766.1, Desulfurococcales order) was chosen as an out-group. Bar, 2 substitutions per 100 nucleotides

On 1st of May 2015 both RDP (Release 11, Update 3) and Silva (SSU r122) databases contain altogether 400 unique 16S rRNA genes of Thermofilaceae family clones and isolates. Most of them were partial, hence were not involved in the mentioned-above phylogenetic analysis. The analysis of distribution of their isolation sources was performed using our homemade software GetIsolationSources [11]. It searches for the GenBank accession numbers in SILVA, RDP and other databases, containing it, and extracts the information, residing under modifiers “description”, “accession”, “isolation source”, “country” and “references” from the respective GenBank records. Analysis revealed that the majority of Thermofilaceae family clones and pure cultures were obtained from hot springs, both terrestrial and marine. A few others were collected from various non-thermal environments. All GenBank IDs of these 16S rRNA genes are listed in Additional file 1.

Genome sequencing information

Genome project history

The sequencing project started in May 2013 and finished in August 2014. Due to the fact that both short and long insert libraries were used for sequencing, the obtained circular genomic contig can be considered as a finalized genome sequence. The complete genome sequence of T. uzonense strain 1807-2T has been deposited in DDBJ/EMBL/GenBank under the accession number CP009961. Related project information and sample details have been deposited in NCBI database under accession numbers PRJNA262459 and SAMN03083278, respectively (Table 2).
Table 1

Classification and general features of Thermofilum uzonense strain1807-2T [31]

MIGS ID

Property

Term

Evidence codea

 

Current classification

Domain Archaea

TAS [32]

Phylum Crenarchaeota

TAS [33]

Class Thermoprotei

TAS [34]

Order Thermoproteales

TAS [3, 4, 3537]

Family Thermofilaceae

TAS [19]

Genus Thermofilum

TAS [5]

Species Thermofilum uzonense

IDA

Type strain 1807-2

IDA

 

Gram stain

Not reported

 
 

Cell shape

Thin straight or curved rods

IDA

 

Motility

Non motile

IDA

 

Sporulation

Non-sporulating

IDA

 

Temperature range

70–90 °C

IDA

 

Optimum temperature

85 °C

IDA

 

pH range; optimum

5.5–7.0; 6.0–6.5

IDA

 

Carbon source

Yeast extract, peptone, starch, glucomannan

IDA

 

Energy source

Yeast extract, peptone, starch, glucomannan

 

MIGS-6

Habitat

Hot spring

 

MIGS-6.3

Salinity

0–0.5 % NaCl (w/v). Optimum 0 %.

IDA

MIGS-22

Oxygen

Anaerobe

IDA

MIGS-15

Biotic relationship

Free living

IDA

MIGS-14

Pathogenicity

Non-pathogenic

NAS

Biosafety level

1

NAS

Isolation

Water/sediment of hot spring, Uzon Caldera, Kamchatka

IDA

MIGS-4

Geographic location

Uzon Caldera, Kamchatka, Far-East Russia

IDA

MIGS-5

Sample collection time

2008

IDA

MIGS-4.1 MIGS-4.2

Latitude

54 30.382

IDA

Longitude

160 00.103

IDA

MIGS-4.3

Depth

Surface

IDA

MIGS-4.4

Altitude

663 m

IDA

a Evidence codes - IDA inferred from direct assay, TAS traceable author statement (i.e., a direct report exists in the literature), NAS non-traceable author statement (i.e., not directly observed for the living, isolated sample, but based on a generally accepted property for the species, or anecdotal evidence). These evidence codes are from the Gene Ontology project [38]

Table 2

Project information and its association with MIGS version 2.0 compliance [31]

MIGS ID

Property

Term

MIGS 31

Finishing quality

Finished

MIGS-28

Libraries used

Illumina Nextera fragment library (insert mean length of 175 bp)

PGM mate-paired library (insert mean length of 2400 bp)

MIGS 29

Sequencing platforms

Ion Torrent, Illumina, Sanger

MIGS 31.2

Fold coverage

Ion Torrent 13.6 ×

Illumina 180.4 ×

MIGS 30

Assemblers

CLC Bio [13]

MIGS 32

Gene calling method

GeneMarKS+

 

Locus Tag

MA03

 

Genbank ID

CP009961

 

GenBank Date of Release

April 1, 2015

 

GOLD ID

Gp0108853

 

BIOPROJECT

PRJNA262459

MIGS 13

Source Material Identifier

DSM 28062

 

Project relevance

Evolution, Diversity

Table 3

Genome statistics

Attribute

Number of genes

% of Total genesa

Genome size (bp)

1,611,988

100.00

DNA codingb (bp)

1,270,203

78.8

DNA G+C (bp)

772,789

47.9

DNA scaffolds

1

100.00

Total genes

1697

100.00

Protein coding genes

1455

85.7

RNA genes

50

3.0

Pseudo genes

192

11.3

Genes in internal clusters

NDc

NDc

Genes with function prediction

1334

78.6

Genes assigned to COGs

1389

81.9

Genes with Pfam domains

1066

62.8

Genes with signal peptides

343

20.2

Genes with transmembrane helices

129

7.6

CRISPR repeats

2

a) The total is based on either the size of the genome in base pairs or the total number of genes in the annotated genome

b) Corresponding to functional CDS. Pseudogenes are not included in this calculation

c) ND not determined

Growth conditions and genomic DNA preparation

T. uzonense strain 1807-2T was grown in medium mentioned above with glucose and yeast extract (1 g l−1 and 0.5 g l−1, respectively) as substrates and in the presence of 1/100 (v/v) Desulfurococcus kamchatkensis strain 1221n culture broth as a source of growth factors at 85 °C during 4 days. Cell-free culture broth of D. kamchatkensis was obtained by filtration of grown cells through 0.22 μm filter. For that, cells of strain 1221n were grown on the same medium containing glucose and yeast extract as growth substrates at optimal conditions [12]. After cultivation, cells of strain 1807-2T were disrupted with glass beads using Minilys homogenizer (Bertin technologies, France) and DNA was extracted using QIAamp DNA mini kit (Qiagen, Netherlands) according to the manufacturers’ instructions.

Genome sequencing and assembly

For sequencing of T. uzonense genome both fragment and mate-paired libraries were used. Fragment library for Miseq paired-end sequencing was prepared from 50 ng genomic DNA with NexteraTM fragment library kit (Illumina, San Diego, CA, USA) according to manufacturer instructions. Analysis of library size distribution showed the mean insert size of 175 bp. Sequencing of this library using MiSeq instrument resulted in 932,095 pairs of 250 bp reads which were subjected to stringent quality and adapter trimming with the corresponding tool of CLCBio Genomics Workbench 7.5 (Qiagen, Netherlands). After trimming and filtering procedures 911,060 read pairs were used for assembly.

The mate-paired library with target insert size of 2400 bp for Ion Torrent sequencing was prepared from 3 μg of DNA with SOLiD 5500 mate-paired library kit (Life Technologies, Carlsbad, CA, USA) using Ion Torrent PGM adapters for final amplification. Library was sequenced on a 314 chip resulting in 300,306 single sequences. The internal adapter used for library construction was trimmed during import procedure to CLC Genomics Workbench. After quality and length filtering totally 197,320 read pairs were used for de novo assembly guidance and scaffolding (single reads were excluded from further analysis).

The initial assembly was made with CLCBio de novo assembler using word size of 64 and bubble size of 500 bp [13]. Since overall quality of MiSeq reads is generally much higher than PGM reads quality, the Illumina reads were used for assembly of contigs, while PGM reads used only in “guidance only” mode for de Bruijn graph ambiguities resolution. Twenty two scaffolds with L50 of 456,782 bp were obtained. After in silico closure of gaps with GapFiller v1.11 [14] contigs were subjected to the second round of scaffolding and gapfilling with SSPACE v.2.0 [15] and GapFiller. Finally one gapless contig of 1,610,790 bp was obtained. Assembly validation was accomplished by mapping of all high-quality MiSeq reads to the final chromosome. Analysis of the mapping revealed 3 problematic regions characterized by the enrichment of mapping conflicts and unaligned read ends. These regions were amplified by PCR and sequenced by Sanger method with ABI 3730XL DNA analyzer (Life Technologies, Carlsbad, CA, USA). Chromosome circularity was confirmed by PCR with outward-oriented primers and subsequent Sanger sequencing. After all correction procedures the length of Thermofilum uzonense strain 1807-2T circular chromosome was 1,611,988 bp.

Genome annotation

Identification of genes and primary annotation was performed with PGAAP pipeline [16]. As a part of the pipeline, protein-coding genes were detected with GeneMarkS+ [17], tRNA genes were identified with tRNA-scan-SE [18] and rRNA genes were identified with blastn search against a curated NCBI rRNA reference set.

Assignment of predicted CDS to the clusters of orthologous groups (COGs) was made using BLAST [19] against the latest version of COG database [20] with maximal e-value of 10−5. Identification of conserved domains families was performed using HMMER hmmscan service [21]. Proteins harboring signal peptides and transmembrane helices were identified with Phobius server [22] Twin-arginine signal peptides were predicted using TatP server [23], while non-classical signal peptides were predicted using SecretomeP server [24]. Other predictions were done according to the genome annotation protocol [25].

Genome properties

The genome of T. uzonense strain 1807-2T consists of one circular chromosome of a total length of 1,611,988 base pairs (47.9 % G+C content). A total of 1697 genes were predicted, 1455 of which are protein-coding genes (CDS), 50 are RNA genes and 192 are pseudogenes. The genome has one ribosomal operon consisting of single copies of 16S and 23S ribosomal RNA genes, while 5S gene is located 300 kb apart from it. A search for IS elements using IS Finder database [26] showed that genome contains two IS200/IS605 family IS elements, one of which is inactive due to disrupted transposase gene. The chromosome also contains two CRISPR stretches of total length about 13 kb [27].

Approximately 70 % of CDS (1019 of 1455) were associated with Clusters of Orthologous Groups (COGs). Since the majority of individual domains of multidomain proteins were assigned to different COGs the number of COGs is higher than the number of proteins with COGs: 1389 (Table 3). The distribution of genes into COGs functional categories is presented in Table 4. Graphical map of T. uzonense strain 1807-2T circular chromosome is presented on Fig. 3.
Table 4

Number of genes associated with general COG functional categories

Code

Value

% age

Description

J

146

10.0

Translation, ribosomal structure and biogenesis

A

0

0.0

RNA processing and modification

K

81

5.6

Transcription

L

81

5.6

Replication, recombination and repair

B

0

0.0

Chromatin structure and dynamics

D

4

0.3

Cell cycle control, Cell division, chromosome partitioning

V

79

5.4

Defense mechanisms

T

19

1.3

Signal transduction mechanisms

M

35

2.4

Cell wall/membrane biogenesis

N

12

0.8

Cell motility

U

13

0.9

Intracellular trafficking and secretion

O

63

4.3

Posttranslational modification, protein turnover, chaperones

C

116

8.0

Energy production and conversion

G

121

8.3

Carbohydrate transport and metabolism

E

122

8.4

Amino acid transport and metabolism

F

48

3.3

Nucleotide transport and metabolism

H

69

4.7

Coenzyme transport and metabolism

I

24

1.6

Lipid transport and metabolism

P

79

5.4

Inorganic ion transport and metabolism

Q

6

0.4

Secondary metabolites biosynthesis, transport and catabolism

R

216

14.8

General function prediction only

S

55

3.8

Function unknown

436

30.0

Not in COGs

The total is based on the total number of protein coding genes in the genome

Fig. 3

Circular map of Thermofilum uzonense strain1807-2T generated with CIRCOS [41]. From outside to inside: positive strand CDSs colored by COG FCs (Clusters of Orthologous Genes Functional Categories), negative strand CDSs colored by COG FCs, RNA-genes and CRISPRs (tRNA – purple; rRNA – blue; riboswitches – green, CRISPR repeats - yellow), G+C-content, GC-skew. On the right – COG functional categories color codes

Insights from the genome sequence

Average nucleotide identity was calculated by ANI calculator [28] with default parameters. ANIs between the genomes of strain 1807-2T and T. pendens strain HRK 5T and “T. adornatus” strain 1910b were 85 and 82 %, respectively which is below the species border, proposed to be 95 % [29]. These results, together with the data, obtained during 16S rRNA gene-based phylogenetic analysis and phenotypic differences, support the proposal of the novel species. Genome analysis of T. pendens revealed a massive loss of biosynthetic pathways, supporting the observation that T. pendens grows only in nutrient-rich environments [30]. To check if this is a common property of Thermofilaceae we analyzed the presence of crenarchaeal biosynthetic COGs [30] in in silico translated proteomes of all members of this family with currently available genome sequences (assembly accession numbers GCA_000015225.1, GCA_000446015.1, GCA_000813245.1, GCA_000993805.1). Analysis revealed that all Thermofilum representatives have only 20–30 of 125 biosynthetic COGs present in almost all Bacteria and Archaea (Additional file 2). Interestingly, the number of biosynthetic protein domains which have been lost during evolution negatively correlates with genome size of Thermofilaceae family members (Additional file 3). Comparative analysis of COG functional groups distribution didn’t reveal any significant deviations showing general metabolic resemblance of Thermofilaceae (Additional file 4).

The analysis of T. pendens genome [30] revealed the possibility of growing on various polysaccharides including starch and cellulose, however none of them were tested so far. T. uzonense is able to grow on starch and glucomannan, and the genes encoding corresponding glycosidases were found in its genome. In total, 17 genes are predicted to encode various glycosidases. Two of them are predicted to be extracellular: MA03_06285 (GH57) and MA03_03765 (GH3). The first one is putative alpha-amylase, most probably responsible for extracellular starch hydrolysis, while the activity of the second one is not particularly obvious, but most likely, is a beta-glucosidase. Intracellular utilization of starch hydrolysis products could occur by means of four GH57 family glycosidases: MA03_00470, MA03_00770, MA03_05655 and one GH13 maltogenic amylase MA03_06280. Final intracellular hydrolysis of maltose could be catalyzed by alpha-glucosidases MA03_03630 (GH4) and MA03_04210 (GH122). Glycosidases MA03_06285 and MA03_06280 are localized in a gene cluster together with transporters MA03_06265 (MalG) and MA03_06270 (MalF) and maltooligosaccharide-binding proteins MA03_06275 and MA03_06290 indicating their synergetic action. Enzymes presumably involved in glucomannan hydrolysis are MA03_02580 (DUF377 domain-containing putative glycosidase), MA03_03185 (GH38), MA03_04200 (GH1), MA03_02300 (GH113). All predictions of their localization (SignalP, TatP, SecP) did not reveal any signatures of extracellular proteins, indicating rather unusual motifs, recognized by signal peptidases, or another modifications in their secretion system than the intracellular state of all these enzymes. Interestingly, putative glycosidase MA03_02580 is located in the cluster of ABC and MFS families of putative sugar transporters and solute-binding proteins: MA03_2555-2575 and MA03_2585 indicating their possible co-regulation.

Two genes encoding proteins MA03_04265 and MA03_06125 are homologous to NAD-dependant oxidoreductases, some of which could be involved in degradation of glycosidic bonds in polysaccharides (GH109); however their function in T. uzonense is unclear.

Apart from glycoside hydrolases two genes encoding carbohydrate esterases (CEs) were also found: MA03_03235 (CE14) family and MA03_04280 (CE9). Characterized enzymes of these families are predicted to be involved in metabolism of N-acetyl-glucosamines and relative compounds.

The genome contains more than 40 genes encoding peptidases of different families. Ten of them are predicted to be extracellular and four possibly are responsible for the hydrolysis of peptides during growth on peptone: subtilase (S08A family) MA03_03015, archaeal serine endopeptidase MA03_01720, thermopsin (A5 family) MA03_03850 and metalloendopeptidase (M48B family) MA03_08235.

Conclusions

Analysis of complete genome sequence of strain 1807-2T indicates that it can be proposed as a novel species Thermofilum uzonense strain 1807-2T . The majority of T. uzonense CDSs have homologs in the genomes of other Thermofilum members, and their distribution among COGs functional categories shows high level of metabolic homogeneity. As it was found for other Thermofilum representatives, massive reduction in number of proteins, contributing to biosynthetic pathways [30], has occurred in T. uzonense genome, hence, like other members of the family, its lifestyle could be characterized as opportunistic heterotroph, growing in nutrient-rich environments.

Apart from peptidic substrates, T. uzonense is able to grow on α-linked (starch) and β-linked (glucomannan) polysaccharides. While this capability was speculated in T. pendens genome paper [30], until now, it was never proven experimentally. Comparative analysis of all available Thermofilum genomes revealed two genes coding alpha-glucosidase of GH122 family and putative carbohydrate esterase of CE4 family, were present exclusively in genome of T. uzonense. Another two, coding extracellular putative amylase of GH57 family and putative endomannanase of GH113 family were found only in T. uzonense and “T. adornatus” genomes. These results suggest that the ability to hydrolyze various polysaccharides could be characteristic for Thermofilum representatives with some substrate-specific peculiarities of each individual strain. This allows one to conclude that Thermofilum members should not be regarded solely as consumers of simple organic substrates but also as primary destructors of the complex organic matter which occurs in their environments.

Taxonomic and nomenclatural proposals

Description of Thermofilum uzonense sp. nov.

Thermofilum uzonense (u.zo.nen’se N.L. neut. adj. uzonense, pertaining to the Uzon Caldera, Kamchatka, Far-East Russia, from where the type strain was isolated).

Cells are non-motile thin straight or curved filaments, 0.15–0.3 μm in width and 2–100 μm in length. Strict anaerobe. Hyperthermophile growing optimally at 85 °C and pH 6.0–6.5 in freshwater medium. Utilizes starch, glucomannan, peptone and yeast extract as the substrates. Amorphous cellulose, filter paper, mannan, amorphous chitin, glycerol and carbon monoxide do not support growth. Yeast extract and culture broth filtrate of other Crenarchaeota are required for growth. The type strain is 1807-2T (= DSM 28062T = JCM 19810T ), was isolated from a mud sample of Uzon Caldera, Kamchatka (Russia). Genome size of the type strain is 1.6 Mb. The G+C content of DNA is 47.9 mol %. The genome sequence of the strain has been deposited in DDBJ/EMBL/GenBank under the accession number CP009961.

Emended description of the genus Thermofilum

The description is based on that provided by Zillig and colleagues [5], with the following amendments. The genus contains slightly or moderately acidophilic species utilizing peptides and polysaccharides and requiring polar component lipid from Thermoproteus tenax or culture broth of other Crenarchaeota for growth. Type species: Thermofilum pendens .

Abbreviations

ANI: 

Average nucleotide identity

COG: 

Clusters of orthologous genes

DSMZ: 

German collection of microorganisms and cell cultures

FC: 

Functional categories

GH: 

Glycoside hydrolase

JCM: 

Japan collection of microorganisms

PGM: 

Ion Torrent personal genome machine

RDP: 

Ribosomal Database Project

Declarations

Acknowledgement

The work of ET, EBO, OP and IK was supported by the Russian Science Foundation (RSF) grant # № 14-24-00165. The work of MP and ID was supported by Russian Federal Targeted Program for Research and Development (FTP R&D) grant №14.575.21.0036. Work of IM and OM was supported by FTP R&D grant RFMEFI57514X0108].

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
Immanuel Kant Baltic Federal University
(2)
Pirogov Russian National Research Medical University
(3)
Winogradsky Institute of Microbiology, Research Center for Biotechnology Russian Academy of Sciences

References

  1. Perevalova AA, Bidzhieva SK, Kublanov IV, Hinrichs K-U, Liu XL, Mardanov AV, et al. Fervidicoccus fontis gen. nov., sp. nov., an anaerobic, thermophilic crenarchaeote from terrestrial hot springs, and proposal of Fervidicoccaceae fam. nov. and Fervidicoccales ord. nov. Int J Syst Evol Microbiol. 2010;60(Pt 9):2082–8.View ArticlePubMedGoogle Scholar
  2. Huber H, Huber R, Stetter KO. Thermoproteales. In: Dworkin M, Falkow S, Rosenberg E, Schleifer KH, Stackebrandt E, editors. The Prokaryotes. Springer: New York; 2006. p. 10–22.View ArticleGoogle Scholar
  3. Zillig W, Stetter KO. Validation of the publication of new names and new combinations previously effectively published outside the IJSB: list no. 8. Int J Syst Bacteriol. 1982;32:266–8.View ArticleGoogle Scholar
  4. Burggraf S, Huber H, Stetter KO. Reclassification of the crenarchael orders and families in accordance with 16S rRNA sequence data. Int J Syst Bacteriol. 1997;47:657–60.View ArticlePubMedGoogle Scholar
  5. Zillig W, Gierl A, Schreiber G, Wunderl S, Janekovic D, Stetter KO, et al. The archaebacterium thermofilum pendens represents, a novel genus of the thermophilic, anaerobic sulfur respiring thermoproteales. Syst Appl Microbiol. 1983;4:79–87.View ArticlePubMedGoogle Scholar
  6. Stetter KO. Diversity of extremely thermophilic archaebacteria. In: Brock TD, editor. Thermophiles: general, molecular, and applied microbiology. New York: Wiley; 1986. p. 39–74.Google Scholar
  7. Dominova IN, Kublanov IV, Podosokorskaya OA, Derbikova KS, Patrushev M V, Toshchakov SV. Complete genomic sequence of “Thermofilum adornatus” strain 1910bT, a hyperthermophilic anaerobic organotrophic crenarchaeon. Genome Announc. 2013;1.Google Scholar
  8. Podosokorskaya OA, Merkel AY, Kolganova TV, Chernyh NA, Miroshnichenko ML, Bonch-Osmolovskaya EA, et al. Fervidobacterium riparium sp. nov., a thermophilic anaerobic cellulolytic bacterium isolated from a hot spring. Int J Syst Evol Microbiol. 2011;61(Pt 11):2697–701.View ArticlePubMedGoogle Scholar
  9. Zhang J, Zhang J, Lin L, Chen T, Zhang J, Liu S, et al. Dissolution of microcrystalline cellulose in phosphoric acid—molecular changes and kinetics. Molecules. 2009;14:5027–41.View ArticlePubMedGoogle Scholar
  10. Sorokin DY, Gumerov VM, Rakitin AL, Beletsky AV, Damsté JSS, Muyzer G, et al. Genome analysis of Chitinivibrio alkaliphilus gen. nov., sp. nov., a novel extremely haloalkaliphilic anaerobic chitinolytic bacterium from the candidate phylum Termite Group 3. Environ Microbiol. 2014;16:1549–65.View ArticlePubMedGoogle Scholar
  11. Taranov E. GetIsolationSources. [https://github.com/allista/GetIsolationSources/releases]
  12. Kublanov IV, Bidjieva SK, Mardanov AV, Bonch-Osmolovskaya EA. Desulfurococcus kamchatkensis sp. nov., a novel hyperthermophilic protein-degrading archaeon isolated from a Kamchatka hot spring. Int J Syst Evol Microbiol. 2009;59(Pt 7):1743–7.View ArticlePubMedGoogle Scholar
  13. White paper on de novo assembly in CLC Assembly Cell 4.0. [http://www.clcbio.com/wp-content/uploads/2012/09/whitepaper-denovo-assembly-4.pdf]
  14. Boetzer M, Pirovano W. Toward almost closed genomes with GapFiller. Genome Biol. 2012;13:R56.PubMed CentralView ArticlePubMedGoogle Scholar
  15. Boetzer M, Henkel CV, Jansen HJ, Butler D, Pirovano W. Scaffolding pre-assembled contigs using SSPACE. Bioinformatics. 2011;27:578–9.View ArticlePubMedGoogle Scholar
  16. Prokaryotic Genomes Automatic Annotation Pipeline (PGAAP). [http://www.ncbi.nlm.nih.gov/genome/annotation_prok/]
  17. Borodovsky M, Lomsadze A. Gene identification in prokaryotic genomes, phages, metagenomes, and EST sequences with GeneMarkS suite. Curr Protoc Microbiol. 2014;32:Unit 1E.7.PubMedGoogle Scholar
  18. Schattner P, Brooks AN, Lowe TM. The tRNAscan-SE, snoscan and snoGPS web servers for the detection of tRNAs and snoRNAs. Nucleic Acids Res. 2005;33(Web Server issue):W686–9.PubMed CentralView ArticlePubMedGoogle Scholar
  19. Altschul SF, Madden TL, Schäffer AA, Zhang J, Zhang Z, Miller W, et al. Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Res. 1997;25:3389–402.PubMed CentralView ArticlePubMedGoogle Scholar
  20. Galperin MY, Makarova KS, Wolf YI, Koonin EV. Expanded microbial genome coverage and improved protein family annotation in the COG database. Nucleic Acids Res. 2015;43(Database issue):D261–9.PubMed CentralView ArticlePubMedGoogle Scholar
  21. Finn RD, Clements J, Eddy SR. HMMER web server: interactive sequence similarity searching. Nucleic Acids Res. 2011;39(Web Server issue):W29–37.PubMed CentralView ArticlePubMedGoogle Scholar
  22. Käll L, Krogh A, Sonnhammer E. A combined transmembrane topology and signal peptide prediction method. J Mol Biol. 2004;338:1027–36.View ArticlePubMedGoogle Scholar
  23. Bendtsen JD, Nielsen H, Widdick D, Palmer T, Brunak S. Prediction of twin-arginine signal peptides. BMC Bioinformatics. 2005;6:167.PubMed CentralView ArticlePubMedGoogle Scholar
  24. Bendtsen JD, Jensen LJ, Blom N, Von Heijne G, Brunak S. Feature-based prediction of non-classical and leaderless protein secretion. Protein Eng Des Sel. 2004;17:349–56.View ArticlePubMedGoogle Scholar
  25. Toshchakov SV, Kublanov IV, Messina E, Yakimov MM, Golyshin PN. Genomic analysis of pure cultures and communities. In: McGenity TJ, Timmis KN, Nogales Fernández B, editors. Hydrocarbon and Lipid Microbiology Protocols, Springer Protocols Handbooks. Heidelberg: Springer-Verlag; 2015. doi: 10.1007/8623_2015_12.
  26. Siguier P, Perochon J, Lestrade L, Mahillon J, Chandler M. ISfinder: the reference centre for bacterial insertion sequences. Nucleic Acids Res. 2006;34(Database issue):D32–6.PubMed CentralView ArticlePubMedGoogle Scholar
  27. Grissa I, Vergnaud G, Pourcel C. CRISPRFinder: a web tool to identify clustered regularly interspaced short palindromic repeats. Nucleic Acids Res. 2007;35(Web Server issue):W52–7.PubMed CentralView ArticlePubMedGoogle Scholar
  28. Rodriguez-R LM, Konstantinidis KT. Bypassing cultivation to identify bacterial species. Microbe. 2014;9:111–8.Google Scholar
  29. Konstantinidis KT, Ramette A, Tiedje JM. The bacterial species definition in the genomic era. Philos Trans R Soc Lond B Biol Sci. 2006;361:1929–40.PubMed CentralView ArticlePubMedGoogle Scholar
  30. Anderson I, Rodriguez J, Susanti D, Porat I, Reich C, Ulrich LE, et al. Genome sequence of Thermofilum pendens reveals an exceptional loss of biosynthetic pathways without genome reduction. J Bacteriol. 2008;190:2957–65.PubMed CentralView ArticlePubMedGoogle Scholar
  31. 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.PubMed CentralView ArticlePubMedGoogle Scholar
  32. 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.PubMed CentralView ArticlePubMedGoogle Scholar
  33. Garrity GM, Holt JG. The Road Map to the Manual. In: Garrity GM, Boone DR, Castenholz RW, editors. Bergey’s manual of systematic bacteriology, Second Edition, Volume 1. Springer: New York; 2001. p. 119–69.View ArticleGoogle Scholar
  34. Reysenbach AL. Class I. Thermoprotei class. nov. In: Garrity GM, Boone DR, Castenholz RW, editors. Bergey’s manual of systematic bacteriology, Second Edition, Volume 1. New York: Springer; 2001. p. 169.Google Scholar
  35. Zillig W, Stetter KO, Schafer W, Janekovic D, Wunderl S, Holz I, et al. Thermoproteales: a novel type of extremely thermoacidophilic anaerobic archaebacteria isolated from Icelandic solfataras. Zentralbl Mikrobiol Parasitenkd Infektionskr Hyg Abt 1 Orig. 1981;2:205–27.Google Scholar
  36. Euzéby JP, Tindall BJ. Nomenclatural type of orders: corrections necessary according to Rules 15 and 21a of the Bacteriological Code (1990 Revision), and designation of appropriate nomenclatural types of classes and subclasses. Request for an opinion. Int J Syst Evol Microbiol. 2001;51(Pt 2):725–7.View ArticlePubMedGoogle Scholar
  37. Judicial Commission Of The International Committee On Systematics Of Prokaryotes. The nomenclatural types of the orders Acholeplasmatales, Halanaerobiales, Halobacteriales, Methanobacteriales, Methanococcales, Methanomicrobiales, Planctomycetales, Prochlorales, Sulfolobales, Thermococcales, Thermoproteales and Verrucomicrobiales are the genera Acholeplasma, Halanaerobium, Halobacterium, Methanobacterium, Methanococcus, Methanomicrobium, Planctomyces, Prochloron, Sulfolobus, Thermococcus, Thermoproteus and Verrucomicrobium, respectively. Opinion 79. Int J Syst Evol Microbiol. 2005;55:517–8.View ArticleGoogle Scholar
  38. The Gene Ontology Consortium. Creating the gene ontology resource: design and implementation. Genome Res. 2001;11:1425–33.View ArticleGoogle Scholar
  39. Tamura K, Nei M. Estimation of the number of nucleotide substitutions in the control region of mitochondrial DNA in humans and chimpanzees. Mol Biol Evol. 1993;10:512–26.PubMedGoogle Scholar
  40. Tamura K, Stecher G, Peterson D, Filipski A, Kumar S. MEGA6: Molecular Evolutionary Genetics Analysis version 6.0. Mol Biol Evol. 2013;30:2725–9.PubMed CentralView ArticlePubMedGoogle Scholar
  41. Krzywinski M, Schein J, Birol I, Connors J, Gascoyne R, Horsman D, et al. Circos: an information aesthetic for comparative genomics. Genome Res. 2009;19:1639–45.PubMed CentralView ArticlePubMedGoogle Scholar

Copyright

© Toshchakov et al. 2015