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Release information: SILVA 119

Release information of the SILVA SSU and LSU databases 119 as of July 24, 2014

SSU 119 LSU 119
Parc

4,346,367

(+ 537,483)

446,998

(+ 85,124)

Ref 1,583,868

(+ 147,454)

57,546

(+ 18,134)

Ref NR 99
534,968 (+55,242) since release 115, only SSU Ref NR 99 contains a guide tree

Former statistics:

Opens internal link in current windowSILVA 95, Silva 96, SILVA 98, SILVA 100, SILVA 102

SILVA 104, Opens internal link in current windowSILVA 106, Opens internal link in current windowSILVA 108, Opens internal link in current windowSILVA 111, Opens internal link in current windowSILVA 115

Small Subunit rRNA Database

SSU Parc (Web database only) contains all aligned sequences with an alignment identity value equal and above 50, an alignment quality value equal and above 40 as well as an basepair score or sequence quality equal and above 30. All sequences with a Pintail value < 50 or an alignment quality value < 75 have been assigned to color group 1 in ARB (red). All Living Tree Project or StrainInfo typestrains have been assigned to color group 2 in ARB (light blue). No further sequence curation has been applied.

To create SSU Ref (ARB file), all sequences below 1,200 bases for Bacteria and Eukarya and below 900 bases for Archaea or an alignment identity below 70 or an alignment quality value below 50 have been removed from SSU Parc. All sequences with a Pintail value < 50 or an alignment quality value < 75 have been assigned to color group 1 in ARB (red). All Living Tree Project or StrainInfo typestrains have been assigned to color group 2 in ARB (light blue).

To create SSU Ref NR 99 (Web database & ARB file), a 99% identity criterion to remove highly identical sequences using the UCLUST tool was applied. Sequences from cultivated species have been preserved in all cases. A guide tree was calculated by adding all sequences to the SSU Ref tree of SILVA release 115. For tree calculation, highly variable positions were removed for Bacteria, Archaea, and Eukarya with the respective position variability filters. Position variability filters for Bacteria, Archaea and Eukarya have been calculated and added to the dataset. Detailed information about the SSU Ref NR dataset is available Opens internal link in current windowhere.

All: Before using the alignment for extensive phylogenetic reconstructions all sequences should be checked carefully.

Large Subunit rRNA Databases

LSU Parc (Web database & ARB file) contains all aligned sequences with an alignment identity value equal and above 40 and an alignment quality value, a basepair score or a sequence quality equal and above 30. All sequences with an alignment quality value < 75 have been assigned to color group 1 in ARB (red). All Living Tree Project or StrainInfo typestrains have been assigned to color group 2 in ARB (light blue). No further curation has been applied. 

Additionally, for LSU Ref (Web database & ARB file) all sequences below 1,900 bases or an alignment identity below 60 have been removed, a guide tree was calculated based on the LSU Ref tree of SILVA release 115, and basic filters have been added.

Please take into account that the LSU SEED consists only of around 2,800 sequences and there is no guaranty that well aligned close relatives have always been available. We would recommend additional manual curation before using it for extensive phylogenetic reconstructions.

Taxonomies, Names, Type Strain & Genome Information

Taxonomy

With SILVA release 102 the default taxonomy shown on the webpage (browser/search) is the SILVA taxonomy. Briefly, the tree for Bacteria and Archaea has been organized based on the Bergey's taxonomic outline, LPSN and the literature. Starting with SILVA release 111 extensive care has been taken to also improve the Opens internal link in current windoweukaryotic taxonomy. The SILVA taxonomy is only available for the sequences that are part of the Ref(erence) datasets (SSU Ref & LSU Ref). To show the classification of all sequences (Parc) in the SILVA databases you have to switch to EMBL taxonomy.  

Alternative Taxonomies

Besides the SILVA and EMBL taxonomy, alternative classifications taken from the greengenes, RDP II and Opens internal link in current windowLTP projects are also available in SILVA. On the webpage, the user can switch using the taxonomy menu. In ARB, the different taxonomies can be found in the fields: tax_slv, tax_embl, tax_gg, tax_rdp and tax_ltp for SILVA, EMBL, greengenes, RDP II and LTP, respectively. The corresponding *_name fields shows the respective sequence name for each entry.  Please take into account that greengenes, RDP II and LTP provide only a subset of the sequences hosted by SILVA. If no taxonomic mapping to greengenes, RDP II or LTP was available they are assigned as "unclassified" and the respective sequence name equals EMBL. For the LSU datasets only SILVA, LTP and EMBL taxonomies are available.

Altenative Names

All names of validly described species in the SSU and LSU databases have been checked for changes (basonyms, synonyms and orthographical corrections) against the DSMZ "Nomenclature up to date" catalogue as of April 2014.

Cultured and Type strains

The information if a sequence originates from a cultured or type strain has been added to the field strain and is indicated by [T] and [C]. Several sources have been used to compile the information: The Opens external link in new windowStrainInfo.net bioportal (April 2014), The Ribosomal Database Project II (April 2014) and the Living Tree Project (release 115) which provides manually curated information compliant with Euzebys "Opens external link in new windowList of Prokaryotic names with Standing in Nomenclature".

Genomes

The information if a sequence originates from a genome project has been taken from Opens external link in new windowEMBL and added to the field strain. It is indicated by e[G].

Detailed information about the corresponding identifiers and target databases can be found in the table to the right.

The identifiers can be used for data retrieval by searching in the strain field see Opens internal link in current windowFAQ.

Quality Values

The length and colours of the bars give a first indication on the sequence and alignment quality as well as the risk for sequence anomalies based on Pintail analysis. After downloading the sequences as an ARB file, sequences that need attention can be selected by searching for low quality (alignment, sequence) or Pintail values in the corresponding ARB database fields. A full description of the colour code and all database fields available in the ARB files can be found in the Opens internal link in current windowFAQ section. Taking into account the rich set of sequence associated information that comes along with every SILVA sequence, user designed sub-databases can be easily generated.

SEEDs

All rRNA sequences have been aligned based on a completely manually re-checked SEED alignment of 71,193 rRNA sequences for SSU and 2,868 rRNA sequences for LSU. The SSU alignment is based on the official ssu_jan04 release of the ARB Project. The SSU SEED alignment has been considerably improved for Archaea by manual addition of more than 1,000 sequences as well as Fungi (10,000 sequences). All SSU Eukaryotic sequences (18S) have been cross-checked by Wolfgang Ludwig before their addition to the SEED. Most of the bacterial sequences have also undergone a curation process carried out by the SILVA Team. We would rate our SSU SEED alignment for all Bacteria and Archaea as good and for Eukarya as reasonable.

The LSU alignment was provided by Wolfgang Ludwig and has not been released before SILVA. It was cross-checked by the SILVA Team before using it as the SEED for automatic alignment.  Bacteria and Archaea could be rated as good. The Eukaryotes need definitely further attention.

Statistics

Sequence Retrieval and Processing

SSU 119 LSU 119
candidates (total) 6,018,530 708,572
RNAmmer66,87132,778
< 300 bases 1,237,546 198,868
> 2% ambiguities 23,398 6867
> 2% homopolymers 78,324 15,314
> 2% vector contamination 2719 636
low alignment identity 391,168 61,830

total rejected by QC

1,672,163

261,574

Sequences have been retrieved from EMBL Opens external link in new windowRelease 119 (March 14) using a complex keyword search procedure and sequence based search with Opens external link in new windowRNAmmer profiles. Cross checks with RDP II indicated no loss of primary data. Most of the sequences rejected by a low identity value after alignment with SINA were classified as not ribosomal RNA sequences by manual inspection.

1. Growth of the ribosomal RNA databases since 1992

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Blue: RDP II, orange: SILVA SSUParc based on EMBL releases

2. Length Distribution (SSU & LSU)

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Blue: raw data, red: the quality checked & aligned SSUParc sequences

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Blue: raw data, red: the quality checked & aligned LSUParc sequences

Basic statistics for the SILVA databases

    SSURef   SSURef NR   LSUParc   LSURef  
Version   119   119   119   119  
Total   1,583,868   534,968   446,998   57,637  
Bacteria   1,454,141   464,618   66,328   43,822  
Archaea   48,002   18,797   736   629  
Eukaryota   81,725   51,533   379,126   13,186  
Cultured   36,585   36,472   24,157   8106  
Typestrains   21,334   21,221   5842   4694  
                   

Strain Identifiers

Source Information Tag Datasets
EMBL Typestrains (t) SSU, LSU
EMBL Genomes e[G]  SSU, LSU
Straininfo.net Cultured s[C] SSU, LSU
Straininfo.net Typestrains s[T] SSU, LSU
Living Tree Project  Typestrains (curated)  l[T] SSU
RDP II Typestrains r[T] SSU

RNAmmer

RNAmmer is a computational predictor for the major rRNA species (SSU, LSU) from all three domains of life. The program uses hidden Markov models trained on data from the European ribosomal RNA database project. SILVA runs the profiles of RNAmmer on all sequence entries of the EMBL archive to complement the existing predictions. All predictions are marked with RNAmmer in the ann_src_field. More information about RNAmmer can be found in the Opens external link in new windowpaper.

New in Release 119

Known Bugs

  • SSUParc: 40,000 sequences have no Pintail values
  • Website/SINA classifier: Only SILVA taxonomy is currently available

Citations

Quast C, Pruesse E, Yilmaz P, Gerken J, Schweer T, Yarza P, Peplies J, Glöckner FO (2013) The SILVA ribosomal RNA gene database project: improved data processing and web-based tools. Opens external link in new windowNucl. Acids Res. 41 (D1): D590-D596.

Yilmaz P, Parfrey LW, Yarza P, Gerken J, Pruesse E, Quast C, Schweer T, Peplies J, Ludwig W, Glöckner FO (2014) The SILVA and "All-species Living Tree Project (LTP)" taxonomic frameworks. Opens external link in new windowNucl. Acids Res. 42:D643-D648

If you use SINA please cite:

Pruesse, E, Peplies, J and Glöckner, FO (2012) SINA: accurate high-throughput multiple sequence alignment of ribosomal RNA genes. Opens external link in new windowBioinformatics, 28, 1823-1829