# Copyright 2006-2016 by Peter Cock. All rights reserved. # Revisions copyright 2015 by Ben Woodcroft. All rights reserved. # # This file is part of the Biopython distribution and governed by your # choice of the "Biopython License Agreement" or the "BSD 3-Clause License". # Please see the LICENSE file that should have been included as part of this # package. """Bio.AlignIO support for "stockholm" format (used in the PFAM database). You are expected to use this module via the Bio.AlignIO functions (or the Bio.SeqIO functions if you want to work directly with the gapped sequences). For example, consider a Stockholm alignment file containing the following:: # STOCKHOLM 1.0 #=GC SS_cons .................<<<<<<<<...<<<<<<<........>>>>>>>.. AP001509.1 UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-GAUGAGGGU #=GR AP001509.1 SS -----------------<<<<<<<<---..<<-<<-------->>->>..-- AE007476.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-CACGA-CGU #=GR AE007476.1 SS -----------------<<<<<<<<-----<<.<<-------->>.>>---- #=GC SS_cons ......<<<<<<<.......>>>>>>>..>>>>>>>>............... AP001509.1 CUCUAC-AGGUA-CCGUAAA-UACCUAGCUACGAAAAGAAUGCAGUUAAUGU #=GR AP001509.1 SS -------<<<<<--------->>>>>--->>>>>>>>--------------- AE007476.1 UUCUACAAGGUG-CCGG-AA-CACCUAACAAUAAGUAAGUCAGCAGUGAGAU #=GR AE007476.1 SS ------.<<<<<--------->>>>>.-->>>>>>>>--------------- // This is a single multiple sequence alignment, so you would probably load this using the Bio.AlignIO.read() function: >>> from Bio import AlignIO >>> align = AlignIO.read("Stockholm/simple.sth", "stockholm") >>> print(align) SingleLetterAlphabet() alignment with 2 rows and 104 columns UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-G...UGU AP001509.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-C...GAU AE007476.1 >>> for record in align: ... print("%s %i" % (record.id, len(record))) AP001509.1 104 AE007476.1 104 This example file is clearly using RNA, so you might want the alignment object (and the SeqRecord objects it holds) to reflect this, rather than simple using the default single letter alphabet as shown above. You can do this with an optional argument to the Bio.AlignIO.read() function: >>> from Bio import AlignIO >>> from Bio.Alphabet import generic_rna >>> align = AlignIO.read("Stockholm/simple.sth", "stockholm", ... alphabet=generic_rna) >>> print(align) RNAAlphabet() alignment with 2 rows and 104 columns UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-G...UGU AP001509.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-C...GAU AE007476.1 In addition to the sequences themselves, this example alignment also includes some GR lines for the secondary structure of the sequences. These are strings, with one character for each letter in the associated sequence: >>> for record in align: ... print(record.id) ... print(record.seq) ... print(record.letter_annotations['secondary_structure']) AP001509.1 UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-GAUGAGGGUCUCUAC-AGGUA-CCGUAAA-UACCUAGCUACGAAAAGAAUGCAGUUAAUGU -----------------<<<<<<<<---..<<-<<-------->>->>..---------<<<<<--------->>>>>--->>>>>>>>--------------- AE007476.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-CACGA-CGUUUCUACAAGGUG-CCGG-AA-CACCUAACAAUAAGUAAGUCAGCAGUGAGAU -----------------<<<<<<<<-----<<.<<-------->>.>>----------.<<<<<--------->>>>>.-->>>>>>>>--------------- Any general annotation for each row is recorded in the SeqRecord's annotations dictionary. Any per-column annotation for the entire alignment in in the alignment's column annotations dictionary, such as the secondary structure consensus in this example: >>> sorted(align.column_annotations.keys()) ['secondary_structure'] >>> align.column_annotations["secondary_structure"] '.................<<<<<<<<...<<<<<<<........>>>>>>>........<<<<<<<.......>>>>>>>..>>>>>>>>...............' You can output this alignment in many different file formats using Bio.AlignIO.write(), or the MultipleSeqAlignment object's format method: >>> print(align.format("fasta")) >AP001509.1 UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-GAUGAGGGUCUCUAC-A GGUA-CCGUAAA-UACCUAGCUACGAAAAGAAUGCAGUUAAUGU >AE007476.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-CACGA-CGUUUCUACAA GGUG-CCGG-AA-CACCUAACAAUAAGUAAGUCAGCAGUGAGAU Most output formats won't be able to hold the annotation possible in a Stockholm file: >>> print(align.format("stockholm")) # STOCKHOLM 1.0 #=GF SQ 2 AP001509.1 UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-GAUGAGGGUCUCUAC-AGGUA-CCGUAAA-UACCUAGCUACGAAAAGAAUGCAGUUAAUGU #=GS AP001509.1 AC AP001509.1 #=GS AP001509.1 DE AP001509.1 #=GR AP001509.1 SS -----------------<<<<<<<<---..<<-<<-------->>->>..---------<<<<<--------->>>>>--->>>>>>>>--------------- AE007476.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-CACGA-CGUUUCUACAAGGUG-CCGG-AA-CACCUAACAAUAAGUAAGUCAGCAGUGAGAU #=GS AE007476.1 AC AE007476.1 #=GS AE007476.1 DE AE007476.1 #=GR AE007476.1 SS -----------------<<<<<<<<-----<<.<<-------->>.>>----------.<<<<<--------->>>>>.-->>>>>>>>--------------- #=GC SS_cons .................<<<<<<<<...<<<<<<<........>>>>>>>........<<<<<<<.......>>>>>>>..>>>>>>>>............... // Note that when writing Stockholm files, AlignIO does not break long sequences up and interleave them (as in the input file shown above). The standard allows this simpler layout, and it is more likely to be understood by other tools. Finally, as an aside, it can sometimes be useful to use Bio.SeqIO.parse() to iterate over the alignment rows as SeqRecord objects - rather than working with Alignnment objects. Again, if you want to you can specify this is RNA: >>> from Bio import SeqIO >>> from Bio.Alphabet import generic_rna >>> for record in SeqIO.parse("Stockholm/simple.sth", "stockholm", ... alphabet=generic_rna): ... print(record.id) ... print(record.seq) ... print(record.letter_annotations['secondary_structure']) AP001509.1 UUAAUCGAGCUCAACACUCUUCGUAUAUCCUC-UCAAUAUGG-GAUGAGGGUCUCUAC-AGGUA-CCGUAAA-UACCUAGCUACGAAAAGAAUGCAGUUAAUGU -----------------<<<<<<<<---..<<-<<-------->>->>..---------<<<<<--------->>>>>--->>>>>>>>--------------- AE007476.1 AAAAUUGAAUAUCGUUUUACUUGUUUAU-GUCGUGAAU-UGG-CACGA-CGUUUCUACAAGGUG-CCGG-AA-CACCUAACAAUAAGUAAGUCAGCAGUGAGAU -----------------<<<<<<<<-----<<.<<-------->>.>>----------.<<<<<--------->>>>>.-->>>>>>>>--------------- Remember that if you slice a SeqRecord, the per-letter-annotations like the secondary structure string here, are also sliced: >>> sub_record = record[10:20] >>> print(sub_record.seq) AUCGUUUUAC >>> print(sub_record.letter_annotations['secondary_structure']) -------<<< Likewise with the alignment object, as long as you are not dropping any rows, slicing specific columns of an alignment will slice any per-column-annotations: >>> align.column_annotations["secondary_structure"] '.................<<<<<<<<...<<<<<<<........>>>>>>>........<<<<<<<.......>>>>>>>..>>>>>>>>...............' >>> part_align = align[:,10:20] >>> part_align.column_annotations["secondary_structure"] '.......<<<' You can also see this in the Stockholm output of this partial-alignment: >>> print(part_align.format("stockholm")) # STOCKHOLM 1.0 #=GF SQ 2 AP001509.1 UCAACACUCU #=GS AP001509.1 AC AP001509.1 #=GS AP001509.1 DE AP001509.1 #=GR AP001509.1 SS -------<<< AE007476.1 AUCGUUUUAC #=GS AE007476.1 AC AE007476.1 #=GS AE007476.1 DE AE007476.1 #=GR AE007476.1 SS -------<<< #=GC SS_cons .......<<< // """ from __future__ import print_function from collections import OrderedDict from Bio.Seq import Seq from Bio.SeqRecord import SeqRecord from Bio.Align import MultipleSeqAlignment from .Interfaces import AlignmentIterator, SequentialAlignmentWriter class StockholmWriter(SequentialAlignmentWriter): """Stockholm/PFAM alignment writer.""" # These dictionaries should be kept in sync with those # defined in the StockholmIterator class. pfam_gr_mapping = { "secondary_structure": "SS", "surface_accessibility": "SA", "transmembrane": "TM", "posterior_probability": "PP", "ligand_binding": "LI", "active_site": "AS", "intron": "IN", } # These GC mappings are in addition to *_cons in GR mapping: pfam_gc_mapping = {"reference_annotation": "RF", "model_mask": "MM"} # Following dictionary deliberately does not cover AC, DE or DR pfam_gs_mapping = {"organism": "OS", "organism_classification": "OC", "look": "LO"} def write_alignment(self, alignment): """Use this to write (another) single alignment to an open file. Note that sequences and their annotation are recorded together (rather than having a block of annotation followed by a block of aligned sequences). """ count = len(alignment) self._length_of_sequences = alignment.get_alignment_length() self._ids_written = [] if count == 0: raise ValueError("Must have at least one sequence") if self._length_of_sequences == 0: raise ValueError("Non-empty sequences are required") self.handle.write("# STOCKHOLM 1.0\n") self.handle.write("#=GF SQ %i\n" % count) for record in alignment: self._write_record(record) # This shouldn't be None... but just in case, if alignment.column_annotations: for k, v in sorted(alignment.column_annotations.items()): if k in self.pfam_gc_mapping: self.handle.write("#=GC %s %s\n" % (self.pfam_gc_mapping[k], v)) elif k in self.pfam_gr_mapping: self.handle.write( "#=GC %s %s\n" % (self.pfam_gr_mapping[k] + "_cons", v) ) else: # It doesn't follow the PFAM standards, but should we record # this data anyway? pass self.handle.write("//\n") def _write_record(self, record): """Write a single SeqRecord to the file (PRIVATE).""" if self._length_of_sequences != len(record.seq): raise ValueError("Sequences must all be the same length") # For the case for stockholm to stockholm, try and use record.name seq_name = record.id if record.name is not None: if "accession" in record.annotations: if record.id == record.annotations["accession"]: seq_name = record.name # In the Stockholm file format, spaces are not allowed in the id seq_name = seq_name.replace(" ", "_") if "start" in record.annotations and "end" in record.annotations: suffix = "/%s-%s" % ( str(record.annotations["start"]), str(record.annotations["end"]), ) if seq_name[-len(suffix) :] != suffix: seq_name = "%s/%s-%s" % ( seq_name, str(record.annotations["start"]), str(record.annotations["end"]), ) if seq_name in self._ids_written: raise ValueError("Duplicate record identifier: %s" % seq_name) self._ids_written.append(seq_name) self.handle.write("%s %s\n" % (seq_name, str(record.seq))) # The recommended placement for GS lines (per sequence annotation) # is above the alignment (as a header block) or just below the # corresponding sequence. # # The recommended placement for GR lines (per sequence per column # annotation such as secondary structure) is just below the # corresponding sequence. # # We put both just below the corresponding sequence as this allows # us to write the file using a single pass through the records. # AC = Accession if "accession" in record.annotations: self.handle.write( "#=GS %s AC %s\n" % (seq_name, self.clean(record.annotations["accession"])) ) elif record.id: self.handle.write("#=GS %s AC %s\n" % (seq_name, self.clean(record.id))) # DE = description if record.description: self.handle.write( "#=GS %s DE %s\n" % (seq_name, self.clean(record.description)) ) # DE = database links for xref in record.dbxrefs: self.handle.write("#=GS %s DR %s\n" % (seq_name, self.clean(xref))) # GS = other per sequence annotation for key, value in record.annotations.items(): if key in self.pfam_gs_mapping: data = self.clean(str(value)) if data: self.handle.write( "#=GS %s %s %s\n" % (seq_name, self.clean(self.pfam_gs_mapping[key]), data) ) else: # It doesn't follow the PFAM standards, but should we record # this data anyway? pass # GR = per row per column sequence annotation for key, value in record.letter_annotations.items(): if key in self.pfam_gr_mapping and len(str(value)) == len(record.seq): data = self.clean(str(value)) if data: self.handle.write( "#=GR %s %s %s\n" % (seq_name, self.clean(self.pfam_gr_mapping[key]), data) ) else: # It doesn't follow the PFAM standards, but should we record # this data anyway? pass class StockholmIterator(AlignmentIterator): """Loads a Stockholm file from PFAM into MultipleSeqAlignment objects. The file may contain multiple concatenated alignments, which are loaded and returned incrementally. This parser will detect if the Stockholm file follows the PFAM conventions for sequence specific meta-data (lines starting #=GS and #=GR) and populates the SeqRecord fields accordingly. Any annotation which does not follow the PFAM conventions is currently ignored. If an accession is provided for an entry in the meta data, IT WILL NOT be used as the record.id (it will be recorded in the record's annotations). This is because some files have (sub) sequences from different parts of the same accession (differentiated by different start-end positions). Wrap-around alignments are not supported - each sequences must be on a single line. However, interlaced sequences should work. For more information on the file format, please see: http://sonnhammer.sbc.su.se/Stockholm.html https://en.wikipedia.org/wiki/Stockholm_format http://bioperl.org/formats/alignment_formats/Stockholm_multiple_alignment_format.html For consistency with BioPerl and EMBOSS we call this the "stockholm" format. """ # These dictionaries should be kept in sync with those # defined in the PfamStockholmWriter class. pfam_gr_mapping = { "SS": "secondary_structure", "SA": "surface_accessibility", "TM": "transmembrane", "PP": "posterior_probability", "LI": "ligand_binding", "AS": "active_site", "IN": "intron", } # These GC mappings are in addition to *_cons in GR mapping: pfam_gc_mapping = {"RF": "reference_annotation", "MM": "model_mask"} # Following dictionary deliberately does not cover AC, DE or DR pfam_gs_mapping = {"OS": "organism", "OC": "organism_classification", "LO": "look"} _header = None # for caching lines between __next__ calls def __next__(self): """Parse the next alignment from the handle.""" handle = self.handle if self._header is None: line = handle.readline() else: # Header we saved from when we were parsing # the previous alignment. line = self._header self._header = None if not line: # Empty file - just give up. raise StopIteration if line.strip() != "# STOCKHOLM 1.0": raise ValueError("Did not find STOCKHOLM header") # Note: If this file follows the PFAM conventions, there should be # a line containing the number of sequences, e.g. "#=GF SQ 67" # We do not check for this - perhaps we should, and verify that # if present it agrees with our parsing. seqs = {} ids = OrderedDict() # Really only need an OrderedSet, but python lacks this gs = {} gr = {} gf = {} gc = {} passed_end_alignment = False while True: line = handle.readline() if not line: break # end of file line = line.strip() # remove trailing \n if line == "# STOCKHOLM 1.0": self._header = line break elif line == "//": # The "//" line indicates the end of the alignment. # There may still be more meta-data passed_end_alignment = True elif line == "": # blank line, ignore pass elif line[0] != "#": # Sequence # Format: " " assert not passed_end_alignment parts = [x.strip() for x in line.split(" ", 1)] if len(parts) != 2: # This might be someone attempting to store a zero length sequence? raise ValueError( "Could not split line into identifier and sequence:\n" + line ) seq_id, seq = parts if seq_id not in ids: ids[seq_id] = True seqs.setdefault(seq_id, "") seqs[seq_id] += seq.replace(".", "-") elif len(line) >= 5: # Comment line or meta-data if line[:5] == "#=GF ": # Generic per-File annotation, free text # Format: #=GF feature, text = line[5:].strip().split(None, 1) # Each feature key could be used more than once, # so store the entries as a list of strings. if feature not in gf: gf[feature] = [text] else: gf[feature].append(text) elif line[:5] == "#=GC ": # Generic per-Column annotation, exactly 1 char per column # Format: "#=GC " feature, text = line[5:].strip().split(None, 2) if feature not in gc: gc[feature] = "" gc[feature] += text.strip() # append to any previous entry # Might be interleaved blocks, so can't check length yet elif line[:5] == "#=GS ": # Generic per-Sequence annotation, free text # Format: "#=GS " seq_id, feature, text = line[5:].strip().split(None, 2) # if seq_id not in ids: # ids.append(seq_id) if seq_id not in gs: gs[seq_id] = {} if feature not in gs[seq_id]: gs[seq_id][feature] = [text] else: gs[seq_id][feature].append(text) elif line[:5] == "#=GR ": # Generic per-Sequence AND per-Column markup # Format: "#=GR " seq_id, feature, text = line[5:].strip().split(None, 2) # if seq_id not in ids: # ids.append(seq_id) if seq_id not in gr: gr[seq_id] = {} if feature not in gr[seq_id]: gr[seq_id][feature] = "" gr[seq_id][feature] += text.strip() # append to any previous entry # Might be interleaved blocks, so can't check length yet # Next line... assert len(seqs) <= len(ids) # assert len(gs) <= len(ids) # assert len(gr) <= len(ids) self.ids = ids.keys() self.sequences = seqs self.seq_annotation = gs self.seq_col_annotation = gr if ids and seqs: if ( self.records_per_alignment is not None and self.records_per_alignment != len(ids) ): raise ValueError( "Found %i records in this alignment, told to expect %i" % (len(ids), self.records_per_alignment) ) alignment_length = len(list(seqs.values())[0]) records = [] # Alignment obj will put them all in a list anyway for seq_id in ids: seq = seqs[seq_id] if alignment_length != len(seq): raise ValueError( "Sequences have different lengths, or repeated identifier" ) name, start, end = self._identifier_split(seq_id) record = SeqRecord( Seq(seq, self.alphabet), id=seq_id, name=name, description=seq_id, annotations={"accession": name}, ) # Accession will be overridden by _populate_meta_data if an explicit # accession is provided: record.annotations["accession"] = name if start is not None: record.annotations["start"] = start if end is not None: record.annotations["end"] = end self._populate_meta_data(seq_id, record) records.append(record) for k, v in gc.items(): if len(v) != alignment_length: raise ValueError( "%s length %i, expected %i" % (k, len(v), alignment_length) ) alignment = MultipleSeqAlignment(records, self.alphabet) for k, v in sorted(gc.items()): if k in self.pfam_gc_mapping: alignment.column_annotations[self.pfam_gc_mapping[k]] = v elif k.endswith("_cons") and k[:-5] in self.pfam_gr_mapping: alignment.column_annotations[self.pfam_gr_mapping[k[:-5]]] = v else: # Ignore it? alignment.column_annotations["GC:" + k] = v # TODO - Introduce an annotated alignment class? # For now, store the annotation a new private property: alignment._annotations = gr return alignment else: raise StopIteration def _identifier_split(self, identifier): """Return (name, start, end) string tuple from an identier (PRIVATE).""" if "/" in identifier: name, start_end = identifier.rsplit("/", 1) if start_end.count("-") == 1: try: start, end = start_end.split("-") return name, int(start), int(end) except ValueError: # Non-integers after final '/' - fall through pass return identifier, None, None def _get_meta_data(self, identifier, meta_dict): """Take an itentifier and returns dict of all meta-data matching it (PRIVATE). For example, given "Q9PN73_CAMJE/149-220" will return all matches to this or "Q9PN73_CAMJE" which the identifier without its /start-end suffix. In the example below, the suffix is required to match the AC, but must be removed to match the OS and OC meta-data:: # STOCKHOLM 1.0 #=GS Q9PN73_CAMJE/149-220 AC Q9PN73 ... Q9PN73_CAMJE/149-220 NKA... ... #=GS Q9PN73_CAMJE OS Campylobacter jejuni #=GS Q9PN73_CAMJE OC Bacteria This function will return an empty dictionary if no data is found. """ name, start, end = self._identifier_split(identifier) if name == identifier: identifier_keys = [identifier] else: identifier_keys = [identifier, name] answer = {} for identifier_key in identifier_keys: try: for feature_key in meta_dict[identifier_key]: answer[feature_key] = meta_dict[identifier_key][feature_key] except KeyError: pass return answer def _populate_meta_data(self, identifier, record): """Add meta-date to a SecRecord's annotations dictionary (PRIVATE). This function applies the PFAM conventions. """ seq_data = self._get_meta_data(identifier, self.seq_annotation) for feature in seq_data: # Note this dictionary contains lists! if feature == "AC": # ACcession number assert len(seq_data[feature]) == 1 record.annotations["accession"] = seq_data[feature][0] elif feature == "DE": # DEscription record.description = "\n".join(seq_data[feature]) elif feature == "DR": # Database Reference # Should we try and parse the strings? record.dbxrefs = seq_data[feature] elif feature in self.pfam_gs_mapping: record.annotations[self.pfam_gs_mapping[feature]] = ", ".join( seq_data[feature] ) else: # Ignore it? record.annotations["GS:" + feature] = ", ".join(seq_data[feature]) # Now record the per-letter-annotations seq_col_data = self._get_meta_data(identifier, self.seq_col_annotation) for feature in seq_col_data: # Note this dictionary contains strings! if feature in self.pfam_gr_mapping: record.letter_annotations[self.pfam_gr_mapping[feature]] = seq_col_data[ feature ] else: # Ignore it? record.letter_annotations["GR:" + feature] = seq_col_data[feature] if __name__ == "__main__": from Bio._utils import run_doctest run_doctest()