New source: SILVA taxonomy

src/pyobo/sources/silva.py

@@ -0,0 +1,167 @@
+"""Convert SILVA small subunit (ssu) taxonomy to OBO format."""
+
+import logging
+from collections.abc import Iterable
+
+import pandas as pd
+from tqdm.auto import tqdm
+
+from pyobo.struct import Obo, Reference, Term
+from pyobo.struct.typedef import has_taxonomy_rank
+from pyobo.utils.path import ensure_path
+
+__all__ = [
+    "SILVAGetter",
+]
+
+PREFIX = "silva.taxon"
+
+#: A mapping from SILVA rank names to TAXRANK references
+SILVA_RANK_TO_TAXRANK = {
+    "domain": Reference(prefix="TAXRANK", identifier="0000037", name="domain"),
+    "major_clade": Reference(prefix="TAXRANK", identifier="0001004", name="major_clade"),
+    "superkingdom": Reference(prefix="TAXRANK", identifier="0000022", name="superkingdom"),
+    "kingdom": Reference(prefix="TAXRANK", identifier="0000017", name="kingdom"),
+    "subkingdom": Reference(prefix="TAXRANK", identifier="0000029", name="subkingdom"),
+    "superphylum": Reference(prefix="TAXRANK", identifier="0000027", name="superphylum"),
+    "phylum": Reference(prefix="TAXRANK", identifier="0000001", name="phylum"),
+    "subphylum": Reference(prefix="TAXRANK", identifier="0000008", name="subphylum"),
+    "infraphylum": Reference(prefix="TAXRANK", identifier="0000040", name="infraphylum"),
+    "superclass": Reference(prefix="TAXRANK", identifier="0000015", name="superclass"),
+    "class": Reference(prefix="TAXRANK", identifier="0000002", name="class"),
+    "subclass": Reference(prefix="TAXRANK", identifier="0000007", name="subclass"),
+    "infraclass": Reference(prefix="TAXRANK", identifier="0000019", name="infraclass"),
+    "superorder": Reference(prefix="TAXRANK", identifier="0000020", name="superorder"),
+    "order": Reference(prefix="TAXRANK", identifier="0000003", name="order"),
+    "suborder": Reference(prefix="TAXRANK", identifier="0000014", name="suborder"),
+    "superfamily": Reference(prefix="TAXRANK", identifier="0000018", name="superfamily"),
+    "family": Reference(prefix="TAXRANK", identifier="0000004", name="family"),
+    "subfamily": Reference(prefix="TAXRANK", identifier="0000024", name="subfamily"),
+    "genus": Reference(prefix="TAXRANK", identifier="0000005", name="genus"),
+}
+
+#: URLs for the SILVA files.
+SILVA_TAXONOMY_URL = "https://www.arb-silva.de/fileadmin/silva_databases/current/Exports/taxonomy/tax_slv_ssu_138.2.txt.gz"
+SILVA_TAXMAP_URL = "https://www.arb-silva.de/fileadmin/silva_databases/current/Exports/taxonomy/taxmap_slv_ssu_ref_nr_138.2.txt.gz"
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.WARNING)
+
+
+class SILVAGetter(Obo):
+    """An ontology representation of the SILVA taxonomy."""
+
+    ontology = bioversions_key = PREFIX
+    typedefs = [has_taxonomy_rank]
+    idspaces = {
+        PREFIX: "https://www.arb-silva.de/no_cache/download/archive/current/Exports/taxonomy/",
+        "ena.embl": "https://www.ebi.ac.uk/ena/browser/view/",
+    }
+    root_terms = [
+        Reference(prefix=PREFIX, identifier="2", name="Archaea"),
+        Reference(prefix=PREFIX, identifier="3", name="Bacteria"),
+        Reference(prefix=PREFIX, identifier="4", name="Eukaryota"),
+    ]
+
+    def iter_terms(self, force: bool = False) -> Iterable[Term]:
+        """Iterate over terms in the SILVA ontology."""
+        return iter_terms_silva(version=self._version_or_raise, force=force)
+
+
+def iter_terms_silva(version: str, force: bool = False) -> Iterable[Term]:
+    """Iterate over SILVA terms from the main taxonomy and taxmap files."""
+    # --- Process the main taxonomy file ---
+    taxonomy_path = ensure_path(PREFIX, url=SILVA_TAXONOMY_URL, version=version, force=force)
+    tax_df = pd.read_csv(
+        taxonomy_path,
+        sep="\t",
+        header=None,
+        names=["taxonomy", "taxon_id", "rank", "ignore", "introduced"],
+        dtype=str,
+    )
+    tax_df.fillna("", inplace=True)
+
+    #: a dictionary that maps the joined taxonomy path (with trailing ";") to taxon_id
+    tax_path_to_id: dict[str, str] = {}
+    #: maps taxon_id to the Term object
+    terms_by_id = {}
+
+    for idx, row in tqdm(
+        tax_df.iterrows(),
+        total=len(tax_df),
+        desc=f"[{PREFIX}] processing main taxonomy",
+        unit="row",
+    ):
+        tax_str = row["taxonomy"].strip()
+        taxon_id = row["taxon_id"].strip()
+        rank_raw = row["rank"].strip()
+        rank = rank_raw.lower()
+        # Split taxonomy string by ";" and discard empty parts.
+        parts = [p.strip() for p in tax_str.split(";") if p.strip()]
+        if not parts:
+            logger.warning(f"Row {idx}: empty taxonomy string: {tax_str}")
+            continue
+
+        # The term's name is the last element (e.g. for "Bacteria;Actinomycetota;", name is "Actinomycetota").
+        name = parts[-1]
+        term = Term(reference=Reference(prefix=PREFIX, identifier=taxon_id, name=name))
+        if rank in SILVA_RANK_TO_TAXRANK:
+            term.annotate_object(has_taxonomy_rank, SILVA_RANK_TO_TAXRANK[rank])
+        else:
+            logger.warning(
+                f"Row {idx}: unknown rank '{rank_raw}' for taxonomy: {tax_str} (taxon id: {taxon_id})"
+            )
+
+        # Determine the parent by joining all but the last element.
+        if len(parts) > 1:
+            parent_key = ";".join(parts[:-1]) + ";"  # e.g. "Bacteria;"
+            parent_id = tax_path_to_id.get(parent_key)
+            if parent_id:
+                term.append_parent(Reference(prefix=PREFIX, identifier=parent_id))
+        full_key = ";".join(parts) + ";"
+        tax_path_to_id[full_key] = taxon_id
+        terms_by_id[taxon_id] = term
+
+    # --- Process the taxmap file ---
+    # This file has a header with columns: primaryAccession, start, stop, path, organism_name, taxid
+    taxmap_path = ensure_path(PREFIX, url=SILVA_TAXMAP_URL, version=version, force=force)
+    taxmap_df = pd.read_csv(taxmap_path, sep="\t", dtype=str)
+    taxmap_df.rename(
+        columns={
+            "primaryAccession": "accession",
+            "organism_name": "organism",
+            "taxid": "species_taxon_id",
+            "path": "taxonomy",
+        },
+        inplace=True,
+    )
+    taxmap_df.fillna("", inplace=True)
+
+    for idx, row in tqdm(
+        taxmap_df.iterrows(), total=len(taxmap_df), desc=f"[{PREFIX}] processing taxmap", unit="row"
+    ):
+        accession = row["accession"].strip()
+        species_taxon_id = row["species_taxon_id"].strip()
+        organism = row["organism"].strip()
+        if not accession or not species_taxon_id:
+            continue
+        if species_taxon_id in terms_by_id:
+            # Create a new term for the ENA accession.
+            new_term = Term(
+                reference=Reference(prefix="ena.embl", identifier=accession, name=organism)
+            )
+            # Do NOT annotate the new term with a rank (leave it unranked).
+            new_term.append_parent(Reference(prefix=PREFIX, identifier=species_taxon_id))
+            yield new_term
+        else:
+            logger.warning(
+                f"Row {idx} in taxmap: species_taxon_id {species_taxon_id} not found in main taxonomy"
+            )
+
+    # Yield all terms from the main taxonomy.
+    for term in terms_by_id.values():
+        yield term
+
+
+if __name__ == "__main__":
+    SILVAGetter().cli()