This package provides tools for reading and writing biological sequences in multiple formats, including FASTA', PHYLIP', CLUSTAL', STOCKHOLM', MEGA and GenBank'. Supports interleaved and sequential layouts where applicable, and reads or writes gzip, bzip2 and xz compressed files transparently. Converts between formats, renames sequences via a two-column mapping, summarizes sequence counts, lengths, GC content and ambiguous characters, and manipulates sequence sets (e.g., filtering by patterns and computing consensus sequences from alignments). Also includes functions to download nucleotide records from NCBI by accession.