def parse_contaminants(file):
    """
    Parse contamination file.
    example:
    ==============================
    Pirisoci	Alveolata	Higher Taxonomy
    DiplDSTH	GoniavonGEN	Unique ID
    Fucucera	Ochrophyta	Lower Taxonomy
    ==============================
    input: tab separated file with contaminants
    result: dictionary with organism as key and tuple with taxonomy
            and rank 
    """
    cont_dict = {}
    for line in open(file):
        org, tax, rank = line.split('\t')
        cont_dict[org] = (tax, rank.strip())
    return cont_dict