tokens: Pulse-field gel electrophoresis ( PFGE ) analysis showed that these genes are physically located within a DNA fragment of 250 kb .
folded_tokens: pulse-field gel electrophoresis ( pfge ) analysis showed that these genes are physically located within a dna fragment of 250 kb .
labels: B-other_name I-other_name I-other_name I-other_name I-other_name I-other_name I-other_name O O O O O O O O O B-DNA_molecule I-DNA_molecule O B-DNA_domain_or_region I-DNA_domain_or_region O