5677
By subjecting a large random transposon mutant library to growth under iron - limiting conditions , mutants of the MCR _ 0996 - rhlB - yggW operon , rnd , and MCR _ 0457 were negatively selected .
 Chemical: iron
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: iron