1816
Previous genetic studies led to the conclusion that nitrate and nitrite induction of nasF operon expression is determined by a transcriptional antitermination mechanism .
 GENE: nasF operon
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: nasF operon