passages.id: split_4_test_2908_passage
passages.type: progene_text
passages.text: Rates of beta-galactosidase synthesis during growth in different media revealed that nirB , - D , - E and - C are transcribed from the FNR - dependent promoter , p - nirB , located just upstream of the nirB gene : expression is co - ordinately repressed by oxygen and induced during anaerobic growth .