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Inducer expulsion is not a determinant of diauxic growth in Streptococcus bovis
D B Kearns1, G M Cook, J B Russell
1Section of Microbiology, Cornell University, Ithaca, NY 14853, USA.
Abstract:
When Streptococcus bovis JB1 was repeatedly transferred in a medium that contained the non-metabolizable glucose analog, 2-deoxyglucose, it lost its phosphotransferase system (PTS) for glucose but was still able to take up glucose via a facilitated diffusion mechanism. The wild type (JB1) had an inducible enzyme II lactose, but the mutant (JB1(2DG)) had a constitutive lactose PTS. JB1(2DG) was no longer able to exclude lactose when it was provided with glucose, but it retained its ability to expel a non-metabolizable lactose analog. Because JB1(2DG) could utilize glucose and lactose simultaneously and grow in a non-diauxic fashion, it appeared that inducer expulsion was not an important catabolite regulatory mechanism. Based on these results, inducer expulsion may be an artifact of non-metabolizable sugars.