Growth phase-associated changes in Lactobacillus rhamnosus GG

Transcriptional profiling of probiotic Lactobacillus rhamnosus GG during growth in industrial-type whey medium in pH-controlled bioreactor cultures at two different growth pH: 4.8 and 5.8. Keywords: growth phase, growth pH Cell samples from three biological replicates were harvested at mid-exponential (4 h), late exponential (12 h), stationary transition point (16 h), early stationary (20 h) and late stationary (31 h) phases, all these samples both from pH 4.8 and 5.8 cultivations. A total of 66 hybridizations were performed according to ANOVA design where all possible direct pair-wise comparisons within biological replicates were conducted. Growth series between treatments (pH 4.8 or pH 5.8) were combined together by hybridizing RNA samples from the treatments at time points 12 h and 31 h to microarrays using dye-swap replicates. Treatments were paired twice and each biological replicate was used only once to form the pairs. Other comparisons between the two pH treatments were estimated computationally.