Global control of carbon flux in Bifidobacterium breve UCC2003

In this paper, two predicted lac I type transcription factors (TFs) were characterised and shown to be involved in the regulation of the central metabolic pathways of B. breve UCC2003. Although, genetically different, these TF were functionally very similar. When first identified these TFs were named AraQ and MalR1, due to their predicted associations with arabinose and maltose metabolism, respectively. Now, however they have been renamed as BifR1 and BifR2 respectively, due to their control of the central metabolic pathways including the bifid shunt. DNA-microarrays containing oligonucleotide primers representing each of the 1864 annotated genes on the genome of B. breve UCC2003 (O'Connell Motherway et al., 2011) were designed by and obtained from Agilent Technologies (Palo Alto, Ca., USA). Methods for cell disruption, RNA isolation, RNA quality control, complementary DNA synthesis and labeling were performed as described previously (Pokusaeva et al., 2009). Labeled cDNA was hybridized using the Agilent Gene Expression hybridization kit (part number 5188-5242) as described in the Agilent Two-Color Microarray-Based Gene Expression Analysis v4.0 manual (G4140-90050). Following hybridization, microarrays were washed in accordance with Agilent’s standard procedures and scanned using an Agilent DNA microarray scanner (model G2565A). Generated scans were converted to data files with Agilent's Feature Extraction software (Version 9.5). DNA-microarray data were processed as previously described (Garcia De La Nava et al., 2003). Differential expression tests were performed with the Cyber-T implementation of a variant of the t-test (Long et al., 2001). A gene was considered differentially expressed when p < 0.001 and an expression ratio of >3 or <0.33 relative to the control.