Dynamics of the XXXX transcriptome in response to media composition, salivary a-amylase and starch.

@entity844 @entity7969 @entity9190 @entity3793 @entity3158 @entity18440 @entity413
UNASSIGNED: @entity9190 , as a primary colonizer of the tooth surface, interacts with salivary a-amylase via amylase-binding protein A (AbpA). This enzyme hydrolyzes starch to @entity413 , @entity7969 , and maltodextrins that can be utilized by various oral bacteria for nutrition. Microarray studies demonstrated that AbpA modulates gene expression in response to amylase, suggesting that the amylase-streptococcal interaction may function in ways other than nutrition. The goal of this study was to explore the role of AbpA in gene regulation through comparative transcriptional profiling of wild-type KS1 and AbpA(-) mutant KS1  abpA under various environmental conditions. A portion of total RNA isolated from mid-log phase cells grown in 5% @entity3158 in (1) complex medium with/without amylase, (2) defined medium (DM) containing 0.8% @entity413 with/without amylase, and (3) DM containing 0.2% @entity413 and amylase with/without starch was reverse transcribed to cDNA and the rest used for RNA-Sequencing. Changes in expression of selected genes were validated by qRT-PCR. Maltodextrin-associated genes, @entity844 synthesis genes and competence genes were differentially expressed in a medium-dependent manner. Genes in another cluster containing a putative @entity3793 kinase/response regulator, peptide @entity18440 reductase, thioredoxin protein, lipoprotein, and cytochrome c-type protein were downregulated in KS1  abpA under all environmental conditions tested. Thus, AbpA appears to modulate genes associated with maltodextrin utilization/transport and @entity844 synthesis. Importantly, in all growth conditions AbpA is associated with increased expression of a potential two component signaling system associated with genes involved in reducing oxidative stress suggesting a role in signal transduction and stress tolerance.
