Abstract
Catabolic control protein (CcpA) is linked to complex carbohydrate utilization and virulence factor in many bacteria species, influences the transcription of target genes by many mechanisms. To characterize the activity and regulatory mechanisms of CcpA in Streptococcus sanguinis, here, we analyzed the transcriptome of Streptococcus sanguinis SK36 and its CcpA-null derivative (ΔCcpA) using RNA-seq. Compared to the regulon of CcpA in SK36 in the RegPrecise database, we found that only minority of differentially expressed genes (DEGs) contained putative catabolite response element (cre) in their regulatory regions, indicating that many genes could have been affected indirectly by the loss of CcpA and analyzing the sequence of the promoter region using prediction tools is not a desirable method to recognize potential target genes of global regulator CcpA. Gene ontology and pathway analysis of DEGs revealed that CcpA exerts an influence predominantly involved in carbon catabolite metabolism and some amino acid catabolite pathways, which has been linked to expression of virulence genes in many pathogens and coordinately regulate the disease progression in vivo studies. However, in some scenarios, differences observed at the transcript level could not reflect the real differences at the protein level. Therefore, to confirm the differences in phenotype and virulence of SK36 and ΔCcpA, we characterized the role of CcpA in the regulation of biofilm development, EPS production and the virulence of Streptococcus sanguinis. Results showed CcpA inactivation impaired biofilm and EPS formation, and CcpA also involved in virulence in rabbit infective endocarditis model. These findings will undoubtedly contribute to investigate the mechanistic links between the global regulator CcpA and the virulence of Streptococcus sanguinis, further broaden our understanding of the relationship between basic metabolic processes and virulence.
Highlights
Infective endocarditis (IE) caused by microorganisms has long been regarded as dependent upon biofilms (Costerton et al, 1999; Douglas, 2003; Parsek and Singh, 2003; Xu et al, 2003)
We analyzed the transcriptional profile of S. sanguinis SK36 wild-type and its CcpA-null derivative ( CcpA) by RNA-seq and provided a global view of potential targets that regulator CcpA regulated
We found that 169 unigenes were significantly differentially expressed when deleted CcpA in S. sanguinis comparing to wild type SK36 (Table 2)
Summary
Infective endocarditis (IE) caused by microorganisms has long been regarded as dependent upon biofilms (Costerton et al, 1999; Douglas, 2003; Parsek and Singh, 2003; Xu et al, 2003). CcpA has been reported to influence the expression of diverse virulence factors of S. aureus, Streptococcus mutans, and Enterococcus faecium in response to various kinds and concentrations of carbohydrate (Somarajan et al, 2014; Bischoff et al, 2017; Bauer et al, 2018). Considering that CcpA is widely conserved, and the overall CPS structural similarity that exists between viridans group suggests a common biosynthetic pathway for these molecules (Xu et al, 2003; Yang et al, 2009; Skov Sorensen et al, 2016), which prompted us to characterize the role CcpA plays in the biofilm development, EPS production and virulence of S. sanguinis and further to identify potential targets of global regulator CcpA regulated that contribute to cause IE
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