An Update on the Evolution of Glucosyltransferase (Gtf) Genes in Streptococcus

Abstract

In many caries-promoting Streptococcus species, glucosyltransferases (Gtfs) are recognized as key enzymes contributing to the modification of biofilm structures, disruption of homeostasis of healthy microbiota community and induction of caries development. It is therefore of great interest to investigate how Gtf genes have evolved in Streptococcus. In this study, we conducted a comprehensive survey of Gtf genes among 872 streptococci genomes of 37 species and identified Gtf genes from 364 genomes of 18 species. To clarify the relationships of these Gtf genes, 45 representative sequences were used for phylogenic analysis, which revealed two clear clades. Clade I included 12 Gtf genes from nine caries-promoting species of the Mutans and Downei groups, which produce enzymes known to synthesize sticky, water-insoluble glucans (WIG) that are critical for modifying biofilm structures. Clade II primarily contained Gtf genes responsible for synthesizing water-soluble glucans (WSG) from all 18 species, and this clade further diverged into three subclades (IIA, IIB, and IIC). An analysis of 16 pairs of duplicated Gtf genes revealed high divergence levels at the C-terminal repeat regions, with ratios of the non-synonymous substitution rate (dN) to synonymous substitution rate (dS) ranging from 0.60 to 1.03, indicating an overall relaxed constraint in this region. However, among the clade I Gtf genes, some individual repeat units possessed strong functional constraints by the same criterion. Structural variations in the repeat regions were also observed, with detection of deletions or recent duplications of individual repeat units. Overall, by establishing an updated phylogeny and further elucidating their evolutionary patterns, this work enabled us to gain a greater understanding of the origination and divergence of Gtf genes in Streptococcus.

Streptococcus oriscaviae sp. nov. Infection Associated with Guinea Pigs

“…The complete genome of S. oriscaviae HKU75 T identified in this study contained homologs of several virulence genes found in streptococci ( Table 3 ). Examples of these genes include glucosyltransferases ( gtfA ), fibronectin-binding protein ( pavA ), collagen-binding protein ( cpbA ), laminin-binding protein ( lmb ) and enolase ( eno ); these genes are known to be involved in adhesion, colonization, internalization, or invasion ( 19 – 24 ).…”

PcsB Expression Diversity Influences on Streptococcus mitis Phenotypes Associated With Host Persistence and Virulence

“…To further address if PcsB expression influences the strain capacity to bind sucrose-derived EPS, we selected strains with the highest ( n = 4; strains SK569, SK579, SK616, SK1073) and lowest ( n = 4; strains SK575, 38–4, 35–15, 26–2) levels of PcsB (produced under aerobic conditions) to compare bacterial aggregation mediated by sucrose-derived EPS. Of note, different from S. mutans , S. mitis does not secrete glucosyltransferase enzymes (Gtfs) required for the synthesis of insoluble glucan EPS from sucrose (Xu et al, 2018). Therefore, to supply S. mitis cultures with sucrose-derived EPS, S. mitis aggregation was assessed in filter-sterilized BHI culture supernatants of S. mutans MT8148 (which contain secreted Gtfs: GtfB, GtfC and GtfD) supplemented with sucrose.…”

“…These enzymes retain activity once bound to the surface of bacterial species that typically co-habit dental biofilms (Bowen and Koo, 2011). Different from S. mutans and other streptococcal species of dental biofilms, the genomes of S. mitis strains do not harbor genes encoding Gtfs (Xu et al, 2018). This is consistent with the reduced S. mitis aggregation observed in BHI supplemented with sucrose, a phenotype also reported in S. mutans gtfBCD isogenic mutants (Alves et al, 2016).…”

Usnic acid deteriorates acidogenicity, acidurance and glucose metabolism of Streptococcus mutans through downregulation of two-component signal transduction systems

“…GtfD predominantly synthesizes water soluble glucans 36 . Reports have demonstrated that Gtfs are recognized as pivotal contributors for the alteration of biofilm architecture, disruption of homeostasis in the community of healthy microbiota and induction of caries progression 37 . Ren et al, in 2016 have pronounced that molecules that target the glycosyltransferase possess the ability to inhibit biofilm formation and cariogenicity of S. mutans 38 .…”