(1→3)-α-D-Glucan hydrolases in dental biofilm prevention and control: A review.

Dental plaque is a highly diverse biofilm, which has an important function in maintenance of oral and systemic health but in some conditions becomes a cause of oral diseases. In addition to mechanical plaque removal, current methods of dental plaque control involve the use of chemical agents against biofilm pathogens, which however, given the complexity of the oral microbiome, is not sufficiently effective. Hence, there is a need for development of new anti-biofilm approaches. Polysaccharides, especially (1→3),(1→6)-α-D-glucans, which are key structural and functional constituents of the biofilm matrix, seem to be a good target for future therapeutic strategies. In this review, we have focused on (1→3)-α-glucanases, which can limit the cariogenic properties of the dental plaque extracellular polysaccharides. These enzymes are not widely known and have not been exhaustively described in literature.

Legionella dumoffii utilizes exogenous choline for phosphatidylcholine synthesis.

Phosphatidycholine (PC) is the major membrane-forming phospholipid in eukaryotes but it has been found in only a limited number of prokaryotes. Bacteria synthesize PC via the phospholipid N-methylation pathway (Pmt) or via the phosphatidylcholine synthase pathway (Pcs) or both. Here, we demonstrated that Legionella dumoffii has the ability to utilize exogenous choline for phosphatidylcholine (PC) synthesis when bacteria grow in the presence of choline. The Pcs seems to be a primary pathway for synthesis of this phospholipid in L. dumoffii. Structurally different PC species were distributed in the outer and inner membranes. As shown by the LC/ESI-MS analyses, PC15:0/15:0, PC16:0/15:0, and PC17:0/17:1 were identified in the outer membrane and PC14:0/16:0, PC16:0/17:1, and PC20:0/15:0 in the inner membrane. L. dumoffii pcsA gene encoding phosphatidylcholine synthase revealed the highest sequence identity to pcsA of L. bozemanae (82%) and L. longbeachae (81%) and lower identity to pcsA of L. drancourtii (78%) and L. pneumophila (71%). The level of TNF-α in THP1-differentiated cells induced by live and temperature-killed L. dumoffii cultured on a medium supplemented with choline was assessed. Live L. dumoffii bacteria cultured on the choline-supplemented medium induced TNF-α three-fold less efficiently than cells grown on the non-supplemented medium. There is an evident effect of PC modification, which impairs the macrophage inflammatory response.

Water-soluble (1→3),(1→4)-α-D-glucan from mango as a novel inducer of cariogenic biofilm-degrading enzyme.

A water-soluble polysaccharide (WSP) extracted from mango (Mangifera indica L.) fruits has been suggested as a new alternative to mutan for mutanase induction in Trichoderma harzianum. Structural analyses revealed that the purified WSP was a (1→3),(1→4)-α-D-glucan with the molecular mass of ca. 760 kDa in which the (1→4)-linked and (1→3)-linked α-Glcp residues were in a ratio of 1:2.4. When the strain T harzianum CCM F-340 was grown in the presence of WSP, the maximal enzyme productivity obtained after 3 days of cultivation was 34 mU/mL. The mango WSP proved to be a very effective stimulus of mutanase expression giving a 5.1-fold higher than without WSP, transcription. It was shown that the mixture of WSP-induced mutanase and commercial dextranase had a high hydrolytic potential in the reaction with streptococcal mutan, where maximal degrees of solubilization and saccharification of this biopolymer (93.4% and 80%, respectively) were reached within 9h (solubilization) and 24h (saccharification). The mixed enzymatic preparation was also effective in degradation of streptococcal mutan and its removal from cariogenic biofilms. After 3h hydrolysis, only 18.2% of the biofilm remained adhered to the glass surface.

Modulation of rosR expression and exopolysaccharide production in Rhizobium leguminosarum bv. trifolii by phosphate and clover root exudates.

The acidic exopolysaccharide (EPS) secreted in large amounts by the symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum bv. trifolii is required for the establishment of an effective symbiosis with the host plant Trifolium spp. EPS biosynthesis in rhizobia is a very complex process regulated at both transcriptional and post-transcriptional levels and influenced by various nutritional and environmental conditions. The R. leguminosarum bv. trifolii rosR gene encodes a transcriptional regulator with a C(2)H(2) type zinc-finger motif involved in positive regulation of EPS synthesis. In silico sequence analysis of the 450-bp long rosR upstream region revealed the presence of several inverted repeats (IR1 to IR6) and motifs with significant identity to consensus sequences recognized by PhoB and LysR-type proteins associated with phosphate- and flavonoid-dependent gene regulation in R. leguminosarum. Using a set of sequentially truncated rosR-lacZ transcriptional fusions, the role of the individual motifs and the effect of phosphate and clover root exudates on rosR expression were established. In addition, the significance of IR4 inverted repeats in the repression, and P2-10 hexamer in the activation of rosR transcription, respectively, was found. The expression of rosR increased in the presence of phosphate (0.1-20 mM) and clover root exudates (10 µM). PHO boxes and the LysR motif located upstream of the rosR translation start site were engaged in the regulation of rosR transcription. The synthesis of EPS and biofilm formation decreased at high phosphate concentrations, but increased in the presence of clover root exudates, indicating a complex regulation of these processes.