Salivaricin E and abundant dextranase activity may contribute to the anti-cariogenic potential of the probiotic candidate Streptococcus salivarius JH

Abstract

Dental caries is an infectious disease that is continuing to increase in prevalence, reducing the quality of life for millions worldwide as well as causing considerable expense, with an estimated US$108 billion spent on dental care in the USA each year. Oral probiotics are now being investigated to determine whether they could play a role in the prevention and treatment of this disease. Streptococcus salivarius strain JH is a potential probiotic candidate that produces multiple proteinaceous antimicrobials (bacteriocins), the inhibitory spectrum of which includes Streptococcus mutans, one of the principal causative agents of dental caries. The genome of strain JH has previously been shown to contain the biosynthetic loci for the bacteriocins salivaricin A3, streptin and streptococcin SA-FF22. Here we show that strain JH also produces salivaricin E, a 32 aa lantibiotic with a mass of 3565.9 Da, which is responsible for the inhibition of S. mutans growth. In addition, strain JH was shown to produce dextranase, an enzyme that hydrolyses (1R6)-a-D-glucosidic linkages, at levels higher than any other S. salivarius tested. In vitro testing showed that partial hydrolysis of the exopolymeric substances of S. mutans, using strain JH dextranase, improved the anti-S. mutans inhibitory activity of the lytic bacteriocin, zoocin A. The multiple bacteriocin and dextranase activities of strain JH support its candidature for development as an oral probiotic.

Bacteriocin production: a relatively unharnessed probiotic trait?

“…salivarius that persist strongly but demonstrate poor bacteriocin production 44 . Additionally, the identification of novel bacteriocins, including salivaricin 9 45 and the recently identified salivaricin E 46 , from this species continues to enhance the probiotic potential of S . salivarius .…”

Genome Sequencing Reveals a Large and Diverse Repertoire of Antimicrobial Peptides

“…Singletons (single genotypes with no closely related variant) were excluded from the count. Synonym(s) for the previously identified bacteriocins are as follows: b Pneumolancidin (Maricic et al, 2016) and salivaricin E (Walker et al, 2016); c lcpAMT (Kadam et al, 2017) and ICESp23FST81 lantibiotic (Croucher et al, 2008); d SP23-BS72 lantibiotic (Begley et al, 2009); e Phr lantibiotic (Hoover et al, 2015); f Pneumocyclicin (Bogaardt et al, 2015); g cibAB (Guiral et al, 2005); h spi and pnc (Bogaardt et al, 2015). …”

Rapid oral bacteria detection based on real-time PCR for the forensic identification of saliva

“…Four saliva samples were cultured on blood agar plates (KOMED, Seongnam Korea) supplemented with 1.5% (w/v) pancreatic digest of casein, 0.5% (w/v) pancreatic digest of soybean meal, 5% sheep blood, 0.5% (w/v) sodium chloride (NaCl), and 1.5% (w/v) agar. All cultures were incubated for 18 h in an atmosphere of natural air at 37 °C 49 . Colonies were amplified using the MicroSEQ.…”