Streptococcus mutans plays a key role in the development of dental caries and promotes the formation of oral biofilm produced by glucosyltransferases (GTFs). Bacillus velezensis K68 was isolated from traditional fermented foods and inhibits biofilm formation mediated by S. mutans. Gene amplification results demonstrated that B. velezensis K68 contained genes for the biosynthesis of 1-deoxynojirimycin (1-DNJ), a known GTF expression inhibitor. The presence of the GabT1, Yktc1, and GutB1 genes required for 1-DNJ synthesis in B. velezensis K68 was confirmed. Supernatant from B. velezensis K68 culture medium inhibited biofilm formation by 84% when S. mutans was cultured for 48 h, and inhibited it maximally when 1% glucose was added to the S. mutans culture medium as a GTF substrate. In addition, supernatant from B. velezensis K68 medium containing 3 ppb 1-DNJ decreased S. mutans cell surface hydrophobicity by 79.0 ± 0.8% compared with that of untreated control. The supernatant containing 1-DNJ decreased S. mutans adherence by 99.97% and 98.83% under sugar-dependent and sugar-independent conditions, respectively. S. mutans treated with the supernatant exhibited significantly reduced expression of the essential GTF genes gtfB, gtfC, and gtfD compared to that in the untreated group. Thus, B. velezensis inhibits the biofilm formation, adhesion, and GTF gene expression of S. mutans through 1-DNJ production. IMPORTANCEDental caries is among the most common infectious diseases worldwide, and its development is closely associated with physiological factors of bacteria, such as the biofilm formation and glucosyltransferase production of Streptococcus mutans. Biofilms are difficult to remove once they have formed due to the exopolysaccharide matrix produced by the

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A halophilic archaeon, strain MBLA0036, was isolated from Sorae solar saltern near Incheon, Republic of Korea. Strain MBLA0036 had three 16S rRNA genes: rrnA, rrnB and rrnC. The 16S rRNA gene sequence similarities between strain MBLA0036 (based on the rrnA gene) and Haloplanus ruber R35 and Haloplanus litoreus GX21 were 98.0 and 97.3 %, respectively. The similarities of the RNA polymerase subunit B' gene between strain MBLA0036 and H. ruber R35 and H. litoreus GX21 were 94.0 and 92.1 %, respectively. Cells of strain MBLA0036 were Gram-stain-negative, motile, red-pigmented, pleomorphic, flat and contained gas vesicles. Strain MBLA0036 grew at 15‒55 °C (optimum, 37 °C), in 10‒30 % (w/v) NaCl (15 %, w/v) with 0‒0.5 M MgSO4.7H2O (0.2 M) and at pH 6.0-9.0 (pH 7.0). The cells lysed in distilled water and the minimum NaCl concentration that prevented cell lysis was 5 % (w/v). Major polar lipids of strain MBLA0036 were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and a glycolipid that was chromatographically identical to sulfated mannosyl glucosyl diether. The major isoprenoid quinone was menaquinone-8. The genomic DNA G+C content was 65.5 mol%. DNA-DNA hybridization values between strain MBLA0036 and H. ruber JCM 17271 and H. litoreus JCM 17092 were 35±3 and 18±1 %, respectively. Therefore, strain MBLA0036 is described a novel species of the Haloplanus, for which we propose the name Haloplanusrallus sp. nov. The type strain is MBLA0036 (=KCTC 4239=JCM 31425).

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Clay minerals are classified as kaolinite and montmorillonite minerals, as a class of layered silicates formed from chemical weathering of other silicate minerals on the surface of the earth [1]. Clay minerals with varying amounts of iron, magnesium, alkali metals, alkaline earths, and other cations are present in the interlayer space or in the lattice structure. They have well-known adsorbent properties due to their layered form, with a high internal surface area, high cation-exchange capacity, and good swelling properties in the presence of water [2]. In the Korea Food and Drug Administration, six kinds of clay minerals (diatomaceous earth, kaolin, bentonite, acid clay, talc, and perlite) are listed in the Food Additive Code, and they are used in filtration aids in the beverage, brewing, and fermentation industries [3].Bentonite is a kind of montmorillonite, and it contains various elements such as potassium (K + ), sodium (Na + ), calcium (Ca 2+ ), and aluminum (Al + ) [4]. Bentonites have been investigated for the adsorption of heavy metals and molecular species in a variety of environments and industries and have been identified as low-cost adsorbents [5]. In addition to studies on the physicochemicalWe have isolated and identified 72 bacterial strains from four bentonite samples collected at the mining areas located in Gyeongsangbuk-do, Republic of Korea, and measured their hydrolytic enzyme (α-amylase, protease, and cellulase) activities to identify the isolates with industrial-use potential. Most of the isolates belonged to the Bacillaceae, with minor portions being from the Paenibacillaceae, Micrococcaceae, and Bacillales Family XII at the family level. Of the strains isolated, 33 had extracellular α-amylase activity, 30 strains produced cellulase, and 35 strains produced protease. Strain MBLB1268, having the highest αamylase activity, was identified as Bacillus siamensis (0.38 ± 0.06 U/ml). Bacillus tequilensis MBLB1223, isolated from Byi33-b, showed the highest cellulase activity (0.26 ± 0.04 U/ml), whereas Bacillus wiedmannii MBLB1197, isolated from Zdb130-b, exhibited the highest protease activity (54.99 ± 0.78 U/ml). These findings show that diverse bacteria of the Bacillaceae family adhere to and exist in bentonite and are potential sources of industrially useful hydrolytic enzymes.These authors contributed equally to this work.