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Highlights • The global lineage of M. caseolyticus strains were divided into four clades from A to D. • MLST typing revealed novel alleles in M. caseolyticus strains isolated in China. • Global clades carried significantly less AMR genes and more virulence factors than present isolates. • As the close relative of the genus Staphylococcus , Macrococcus caseolyticus has a larger diameter and thicker cell wall compared with S.aureus ATCC 25923. • Macrococcus caseolyticus may serve as a vector for methicillin resistance habitats in foodborne microorganisms.

Abstract Background Nattokinase (NK), which is a member of the subtilisin family, is a potent fibrinolytic enzyme that might be useful for thrombosis therapy. Extensive work has been done to improve its production for the food industry. The aim of our study was to enhance NK production by tandem promoters in Bacillus subtilis WB800. Results Six recombinant strains harboring different plasmids with a single promoter (P P43 , P HpaII , P BcaprE , P gsiB , P yxiE or P luxS ) were constructed, and the analysis of the fibrinolytic activity showed that P P43 and P HpaII exhibited a higher expression activity than that of the others. The NK yield that was mediated by P P43 and P HpaII reached 140.5 ± 3.9 FU/ml and 110.8 ± 3.6 FU/ml, respectively. These promoters were arranged in tandem to enhance the expression level of NK, and our results indicated that the arrangement of promoters in tandem has intrinsic effects on the NK expression level. As the number of repetitive P P43 or P HpaII increased, the expression level of NK was enhanced up to the triple-promoter, but did not increase unconditionally. In addition, the repetitive core region of P P43 or P HpaII could effectively enhance NK production. Eight triple-promoters with P P43 and P HpaII in different orders were constructed, and the highest yield of NK finally reached 264.2 ± 7.0 FU/ml, which was mediated by the promoter P HpaII -P HpaII -P P43 . The scale-up production of NK that was promoted by P HpaII -P HpaII -P P43 was also carried out in a 5-L fermenter, and the NK activity reached 816.7 ± 30.0 FU/mL. Conclusions Our studies demonstrated that NK was efficiently overproduced by tandem promoters in Bacillus subtilis. The highest fibrinolytic activity was promoted by P HpaII -P HpaII -P P43 , which was much higher than that had been reported in previous studies. These multiple tandem promoters were used successfully to control NK expression and might be useful for improving the expression level of the other genes.

Background: The sequences of the 16S rRNA genes extracted from fecal samples provide insights into the dynamics of fecal microflora. This potentially gives valuable etiological information for patients whose conditions have been ascribed to unknown pathogens, which cannot be accomplished using routine culture methods. We studied 33 children with diarrhea who were admitted to the Children's Hospital in Shanxi Province during 2006. Results: Nineteen of 33 children with diarrhea could not be etiologically diagnosed by routine culture and polymerase chain reaction methods. Eleven of 19 children with diarrhea of unknown etiology had Streptococcus as the most dominant fecal bacterial genus at admission. Eight of nine children whom three consecutive fecal samples were collected had Streptococcus as the dominant fecal bacterial genus, including three in the Streptococcus bovis group and three Streptococcus sp., which was reduced during and after recovery. We isolated strains that were possibly from the S. bovis group from feces sampled at admission, which were then identified as Streptococcus lutetiensis from one child and Streptococcus gallolyticus subsp. pasteurianus from two children. We sequenced the genome of S. lutetiensis and identified five antibiotic islands, two pathogenicity islands, and five unique genomic islands. The identified virulence genes included hemolytic toxin cylZ of Streptococcus agalactiae and sortase associated with colonization of pathogenic streptococci. Conclusions: We identified S. lutetiensis and S. gallolyticus subsp. pasteurianus from children with diarrhea of unknown etiology, and found pathogenic islands and virulence genes in the genome of S. lutetiensis. [ABSTRACT FROM AUTHOR]