The major surface glycoprotein (MSG) of Pneumocystis carinii is encoded by a family of related but distinct genes distributed throughout the P. carinii genome. Previous reports of the genomic and mRNA MSG structure suggested that there was a highly conserved 5'-untranslated region and a highly variable translated region. In the current study, we demonstrate that there is a single expression site for MSG expression and that different MSG genes are located downstream of this expression site. Isolation of a genomic clone containing the putative 5'-untranslated region has demonstrated that there was a single base sequencing error in what was considered to be the untranslated region. The corrected sequence reveals an extended open reading frame encoding a constant amino-terminal leader domain, with a typical signal peptide, for the MSG protein family. Since this constant amino-terminal domain is encoded by a single copy genomic sequence, a recombination/gene conversion-mediated antigenic switching event is required to effect the known variability in expressed MSG sequences. Therefore, like some bacterial and protozoan pathogens, the opportunistic fungal pathogen P. carinii contains a constant genomic site dedicated to MSG expression and a switchable downstream region for the variable part of the MSG gene family.
This study was conducted to investigate lactobacillus salivarius subsp. salivarius having probiotic properties to be used as the health adjuncts with fermented milk products. Acid-and bile-tolerant lactobacillus salivarius subsp. salivarius was isolated with lactobacilli MRS broth from faeces of 80 healthy persons (infants, children and adults). It was used as a probiotic strain in fermented milk products. The pH of fermented milk decreased from pH 6.7 to 5.0 and titratable acidity increased from 0.3% to 1.0% by L. salivarius subsp. salivarius (isolation strain 20, 35, and 37), when incubated for 36 h at 37°C. The number of viable cell counts of fermented milk was maximized at this incubation condition. The SDS-PAGE evidenced no significant change of casein but distinct changes of whey protein were observed by isolated L. salivarius subsp. salivarius for titratable acidity being incubated by 0.9-1.0% at 37°C. All of the strains produced 83.43 to 131.96 mM of lactic acid and 5.39 to 26.85 mM of isobutyric acid in fermented products. The in vitro culture experiment was performed to evaluate ability to reduce cholesterol levels and antimicrobial activity in the growth medium. The selected L. salivarius subsp. salivarius reduced 23-38% of cholesterol content in lactobacilli MRS broth during bacterial growth for 24 h at 37°C. All of the isolated L. salivarius subsp. salivarius had an excellent antibacterial activity with 15-25 mm of inhibition zone to E. coli KCTC1039, S. enteritidis KCCM3313, S. typhimurium M-15, and S. typhimurium KCCM40253 when its pH had not been adjusted. Also, all of the isolated L. salivarius subsp. salivarius had partial inhibition zone to E. coli KCTC1039, E. coli KCTC0115 and S. enteritidis KCCM3313 when it had been adjusted to pH 5.7. The selected strains were determined to have resistances of twelve antibiotic. Strains 27 and 35 among the L. salivarius subsp. salivarius showed the highest resistance to the antibiotics. These results indicated that some of the L. salivarius subsp. salivarius (strain 27 and 35) are considered as effective probiotic strains with a potential for industrial applications, but the further study is needed to establish their use as probiotics in vivo.
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