Search

When proteins are damaged under stresses conditions, these proteins are either refolded or degraded by quality control system of molecular chaperones and protease. High-temperature requirement A (htrA) is of particular interest because it can perform the roles of both protease and a chaperone. HtrA plays an important role in maintaining the physiological homeostasis of bacteria against environmental stress such as elevated temperature, oxidative and osmotic stress. Inactivation of htrA genes can thus restrict the survival ability of bacteria. These observations suggested that htrA might be responsible for acid tolerance of Streptococcus mutans. In this study, we have generated an htrA mutant and an htrA-complemented strain of S. mutans K7 isolated from a Korean in order to investigate the role of htrA in growth under acidic conditions. In terms of growth under cidic conditions, the htrA mutant exhibited 20% to 23% lower growth than the control group. In addition, glucosyltransferase B and glucosyltransferase C expression levels significantly decreased. When the htrA expression level was restored by adding the htrA gene to the htrA mutant strain, the normal growth phenotype was restored under acid stress. Further, similar results were obtained for S. mutans UA159. Thus, htrA in S. mutans K7, as well as S. mutans UA159, can be concluded to play an important role during acid stress.

Background: Helicobacter pylori is a causative agent of gastritis, and H. pylori infection is thought to be correlated with iron-deficiency anemia (IDA) at puberty. The H. pylori feoB gene product, a high-affinity ferrous iron transporter, plays a central role in iron acquisition and virulence. This study was undertaken to analyze H. pylori feoB status according to clinical data, including antral gastritis with or without IDA., Methods: Fourteen H. pylori-positive patients aged from 10 to 18 years were categorized into subgroups based on the presence or absence of IDA. Eight patients were diagnosed as having IDA; the other six showed normal hematological findings. Genomic DNA was isolated from H. pylori cultured from each gastric biopsy specimen. Five sets of primers were used for the PCR amplification of the feoB gene. Linking and sequencing of PCR products generated the feoB region, which was 1.93 kb in size. The feoB gene sequences of H. pylori J99 and 26695 were compared with the clinical strains, and the sequences of feoB regions in the IDA (+) and (-) groups were compared., Results: Sequence analysis of the complete coding region of the feoB gene revealed 16 sites of polymorphism or mutation. Among these, three polymorphisms (E/T254A, I263V, and K511Q) were indigenous to the Korean clinical strains. Although statistically significant differences were observed at four sites (K127T, A273S/P, I438V and I441T) between IDA (+) and (-), the number of specimens was too low to assess the significance of the differences., Conclusion: The four polymorphisms of the feoB gene observed appear to be related to the clinical phenotype of IDA, but the relation is unclear because of the small number of strains studied. Further studies are required to confirm a correlation between IDA and H. pylori infection.