Regulation of H super(+)-ATPase Synthesis in Response to Reduced pH in Ruminal Bacteria

• Published in: Current microbiology 2001-02, Vol.42 (2), p.106-110
• Main Authors: Miwa, Takehiro, Abe, Tetsuo, Fukuda, Shinji, Ohkawara, Sou, Hino, Tsuneo
• Format: Article
• Language: English
• Subjects: H super(+)-transporting ATPase; Ruminococcus albus
• ISSN: 0343-8651; 1432-0991
• DOI: 10.1007/s002840010187

The capacity of ruminal bacteria to regulate H super(+)-ATPase synthesis in response to reduced pH was investigated to explain acid tolerance. The activity of H super(+)-ATPase in Streptococcus bovis, an acid-tolerant bacterium, was 2.2-fold higher at pH 4.5 than at pH 5.5. The increase in the amount of H super(+)-ATPase protein was similar, suggesting that the increase in H super(+)-ATPase activity is owing to the increase in H super(+)-ATPase synthesis. The level of atp-mRNA at pH 4.5 was 2.5-fold higher than at pH 5.5, indicating that H super(+)-ATPase synthesis is regulated at the transcriptional level, responding to low pH. In Ruminococcus albus, an acid-sensitive bacterium, H super(+)-ATPase activity, the amount of H super(+)-ATPase protein, and the level of atp-mRNA at pH 7.0 were similar to the values at pH 6.0, the lowest pH permitting growth. This result suggests that R. albus is incapable of enhancing H super(+)-ATPase synthesis at low pH. Thus, acid tolerance appeared to be related to the capacity to augment the synthesis of H super(+)-ATPase responding to low pH.