Cold-adapted H2O2 Tolerant Bacteria and their Catalases
Isao Yumoto and Isao Hara
from: Cold-Adapted Microorganisms (Edited by: Isao Yumoto). Caister Academic Press, U.K. (2013)
Three novel species of psychrotolerant H2O2-resistant bacteria have been isolated from drain pools of a fish egg processing plant that uses H2O2 as a bleaching agent. Among them Vibrio rumoiensis was isolated from downstream of the drain pool, whereas Exiguobacterium oxidotolerans and Psychrobacter piscatorii were isolated from upstream. The catalase activity in the cell extract of the former was lower than that in the latter, which reflected the H2O2 concentration in their niches. The VktA (catalase from V. rumoiensis) and PktA (catalase from P. piscatorii) belonged to clade III, and EktA (catalase from E. oxidotolerans) belonged to clade I. From the temperature profile of their activities, these catalases exhibited heat sensitivity at higher than 60°C. The cell extract of V. rumoiensis exhibited lower catalase content (1.8%) than that of P. piscatorii (10%), whereas the former produces VktA, which exhibited a higher catalytic efficiency than the PktA. EktA content in the cell extract of E. oxidotolerans was 6.5% and EktA exhibited the highest catalase activity in both cell extract and the purified form among the three catalases. EktA possesses a wider bottleneck structure in the main channel for accepting substrates, enable it to react efficient with organic peroxides larger than H2O2 as substrates. Considering the environmental adaptation and distribution of microorganisms in this unique niche with high concentrations of H2O2 and low temperatures, certain variations of unknown bacterial species exist with certain variations of environmental adaptation mechanisms (e.g., cellular localization, production rate, and catalytic efficiency of catalase) depending on the environmental H2O2 concentration and fragility of cells. Furthermore, the characteristics of these catalase molecules reflect the environmental conditions (low temperatures and high concentrations of H2O2) under which these bacteria survive read more ...