Biological Role of Mn-catalase in Select Lactobacilli
Abstract (Summary)Mechanisms for protection against oxidative stress within species of Lactobacillus vary widely, encompassing manganese accumulation, peroxidases, and both heme and non-heme (Manganese containing) catalases. While most species of Lactobacillus accumulate manganese, to mM levels, and contain peroxidases, heme and manganese catalases are limited to a select few lactobacilli. Furthermore, manganese catalases are documented in only two Lactobacillus species, one of which is Lactobacillus plantarum ATCC 14431. Therefore, the presence of catalases in lactobacilli represents a unique opportunity to investigate both the biological role and potential advantages associated with having Mn-catalase in the native host as well as in Lactobacillus species utilized in the food industry and as probiotics, that are normally lacking catalases. To address the biological role of Mn-catalase, a mnkat- strain of L. plantarum ATCC 14431 was constructed through insertional inactivation. Findings show that Mn-catalase is essential for normal growth of L. plantarum ATCC 14431 under aerobic conditions and that the protein is critical for removing H2O2 generated during aerobic growth. Additionally, the inactivation of mnkat results in an increased sensitivity to exogenous H2O2, though growth in Mn-rich media does improve both general growth and growth in the presence of H2O2. It is also of interest to be able to successfully obtain multiple strains of Lactobacillus that have potential use as starter cultures or probiotics that have an improved antioxidant capacity. To address this, the 1449-bp manganese catalase gene from L. plantarum CECT 221 (ATCC 14431), including its native promoter, has been cloned into the shuttle vector pTRK563. The resulting pMnKat was transformed into L. reuteri NCK 932 and L. gasseri NCK 334. Manganese catalase (Mn-catalase) activity was assayed and detected in both species. Furthermore, expressing MnKat leads to increased growth rate (mmaxâhr-1), increased resistance to H2O2 concentrations as high as 10 mM, and increases long term survival under aerobic conditions.
Advisor:Hosni M. Hassan
School Location:USA - North Carolina
Source Type:Master's Thesis
Date of Publication:06/09/2008