Factors affecting gene expression and activity of heme- and manganese-dependent catalases in Lactobacillus casei strains.

Catalases reduce oxidative stress by degrading hydrogen peroxide to molecular oxygen and water. The presence of heme-dependent or manganese-dependent catalases was observed for a long time in lactic acid bacteria (LAB) but, to date, knowledge on the factors affecting gene expression and enzymatic functionality are limited to a very few strains. In this study, the effect of atmosphere of incubation (not aerated static growth vs aerated shaken growth) and supplementation with Fe, hemin, Mn or their combinations on the catalase production of respiration-competent strain Lactobacillus casei N87 was evaluated using a 2 factorial design. Kinetics of growth, enzymatic activity, tolerance of oxidative stress and expression of heme- and Mn-catalase genes were assessed. A phylogenetic analysis of heme- and Mn-catalase sequences retrieved for all published LAB genomes was performed. The presence of cofactors, especially when combined, improved biomass production in L. casei N87 in both aerated and not aerated conditions. The genome of L. casei N87 harboured sequences for both catalases and hemin and Mn supplementation was crucial for gene expression and enzyme functionality. Iron and oxygen had an additive stimulatory effect. Tolerance of oxidative stress was higher in aerated cultures supplemented with hemin and/or Mn, because of high catalase activities. The presence of both enzymes was confirmed in other respirative strains of L. casei. Clustering of catalase sequences reflected in most of cases the phylogenetic distance between LAB genomes, but in other cases significant differences were found within the same genus, indicating a different evolutionary history. The occurrence of both genes is rare in LAB genomes. The exploitation of LAB with both heme- and Mn-catalases may ensure protection from oxidative stress in different conditions and may be relevant for several food (reduction of oxidative processes on food components) and health (prevention of human diseases) related applications.