Peroxide stress in Sigma54 mutant and Wt

Analyses of the Wild type and the sigma 54 mutant strain NZ7306 with and without peroxide treatment: A Lactobacillus plantarum strain with a deletion in the alternative sigma factor 54 (?54) encoding gene rpoN, displayed a 100 fold higher sensitivity to peroxide as compared to its parental strain. This feature could be due to ?54-dependent regulation of genes involved in peroxide stress response. However, transcriptome analyses of the wild type and the mutant strain during peroxide exposure did not support such a role for ?54. Subsequent experiments revealed that the impaired expression of the mannose PTS operon in the rpoN mutant caused the observed increased peroxide sensitivity. Keywords: genetic modification Two conditions were tested in the transcriptome comparison, the condition “peroxide stress exposure” and the condition “deletion of the rpoN-gene”. This resulted in 4 samples: “Wild type normal”, “rpoN-mutant normal”, “Wild type with peroxide”, and “rpoN-mutant with peroxide”. Samples were hybridised against a sample with only one variation, resulting in a total of 4 hybridisations (“Wild type vs Mutant”, “Wild type vs Wild type peroxide”, “Mutant vs Mutant peroxide”, and “Wild type peroxide vs Mutant peroxide”). The experiment was performed in duplicate (duplicates are designated A and B) and in order to discriminate the variation between the duplicates additional hybridisation were performed: “Wild type A vs Wild type B” and “Mutant with peroxide A vs Mutant with peroxide B”. This resulted in a total of 10 hybridisations (2 x 4 and 2).