Cytosolic Proteomes of Lactobacillus rhamnosus ATCC27773 Cells Grown in pH 5.5 and 6.5

Lactobacillus rhamnosus is an important bacterium from a health and industry perspective. Cytoplasmic proteomes of L. rhamnosus ATCC2773 were studied to elucidate the specific growth condition variations and the changes occurring in the protein expression patterns of this bacterium when cultivated in a standard rich medium under two different pH conditions (pH 6.4 and 5.5). A total of 220 proteins were identified and compared by quantitative proteomic analysis using iTRAQ LC-MS/MS. A functional classification of the cytoplasmic proteins of L. rhamnosus revealed translation and carbohydrate metabolism associated proteins as the major groups. A comparison of proteome data showed that the majority of proteins (89%) have similar expression patterns in cells grown in pH 6.5 and 5.5. The key differences observed in the proteomes of L. rhamnosus grown in pH 6.5 and 5.5 were: 19 proteins were present at pH 5.5 but not expressed at pH 6.5 and six proteins were expressed at pH 6.5 but not at pH 5.5. Specific proteins were induced by each condition: 14 and 23 proteins in response to pH 6.5 and pH 5.5, respectively. This study illustrated the impact of culture conditions on the proteome of L. rhamnosus.