Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2007
Publication Date: July 8, 2007
Citation: Lippolis, J.D., Reinhardt, T.A. 2007. Changes in protein expression in Escherichia coli as a consequence of growth in milk whey [abstract]. 2007 Joint Meeting-American Dairy Science Association, Poultry Science Association, Asociacion Mexicana de Produccion Animal, American Society of Animal Sciences. p. 8. Technical Abstract: Understanding changes in protein expression by bacteria as they adapt to their environment and the pressures exerted by the host immune system to eliminate the bacteria will become a foundation to research into better therapeutics for treatment of bacterial infections. Shotgun Proteomics, using amine-reactive isobaric tags (iTRAQ) was used to quantify protein changes in Escherichia coli (mastitis isolate) grown in either Luria-Bertoni broth or milk whey. Changes in expression for over 264 proteins were obtained, 74 proteins that were down-regulated when the bacteria were grown in whey, 66 that were up-regulated, and the rest were unchanged. Several proteins of immediate interest were those involved in iron transport. Iron(III) dicitrate transport protein (FECA) and Iron(III) dicitrate-binding periplasmic protein (FECB) were both up-regulated in E. coli when grown in whey by approximately 3.0 fold. An innate mechanism to limit bacterial growth is the sequestration of free iron by proteins such a lactoferrin. Therefore, necessary for successful growth in milk, bacteria must increase expression of proteins that bind and internalize iron. Our proteomic profiling suggests E. coli responded to the milk environment by increasing its own iron-binding proteins. Two proteins associated with osmotic regulation were also up-regulated when the E. coli was grown in whey. Osmotically-induced protein Y (OSMY) and Osmotically-inducible lipoprotein E (OSME) were up-regulated 4 and 5 fold, respectively. There is evidence that osmotic regulation plays an important role in bacterial virulence by either affecting expression of virulence genes or affecting bacterial growth in vivo. These data demonstrate that quantitative shotgun proteomics has great potential to provide new insights into how bacteria thrive in milk and may provide new insights into antibiotic therapies.