MALDI TOF mass spectrometry can be used to identify changes in the protein composition of rumen bacteria : the response of the novel ruminal bacterium LPLR3-7 when grown in the presence of diaminopropionic acid

Abstract

The hypothesis that matrix assisted laser desorption ionization time of flight (MALDI TOF) mass spectrometry can be used to identify changes in the protein composition of rumen bacteria was tested. We used MALDI TOF mass spectrometry to identify the proteins responsible for the ability to degrade diaminopropionic acid (DAPA), a non-protein amino acid found in the forage legumes Lathyrus spp. and Acacia angustissima, by a novel ruminal bacterial isolate, LPLR3-7. LPLR3-7 was grown on 3 different growth media containing either nutrient supplements (nutrient) or 10mM DAPA (DAPA) or both (nutrient/DAPA). A MALDI TOF mass spectrometer was used to determine the protein composition of whole cells, of cell-free extracts and of cell debris, from cells grown on each of the different treatment media. LPLR3-7 altered its protein composition when grown in the presence of DAPA. A peak cluster at 9700 Da in the cell free extract showed a direct relation to the presence and absence of DAPA. MALDI TOF mass spectrometry was successfully used to examine protein composition in ruminal bacteria. The process allowed identification of changes in protein composition in this ruminal bacterium in response to a toxin. However, the profiles produced for entire cell protein composition by the MALDITOF technique are complex and difficult to interpret and compare between samples.