Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/14/2021
Publication Date: 6/14/2021
Citation: Kudva, I.T., Trachsel, J.M., Biernbaum, E.N., Lippolis, J.D. 2021. Escherichia coli O157 differentially express proteins with a potential role in bacterial adaptation and survival in vivo in the rumen of cattle. Meeting Abstract. https://www.abstractsonline.com/pp8/#!/9286/presentation/12063.
Technical Abstract: Towards new insights into bacterial adaptation and survival, we examined O157 proteins expressed in the bovine rumen fluid/rumen environment. In our previous study, we had examined growth of three O157 strains, 86-24, EDL933 and super-shed SS17, in rumen fluid of disparate compositions, both in-vitro and in-vivo. Animals fed the maintenance diet (high fiber) had rumen fluid with a pH of 6.2-7.0 and total volatile fatty acid (VFA) concentrations of 109 - 141 µM/ml (Maintenance Rumen Fluid/MRF), and those fed the lactation diet (high protein), a ruminal pH of 5.14 -6.0 with a total VFA of 125 - 241 µM/ml (Lactation Rumen Fluid/LRF). In-vitro, O157 strains 86-24 and EDL933 had similar growth patterns with 2 log reduction in viable counts in MRF and LRF. However, O157 strain SS-17 showed 1 log reduction in MRF and 5 log reduction in LRF, in in-vitro viable counts. In-vivo, all O157 strains showed 2 log reduction in viable counts, in LRF and 1-2 log reduction in MRF. Here, we compared proteomes of individual O157 strains as expressed under each of the above growth and dietary conditions using label-based Isobaric Tagging Technology for Relative Quantitation/iTRAQ, to determine if protein expressed could be contributing to the observed growth patterns. The O157 strain 86-24 proteome expressed in-vitro in MRF was used as the reference. The extracted tandem mass spectra were analyzed using Mascot, Sequest (XCorr Only) and X! Tandem. Scaffold Q+ v 4.9.0 was used to validate the peptide and protein identifications. In addition, the raw data was analyzed using label free Intensity Based Absolute Quantification/iBAQ to identify peptides/proteins missed by iTRAQ due to possible loss of labels. Using iBAQ, post-statistical verification, we detected a total of 756 O157 proteins: 566 proteins expressed across both diets, 179 uniquely in MRF and 11 uniquely in LRF. More proteins were differentially expressed between the in-vitro and in-vivo conditions in LRF compared to MRF as determined by iTRAQ. With LRF, 43 and 111 O157 proteins were more highly expressed in-vitro and in-vivo, respectively. With MRF, 25 and 56 O157 proteins were more highly expressed in-vitro and in-vivo, respectively. We have stringently shortlisted 89 and 87 O157 proteins expressed in LRF and MRF, respectively, including those with putative roles in metabolism, transport, and environmental adaptation, for further evaluation. We anticipate a subset of such proteins will play a role in O157 survival in the bovine rumen and hence could be targeted for developing preharvest O157 control modalities.