Overall, fewer O157 proteins were detected in more nutritionally complex RF-preparations versus LB and among these, differences were observed based on availability of oxygen, nutrients and incubation time. Also, the O157-proteome in the RF-preparations included more proteins with diverse functions at 48 h than after 14 days of incubation. In fact, proteins associated with adherence, cell division and growth were identified only at 48 h. However, under all
conditions, a selective expression of proteins with a role in cell structure, transport, metabolism, chemotaxis, motility, resistance, stress and regulation was observed in RF-preparations selleck inhibitor , many of which were up-regulated in the unfiltered rumen fluid. The O157 growth patterns and proteome expressed in the rumen fluid is suggestive of an adapting O157, expending
minimal energy, preparing for survival and downstream intestinal colonization. Since adult cattle are often fed a maintenance diet with less protein until ready for feedlots, we decided to analyze O157 growth dynamics in rumen fluid derived from animals on this diet. Rumen fluid from cattle fed a diet low in protein usually has a pH ranging from 6.2-6.8, and VFA concentrations at, 60-70% acetic acid, 15-20% propionic acid, 5-15% butyric acid [28–31]. The rumen fluid VFA and pH values were within the limits described for this diet for both animals used in this study (Tables 1 and 2; 26–29). Irrespective of incubation times (14 days versus 48 h), O157 exhibited Lazertinib research buy very distinctive growth patterns in RF-preparations selleckchem compared to LB. O157 cultures Amobarbital in dRF, fRF and uRF were consistently at lower optical densities than LB, under both aerobic and anaerobic conditions. The anaerobic RF-preparation cultures never reached an OD600 ≅ 1.0 and the viable O157 recovered were at substantially lower counts when compared to LB. The low OD readings and viable counts recovered from RF-preparation
grown cultures may have been due to inhibitory factors and /or limited nutrients in dRF, fRF, uRF, not seen in LB, having a bacteriostatic (aerobic) or bactericidal (anaerobic) effect on O157 and reflective of O157 growth in a stressful environment [11, 32–36]. Using LB media for estimating viable counts may have helped recover the stressed bacteria . Similar recovery of viable bacteria despite low OD reading has been reported among bacteria exposed to antimicrobial stress , and limited growth has been associated with bacteria entering into a stressed/starved state or stationary phase [35–37]. Overall, fewer O157 proteins were detected in RF-preparation cultures compared to LB, especially under anaerobic conditions.