Effects of ruminal lipopolysaccharides on growth and fermentation end products of pure cultured bacteria

Authors: SARMIKASOGLOU, E. - University Of Florida; Ferrell, Jessica; VINYARD, J. - University Of Florida; Flythe, Michael; TUANYOK, A. - University Of Florida; FACIOLA, A. - University Of Florida

Submitted to: Nature Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2022
Publication Date: 9/23/2022
Citation: Sarmikasoglou, E., Ferrell, J.L., Vinyard, J.R., Flythe, M.D., Tuanyok, A., Faciola, A.P. 2022. Effects of ruminal lipopolysaccharides on growth and fermentation end products of pure cultured bacteria. Nature Scientific Reports. 12. Article 15932. https://doi.org/10.1038/s41598-022-20073-2.
DOI: https://doi.org/10.1038/s41598-022-20073-2

Interpretive Summary: Lipopolysaccharide (LPS) is a component of the membranes of certain types of bacteria. The toxicity of LPS to animals is well known, but recent results showed that the LPS made in a ruminant animal was less toxic to that animal than LPS purified from a culture (Escherichia coli or E. coli). The rumen bacteria are very important to the nutrition of ruminant animals, like cows, but it was not clear if rumen bacteria were impacted by the LPS made by other bacteria. These experiments tested three rumen bacteria with E. coli LPS or rumen-native LPS in the laboratory. In general, the growth and metabolism of the bacteria were impacted by the addition of LPS from either source. Some processes, such as the production of lactic acid, were impacted more than others, such as the consumption of lactic acid or ammonia. These results indicate the presence of LPS can impact natural rumen bacteria, even those that do not produce LPS. More research is needed to fully understand the roles of LPS. However, researchers should be aware that the presence of natural or exogenous LPS could impact scientific results.

Technical Abstract: Lipopolysaccharides (LPS) are components of the outer cell membrane of Gram-negative bacteria. Elevated levels of ruminal-LPS have been linked to ruminal acidosis; however, ruminal-LPS structure tends to exhibit lower endotoxicity compared to LPS derived from species like Escherichia coli. Additionally, there is a knowledge gap on the potential effect of ruminal-LPS on ruminal bacteria associated with ruminal acidosis. Therefore, the objective of this study was to evaluate the effects of E. coli-LPS (E. COLI), ruminal-LPS (RUM), and a 1:1 mixture of E. coli and ruminal-LPS (MIX) on the growth and fermentation end products of lactate-producing bacteria (Streptococcus bovis JB1, Selenomonas ruminantium HD4) and lactate-utilizing bacteria (Megasphaera elsdenii T81), as well as assess any potential effect of the combination between them. Ruminal LPS was extracted with phenol-water extraction from the rumen bacterial fraction obtained from ruminal content of a TMR (60:40; forage: concentrate) fed cow. At least three biological replicates were done for each strain. Data were statistically analyzed using Proc MIXED of SAS; in which treatments were analyzed as fixed effect and experimental runs analyzed as random effect. Results indicate that, compared to the control group (LPS-free anaerobic water; CTRL), the maximum specific growth rate of S. bovis JB1 decreased by approximately 32% and 39% when RUM and MIX were dosed, respectively. Compared to E. COLI, the lag phase of S. bovis JB1 was greater when MIX was dosed. In addition, acetate and lactate concentrations in Se. ruminantium HD4 were reduced by approximately 30% and 18%; respectively, in response to MIX dosing. Compared to CTRL, lactate concentration from S. bovis JB1 was reduced approximately by 31% and 22% in response to RUM- and MIX- dosing; respectively. We also found that RUM dosing reduced lactate production, from S. bovis JB1, to a greater extent than E. COLI dosing. Ammonia assimilation was not affected by treatments for all the tested bacterial strains. In summary, our results indicate that RUM decreased the growth and lactate production of lactate-producing bacteria, potentially contributing to the development of acidosis, whereas it did not affect the growth of species that consume lactate.