Ruminal Lipopolysaccharides Analysis: Uncharted Waters with Promising Signs

Abstract

The objective of this review is to present the need for the development of a comprehensive ruminal lipopolysaccharide (LPS) extraction, purification and analysis protocol and state hypotheses that could contribute to planning novel strategies against ruminal acidosis. Lipopolysaccharide is an immunostimulatory molecule of Gram-negative bacterial outer membranes and has been reported to contribute to ruminal acidosis in cattle. Bacterial death and lysis are normal processes, and thus LPS is normally present in ruminal fluid. However, ruminal LPS concentration is much greater during subacute ruminal acidosis (SARA). Contrary to the widely known LPSs, ruminal LPS seems to be composed of a variety of LPS chemotypes that may interact with each other resulting in an LPS "mixture". Hypotheses regarding the influence of each specific ruminal bacterial specie to innate immunity during SARA, and the representativeness of the exclusive use of the Escherichia coli LPS to rumen epithelial tissue challenges, could expand our knowledge regarding SARA. In addition, possible correlation between the monomeric Toll-like Receptor 4 (TRL4) and the antagonistic penta-acylated lipid A of LPS could contribute to novel strategies to tackle this nutrition disorder.

Keywords: LBP; Prevotella; extraction protocol; ruminal LPS; single molecule localization microscopy.

Figure 1

Diagram of the general structure of lipopolysaccharides of Gram-negative bacteria. Lipopolysaccharides of Gram-negative bacteria consist of three main subunits (from bottom to top): lipid A, the core region, and the O-antigen. Lipid A and the core (Adapted from Steimle, A. et al. [66]).

Figure 2

Structures of Escherichia coli (strong agonistic) and Helicobacter pylori (antagonistic). Escherichia coli Lipid A consists of six acyl chains (hexa-acylated) and two immunogenic phosphate groups (Light red); in contrast, H. pylori Lipid A is composed of four acyl chains (tetra-acylated) and one immunogenic phosphate group (light red). Structural differences of the acyl chains and modifications in phosphate groups significantly alter the immunogenic activity of Lipid A molecules (Adapted from Steimle, A. et al. [66]).