Weakening of perennial ryegrass cell wall within the rumen is a rapid process accomplished predominantly by primary attached bacterial biofilm communities dominated by as yet uncultured Lachnospiraceae, Prevotellaceae and unclassified bacteria

Understanding the relationship between ingested plant material and the colonising microbes is essential for developing methodologies of improving ruminant nutrient use efficiency. In this study we investigated temporal niche specialisation of the attached rumen microbiota in relation to the chemical composition of perennial ryegrass (PRG). Denaturing gradient gel electrophoresis revealed the presence of primary (0-2 h) and secondary (4 h onwards) PRG attached bacterial communities. Chemometric analysis of the mid-infrared spectra (FT-IR) of the plant residues also showed significant differences in plant chemical composition between 0-2 h and 4 h onwards, indicative of plant cell wall chemical changes. Scanning electron microscopy (SEM) images of primary attached bacteria following 2 h of incubation illustrated that they predominated within the biofilm phenotype. 16S rDNA 454 pyrosequences obtained from the primary attached bacteria showed that currently uncultured members of the families Lachnospiraceae, Prevotellaceae, and unclassified bacteria dominated. Metagenomic Rapid Annotation using Subsystem Technology (MG-RAST) analysis of 454 metagenomic shotgun sequences showed that functional capacity of the primary attached biofilm communities was predominantly concerned with carbohydrate, capsular and exopolymeric substance metabolism, corroborating suggestive FT-IR and SEM data. This study demonstrates that weakening of PRG cell wall by primary attached biofilm bacteria dominated by currently uncultured of the families Lachnospiraceae, Prevotellaceae, and unclassified bacteria is a rapid process and likely dictates the degree of resultant degradation by secondary colonisers.