Successional colonization of perennial ryegrass by rumen bacteria

This study investigated successional colonization of perennial ryegrass (PRG) by the rumen microbiota. PRG grown for 6 weeks in a greenhouse was incubated in sacco in the rumens of three Holstein × Freisian cows over a period of 24 h. PRG incubated within the rumen was subsequently harvested at various time intervals postincubation to assess colonization over time. DGGE-based dendograms revealed the presence of distinct primary (0-2 h) and secondary (4 h onwards) attached bacterial communities. Moving window analysis, band number and Shannon-Wiener diversity indices suggest that after 2 h a proportion of primary colonizing bacteria detach, to be replaced with a population of secondary colonizing bacteria between 2 and 4 h after entry of PRG into the rumen. Sequencing and classification of bands lost and gained between 2 and 4 h showed that the genus Prevotella spp. was potentially more prevalent following 4 h of incubation, and Prevotella spp. 16S rDNA-based QPCR supported this finding somewhat, as 2- to 4-h Prevotella QPCR data were greater but not significantly so. Low-temperature scanning electron microscopy showed that attached bacteria were predominantly enveloped in extracellular polymeric substances. In conclusion, colonization of fresh PRG is biphasic with primary colonization completed within 2 h and secondary colonization commencing after 4 h of attachment in this study.