Successional colonization of perennial ryegrass by rumen bacteria

This study investigated successional colonization of perennial ryegrass (PRG) by the rumen microbiota. PRG grown for 6weeks in a greenhouse was incubated in sacco in the rumens of three Holstein×Freisian cows over a period of 24h. 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 (0-2h) and secondary (4h onwards) attached bacterial communities. Moving window analysis, band number and Shannon-Wiener diversity indices suggest that after 2h a proportion of primary colonizing bacteria detach, to be replaced with a population of secondary colonizing bacteria between 2 and 4h after entry of PRG into the rumen. Sequencing and classification of bands lost and gained between 2 and 4h showed that the genus Prevotella spp. was potentially more prevalent following 4h 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 2h and secondary colonization commencing after 4h of attachment in this study.