Effects of different pH on number and community structure of rumen bacteria
[Objective]The aim of this experiment is to investigate the changes in the number of rumen acidosis related bacteria and the structure of rumen bacterial communities under different pH in the rumen.[Method]Five Holstein cows at dry milk stage were selected as rumen fluid donors,and the pH of rumen fluid was adjusted to 6.5,5.8,5.5,5.2 and 5.0,respectively.After incubation for three hours,qPCR technology was used to determine the number of bacteria associated with rumen acidosis,and 16S rDNA high-throughput se-quencing technology was used to study changes in the structure of rumen microbiota.[Result](1)Ruminal pH did not affect the relative number of Ruminococcus albus(P>0.05),it significantly affected the relative num-bers of lactic acid producing bacteria and lactic acid utilizing bacteria(P<0.05).The relative number of Strepto-coccus bovis increased with the decrease of pH,and it was significantly higher at pH 5.0 than other groups(P<0.05);The relative number of Megaphagea elsdenii,Selenomonas ruminantium,and Lactobacillus species showed a trend of first increasing and then decreasing with the decrease of pH,which reached a maximum val-ues at pH 5.5 or 5.2,respectively(P<0.05);(2)The results of α diversity analysis of rumen bacterial communi-ties showed that the abundance and diversity of rumen bacteria had a trend of first increasing and then decreas-ing with the decrease of rumen pH,The Chao1 index at pH 5.5,and the Observed Specifications and Shannon indices at pH 5.2 were the highest ones in all groups(P<0.05).The results of β diversity analysis of rumen bac-terial communities showed that there were significant differences in the microbial community composition be-tween the pH 6.5,pH 5.8 treatment groups and the pH 5.2,pH 5.0 ones.The distance of pH 5.5 treatment group samples was far away from the other four groups,which meant its microbial community composition was different from the other four groups;(3)In terms of microbial community composition,the abundance of the main bacteria at phylum and genus levels in the rumen also varied with the decrease of rumen pH.There was a significant difference in the microbial community structure between the pH 5.2,5.0 treatment groups and the pH 6.5,5.8 treatment groups(P<0.05).There was no significant difference in the composition between pH 6.5 group and pH 5.8 group(P>0.05),in which only the difference of Prevotellaceae UCG-003 and Succinivibrio-naceae UCG 002 were found;The microbial community structure of the pH 5.0 treatment group and the pH 5.2 treatment group was relatively identical(P>0.05),and there were differences only in Spirochaete,Actinomyce-tota at phylum level,and in Ruminococcus and Succiniaclasticum at level of fungi(P<0.05);the microbial com-munity composition of the pH 5.5 treatment group showed significant differences compared with the other four groups(P<0.05).[Conclusion]In summary,change in environmental pH was a serious disturbance to rumen bacteria,which resulted in significant changes in the relative numbers of lactic acid producing and lactic acid utilizing bacteria in the rumen.The number,richness,and diversity of rumen bacteria also showed a trend of first increasing and then decreasing with the decrease of rumen pH,which conforms to the"Intermediate Dis-turbance Hypothesis".
low pHruminal acidosisrumen bacterianumber of bacteriacommunity structure"Intermediate disturbance hypothesis"
万方数据
维普
