Submitted to: Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2013
Publication Date: July 8, 2013
Citation: Ziemer, C.J. 2013. Broad diversity and newly cultured bacterial isolates from enrichment of pig feces on complex polysaccharides. Microbial Ecology. 66:448-461. DOI:10.1007/s00248-013-0185-4. Interpretive Summary: Mammals like humans and pigs cannot digest most of the carbohydrates contained in plants because we lack the necssary enzymes. Bacteria that live in the large intestine have the enzymes to utilize plant carbohydrates, and through that supply energy to the host. We isolated bacteria that can degrade these complex carbohydrates from pig feces by feeding them only one carbohydrate, either cellulose or a xylan/pectin 2:1 mix. Over 30% of our isolates have not been previously isolated, with many likely representing new bacterial genera. Most of the isolates were from two main groups, Bacteroides and Clostridia, but there was also a wide range of other bacterial species among our isolates. These isolates represent new opportunities to study the genomic and metabolic capacities of these members of the complex intestinal microbiota that utilize plant carbohydrates. This data will be used by scientists and others studying the interaction of the host and its microbiome, in particular utilization of fiber. The results of this research will be used to improve feed utilization in pigs by tapping into the power of the microbes thus reducing nutrient excretion in the urine and feces.
Technical Abstract: One of the fascinating functions of the mammalian intestinal microbiota is the fermentation of plant cell wall components. We used 8 week continuous culture enrichments of pig feces with cellulose and xylan/pectin to isolated bacteria from this community. A total of 575 bacterial isolates were classified phylogenetically using 16S rRNA gene sequencing. Six phyla were represented in the bacterial isolates: Firmicutes (242), Bacteroidetes (185), Proteobacteria (65), Fusobacteria (55), Actinobacteria (23), and Synergistetes (5). The majority of our bacterial isolates had = 97% similarity to cultured bacteria with sequences in the RDP, but 179 of our isolates represent new species and/or genera. Within the Firmicutes isolates, most were classified in the families of Lachnospiraceae, Enterococcaceae, Staphylococcaceae and Clostridiaceae I. The majority of the Bacteroidetes were most closely related to Bacteroides thetaiotaomicron, B. ovatus and B. xylanisolvens. Many of our Firmicutes and Bacteroidetes isolates were identified as species that possess enzymes which ferment plant cell wall components, the rest likely support these bacteria. The microbial communities that arose in our enrichment cultures had broad bacterial diversity. With over 30% of our isolates were not represented in culture we have new opportunities to study the genomic and metabolic capacities of these members of the complex intestinal microbiota.