Submitted to: FEMS Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2013
Publication Date: N/A
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 both human and pig feces. Over 30% of our isolates have not been previously isolated. Most of the isolates from both humans and pigs fell into the genetic grouping of Clostridia. There were only a few groups where the human and pig isolates were very similar. The isolates will increase our understanding of the complex metabolic pathways that exist in intestinal micobial communities.
Technical Abstract: Microbial fermentation of plant cell wall components to short chain fatty acids in the large intestine provides energy to both humans and pigs. To better understand plant cell wall fermentation in the pig and human intestine, we isolated cellulose, xylan, and pectin fermenting bacteria from pig and human feces. In pig and human feces, two different enrichment methods were used: 1) rapid flow isolations utilized a flow rate of 25%/h with immobilized substrate (24 h), and 2) substrate depleted isolations utilized nutrient depleted medium with a single carbohydrate (between 72 and 120 h). A total of 391 and 135 isolates were recovered using both methods, from pig and human fecal inoculations, respectively. Of those, 84 different sequence identities were present in pigs and 58 in humans. Bacteria in the Firmicutes phyla dominated isolates from both pig (72.6%) and human (32.5%) feces. The other phyla isolates were from included Bacteroidetes (4.8% and 15.5%), Proteobacteria (16.7% and 29.3%), and Actinobacteria (4.8% and 15.5%) (pig and human isolates, respectively); Fusobacteria were also isolated from pigs at 1.2% of total pig isolates. Isolates with low similarity to other cultured bacteria were identified from both hosts, 27 in pig (32.1%) and 30 in human (51.7%) isolates. Comparisons of isolates found only a few groupings with phylogenetic similarity among pig and human isolates. These bacterial pure cultures will be used to increase our understanding of the high level of species and strain diversity in intestinal environments. As more data is compiled by metagenomic surveys of gastrointestinal environments, it will become increasingly important to have isolates which can help determine which organisms are important to the vast metabolic capacity of intestinal microbial communities.