Submitted to: The ISME Journal: Multidisciplinary Journal of Microbial Ecology
Publication Type: Abstract Only
Publication Acceptance Date: May 2, 2010
Publication Date: August 27, 2010
Citation: Ziemer, C.J. 2010. Firmicutes and Bacteroidetes Dominate Fiber Degrading Bacteria Isolated from Pig Feces [abstract]. The ISME Journal: Multidisciplinary Journal of Microbial Ecology, August 22-27, 2010, Seattle, WA. 2010 CD-ROM. Technical Abstract: Addition of fibrous feedstuffs to pig diets improves feed efficiency due to decreased feed intake without commensurate decrease in weight gain; due to utilization of short chain fatty acids (SCFA) for energy. Bacterially produced SCFA can contribute 10 to 30% of a pig’s metabolic energy. Investigation of intestinal bacteria that degrade fiber and produce SCFA can be applied to improve feed utilization and animal growth efficiencies. Continuous culture fermentations (n=12; 2/pig, 6 pigs) of pig feces fed cellulose (6 g/d) or xylan-pectin (4+2 g/d) as sole carbohydrate were used to enrich fiber utilizing bacteria. Fermenters (700 ml, 38ºC, pH 6.0-7.5, 0.03%/h turnover, continuous agitation and nitrogen inflow) were inoculated with 350 ml of 1 in 10 (w/w) fecal slurry. After feeding 3 g of substrate, fermenter contents were batch cultured overnight before starting inflow of carbohydrate-free nutrient medium. Carbohydrates were fed twice daily for 8 weeks; contents were sampled for bacterial isolations after 4, 6 or 8 wk. Replicate plating on single carbohydrate agars (including cellulose and xylan) was used; individual colonies were selected and bacterial isolates obtained. A total of 940 isolates were recovered and 16S rRNA genes sequenced. Sequences were identified using Ribosomal Database Project and identical sequences from the same pig were eliminated, resulting in 360 individual isolates. The dominant bacterial genera of isolates were Bacteroides (23%) and Clostridium (15%); both Firmicutes bacilli and other Firmicutes were each 19%, with Bacteroidetes only 2% of total isolates. Over 46% of isolates were less than 97% similar to cultured organisms. There was a great deal of strain diversity within species. These isolates will be used to increase understanding of energy supplied to pigs through bacterial production of SCFA and to investigate strain diversity within bacterial species.