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Fibrolytic bacteria isolated from the rumen of North American moose (Alces alces)
Background
Fibrolytic bacteria were isolated from the rumen of North American moose (Alces alces), which eat a high-fiber diet of browse. It was hypothesized that fibrolytic bacteria isolated from the moose rumen could be candidates to improve fiber degradation and animal production. In vivo, an increase in cellulose degradation can increase weight gain, milk, and wool production. In industrial systems, digestion by microorganisms or enzymes can increase forage digestibility for livestock, improve ensiling, or provide glucose from biomass for bioethanol-production.
Materials
Thirty-eight isolates were cultured from rumen digesta samples collected in October 2010 in Vermont, USA. Using Sanger sequencing of the 16S rRNA gene, culturing techniques, and optical density, isolates were identified and screened for biochemical properties important to plant carbohydrate degradation.
Results
Isolates had the following percent identity to known sequences in NCBI: Bacillus licheniformis, 98 - 100% (n=22); Enterococcus faecalis, 95 – 99% (n=6); Staphylococcus saprophyticus, 99 - 100% (n=4), B. chandrigarhensis, 98% (n=1); B. firmus, 98% (n=1); B. flexus, 100% (n=1); B. niabensis, 95% (n=1); Enterobacter ludwigii, 99% (n=1), and Paenibacillus woosongensis, 98% (n=1). Using a 97% identity cutoff for near full-length 16S rRNA gene sequences, there are 22 novel strains of B. licheniformis; one novel strain each of B. chandrigarhensis, B. firmus, and B. flexus; one novel species of Bacillus; three novel strains of Enterococcus faecalis, two novel Enterococcus sp., one novel strain of Enterobacter ludwigii; one novel strain of P. woosongensis; and 4 novel strains of S. saprophyticus,
Isolates were able to digest cellulose (n=38), cellobiose (n=34), xylan (n=31), starch (n=25), carboxymethylcellulose (n=24), and lignin (n=20) under minimal nutritional conditions. Fifteen isolates were able to digest all six carbohydrates tested. Isolates were able to tolerate up to 10% (n=17) salinity, between pH 4.0 (n=34) and pH 10.0 (n=33), and between 20°C (n=35) and 55°C (n=36). Isolates were tolerant to sodium azide (n=37), could reduce potassium tellurite (n=3), metabolize mannitol (n=31), produce indole from tryptophan (n=7), and all isolates could use citrate or proprionate as a sole carbon source, as well as ammonium ions for nitrogen.
Conclusions
New, highly efficient species or strains of fibrolytic bacteria could be utilized to improve fiber degradation in ruminants or in industrial applications. The isolates tested showed a wide range of carbohydrate digestion and were able to tolerate adverse growth conditions, making them good candidates for improved fiber digestion in vivo and suitable for high temperature industrial fiber digestion.
Keywords: fibrolytic, bacteria