207 Polyclonal Antibodies Inhibit Growth of Key Cellulolytic Rumen Bacterial Species

Abstract

The objective was to develop efficacious polyclonal antibodies to inhibit growth of targeted cellulolytic rumen bacterial species. Many rumen microorganisms have overlapping functions, so inhibiting the activity of targeted bacterial species may help elucidate their dynamic contributions to rumen fermentation. Egg-derived, polyclonal antibodies were developed against whole-cell cultures of Ruminococcus albus 7 (anti-RA7), Ruminococcus albus 8 (anti-RA8), and Fibrobacter succinogenes S85 (anti-FS85). Antibodies were added to a cellobiose-containing growth medium of pure cultures of the 3 targeted species. Antibody efficacy was determined via an inoculation time (0 and 4 h) and dose response. Antibody doses included: 0 (CON), 0.013 (LO), 1.3 (MD), 13 (HI) mg antibody per 10 mL of medium. Each targeted species inoculated at 0 h with HI of their respective antibody had decreased (P < 0.01) final optical density and total volatile fatty acid (VFA) concentration after a 52-h growth period when compared with CON or LO. Live/dead stains of R. albus 7 and F. succinogenes S85 dosed at 0 h with HI of their respective antibody indicated a decrease (≥ 96%; P < 0.05) of live bacterial cells during mid-log phase compared with CON or LO. Addition of HI of anti-FS85 at 0 h in F. succinogenes S85 cultures reduced (P < 0.01) total substrate disappearance over 52 h by at least 48% when compared with CON or LO. Cross-reactivity was assessed by adding HI at 0 h to non-targeted bacterial species. Addition of anti-RA8 or anti-RA7 to F. succinogenes S85 cultures did not affect (P ≥ 0.45) total VFA accumulation after 52 h incubation. Overall, polyclonal antibodies were more efficacious at inhibiting growth of targeted cellulolytic bacteria than non-targeted bacteria. Specific polyclonal antibodies can be used to further characterize functional contributions of bacterial species to rumen fermentation.