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Effects of the Antimicrobial Tylosin on the Microbial Community Structure of an Anaerobic Sequencing Batch Reactor

Effects of the Antimicrobial Tylosin on the Microbial Community Structure of an Anaerobic Sequencing Batch Reactor

Shimada, T., X. Li, J. Zilles, E. Morgenroth, L. Raskin
Published In: 
Biotechnology and Bioengineering,  
January 2011

The effects of the antimicrobial tylosin on a methanogenic microbial community were studied in a glucose-fed laboratory-scale anaerobic sequencing batch reactor (ASBR) exposed to stepwise increases of tylosin (0, 1.67, and 167 mg/L). The microbial community structure was determined using quantitative fluorescence in situ hybridization (FISH) and phylogenetic analyses of bacterial 16S ribosomal RNA (rRNA) gene clone libraries of biomass samples. During the periods without tylosin addition and with an influent tylosin concentration of 1.67 mg/L, 16S rRNA gene sequences related to Syntrophobacter were detected and the relative abundance of Methanosaeta species was high. During the highest tylosin dose of 167 mg/L, 16S rRNA gene sequences related to Syntrophobacter species were not detected and the relative abundance of Methanosaeta decreased considerably. Throughout the experimental period, Propionibacteriaceae and high GC Gram positive bacteria were present, based on 16S rRNA gene sequences and FISH analyses, respectively. The accumulation of propionate and subsequent reactor failure after long-term exposure to tylosin are attributed to the direct inhibition of propionate-oxidizing syntrophic bacteria closely related to Syntrophobacter and the indirect inhibition of Methanosaeta by high propionate concentrations and low pH.

Figure 1
Modeled (–) and measured bacteria (■), archaea (▲), high GC bacteria (●), and aceticlastic methanogens (Methanosarcina + Methanosaeta, □) relative abundance in the ASBR throughout the experimental period. FISH data was normalized to total hybridization (sum of Bact0338 and Arch0915). Numbers above the figure indicate influent tylosin concentrations.

Shimada, T., X. Li, J. Zilles, E. Morgenroth, L. Raskin. “Effects of the Antimicrobial Tylosin on the Microbial Community Structure of an Anaerobic Sequencing Batch Reactor.” Biotechnology & Bioengineering 108(2):296-305, 2011.