Microstructure of anaerobic granules bioaugmented with Desulfitobacterium frappieri PCP-1

Abstract

Oligonucleotide probes were used to study the structure of anaerobic granular biofilm originating from a pentachlorophenol-fed upflow anaerobic sludge bed reactor augmented with Desulfitobacterium frappieri PCP-1, .Fluorescence in situ hybridization demonstrated successful colonization of anaerobic granules by strain PCP-1. Scattered microcolonies of strain PCP-1 were detected on the biofilm surface after 3 weeks of reactor operation, and a dense outer layer of strain PCP-1 was observed after 9 weeks. Hybridization with probes specific for Eubacteria and Archaea probes showed that Eubacteria predominantly colonized the outer layer, while Archaea were observed in the granule interior. Mathematical simulations showed a distribution similar to that observed experimentally when using a specific growth rate of 2.2 day-1 and a low bacterial diffusion of 10-7 dm2 day-1. Also, the simulations showed that strain PCP-1 proliferation in the outer biofilm layer provided excellent protection of the biofilm from pentachlorophenol toxicity.