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Barr J.J.,San Diego State University | Barr J.J.,University of Queensland | Barr J.J.,Environmental Biotechnology Cooperative Research Center | Dutilh B.E.,University Utrecht | And 11 more authors.
Environmental Microbiology | Year: 2016

Biofilms are ubiquitous in nature, forming diverse adherent microbial communities that perform a plethora of functions. Here we operated two laboratory-scale sequencing batch reactors enriched with CandidatusAccumulibacter phosphatis (Accumulibacter) performing enhanced biological phosphorus removal. Reactors formed two distinct biofilms, one floccular biofilm, consisting of small, loose, microbial aggregates, and one granular biofilm, forming larger, dense, spherical aggregates. Using metagenomic and metaproteomic methods, we investigated the proteomic differences between these two biofilm communities, identifying a total of 2022 unique proteins. To understand biofilm differences, we compared protein abundances that were statistically enriched in both biofilm states. Floccular biofilms were enriched with pathogenic secretion systems suggesting a highly competitive microbial community. Comparatively, granular biofilms revealed a high-stress environment with evidence of nutrient starvation, phage predation pressure, and increased extracellular polymeric substance and cell lysis. Granular biofilms were enriched in outer membrane transport proteins to scavenge the extracellular milieu for amino acids and other metabolites, likely released through cell lysis, to supplement metabolic pathways. This study provides the first detailed proteomic comparison between Accumulibacter-enriched floccular and granular biofilm communities, proposes a conceptual model for the granule biofilm, and offers novel insights into granule biofilm formation and stability. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Barr J.J.,University of Queensland | Barr J.J.,Environmental Biotechnology Cooperative Research Center | Slater F.R.,University of Queensland | Fukushima T.,University of Queensland | And 3 more authors.
FEMS Microbiology Ecology | Year: 2010

Bacteria are known to play important roles in biogeochemical cycles and biotechnology processes, but little is known about the influence of bacteriophage on these processes. A major impediment to the study of host-bacteriophage interactions is that the bacteria and their bacteriophage are often not available in a pure culture. In this study, we detected an unexpected decline in the phosphorus-removal performance of a granular laboratory-scale wastewater treatment reactor. Investigations by FISH, transmission electron microscopy and proteomics led us to hypothesize that a bacteriophage infection of the uncultured Candidatus'Accumulibacter phosphatis' was responsible for the decline in performance. Further experiments demonstrated that the addition of a putative bacteriophage-rich supernatant, obtained from the previous failed reactor to phosphorus-removal reactors, caused a decrease in the abundance of Accumulibacter in both granular and floccular activated sludges. This coincided with increases in bacteriophage-like particles and declining phosphorus-removal performance. The granular sludge did not recover after the attack, but the floccular sludge regained Accumulibacter numbers and phosphorus-removal performance. These findings suggest that bacteriophage may play a significant role in determining the structure and function of bacterial communities in activated sludges. © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Barr J.J.,University of Queensland | Barr J.J.,Environmental Biotechnology Cooperative Research Center | Cook A.E.,University of Queensland | Bond P.L.,University of Queensland | Bond P.L.,Environmental Biotechnology Cooperative Research Center
Applied and Environmental Microbiology | Year: 2010

Granular sludge is a novel alternative for the treatment of wastewater and offers numerous operational and economic advantages over conventional floccular-sludge systems. The majority of research on granular sludge has focused on optimization of engineering aspects relating to reactor operation with little emphasis on the fundamental microbiology. In this study, we hypothesize two novel mechanisms for granule formation as observed in three laboratory scale sequencing batch reactors operating for biological phosphorus removal and treating two different types of wastewater. During the initial stages of granulation, two distinct granule types (white and yellow) were distinguished within the mixed microbial population. White granules appeared as compact, smooth, dense aggregates dominated by 97.5% "Candidatus Accumulibacter phosphatis," and yellow granules appeared as loose, rough, irregular aggregates with a mixed microbial population of 12.3% "Candidatus Accumulibacter phosphatis" and 57.9% "Candidatus Competibacter phosphatis," among other bacteria. Microscopy showed white granules as homogeneous microbial aggregates and yellow granules as segregated, microcolony-like aggregates, with phylogenetic analysis suggesting that the granule types are likely not a result of strain-associated differences. The microbial community composition and arrangement suggest different formation mechanisms occur for each granule type. White granules are hypothesized to form by outgrowth from a single microcolony into a granule dominated by one bacterial type, while yellow granules are hypothesized to form via multiple microcolony aggregation into a microcolony-segregated granule with a mixed microbial population. Further understanding and application of these mechanisms and the associated microbial ecology may provide conceptual information benefiting start-up procedures for full-scale granular-sludge reactors. Copyright © 2010, American Society for Microbiology.

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