Layered Structure of Bacterial and Archaeal Communities and Their In Situ Activities in Anaerobic Granules

Abstract

The microbial community structure and spatial distribution of microorganisms and their in situ activities in anaerobic granules were investigated by 16S rRNA gene-based molecular techniques and microsensors for CH 4 , H 2 , pH, and the oxidation-reduction potential (ORP). The 16S rRNA gene-cloning analysis revealed that the clones related to the phyla Alphaproteobacteria (detection frequency, 51%), Firmicutes (20%), Chloroflexi (9%), and Betaproteobacteria (8%) dominated the bacterial clone library, and the predominant clones in the archaeal clone library were affiliated with Methanosaeta (73%). In situ hybridization with oligonucleotide probes at the phylum level revealed that these microorganisms were numerically abundant in the granule. A layered structure of microorganisms was found in the granule, where Chloroflexi and Betaproteobacteria were present in the outer shell of the granule, Firmicutes were found in the middle layer, and aceticlastic Archaea were restricted to the inner layer. Microsensor measurements for CH 4 , H 2 , pH, and ORP revealed that acid and H 2 production occurred in the upper part of the granule, below which H 2 consumption and CH 4 production were detected. Direct comparison of the in situ activity distribution with the spatial distribution of the microorganisms implied that Chloroflexi contributed to the degradation of complex organic compounds in the outermost layer, H 2 was produced mainly by Firmicutes in the middle layer, and Methanosaeta produced CH 4 in the inner layer. We determined the effective diffusion coefficient for H 2 in the anaerobic granules to be 2.66 ؋ 10 ؊5 cm 2 s ؊1 , which was 57% in water.Upflow anaerobic sludge blanket (UASB) reactors are commonly used in the treatment of high-strength municipal and industrial wastewaters. Their design permits the retention of a greater amount of active biomass (known as granules) than other anaerobic reactors. These anaerobic granules harbor several metabolic groups of microorganisms, including hydrolytic, fermentative, syntrophic, and methanogenic microorganisms, involved in the anaerobic degradation of complex organic compounds. These different trophic groups of anaerobes closely and coordinately interact with one another within the granules and convert complex organic compounds in wastewaters into methane (CH 4 ) and carbon dioxide (CO 2 ). The microbial communities of anaerobic granules used to treat different wastewaters have been investigated by culture-independent 16S rRNA gene-based molecular analyses (14, 22, 36), which allow one to obtain more-complete inventories of microorganisms in anaerobic granules. The results have shown that anaerobic granules consist of a phylogenetically diverse group of microorganisms; however, the majority of them have not yet been cultivated (14,22,36).The application of fluorescence in situ hybridization (FISH) with specific oligonucleotide probes allows us to further determine the abundances and in situ spatial distributions of specific phylogenetic groups in anaerobic granules (14,20...

Microbial community changes in methanogenic granules during the transition from mesophilic to thermophilic conditions

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Effect of feeding regimens on polyhydroxybutyrate production from food wastes by Cupriavidus necator

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Comparison of different procedures to stabilize biogas formation after process failure in a thermophilic waste digestion system: Influence of aggregate formation on process stability

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