Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia

ABSTRACT Tropical forest soils decompose litter rapidly with frequent episodes of anoxic conditions, making it likely that bacteria using alternate terminal electron acceptors (TEAs) play a large role in decomposition. This makes these soils useful templates for improving biofuel production. To inve...

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Autores principales:	Kristen M. DeAngelis, Julian L. Fortney, Sharon Borglin, Whendee L. Silver, Blake A. Simmons, Terry C. Hazen
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2012
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/02b7fcd889074a1e88924736f26403a7
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spelling	oai:doaj.org-article:02b7fcd889074a1e88924736f26403a72021-11-15T15:39:02ZAnaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia10.1128/mBio.00249-112150-7511https://doaj.org/article/02b7fcd889074a1e88924736f26403a72012-03-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00249-11https://doaj.org/toc/2150-7511ABSTRACT Tropical forest soils decompose litter rapidly with frequent episodes of anoxic conditions, making it likely that bacteria using alternate terminal electron acceptors (TEAs) play a large role in decomposition. This makes these soils useful templates for improving biofuel production. To investigate how TEAs affect decomposition, we cultivated feedstock-adapted consortia (FACs) derived from two tropical forest soils collected from the ends of a rainfall gradient: organic matter-rich tropical cloud forest (CF) soils, which experience sustained low redox, and iron-rich tropical rain forest (RF) soils, which experience rapidly fluctuating redox. Communities were anaerobically passed through three transfers of 10 weeks each with switchgrass as a sole carbon (C) source; FACs were then amended with nitrate, sulfate, or iron oxide. C mineralization and cellulase activities were higher in CF-FACs than in RF-FACs. Pyrosequencing of the small-subunit rRNA revealed members of the Firmicutes, Bacteroidetes, and Alphaproteobacteria as dominant. RF- and CF-FAC communities were not different in microbial diversity or biomass. The RF-FACs, derived from fluctuating redox soils, were the most responsive to the addition of TEAs, while the CF-FACs were overall more efficient and productive, both on a per-gram switchgrass and a per-cell biomass basis. These results suggest that decomposing microbial communities in fluctuating redox environments are adapted to the presence of a diversity of TEAs and ready to take advantage of them. More importantly, these data highlight the role of local environmental conditions in shaping microbial community function that may be separate from phylogenetic structure. IMPORTANCE After multiple transfers, we established microbial consortia derived from two tropical forest soils with different native redox conditions. Communities derived from the rapidly fluctuating redox environment maintained a capacity to use added terminal electron acceptors (TEAs) after multiple transfers, though they were not present during the enrichment. Communities derived from lower-redox soils were not responsive to TEA addition but were much more efficient at switchgrass decomposition. Though the communities were different, diversity was not, and both were dominated by many of the same species of clostridia. This reflects the inadequacy of rRNA for determining the function of microbial communities, in this case the retained ability to utilize TEAs that were not part of the selective growth conditions. More importantly, this suggests that microbial community function is shaped by life history, where environmental factors produce heritable traits through natural selection over time, creating variation in the community, a phenomenon not well documented for microbes.Kristen M. DeAngelisJulian L. FortneySharon BorglinWhendee L. SilverBlake A. SimmonsTerry C. HazenAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 3, Iss 1 (2012)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Kristen M. DeAngelis Julian L. Fortney Sharon Borglin Whendee L. Silver Blake A. Simmons Terry C. Hazen Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
description	ABSTRACT Tropical forest soils decompose litter rapidly with frequent episodes of anoxic conditions, making it likely that bacteria using alternate terminal electron acceptors (TEAs) play a large role in decomposition. This makes these soils useful templates for improving biofuel production. To investigate how TEAs affect decomposition, we cultivated feedstock-adapted consortia (FACs) derived from two tropical forest soils collected from the ends of a rainfall gradient: organic matter-rich tropical cloud forest (CF) soils, which experience sustained low redox, and iron-rich tropical rain forest (RF) soils, which experience rapidly fluctuating redox. Communities were anaerobically passed through three transfers of 10 weeks each with switchgrass as a sole carbon (C) source; FACs were then amended with nitrate, sulfate, or iron oxide. C mineralization and cellulase activities were higher in CF-FACs than in RF-FACs. Pyrosequencing of the small-subunit rRNA revealed members of the Firmicutes, Bacteroidetes, and Alphaproteobacteria as dominant. RF- and CF-FAC communities were not different in microbial diversity or biomass. The RF-FACs, derived from fluctuating redox soils, were the most responsive to the addition of TEAs, while the CF-FACs were overall more efficient and productive, both on a per-gram switchgrass and a per-cell biomass basis. These results suggest that decomposing microbial communities in fluctuating redox environments are adapted to the presence of a diversity of TEAs and ready to take advantage of them. More importantly, these data highlight the role of local environmental conditions in shaping microbial community function that may be separate from phylogenetic structure. IMPORTANCE After multiple transfers, we established microbial consortia derived from two tropical forest soils with different native redox conditions. Communities derived from the rapidly fluctuating redox environment maintained a capacity to use added terminal electron acceptors (TEAs) after multiple transfers, though they were not present during the enrichment. Communities derived from lower-redox soils were not responsive to TEA addition but were much more efficient at switchgrass decomposition. Though the communities were different, diversity was not, and both were dominated by many of the same species of clostridia. This reflects the inadequacy of rRNA for determining the function of microbial communities, in this case the retained ability to utilize TEAs that were not part of the selective growth conditions. More importantly, this suggests that microbial community function is shaped by life history, where environmental factors produce heritable traits through natural selection over time, creating variation in the community, a phenomenon not well documented for microbes.
format	article
author	Kristen M. DeAngelis Julian L. Fortney Sharon Borglin Whendee L. Silver Blake A. Simmons Terry C. Hazen
author_facet	Kristen M. DeAngelis Julian L. Fortney Sharon Borglin Whendee L. Silver Blake A. Simmons Terry C. Hazen
author_sort	Kristen M. DeAngelis
title	Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
title_short	Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
title_full	Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
title_fullStr	Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
title_full_unstemmed	Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
title_sort	anaerobic decomposition of switchgrass by tropical soil-derived feedstock-adapted consortia
publisher	American Society for Microbiology
publishDate	2012
url	https://doaj.org/article/02b7fcd889074a1e88924736f26403a7
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Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia

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