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Co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III)-reducing enrichment culture.

Zheng S, Zhang H, Li Y, Zhang H, Wang O, Zhang J, Liu F - Front Microbiol (2015)

Bottom Line: First, iron (III) reducers including Geobacteraceae were successfully enriched by 3-months successive culture on amorphous Fe(III) oxides as electron acceptor and acetate as electron donor.Remarkably, aggregates were successively formed in the enrichments after three transfers.The results revealed by RNA-based analysis demonstrate that the co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III)-reducing enrichment culture.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences Yantai, China ; Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences Yantai, China.

ABSTRACT
Methanosaeta harundinacea and Methanosarcina barkeri, known as classic acetoclastic methanogens, are capable of directly accepting electrons from Geobacter metallireducens for the reduction of carbon dioxide to methane, having been revealed as direct interspecies electron transfer (DIET) in the laboratory co-cultures. However, whether their co-occurrences are ubiquitous in the iron (III)-reducing environments and the other species of acetoclastic methanogens such as Methanosarcina mazei are capable of DIET are still unknown. Instead of initiating the co-cultures with pure cultures, two-step cultivation was employed to selectively enrich iron (III)-reducing microorganisms in a coastal gold mining river, Jiehe River, with rich iron content in the sediments. First, iron (III) reducers including Geobacteraceae were successfully enriched by 3-months successive culture on amorphous Fe(III) oxides as electron acceptor and acetate as electron donor. High-throughput Illumina sequencing, terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures actively contained the bacteria belong to Geobacteraceae and Bacilli, exclusively dominated by the archaea belong to Methanosarcinaceae. Second, the enrichment cultures including methanogens and Geobacteraceae were transferred with ethanol as alternative electron donor. Remarkably, aggregates were successively formed in the enrichments after three transfers. The results revealed by RNA-based analysis demonstrate that the co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III)-reducing enrichment culture. Furthermore, the aggregates, as close physical contact, formed in the enrichment culture, indicate that DIET could be a possible option for interspecies electron transfer in the aggregates.

No MeSH data available.


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Fe(III) reduction, methane production and acetate or ethanol consumption of enrichment cultures. Time-courses of Fe(II) production (A), methane production (B) and acetate consumption (C) in enrichment cultures by 10% (w/v, wet) inoculation from fresh water enrichment culture of in situ sediments with 33 mmol L−1 of acetate in the absence or presence of 100 mmol L−1 of Fe(III) oxides. Time-courses of Fe(II) production (D), methane production (E), ethanol consumption (F) and acetate production/consumption (G) in enrichment cultures by 10% (v/v) inoculation from enrichment culture of three transfers of in situ sediments in DSM 120 medium with 30 mmol L−1 of ethanol in the absence or presence of 100 mmol L−1 of Fe(III) oxides. (H) Image was presented aggregates after enrichment culture in DSM 120 medium with ethanol or acetate as a substrate in the absence of Fe(III) oxides. Sterile sediment sample (SJh) with Fe(III) oxides treatment was used as the negative control. Data was presented in triplicate and standard deviation was shown for each data point. Jh2 was selected as the representative sample named as Jh.
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Figure 3: Fe(III) reduction, methane production and acetate or ethanol consumption of enrichment cultures. Time-courses of Fe(II) production (A), methane production (B) and acetate consumption (C) in enrichment cultures by 10% (w/v, wet) inoculation from fresh water enrichment culture of in situ sediments with 33 mmol L−1 of acetate in the absence or presence of 100 mmol L−1 of Fe(III) oxides. Time-courses of Fe(II) production (D), methane production (E), ethanol consumption (F) and acetate production/consumption (G) in enrichment cultures by 10% (v/v) inoculation from enrichment culture of three transfers of in situ sediments in DSM 120 medium with 30 mmol L−1 of ethanol in the absence or presence of 100 mmol L−1 of Fe(III) oxides. (H) Image was presented aggregates after enrichment culture in DSM 120 medium with ethanol or acetate as a substrate in the absence of Fe(III) oxides. Sterile sediment sample (SJh) with Fe(III) oxides treatment was used as the negative control. Data was presented in triplicate and standard deviation was shown for each data point. Jh2 was selected as the representative sample named as Jh.

Mentions: In order to investigate whether DIET is involved between more iron(III)-reducing microorganisms and methanogens, syntrophic co-cultures systems need to be set up. Instead of initiating the co-cultures with pure cultures, two-step cultivation was employed to selectively enrich iron (III)-reducing microorganisms and methanogens from the sediments. First, iron (III) reducers were enriched by 3-months successive culture on amorphous Fe(III) oxides as electron acceptor and acetate as electron donor. Second, the enrichment cultures were transferred with ethanol as alternative electron donor. During the first step, ferrous iron was produced during the enrichment with or without Fe(III) oxides treatment. Under the Fe(III) oxides-amended conditions with acetate as electron donor, 1.98 ± 0.059 mmol of ferrous iron was produced at day 30 (Figure 3A). When the enrichment culture was transferred for three times, ethanol was used as electron donor. As a result, 5.37 ± 0.086 mmol of ferrous iron was produced at day 20 (Figure 3D). However, when acetate was used as the electron donor without Fe(III) oxides treatment, only 0.66 ± 0.018 mmol of ferrous iron was produced at day 30 (Figure 3A), while the amount of ferrous iron was below 0.012 mmol in the culture with ethanol as the electron donor after three transfers (Figure 3D). Thus, part of the ferric iron in acetate or ethanol-fed cultures, mostly consisting of the supplemented Fe(III) oxides, was reduced to ferrous iron. As a control to show this reduction is a biogeochemical process, autoclaved sediments did not produce any more ferrous iron (Figures 3A,D).


Co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III)-reducing enrichment culture.

Zheng S, Zhang H, Li Y, Zhang H, Wang O, Zhang J, Liu F - Front Microbiol (2015)

Fe(III) reduction, methane production and acetate or ethanol consumption of enrichment cultures. Time-courses of Fe(II) production (A), methane production (B) and acetate consumption (C) in enrichment cultures by 10% (w/v, wet) inoculation from fresh water enrichment culture of in situ sediments with 33 mmol L−1 of acetate in the absence or presence of 100 mmol L−1 of Fe(III) oxides. Time-courses of Fe(II) production (D), methane production (E), ethanol consumption (F) and acetate production/consumption (G) in enrichment cultures by 10% (v/v) inoculation from enrichment culture of three transfers of in situ sediments in DSM 120 medium with 30 mmol L−1 of ethanol in the absence or presence of 100 mmol L−1 of Fe(III) oxides. (H) Image was presented aggregates after enrichment culture in DSM 120 medium with ethanol or acetate as a substrate in the absence of Fe(III) oxides. Sterile sediment sample (SJh) with Fe(III) oxides treatment was used as the negative control. Data was presented in triplicate and standard deviation was shown for each data point. Jh2 was selected as the representative sample named as Jh.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4562271&req=5

Figure 3: Fe(III) reduction, methane production and acetate or ethanol consumption of enrichment cultures. Time-courses of Fe(II) production (A), methane production (B) and acetate consumption (C) in enrichment cultures by 10% (w/v, wet) inoculation from fresh water enrichment culture of in situ sediments with 33 mmol L−1 of acetate in the absence or presence of 100 mmol L−1 of Fe(III) oxides. Time-courses of Fe(II) production (D), methane production (E), ethanol consumption (F) and acetate production/consumption (G) in enrichment cultures by 10% (v/v) inoculation from enrichment culture of three transfers of in situ sediments in DSM 120 medium with 30 mmol L−1 of ethanol in the absence or presence of 100 mmol L−1 of Fe(III) oxides. (H) Image was presented aggregates after enrichment culture in DSM 120 medium with ethanol or acetate as a substrate in the absence of Fe(III) oxides. Sterile sediment sample (SJh) with Fe(III) oxides treatment was used as the negative control. Data was presented in triplicate and standard deviation was shown for each data point. Jh2 was selected as the representative sample named as Jh.
Mentions: In order to investigate whether DIET is involved between more iron(III)-reducing microorganisms and methanogens, syntrophic co-cultures systems need to be set up. Instead of initiating the co-cultures with pure cultures, two-step cultivation was employed to selectively enrich iron (III)-reducing microorganisms and methanogens from the sediments. First, iron (III) reducers were enriched by 3-months successive culture on amorphous Fe(III) oxides as electron acceptor and acetate as electron donor. Second, the enrichment cultures were transferred with ethanol as alternative electron donor. During the first step, ferrous iron was produced during the enrichment with or without Fe(III) oxides treatment. Under the Fe(III) oxides-amended conditions with acetate as electron donor, 1.98 ± 0.059 mmol of ferrous iron was produced at day 30 (Figure 3A). When the enrichment culture was transferred for three times, ethanol was used as electron donor. As a result, 5.37 ± 0.086 mmol of ferrous iron was produced at day 20 (Figure 3D). However, when acetate was used as the electron donor without Fe(III) oxides treatment, only 0.66 ± 0.018 mmol of ferrous iron was produced at day 30 (Figure 3A), while the amount of ferrous iron was below 0.012 mmol in the culture with ethanol as the electron donor after three transfers (Figure 3D). Thus, part of the ferric iron in acetate or ethanol-fed cultures, mostly consisting of the supplemented Fe(III) oxides, was reduced to ferrous iron. As a control to show this reduction is a biogeochemical process, autoclaved sediments did not produce any more ferrous iron (Figures 3A,D).

Bottom Line: First, iron (III) reducers including Geobacteraceae were successfully enriched by 3-months successive culture on amorphous Fe(III) oxides as electron acceptor and acetate as electron donor.Remarkably, aggregates were successively formed in the enrichments after three transfers.The results revealed by RNA-based analysis demonstrate that the co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III)-reducing enrichment culture.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences Yantai, China ; Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences Yantai, China.

ABSTRACT
Methanosaeta harundinacea and Methanosarcina barkeri, known as classic acetoclastic methanogens, are capable of directly accepting electrons from Geobacter metallireducens for the reduction of carbon dioxide to methane, having been revealed as direct interspecies electron transfer (DIET) in the laboratory co-cultures. However, whether their co-occurrences are ubiquitous in the iron (III)-reducing environments and the other species of acetoclastic methanogens such as Methanosarcina mazei are capable of DIET are still unknown. Instead of initiating the co-cultures with pure cultures, two-step cultivation was employed to selectively enrich iron (III)-reducing microorganisms in a coastal gold mining river, Jiehe River, with rich iron content in the sediments. First, iron (III) reducers including Geobacteraceae were successfully enriched by 3-months successive culture on amorphous Fe(III) oxides as electron acceptor and acetate as electron donor. High-throughput Illumina sequencing, terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures actively contained the bacteria belong to Geobacteraceae and Bacilli, exclusively dominated by the archaea belong to Methanosarcinaceae. Second, the enrichment cultures including methanogens and Geobacteraceae were transferred with ethanol as alternative electron donor. Remarkably, aggregates were successively formed in the enrichments after three transfers. The results revealed by RNA-based analysis demonstrate that the co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III)-reducing enrichment culture. Furthermore, the aggregates, as close physical contact, formed in the enrichment culture, indicate that DIET could be a possible option for interspecies electron transfer in the aggregates.

No MeSH data available.


Related in: MedlinePlus