Aqueous iron-sulfur systems in rice field soils of Louisiana

Pitts, Gary; Allam, A. I.; Hollis, J. P.

doi:10.1007/bf01373480

Cited by 6 publications

(2 citation statements)

References 5 publications

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“…Pyrite (FeS 2) is ubiquitously present in anoxic environments [30] and is an important constituent of paddy soil [31]. We can only speculate about the reasons of its protective effect for methanogens.…”

Section: Discussionmentioning

confidence: 99%

Sensitivity of methanogenic bacteria from paddy soil to oxygen and desiccation

Fetzer

1993

FEMS Microbiology Ecology

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The effects of combinations of desiccation and exposure to 0 2 were studied in pure cultures of Methanosarcina barkeri strain Fusaro and in a new Methanosa~'ina strain and a new Methanobacterium strain which were both isolated from dry oxic paddy soil. Incubation of bacterial suspensions under air for 200 min resulted in a decreased potential to produce CH 4, but not in a decreased viability. The inhibitory effect of 0 2 slightly increased with increased salt concentration. Desiccation of bacterial suspensions under N 2 resulted in reduction of viability to 10% and of potential CH 4 production to 0.6%. Desiccation of bacterial suspensions under air resulted in a larger decrease of both viability (0.5%) and potential CH 4 production (0.03%). This decrease was smaller at rapid compared to slow deslccation. Survival and potential CH 4 production were further inhibited when the suspension was dried in the presence of sand grains or glass beads coated with FeS or FeNH4PO 4. However, survival and potential CH 4 production increased dramatically'in the presence of pyrite (FeS 2) grains. Then, as much as 10% of the initial methanogenic population survived oxic desiccation. This relatively good resistance is in agreement with observations that methanogens in rice fields survive the periods when the paddy soil is dry and oxic.

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Section: Discussionmentioning

confidence: 99%

Sensitivity of methanogenic bacteria from paddy soil to oxygen and desiccation

Fetzer

1993

FEMS Microbiology Ecology

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“…A significant portion (0.5–10%) of the isolates Methanosarcina strain MVF4 and Methanobacterium strain HVF5 also survived the additive effect of desiccation and exposure to oxygen [50]. The survival rate was even higher in the presence of pyrite (FeS 2 ), which is an important constituent of rice paddy soil [51]. Consequently, it was hypothesized that the highly uneven, ‘raspberry’‐like surface of the spheroidal pyrite crystals [52] may be a protective habitat for methanogens [50].…”

Section: Rice Soil Microbial Communitymentioning

confidence: 99%

Microbiology of flooded rice paddies

2000

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Flooded rice paddies are one of the major biogenic sources of atmospheric methane. Apart from this contribution to the 'greenhouse' effect, rice paddy soil represents a suitable model system to study fundamental aspects of microbial ecology, such as diversity, structure, and dynamics of microbial communities as well as structure-function relationships between microbial groups. Flooded rice paddy soil can be considered as a system with three compartments (oxic surface soil, anoxic bulk soil, and rhizosphere) characterized by different physio-chemical conditions. After flooding, oxygen is rapidly depleted in the bulk soil. Anaerobic microorganisms, such as fermentative bacteria and methanogenic archaea, predominate within the microbial community, and thus methane is the final product of anaerobic degradation of organic matter. In the surface soil and the rhizosphere well-defined microscale chemical gradients can be measured. The oxygen profile seems to govern gradients of other electron acceptors (e.g., nitrate, iron(III), and sulfate) and reduced compounds (e.g., ammonium, iron(II), and sulfide). These gradients provide information about the activity and spatial distribution of functional groups of microorganisms. This review presents the current knowledge about the highly complex microbiology of flooded rice paddies. In Section 2 we describe the predominant microbial groups and their function with particular regard to bacterial populations utilizing polysaccharides and simple sugars, and to the methanogenic archaea. Section 3 describes the spatial and temporal development of microscale chemical gradients measured in experimentally defined model systems, including gradients of oxygen and dissolved and solid-phase iron(III) and iron(II). In Section 4, the results of measurements of microscale gradients of oxygen, pH, nitrate-nitrite, and methane in natural rice fields and natural rice soil cores taken to the laboratory will be presented. Finally, perspectives of future research are discussed (Section 5).

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