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. 1997 Oct;63(10):4039–4046. doi: 10.1128/aem.63.10.4039-4046.1997

Hydrogen Concentration Profiles at the Oxic-Anoxic Interface: a Microsensor Study of the Hindgut of the Wood-Feeding Lower Termite Reticulitermes flavipes (Kollar)

A Ebert, A Brune
PMCID: PMC1389272  PMID: 16535716

Abstract

Molecular hydrogen is a key intermediate in lignocellulose degradation by the microbial community of termite hindguts. With polarographic, Clark-type H(inf2) microelectrodes, we determined H(inf2) concentrations at microscale resolution in the gut of the wood-feeding lower termite Reticulitermes flavipes (Kollar). Axial H(inf2) concentration profiles obtained from isolated intestinal tracts embedded in agarose Ringer solution clearly identified the voluminous hindgut paunch as the site of H(inf2) production. The latter was strictly coupled with both a low redox potential (E(infh) = -200 mV) and the absence of oxygen, in agreement with the growth requirements of the cellulolytic, H(inf2)-producing flagellates located in the hindgut paunch. Luminal H(inf2) partial pressures were much higher than expected (ca. 5 kPa) and increased more than threefold when the guts were incubated under a N(inf2) headspace. Radial H(inf2) concentration gradients showed a steep decrease from the gut center towards the periphery, indicating the presence of H(inf2)-consuming activities both within the lumen and at the gut epithelium. Measurements under controlled gas headspace showed that the gut wall was also a sink for externally supplied H(inf2), both under oxic and anoxic conditions. With O(inf2) microelectrodes, we confirmed that the H(inf2) sink below the gut epithelium is located within the microoxic gut periphery, but the H(inf2)-consuming activity itself, at least a substantial part of it, was clearly due to an anaerobic process. These results are in accordance with the recently reported presence of methanogens attached in large numbers to the luminal side of the hindgut epithelium of R. flavipes. If the oxygen partial pressure was increased, O(inf2) penetrated deeper and H(inf2) production was suppressed; it ceased completely as soon as the gut was fully oxic. In experiments with living termites, externally supplied H(inf2) (20 kPa) stimulated methane formation five- to sixfold to 0.93 (mu)mol (g of termite)(sup-1) h(sup-1), indicating that the methanogenic activity in R. flavipes hindguts is not saturated for hydrogen under in situ conditions. This rate was in good agreement with the H(inf2) uptake rates exhibited by isolated hindguts, which would account for more than half of the CH(inf4) formed by living termites under comparable conditions.

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Selected References

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  1. Brauman A., Kane M. D., Labat M., Breznak J. A. Genesis of acetate and methane by gut bacteria of nutritionally diverse termites. Science. 1992 Sep 4;257(5075):1384–1387. doi: 10.1126/science.257.5075.1384. [DOI] [PubMed] [Google Scholar]
  2. Breznak J. A. Intestinal microbiota of termites and other xylophagous insects. Annu Rev Microbiol. 1982;36:323–343. doi: 10.1146/annurev.mi.36.100182.001543. [DOI] [PubMed] [Google Scholar]
  3. Breznak J. A., Switzer J. M. Acetate Synthesis from H(2) plus CO(2) by Termite Gut Microbes. Appl Environ Microbiol. 1986 Oct;52(4):623–630. doi: 10.1128/aem.52.4.623-630.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Brune A., Emerson D., Breznak J. A. The Termite Gut Microflora as an Oxygen Sink: Microelectrode Determination of Oxygen and pH Gradients in Guts of Lower and Higher Termites. Appl Environ Microbiol. 1995 Jul;61(7):2681–2687. doi: 10.1128/aem.61.7.2681-2687.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Brune A., Miambi E., Breznak J. A. Roles of oxygen and the intestinal microflora in the metabolism of lignin-derived phenylpropanoids and other monoaromatic compounds by termites. Appl Environ Microbiol. 1995 Jul;61(7):2688–2695. doi: 10.1128/aem.61.7.2688-2695.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Ellis J. E., McIntyre P. S., Saleh M., Williams A. G., Lloyd D. Influence of CO2 and low concentrations of O2 on fermentative metabolism of the ruminal ciliate Polyplastron multivesiculatum. Appl Environ Microbiol. 1991 May;57(5):1400–1407. doi: 10.1128/aem.57.5.1400-1407.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Friedrich M., Schink B. Hydrogen formation from glycolate driven by reversed electron transport in membrane vesicles of a syntrophic glycolate-oxidizing bacterium. Eur J Biochem. 1993 Oct 1;217(1):233–240. doi: 10.1111/j.1432-1033.1993.tb18238.x. [DOI] [PubMed] [Google Scholar]
  8. Jensen K., Revsbech N. P., Nielsen L. P. Microscale distribution of nitrification activity in sediment determined with a shielded microsensor for nitrate. Appl Environ Microbiol. 1993 Oct;59(10):3287–3296. doi: 10.1128/aem.59.10.3287-3296.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Jones L. W., Bishop N. I. Simultaneous measurement of oxygen and hydrogen exchange from the blue-green alga anabaena. Plant Physiol. 1976 Apr;57(4):659–665. doi: 10.1104/pp.57.4.659. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Leadbetter J. R., Breznak J. A. Physiological ecology of Methanobrevibacter cuticularis sp. nov. and Methanobrevibacter curvatus sp. nov., isolated from the hindgut of the termite Reticulitermes flavipes. Appl Environ Microbiol. 1996 Oct;62(10):3620–3631. doi: 10.1128/aem.62.10.3620-3631.1996. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Odelson D. A., Breznak J. A. Nutrition and Growth Characteristics of Trichomitopsis termopsidis, a Cellulolytic Protozoan from Termites. Appl Environ Microbiol. 1985 Mar;49(3):614–621. doi: 10.1128/aem.49.3.614-621.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Odelson D. A., Breznak J. A. Volatile Fatty Acid production by the hindgut microbiota of xylophagous termites. Appl Environ Microbiol. 1983 May;45(5):1602–1613. doi: 10.1128/aem.45.5.1602-1613.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Platen H., Schink B. Methanogenic degradation of acetone by an enrichment culture. Arch Microbiol. 1987;149(2):136–141. doi: 10.1007/BF00425079. [DOI] [PubMed] [Google Scholar]
  14. Schink B. Energetics of syntrophic cooperation in methanogenic degradation. Microbiol Mol Biol Rev. 1997 Jun;61(2):262–280. doi: 10.1128/mmbr.61.2.262-280.1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Wang R., Healey F. P., Myers J. Amperometric measurement of hydrogen evolution in chlamydomonas. Plant Physiol. 1971 Jul;48(1):108–110. doi: 10.1104/pp.48.1.108. [DOI] [PMC free article] [PubMed] [Google Scholar]

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