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  Microprofiles of oxygen, redox potential, and pH, and microbial fermentation products in the highly alkaline gut of the saprophagous larva of Penthetria holosericea (Diptera: Bibionidae)

Sustr, V., Stingl, U., & Brune, A. (2014). Microprofiles of oxygen, redox potential, and pH, and microbial fermentation products in the highly alkaline gut of the saprophagous larva of Penthetria holosericea (Diptera: Bibionidae). Journal of Insect Physiology, 67, 64-69. doi:10.1016/j.jinsphys.2014.06.007.

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https://doi.org/10.1016/j.jinsphys.2014.06.007 (Publisher version)
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 Creators:
Sustr, V., Author
Stingl, U., Author           
Brune, A.1, Author                 
Affiliations:
1Department-Independent Research Group Insect Gut Microbiology and Symbiosis, Max Planck Institute for Terrestrial Microbiology, Max Planck Society, ou_3266271              

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Free keywords: Dipteran larvae; Gut pH; Redox potential; Oxygen partial pressure; Hydrogen partial pressure
 Abstract: The saprophagous larvae of bibionid flies harbor bacteria in their alkaline intestinal tracts, but little is known about the contribution of the gut microbiota to the digestion of their recalcitrant diet. In this study, we measured oxygen and hydrogen partial pressure, redox potential and pH in the midgut, gastric caeca and hindgut of larvae of the bibionid fly Penthetria holosericea with Clark-type O2 and H2 microsensors, platinum redox microelectrodes, and LIX-type pH microelectrodes. The center of the midgut lumen was anoxic, whereas gastric caeca and hindgut were hypoxic. However, redox potential profiles indicated oxidizing conditions throughout the gut, with lowest values in the midgut (+20 to +60 mV). Hydrogen production was not detected. The midgut was extremely alkaline (pH around 11), whereas hindgut and gastric caeca were neutral to slightly alkaline. While HPLC analysis showed high concentrations of glucose in the midgut (15 mM) and gastric caeca (27 mM), the concentrations of microbial fermentation products such as lactate (2–4 mM), acetate (<1 mM) and succinate (<0.5 mM) were low in all gut regions, suggesting that the contribution of microorganisms to the digestive process, particularly in the alkaline midgut, is only of minor importance. We conclude that the digestive strategy of the saprophytic larva of P. holosericea, which feeds selectively on decomposed leaves and its own microbe-rich faeces, differs fundamentally from those of detritivorous and humivorous insects, which host a highly active, fermentative microbiota in their alkaline midgut or hindgut compartments.

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Language(s): eng - English
 Dates: 2014-08
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 701628
ISI: 000340326900008
DOI: 10.1016/j.jinsphys.2014.06.007
 Degree: -

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Title: Journal of Insect Physiology
Source Genre: Journal
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Publ. Info: OXFORD : PERGAMON-ELSEVIER SCIENCE LTD
Pages: - Volume / Issue: 67 Sequence Number: - Start / End Page: 64 - 69 Identifier: ISSN: 0022-1910