Assessing the efficacy of antibiotic treatment to produce earthworms with a suppressed microbiome

Omosigho, H. O., Swart, E., Sizmur, T. P. ORCID: https://orcid.org/0000-0001-9835-7195, Spurgeon, D. J., Svendsen, C. and Shaw, L. J. (2022) Assessing the efficacy of antibiotic treatment to produce earthworms with a suppressed microbiome. European Journal of Soil Biology, 108. 103366. ISSN 1164-5563 doi: 10.1016/j.ejsobi.2021.103366

Abstract/Summary

Earthworms are an integral part of soil ecosystems, especially for their role in soil functions such as organic matter (OM) decomposition and nutrient cycling. Earthworms and microorganisms are interdependent, and a considerable portion of the contribution earthworms make to influencing OM fate is through interactions with microorganisms. However, the importance of the earthworm-associated microbiome is not fully understood, because it is difficult to separate the direct influence of the earthworms from the indirect influence of their microbiome. Here, we evaluated an antibiotic-based procedure to suppress the microbiome of individuals of ecologically-contrasting earthworm species (Eisenia fetida, Lumbricus terrestris, Allolobophora chlorotica) as the first step towards soil studies aimed at understanding the importance of the earthworm microbiome for host health and function. Individual earthworms were exposed to antibiotics: cycloheximide (150 μg ml-1), ampicillin (100 μg ml-1), ciprofloxacin (50 μg ml-1), nalidixic acid (50 μg ml-1), and gentamicin (50 μg ml-1) either singly or in a cocktail via culture (96 h) in a semi-solid agar carrier. Compared to the non-antibiotic treated control, the cocktail (for all three species) and ciprofloxacin (for E. fetida and A. chlorotica) treatments significantly reduced (P<0.05) culturable microbial abundance on nutrient agar and potato dextrose agar. The microbial counts were reduced to below detection (<50 CFU individual-1) for E. fetida and A. chlorotica receiving the cocktail. Illumina 16S rDNA amplicon sequence analysis of culturable L. terrestris -associated bacteria showed that antibiotic treatment influenced community composition revealing putative sensitive (Comomonas, Kosakonia and Sphingobacterium) and insensitive (Aeromonas, Pseudochrobactrum) taxa. Overall, we report a rapid, with minimal earthworm- handling, process of creating suppressed-microbiome E. fetida, A. chlorotica and L. terrestris as a tool to be used in future ecological studies of earthworm microbial interactions affecting host health and function.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/101338
Item Type	Article
Refereed	Yes
Divisions	Science > School of Archaeology, Geography and Environmental Science > Department of Geography and Environmental Science Interdisciplinary centres and themes > Soil Research Centre
Publisher	Elsevier
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