Degradation of the Indospicine Toxin from Indigofera spicata by a Mixed Population of Rumen Bacteria.

Rosalind A Gilbert,Kerri Chandra,Gabriele Netzel,Diane Ouwerkerk,Mary T Fletcher

doi:10.3390/toxins13060389

Rosalind A Gilbert, Kerri Chandra + Show 3 more

Open Access

https://doi.org/10.3390/toxins13060389

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Journal: Toxins	Publication Date: May 28, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: University of Queensland, Agriculture and Food

Abstract

The leguminous plant species, Indigofera linnaei and Indigofera spicata are distributed throughout the rangeland regions of Australia and the compound indospicine (L-2-amino-6-amidinohexanoic acid) found in these palatable forage plants acts as a hepatotoxin and can accumulate in the meat of ruminant livestock and wild camels. In this study, bovine rumen fluid was cultivated in an in vitro fermentation system provided with Indigofera spicata plant material and the ability of the resulting mixed microbial populations to degrade indospicine was determined using UPLC–MS/MS over a 14 day time period. The microbial populations of the fermentation system were determined using 16S rRNA gene amplicon sequencing and showed distinct, time-related changes occurring as the rumen-derived microbes adapted to the fermentation conditions and the nutritional substrates provided by the Indigofera plant material. Within eight days of commencement, indospicine was completely degraded by the microbes cultivated within the fermenter, forming the degradation products 2-aminopimelamic acid and 2-aminopimelic acid within a 24 h time period. The in vitro fermentation approach enabled the development of a specifically adapted, mixed microbial population which has the potential to be used as a rumen drench for reducing the toxic side-effects and toxin accumulation associated with ingestion of Indigofera plant material by grazing ruminant livestock.

Highlights

The Indigofera plant species are deep-rooted, perennial shrubs that are highly palatable to ruminant livestock and are considered endemic in many countries, those in subtropical and tropical regions [1,2]
Of the many Indigofera species present in Australia, at least eight have been found to contain the non-acute hepatotoxin indospicine [5,6], which was demonstrated in rodent studies to be the responsible toxin by subcutaneous injection of the isolated amino acid [7]
Indospicine is an arginine analogue, which, rather than being incorporated into proteins, persists as a free amino acid which can accumulate in tissues of animals who have ingested Indigofera plant material [8,9,10]

Summary

Introduction

The Indigofera plant species are deep-rooted, perennial shrubs that are highly palatable to ruminant livestock and are considered endemic in many countries, those in subtropical and tropical regions [1,2]. Indospicine is an arginine analogue, which, rather than being incorporated into proteins, persists as a free amino acid which can accumulate in tissues of animals who have ingested Indigofera plant material [8,9,10]. Several species of herbivores have been shown to bioaccumulate indospicine including horses, goats, cattle, rabbits and camels, resulting in poor animal performance, reduced weight. Toxins 2021, 13, 389 indospicine including horses, goats, cattle, rabbits and camels, resulting in poor animal performance, reduced weight gain, reproductive losses and mild to severe liver disease [1]. Inreproductive addition, indospicine represents a potential safety with domesticated gain, losses and mild to severe liver food disease [1]. Inreproductive addition, indospicine represents a potential safety with domesticated gain, losses and mild to severe liver food disease [1]. issue, In addition, indospicine dogs suffering liver damage following ingestion of indospicine-contaminated meat [11–

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