Dataset Information

Biodegradation of the allelopathic chemical m-tyrosine by Bacillus aquimaris SSC5 involves the homogentisate central pathway.

ABSTRACT: m-Tyrosine is an amino acid analogue, exuded from the roots of fescue grasses, which acts as a potent allelopathic and a broad spectrum herbicidal chemical. Although the production and toxic effects of m-tyrosine are known, its microbial degradation has not been documented yet. A soil microcosm study showed efficient degradation of m-tyrosine by the inhabitant microorganisms. A bacterial strain designated SSC5, that was able to utilize m-tyrosine as the sole source of carbon, nitrogen, and energy, was isolated from the soil microcosm and was characterized as Bacillus aquimaris. Analytical methods such as HPLC, GC-MS, and (1)H-NMR performed on the resting cell samples identified the formation of 3-hydroxyphenylpyruvate (3-OH-PPA), 3-hydroxyphenylacetate (3-OH-PhAc), and homogentisate (HMG) as major intermediates in the m-tyrosine degradation pathway. Enzymatic assays carried out on cell-free lysates of m-tyrosine-induced cells confirmed transamination reaction as the first step of m-tyrosine degradation. The intermediate 3-OH-PhAc thus obtained was further funneled into the HMG central pathway as revealed by a hydroxylase enzyme assay. Subsequent degradation of HMG occurred by ring cleavage catalyzed by the enzyme homogentisate 1, 2-dioxygenase. This study has significant implications in terms of understanding the environmental fate of m-tyrosine as well as regulation of its phytotoxic effect by soil microorganisms.

SUBMITTER: Khan F

PROVIDER: S-EPMC3788032 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Biodegradation of the allelopathic chemical m-tyrosine by Bacillus aquimaris SSC5 involves the homogentisate central pathway.

Khan Fazlurrahman F Kumari Munesh M Cameotra Swaranjit Singh SS

PloS one 20131001 10

m-Tyrosine is an amino acid analogue, exuded from the roots of fescue grasses, which acts as a potent allelopathic and a broad spectrum herbicidal chemical. Although the production and toxic effects of m-tyrosine are known, its microbial degradation has not been documented yet. A soil microcosm study showed efficient degradation of m-tyrosine by the inhabitant microorganisms. A bacterial strain designated SSC5, that was able to utilize m-tyrosine as the sole source of carbon, nitrogen, and energ ...[more]

PMID: 24098407

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Project description:Many plants produce allelopathic chemicals, such as stilbenes, to inhibit pathogenic fungi. The degradation of allelopathic compounds by bacteria associated with the plants would limit their effectiveness, but little is known about the extent of biodegradation or the bacteria involved. Screening of tissues and rhizosphere of peanut (Arachis hypogaea) plants revealed substantial enrichment of bacteria able to grow on resveratrol and pterostilbene, the most common stilbenes produced by the plants. Investigation of the catabolic pathway in Sphingobium sp. strain JS1018, isolated from the rhizosphere, indicated that the initial cleavage of pterostilbene was catalyzed by a carotenoid cleavage oxygenase (CCO), which led to the transient accumulation of 4-hydroxybenzaldehyde and 3,5-dimethoxybenzaldehyde. 4-Hydroxybenzaldehyde was subsequently used for the growth of the isolate, while 3,5-dimethoxybenzaldehyde was further converted to a dead-end metabolite with a molecular weight of 414 (C24H31O6). The gene that encodes the initial oxygenase was identified in the genome of strain JS1018, and its function was confirmed by heterologous expression in Escherichia coli This study reveals the biodegradation pathway of pterostilbene by plant-associated bacteria. The prevalence of such bacteria in the rhizosphere and plant tissues suggests a potential role of bacterial interference in plant allelopathy.IMPORTANCE Pterostilbene, an analog of resveratrol, is a stilbene allelochemical produced by plants to inhibit microbial infection. As a potent antioxidant, pterostilbene acts more effectively than resveratrol as an antifungal agent. Bacterial degradation of this plant natural product would affect the allelopathic efficacy and fate of pterostilbene and thus its ecological role. This study explores the isolation and abundance of bacteria that degrade resveratrol and pterostilbene in peanut tissues and rhizosphere, the catabolic pathway for pterostilbene, and the molecular basis for the initial cleavage of pterostilbene. If plant allelopathy is an important process in agriculture and management of invasive plants, the ecological role of bacteria that degrade the allelopathic chemicals must be equally important.

Dataset Information

Biodegradation of the allelopathic chemical m-tyrosine by Bacillus aquimaris SSC5 involves the homogentisate central pathway.

Publications

Biodegradation of the allelopathic chemical m-tyrosine by Bacillus aquimaris SSC5 involves the homogentisate central pathway.

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