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 1H-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.

Identification and comparative analysis of microRNAs in barnyardgrass (Echinochloa crus‐galli) in response to rice allelopathy

“…Our studies showed that the expression 3 of these miRNAs was greatly increased in BYG treated with different phenolic acids. Microorganisms, an important link between allelochemicals and target plants, have 9 received increasing attention (Bertin et al 2003;Blum 2003;Dayan et al 2010;10 Inderjit 2005;Khan et al 2013;Zuo et al 2014), and the biotransformation of 11 allelochemicals by particular environmental microorganisms has been reported to be 12 necessary and to contribute to an increase in allelopathy (Wang et al 2013). In this 13 study, a specific microbe, the Myxococcus species, showed a close relationship with 14 rice allelopathic inhibition.…”

Innovative Microbial Immobilization Strategy for Di-n-Butyl Phthalate Biodegradation Using Biochar-Calcium Alginate-Waterborne Polyurethane Composites

“…In previous studies, B. aquimaris has been demonstrated to degrade various pollutants, including microplastics [48,49]. This strain can be isolated from soil or marine environments and is commonly found in the environment [48,50].…”

Assaying the potential autotoxins and microbial community associated with Rehmannia glutinosa replant problems based on its ‘autotoxic circle’

“…In this work, we found that some congeneric species showed a close interaction with allelochemicals. For instance, Pseudomonas catalysed (-)-catechin conversion into 3,4-dihydroxybenzoic acid, and 3,4-dihydroxybenzoic acid showed a higher phytotoxicity than (-)-catechin (Masuda et al 2007); Bacillus aquimaris involved in the degradation of allelopathic m-tyrosine (Khan et al 2013); F. oxysporum, a replant disease pathogen in P. heterophylla rhizospheric soil, increased sharply under a consecutive-replant system, and some phenolic acids promoted the growth of F. oxysporum f.sp. (Zhao et al 2015).…”