Isolation and Characterization of 1-Hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic Acid, a Metabolite in Bacterial Transformation of Abscisic Acid

Abstract

We report the discovery of a new abscisic acid (ABA) metabolite, found in the course of a mass spectrometric study of ABA metabolism by the rhizosphere bacterium Rhodococcus sp. P1Y. Analogue of (+)-ABA, enriched in tritium in the cyclohexene moiety, was fed in bacterial cells, and extracts containing radioactive metabolites were purified and analyzed to determine their structure. We obtained mass spectral fragmentation patterns and nuclear magnetic resonance spectra of a new metabolite of ABA identified as 1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic acid, which we named rhodococcal acid (RA) and characterized using several other techniques. This metabolite is the second bacterial ABA degradation product in addition to dehydrovomifoliol that we described earlier. Taken together, these data reveal an unknown ABA catabolic pathway that begins with side chain disassembly, as opposed to the conversion of the cyclohexene moiety in plants. The role of ABA-utilizing bacteria in interactions with other microorganisms and plants is also discussed.

Strain Streptomyces sp. P-56 Produces Nonactin and Possesses Insecticidal, Acaricidal, Antimicrobial and Plant Growth-Promoting Traits

“…The recent trends in the study of bioactive secondary microbial metabolites [ 1 , 2 , 3 ] show the increasing practical importance of this field. Particularly, the metabolites produced by actinomycetes ( Actinomycetales) are very useful agents for pharmacology and agrobiology [ 4 , 5 , 6 , 7 , 8 ].…”

Fourier Transform Infrared (FTIR) Spectroscopic Study of Biofilms Formed by the Rhizobacterium Azospirillum baldaniorum Sp245: Aspects of Methodology and Matrix Composition

“…The diverse field of microbiology has been progressively developing over the last decades, largely owing to the steadily growing applications of a range of modern molecular spectroscopy techniques that provide molecular-level information on complicated microbiological objects and allow for successfully solving various bioanalytical problems, often in situ or in vivo (see, e.g., [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]). We would like to emphasize the informativity of very relevant vibrational spectroscopic techniques, including various modifications of infrared (conventional absorption [ 2 , 7 , 11 , 16 ], diffuse reflectance [ 3 , 6 ], attenuated total reflectance (ATR) [ 5 , 17 ] and surface-enhanced absorption [ 15 ] modes; 2D infrared [ 8 ]) and Raman [ 1 , 2 , 13 ] spectroscopies, as well as their combinations [ 4 , 14 ]; vibrational circular dichroism [ 12 ], optical activity [ 9 ], etc. Of special notice are microbiological applications of Mössbauer spectroscopy, in both transmission and emission variants [ 2 , 10 ].…”