NOVEL ASPECTS OF BENZOATE AND CROTONATE METABOLISM

In anoxic environments, many aromatic compounds (AC)
are transformed to benzoylCoA, prior to
dearomatization and ring cleavage. Due to the
resonance stability of the aromatic ring, AC are
difficult to degrade in the absence of O2. Benzoate
degradation in methanogenic ecosystems is mediated by
syntrophic association of a fermentative bacterium
with a H2/formate-using methanogen. The metabolism of
crotonate in the strictly anaerobic bacteria
S.aciditrophicus (SB) was studied and
indicated that cyclohexane carboxylate and acetate as
end products. In addition to benzoate fermentation,
SB as the ability to use benzoate as an electron
acceptor with crotonate as the electron
donor.Phototrophic and denitrifying bacteria couple
the hydrolysis of 2 ATP to reduce benzoylCoA to
cyclohexediene carboxylCoA. The use of
such an energy intensive reaction by fermentative
bacteria such as SB has been questioned since it is
not clear how net ATP synthesis would occur. The
utilization of fluorobenzoate by SB allowed the
detection of a fluorinated diene intermediate.
Proteomic analysis of SB grown with crotonate or
benzoate allowed the identification of gene
products involved in benzoate metabolism.

Autorentext

Housna Mouttaki, PhD: Studied Environmental Microbiology at theUniversity of Oklahoma, USA in Prof. McInerney's laboratory; BS:Cell Biology and Physiology at Université Blaise Pascal inClermont-Ferrand, France.

Klappentext

In anoxic environments, many aromatic compounds (AC)are transformed to benzoylCoA, prior todearomatization and ring cleavage. Due to theresonance stability of the aromatic ring, AC aredifficult to degrade in the absence of O2. Benzoatedegradation in methanogenic ecosystems is mediated bysyntrophic association of a fermentative bacteriumwith a H2/formate-using methanogen. The metabolism ofcrotonate in the strictly anaerobic bacteriaS.aciditrophicus (SB) was studied andindicated that cyclohexane carboxylate and acetate asend products. In addition to benzoate fermentation,SB as the ability to use benzoate as an electronacceptor with crotonate as the electrondonor.Phototrophic and denitrifying bacteria couplethe hydrolysis of 2 ATP to reduce benzoylCoA tocyclohexediene carboxylCoA. The use ofsuch an energy intensive reaction by fermentativebacteria such as SB has been questioned since it isnot clear how net ATP synthesis would occur. Theutilization of fluorobenzoate by SB allowed thedetection of a fluorinated diene intermediate.Proteomic analysis of SB grown with crotonate orbenzoate allowed the identification of geneproducts involved in benzoate metabolism.