Degradation of aromatic carboxylic acids by acinetobacter

The degradation of the aromatic carboxylic acids 3-phenylpropionic acid, cinnamic acid and L-phenylalanine was investigated in several strains of Acinetobacter calcoaceticus var. lwoffii. Evidence is presented for the conversion of 3-phenylpropionic acid into the cis-2,3-dihydrodihydroxy-derivative, which is further metabolized to 3-(2,3-dihydroxyphenyl-)propionic acid, followed by cleavage of the aromatic ring in meta-proximal position. When pre-grown on 3-phenylpropionic acid, cinnamic acid as well as L-phenylalanine were metabolized under resting cell conditions via the same degradation pathway. When cultivated with cinnamic acid as sole carbon source 4-hydroxycinnamate, together with 4-hydroxybenzoate and protocatechuate were found as metabolites. L-phenylalanine, when provided as the only carbon source, is converted via phenylacetic acid to 2-hydroxyphenyl-acetic acid. All metabolites were identified by conventional chemical techniques. Enzymatic studies yielded further support for the proposed pathways. In 14 of 15 Acinetobacter strains the presence of plasmid DNA could be detected. The number of plasmids varied between 1 and 7. Regarding the number and size of the plasmids considerable variations within the different bacterial strains were observed. No extended homology among the plasmids could be shown by restriction endonuclease digestion. One strain exhibiting a high spontaneous mutation rate to the 3-phenylpropionic acid-negative phenotype did not show any change in its plasmid pattern. The results lead us to conclude that a correlation between the degradative properties of these strains and the presence of plasmid DNA is unlikely.