| Summary: | Streptomycetes were isolated from soil samples and screened for biodegradative activity
against lignin-related aromatic compounds. One isolate, Streptomyces violaceusniger,
efficiently utilized 4-hydroxy-3-methoxybenzoic acid (vanillate) and 4-hydroxybenzoic
acid (p-hydroxybenzoate) as sole sources of carbon and energy. S. violaceusniger was
able to biotransform indole to the dye indigo, indicative of aromatic dioxygenase activity.
Colorimetric Rothera assays demonstrated the induction of aromatic dioxygenase
activity in S. violaceusniger in the presence of vanillate and p-hydroxybenzoate. Twodimensional
gel electrophoresis of total cell proteins revealed the synthesis of specific
groups of proteins upon growth in the presence of vanillate, p-hydroxybenzoate or 3,4-
dihydroxybenzoic acid (protocatechuate). The amino-terminal sequence of a heavily
expressed 52 kDa protein, induced by vanillate andp-hydroxybenzoate, was highly
similar to the amino-terminus of a hypothetical 55 kDa protein discovered during the
course of the Escherichia coli genome sequencing project. The S. violaceusniger
sequence aligns with conserved regions adjacent to nucleotide binding domains of the
GTP-binding cc-subunit protein family and valyl-tRNA synthetases. Because
biodegradative monooxygenases are known to possess nucleotide binding domains near
the amino terminus and the protein is synthesized in such abundance, it is suggested that
the 52 kDa protein is an enzyme involved in aromatic biodegradation. The results of this
work are of interest to the study of lignin biodegradation, and also to the study of the
catabolism of phenolic compounds in Streptomyces. === Science, Faculty of === Microbiology and Immunology, Department of === Graduate
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