Brown pigmentation in Serratia marcescens cultures associated with tyrosine metabolism

Abstract

Serratia marcescens produced a brown pigment when grown in minimal medium in the presence of tyrosine and high concentrations of copper(II) ion. The pigment was not related to the melanin pigments, but was similar to the pigment produced by autooxidation and polymerization of 3,4-dihydroxyphenylacetate, which is synthesized in S. marcescens from tyrosine through the 3,4-dihydroxyphenylacetate catabolic pathway. The enzymes of this pathway were induced under pigment production conditions; however, 3,4-dihydroxyphenylacetate 2,3-dioxygenase remained at low activity levels, permitting the accumulation and excretion of the substrate. Mutants unable to use tyrosine as a sole carbon and energy source were able to produce brown pigments only if the step blocked by the mutation was after the synthesis of 3,4-dihydroxyphenylacetate. The ability to produce brown pigments was common to all the S. marcescens strains tested.

Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes

“…In agreement with the bacterial diversity, other species such as S. marcescens [141] form a brown pigment by oxidation and polymerization of intermediates of catabolic pathways. In that species, the melanin precursor is 3,4-dihydroxyphenylacetate.…”

“…The final steps of this polymerization pathway are also undefined and poorly studied, but, as in other systems, a phenol oxidase or laccase can be involved in the oxidation of HGA to the corresponding p-quinone. This form of pyomelanin is formed in some fungi, such as Aspergillus fumigatus [124], bacterial species, such as Vibrio cholerae [146], or even in human (alkaptonuria) but in bacteria similar dark yellowish pyomelanin can be formed from other p-dihydroxyphenols different from HGA, such as Serratia marcescens [141] or Pseudomonas [142].…”

A Streptomyces avermitilis gene encoding a 4-hydroxyphenylpyruvic acid dioxygenase-like protein that directs the production of homogentisic acid and an ochronotic pigment in Escherichia coli

“…It is generally believed that the autoxidation and polymerization of benzoquinoneacetic acid to the ochronotic pigment resemble the mechanism by which dopaquinone is converted into melanin (29). Similarly, oxidation of DOPAC leads to the formation of a brown pigment having the appearance of both melanin and ochronotic pigment in Serratia marcescens (50).…”

“…The urine of alkaptonuric patients contains large amounts of HGA, which, on standing or when made alkaline and exposed to oxygen, turns dark because it is oxidized and polymerized to an ochronotic (derived from ochre; yellowish-brown color) pigment (29). Interestingly, formation of similar pigments resulting from the secretion and oxidation of either HGA or homoprotocatechuic acid (3,4-dihydroxyphenylacetic acid [DOPAC]) has been reported for some bacteria (19,50). In those cases, either DOPAC or HGA is probably produced through two alternative tyrosine catabolic pathways that use 4-hydroxyphenylacetate as an intermediate (7,9).…”

“…Since the production of the brown pigment in the recombinant E. coli clone was enhanced by the presence of tyrosine in the medium, it was inferred that the cloned DNA was involved in melanin biosynthesis via a tyrosinase in S. avernitilis (Fig. 1 (42) supplemented, where indicated, with L-tyrosine (600 ,ug/ml) and/or ampicillin (50 ,ug/ml). In some experiments, to enhance pigment detection in the solid medium surrounding E. coli colonies grown overnight at 37°C, 1 ml of 10 N NaOH was added on top of each 20-ml agar plate.…”