Melanin-Like Pigment Synthesis by Soil Bacillus weihenstephanensis Isolates from Northeastern Poland

Abstract

Although melanin is known for protecting living organisms from harmful physical and chemical factors, its synthesis is rarely observed among endospore-forming Bacillus cereus sensu lato. Here, for the first time, we reported that psychrotolerant Bacillus weihenstephanensis from Northeastern Poland can produce melanin-like pigment. We assessed physicochemical properties of the pigment and the mechanism of its synthesis in relation to B. weihenstephanensis genotypic and phenotypic characteristics. Electron paramagnetic resonance (EPR) spectroscopy displayed a stable free radical signal of the pigment from environmental isolates which are consistent with the commercial melanin. Fourier transform infrared spectroscopy (FT-IR) and physicochemical tests indicated the phenolic character of the pigment. Several biochemical tests showed that melanin-like pigment synthesis by B. weihenstephanensis was associated with laccase activity. The presence of the gene encoding laccase was confirmed by the next generation whole genome sequencing of one B. weihenstephanensis strain. Biochemical (API 20E and 50CHB tests) and genetic (Multi-locus Sequence Typing, 16S rRNA sequencing, and Pulsed-Field Gel Electrophoresis) characterization of the isolates revealed their close relation to the psychrotrophic B. weihenstephanensis DSMZ 11821 reference strain. The ability to synthesize melanin-like pigment by soil B. weihenstephanensis isolates and their psychrotrophic character seemed to be a local adaptation to a specific niche. Detailed genetic and biochemical analyses of melanin-positive environmental B. weihenstephanensis strains shed some light on the evolution and ecological adaptation of these bacteria. Moreover, our study raised new biotechnological possibilities for the use of water-soluble melanin-like pigment naturally produced by B. weihenstephanensis as an alternative to commercial non-soluble pigment.

Characterization of a nontoxic pyomelanin pigment produced by the yeast Yarrowia lipolytica

“…Melanin‐like brown pigment derived from L‐tyrosine could be synthesized through two different pathways, namely the L‐DOPA and the HGA pathways. As specific inhibitors of these pathways are available, it is possible to determined which one leads to the brown pigment formation in Y. lipolytica . For that purpose, strain W29 was grown in YNBTy supplemented with arginine, used as inhibitor of L‐DOPA pathway or sulcotrione, used as an inhibitor of the HGA pathway.…”

“…For that purpose, strain W29 was grown in YNBTy supplemented with arginine, used as inhibitor of L‐DOPA pathway or sulcotrione, used as an inhibitor of the HGA pathway. This latter being an inhibitor of the 4‐hydroxyphenylpyruvate dioxygenase encoded by gene YALI0B21846p in Y. lipolytica . As shown in Figure a, the supplementation of the culture medium with arginine did not impair the cell ability to synthetize the brown pigment.…”

“…In the so‐called 3,4‐dihydroxy‐L‐phenylalanine pathway (L‐DOPA pathway), the synthesis starts with a multi‐step enzymatic conversion of L‐tyrosine to DOPA‐quinone through a L‐DOPA intermediate. This conversion is catalyzed by three different enzymes, namely laccase, tyrosinase, and tyrosine hydroxylase . Then after, a series of nonenzymatic polymerization reactions leads to the conversion of DOPA‐quinone to eumelanin.…”

“…This conversion is catalyzed by three different enzymes, namely laccase, tyrosinase, and tyrosine hydroxylase. 7 Then after, a series of nonenzymatic polymerization reactions leads to the conversion of DOPA-quinone to eumelanin. Actually, this metabolic pathway is considered as the best characterized melanization synthesis pathway from L-tyrosine.…”

Infectious Pseudochromhidrosis: A Case Report and Literature Review

“…Apart from B. cereus, previous studies have also described pigment production in many other Bacillus spp. (90)(91)(92)(93)(94).…”