Melanin biosynthesis in bacteria, regulation and production perspectives Original paper
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Dr. Umar
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Dr. Umar
Read MoreClinical Pharmacist and Clinical Pharmacy Master’s candidate focused on antibiotic stewardship, AI-driven pharmacy practice, and research that strengthens safe and effective medication use. Experience spans digital health research with Bloomsbury Health (London), pharmacovigilance in patient support programs, and behavioral approaches to mental health care. Published work includes studies on antibiotic use and awareness, AI applications in medicine, postpartum depression management, and patient safety reporting. Developer of an AI-based clinical decision support system designed to enhance antimicrobial stewardship and optimize therapeutic outcomes.
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Dr. Umar
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Researched by:
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Dr. Umar
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Dr. Umar
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Microbiome Signatures identifies and validates condition-specific microbiome shifts and interventions to accelerate clinical translation. Our multidisciplinary team supports clinicians, researchers, and innovators in turning microbiome science into actionable medicine.
Dr. Umar
What was reviewed?
This mini-review summarizes bacterial melanin biosynthesis pathways, how melanin production is regulated, what ecological and pathogenic advantages melanins confer, and how these pigments can be scaled for biotechnology. The authors emphasize that bacterial melanins are heterogeneous biopolymers formed by oxidative polymerization of phenolic/indolic precursors, typically arising from tyrosine metabolism (via L-DOPA, homogentisate, or homoprotocatechuate) or, less commonly, from malonyl-CoA through type III polyketide synthases. The review also highlights practical characterization approaches (UV–Vis/FTIR signatures) and frames melanin as a multifunctional “stress-response material” with expanding applications in biomaterials, bioremediation, and bioelectronics.
Who was reviewed?
Rather than focusing on a single patient population, the review synthesizes evidence across diverse bacterial taxa, spanning Gram-positive and Gram-negative organisms, environmental isolates, symbionts, and clinically relevant pathogens. Examples include melanogenic Streptomyces (tyrosinase- and polyketide-derived melanins), Pseudomonas aeruginosa (pyomelanin via homogentisate accumulation), Vibrio cholerae, Ralstonia solanacearum, Sinorhizobium/Rhizobium species linked to symbiosis, and extremophiles from deserts, polar regions, marine habitats, and polluted ecosystems. This breadth is clinically relevant because melanin production can influence virulence, oxidative stress tolerance, persistence, and biofilm-associated survival across multiple infection contexts.
Most important findings
Melanin formation in bacteria converges on a core chemistry: oxidation of hydroxylated aromatics into quinones followed by spontaneous polymerization. The dominant biosynthetic “routes” are (1) DOPA/eumelanin, driven by tyrosinases and sometimes laccases, where tyrosine → L-DOPA → dopaquinone → polymer; (2) pyomelanin, where tyrosine catabolism produces homogentisate that accumulates (often through hmgA disruption or altered hpd activity) and then auto-oxidizes/polymerizes; and (3) polyketide-derived HPQ melanin in Streptomyces via rppA-dependent THN formation and oxidative coupling. Regulation is multilayered: nutrient metals (especially Cu) frequently enhance melanization; oxygen availability, nitrogen fixation regulators (e.g., NifA), redox systems (thioredoxin), stress regulators (OxyR/RpoS), and biofilm-linked transcription factors can all shift pigment output. Functionally, melanins support UV protection, heavy-metal binding, oxidative stress resistance, immune evasion, iron acquisition, electron shuttling, and interkingdom interactions—traits that can amplify persistence and virulence. Industrially, reported yields vary dramatically, with standout production in some marine Vibrio and optimized Streptomyces systems, underscoring the value of bioprospecting plus regulatory/process engineering.
| Microbiome-relevant signature | Key microbial association described |
|---|---|
| Tyrosinase/laccase-driven melanization | Streptomyces (melC operon), Bacillus (CotA laccase), Marinomonas, Pseudomonas |
| Pyomelanin from homogentisate accumulation | Pseudomonas aeruginosa clinical isolates; Vibrio cholerae; Aeromonas with hmgA lesions |
| Stress-linked induction of pigmentation | Stationary phase, heat/osmotic stress, Zn exposure, oxidative stress regulators (OxyR/RpoS) |
| High-yield bioproduction phenotypes | Optimized Streptomyces; sponge-associated Vibrio with exceptionally high titers |
Key implications
Clinically, bacterial melanin synthesis should be viewed as a persistence and virulence-adjacent trait: it can blunt oxidative killing, reshape host-pathogen interactions, and support chronic infection dynamics (notably in pigmented Pseudomonas populations). For microbiome-signature work, melanin pathways provide mechanistic biomarkers—e.g., enrichment of tyrosinase/laccase genes, homogentisate pathway disruptions, or stress-response modules tied to pigmentation—that may indicate organisms adapted to inflammatory, oxidative, metal-stressed, or biofilm-prone niches. Translationally, understanding melanin regulation could inform anti-virulence strategies (blocking pigment-mediated stress tolerance) while also enabling safe exploitation of microbial melanins for biomaterials, detoxification, and bioelectronic interfaces.
Citation
Pavan ME, López NI, Pettinari MJ. Melanin biosynthesis in bacteria, regulation and production perspectives.Applied Microbiology and Biotechnology. 2019;103:1357-1371. doi:10.1007/s00253-019-10245-y