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Adaptation in the Chernobyl Exclusion Zone: Melanin as an Energy Transducer

Glowing blue mushrooms grow on debris near a radiation sign in an industrial setting with a yellow-lit window and dark background.

Abstract


The 1986 Chernobyl disaster created a distinct ecological niche characterized by ionizing radiation fluxes lethal to most higher life forms. Yet, within the darkened, highly radioactive interior of the destroyed Reactor No. 4, a specific guild of filamentous fungi has not only survived but thrived. First documented during the "Complex" expedition of the early 1990s by researchers employing remotely operated robotic platforms, these organisms—primarily Cladosporium sphaerospermum, Wangiella dermatitidis, and Cryptococcus neoformans—exhibit a phenomenon termed "radiotropism," characterized by directional growth toward sources of beta and gamma radiation. Subsequent physiological studies suggest a mechanism of "radiosynthesis," wherein the pigment melanin functions as an energy transducer, capturing electromagnetic radiation and coupling it to cellular metabolic pathways, potentially via the reduction of NAD+ to NADH. This report provides an exhaustive analysis of the discovery, the proposed physicochemical mechanisms of fungal radiosynthesis, the evolutionary implications involving Early Cretaceous geomagnetic reversals, and the recent experimental validation of these traits aboard the International Space Station (ISS). We further explore the application of these "radiotrophic" fungi in the development of self-regenerating radiation shields for deep space exploration, critically examining the energetic feasibility and the controversies surrounding this paradigm-shifting biological capability.



1. Introduction: The Radiative Frontier of Chernobyl


The explosion of Unit 4 at the Chernobyl Nuclear Power Plant on April 26, 1986, represented a catastrophic failure of technology that inadvertently initiated one of the most significant unplanned biological experiments in history. The release of massive quantities of radioactive isotopes—including Cesium-137, Strontium-90, and Plutonium-239—created a zone of exclusion where the background radiation levels soared to orders of magnitude above the terrestrial norm.1

The immediate biological consequence was death. The pine forest surrounding the plant turned a spectral rusty red and died, earning the moniker "The Red Forest." The expectation among radiobiologists and ecologists was that the area, particularly the interior of the reactor sarcophagus (the concrete shelter hastily erected to contain the corium), would remain a sterile abiotic zone for decades, if not centuries. The radiation levels inside the sarcophagus were sufficient to hydrolyze water, generate clouds of reactive oxygen species (ROS), and shatter the genomic integrity of any organism foolish enough to enter.2

However, this assumption of sterility was fundamentally flawed. It underestimated the plasticity of microbial life and the protective and energetic potential of one of nature's most ancient pigments: melanin.

By the early 1990s, five years post-disaster, the silence of the sarcophagus was found to be teeming with life. Not the chaotic, mutated life of science fiction, but a highly adapted, specialized community of black fungi. These organisms were coating the walls of the reactor hall, swimming in the radioactive cooling waters, and growing directly on the remains of the fuel rods.2

This report aims to synthesize over three decades of research into these "radiotrophic" fungi. We will traverse from the hazardous corridors of the Chernobyl reactor to the laboratory benches of the Albert Einstein College of Medicine, and finally to the microgravity environment of the International Space Station, to understand how life has adapted to harvest the energy of the atom.



2. The Ecology of the Exclusion Zone: Discovery and Characterization



2.1 The "Complex" Expedition and the Robotic Pioneers


The discovery of fungal life inside the reactor was not made by casual observation. It was the result of the "Complex" expedition, a dedicated and perilous scientific mission initiated by Soviet (and later Ukrainian) authorities to monitor the stability of the "Elephant's Foot" (the solidified lava-like corium) and the structural integrity of the sarcophagus.1

The environment inside the reactor hall was too hostile for prolonged human presence. Radiation levels in some areas exceeded 10,000 Roentgens per hour, a dose that is fatal within minutes. To mitigate this risk, the expedition relied heavily on remote technologies.

The Robotic Vanguard:

Researchers utilized a fleet of remotely operated vehicles (ROVs). These included modified heavy machinery, such as Komatsu amphibious bulldozers, originally brought in for the exterior cleanup but adapted for remote operation to push debris and clear paths.5 More crucial for the biological discovery were smaller, specialized reconnaissance robots, such as the "Pioneer", which were equipped with cameras and sensors to navigate the labyrinthine ruins of the reactor core.7

It was through the eyes of these robots in 1991 that researchers first spotted the anomalies: patches of black slime and textured growth clinging to the concrete walls of the reactor hall and the surfaces of piping systems.2 The growth was not random; it appeared dense and vigorous, defying the radiolytic toxicity of the environment.


2.2 The Mycological Assessment


Following the robotic identification, daring sample collection missions were undertaken. Researchers, often wearing heavy lead shielding and working in intervals of seconds to minutes, scraped samples from the walls and collected water from the cooling pools.3

These samples were transferred to the Institute of Microbiology and Virology in Kyiv, where a team led by Dr. Nelli Zhdanova and Dr. Tatyana Tugai began the painstaking process of isolation and identification.2

The Isolates:

The biodiversity within the reactor was surprisingly high, yet distinctly skewed. Zhdanova’s team isolated over 200 species of fungi from the exclusion zone, but the interior of the reactor—the zone of highest radiation—was dominated by dematiaceous (dark-pigmented) fungi.3

Key species identified included:

  • Cladosporium sphaerospermum: A cosmopolitan saprotroph usually found on decaying plant matter, textiles, and painted surfaces. Inside the reactor, it was ubiquitous.2

  • Wangiella dermatitidis (also known as Exophiala dermatitidis): An opportunistic human pathogen known for causing neurotropic infections. It is constitutively melanized.11

  • Cryptococcus neoformans: An encapsulated yeast that is a significant human pathogen, particularly in immunocompromised hosts (e.g., HIV/AIDS patients). While not constitutively melanized, it possesses the enzymatic machinery (laccase) to synthesize melanin when provided with precursors like L-DOPA.11

  • Penicillium hirsutum and Penicillium roseopurpureum: Species found growing directly on "hot particles" of graphite and fuel.12

The unifying characteristic of these survivors was their pigmentation. They were not white or green like typical bread molds; they were jet black. This observation led Zhdanova and subsequent researchers to hypothesize that the pigment itself—melanin—played a functional role in their survival.2



3. Radiotropism: The Attraction to the Glow


The mere presence of fungi in a radioactive environment suggests radioresistance (the ability to survive). However, the behavior of the Chernobyl fungi suggested something far more active: radiotropism.


3.1 Directional Growth


Tropism defines a biological organism's directional growth in response to an environmental stimulus (e.g., phototropism toward light). In a series of elegant experiments, Zhdanova and colleagues demonstrated that these fungi actively grow toward sources of ionizing radiation.2

Experimental Evidence:

Fungal spores were placed in a central location on an agar plate. Sources of radiation (using isotopes like P-32 for beta radiation and Cd-109 for gamma radiation) were placed at specific vectors.

  • The Return Angle: Researchers measured the "return angle"—the angle of hyphal deviation toward the source. A significant majority of the melanized isolates, particularly Cladosporium sphaerospermum, exhibited a low return angle, indicating directional growth toward the radiation source.12

  • Carbon Exclusion: To rule out the possibility that the fungi were simply sensing a chemical gradient (chemotropism) or seeking a carbon source on the hot particles, the experiments were controlled to ensure radiation was the only variable. Even when the radiation source was collimated (a beam) and physically separated from the agar, the hyphae bent toward the beam.12

This behavior implies a sensing mechanism. The fungi were not just tolerating the radiation; they were detecting it and investing metabolic energy to reach it. This is counter-intuitive for a toxic stimulus (usually organisms display negative tropism to toxins) but perfectly logical for a nutrient or energy source.


3.2 Decomposition of "Hot Particles"


Perhaps the most startling observation was the interaction with "hot particles"—fragments of nuclear fuel and graphite ejected during the explosion. Fungi like Cladosporium cladosporioides and Penicillium roseopurpureum were observed physically overgrowing these particles.

  • Bio-etching: Microscopic analysis revealed evidence of "bio-etching" or decomposition of the radioactive substrates. The fungi were apparently breaking down the matrix of the particles.2

  • Radionuclide Accumulation: These fungi actively bioaccumulate radionuclides. This has implications for the stability of the sarcophagus, as fungal degradation could potentially mobilize radioactive dust, but it also hints at the potential for bioremediation (mycoremediation).12



4. The Mechanism of Radiosynthesis: Melanin as a Biological Transducer


If the fungi are seeking radiation, the question becomes: why? The hypothesis of radiosynthesis proposes that melanized fungi can utilize the energy of ionizing radiation to drive metabolic processes, analogous to how plants use visible light in photosynthesis.16 The key to this process is melanin. 


4.1 The Biochemistry of Fungal Melanin


Melanins are a broad class of pigments formed by the oxidative polymerization of phenolic or indolic compounds. They are chemically diverse, amorphous, and recalcitrant. In fungi, two primary pathways exist:


4.1.1 The DHN-Melanin Pathway


Used by Cladosporium sphaerospermum and Wangiella dermatitidis.

  • Precursor: Acetyl-CoA is converted to 1,8-dihydroxynaphthalene (DHN) via a polyketide synthase pathway.

  • Polymerization: DHN is polymerized into the cell wall structure.

  • Properties: DHN-melanin is typically black or dark brown and confers significant structural rigidity and protection against desiccation and lysis.10


4.1.2 The DOPA-Melanin Pathway


Used by Cryptococcus neoformans.

  • Precursor: L-3,4-dihydroxyphenylalanine (L-DOPA) or other catecholamines. C. neoformans cannot synthesize the precursor de novo; it must acquire it from the environment (e.g., from host tissue or animal waste).

  • Enzyme: The enzyme laccase (Lac1 and Lac2) oxidizes L-DOPA to dopaquinone, which spontaneously polymerizes.

  • Structure: DOPA-melanin forms a granular layer within the cell wall.17


4.2 The Physics of Interaction: Melanin as a Semiconductor


Melanin is often described as an "organic semiconductor." Its structure consists of stacked planar sheets of aromatic rings with extensive conjugated double-bond systems.

  • Electron Delocalization: This structure allows electrons to move relatively freely along the polymer chain (delocalization).

  • Radical Scavenging: Melanin contains a high population of stable free radicals. When ionizing radiation (which generates free radicals like hydroxyls in water) interacts with melanin, the polymer can absorb the energy and trap the radicals without breaking apart. This is the basis of its radioprotective function.16

However, the Dadachova/Casadevall hypothesis suggests it goes beyond protection.

  • Compton Scattering: High-energy gamma photons interact with the melanin atoms, ejecting high-energy electrons (Compton electrons).

  • Exciton Generation: The energy absorption generates electron-hole pairs (excitons) within the semiconductive matrix of the melanin.16


4.3 The 2007 "PLoS ONE" Study: Evidence for Transduction


The seminal paper supporting radiosynthesis was published in 2007 by Ekaterina Dadachova, Arturo Casadevall, and colleagues at the Albert Einstein College of Medicine.17

Methodology:

They exposed melanized and non-melanized (albino mutant) strains of C. neoformans, W. dermatitidis, and C. sphaerospermum to ionizing radiation (Cs-137 source) at dose rates approximately 500 times higher than background (similar to the Chernobyl interior).

Key Findings:

  1. Electronic Alteration: Electron Spin Resonance (ESR) spectroscopy showed that irradiation altered the electronic structure of the melanin, changing its signal intensity and spin characteristics. This proved the pigment was physically interacting with the radiation field.16

  2. Enhanced Growth: Melanized cells grew significantly faster under irradiation than non-irradiated controls. Albino mutants did not show this effect; they either grew at the same rate or were inhibited by the radiation toxicity. This linked the growth advantage directly to the presence of melanin.11

  3. Data Point: Irradiated melanized W. dermatitidis showed higher Colony Forming Units (CFUs) and dry weight biomass.

  4. Metabolic Coupling (NADH): In a cell-free system, irradiated melanin was shown to reduce NADH (Nicotinamide adenine dinucleotide) at a rate 4-fold higher than non-irradiated melanin.16

  5. Significance: NADH is a crucial electron carrier in cellular respiration (oxidative phosphorylation). If melanin can capture radiation energy and use it to reduce NAD+ to NADH, it provides a direct mechanism for feeding electrons into the mitochondrial electron transport chain to generate ATP.

  6. Nutrient Dependency: The "radiosynthesis" effect was most pronounced under nutrient-limited conditions. When glucose was abundant, the cell relied on heterotrophy. When glucose was scarce, the "nuclear battery" became a significant contributor to survival and growth.12

Proposed Model:

The researchers proposed that melanin in the cell wall acts as an antenna. It captures high-energy electromagnetic radiation, converts it into high-energy electrons/reducing power, and transfers this potential to the cell's metabolic machinery (possibly via trans-plasma membrane electron transport systems) to drive ATP synthesis and carbon assimilation.17


Table 1: Comparative Response to Ionizing Radiation



Species

Melanin Type

Growth Response to Radiation (500x Background)

Mechanism Implicated

Source

Cladosporium sphaerospermum

DHN

Positive (Increased Biomass)

Radiosynthesis via DHN-melanin antenna

2

Cryptococcus neoformans (Melanized)

DOPA

Positive (Increased CFU/ATP)

Electron transfer to NADH; Laccase-mediated

11

Cryptococcus neoformans (Albino)

None

Neutral/Negative (Radiation Damage)

Lack of protection/transduction

11

Wangiella dermatitidis

DHN

Positive (Rapid Growth)

Constitutive melanin usage

11



5. Evolutionary Origins: The Cretaceous Connection


The ability to harvest ionizing radiation seems like an adaptation to a very specific, modern horror (nuclear reactors). However, evolution works on geologic timescales. It is unlikely that fungi evolved a complex bioenergetic pathway in the mere 35 years since Chernobyl. This suggests the trait is an atavism—an ancient adaptation re-purposed.


5.1 The Magnetic Zero Hypothesis


Dr. Casadevall has proposed that the origin of this trait lies in the Early Cretaceous period (approx. 145–100 million years ago).12

The Geomagnetic Context:

During this era, the Earth experienced frequent geomagnetic reversals (the "M-sequence"). During a reversal, the Earth's magnetic field—which shields the surface from Solar Particle Events (SPEs) and Galactic Cosmic Rays (GCRs)—weakens significantly or collapses temporarily (a "magnetic zero").12

Consequently, the surface radiation flux would have been much higher than today.

The Fungal Spike:

Paleontological records from the Cretaceous show a phenomenon known as the "fungal spike"—layers of sediment rich in fungal spores and hyphae, coinciding with extinction events of plants and animals. Crucially, many of these fossilized fungi appear to be highly melanized.16

The Hypothesis:

During these periods of high radiation and ecological collapse (where dying plants and animals provided a carbon source, but competition was fierce), fungi with high melanin content had a dual advantage:

  1. Protection: They were shielded from the mutagenic effects of the cosmic rays.

  2. Energy Harvesting: They could utilize the abundant radiation flux to supplement their energy needs, allowing them to dominate the biosphere when other organisms were dying.12

Other theories mentioned in the literature include radiation from a putative passing star ("Nemesis") which might have irradiated the solar system, further selecting for radio-tolerant/trophic organisms.12 Thus, the fungi in Chernobyl are not "mutants" in the novel sense; they are ancient warriors waking up to a familiar environment.



6. The ISS Experiment: Radiotrophy in Orbit


The terrestrial findings naturally led to interest from the space exploration sector. Space is a radiation hazard zone. If biology can turn this hazard into a resource, it has profound implications for long-duration human spaceflight.


6.1 The Shunk-Gomez-Averesch Study


In 2018/2019, a research team including Graham Shunk, Xavier Gomez, and Nils Averesch sent a payload containing Cladosporium sphaerospermum to the International Space Station (ISS) to test its growth and shielding properties in microgravity.22

Experimental Design:

  • Hardware: A "split Petri dish" setup was used. One side contained agar inoculated with C. sphaerospermum; the other side was a sterile negative control (agar only).

  • Sensors: Radiation detectors (Geiger-Muller counters) were placed directly beneath each side of the dish to measure the flux of radiation passing through the fungus versus the control.

  • Monitoring: The experiment ran for 30 days.26 Images were taken every 30 minutes to track growth coverage.26


6.2 Results: Growth and Attenuation


The data returned from orbit was compelling:

  1. Growth Advantage: The fungus grew faster on the ISS than in ground controls on Earth. The specific growth rate was 1.21 ± 0.37 times higher in space.22 This confirms that the combined stress of microgravity and increased background radiation (approx. 40-80 times Earth background) acted as a stimulant, consistent with the radiosynthesis hypothesis.

  2. Radiation Attenuation: The fungal lawn, which reached a thickness of approximately 1.7 mm, attenuated a measurable amount of the incoming radiation.

  3. The Delta: The radiation levels beneath the fungus were 1.82% to 2.17% lower than beneath the negative control.28

  4. Significance: While ~2% sounds low, this was achieved by a microscopic layer of biomass. When normalized for mass and thickness, the specific attenuation capacity of the fungus (and its melanin) was comparable to or better than standard passive shielding materials.30


6.3 The Mars Shield Calculation


Extrapolating from the ISS data, the researchers calculated the thickness of a fungal shield required to protect astronauts on the surface of Mars (reducing the annual dose equivalent to Earth-like levels).

The Calculation (Linear Attenuation):

  • Pure Fungal Biomass: A layer of living C. sphaerospermum approximately 21 cm thick would be sufficient to negate the annual dose-equivalent of the Martian radiation environment.31

  • Regolith Composite: To reduce the volume and increase structural integrity, the fungus could be mixed with Martian regolith (soil). An equimolar mixture of melanin-rich fungi and regolith would require a layer of only ~9 cm.31

Comparison to Traditional Materials:

  • Regolith Only: Using pure Martian soil would require a thicker layer (approx. 12-15 cm) to achieve the same effect and lacks the self-healing property.34

  • Aluminum: Standard aerospace shielding. While effective, it produces secondary radiation (neutrons) when hit by high-energy Galactic Cosmic Rays (GCRs). Hydrogen-rich materials (like water or polyethylene) are better. Fungal biomass, being organic and water-rich, serves as an excellent high-hydrogen shield with the added benefit of active repair.35


Table 2: Radiation Shielding Efficacy Comparison (Mars Scenario)


Material

Required Thickness (cm)

Mechanism

Pros

Cons

Living C. sphaerospermum

~ 21 cm

Radical Scavenging + Mass Attenuation

Self-replicating, self-healing, ISRU compatible

Requires water/nutrients to maintain viability

Melanin/Regolith Composite

~ 9 cm

Density + Scavenging

Structural strength, lower volume

Passive (if dead biomass used)

Pure Martian Regolith

~ 12-15 cm

Mass Attenuation

Abundant

Heavy, brittle, no self-repair

Aluminum

N/A (Baseline)

Mass Attenuation

Strong structural material

Secondary neutron production, heavy launch mass



7. Controversies and Alternative Hypotheses


While the narrative of "radiation-eating fungi" is captivating, the scientific community maintains a healthy skepticism. Several researchers have critiqued the radiosynthesis hypothesis, proposing alternative explanations for the observed data.


7.1 The Walberg Critique (2015)


A significant critique comes from Eric Walberg's thesis and subsequent analysis.36 Walberg reviewed the Dadachova/Casadevall data and raised several points:

  1. Thermodynamic Insufficiency: Calculations suggest that the total energy deposited by the radiation doses used in the experiments (and present in Chernobyl) is thermodynamically very low compared to the chemical energy in even a small amount of glucose. Critics argue the energy is insufficient to drive the biomass accumulation observed if it were the sole energy source.38

  2. Stress Response vs. Energy: Walberg proposed that the enhanced growth is a "hormetic" stress response. The radiation causes low-level damage. The cell responds by upregulating repair mechanisms (autophagy, protein synthesis). If nutrients are available, this "overcompensation" results in faster growth, not because the radiation provides energy, but because it triggers a survival overdrive.36

  3. Nutrient Availability: Critics noted that in some "starvation" experiments, the media still contained agar (a polysaccharide) or trace nutrients. The radiation might have chemically altered the agar, making the carbon more bioavailable to the fungi, rather than the fungi using the radiation directly.37


7.2 The Carbon Fixation Gap


Photosynthesis involves two things: energy capture (light to ATP/NADPH) and carbon fixation (CO2 to sugar).

Radiosynthesis, as currently described, only addresses the first half (Energy capture/NADH reduction). There is no evidence yet that radiotrophic fungi can fix atmospheric carbon dioxide using radiation energy.12

They remain heterotrophs (or organotrophs). They need a carbon source. Therefore, "radio-stimulated organotrophy" might be a more accurate, albeit less catchy, term. The radiation provides the ATP "turbo boost" to hunt for and digest scarce carbon sources more efficiently.


7.3 Casadevall’s Rebuttal


In response, the Dadachova/Casadevall team argues that the magnitude of the growth enhancement (often 3-4 times higher) is difficult to explain via hormesis alone, especially since albino mutants (which suffer the same stress) do not show the response. The specificity of the NADH reduction by irradiated melanin in cell-free systems remains a strong biophysical argument for actual energy transduction, even if the complete metabolic pathway is not yet fully mapped.12



8. Broader Implications: From Earth to Europa


The validation of radiotrophy, even if partially strictly a radioprotective/metabolic boost phenomenon, opens up vast avenues for application.


8.1 Bioremediation (Mycoremediation)


The ability of these fungi to grow on radioactive substrates makes them ideal candidates for cleaning up nuclear waste.

  • Bio-accumulation: Fungi like C. sphaerospermum can be grown on radioactive waste. As they grow, they incorporate radionuclides (Cesium, Strontium) into their biomass.

  • Harvesting: The fungal mats can then be harvested and vitrified (turned into glass) for safe storage, significantly reducing the volume of the waste compared to treating thousands of gallons of contaminated water or tons of soil.39

  • Hot Particles: Their ability to "etch" and break down fuel particles could speed up the decomposition of dangerous debris inside reactors, though this must be managed to prevent airborne dispersion.15


8.2 In-Situ Resource Utilization (ISRU) for Space


The "Moon to Mars" vision relies on ISRU. We cannot carry everything.

  • Myco-Architecture: The ISS study proposes growing habitats. A small payload of spores and a nutrient solution could be sent to Mars ahead of the crew. Upon landing, the system mixes the spores with Martian regolith and waste water, growing a thick, melanin-rich dome. When the astronauts arrive, their radiation-shielded home is ready and waiting.40

  • Self-Healing Suits: Melanin could be incorporated into spacesuits. If the suit layer is damaged, a layer of dormant spores could be activated to "grow back" the shielding integrity (biologically active materials).22


8.3 Astrobiology and the Search for Life


Finally, this research expands the definition of the "Habitable Zone."

  • Rogue Planets: Planets wandering in interstellar space, far from any star, were thought to be dead. But if they have a hot, radioactive core (geothermal/nuclear energy), radiotrophic life could exist on their surface or in their crust.

  • Icy Moons: Europa (Jupiter) and Enceladus (Saturn) are bathed in intense radiation belts from their gas giants. The surface of Europa is bombarded by particles that would kill a human instantly. However, for a radiotrophic organism, the surface of Europa isn't a hellscape; it's a banquet. This prioritizes the search for melanized biomarkers in future missions to these worlds.25



9. Conclusion


The black fungi of Chernobyl—Cladosporium, Wangiella, Cryptococcus—represent a stunning example of biological resilience and innovation. In the heart of a nuclear disaster, where human technology failed and the environment became lethal, life adapted. By harnessing the ancient, semiconductive properties of melanin, these organisms transformed the "death ray" of ionizing radiation into a source of metabolic vitality.

Whether strictly "radiosynthetic" in the thermodynamic sense or highly efficient "radio-stimulated" scavengers, their existence challenges our understanding of bioenergetics. From the "Complex" expedition robots that first saw them, to the ISS modules where they are now tested, these fungi are guiding humanity toward new biotechnologies. They offer a path to clean up our nuclear legacy on Earth and a shield to protect our future explorers on Mars. As we gaze out at the radioactive void of the cosmos, we may find that the dark, melanized life forms are not the exception, but the rule for survival in the high-energy universe.



Appendix: Detailed Data Tables



Table 3: Summary of Key Research Expeditions and Studies



Year

Event/Study

Key Personnel/Robots

Major Finding

Source

1991

"Complex" Expedition

Nelli Zhdanova, Tatyana Tugai; Robots: Komatsu, Pioneer

Discovery of black fungi on Reactor 4 walls and in cooling pools.

1

2007

PLoS ONE Paper

E. Dadachova, A. Casadevall

Lab proof of concept: Enhanced growth under radiation, NADH reduction by melanin.

16

2016

JPL/ISS Payload

K. Venkateswaran

Eight species sent to ISS to observe reaction to space radiation.

2

2018-19

ISS "Myco-Shield"

G. Shunk, X. Gomez, N. Averesch

C. sphaerospermum growth and attenuation study; 21cm shield calculation.

22


Table 4: Fungal Melanin Biosynthetic Pathways



Pathway

Primary Precursor

Key Enzyme

Species Example

Characteristics

Source

DHN

Acetyl-CoA (Endogenous)

Polyketide Synthase (PKS)

Cladosporium sphaerospermum, Wangiella dermatitidis

Constitutive, structural, high radioprotection.

10

DOPA

L-DOPA (Exogenous)

Laccase (Lac1, Lac2)

Cryptococcus neoformans

Facultative (requires substrate), granular, virulence factor.

17

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