Flora Funga Podcast

Fungi and the electromagnetic spectrum

From counting x-ray photons to reading mushrooms

KK with Matthew Getzin · 09/30/2026

Matthew Getzin holding a large hen-of-the-woods

Introduction

Who is Mushroom Matthew?

Training

PhD in Biomedical Engineering from Rensselaer Polytechnic Institute '19
Thesis: Photon-Counting X-ray Computed Tomography

Post graduate work

X-ray physics for GE HealthCare's deep-silicon photon-counting CT

OPEN TO WORK

Available now for data science, AI and imaging-physics roles, while building myco.ai and AI tools

Fungi

Self-started foraging over 10 years ago after "chance" encounters with fungi in the wild · founder of myco.ai

Matthew Getzin holding two large mushrooms in the forest

Matthew as a child holding a giant puffball

Sources: [1] · full list at the end

Light meets matter

Six things a photon can do when it hits matter

Pass through

Transmission

An x-ray image is a shadow of what got through.

Bend

Refraction

A lens slows light and bends it to a focus; no energy lost.

Bounce

Elastic scatter

Same wavelength out: why a white mushroom looks white.

Get absorbed

Photoelectric

The photon vanishes; its energy frees an electron (lead K shell, 88 keV).

Re-emerge

Fluorescence

The gap refills and a new, lower-energy photon leaves.

Share its energy

Compton scatter

It kicks an electron and leaves with a longer wavelength.

What wins depends on photon energy and the electron's orbital: a tight K shell needs keV, a spread-out pigment orbital a few eV, and melanin's overlapping bands absorb every color.

Sources: [2–5] · full list at the end

Light as particles

Light arrives in packets called photons

Gamma

X-ray

UV

Infrared

Microwave and radio

400 nm

700 nm

Visible, the sliver we see

← Shorter wavelength, more energy

Longer wavelength, less energy →

E = hf = hc/λ

E (eV) ≈ 1240 ÷ λ (nm)

Brightness is how many photons arrive; color is the energy of each one.

Band	Wavelength	Frequency	Photon energy
Gamma	< 0.01 nm	> 3×10¹⁹ Hz	≳ 100 keV
X-ray	0.01–10 nm	3×10¹⁶–3×10¹⁹ Hz	0.1–100 keV
Ultraviolet	10–400 nm	7.5×10¹⁴–3×10¹⁶ Hz	3.1–124 eV
Visible	400–700 nm	4.3–7.5×10¹⁴ Hz	1.8–3.1 eV
Infrared	700 nm–1 mm	3×10¹¹–4.3×10¹⁴ Hz	0.001–1.8 eV

Sources: [6, 7] · full list at the end

X-rays · the energy scale

Same photons, 40,000× the energy

Sources: [2, 3, 8] · full list at the end

The bridge

Same question, new subject: what happens when a photon meets matter?

In a detector, we measure it. In a mushroom, evolution uses it.

The electromagnetic spectrum · three fungal stories

Energy decides what a photon does

1 eV

10 eV

100 eV

1 keV

10 keV

100 keV

1 MeV

β-carotene 2.8 eV

water ionizes 12.6 eV

Pb K edge 88 keV

Cs-137 γ 662 keV

Visible · 1.8–3.1 eV

Lifts an electron

β-carotene's 2.8 eV gap absorbs blue; the electron stays bound

Pigment colors, glowing mushrooms, fungal light sensing

Ultraviolet · 3.1–124 eV

Breaks bonds

From about 10 eV, photons can tear electrons off molecules

Vitamin D in mushrooms; light-powered DNA repair

X-ray and gamma · keV–MeV

Knocks one out

Lead's 88 keV K edge; refilling the hole emits a 75 keV x-ray

Melanized molds at Chernobyl; fungi that mineralize lead

Sources: [2, 3, 8–11] · full list at the end

The episode

Six stops, from settled chemistry to open questions

01

Color

Which molecules paint mushrooms

02

Glow

How fungi make light

03

UV

Vitamin D, sunscreen, repair

04

Seeing

Fungal eyes and ours

05

Melanin

Fungi, skin and brain

06

Radiation

Chernobyl to the ISS

Settled chemistry

Hypothesis and open questions

Into the visible · subtractive color

Color is the light a pigment leaves over

Sources: [9, 12–16] · full list at the end

Stop 1 · Color · knob 1

Spread-out electrons set a mushroom's color

Beta-carotene structure with its 11 conjugated double bonds highlighted in amber

Alternating single and double bonds share one electron cloud

Longer cloud, smaller energy step, longer wavelength absorbed

Beta-carotene: 11 double bonds, absorbs blue, looks orange

Knob one: runway length. But each extra double bond helps less and less; next, a shortcut.

Sources: [9, 17] · full list at the end

Stop 1 · Color · knob 2

Push–pull beats length

Plain chain: longer, slowly redder

β-carotene needs 11 double bonds just to reach blue (450 nm).

Push–pull chain: the shortcut

N pushes, N⁺ pulls, bonds even out: 3 double bonds reach green.

200

300

400

500

600

700

2

4

6

8

10

12

Double bonds in a row

nm absorbed ↑

● push–pull chains

● plain chains

β-carotene 450

chanterelle 470

betalamic acid 414

fly agaric red 542

On the rainbow: the chanterelle is a long plain chain; the fly agaric is a short push–pull chain, and it wins.

Sources: [12, 17–19] · full list at the end

Stop 1 · Color · knob 3

Same atoms, different color

Naphthalene

C10H8 · colorless · mothballs

Azulene

C10H8 · deep blue · core of Lactarius indigo's pigment

Naphthalene's electrons spread evenly. Azulene's odd rings pull them lopsided: the 5-ring gains charge, the 7-ring loses it, and the jump to the first empty orbital shrinks enough for yellow light (≈580 nm).

Sources: [15, 20] · full list at the end

Into the visible · warm colors

Warm colors: red, orange and yellow

Canthaxanthin structure with its long conjugated chain highlighted

Absorbs ≈420–530 nm → orange

Orange · Chanterelle

Long runway: 13 double bonds, but plain chains redden slowly

Underside of a chanterelle showing its ridged false gills

Sources: [12, 13, 19, 21, 22] · full list at the end

Fly agarics with red caps and white warts

Betanidin, the core of the fly agaric red betacyanins: the NH (blue) pushes electrons along a short chain to the N+ (red), which pulls, with an extra benzene ring on the N+ end

Absorbs ≈440–570 nm → red

Red · Fly agaric

Push–pull: N pushes, N⁺ pulls; 3 double bonds reach green

Variegatic acid structure with its conjugated system highlighted

Absorbs ≈380–480 nm → yellow

Yellow · Bolete

Shorter runway: a smaller cloud, so it stops at blue

Photo by Clarissa Arana

Sources: [13–16] · full list at the end

Into the visible · cool colors

Cool colors: green, blue and violet

Xylindein: OH groups (blue) push electrons, C=O groups (red) pull, across a flat sheet of fused rings

Absorbs ≈590–700 nm → blue-green

Green · Green elfcup

Sheet + push–pull: eight fused rings; OH pushes, C=O pulls

Absorbs ≈530–640 nm → blue

Blue · Indigo milk cap

Shape: lopsided 7+5 rings, same atoms as colorless naphthalene

Iron bound to beta-DOPA: the catechol oxygens (blue) hand an electron to iron (red)

Absorbs ≈500–620 nm → violet

Violet · Violet webcap

Charge transfer: the catechol hands an electron to iron

Into the visible · color on demand

Why mushrooms bruise blue

Sources: [13, 23–25, 67] · full list at the end

Bolete flesh staining dark blue where it was cut

Why blue?

Probably a side effect, not a signal.

Injury lets enzymes reach pigments kept apart in intact cells.

Variegatic acid may feed iron to wood-rot chemistry [24]; disputed [67].

Sources: [26] · full list at the end

Into the visible · the extremes

Black and white: absorb everything, or nothing

Brown hen-of-the-woods at the base of a tree

Dark, shaggy-capped bolete held in a hand

DHN, the building block of fungal melanin

DHI, the building block of human eumelanin

Many overlapping bands → black

Black · Melanized fungi

Every gap at once: a jumble of units, chain lengths and stacks, each absorbing its own color; together, all of them

White lion's mane fungus on a tree trunk

White Amanita mushroom with a ringed stem

Absorbs nothing → white

White · Button mushroom

No chromophore: hyphae and air pockets scatter every color back

After absorption

An excited electron has five ways out

Next stops: Glow runs 02 on chemistry · UV uses 03 and 04 · Seeing uses 03 · Melanin is 01.

Sources: [27–30] · full list at the end

Sources: [31–34] · full list at the end

Stop 2 · Glow

Glow: chemistry does the exciting

Red circles: what changes at each step. Losing CO₂ pays for the photon (≈2.4 eV).

1 · Build the fuel

Caffeic acid

→

+ ring

Hispidin

→

+ OH

3-OH-hispidin (fuel)

2 · Burn it for light

The fuel's ring with an O–O bridge across it, circled; Ar is the unchanged catechol arm

O–O ring (unstable)

→

− CO₂

Caffeylpyruvic acid*

→

light

green light ≈520 nm

Fungal mycelium glowing green in the dark

Photos by Tyler Brunner

Stop 3 · UV

UV: damage, defense and vitamin D

UV photons carry 3–4+ eV: enough to break and rearrange bonds, not just lift electrons.

Sources: [10, 11, 35, 36] · full list at the end

Stop 4 · Seeing

Seeing: fungi sense light with our toolkit

Three chromophores we share with fungi, flavin, retinal and a bilin, plus one lens.

Sources: [30, 37–43] · full list at the end

Stop 5 · Melanin

One pigment, three places

Same chemistry everywhere: soak up light, return it as heat, mop up radicals.

Sources: [26, 44–46] · full list at the end

Stop 6 · Ionizing radiation

Five kinds of radiation, five kinds of armor

Radon: the alpha you breathe

Radium in soil decays into radon gas that seeps into basements. Skin blocks its alphas, but breathed in, radon and its decay products fire them straight into lung tissue.

Ra-226 → Rn-222 (gas, 3.8 days) → Po-218 → Po-214 → … Pb-210

Sources: [47–51] · full list at the end

Stop 6 · Ionizing radiation

From solid ground to open question

“Radiation-stimulated” is accurate; “eats radiation” is not.

Hypothesis

“Radiosynthesis”: fungi harvest usable energy from radiation [56]

Suggestive

On the ISS: growth 1.21× (±0.37) ground; ≈2% fewer counts under the mat [57, 64]

Well supported

Radiation alters melanin's electrons; melanized fungi grow faster at ≈500× background [55]

Established

In 18 of 27 tests, soil fungi grew toward beta and gamma sources [54]

Established

Melanized fungi dominate Chernobyl's damaged reactor rooms [53]

Sources: [52–57] · full list at the end

Stop 6 · Uptake

Fungi soak up the soil, radioactive or not

S

K

Ca

V

Fe

Se

Sr

Cd

Cs

Hg

Pb

Ra

U

actinide

radioactive isotope of concern

nutrient being copied

Poses as a nutrient

Cs-137 sneaks in as potassium [68]; radium and Sr-90 as calcium

Grabbed on purpose

The fly agaric builds amavadin to hoard vanadium; siderophores fetch iron [59]

Sticks to wall and melanin

Lead, cadmium and mercury cling to chitin and melanin; cesium to a cap pigment [58, 60]

Turned into a mineral

Lead becomes pyromorphite; uranium becomes uranyl phosphate [61–63]

Swallow a radioactive element and the fungus becomes its own radiation source.

Sources: [58–63, 68] · full list at the end

Medical physics sidebar · hypothesis

Lead stops x-rays. Could metal-loaded fungi?

Stopping power per gram

100 keV x-rays

mycelium

1×

+1% lead

1.3×

+10% lead

4.2×

pure lead

33×

1 MeV gamma

mycelium

1×

+1% lead

1×

+10% lead

1×

pure lead

1×

Photoelectric absorption climbs with atomic number; at gamma energies Compton wins and every material is ≈ equal per gram. A 1.7 mm fungal lawn blocks ~1–2% at 662 keV.