Kiana Sedighi

Home for Two: A Slime Mold Coexistence Experiment

Introduction

For my final DIY BioLab project, I wanted to create an experiment that was both biological and narrative. Instead of only observing the growth of one slime mold, I wanted to place two different slime mold species in the same environment and document what happened when their growing networks approached each other.

The two organisms used in this experiment were Badhamia and Physarum polycephalum. At the beginning, both looked very similar because they were yellowish, which made it difficult to visually separate them during observation. Because of this, I later used a red pigment on the food source of one culture to create a visible contrast.

My final goal was to create a time-lapse video showing the interaction between the two slime molds. I wanted the project to ask a simple question:

Can two different living organisms share the same space?

Materials

For this experiment I used:

• Badhamia culture
• Physarum polycephalum culture
• Agar-agar
• Water
• Petri dishes
• Oat flakes
• Red pigment / coloring powder
• Laboratory glassware
• Spoon
• Tweezers
• Gloves
• Microscope / camera setup
• Canon DSLR camera
• Python
• Video editing software

Preparing the First Badhamia Culture

Badhamia

At the beginning of the project, I prepared a simple agar medium for the slime mold.

I mixed agar-agar with water, heated it until the agar dissolved, and poured the liquid into a Petri dish. After the agar cooled down and became solid, I transferred Badhamia from the kit that was ordered for me by our lab supervisor Mr. Volpato.

I placed several oat flakes on the agar as food and left the culture to grow. This first step was mainly about keeping the Badhamia alive and giving it enough time to become stronger before using it in the final experiment.

Badhamia kit

Receiving the Second Slime Mold

After the Badhamia culture had started growing, I contacted another student and exchanged slime mold cultures with her. I gave her part of my Badhamia culture, and she gave me Physarum polycephalum.

The Problem of Visibility

Color Physarum polycephalum

At first, both cultures were yellowish and visually very similar. This was a problem because once they started growing on the same agar plate, it would be difficult to tell which slime mold was which.

P1. Food coloring

Because of this, I looked at a previous experiment done by Daria Lukianchuk, who had tested different coloring methods. In her experiment, an unknown red pigment had produced the clearest visible result. I used this information as a practical reference for my own setup.

Instead of repeating the full color-testing process, I decided to use the same red pigment to color the food source of one slime mold. This made the two sides easier to distinguish in the final video. Then I prepared the food as she mentioned.

P2. Food coloring

Preparing the Final Petri Dish

For the final experiment, I prepared new agar plates.

Preparing the Final Petri Dish

I again mixed agar-agar with water, heated the mixture, and poured it into a clean Petri dish. After the agar solidified, I transferred both slime molds onto the same plate.

One side contained Badhamia, and the other side contained Physarum polycephalum. This setup became the central scene of the project: two different organisms, one shared environment.

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Camera Setup and Time-Lapse Recording

Camera Setup and Time-Lapse Recording

To document the experiment, I used a fixed camera setup.

The camera was mounted above the Petri dish and under it a power source so that it could record for several hours without interruption. I configured the camera to take one photo every 10 seconds.

This interval was chosen because it created enough frames for a smooth time-lapse, while still keeping the number of images manageable.

During the recording session, the camera captured thousands of photographs of the slime molds.

Creating the Video with Python

After the recording session, I transferred the images to my computer.

The folder contained both image files and raw camera files, so I used only the JPG images for the final processing. I wrote a Python program to load the images in order, align them, remove problematic outsider frames when necessary, and combine the sequence into a video.

import cv2
import os
import glob
import numpy as np

# SETTINGS
FPS = 30
OUTPUT = "timelapse_aligned.mp4"
IMAGE_EXT = "*.JPG"

# Read JPG files only
files = sorted(glob.glob(IMAGE_EXT))

if not files:
    raise Exception("No JPG files found in this folder.")

print(f"Found {len(files)} JPG images")

# Use first image as reference
ref = cv2.imread(files[0])
ref = cv2.resize(ref, (1920, 1080))
ref_gray = cv2.cvtColor(ref, cv2.COLOR_BGR2GRAY)

h, w = ref.shape[:2]

video = cv2.VideoWriter(
    OUTPUT,
    cv2.VideoWriter_fourcc(*"mp4v"),
    FPS,
    (w, h)
)

last_good = ref.copy()

for i, file in enumerate(files):
    img = cv2.imread(file)

    if img is None:
        print("Skipped unreadable:", file)
        continue

    # Fix portrait/rotated outsiders automatically
    if img.shape[0] > img.shape[1]:
        img = cv2.rotate(img, cv2.ROTATE_90_CLOCKWISE)

    img = cv2.resize(img, (w, h))
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    # Align image to first image
    warp_matrix = np.eye(2, 3, dtype=np.float32)

    try:
        _, warp_matrix = cv2.findTransformECC(
            ref_gray,
            gray,
            warp_matrix,
            cv2.MOTION_EUCLIDEAN,
            criteria=(cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 50, 1e-5)
        )

        aligned = cv2.warpAffine(
            img,
            warp_matrix,
            (w, h),
            flags=cv2.INTER_LINEAR + cv2.WARP_INVERSE_MAP
        )

        video.write(aligned)
        last_good = aligned

    except cv2.error:
        # If alignment fails, probably outsider / bad photo
        print("Skipped outsider or badly rotated image:", file)
        continue

    if i % 100 == 0:
        print(f"Processed {i}/{len(files)}")

video.release()
print("Done:", OUTPUT)

The final time-lapse was created from the image sequence and exported as an MP4 file. After that, I edited the video further by adding an intro, title cards, music, and an ending message.

Artistic Concept

The original concept of the video was Home for Two. I wanted to present the two slime molds almost like two characters sharing one space:

One — Badhamia

Two — Physarum polycephalum

However, after discussing the experiment with our lab supervisor, I realized that my first interpretation was not good. Since both slime molds depend on the same food source, the situation is not simply peaceful coexistence. It is also competition.

In the actual experiment, the two organisms also did not grow as expected. Because of this, the biological part of the project cannot be presented as a successful coexistence experiment. Still, I decided to continue working with the material visually.

For the next attempt, I want to develop the video concept in a more playful direction: not as a peaceful home, but more like a small battlefield, where two organisms compete for space and food.

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Conclusion

This project started as an attempt to create a poetic slime mold film about two different organisms sharing one space. The idea behind Home for Two was to connect biological observation with a wider reflection on difference and coexistence.

However, the experiment did not work in the way I expected. The two slime molds did not grow strongly, and after feedback from our lab supervisor, I understood that the concept of peaceful coexistence was biologically too simplified. Since both organisms use the same food source, their relationship is more competitive than harmonious.

Because of this, I now see the project as an unfinished first attempt rather than a successful final experiment. I still learned how to prepare agar plates, maintain slime mold cultures, exchange biological material, use colored food as a visual marker, build a time-lapse setup, and turn thousands of photos into a video using Python.

For the next version, I want to repeat the experiment with a stronger setup and change the artistic direction. Instead of presenting the slime molds as peacefully living together, I want to show them in a more playful and dramatic way: as two organisms entering the same arena, competing for food and space.

The failure of the first experiment therefore becomes part of the project. It shows how an artistic idea can meet biological limits, and how the concept can evolve after understanding what actually happens.

Introduction

For the second stage of this project, I wanted to explore the interaction between two slime mold species under shared environmental conditions. Instead of focusing on coexistence, this experiment investigates how two organisms respond when they compete for the same resources.

The two species used are Badhamia and Physarum polycephalum. Both are plasmodial slime molds that forage by expanding dynamic networks toward food sources. Because they rely on similar nutrients, placing them in the same Petri dish creates a situation in which their growth patterns and interactions can be directly observed.

As in the first experiment, one food source was colored with red pigment to make the two organisms easier to distinguish during time-lapse recording.

The experiment was documented using automated photography. The resulting image sequence will be processed into a time-lapse film, allowing the interaction between the two slime molds to be observed over time.

Rather than asking whether the organisms can peacefully share a habitat, this experiment asks a different question:

How do two slime molds behave when they compete for the same space and food?