INDEPENDENT RESEARCH | Isabella Victa

Summer 2026 - INDEPENDENT RESEARCH PROJECT

Lab Report: Household Surface Contamination

Instructor Guide:

Sarika Robinson (Science, Artificial Intelligence, Northgate High School)

What was being tested in this lab? Give a brief summary of the procedures
and your findings.

This lab tested which everyday surfaces were the least and most contaminated. The lab
procedures consisted of swabbing the tested surfaces and creating bacteria colonies from the
various surfaces. To get the most accurate data a few agar plates were left open in each room for
the same amount of time to test how clean the air of the room was. Overall, the toilet and shower
ended up being the most contaminated with about 400+ colonies on the toilet agar plate and 300+
colonies grown on the shower agar plate. The least contaminated surface was the steering wheel
of the car resulting in only 3 bacteria colonies grown on the agar plate.

What was the independent and dependent factor? What was the control
group? What were the constants in the lab?

The independent factor in the lab is the surfaces that were being tested. The dependent factor is
the amount of bacteria colonies that grew on the agar plates. There was an air control group to
test if the air from the various rooms affected the agar plates while gathering the samples. In
addition, there was a negative control which consisted of an unopened agar plate testing if the
agar plate was contaminated and to compare the experimental group to it. Constants included the
time in which the agar plates were opened when gathering the air control group data, the time
each agar plate had to grow bacteria colonies, and the temperature at which the plates were
stored.

aminated.

Based on the data collected, which surface contained the most bacteria? And
why do you think so? Which room in the house contained the most bacteria
overall?
The toilet contained the most bacteria with an agar plate containing 400+ colonies of various
sizes. This is most likely because the toilet is used for disposing of feces and other waste from the
human body which contains most various germs making the toilet the most unsanitary. This is
especially true when the toilet is being used by various people throughout the day without being cleaned. The bathroom contained the most bacteria overall because while the toilet contained the
most bacteria the shower handle comes second place with 300+ bacteria colonies. The bathroom
also contained the most bacteria because the air was also contaminated which is shown from the
bathroom air-control which consisted of 6 bacteria colonies while the other air-control plates had
0-1 bacteria colonies.

Based on your previous answer, what can be done to keep those surfaces less
contaminated?
To keep the toilet and shower less contaminated is to consistently clean both surfaces at least
once every other day or week to prevent further bacteria growth or contamination on each
surface. In addition, because the bathroom air-control plate grew bacteria as well it most likely
influenced the amount of bacteria on the surfaces. To make the air more clean, ventilating the
bathroom and maybe adding an air purifier would improve the air quality.

What errors may have occurred during the lab that caused the data to be
imprecise or inaccurate?
Some errors that may have occurred include swabbing some surfaces more thoroughly than
others which may cause more bacteria growth on certain plates. In addition, when swabbing the
bacteria colonies onto the plates they weren't all at the same time which gave some plates a little
more time to grow, but only by a few minutes which shouldn't have a great affect on the data.
When counting the bacteria colonies some colonies were merely tiny dots which were barely
visible, so the data collected may be wrong depending on how visible the bacteria colony was to
my naked eyes.

Formulate a hypothesis/ claim about this lab and use evidence and reasoning
to back it up.

If household surfaces are being tested for bacterial growth then areas that are touched most
frequently such as the toilet or fridge and keyboard will contain the most bacteria colonies. This
can be seen with the toilet agar plate which contained over 400+ colonies by the second week and
fourth day. The toilet was shared among various family members and was used the most
frequently all together resulting in the most bacterial growth on the plate. In addition, the fridge
handle contained 83+ visible colonies which is the third most contaminated surface according to
how many colonies grew on its agar plate. The fridge handle is another most commonly touched
surface whenever a person eats or even grabs a snack the fridge is touched which results in it
having one of the most bacteria colonies. The keyboard is another most frequently used item and

contains over 81+ bacteria colonies in comparison to the actual desk which only grew 20
colonies. In other words, because the keyboard is used constantly and cleaned less often, naturally
it will contain more bacteria versus a surface that is used less frequently. Overall, there was a
trend in the data that proves more frequently touched surfaces are the most contaminated.

Additional Photos from findings

The following photos were taken using a microscope at 40x and 100x Magnification and a digital camera with a microscope attachment. Photos were then vetted through several image recognition applications including Gemini, Chat GPT, and AI Cell Profiler. Final Identification and description are based on average results over 5 attempts each. Samples were applied to slides.

SHOWER

Bdelloid Rotifer

Elongated, Segmented Body: The body is telescopic and worm-like, tapering toward the posterior end.
Foot and Toes: At the rear (bottom right), you can see the characteristic toes or spurs used by bdelloid rotifers to anchor themselves to surfaces.
Corona/Head Structure: At the anterior end (top left), the retracted or semi-contracted corona is visible, which typically features cilia used for locomotion and filter-feeding.

DESK

Colonial Micoalga

Colonial Aggregation: Instead of single free-swimming cells, the organism forms an interconnected cluster or subcolony held together by a mucilaginous matrix.
Lobed/Botryoidal Morphology: The individual cells or groups are tightly packed in rounded, bulbous lobes that give it a characteristic multi-lobed or branching outline under light microscopy.
Pigmentation: The dark, dense internal structure reflects the chloroplast clusters packed within the cellular matrix.

AIR CONDITIONER CONTROLS

Testate Amoeba

Distinct Shell/Test: A clear outer boundary or test encases the central protoplasm, which is characteristic of testate amoebas that construct or secrete protective micro-shells.
Compact Morphology: The rounded body shape with a slightly narrowed anterior aperture region is typical of various freshwater testate amoeba species (such as Arcella or Lecquereusia variants seen from an apical or angled view) or encysted protozoans protecting themselves under unfavorable conditions.

MY KEYBOARD

Fungal Mycelium and Spore structures

Hyphal Network: Fine, branching, thread-like filaments (hyphae) stretch across the background, which form the structural body (mycelium) of a fungus.
Aggregated Clusters / Sporulating Bodies: The dense, darkened, and lobed central masses represent clustered spores or developing fruiting structures connected to the hyphal network.

DAD'S KEYBOARD - Sample #1

Myxomycete (Slime Mold)

Plasmodial Veins: The thick, branching, interconnected channels form the protoplasmic network through which cytoplasm actively streams (cytoplasmic streaming).
Translucent Matrix: The smooth, semi-transparent membranes surrounding the channels are typical of a plasmodium moving across a surface to engulf nutrients, bacteria, or yeast.

DAD'S KEYBOARD- Sample #2

Saccharomyces or Bacillus Bacteria

Radial/Symmetrical Pattern: The colony expands outward from a central point, developing distinct channels, spokes, or folds that radiate toward the perimeter.
Marginal Growth: The edge shows dense cellular accumulation with regular undulations, typical of structured microbial growth on a solid or semi-solid substrate

TOILET

Filamentous Fungi and empty testate amoebae shells

Radiating Hyphae: Fine, branching, thread-like hyphae extend outward symmetrically from a central point of origin where the spore or inoculum initially germinated.
Mycelial Mat Formation: The dense, darker core consists of tightly packed initial growth, while the finer, branching tendrils at the periphery represent active hyphal extension searching for nutrients.

REFRIGERATOR

Actinobacteria

Dense Filamentous Mass: The microscopic tangle consists of extremely fine, branching filaments or rods that form an opaque, textured mat typical of certain filamentous bacteria (such as Actinomyces or Streptomyces) or early-stage fungal mycelium.
Compact Growth Zone: The well-defined boundary and granular surface structure indicate a tightly packed colonial growth rather than free-swimming single-celled microorganisms.

CHAIR HANDLE

Plasmodium (microbial biofilm)

Reticulated Web/Matrix: Dark, fibrous strands weave together to form enclosed channels and pockets, characteristic of a mature extracellular polymeric substance (EPS) matrix produced by a microbial community or the advancing veins of a slime mold.
Cellular Pockets: The translucent, rounded lacunae (spaces) enclosed by the dark webbing represent areas where microorganisms or fluid channels are concentrated within the matrix.

Instructor Response:

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