Cladosporium sphaerospermum is a species of mold that is widespread across the globe. First described in 1886, this fungus is a member of the common Cladosporium genus. It is characterized by darkly pigmented colonies in shades of olive-green, brown, or black, with a velvety or powdery texture from melanin in the cell walls.
This mold reproduces asexually, allowing it to spread efficiently. It is known for its slow growth and ability to tolerate a wide range of environmental conditions, including low temperatures and high salt concentrations, which contributes to its prevalence.
Common Habitats
Outdoor Environments
Cladosporium sphaerospermum is commonly found in the natural environment as a saprotroph, breaking down dead organic material. It colonizes soil and decaying plant matter, such as leaves and stems, and can also live on living plants as a secondary invader of dying tissue. Its airborne spores are distributed widely, making it a regular component of outdoor air samples. The fungus is adaptable to various climates, from temperate to tropical, and can grow at temperatures as low as -5°C (23°F), which explains its widespread distribution.
Indoor Environments
Indoors, the presence of C. sphaerospermum often signals a moisture problem, as it thrives in damp and humid areas like bathrooms, kitchens, and basements. The fungus can grow on many building materials when moisture is present, including painted walls, wallpaper, wood, and textiles like carpets and mattress dust. HVAC systems can become reservoirs for this mold, distributing its spores throughout a building. Window frames and sills are another frequent location for growth, as condensation provides the necessary moisture.
Health Implications
The most common health issue associated with Cladosporium sphaerospermum is its role as an allergen. For sensitive individuals, airborne spores can trigger allergic reactions resembling hay fever. These symptoms can include sneezing, a runny or stuffy nose, itchy and watery eyes, and a cough. Exposure can also lead to skin irritation, such as dryness or hives.
In people with asthma, exposure to this mold can be problematic, potentially causing asthma attacks or worsening existing respiratory symptoms. Symptoms of an asthma flare-up triggered by the mold can include wheezing, chest tightness, and difficulty breathing. Higher concentrations of spores in the air are more likely to provoke a reaction.
While primarily known as an allergen, C. sphaerospermum can, in rare instances, act as an opportunistic pathogen. This means it causes infections in individuals with severely weakened immune systems. Reported infections are uncommon but can affect the skin, eyes, sinuses, and, in very rare cases, the brain or lungs. For the general population, the risk of infection is very low, with allergic responses being the primary health concern.
Identification and Remediation in Buildings
Visually, Cladosporium sphaerospermum appears as dark spots that are olive-green, brown, or black with a velvety or powdery texture. It grows in patches on surfaces prone to moisture, and its presence may be indicated by a persistent musty odor in a poorly ventilated area.
For small areas of growth, homeowners can perform the cleanup. It is recommended to use protective gear, including gloves, goggles, and a mask, to avoid inhaling spores. The affected area can be cleaned with a mixture of detergent and water. Ensuring the area is well-ventilated during and after cleaning helps disperse airborne spores.
Larger infestations, or those embedded within materials like drywall, require professional remediation. Professionals have the equipment and expertise to safely remove the mold and address the underlying moisture source. After remediation, preventing regrowth is centered on moisture control. This includes fixing leaks promptly, ensuring proper ventilation, and using dehumidifiers to keep indoor humidity below 50%.
Unique Scientific Properties
Beyond its common role as a household mold, Cladosporium sphaerospermum possesses some unique scientific characteristics. One of its most studied properties is its ability to perform radiosynthesis, a process where it uses ionizing radiation as an energy source. This radiotrophic capability was observed in samples of the fungus found thriving inside the highly radioactive Chernobyl nuclear reactor. The dark melanin pigment in the fungus’s cell walls is thought to be responsible for absorbing the radiation and converting it into chemical energy, similar to how chlorophyll captures sunlight.
This unique trait has led scientists to explore its potential for bioremediation, using the fungus to clean up radioactively contaminated sites. Researchers are investigating whether deploying the fungus could help contain or reduce radiation levels in hazardous environments. Additionally, its ability to withstand high levels of radiation has prompted studies on its use as a radiation shield for space exploration, with experiments conducted on the International Space Station. The fungus has also shown potential in breaking down other environmental pollutants, such as hydrocarbons.