Saprophytic molds are decomposers
Many of the molds that can be found growing indoors, share a common ‘personality’ trait. They are all ‘Saprophytes’.
Saprophytes are classified as a type of organism (in this case fungi), that feed on decaying organic materials.
Sapros, in Greek, means rotten. Trophe, in Greek, means nourishment. Thusly, Saprophytes derive their nutrition from decaying matter.
In doing so, Saprophytic fungi ‘unlock’ many of the nutrients, amino acids, vitamins and minerals in the decaying matter so the nutrients can return to the ecosystem and be absorbed by plants, trees and eventually animals.
Saprophytes are an integral part of the terrestrial ecology of earth!
Saprophytes are at home in soil, on grains and seeds, growing on logs, mulch, manure and fallen leaves. Saprophytes are the unsung heroes of the nutrient-recycling community.
But, is there a catch?
Saprophytes are our allies outdoors, but indoors (if there is a moisture source) they can be a nuisance!
Why cant mold stay outdoors, and out of my home?
Sometimes I wish I could say to the fungi, ‘Not this home buddy!’
Molds and spores, like humans and many other organisms, are opportunistic. If they sense food and water, they sit themselves down and feast. Even if it’s not their home, but yours.
Much like humans, buffalos, and migratory birds travel long distances seeking resources to grow and reproduce, so do saprophytic fungi.
Saprophytic fungi do not have legs, so how do they travel?
Introducing, the Mold spore!
Spores float, and go with the wind. They are as roving as one can be.
Spores are microscopic, and are lightweight, weighing nano-grams. They are caught by the slightest wind currents, and are carried long distances until they settle down on a suitable nutritional source.
How does a Mold Spore become Mold?
The spore is a reproductive cell capable of germination, and growth. They are akin to a ‘seed’ or ‘pollen’ for plants, but unlike seeds, do not rely on sexual reproduction.
Spores asexually reproduce, meaning, they do not need to be ‘germinated’ by pollen or require a male / female spore counter part.
Spores require two things, a food source and a moisture source.
Some mold spore types prefer growing on cellulose based materials ie. plants, fibers, leaves and some prefer lignin based materials ie. wood and wood pulp.
If a singular spore ‘stumbles’ upon a suitable growth medium of choice, and has access to sufficient moisture, it will begin to germinate.
Spores can germinate in your home with sufficient moisture
Your home is filled with suitable growth mediums! Plywood, drywall, wall paper, baseboards, insulation; you name it, there is a mold that can potentially grow on it.
But, remember, mold needs moisture. Relative humidity over 60%, or building materials with greater than 15% moisture content set the mold spore up for germination conditions.
Flood, leaks and improper AC function can all provide sources of moisture or elevated relative humidity.
This is why keeping relative humidity levels under 60%, preventing dust and organic matter buildup in your duct system (regular duct cleanings and HVAC service) as well as changing your filter are the key to prevent spore germination in your home. Read more about this here.
We have addressed what saprophytic molds are (organic decomposers, leaves soil etc.), what mold spores are (reproductive cell capable of germination) and what mold spore need for germination.
How do mold spores get inside a home?
Spores are all around us, they can ‘float’ and be ‘carried’ into your home!
Every time you open a window or door, spores can (and probably will) enter through the air. Spores can get caught on the fur of animals, shoes and clothing. They are microscopic, you wont see them, but they are there.
Look at the trees, shrubs and bushed around your home. Do you have mulch? Is there soil? If you answered yes to any of these, there are mold spores floating around the air outside.
This is normal and nothing to be concerned about. All homes and buildings in the united states (and around the world) will have some levels of spore count.
There is no national standard for indoor spore count, but as a licensed mold assessor, this is part of our professional duty. We have the discretion and knowledge to analyze the results and determine if indoor spore counts are consistent with a normal ‘non-contaminated’ home.
General life cycle of mold
Life cycle of mold:
- Spore: Spores vary in size, shape and relative weight. They’re phenotypic (expressed genetic traits) all contribute to their ability to grow and reproduce. Spores float around until they settle on an appropriate food and water source.
- Germination: Once the spore settles in an environment with suitable moisture and nutrients (outdoors: decaying vegetation, soil, compost, indoors: building materials like drywall), it germinates. This requires suitable temperatures and an organic substrate from which to obtain nutrients. The round spores, germinate, and begin to form thread like filaments.
- Hyphal Growth: After germination, the spore grows into hyphae, which are multicellular filaments that grow on and then into the growth medium. For example, the hyphae will begin to grow on the back of water damaged drywall and then will grow into the drywall. This network of hyphae, known as the mycelium, absorbs nutrients from the material around it.
- Colony Formation: As the network of hyphae expands, it forms a visible colony or group. In Aspergillus mold, colonies can appear as ‘velvety’ or ’dusty’ and in colors of green, yellow, or black due to spore production on the surface.
- Asexual Reproduction: Saprophytes most commonly reproduce asexually. They form a structure called a conidiophore, which is a specialized hyphal stalk. Atop these stalks, conidia (asexual spores) are produced in chains. Once mature, these spores are released into the air to be dispersed and spread by air currents.
- Spore Dispersal: The newly formed asexual spores (conidia) travel through the air to new locations where they can start the life cycle anew. Spores can remain dormant for long periods of time until they land in conditions suitable for growth, at which point the cycle begins again.
This, ladies and gentleman, is how spores begin outside and can end up inside your home.
Key Takeaways:
- Molds are opportunistic
- Molds are decomposers
- Mold spores are ubiquitous around the world
- Mold spores get carried through the air
- Molds need moisture and a food source
- Once Mold spores land on moisture and food, they germinate
- Once they germinate they grow into, hyphae, mycellium and mold colonies
- Mold Colonies form new spores, release them
- The cycle repeats
Key Takeaways, Mold growth indoors:
- Molds leverage water damaged building materials and elevated relative humidity
- Keep your relative humidity under 60%
- Change your filter regularly
- Keep your AC system clean
- Eat good food, drink clean water and be a loving human being!!
Sources:
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/saprophyte
https://www.britannica.com/science/saprotroph
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2936274/
https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home
About the Author
Brett Brunsvold, President of Full Spectrum Environmental LLC, is a certified expert in the field of environmental health and safety with a diverse set of qualifications. Holding certifications as a Certified Indoor Environmentalist (CIE #234891) and Remediation Supervisor (CRMS #2401011), Brett is also a licensed Mold Assessor (MRSA1538) and Mold Remediator (MRSR4976). Brett’s proficiency extends to water quality management as a DEP Stormwater Inspector (#53216).
Beyond his professional endeavors, Brett is an amateur mycologist, bringing a scientific curiosity and enthusiasm to the study of fungi, which complements his professional work in mold assessment. His passion for the outdoors is evident in his regular hiking excursions and his dedication as an avid nature lover. Brett is also a keen swimmer, often found exploring the waters around West Palm Beach, Florida, where he resides. This blend of professional expertise and personal interests highlights Brett’s comprehensive approach to environmental health, combining thorough knowledge with a deep appreciation for the natural world.