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You are here: Home / Archives for moulds

My Interest In The Study Of Fungi.

Jackson Kung'u

I have always been fascinated by fungi. Fungi are a group of organisms to which moulds (mildews), yeasts, and mushrooms belong. Fungi used to be classified under the plant kingdom. However, they differ from plants in that they cannot make their own food and their cell wall is mainly made of chitin and glucan and not cellulose. Since they cannot make their own food, fungi have to survive as either saprophytes, parasites (pathogens) or by forming symbiotic relationships with their hosts. Saprophytic moulds are the ones commonly found in indoor environment growing on wall surfaces and other organic substrates. It is estimated that there are close to 1.5 million species of fungi but only about 100,000 species have been described.

Entomosporium spores
Entomosporium spores

My interest in fungi started when I completed my B.Sc. (Agriculture) and got employed as a plant pathologist. As a trainee plant pathologist, I spent countless hours in a plant clinic where farmers brought their diseased plants for diagnoses. My first fungus to identify without help was Entomosporium. One feature that makes me remember this fungus is the shape of the spores. The spores have appendages that make them resemble insects or two-legged mice with legs stretched sideways. I also went out into the field collecting diseased plants and taking them back to the laboratory for disease diagnoses and preservation as reference material. Working with diseased plants is not always easy because they won’t tell you where it is hurting (if at all they feel pain). You have to depend on symptoms and laboratory culturing and identification of the causative agent. If a plant is just wilting, for example, it is had to tell the cause of wilting which could be due to fungi, nematodes, bacteria, physical/chemical or physiological factors that interfere with water movement in the plant.

In my early days as a trainee, one challenge I had was to isolate the disease causing agent and getting pure cultures of the mould. It was not always easy because of the myriad saprophytic moulds and bacteria present on the surfaces of the plant. However, I learned quickly some clever ways plant pathologists and mycologists have developed to overcome the problem of contamination.

I was fortunate to be taught and interact with some of the world authorities in Mycology at CABI Bioscience (formerly the International Mycological Institute) and the University of Kent in the United Kingdom. These great people made me to like the subject.

My interest in fungi is now focused on indoor moulds. Indoor moulds are recognized health hazards and it is estimated that 20% of human population is sensitive to mould exposure. It is also believed that long-term exposure to mould could lead to sensitization.

Filed Under: Fungi Tagged With: Fungi, mildews, moulds, yeasts

Are There Moulds That Can Be Used As Indicators Of Marijuana Grow Operations In A Building?

Jackson Kung'u

With increasing grow ops in residential houses many home buyers, home inspectors and indoor air quality consultants wonder if there were some types of mould species that can be used as ‘fingerprints’ or indicators for homes formerly used for marijuana grow ops. Currently we are not aware of species of moulds that can strictly be associated with marijuana grow ops. However, the dominant moulds in a building environment are generally indicative of the moisture levels prevailing over a long period of time.

The environments tends to select and maintain certain micro-organisms as the “home microflora”. This “home microflora” is usually determined by the types of nutrients available, water activity, pH and temperature. In building environments, moisture is the growth limiting factor for moulds. Moulds differ in their water requirements. A small group of moulds requires high levels of available water (water activities of more than 0.9). This group, referred to as hydrophilic or tertiary colonizers can be used as indicators for water/moisture damaged buildings. Such moulds include species of Chaetomium, Fusarium, Memnoniella, Stachybotrys, Trichoderma, Ulocladium and a few others. The largest group of moulds requires continuous damp conditions (or water activities between 0.80 and 0.90). This group is referred to as secondary colonizers. Examples of secondary colonizers include common indoor contaminants such as Cladosporium spp and some species of Aspergillus and Penicillium. Another small group of noulds, the xerophilic or xerotolerant, is able to grow at water activities below 0.80. This group, also referred to as primary colonizers, include Aspergillus restrictus, Aspergillus versicolor, Eurotium spp., Penicillium aurantiogriseum, P. brevicompactum, P. chrysogenum and Wallemia sebi. Xerophilic moulds are indicators of relatively dry environments.

Moulds commonly associated with marijuana in storage include species of Aspergillus, Penicillium, Fusarium, Mucor, Rhizopus, Alternaria, and Curvularia. These moulds cannot be used as indicator moulds for marijuana grow ops since they are also found on many other substrates.

Secondary colonizers are likely to be the most common in houses used for grow ops but they are not unique to the grow ops. In conclusion no moulds are currently known to be strictly associated with marijuana grow operations.

Filed Under: Fungi Tagged With: Grow ops, marijuana, molds, moulds

What is the Difference between Moulds and Bacteria?

Jackson Kung'u

Recently one of our website visitors wanted to know the difference between moulds and bacteria.

Moulds and bacteria are very different organisms. They are genetically unrelated. Moulds are larger, complex and grow as long, multi‑celled filaments (hyphae). Those filaments can aggregate to form larger masses (referred to as mycelia) visible to unaided eye. That is why we can see mould growth, for example, on a wall surface. Bacteria are smaller, single-celled and less complex. Requirements for growth and the means of reproduction for moulds and bacteria differ in many aspects.

Do you have a mould problem? Call (905)290-9101.

Filed Under: Bacteria, Fungi Tagged With: Bacteria, molds, mould, moulds

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May 2025
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Salmonella food poisoning and symptoms

Salmonella food poisoning has been a growing concern in recent news. It has frequently lead to recalls of beef, salads and organic products and, even peanut butter products. Salmonella food poisoning occurs when one eats raw or undercooked foods such meat, poultry, eggs or egg products. Properly cooked food can get contaminated with Salmonella if […]

Legionella pneumophila – Guidelines for Laboratory Interpretation

Legionella pneumophila is a Gram negative, aerobic bacteria that is characterized as an opportunistic pathogen. It is the cause of Legionnaires’ Disease, a severe form of pneumonia and, it is the cause of Pontiac fever, a non-pneumonic form of L. pneumophila infection. Legionella spp.’s mode of transmission is through aerosols or aspiration of contaminated water. The Public Health […]

The Indoor Mold Is An Early Warning Device

The mold (or mould, in the Queen’s English) has been the victim of a bad press. Mention the word and it conjures up an image of something rotting or in the process of decomposition. And yet, were it not for the mold that inspired the discovery of penicillin millions of lives would have been lost. […]

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