Biological Sciences
Molds
Molds are a type of fungus that typically grows in the form of multicellular filaments called hyphae. They reproduce by forming spores, which can be dispersed through the air or water. Molds play important roles in nature, such as breaking down organic matter, but they can also cause health issues and damage to buildings when they grow indoors.
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6 Key excerpts on "Molds"
eBook - PDF- Thad Godish(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
167 chapter six Biological contaminants — mold Biological contaminants were described in Chapter 5 in the context of illness syndromes and disease risks associated with exposure to airborne organisms and products of biological origin. Discussion of airborne bacteria and viruses was in the context of their role in causing infectious disease and potentially contributing to other problems; mites, insects and animal allergens, in the context of causing chronic allergic rhinitis and asthma. Because mold is such a significant indoor environment concern, this chapter is devoted to mold- related health concerns and risk factors for mold infestation. I. Biology of mold The terms mold and mildew are commonly used to describe the visible manifestations of the growth of a large number of organisms that are scien- tifically classified as fungi. Terms such as yeast and mushrooms are used to describe, respectively, single-celled fungi (widely used for baking and brew- ing) and the large reproductive structures of a major class of fungi that are used for food or are known for their high toxicity. Fungi form true nuclei, which distinguishes them from lower organisms such as bacteria. They differ from plants in that they do not produce chlo- rophyll and thus cannot manufacture their own food; from animals in that (except for reproductive cells in some species) they are not motile. Structurally, fungi exist as masses of threadlike filaments or hyphae. The collective mass of hyphal filaments is described as mycelium, the vegetative part of the organism that infests a substrate and extracts food for the organ- ism’s growth. Though hyphal filaments are microscopic, the mycelium is typically visible to the naked eye. Masses of mycelia can be distinguished as fungal colonies (Figure 6.1). In many species, the hyphae are colorless; in other species they contain pigments.
- David M. Carlberg(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
Unlike spore-forming bacteria, where only one spore is formed per cell, a single mold hypha may produce thousands of spores, each of The Scope of Microbiology 19 which can be launched into the air with the slightest air movement. If the spore happens to land on a site where there are nutrients and moisture, it will germinate and eventually develop into a new mycelium. While mold spores are somewhat more resistant to harsh conditions than the cells that make up the hyphae, mold spores generally are nowhere as resistant to adverse environmental conditions as are bacterial endospores. Thus, chemical and physical means that destroy bacterial spores easily eliminate mold spores. People are most familiar with Molds because of their association with food spoilage and the deterioration of materials and equipment through mildew and dry rot. In addition, a few species of Molds are responsible for diseases in animals and plants. The destructive effects Molds have on landscape plants, food crops, and consumer products cause billion dollar losses each year for farmers, manufacturers, and consumers. On the positive side, many of our most effective antibiotics, such as penicillin, griseofulvin, and gentamicin, are produced by Molds. Also, many species of Molds are necessary in the manufacture of important products such as corticosteroids and citric acid and dozens of foods like soy sauce, miso, and blue cheese. Molds are the second most common microbial contaminant in the cleanroom and, under certain circumstances, they can become a serious threat. Their nutritional requirements are generally simpler than those of bacteria, and many species can grow in the absence of significant amounts Figure 1.9 Tangled mycelium of the mold Microsporum. Conical structures are macroconidia or spore cases. (Photo: CDC Public Health Image Library ID #4325.) 20 Cleanroom Microbiology for the Non-Microbiologist of moisture.
eBook - PDF- Wilhelm Tham, Marie Louise Danielsson-Tham, Wilhelm Tham, Marie Louise Danielsson-Tham(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
CHAPTER 11 Moulds as a Threat to Food Safety Dereje T. Asefa 1, * and Ida Skaar 2 Introduction Moulds Moulds are part of the natural environment and grow practically everywhere. They are microscopic fungi that are found indoors and/or outdoors throughout the year (Carlile et al. 2001, Deacon 1997, Samson et al. 2004). Moulds grow best in warm, damp, humid conditions and spread with the help of the spores they are producing. On moist, nutrient-rich substrates the spores can germinate into tiny filaments called hyphae that form mycelia upon further extension (Deacon 2006, Pitt and Hocking 2009, Webster and Weber 2007). Mould spores can survive harsh environments, such as, dry conditions that are not suitable for microbial growth (Pitt and Hocking 2009). Moulds are heterotrophic that break down organic materials with the help of extra cellular enzymes and absorb carbon for energy (Pitt and Hocking 2009, Webster and Weber 2007). 1 Reeco-san International, Gamle Åsvei 25, 1400, Ski. Email: [email protected] 2 Section of Mycology, The Norwegian Veterinary Institute, Ullevålsveien 68, Pb 750 Sentrum, Oslo, Norway. Email: [email protected] * Corresponding author 142 Food Associated Pathogens Species concept Moulds are multi-cellular eukaryotic organisms belonging to the fungal kingdom (Pitt and Hocking 2009). Species is the unit of measure that biologists use to categorize and differentiate diversity. Moulds were classically identified at a species level based on their differences in macro (colony characters) and micro morphological characters (reproductive structures) in a specific environmental niche (Deacon 1997, Pitt and Hocking 2009, Webster and Weber 2007). The method is good to identify the most common fungi but cannot be employed on the majority of fungi as they are uncultivable and lack the important reproductive structures useful for identification (Pitt and Hocking 2009, Samson et al. 2004).
eBook - PDF- F Cunningham(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Included in this group are also the true yeasts Saccaromyces, Candida, and other yeasts. Diagrams of commonly occurring yeast and mold are given in Fig. 2. Basidiomycetes. The hyphae are septated; asexual spores are rarely ob-served; and sexual spores (basidiospores) occur at the tip of basidium. Common examples of this group are mushroom, toadstools, smuts, etc. 2. T y p e s of Microorganisms 17 Mucor Rhizopus Aspergillus Pénicillium Fusarium Alternaria Cephalosporium Botrytis Trichothecium Cladosporium S a c c h a r o m y c e s Candida F i g . 2. Typical morphologies of some common yeasts and Molds. Deuteromycetes or Fungi Imperfecti. This is a catch-all grouping of all those fungi that show asexual, but not sexual, cycles. Once both sexual and asexual cycles are characterized, the culture will be assigned accord-ingly to one of the aforementioned subdivisions, most likely the Ascomycetes. The role of yeasts and Molds in poultry products is mainly in food spoilage. When poultry products are processed and kept at low tem-peratures for a long time there may be chances for spoilage from yeasts and Molds. The only real food poisoning concern is the possible produc-tion of a carcinogenic toxin called aflatoxins by species of Aspergillus (A. flavus and A. parasiticus). Other yeasts and Molds are chance contami-nants. V. M I C R O B I A L G R O W T H A N D D E A T H Growth of microorganisms can be viewed as growth in size of an individual organism or growth in numbers of a population. Since micro- 18 Daniel Y. C . Fung organisms are minute in size, growth is usually ascertained by monitor-ing numbers. Thus, in terms of studying growth and death of micro-organisms, it is common to monitor population dynamics. This assump-tion is valid only for the truly unicellular organisms such as bacteria and yeasts.
eBook - PDFNonhuman DNA Typing
Theory and Casework Applications
- Heather Miller Coyle(Author)
- 2007(Publication Date)
- CRC Press(Publisher)
153 9.15 Conclusion ........................................................................................... 157 Acknowledgments ......................................................................................... 158 References ...................................................................................................... 158 9.1 Introduction Fungi are one of the largest and most heterogeneous eukaryotic families, with various species, forms, and a wide range of habitats such as air, land, and sea. The word fungus is thought to be derived from the Greek word sphongis , meaning sponge; however, others have suggested that the word could be derived from the Latin Fingus ago , meaning I make a corpse. The word toadstool , referring to a poisonous mushroom, comes from the German word todess-tuhl , which means death’s stool . 1 The first fossil of a land plant and fungi appeared 480 to 460 million years ago. 2 It is estimated that there are approximately 1.5 million species of fungi; roughly 80,000 species of them have been described. 3 These creatures 136 Nonhuman DNA Typing: Theory and Casework Applications have a vital role in ecology and human life such as in fermentation, agricul-ture, food spoilage, 4 natural decomposition, and in various scientific and industrial applications. Sir Alexander Fleming, the discoverer of penicillin, said one day to a group of artists, “If any of you chaps has got a pair of moldy old shoes, I’d very much like to have’em.” Fleming was curious about Molds as part of his research of antibiotics. 5 In forensics, we may ask many questions about the growth of Molds on a pair of shoes: 1. Which mold species are growing on those shoes? 2. How long did it take them to grow? 3. How large is the growth? 4. On which side is there more growth? 5. What are the effects of the mold growth on the leather? 6. Were the Molds disturbed by some action during the crime? 7. What were the moisture and temperature conditions? 8.
- Martha J. Boss, Dennis W. Day(Authors)
- 2020(Publication Date)
- CRC Press(Publisher)
After the spring thaw, Molds thrive on the vegetation that has been killed by the 122 AIR SAMPLING AND INDUSTRIAL HYGIENE ENGINEERING winter cold. In the warmest areas of the world, however, Molds thrive year-round and can cause perennial allergic problems. Molds growing indoors can cause perennial allergic rhinitis even in the coldest climates. If indoor areas show signs of amplification identified by visual assessment, air sam-pling, and contact/liquid sampling, amplification must be suspected. Amplification is the process whereby biological organisms continue to increase over time. If this increase is not controlled, sufficient mold spores and vegetative structures may be present to create indoor air problems . Hot spots of mold growth in the home include damp basements and closets, bathrooms (especially shower stalls), places where fresh food is stored, refrigerator drip trays, house plants, air conditioners, humidifiers, garbage pails, mattresses, upholstered furniture, and old foam rubber pillows. 6.1.1 What Is the Difference between Molds, Fungi, and Yeasts? Molds and yeasts are two groups of plants in the fungus family. Yeasts are single cells that divide to form clusters. Molds consist of many cells that grow as branching threads called hyphae. The seeds or reproductive particles of fungi are called spores. They differ in size, shape, and color among species. Each spore that germinates can give rise to new mold growth, which in turn can produce millions of spores. 6.1.2 How Would I Become Exposed to Fungi That Would Create a Health Effect? The route of exposure may be inhalation or ingestion accompanied by inhalation. When inhaled, microscopic fungal spores or fragments of fungi may cause health prob-lems. Because they are so small, mold spores may evade the protective mechanisms of the nose and upper respiratory tract to reach the lungs and bring on asthma symptoms. The buildup of mucus, wheezing, and difficulty in breathing are the result.
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