WHAT IS A micro-organism ?
Micro (Invisible with naked eye) + organism (Being alive)
THE MICROBIAL WORLD
Bacteria: unicellular organism measuring from 0.5 to 7 microns; Main origin= mammals and environment; proliferate through cell division
Yeast: unicellular organism measuring 6 to 25 microns; Main origin =environment; proliferates by budding
Mold: Organsm forming multi-cellular mycelium; Main origin = soil; proliferates by producing billions of conidia (2-50 microns) = spores.
The microscopic algae: Organisms capable of photosynthesis and growth in liquid media in the presence of light. They have extremely varied shapes and sizes. They are the basis of many food chains.
A mold is an eukaryotic organism, multi-cellular belonging to the kingdom of Fungi, can colonize numerous environments and is highly contaminant. They have a large and varied enzyme potential (cellulases, proteases …). In sum, molds can grow with wery limited substrate and on a huge variety of media: plasterboard, wood, wallpaper, food, dust, plants … They also have the ability of release spores and contaminate the air.
Molds development factors are :
Water activity (aw): the most important because it is the water available for growth of microorganisms. Several factors can affect the aw of a place or product: the temperature (condensation), weather, leaks and water damage and the water content of a support (material, plant, food … )
- Temperature: in general, growth from 4 ° to 30 ° C. Optimum between 18-28 ° C.
Oxygen: molds are able to grow in a very wide range of oxygen (from ambient air to the product having only trace of oxygen)
- pH: yeasts / molds Optimum pH 5-6 but some can grow in pH ranges from 2 to 12.
The mold growth can cause the deterioration of the structure of a building, health risks to its occupants, problems for the products quality…
A food product that has changed color due to microbial growth
Mould growth on materials will lead to changes in their physical properties but will also contribute to the degradation of air quality.
During germination, spores form germinative tubes which will divide to create mycelium.
Molds are responsible for many plant diseases. Here, the leaves of potato plants infected by fungi of the genus Alternaria.
Scopulariopsis sp. is a mold which is considered a contaminant but which in certain circumstances is desired as quality proof (for example on specific cheese).
A typical conidiophore of an Aspergillus.
The mycelium is composed of thousands of filaments visible under microscope.
Another example of Penicillium, typical mold of our latitudes.
A microscopic picture of Penicillium sp. Conidiophores are structures where born spores.