Practical procedure

STUDY OF FUNGI - PENICILLIUM AND ASPERGILLUS

AIM

To isolate and identify fungi - Penicillium and Aspergillus.

PRINCIPLE

       The morphology of fungi is usually viewed by performing wet mount. The primary purpose of preparing a wet mount is to demonstrate conidia or other reproductive structure, which might give information towards the identification. It is based on the characteristic shape and arrangement of the conidia and the size of the hyphae. Lactophenol cotton blue is a stain commonly used for making a semi-permanent microscopic preparation of fungi. It stains the fungal cytoplasm and provides the light blue background against the walls of hyphae can readily to seen. It contains four constituents namely phenol which serves as a fungicide, lactic acid which acts as a clearing agent, cotton blue which stains the outer wall of the fungus and glycerine which gives a semi-permanent preparation. A permanent preparation may be made by incorporating polyvinyl alcohol in place of glycerine into the mounting medium.

MATERIALS REQUIRED

       Microslide, Coverslip, Petri plate, Pipette, Conical flask, Lactophenol cotton blue stain, inoculation Loop, Microscope.

PROCEDURE

l  Serial dilution technique (10^-1 - 10 ^-7) is done to isolate the fungi and plated on potato dextrose agar.

l  A drop of lactophenol cotton blue stain was placed on a clean glass slide.

l  A small portion of the fungal colony was pickled using a sterile needle and placed on to the drop of lactophenol cotton blue on the slide.

l  The coverslip was placed over the drop and carefully pressed down hard to spread the fungus and examined under the microscope for reproduction structure under 10X and 40X objective.

OBSERVATION 

Aspergillus

       This mold is also known as Eurotium. It is a common saprophytic fungus. The vegetative body consists of a well-branched delicate, white, flocculant, hyaline mycelium. Hyphae rancify over the substratum superficially and some penetrate deeper. A sexual reproduction occurs by the production of conidia from a range of the number of conidiophores. Chains of conidia are born on bottle shaped sterigmata Aspergillus species produce aflatoxin. It involves in the spoilage of foods such as the foods with high concentration of sugar and salt and also in low moisture content foods. This fungus causes infection in the middle ear called as mycosis and in lungs called as pulmonary Aspergillosis.

Penicillium

       It is also called blue-green mold. Mycelium is extensively septate from which arises conidiophores that branch into broom or bottle shaped sterigmata. Penicillium species produces important antibiotics. They are used in the ripening of cheese production of organic acids. They produce soft rot of fruits, some troubles in canned acid foods. It causes opportunistic infection in man.