Fungi and the Development of Microbiological Chemistrv green Penicillium species growing on the surface of some cheese.However. there are some con mon features.The basic structural units of most fungi are the filaments known as the hyphae.Collectively,hyphae can aggregate to form a felt kno as the In so of the higher ungi the hyphae car aggregat to form long strands and even differentiate ate a structur almost like a boot-lace,which is known as a rhizomorph.Another name for the honey-fungus,Armillaria mellea,which does considerable damage to trees,is the 'boot-lace fungus',which aptly describes the rhizomorphs by which it spreads underground. The higher fungi,the mushrooms and toadstools,develop complex and readily observable structures known as fruiting bodies.These sprout from their mycelium,particularly in the autumn,and produce spores.At the other ex nicellular ch as the yea s,produce small globular or ellipsoid The hyphae may be long single multi-nucleate aseptate (undivided)cells through which the cellular cytoplasmic fluids may flow.Other hyphae are septate and have distinct divisions.In these much of the chemical activity takes place at the growing tip.The lower micro-fungi only become septate as the culture ages whilst the higher macro-fungi become septate at an early stage and as rhizom norphs are formed,their function may differentiate The form a fun ous takes nd on the cultu will have a yea like fo conditions.Some fung set o of com tous forn under others.Unde often expl cultures,an organism can develop a 'resting stage.In the wild this can allow spores to over-winter in the soil.In the laboratory.fungal cultures are often stored at low temperatures on agar under oil or in sealed vials on sand. When a fungus is grown in suspension in a nutrient medium contained within a conical flask,the mycelium will sometimes clump together whilst at other times a well-dispersed mycelial suspension or e mycelial mat is for ned.The aeration nd he n the etabolic apabilities of these form can differ be qu poor within fungi to produce fruiting bodies in laboratory culture and again this can affect their metabolite production.Some rapidly growing fungi such as Rhizopus species produce fine long hyphae that spread rapidly across the agar in a Petri dish.They may produce a covering of aerial mycelium with the appearance of household dust.Indeed,quite a lot of household dust is fungal celium. Fungius ally reproduce by spores although they can also develop vegetatively from mycelial Ifragments.The spores may be pigmented and some may have gelatinous polysaccharide coating to facilitate their dissemination by a carrier and their attachment to a host.They are often borne on a specific thallus or germ tube.Hyphae that carry these are known as conidiophores.A culture such as that of Botrytis cinerea may appear light grey as the mycelium spreads across a Petri dish and then it develops a ring of green-black sclerotial mycelium bearing spores. green Penicillium species growing on the surface of some cheese. However, there are some common features. The basic structural units of most fungi are the filaments known as the hyphae. Collectively, hyphae can aggregate to form a felt known as the mycelium. In some of the higher fungi, the hyphae can aggregate to form long strands and even differentiate to create a structure almost like a boot-lace, which is known as a rhizomorph. Another name for the honey-fungus, Armillaria mellea, which does considerable damage to trees, is the ‘boot-lace fungus’, which aptly describes the rhizomorphs by which it spreads underground. The higher fungi, the mushrooms and toadstools, develop complex and readily observable structures known as fruiting bodies. These sprout from their mycelium, particularly in the autumn, and produce spores. At the other ex￾treme some unicellular micro-fungi, such as the yeasts, produce small globular or ellipsoid cells that are only visible under the microscope. The hyphae may be long single multi-nucleate aseptate (undivided) cells through which the cellular cytoplasmic fluids may flow. Other hyphae are septate and have distinct divisions. In these much of the chemical activity takes place at the growing tip. The lower micro-fungi only become septate as the culture ages whilst the higher macro-fungi become septate at an early stage and, as rhizomorphs are formed, their function may differentiate. The form a fungus takes can depend on the culture conditions. Some fungi will have a yeast-like form under one set of conditions and a filamentous form under others. Under inhospitable conditions, often exploited in the storage of cultures, an organism can develop a ‘resting’ stage. In the wild this can allow spores to over-winter in the soil. In the laboratory, fungal cultures are often stored at low temperatures on agar under oil or in sealed vials on sand. When a fungus is grown in suspension in a nutrient medium contained within a conical flask, the mycelium will sometimes clump together whilst at other times a well-dispersed mycelial suspension or even a mycelial mat is formed. The aeration and hence the metabolic capabilities of these forms can differ. The aeration can be quite poor within tightly formed clumps and this can affect the metabolism of the fungus. It is often difficult to get higher fungi to produce fruiting bodies in laboratory culture and again this can affect their metabolite production. Some rapidly growing fungi such as Rhizopus species produce fine long hyphae that spread rapidly across the agar in a Petri dish. They may produce a covering of aerial mycelium with the appearance of household dust. Indeed, quite a lot of household dust is fungal mycelium. Fungi usually reproduce by spores although they can also develop vegetatively from mycelial fragments. The spores may be pigmented and some may have a gelatinous polysaccharide coating to facilitate their dissemination by a carrier and their attachment to a host. They are often borne on a specific thallus or germ tube. Hyphae that carry these are known as conidiophores. A culture such as that of Botrytis cinerea may appear light grey as the mycelium spreads across a Petri dish and then it develops a ring of green-black sclerotial mycelium bearing spores. Fungi and the Development of Microbiological Chemistry 3