Fungi are one of the most important groups of organisms on the planet. This is easy to overlook, given their largely hidden, unseen actions and growth. They are important in an enormous variety of ways.

Recycling Fungi, together with bacteria, are responsible for most of the recycling which returns dead material to the soil in a form in which it can be reused. Without fungi, these recycling activities would be seriously reduced. We would effectively be lost under piles many metres thick, of dead plant and animal remains.

Mycorrhizae and plant growthFungi are vitally important for the good growth of most plants, including crops, through the development of mycorrhizal associations. As plants are at the base of most food chains, if their growth was limited, all animal life, including human, would be seriously reduced through starvation.

FoodFungi are also important directly as food for humans. Many mushrooms are edible and different species are cultivated for sale worldwide. While this is a very small proportion of the actual food that we eat, fungi are also widely used in the production of many foods and drinks. These include cheeses, beer and wine, bread, some cakes, and some soya bean products. 

While a great many wild fungi are edible, it can be difficult to correctly identify them. Some mushrooms are deadly if they are eaten. Fungi with names such as 'Destroying Angel' and 'Death Cap' give us some indication that it would not be a terribly good idea to eat them! In some countries, collecting wild mushrooms to eat is a popular activity. It is always wise to be totally sure that what you have collected is edible and not a poisonous look-a-like.

MedicinesPenicillin, perhaps the most famous of all antibiotic drugs, is derived from a common fungus calledPenicillium. Many other fungi also produce antibiotic substances, which are now widely used to control diseases in human and animal populations. The discovery of antibiotics revolutionized health care worldwide.

Some fungi which parasitise caterpillars have also been traditionally used as medicines. The Chinese have used a particular caterpillar fungus as a tonic for hundreds of years. Certain chemical compounds isolated from the fungus may prove to be useful treatments for certain types of cancer.

A fungus which parasitises Rye crops causes a disease known as Ergot. The fungus can occur on a variety of grasses. It produces small hard structures, known as sclerotia. These sclerotia can cause poisoning in humans and animals which have eaten infected material. However, these same sclerotia are also the source of a powerful and important drug which has uses in childbirth.

BiocontrolFungi such as the Chinese caterpillar fungus, which parasitise insects, can be extremely useful for controlling insect pests of crops. The spores of the fungi are sprayed on the crop pests. Fungi have been used to control

Colorado potato beetles, which can devastate potato crops. Spittlebugs, leaf hoppers and citrus rust mites are some of the other insect pests which have been controlled using fungi. This method is generally cheaper and less damaging to the environment than using chemical pesticides.

Crop DiseasesFungal parasites may be useful in biocontrol, but they can also have enormous negative consequences for crop production. Some fungi are parasites of plants. Most of our common crop plants are susceptible to fungal attack of one kind or another. Spore production and dispersal is enormously efficient in fungi and plants of the same species crowded together in fields are ripe for attack. Fungal diseases can on occasion result in the loss of entire crops if they are not treated with antifungal agents.

Animal DiseaseFungi can also parasitise domestic animals causing diseases, but this is not usually a major economic problem. A wide range of fungi also live on and in humans, but most coexist harmlessly. Athletes foot and Candida infections are examples of human fungal infections.

Food SpoilageIt has already been noted that fungi play a major role in recycling organic material. The fungi which make our bread and jam go mouldy are only recycling organic matter, even though in this case, we would prefer that it didn't happen! Fungal damage can be responsible for large losses of stored food, particularly food which contains any moisture. Dry grains can usually be stored successfully, but the minute they become damp, moulds are likely to render them inedible. This is obviously a problem where large quantities of food are being produced seasonally and then require storage until they are needed.

Looking at the above list, it is clear that fungi play a role in just about every part of our daily lives!

The amoeba is a tiny, one-celled organism. You need a microscope to see most amoebas - the largest are only about 1 mm across. Amoebas live in fresh water (like puddles and ponds), in salt water, in wet soil, and in

animals (including people). There are many different types of amoebas. The name amoeba comes from the Greek word amoibe, which means change. (Amoeba is sometimes spelled ameba.)

Anatomy: An amoeba consists of a single blobby cell surrounded by a porous cell membrane. The amoeba "breathes" using this membrane - oxygen gas from the water passes in to the amoeba through the cell membrane and carbon dioxide gas leaves through it. A complex, jelly-like series of folded membranes called cytoplasm fills most of the cell. A large, disk-shaped nucleus within the amoeba controls the growth and reproduction of the amoeba.

Diet: Amoebas eat algae, bacteria, plant cells, and microscopic protozoa and metazoa - some amoebas are parasites. They eat by surrounding tiny particles of food with pseudopods, forming a bubble-like food vacuole. The food vacuole digests the food. Wastes and excess water are transported outside the cell by contractile vacuoles.

Locomotion: Amoebas move by changing the shape of their body, forming pseudopods (temporary foot-like structures). The word pseudopod means "false foot."

Reproduction: Amoebas reproduce asexually by binary fission. A parent cell divides (the nucleus also divides in a process called fission) and produces two smaller copies of itself.

Classification: Eukaryota (organisms with nucleated cells), Kingdom Protista (flagellates, amoebae, algae, and parasitic protists), Phylum Protozoa (single-celled organisms), Class Sarcodina (having pseudopods).

Bacteria

“Bacteria” is a plural word. The singular for this word is “bacterium” (bacter = rod, staff). Bacteria are prokaryotes (Kingdom Monera), which means that they have no true nucleus. They do have one chromosome of double-stranded DNA in a ring. They reproduce by binary fission. Most bacteria lack or have very few internal membranes, which means that they don’t have some kinds of organelles (like mitochondria or chloroplasts). Most bacteria are benign (benign = good, friendly, kind) or beneficial, and only a few are “bad guys” or pathogens.

Kingdom Monera is a very diverse group. There are some bacteria relatives that can do photosynthesis--they don’t

have chloroplasts, but their chlorophyll and other needed chemicals are built into their cell membranes. These organsims are called Cyanobacteria (cyano =

blue, dark blue) or bluegreen algae, although they’re not really algae (real algae are in Kingdom Protista). Like us, some kinds of bacteria need and do best in O2, while others are poisoned/killed by it.

Most bacteria are one of three shapes (although there are a few other possibilities):

coccus (sing.), cocci (pl.):are spherical (coccus = a berry),

bacillus (sing.), bacilli (pl.):are rod-shaped (bacill(um) = a little stick), and

spirillum (sing.), spirilla (pl.):are spiral (spiro = spiral, coil).

While many bacteria live singly, others are found in aggregates or clusters. These aggregates are named based on the arrangement of the bacterial cells of which they are composed. Using cocci as an example:

diplococcus:like Streptococcus pneumoniae (pneumonia) are in sets of two (diplo = double, two; pneumo = lungs), PHOTO

streptococcus:are in chains (strepto = bent, twisted, pliable), and

staphylococcus:are in clusters (staphylo = a bunch of grapes).

Most bacteria secrete a covering for themselves which we call a cell wall, However, bacterial cell walls are a totally different thing than the cell walls we talk about plants having. Bacterial cell walls do NOT contain cellulose like plant cell walls do. Bacterial cell walls are made mostly of a chemical called peptidoglycan (made of polypeptides bonded to modified sugars), but the amount and location of the peptidoglycan are different in the two possible types of cell walls, depending on the species of bacterium. Some antibiotics, like penicillin, inhibit the formation of the chemical cross linkages needed to make peptidoglycan. These antibiotics don’t outright kill the bacteria, but just stop them from being able to make more cell wall so they can grow. That’s why antibiotics must typically be taken for ten days until the bacteria, unable to grow, die of “old age”. If a person stops taking the antibiotic sooner, any living bacteria could start making peptidoglycan, grow, and reproduce.

However, because one of the two possible types of bacterial cell walls has more peptidoglycan than the other, antibiotics like penicillin are more effective against bacteria with that type of cell wall and less effective against bacteria with less peptidoglycan in their cell walls. Thus it is important, before beginning antibiotic treatment, to determine with which of the two types of bacteria one is dealing. Dr. Hans Christian Gram, a Danish physician, invented a staining process to tell these two types of bacteria apart, and in his honor, this process is called Gram stain. In this process, the amount of peptidoglycan in

the cell walls of the bacteria under study will determine how those bacteria absorb the dyes with which they are stained, thus bacterial cells can be Gram+ or Gram -. Gram+ bacteria have simpler cell walls with lots of peptidoglycan, and stain a dark purple color. Gram- bacteria have more complex cell walls with less peptidoglycan, thus absorb less of the purple dye used and stain a pinkish color instead. Also, Gram- bacteria often incorporate toxic chemicals into their cell walls, thus tend to cause worse reactions in our bodies. Because Gram- bacteria have less peptidoglycan, antibiotics like penicillin are less effective against them. As we have discussed before, taking antibiotics that don’t work can be bad for you, thus a good doctor should always have a culture done before prescribing antibiotics to make sure the person is getting something that will help.

One “famous” person who worked with bacteria was Dr. Robert Koch, a German physician. He is famous for several discoveries related to bacteria:

1.  He noted bacteria growing on a spoiled potato and realized that each colony he saw grew from one bacterium that had landed on the potato. He realized he could remove a bit of one of the colonies and transfer it to a sterile medium to start a pure culture of that species of bacterium. This is called single

colony isolation. 

2. Up until that time, researchers working with bacteria were trying to use gelatin to solidify nutrient media upon which to grow bacterial cultures, but there were a number of problems with this. Because gelatin is a protein, many bacteria are able to digest it and use it for food, resulting in liquification of the medium. Also, most of the bacteria that cause diseases grow best at body temperature (37°C), but as anyone who has tried taking Jello to a picnic knows, gelatin liquifies at that temperature. Based on a suggestion from a housewife friend, Koch developed the use of agar (a polysaccharide isolated from seaweed) to solidify nutrient media upon which to raise/grow bacteria. Because agar is a complex polysaccharide, most bacteria cannot digest it, and it remains solid at body temperature, enabling researchers to incubate bacteria, encouraging their growth.

3. He was the first person to actually connect certain disease(s) to specific bacteria. He established four criteria, called Koch’s Postulates, which if met, prove a specific pathogen causes a specific disease (in animals):

a. the same pathogen must be found in all diseased individuals (those showing the same symptoms),

b. the pathogen must be isolated from the diseased subjects and grown in pure culture on some nutrient medium,

c. the same disease must be induced in experimental animals by transferring bacteria from the pure culture into their

bodies, and

d. after the disease develops, the same pathogen must be isolated from the experimental animals.

If all four of these steps can be demonstrated, then it can be said that the pathogen in question causes that disease. Koch specifically proved that anthrax and tuberculosis were caused by specific species of bacteria. Other people have demonstrated this relationship for a number of other bacterial diseases. Interestingly, this has never been done for the bacterium that causes syphilis. While we “know” what it is and how to treat it, no one has been able to grow it in