Algae

Algae are a very diverse group of photosynthetic organisms that range from microscopic size to giant kelp that may reach lengths of 20 m (66 ft). Some commercial biochemicals come from algal seaweeds, and algae supply oxygen and consume nutrients in some processes used for biological waste treatment.

Although their rapid growth rates relative to other green plants offer great potential for producing biomass for energy or a chemical feedstock, there is little industrial use of algae. One proposed process uses Dunaliella, a species that grows in high salinity and accumulates glycerol internally to counter the high external osmotic pressure. Outdoor ponds are most suitable for growing algae because vast surfaces and high illumination are needed.

Fungi As a group, fungi are characterized by simple vegetative bodies from which reproductive structures are elaborated. All fungal cells possess distinct nuclei and produce spores in specialized fruiting bodies at some stage in their life cycles. The fungi contain no chlorophyll and therefore require sources of complex organic molecules for growth: Many species grow on dead organic material; others live as parasites.

Yeasts are one kind of fungi. They are unicellular organisms surrounded by a cell wall and possessing a distinct nucleus. With very few exceptions, yeasts reproduce by a process known as budding, where a small new cell is pinched off the parent cell. Under certain conditions, an individual yeast cell may become a fruiting body, producing spores.

Isolated Plant and Animal Cells Biotechnology includes recovery of biochemicals from intact animals and plants, but the care and feeding of them is beyond the scope of this section. Processes with their isolated cells have much in common with processes based on microorganisms. The cells tend to be much more fragile than microbial cells, and allowable ranges of pH and temperature are quite narrow. These cells occur in aggregates and usually require enzymes to free them. There is a strong tendency for the cells to attach to something, and cell cultures often exploit attachment to surfaces.

Plant and animal cells have numerous chromosomes. Growth rates are relatively slow. A typical nutrient medium will contain a large number of vitamins and growth factors in addition to complex nitrogen sources, because other specialized cells in the original structures supply these needs. A plant or animal cell is not like a microbial cell in its ability to function independently.

Bacteria as Single Cell

The bacteria are tiny single-cell organisms ranging from 0.5–20 mm in size, although some may be smaller, and a few exceed 100 mm in length. The cell wall imparts a characteristic round or ovoid, rod, or spiral shape to the cell. Some bacteria can vary in shape, depending on culture conditions; this is termed pleomorphism. Certain species are further characterized by the arrangement of cells in clusters, chains, or discrete packets.

Some cells produce various pigments that impart a characteristic color to bacterial colonies. The cytoplasm of bacteria may also contain numerous granules of storage materials such as carbohydrates and lipids. Bacteria can contain plasmids that are pieces of genetic material existing outside the main genome. Plasmids can be used as vectors for introducing foreign genes into the bacteria that can impart new synthetic capabilities to an otherwise “wild” bacterial strain. Many bacteria exhibit motility by means of one or more hairlike appendages called flagella. Bacteria reproduce by dividing into equal parts, a process termed binary fission.

Under adverse conditions, certain microorganisms produce spores that germinate upon return to a favorable environment. Spores are a particularly stable form or state of bacteria that may survive dryness and temperature extremes. Some microorganisms form spores at a stage in their normal life cycle.

Many species may, under appropriate circumstances, become surrounded by gelatinous material that provides a means of attachment and some protection from other organisms. If many cells share the same gelatinous covering, it is called a slime; otherwise each is said to have a capsule.

BACTERIA AND DISEASE

A century ago in the United State and even today in the less developed countries, at least 25% of the children died of bacteria infections before reaching puberty. In the united states and other Western nations, this figure is now below 5% as a result of improved sanitation, hygiene, and medical care.

The control of Typhoid fever alone is perhaps the greatest triumph of organized preventive medicine. As late as 1900 the annual death rate from typhoid fever in United States was more 30 per 100, 000; by 1944 the rate hade decreased to 0,4 per 100, 000.

For the world as the whole however, typhoid fever remain a major disease.

History.

To account for the spread of certain disease, thoughtful people since ancient times postulated the existence of transmissible agents of infections invisible to the naked eye, In 1546 the Italian physician Girolamo fracastoro proposed the germ theory of disease, describing the transmission of disease by ‘Seminaria’ or living germ. Visualization of germ could not take place until the microscope had been invented. However, bacteria and other microscopic organism were first seen in 1676 by a Dutch linen-draper, Antony Van Leeuwenhoek, who made single lens microscope with sufficient magnification to observe the major types of bacteria as well as protozoans, yeasts, and one-celled algae. Leeuwenhoek is regarded as the father of bacteriology.

The first important classification of bacteria was made in the early 1800s. In 1829, Christian Gottfried established the genus Bacterium, using a term formed from the greek word Bacterion , signifying a rod.

The entire subject of bacteriology has taken its common name from the prominence of rodlike forms of bacteria, now called bacilli. Eventually, bacteria were classified as plants; this remained the dominant view until the 1960s. Bacteria are now clasisified as Monerans.

An experimental science of bacteriology emerged slowly and required the development of special methodology. The key was the use of sterile (germ-free) materials and antiseptic technique; a singe contaminating cell can ruin an experiment in bacteriology. Only after learning to avoid such contamination could investigators recognized the existing variety of bacteria, their distribution, and their major rules.