Unit VI: Application of Microbes and Cryptogams

Algae are economically important in a variety of ways. The natural substance can be used as a food source, a fodder, in fish farming, and as a fertilizer. It also plays a key role in alkaline reclaiming, can be used as a soil binding agent, and is used in a variety of commercial products.

Uses For Algae

Food

Numerous cultures around the world consider algae an important source of nourishment. Citizens living in European countries such as Ireland, Scotland, France, Germany, Norway, and Sweden, as well as populations living in North and South America, and Asian nations such as China and Japan use algae as a key ingredient in a number of local dishes. These meals can include algae as part of a salad, accompanying meat in a fried dish, as a topping on oatmeal, or even in liquid form as an extract in a nutritious smoothie.

Algae contains several healthy elements including carbohydrates, fats, proteins, and vitamins A, B, C, and E. Not only is algae considered by many consumers worldwide to be a low cost source of protein, but it also contains a number of important minerals such as iron, potassium, magnesium, calcium, manganese, and zinc. Foods which commonly contain algae include a variety of dairy products such as milk, ice cream, cheese, whipped topping, as well as syrup, icing, fruit juice, and even salad dressings. Brown algae, in particular, is used in order to stabilize, thicken, and emulsify numerous food products, while red algae is used in the preparation of various semi-solid products as wide-ranging as medicines, cosmetics, and in the production of a wide array of foods.

Fodder

Algae, especially seaweed, is used as a feed for a variety of farm animals. For example, Rhodymenia palmate, or so-called "Sheep’s weed," is used in order to feed livestock such as cattle and chickens. Algae is used as fodder in various countries, such as the northern European nations of Sweden, Denmark, and Norway, as well as in Scotland, China, New Zealand, and throughout North and South America.

Fertilizer

The two most common varieties of algae used in the manufacture of fertilizer are large red and brown. In particular, these two types of algae are utilized in areas located near the ocean. Liquid fertilizer can also be produced using a concentrated seaweed extract. The reasons why this type of fertilizer is so popular involves the organism’s ability to repair levels of nitrogen already present in the soil. For example, rice producers in India typically employ blue-green algae in order to fertilize their agricultural fields.

Reclaiming Alkaline

In many countries, such as India, fields that once produced large agricultural yields can no longer be used due to high concentrations of alkalinity in the soil. In order for crops to eventually be grown in these lands, often referred to as "Usar" lands, the ph level must be lowered and the ability of the soil to hold onto water must be increased. This process can be achieved using blue-green algae.

Binding Agent

Algae can also be used to help bind soil together. The use of algae to aid in the healthy formation of soil is important in the protection against natural processes such as erosion.

Algae Products

Algae is used as a key ingredient in various food products. The substance can either be used as an additive or can act as a thickener in many types of food products. Algae can also be found in household products, such as toothpaste and various pharmaceuticals. A type of algae, known as carrageenan, is often added to dairy products such as cheese and sour cream in order to give them a denser texture. Alginic acid, which can be found in algae, is used to stabilize foods such as milkshakes, malts, and mayonnaise. Consumers might also be familiar with the green paper-like sheets used to wrap sushi. This product, called nori, is actually a leafy form of algae which was traditionally grown in Japan and contains plenty of healthy nutrients and assorted vitamins.

Gelatin is used in the production of numerous edible products. In fact, this substance is made up of a type of algae known as agar. Purportedly first used in 17^th century China, gelatin acts to solidify liquids found in such popular products such as pie crusts and fillings.

Purple-colored algae, also known as Porphyra, is commonly used in Japan and is known as nori, which is used to wrap up sushi rolls. In Korea, this same substance is known as gim. In Wales, this type of algae is referred to as laverbread, which is traditionally served for breakfast along with bacon and cockles (a type of mollusk). In Ireland, residents stew or boil the algae, thus making it into a pink colored jelly.

In the manufacturing of toothpaste, algae is used in order to thicken what would otherwise be a runny substance and transform it into a partially solid form. This particular form of algae is safe to consume and dissolves during the tooth brushing process.

Mycorrhizae literally translates to “fungus-root.” Mycorrhiza defines a (generally) mutually beneficial relationship between the root of a plant and a fungus that colonizes the plant root. In many plants, mycorrhiza are fungi that grow inside the plant’s roots, or on the surfaces of the roots. The plant and the fungus have a mutually beneficial relationship, where the fungus facilitates water and nutrient uptake in the plant, and the plant provides food and nutrients created by photosynthesis to the fungus. This exchange is a significant factor in nutrient cycles and the ecology, evolution, and physiology of plants.

In some cases, the relationship is not mutually beneficial. Sometimes, the fungus is mildly harmful to the plant, and at other times, the plant feeds from the fungus.

Not all plants will have mycorrhizal associations. In environments in which water and nutrients are abundant in the soil, plants do not require the assistance of mycorrhizal fungi, nor might mycorrhizal fungi germinate and grow in such environments.

Types of Mycorrhizae

There are two predominant types of mycorrhizae: ectomycorrhizae, and endomycorrhizae. They are classified by where the fungi colonize on the plants.

Ectomycorrhiza

Ectomycorrhiza tend to form mutual symbiotic relationships with woody plants, including birch, beech, willow, pine, oak, spruce, and fir. Ectomycorrhizal relationships are characterized by an intercellular surface known as the Hartig Net. The Hartig Net consists of highly branched hyphae connecting the epidermal and cortical root cells. Additionally, ectomycorrhiza can be identified by the formation of a dense hyphal sheath surrounding the root’s surface. This is known as the mantle. In other words, ectomycorrhiza live only on the outside of the root. Overall, only 5-10% of terrestrial plant species have ectomycorrhiza.

Endomycorrhiza

On the other hand, endomycorrhizae are found in over 80% of extant plant species -including crops and greenhouse plants such as most vegetables, grasses, flowers, and fruit trees. Endomycorrhizal relationships are characterized by a penetration of the cortical cells by the fungi and the formation of arbuscules and vesicles by the fungi. In other words, endomycorrhiza have an exchange mechanism on the inside of the root, with the fungi’s hyphae extending outside of the root. It is a more invasive relationship compared to that of the ectomycorrhiza.

Endomycorrhiza are further subdivided into specific types: Arbuscular Mycorrhizae, Ericaceous Mycorrhizae, Arbutoid Mycorrhizae, and Orchidaceous Mycorrhizae.

Examples of Mycorrhiza

Orchid Mycorrhiza

As mentioned above, some orchids cannot photosynthesize prior to the seedling stage. Other orchids are entirely non-photosynthetic. All orchids, however, depend on the sugars provided by their fungal partner for at least some part of their lives. Orchid seeds require fungal invasion in order to germinate because, independently, the seedlings cannot acquire enough nutrients to grow. In this relationship, the orchid parasitizes the fungus that invades its roots. Once the seed coat ruptures and roots begin to emerge, the hyphae of orchidaceous mycorrhiza penetrate the root’s cells and create hyphal coils, or pelotons, which are sites of nutrient exchange.

Arbuscular Mycorrhiza

Arbuscular mycorrhizae are the most widespread of the micorrhizae species and are well known for their notably high affinity for phosphorus and ability for nutrient uptake. They form arbuscules, which are the sites of exchange for nutrients such as phosphorus, carbon, and water. The fungi involved in this mycorrhizal association are members of the zygomycota family and appear to be obligate symbionts. In other words, the fungi cannot grow in the absence of their plant host.

Ericaceous Mycorrhiza

Ericaceous mycorrhizae is generally found on plants of the order Ericales and in inhospitable, acidic environments. While they do penetrate and invaginate the root cells, ericoid mycorrhiza do not create arbuscules. They do, however, help regulate the plant’s acquisition of minerals including iron, manganese, and aluminum. Additionally, mycorrhizal fungi form hyphal coils outside of the root cells, significantly increasing root volume.

Arbutoid Mycorrhiza

Arbutoid mycorrhiza are a type of endomycorrhizal fungi that look similar to ectomycorrhizal fungi. They form a fungal sheath that encompasses the roots of the plant; however, the hyphae of the arbutoid mycorrhiza penetrate the cortical cells of plant roots, differentiating it from ectomycorrhizal fungi.

Ectotrophic Mycorrhiza

The fungi involved in this mycorrhizal association are from the Ascomyota and Basidiomyota families. They are found in many trees in cooler environments. Unlike their wood-rotting family members, these fungi are not adapted to degrade cellulose and other plant materials; instead, they derive their nutrients and sugars from the roots of their living plant host.

Plant Benefits from Mycorrhizae

Mycorrhiza associations are particularly beneficial in areas where the soil does not contain sufficient nitrogen and phosphorus, as well as in areas where water is not easily accessible. Because the mycorrhizal mycelia are much finer and smaller in diameter than roots and root hairs, they vastly increase the surface area for absorption of water, phosphorus, amino acids, and nitrogen—almost like a second set of roots! As these nutrients are essential for plant growth, plants with mycorrhizal associations have a leg-up on their non-mycorrhizal associated counterparts that rely solely on roots for the uptake of materials. Without mycorrhiza, plants can be out-competed, possibly leading to a change in the plant composition of the area.

Additionally, studies have found that plants with mycorrhizal associations are more resistant to certain soil-borne diseases. In fact, mycorrhizal fungi can be an effective method of disease control. In the case of sheathing mycorrhiza, they create a physical barrier between pathogens and plant roots. Mycorrhiza also thicken the root’s cell walls through lignifications and the production of other carbohydrates; compete with pathogens for the uptake of essential nutrients; stimulate plant production of metabolites that increases resistance to disease; stimulate flavonolic wall infusions that prevent lesion formation and invasion by pathogens; and increase plant root concentrations of orthodihydorxy phenol and other allochemicals to deter pathogenic activity. In addition to disease resistance, mycorrhizal fungi can also impart to its host plant resistance to toxicity and resistance to insects, ultimately improving plant fitness and vigor.

In more complex relationships, mycorrhizal fungi can connect individual plants within a mycorrhizal network. This network functions to transport materials such as water, carbon, and other nutrients from plant to plant, and even provides some type of defense communication via chemicals signifying an attack on an individual within the network. Not only can plants use these signals to start producing natural insect repellants, they can also use them to start producing an attractant to bring in natural predators of the plant’s pests!

In some cases, mycorrhizal fungi allow plants to bypass the need for soil uptake, such as trees in dystrophic forests. Here, phosphates and other nutrients are taken directly from the leaf litter via mycorrhizal hyphae.

Mycorrhizal fungi are also able to interact with and change the environment in the favor of the host plants—namely, by improving soil structure and quality. The filaments of mycorrhizal fungi create humic compounds, polysaccharides, and glycoproteins that bind soils, increase soil porosity, and promote aeration and water movement into the soil. In environments that have highly compacted or sandy soils, improved soil structure can be more important for plant survival than nutrient uptake.

Some ectomycorrhizal associations create structures that host nitrogen-fixing bacteria, which would largely contribute to the amount of nitrogen taken up by plants in nutrient-poor environments, and would play a large part in the nitrogen cycle. The mycorrhizal fungi, however, do not fix nitrogen themselves.

Fungi Benefits from Plants

When the plant is provided with enough water and nutrients, it is able to photosynthesis and produce glucose and sucrose—some of which is made directly accessible to the mycorrhizal fungi. The fungi are also provided with photosynthetically fixed carbon from the host, which functions as a trigger for nitrogen uptake and transport by the fungi. All of this is necessary for fungal growth and reproduction.

Fungi include hundreds of species which are of tremendous economic importance to man. In fact our lives are intimately linked with those of fungi. Hardly a day passes when we are not benefited or harmed directly or indirectly by these organisms.

They play an important role in medicine yielding antibiotics, in agriculture by maintaining the fertility of the soil and causing crop and fruit diseases, forming basis of many industries and as important means of food. Some of the fungi are important research tools in the study of fundamental biological processes.

1. Role of Fungi in Medicine:

Some fungi produce substances which help to cure diseases caused by the pathogenic microorganisms. These substances are called the antibiotics.

The term antibiotic, therefore, denotes an organic substance, produced by a microorganism, which inhibits the growth of certain other microorganisms. The most important antibiotics are produced by the moulds, actinomycetes or bacteria.

They are used to combat the evil effects of pathogenic bacteria and viruses. The use of antibiotics is not limited to disease treatment.

The addition to certain antibiotics in small amounts to the feed of slaughter animals promotes rapid growth and improves the quality of the meat products. Application of an antibiotic to surface of freshly killed poultry preserves the fresh-killed taste during long periods of refrigeration.

The discovery of antibiotic agents as drugs is comparatively a recent history. The role of fungi m producing antibiotic substances was first established by Sir Alexander Fleming in 1929.

He extracted the great antibiotic drug Penicillin from Penicillium notatum. It was the first antibiotic to be widely used. Penicillin is an organic substance lethal to microbes. It is far more effective than ordinary drugs and germicides.

2. Role of Fungi in Industry:

The industrial uses of fungi are many and varied. In fact the fungi form the basis of many important industries. There are a number of industrial processes in which the biochemical activities of certain fungi are harnessed to good account.

(i) Alcoholic fermentation:

It is the basis of two important industries in India or rather all over the world. These are brewing and baking. Both are dependent on the fact that the fermentation of sugar solutions by yeasts produces ethyl alcohol and carbon dioxide.

In brewing or wine making industry alcohol is the important product. The other by-product which is carbon dioxide was formerly allowed to escape as a useless thing.

Now carbon dioxide is also considered a valuable by-product. It is collected, solidified and sold as “dry ice”. In the baking or bread- making industry CO₂ is the useful product.

(ii) Enzyme preparations:

Takamine on the basis of his intensive study of the enzymes produced by Aspergillus flavus-oryzae series has introduced in the market a few products of high enzymic activity. These are Digestin, Polyzime, Taka diastase, etc. They are used for dextrinization of starch and desiring of textiles.

Cultures of Aspergillus niger and A. oryzae on trays of moist, sterile bran yield a well-known amylase which contains two starch splitting components.

Invertase is extracted from Saccharoymces cerevisiae. It has many industrial uses. It hydrolyses sucrose to a mixture of glucose and fructose.

(iii) Preparation of organic acids:

The important organic acids produced commercially as the result of the biochemical activities of moulds are oxalic acid, citric acid, gluconic acid, gallic acid, fumaric acid, etc.

Oxalic acid is the fermentation product of Aspergillus niger. Citric acid is made by mould fermentation. Many species of Penicillium are used for the purpose. The acid is produced on a commercial scale and is cheaper than the acid made from the citrus fruits.

The gluconic acid is prepared from sugars. The moulds chiefly employed for this purpose are some species of Penicillium and Aspergillus.

(iv) Gibberellins:

These are plant hormones produced by the fungus Gibberella fujikuroi which cause a disease of rice accompanied by abnormal elongation. Gibberellin is used to accelerate growth of several horticultural crops.

(v) Cheese Industry:

Certain fungi popularly known as the cheese moulds play an important role in the refining of cheese. They give cheese a characteristic texture and flavour.

(vi) Manufacture of Proteins:

As a supplement to the normal diet, some fungi particularly the yeasts are employed to synthesize proteins. The yeast (Saccharomyces cerevisiae and Candida utilis) contain high percentage of protein of great nutritive value.

They are grown with ammonia as the source of nitrogen and molasses as the source of carbon. The manufactured product is called Food Yeast. It contains 15% protein and B group of vitamins.

(vii) Vitamins:

The yeasts, are the best source of vitamin B complex. A number of preparations of high potency have been made from the dried yeast or yeast extracts and sold in the market.

A number of moulds and yeasts are utilised in the synthesis of Ergosterol which contains Vitamin D. Riboflavin—another vitamin useful both in human and animal food—is obtained from a filamentous yeast, Ashby gossypii.

3. Role of Fungi in Agriculture:

The fungi play both a negative and a positive role in agriculture.

A. Negative Role:

They have a negative value because they are the causative agents of different diseases of our crop, fruit and other economic plants. These fungal diseases take a heavy toll and cause tremendous economic losses.

The modest estimate is that about 30 thousand different diseases (including bacterial and virus) attack the economic plants grown for food or commercial purposes.

B. Positive Role of Fungi:

Some soil fungi are beneficial to agriculture because they maintain the fertility of the soil. Some saprophytic fungi particularly in acid soils where bacterial activity is at its minimum cause decay and decomposition of dead bodies of plants and their wastes taking up the complex organic compounds (cellulose and lignin) by secreting enzymes.

The enzymes convert the fatty carbohydrate and nitrogenous constituents into simpler compounds such as carbon dioxide, water, ammonia, hydrogen sulphide, etc.

Some of these return to the soil to form humus and the rest of the air from where they can again be used as raw material for food synthesis. There are fungi in the soil which produce more ammonia from proteins than the ammonifying bacteria.

Ecological Importance of Bryophytes

Bryophytes have great ecological importance. Mosses and lichens are the first organisms to colonise rocks.

• They decompose the rock making it suitable for the growth of higher plants. The acid secreted by lichens, death and decay of mosses helps in soil formation

• Bryophytes grow densely so act as soil binders

• Mosses play an important role in bog succession. Mosses can change the landscape from open soil to climax forest. The thick mat formed of mosses forms suitable substratum for germination of hydrophilic seeds due to the presence of water and humus. In the course of time, the dead and decayed mosses and hydrophilic plants form a solid soil for mesophytic development

• They prevent soil erosion by reducing the impact of the falling rain

• They reduce the amount of run-off water due to their water holding capacity

• They help in recycling of the nutrients

• They act as a rock builder. Certain mosses (Bryum) along with algae, present in calcium bicarbonate rich shallow water or lakes form calcareous (lime) rock-like deposits around these plants. These plants decompose bicarbonate ions resulting in the precipitation of insoluble calcium carbonate. This mineral deposit continues to grow and extends over several hundred square feet area.

Importance of Bryophytes

1. Medicinal uses:

   • Sphagnum is used in surgical dressing due to its high absorptive power and some antiseptic property for filling absorptive bandages in place of cotton for the treatment of boils and discharging wounds

   • Marchantia has been used to cure pulmonary tuberculosis and affliction of liver

   • The decoction of dried sphagnum is used in the treatment of acute haemorrhage and eye infections

   • Peat-tar is antiseptic and used as a preservative. Sphagnol, which is a distillate of peat-tar is used to treat skin disease

   • Polytrichium species has shown to dissolve stone in kidney and gall bladder

   • Antibiotic substances can be extracted from certain bryophytes having antibiotic properties

2. In research: Mosses and liverworts are used in research in the field of genetics. The mechanism of sex determination in the plant is discovered in liverworts

3. Packing material: Dried mosses make an excellent packing material for fragile goods like glassware, bulbs. For trans-shipment of living material such as cuttings and seedlings as they have water retention capacity

4. Food: Some mosses provide food for herbaceous mammals, birds and other mammals

5. As Indicator plants: Some bryophytes grow in a specialised area and can be used as an indicator for acidity and basicity of the soil. E.g. Polytrichum indicated the acidity of the soil, Tortella species grow well in the soil rich in lime or other bases and occur as calcicoles

6. In seedbeds: Because of its water retention capacity, it is used in seedbeds, greenhouses, nurseries to root cuttings. Sphagnum is also used to maintain high soil acidity required by certain plants

7. Peat formation: Sphagnum is also known as peat moss. Peat is formed by slowing down the decaying process. The gradual compression and carbonisation of partially decomposed vegetative matter in bogs give rise to a dark-coloured substance called Peat.

   • It is used as a fuel

   • Lower layers of peat form coal

   • Peat is also used in the production of ethyl alcohol, ammonium sulphate, ammonia, dye, paraffin, tannins etc.

   • It improves soil texture in horticulture

8. Formation of stone: The travertine rock deposits are extensively used as a building stone