MUKHLiS TANVEER JAN KURD

Tanveer Biology Concepts

Kingdom Prokaryotae

Some spirochetes occasionally reach 500 µm in length whereas

Staphylococci are 0.75 – 1.25 µ in diameter.

Epulopiscium fishelsoni, recently a huge bacterium has been discovered in the intestine of the brown surgeonfish, Acanthurus nigrofuscus. Epulopiscium fishelsoni grows as large as 600 µm by 80 µm, a little smaller than a printed hyphen. It is now clear that a few bacteria are much larger than the average eukaryotic cell.

All bacterial cells invariably have a cell membrane, cytoplasm, ribosome, and chromatin bodies.

The majority have a cell wall, which gives shape to the bacterial cell.

Specific structures like capsule, slime, flagella, Pili, fimbriae and granules are not found in all bacteria.

FLAGELLA

These are extremely thin, hair like appendages.

Origin ;

They come out through cell wall and originate from basal body, structure just beneath the cell membrane in the cytoplasm.

they are made up of protein Flagellin.

Classification of bacteria;

On the basis of presence of flagella. Pattern of attachment of flagella and the number of flagella present bacteria are classified into different taxonomic groups.

Atrichous; It means bacteria are without any flagella.

Monotrichous; when single polar flagellum is present then condition is known as monotrichous.

Lophotrichous; if tuft of flagella is present only at one pole of bacteria then these are lophotrichous flagella.

Amphitrichous; It is a condition when tuft of flagella at each of two poles is present.

Peritrichous; in peritrichousform, flagella surround the whole cell.

Occurrence

Most of bacilli and spiral shaped bacteria have flagella. Cocci very rarely have flagella.

Function

Motility; Primary function of flagella is to help in motility.

Chemotaxis; with the help of flagella, flagellate bacteria can also detect and move in response to chemical signals which is a type of behavior called as chemotaxis.

PILI

These are hollow, no helical, filamentous appendages. Pili are smaller than flagella and are not involved in motility.

Occurrence

True pili are only present on gram-negative bacteria.

Composition;

they are made up of special protein called pilin.

Function

Conjugation; They are primarily involved in a mating process between cells called conjugation process.

Attachment; Some pili function as a means of attachment of bacteria to various surfaces.

Several bacterial groups lack the cell wall structure characteristic of gram positive or gram negative bacteria,

Mycoplasmas; These bacteria have no cell wall at all.

Archaeobacteria; Cell walls of archaeobacteria are different from eubacteria. They do not contain peptidoglycan. Their cell walls are composed of proteins, glycoproteins and polysaccharides.

CELL MEMBRANE

LOCATION;

Just beneath the cell wall is the cell membrane or plasma membrane and completely surrounds the cytoplasm.

DELICACY;

It is very thin and flexible. Plasma membrane is very delicate in nature any damage to it results in death of the organism.

Differ:

It differs from eukaryotic membranes in lacking sterols such as cholesterol.

FUNCTION

Cell membrane regulates the transport of proteins, nutrients, sugar and electrons or other metabolites.

The plasma membranes of bacteria also contain enzymes for respiratory metabolism.

Respiratory enzymes are also present on the mesosomes

GRANULES AND STORAGE BODIES

STROAGE NUTRIENTS

Since bacteria exist in a very competitive environment where nutrients are usually in short supply.

They tend to store extra nutrients when possible. These may be glycogen, sulphur, fat and phosphate.

WASTES

In addition, cells contain waste materials that are subsequently excreted. For example, common waste materials are alcohol, lactic acid and acetic acid.

SPORES

Metabolically dormant (inactive) bodies with thick wall are called as spores.

Certain bacteria produces spores.

Types.

There are two types of spores.

Exospores: These are produced external to vegetative cells.

Endospores : These are produces within the vegetative cells,

DORMANCY ;

They are metabolically dormant bodies and are produced at a late stage of cell growth.

RESISTANT ;

Spores are resistant to adverse physical environmental conditions such as light, high temperature, desiccation, PH and chemical agents.

GERMINATION;

; Under favorable conditions they germinate and form vegetative cells.

CYSTS

Cysts are dormant, thick-walled, desiccation resistant forms and develop during differentiation of vegetative cells which can germinate under suitable condition. They are not heat resistant.

NUTRITION IN BACTERIA

Like other organisms bacteria. Need energy for their growth, maintenance and reproduction. There are two types.

Heterotrophic bacteria

Autotrophic Bacteria

HETEROTROPHIC BACTERIA

Most bacteria are heterotrophic i.e., they cannot synthesize their organic compounds from simple inorganic substances. They live either as saprophytes or as parasites.

Saprophytic bacteria

They get their food from dead organic matter. Soil is full of organic compounds in the form of humus. Humus is the material resulting from the partial decay of plants and animals. Many soil inhabiting bacteria have very extensive enzyme system that breaks down the complex substances of humus to simpler compounds. The bacteria can then absorb and utilize these simpler substances as a source of energy.

Parasitic bacteria

Parasitic bacteria for their nutrition are fully dependent on their host.

AUTOTROPHIC BACTERIA

Some kinds of bacteria are autotrophic i.e., they can synthesize organic compounds which are necessary for their survival from inorganic substances.

These bacteria may be separated into two groups:

photosynthetic autotrophs and

2Chemosynthetic autotrophs.

Photosynthetic bacteria

They possess chlorophyll which differs from the chlorophyll green plants. Unlike most green plant have their chlorophyll in chloroplasts, bacterial chlorophyll is dispersed in the cytoplasm. During photosynthesis the autotrophic bacteria utilize hydrogen sulphide (H2S) instead of water as a hydrogen source and liberate sulphur instead of oxygen. The overall reaction of photosynthesis in photosynthetic bacteria can be written as:

EXAMPLES.

Green sulphur bacteria, purple sulphur bacteria and purple non-sulphur bacteria are photosynthetic bacteria.

Chemosynthetic bacteria

They oxidize inorganic compounds like ammonia, nitrate, nitrite, sulphur or ferrous iron and trap the energy thus released for their synthetic reactions.

EXAMPLES

Nitrifying bacteria are chemosynthetic.

RESPIRATION IN BACTERIA

Respiration is the process by which energy is made available to cells in a step by step breakdown of carbon chain molecules in the cells.

Respiration in bacteria may be aerobic (requiring free oxygen) or anaerobic not requiring free oxygen. There are several categories of bacteria.

Aerobic bacteria

Bacteria, which are able to grow in the presence of oxygen, are called aerobic bacteria. Pseudomonas is an aerobic bacterium.

Anaerobic bacteria

Those which can grow in the absence of oxygen are known as anaerobic bacteria. Spirochete is an anaerobic bacterium.

Facultative bacteria

Some bacteria are neither aerobic nor anaerobic, but facultative. Facultative bacteria grow either in the presence or absence of oxygen. E.coli is a facultative anaerobic bacterium

Microaerophilic.

Some bacteria require a low concentration of oxygen for growth and are known as microaerophilic. Campylobacter is a microaerophilic bacterium.

GROWTH AND REPRODUCTION IN BACTERIA

Bacterial growth refers commonly to increase in number of bacterial cells.

Binary fission

Bacteria increase in number by an asexual means of reproduction, called binary fission. In binary fission

parent cell enlarges,

its chromosome duplicates,

Plasma membrane pinches inward at the center of the cell.

When nuclear material has been evenly distributed, the cell wall grows inward to separate cell into two.

This sequence is repeated at intervals by each new daughter cell which in turn increases the population of cells. Once the division is complete, bacteria grow and develop their unique features.

Generation time.

The interval of time until the completion of next division is known as generation time.

The important chemical agents used for disinfection are oxidizing and reducing agents.

For example halogens and phenols, hydrogen peroxide, potassium permanganate, alcohol and formaldehyde etc.

ANTIBIOTICS

Antibiotics

Chemotherapeutic agents and antibiotics work with natural defense and stop the growth of bacteria and other microbes.

They destroy or inhibit the growth of microorganisms in living tissues.

Antibiotics is a Greek word (anti-against-and bios life). Antibiotics are the chemotherapeutic chemical substances which are used in treatment of infectious diseases.

Examples

These are sulfonamides, tetracycline, penicillin, etc.

TYPES OF ANTIBIOTICS

Microbicidal ; is one that kills the microbes immediately e.g. Tetracycline, penicillin,

Microbistatic inhibits the reproductive capacities of the cells and maintains the microbial population at constant size. e.g. Sulfonamides

MODE OF ACTION OF ANTIBIOTICS

Modes of action of different chemical and physical agents of control vary.

Damage can result malfunctions in cell wall. Cell membranes, cytoplasmic enzymes, or nucleic acid.

SOURCE OF ANTIBIOTICS

Antibiotics are synthesized and secreted by certain bacteria, actinomycetes and fungi. Today, some antibiotics are synthesized in the laboratory. However, their origins are living cells.

USE OF ANTIBIOTICS

To determine drug of choice, one must know its mode of action, possible adverse side effects in the human beings.

Use antibiotics as prescribed by the physicians.

Take dose at regular intervals and complete the treatment as advised by the doctor.

MISUSE OF ANTIBIOTICS

DRUG RESISTANCE ;

Massive quantities of antibiotics are being prepared and used, which are followed by the widespread problems of drug resistance in microorganisms. This results in an increasing resistance against disease treatments.

METABOLIC PROBLEMS ;

Misused antibiotics can interact with the human metabolism and in severe cases can cause death of human beings.

ALLERGIC PROBLEMS

Misuse of antibiotic such as penicillin can cause allergic reactions.

DEAFNESS

Similarly streptomycin can affect auditory nerve thus causing deafness.

DISCOLORATION OF TEETH

Tetracycline and its related compounds cause permanent discoloration of teeth in young children.

IMMUNIZATION AND VACCINATION

Methods of prevention and treatment that have been introduced to control microbial diseases include

antisepsis (procedures to eliminate or reduce the possibility of infection),

immunization (e.g. vaccination),

Chemotherapy; Use of chemicals and antibiotics.

Public health measures (e.g. water purification, sewage disposal, and food preservation).

Vaccine.

A preparation of killed microorganisms or living attenuated organisms that is administered to produce or artificially increase immunity to a particular disease is called as vaccine.

Vaccination

The procedure of inoculation of vaccine to produce or artificially increase immunity to a particular disease is called as vaccination.

Immunization

The phenomenon of development and increment of immunity due to inoculation of disease is called as immunization.

them is assimilated through the Calvin cycle.

FOOD STORAGE

Reserve food material in cyanobacteria is glycogen.

REPRODUCTION

Cyanobacteria reproduce by binary fission, fragmentation. In cyanobacteria hormogonia, akinetes and heterocysts are present.

ECONOMIC IMPORTANCE OF CYANOBACTERIA

GAINS

Cyanobacteria have heterocysts, which are helpful in the fixation of atmospheric nitrogen.

They help in reclamation of alkaline soils.

They release O2 in the environment due to their photosynthetic activity.

Oscillatoria and few other cyanobacteria can be used as pollution indicator.

They have symbiotic relationship with protozoa, fungi, and nitrogen fixing species form associations with angiosperms. They are photosynthetic partner in most of lichen association.

Super Blue green algae are basically expensive pond scum, in which cyanobacterium a singled celled organism is that produces its own food through photosynthesis. It serves as a “complete whole food” which contain 60% protein with all essential amino acids in perfect balance.

Losses

Many species of cyanobacteria form water blooms where they often impart unpleasant smell and due to large amount of suspended organic matter water becomes unfit for consumption.

Some species produce toxins that kill live stock and other animals that drink the water.

NOSTOC

Habitat and occurrence

Nostoc is common as terrestrial and subaerial cyanobacterium. It is widely distributed in alkaline soils and on moist rocks and cliffs.

Body Forms

Nostoc forms a jelly like mass in which numerous filaments are embedded.

Structure

Individual cells are mostly spherical but some times barrel shaped or cylindrical.

Trichomes are unbranched and appear beaded.

All cells in trichome are mostly similar in structure but at intervals are found slightly large, round, light yellowish thick walled cells called as heterocysts.

Trichome mostly breaks near heterocyst and forms hormogonia and thus help in fragmentation.

Reproduction

There is no s****l reproduction but it reproduces asexually by formation of hormogonia.

Hormogonia Formation ;

Hormogonia are formed when filament break at different points into smaller pieces. This is due to death and decay of an ordinary cell or the heterocyst may serve as a breaking point.

Akinetes formation.

Reproduction can also be due to akinetes formation. Akinetes are thick walled, enlarged vegetative cells which accumulate food and become resting cells. On arrival of favorable conditions they form normal vegetative cell.

During the course of evolutionary history, organisms in the kingdom protista have evolved diversity in their

size and structure,

means of locomotion,

ways of obtaining nutrients,

interactions with other organisms,

habitat and

modes of reproduction.

Based on the diversity, most biologists regard the protist kingdom as a polyphyletic group of organisms; that is, the protists probably do not share a single common ancestor.

Margulis and Schwartz have listed 27 phyla to accommodate this diverse assemblage of organism.

Major Groups of Protista

Protozoa: Animal –like Protists

All protozoans are unicellular. Most ingest their food by endocytosis. A summary or protozoan diversity is given in Table 7.1

Table 7.1 some groups of protozoa

Common Name

Form

locomotion

examples

Amoebae

Unicellular, no definite shape

pseudopods

Amoeba, entamoeba,

Zooflagellates

Unicellular,some colonial

One or more flagella

Trypanosome, Eugleria,

Actinopods

Unicellular

Pseudopods

Radiolarians

Foraminifera

Unicellular

Pseudopods

Forams

Apicomplexans

Unicellular

None

Plasmodium

Ciliates

Unicellular

Cilia

Paramecium, vorticella, stentor.

(Chrysophyta)

Body Form.

Most diatoms are unicellular

Locomtion

They have usually no locomotry organs

Pigments

They have Chl.a, Chl. C . carotenes including Fucoxanthin

Shells

The cell wall of each diatom consists of two shells that overlap where they fit together, much like a petri dish. Silica is deposited in the shell, and this glasslike material is laid down in intricate patterns.

Ecological importance.

Diatoms are the major producers in the aquatic (marine and freshwater) ecosystems because of their extremely large numbers.

Diatoms are very aquatic food chains.

Examples. Diatoma, Frequilaria, Pinnularia

important in

Brown Algae.(Phaeophyta).

Body Forms.

Brown algae include the giants of the protest kingdom. All brown algae are multicellular and range from a few centimeters to approximately 75 meters in length.

Locomtion

They have two flagella usually on reproductive cells.

Pigments

They have Chl.a, Chl. C . carotenes including Fucoxanthin

Kelps

The largest brown algae, called the kelps are tough and leathery in appearance.

They are edible and may be used to overcome shortage of food in the world.

Body structures.

They possess leafl ike blades, stem like stipes, and root like anchoring holdfast.

Occurrence

Brown algae are common in cooler marine waters, especially along rocky coastlines in the intertidal zone.

Examples.

Fucus, Macrocystis. Laminaria (a brown algae having blades stipes and holdfast.).

Red Algae.(Rhodophyta).

Body Forms.

The multicellular body form of red algae is commonly composed of complex interwoven filaments that are delicate and feathery. A few red algae are flattened sheets of cells.

These may be unicellular.

Locomtion.

They have no locomotry organs. Most multicellular red algae attach to rocks or other substances by a basal holdfast.

Pigments

They have Chl.a, carotenes, Phycoerythrin.

Ecological Impotrance.

Some red algae incorporate calcium carbonate in their cell walls from the ocean and take part in building coral reefs along with coral animals.

Examples

Chondrus Polysiphonia (a representative red alga with world wide distribution)

Green Algae.(Chlorophyta)

Body Forms

Green algae exhibit diverse forms.

(a) Unicellular e.g. Chlamydomonas and Chlorella

(b) Cells with two halves e.g. Desmide.

(c) Colonial Volvox

(d) Filamentous spirogyra

(e) Having sheet like body. Ulva,

Locomtion

Most have flagella

Resemblance with Plants

Green algae have pigments, energy reserve products, and cells walls that are identical to those of plants.

Energy Reserves. Their main energy reserves are stored as starch.

Green algae are photosynthetic, with chlorophylla, chlorophyll b, and carotenoids present in the chloroplasts.

Cell wall. Most green algae possess cell walls with cellulose.

Because of these and other similarities it is generally accepted that plants arose from ancestral green algae. Evidence from RNA sequencing also indicates that green algae and the plants form a monophyletic lineage.

Chlorella is a unicellular non-motile green alga. Its habitat is fresh water ponds and ditches. It is easily cultured and has been used as an experimental organism in research on photosynthesis as well as being investigated as an alternate source of food

Importance of Algae.

Algae have great economic and environmental importance for us.

Marine algae are also source of many useful substances like algin, agar, carrageenan, and antiseptics.

Some algae such as kelps are edible and may be used to overcome shortage of food in the world.

Algae are major producers of the aquatic ecosystem, thus they play a basic role in food chains, providing food and oxygen to other organism.

Fungus like Protists.

Similarites

Some protists superficially resemble fungi in that they are not photosynthetic and some have bodies formed of thread like structures called hyphae.

Differences

However, fungus-like protists are not fungi for several reasons.

Fungi

Fungus Like Protists

Ø Fungi lack centrioles.

Ø They have cell wall of chitin.

Ø Many of these protists have centrioles.

Ø They produce cellulose as a major component of their cell walls,

Groups.

Two major groups of fungus-like protists are:

slime molds and 2. water molds (oomycotes).

Slime Molds (Myxomycota)

Feeding Stage.

The feeding stage of a slime mold is a plasmodium, a multinucleate mass of cytoplasm that can grow to 30 cm (1 ft) in diameter. The plasmodium,

streams over damp, decaying logs and leaf litter.

which is slimy in Appearance,

It often forms a network of channels that cover a large surface area.

As it creeps along, it ingests bacteria, yeasts, spores and decaying organic matter.

Reproductive stage.

When conditions become favourable again, spores germinate into bi_flagellated or amoeboid reproductive or swarm cells which unite to form diploid zygote.

During unfavorable condition, slime mold forms resistant haploid spore by meiosis within stalked structures called sporangia.

Zygote produces multinucleate plasmodium, each nucleus being diploid.

Physarum polycephalum

The plasmodial slime mold Physarum polycephalum is a model organism that has been used to study many fundamental biological processes, such as growth and differentiation, cytoplasmic streaming, and the function of cytoskeleton.

Water Molds (Oomycota)

Oomycotes show close relations with the fungi and have a similar structure, but are now regarded as more ancient group.

Their cell walls contain cellulose, not chitin.

Their hyphae are aseptate (without cross walls).

Oomycotes include a number of pathogenic organisms, including phytophthora infestans, which have played infamous roles in human history.

Phytophthora infestans

Phytophthora infestans was the cause of Irish potato famine of the 19th century. It causes a disease commonly known as late blight of potatoes.

Because of several rainy, cool summers in Ireland in the 1840’s, the water mold multiplied uncheched, causing potato tubers to rot in the fields.

Since potatoes were the staple of Irish peasants’ diet, many people (250,000 to more than 1 million) starved to death.

The famine prompted a mass migration out of Ireland to such countries as the United states

Kingdom Fungi

Deuteromycota (Deuteromycetes or Imperfect Fungi)

This heterogeneous group includes all such fungi in which s****l phase has not been observed.

Related with Other Groups.

Most of them are related to their sexually reproducing relatives of ascomycetes; however some are related to other two phyla (Zygomycota, Basidiomycota) as well. If s****l structures are found on an imperfect fungus, it is then reassigned to the appropriate phylum.

Base of Classification

Biologists now can classify most imperfect fungi on the basis of DNA

sequences, though s****l structures may not be found.

Parasexuality

Despite absence of s****l reproduction, imperfect fungi show special kind of genetic recombination, called parasexuality, in which portions of chromosomes of two nuclei lying in the same hypha are exchanged.

Examples.

Penicillium (blue, green molds), Aspergillus (brown molds), Alternaria, fusarium, helminthosporium are some of the economically important genera of Deuteromycetes (see economic importance of fungi).

Penicillium

Habitat.

Penicillium sp. (blue, green molds) are wide spread saprotrophic species common on decaying fruit, bread etc.

Its hyphae are septate.

Asexual reproduction.

Penicillium reproduces asexually by means of naked spores called conidia.

These are found in chains at the tips of special hyphae called conidiophores, which are branched. Brush-like arrangement of its conidia is characteristic of Penicillium.

These conidia give colour to the mycelia colony, which is circular. Mature conidia are easily and readily dispersed.

LAND ADAPTATIONS OF FUNGI.

Fungi although grow best in moist habitats, are found wherever organic matter is present. They are a successful group of land organisms, and possess several features in their body and reproduction that adapt them to their habit and terrestrial mode of life.

EXTENSIVE HYPHAL SYSTEM.

Extensive system of fast-spreading hyphae penetrate the substrate and enormously increase the contact and surface area for absorption.

RAPID CYTOPLASMIC FLOW

Cytoplasmic flow throughout the hyphae is responsible for their rapid growth and spread.

CHITIN

Chitin in their thickened hyphal wall is more resistant to decay than are cellulose and lignin found in plant cell wall.

BETTER DECOMPOSERS

They can even break down the lignin (in addition to cellulose) to obtain their nutrients. Most of the bacteria can not break these structure.

RHIZOIDES

In saprobes, certain modified hyphae called rhizoids anchor the fungus to the substrate and also digest and then absorb the food.

REPRODUCTIVE PROPERTIES

They are very well adapted to live on land due to lack of flagellated cells, non-motile spores and conidia efficient dispersal by wind.

They have thick-walled zygote and other resistant structures.

Hyphae may be modified in such a way as to enable them to reproduce themselves without dependence on external water.

MORE TOLERANT TO ENVIROMENTAL CONDITIONS.

Dry conditions.

They survive dry conditions in some resting stage or by producing resistant spores.

Hyperosmotic Conditions.

Many fungi are more tolerant than are bacteria to damage in hyperosmotic surroundings and high osmotic pressures such as in concentrated salt/sugar solutions as in jelly, jam etc.

Temperature.

Many can tolerate temperature extremes – 5 C below freezing and 50 C or more. Now you can tell why molds (e.g. Penicillium) can grow on oranges and jelly kept in a refrigerator, while generally bacteria cannot.

pH.

They can also tolerate a wide range of pH from 2 – 9.

FOOD STORAGE

Fungi store surplus food usually as lipid droplets or glycogen in the mycelium.

IMPORTANCE OF FUNGI

ECOLOGICAL IMPORTANCE

Fungi have great ecological impact. They are very important as decomposers and symbionts.

AS A DECOMPOSER

Fungi, along with saprobic bacteria, play vital role in the recycling of inorganic nutrients in the ecosystem. Without their activity all the essential nutrients would soon become locked up in the mounds of dead animals, plants, would be unavailable for use by organisms, and life would cease.

AS A SYMBIONTS

Mycorrhizal fungi improve the growth of plants with which they are associated. 95% of all kinds of vascular plants have this association.

SUCCESSION

Lichens growing on rocks break them, setting stage for other organisms during the course of ecological succession.

BIOINDICATORS

Lichens are very good bioindicators of air quality as they are very sensitive to pollution.

BIOREMEDIATION.

Some fungi are also used for bioremediation (degrading/ removing environmental poisons/ pollutants by organisms).

COMMERCIAL IMPORTANCE

Fungi cause economic gains as well as losses

ECONOMIC GAINS

Source of food

Edible Fungi. Certain fungi are edible. About 200 species of mushrooms (e.g. Agaricus sp), morels (e.g. Morchella esculenta), and truffles (underground fruiting bodies some Ascomycetes, e.g. tuber sp). The truffles (tuber species) are underground fruiting bodies that people find with the help of trained dogs or pigs.

Beware of poisonous mushrooms called the toadstools, such as death cap/death angel (amanita, a poisonous mushroom) and jack-O, latern mushroom (Omphalotus olearius whose dark).

Reindeer moss

(A lichen, not a moss) is used as food for reindeers and some other large animals in arctic / subarctic / boreal regions.

USE IN FOOD INDUSTRY.

Certain fungi are used in food industry

Yeast.

Because of their fermenting ability, yeasts (Saccharomyces cerevisiae) are used in the production of bread and liquor.

Penicillium species.

Penicillium species are used for giving flavor, aroma and characteristic colour to some cheese.

Aspergillus species.

Some species of Aspergillus are used for fermenting/producing soya sauce and soya paste from soya bean. Citric acid is also obtained from some Aspergillus species.

MEDICINAL VALUE.

Some fungi are source of antibiotics and some other drugs.

Penicillin.

Penicillin, first antibiotic to be ever discovered (by A. Fleming-1928) is obtained from Penicillium notatum.

Lovastatin.

Lovastatin is used for lowering blood cholesterol;

Cyclosporin

Cyclosporine obtained from a soil fungus is used in organ transplantation for preventing transplant rejection;

Ergotine.

Ergotine to relieve one kind of headache migraine.

Griseofulvin.

Griseofulvin is used to inhibit fungal growth.

TEXTILE INDUSTRY.

Some natural dyes obtained from lichens are used in textile industry.

GENETIC VALUE.

Yeasts are heavily used in genetic/molecular biological research because of their rapid generation and rapidly increasing pool of genetic and biochemical information.

Yeast were the first eukaryotes to be used by genetic engineers.

In 1983, a functional artificial chromosome was made in Saccharomyces cervisiae.

The same yeast was the first eukaryote whose genomic sequence was completely studied in 1996.

Yeasts are also being investigated for production of some hormones.

Pink bread mold Neurospora has also been used for genetic research.

ECONOMIC LOSSES.

Plant pathogens.

Fungi are responsible for many serious plant diseases because they produce several enzymes that can breakdown cellulose, lignin and even cutin.

All plants are susceptible to them.

Extensive damages due to rusts and smut diseases of wheat, corn, and rice prompted mass displacement, and starvation to death of many people.

Example of plant diseases due to fungi.

Powdery mildews (on grapes, rose, wheat etc.), ergot of rye, red rot of sugar cane, Potato wilt, cotton root rot, brown rot of peaches, plums, apricots and cherries , apple scab are some common diseases caused by fungi.

Animal Pathogens

Fungi also cause certain animal diseases

Ringworm and athlete’s foot

These are superficial fungi infections caused by certain imperfect fungi.

Candidiasis or candidosis

Candida albicans, a yeast, causes oral and vaginal thrush called as candidiasis or candidosis.

Histoplasmosis

Histoplasmosis is a serious infection of lungs caused by inhaling spores of a fungus (Histoplasma capsulatum) which is common in soil contaminated with bird’s feces.

If infection spreads into blood stream and then to other organs (which is very occasional), it can be serious and even fatal.

Aspergillosis

Aspergillus fumigates causes aspergillosis, but only in persons with defective immune system such as AIDS, and may cause death.

Aspergillus Toxicity

Some strains of Aspergillus produce one of the most carcinogenic (cancer causing) mycotoxins (toxins produced by fungi), called aflatoxins.

Aspergillus contaminates improperly stored grains such as peanuts and corn etc. milk, eggs and meat may also have small traces of aflatoxins.

Any moldy human food or animal forage product should be discarded.

Ergotism

Ergotism is caused by eating bread made from purple ergot contaminated rye flour.

The poisonous material in the ergot causes nervous spasm, convulsion, psychotic delusion and even gangrene.

HARMFUL DECOMPOSERS

15-50% of world’s fruit is lost each year due to fungal attack. Wood-rotting fungi destroy not only living trees but also structural timber.

Saprobic fungi are not only useful recyclers but also cause incalculable damage to food, wood, fiber, and leather by decomposing them.

Bracket/shelf fungi cause lot of damage to stored cut lumber as well as stands of timber of living trees.

A pink yeast (Rhodotorula) grows on shower curtains and other moist surfaces.

Fungi Pics.

LICHEN

Fungi form two key mutualistic symbiotic between

certain fungi (mostly Ascomycetes and imperfect fungi, and few basidiomycetes – about 20 out of 15000 species of lichens) and

certain photoautotrophs – either green algae or a cyanobacterium, or sometimes both.

Most of the visible part of lichen consists of fungus, and algal components are present within the hyphae.

Fungus protects the algal partner from strong light and desiccation and itself gets food through the courtesy of alga.

ECOLOGICAL IMPORTANCE .

Succession.

Lichens can grow at such places where neither of the components alone can grow, even at harsh places such as bare rocks etc. Lichens growing on rocks break them, setting stage for other organisms during the course of ecological succession

Bio indicators.

They are ecologically very important as bioindicators of air pollution.

REPRODUCTION.

Lichen are sometimes asexually reproduced by soredia. Soredia are fragments separated from lichen body and contain group of algal cells enveloped by fungal hyphae.

STRUCTURE.

Surface and bottom layers of lichen body usually contain hyphae of fungi While

Portion of lichen body below the surface layer contains both hyphae and photoautotrophs strongly interwoven into each other while portion above the bottom layer contain loosely interwoven components.

TYPES OF LICHEN.

Different types of lichens varying in size, colour and appearance.

Three growth forms.

Crustose

grow tightly attached to rocks, tree trunks etc.; e.g. Bacidia, Lecanor

Foliose are leaf – like. e.g. Parmelia.

Fruticose are branching. Ramalina

@@ Tanveer Mix Biology Notes For MBBS And Lecturer Students

REPRODUCTION IN FUNGI

Most fungi can reproduce asexually as well as sexually (except imperfect fungi in which s****l reproduction has not been observed).

ASEXUAL REPRODUCTION

Asexual reproduction takes place by spores, conidia, fragmentation, and budding.

SPORES FORMATION.

Spores are produced inside the reproductive structures called sporangia, which are cut off from the hyphae by complete septa. Spores may be produced by s****l or asexual process.

GENEARL CHARACTERISTICS OF SPORES.

These are haploid, non-motile small, and produced in very large number and

Dispersal.

. These do not need water for their dispersal, and dispersed by wind to great distances and cause wide distribution of many kinds of fungi, including many plant pathogens. Spores may also be dispersed by insects and other small animals and by rain splashes.

Germination.

When spores land in a suitable place, they germinate, giving rise to new fungal hyphae. Spores are a common means of reproduction in fungi.

Conidia Formation

Conidia (singular conidium) are non-motile, asexual spores which are cut off at the end of modified hyphae called conidiophores, and not inside the sporangia, usually in chains or clusters.

These may be produced in a very large number, can survive for weeks and cause rapid colonization of new food.

LASSIFICATION OF FUNGI

Classification of fungi into four main groups.

GENES

Gene is the basic unit of biological information. Hereditary characteristics pass from parents to offspring through genes in their gametes. In fact DNA stores all sorts of biological information coded in the sequence of its bases in a linear order, and genes are actually parts of DNA comprising its base sequences.

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