Viruses are very tiny, simple organisms. In fact, they are so tiny that they can only be seen with a special, very powerful microscope called an "electron microscope," and they are so simple that they are technically not even considered "alive."
Structure of Virus
Each virus is made up of two elementary components. The first is a strand of genetic material, either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). Unlike living cells, viruses will have either DNA or RNA, but not both. The genetic material is a blueprint for determining the structure and behavior of a cell. In a virus, a protein coat called a "capsid" surrounds the nucleic acid. This coat serves to protect the nucleic acid and aid in its transmission between host cells. The capsid is made of many small protein particles called "capsomeres," and can be formed in three general shapes – helical, icosahedral (a 20-sided figure with equilateral triangles on each side), and complex. Some of the more advanced viruses have a third structure that surrounds the capsid. This is called the "envelope" and is composed of a bilipid layer, like the membrane on a cell, and glycoproteins, which are protein and carbohydrate compounds. The envelope serves to disguise the virus to look like a 'real' cell, protecting it from appearing as a foreign substance to the immune system of the host. The structure of a virus is closely related to its mode of reproduction.
Human diseases caused by Virus
| Disease | Name of Virus |
| AIDS (Acquired immune deficiency syndrome | Human T cell Leukemia Virus (HTLV III) |
| Chicken Pox | Varicella Virus |
| Common Cold | Rhino Virus |
| Herpes Zoster | Herpes Zoster |
| Influenza/ Flu | Orthomixo Virus |
| Measles | Paramyxo Virus |
| Mumps | Mumps Virus |
| Rabies | Rhabdovirus |
| Dengue Fever | Arbovirus |
| Poliomyelitis | poliovirus |
| Herpes Simplex | Herpes Simplex |
Treatement
Although viruses cannot be treated with antibiotics, which are effective only against bacteria, the body's immune system has many natural defences against virus infections. Infected cells produce interferon and other cytokines (soluble components that are largely responsible for regulating the immune response), which can signal adjacent uninfected cells to mount their defences, enabling uninfected cells to impair virus replication. Virus are widely used in genetic engineering. Viruses that are parasites of bacteria are called bacteriophage.
Viroids and Prions
Viroids and prions are smaller than viruses, but they are similarly associated with disease.
Viroids are plant pathogens that consist only of a circular, independently replicating RNA molecule.
Prion The mutated protein, known as a prion, has been implicated in some neurological diseases such as Creutzfeldt-Jakob disease and Bovine Spongiform Encephalopathy. There is some evidence that prions resemble viruses in their ability to cause infection. Prions, however, lack the nucleic acid found in viruses.
Structure
Bacteria are microorganisms that lack a nucleus and have a cell wall composed of peptidoglycan, a protein-sugar molecule. Bacteria are the most common organisms on earth and are intimately connected to the lives of all organisms. The common structural forms are
- Spherical or ovoid (coccus )
- rod shaped or cylindrical (bacillus )
- spiral or screw (spirillum)
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Many forms of bacteria are not capable of independent movement,. Some Bacteria which live in liquid often have thread like projections called flagella (e.g Salmonella bacterium)
Reproduction
Reproduction in bacteria is largely by binary fission i.e. it splits into two. In some case due to some extreme environmental conditions, they form tiny structures is called Spores. It is formed by condensation of protoplasm into a spherical or egg shaped body and they germinate under favourable conditions. Some bacteria exhibit a type of sexual reproduction.
Human Diseases caused by bacteria
| Disease | Name of Bacteria | Mode of Transmission |
| Septic sore throat | Streptococccus | By direct contact & droplets |
| Diptheria | Corynebacterim diptheriae | Infect respiratory tract by carrier, direct contact, droplets and food |
| Pneumonia | Diplococcus pneumoniae | respiratory tract,lungs by direct contact, droplets and food. |
| Tuberculosis | Mycobacterium | Lungs, bones etc by direct contact |
| Plague or Babonic Plague | Yersinia pestis | Rat flea spreads from rat to man |
| Tetanus | Clostridium tetani | Bacteria in soil, enter through wounds |
| Typhoid | Samonella typhi | Flies, food, faeces, water and carriers |
| Typhoid | Samonella typhi | Flies, food, faeces, water and carriers |
| Cholera | Vibrio Cholerae | Flies, food, faeces, water and carriers |
| Bacillary dysentery | Shigella dysenteriae | Flies, food, faeces, water and carriers |
| Whooping Cough | Hemophilus pertussis | Droplets |
| Gonorrhoea | Neisseria gomorrhoeae | Sexual intercourse |
| Syphilis | Treponema Pallidum | Sexual intercourse |
| Leprosy | Mycobacterium leprae | Sexual intercourse |
| Leprosy | Mycobacterium leprae | Long and close contact with infected |
| Botulism | Clostridium botulinum | Organism produces poison in food |
Treatement
Vaccination or Immunization or inoculation is a method of stimulating resistance in the human body to specific diseases using microorganisms -bacteria or viruses-that have been modified or killed. These vaccines do not cause diseases but stimulates the production of antibodies in its blood. It build a defense mechanism that continuously guards against the disease. If a person immunized against a particular disease later comes into contact with the disease-causing agent, the immune system is immediately able to respond defensively. Bacterial vaccines are used chiefly in immunizing human beings and animals against such diseases on diphtheria, cholera and typhoid fever.
Uses
Aerobic bacteria uses oxygen for respiration and anaerobic bacteria maintain respiration without free oxygen and this process is known as fermentation. So it is used in the production of vinegar and other substances. Some bacteria decompose organic matter and fix nitrogen by converting atmospheric nitrogen into nitrates. These are mainly found in the roots of legumes such as peas, clover and alfalfa. In human beings, intestinal bacteria produce lactic acid which promotes digestion.
Bioremediation
It is the use of microorganisms such as bacteria to remove environmental pollutants from soil, water or gases.
Serum
Serum is a preparation from blood of an animal that has been inoculated with bacteria. This contains antibodies that formed as a consequence of the disease. The important antibodies produced with the help of bacteria are streptomycin, Aureomycin, Terramycin. Please note that penicillin is produced by an Fungi.
History
- Antoni van Leeuwenhoek : The first person to systematically study bacteria.
- Louis Pasteur: Showed that microbes do not arise from nonliving matter (germ theory). He also founded the science of microbiology, invented the process of pasteurization, and developed vaccines for several diseases, including rabies.
- Robert Koch: showed that bacteria could cause disease.
The fungi (singular fungus) are a kingdom of eukaryotic organisms. Fungi lack chlorophyll; consequently they cannot synthesize their own food. In order to feed fungi release digestive enzymes that break down food outside their bodies. The fungus then absorbs the dissolved food through their cell walls. It is a simple plant body that has no roots, stems, flowers and seeds. It includes mushrooms, molds, yeasts, truffles etc.
Mycology
The branch of biology involving the study of fungi is known as mycology.
Types of Fungi
The major divisions (phyla) of fungi are mainly classified based on their sexual reproductive structures. Currently, five divisions are recognized:
- The Chytridiomycota are commonly known as chytrids. These fungi produce zoospores that are capable of moving on their own through liquid menstrua by simple flagella.
- The Zygomycota are known as zygomycetes and reproduce sexually with meiospores called zygospores and asexually with sporangiospores. Black bread mold (Rhizopus stolonifer) is a common species that belongs to this group; another is Pilobolus, which shoots specialized structures through the air for several meters. Medically relevant genera include Mucor, Rhizomucor, and Rhizopus. Molecular phylogenetic investigation has shown the zygomycota to be a polyphyletic group.
- Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually. This is an ancient association, with evidence dating to 350 million years ago.
- The Ascomycota, commonly known as sac fungi or ascomycetes, form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes morels, some mushrooms and truffles, as well as single-celled yeasts and many species that have only been observed undergoing asexual reproduction. Because the products of meiosis are retained within the sac-like ascus, several ascomyctes have been used for elucidating principles of genetics and heredity (e.g. Neurospora crassa).
- Members of the Basidiomycota, commonly known as the club fungi or basidiomycetes, produce meiospores called basidiospores on club-like stalks called basidia. Most common mushrooms belong to this group, as well as rust (fungus) and smut fungi, which are major pathogens of grains.
Major Uses
- The enzyme forming activities are used by man in brewing, baking, cheese making. Some cause diseases in animals and plants.
- The symbiotic relationship between fungus and roots are called mycorrhizal. Similarly Lichens are living partnership of a fungus and an alga.
- Litmus, a dye used in chemistry to determine the presence of acid and bases in a solution. Acid turn blue litmus red and bases turn red litmus blue.
- Fungi and bacteria are the primary decomposers of organic matter in most terrestrial ecosystems
- Some of these fungi can be used as biopesticides, like the ones that kill insects (entomopathogenic fungi). Specific examples of fungi that have been developed as bioinsecticides are Beauveria bassiana, Metarhizium anisopliae, Hirsutella, Paecilomyces fumosoroseus, and Verticillium lecanii.
Major diseases in human caused by Fungi
- Ringworm
- Athletes foot
- Madura foot
- Dhobie itch
These are chiefly plant like organisms found usually in water bodies and moist environments that are not subjected to direct sunlight. They make their own food by photosynthesis but theylack roots, leaves and other structures typical of true plants. They capture more of sun’s energy than all plants combined and form the foundation of most aquatic food webs. These are divided into 7 divisions one belonging to monera and the rest to plant kingdom.
Blue Green Algae (Cyanobacteria)
This belongs to the moneran division and contain a blue pigmentphycocyanin ,which in addition to chlorophyll but the chlorophyll is not located in chloroplasts rather it is found in chromatophores, infoldings of the plasma memrane where photosynthesis is carried out. It fixes atmospheric nitrogen. Some of this group likeGloeocapsa and Nostoc coexist with fungi to form Lichens. They give reddish colour to the Red sea. Euglenophycota is like Euglena found in stagnant water causes greenish colour and unpleasant flavour. Extensive quantities not desirable for drinking.
Green Algae (chlorophyta)
These are found in fresh water and add more oxygen to water. Their excessive growth contaminate water . This unwanted growth can be removed by adding copper sulphate (CuSo4). Chlamydomonasis a green alage found in ditches,pools and even in artic . Spirogyrais green alage with a unique arrangement of its chlorophyll like a spirally twisted ribbon.
Brown Algae
The Brown colour is due to the presence of brown pigment,Flucoxanthin. They are the important sources of food for fish and other marine animals. They are also used as cattle feed, fertilizer. Its well known forms include Kelp (largest algae) and the sargassum weed.
Red Algae
These are characterized by reddish pigment phycobilin pigments . Most species grow near tropical and subtropical shores below the low tide mark and quite few are found on fresh water. Some secrete lime and there fore helped to build numours coral reefs . important edible varieties are Irish moss and laver(porphyra). Iris moss is used in curing leather, shoe polish and as an ingredient for creams and shampoos. Ceylon moss yield a gelatinous material known asagar-agar which is used as a medium for growing bacteria and fungi. Carrageenin obtained from Irish moss used as substitute for gelatine.
Diatoms
They have colour ranging from yellowish green to yellowish brown containing silica. When they die, their skeletons are accumulated on the bottom of earth. This diatomaceous earth is used as insulating material for boilers, blast furnaces and refrigerators. It is also used as mild abrasive in polishes and scouring powders.
