Category: Biology Second Paper

1. Bacteria are microscopic, smallest (0.2-5.0 micrometers) and simplest organisms.
2. They are unicellular organisms. But can form groups or colonies together.
3. They are primitive creatures. That is, their nucleus does not have nuclear membrane and nucleolus.
4. Their cells contain no other organelles except ribosomes (70S). That is, bacteria do not have chloroplasts, mitochondria, endoplasmic reticulum, Golgibodies, lysosomes, cytoskeleton, microbodies etc.
5. They can be parasitic, saprophytic or autophytic.
6. Their cell wall is composed of mucopeptide, peptidoglycan, polysaccharide, teichoic acid and muramic acid. They are similar to plants because they have cell walls.
7. Their cell membrane or plasma membrane folds to form mesosomes.
8. They are very sensitive to phage virus.
9. They collect energy by oxidizing inorganic salts.
10. They can survive extremely cold temperatures ranging from -170C to 800C.
11. Cells of autophytic bacteria contain bacteriochlorophyll, bacterioviridin, bacterium chlorophyll and carotene as photosynthetic pigments.
12. As their cells do not have chromosomes, mitosis and meiosis cell division does not occur.
13. They reproduce by binary fission, asexually, asexually and sexually.
14. It can carry out respiration in the presence or absence of oxygen.
15. Some bacteria are obligate aerobic, some bacteria are obligate anaerobes and some bacteria are opportunistic anaerobes.
16. Bacterial cells have flagella. It is composed of flagellin protein.
17. Bacteria have pili or phimoxy. It is composed of pilin protein.
18. Its cell membrane does not contain cholesterol or steroids.
19. Forms endospores to survive in hostile environment. In this condition it can last up to 50 years.
20. They can usually have a basic color (gram positive or negative).

1. Bacteria live as parasites in plants and animals. Lives as a mitotic organism in the intestines of animals. Bacteria living in human body are – Salmonella typhosa, Mycobacterium tuberculosis, Bacillus anthracis, Diplococcus pneumoniae, Clostridium tetani etc.
2. There are about 40 million bacteria in one gram of soil and about 1 million in one milliliter of fresh water. Bacteria living in soil are Rhizobium, Azotobacter, Bacillus, Clostridium, Nitrosococcus, Nitrosomonas etc.
3. There are 10 times more bacteria than there are cells in the human body. 500 species of bacteria live in the human mouth.
4. There are about five billion bacteria on Earth. The total biomass of bacteria is greater than that of all plants and animals.
5. Bacteria survive in extreme cold (-17°C) and extreme heat (100°C). Bacteria can live in the presence or absence of oxygen.
6. Human cholera (Vibrio cholerae), dysentery (Bacillus dysenteti), tuberculosis (Mycobacterium tuberculosis), typhoid (Salmonella typhosa), whooping cough (Bordetallapertussus), pneumonia (Diplococcus pneumoniae), diphtheria (Corynebacterium diptheriae), syphilis (Treponema pallidum), gonorrhea ( Neisseria gonorrhoeae), meningitis (Neisseria meningitidis), plague (Yersinia pestis), tetanus (Clostridium tetani), leprosy (Mycobacterium leprae) etc. are caused by bacteria.
7. Diseases like Mycobacterium bovis and undulated fever, sheep anthrax (Bacillus anthracis), goat brucellosis (Brucella sui), rat plague (Yersinia pestis), poultry cholera (Bacillus avisepticus) etc. are caused by bacteria.
8. Wheat blight (Agrobacterium tritici), rice blight (Xanthomonas oryzae), sugarcane blight (Xanthomonas vasculorum), tomato canker (Corynebacterium michiganese), tomato and rose crown gall (Agrobacterium tumefaciens), lemon canker (Xanthomonas citri), potato Scab disease (Steptomyces scabies), apple fire blight (Erwinia amylovora), oat root rot and potato soft rot (Erwinia carotovora), tobacco blight (Pseudomonas tabacci), cotton leaf spot (Xanthomonas mavacearum), bean leaf spot (Xanthomonas malvacearum) ) etc. diseases are caused by bacteria.

There are about five billion bacteria on Earth. There are about 40 million bacteria in one gram of soil and about 1 million in one milliliter of fresh water. A total of 472 species of bacteria have been recorded from Bangladesh in Encyclopedia of Flora and Fauna of Bangladesh. Among them, 300 species of Cyanobacteria, 60 species of Proteobacteria, 42 species of Firmicutes and 70 species of Actinobacteria.

Bacteria are about 0.2-50 micrometers in size. Bacillus bacteria are 5×0.4-0.7 micrometers, Pseudomonas bacteria are 0.4-0.7 micrometers, and Micrococcus bacteria are about 0.6 micrometers. The smallest bacteria is Dialister pneumosintes. It causes disease in human respiratory tract. The largest bacteria is Epulopiscium fishelsoni. It lives as a parasite in the gut of a type of marine fish. Currently, Mycoplasma is considered as a bacteria.

In 1675 Dutch scientist Antony Von Leeuwenhoek observed bacteria and named them animalcule. In 1773, the Danish scientist Müller named the rod-shaped organisms as bacilli. In 1829, German scientist C. G. Ehrenberg was the first to name the small organisms bacteria. In 1869, the French scientist Louis Pasteur established the Germ theory of disease by extensive research on bacteria. In 1878, German physician and scientist Sadilot named bacteria as microbes. In 1952, Zinder and Linderberg discovered the bacterial transduction system. In 1968, scientist Mary included bacteria as prokaryotes. German physician Robert Koch is called the father of bacteriology.

The Greek word bakterion means stick or rod. Bacteria are the simplest microscopic organisms in nature that are single-celled without chlorophyll and have complex cell walls that cause disease in plants and animals. Bacteria are called natural scavengers. The branch of biology which deals with the structure, habitat, pathology, reproduction etc. of bacteria is called bacteriology. Anthony van Leeuwen Hooke is called the father of bacteriology and protozoology.

No cure for AIDS has been discovered till date. Treatment of AIDS with drugs is called anti-retroviral therapy or ART. In the treatment of AIDS, the Food and Drug Administration-FDA (USA) recommends taking two groups of drugs together. This type of treatment is known as Highly Active Antiretroviral Therapy-HAART. The first group of drugs are Nucleoside reverse transcriptase inhibitors which delay its transmission. The second group of drugs is Protease inhibitors which block the replication of HIV. Some of the approved drugs are Fusion Inhibitors, Entry Inhibitors, Integrase Inhibitors, Pharmacokinetic Enhancers etc.

(i) To follow social and religious norms.
(ii) Associate with a trusted partner.
(iii) Condom should be used during intercourse.
(iv) Avoid taking intravenous drugs.
(v) The same syringe should not be used repeatedly.
(vi) Blood should be tested for virus free before collection.
(vii) Not using the same blade more than once in the salon.
(viii) Treat the diseased person.
(ix) Sex workers should be made aware of safe sex.
(x) People should be made aware.

Antibody Test, Western Blot Test etc. Blood T-helper cells or CD-4 cells are tested. (The normal range of CD-4 cells is 500-1,500 cells/mm3).

(i) Fever, headache and fatigue.
(ii) There is dry phlegm. Pneumonia occurs and wheezing occurs.
(iii) Lymph nodes become swollen and become lymphoma cancer.
(iv) Abdominal pain and loss of appetite.
(v) Arthritis causes severe pain and burning.
(vi) Karposi sarcoma cancer (brown spot) occurs on skin and face.
(vii) Troxoplasmosis occurs in brain and thinking power is reduced. Memory and vision decline.
(viii) Limbs are deformed. Body weight decreases. The body becomes weak.
(ix) Immunity is lost and the patient dies.