Bacteria that look like stars are called star-shaped bacteria. Such as- Stella humosa, Stella vacuolata.

Square bacteria with four arms are called square bacteria. For example, Haloquadratum.

Bacteria that do not have a specific shape are called pleomorphic bacteria. For example, Rhizobium mayense.

Archaic bacteria are called archaic bacteria. For example – Vibrio cholera.

Bacteria that look rod-shaped are called bacillus. Different types of bacillus are-
(i) Monobacillus : Rod shaped bacteria are called monobacillus if they are single. For example- Bacillus albus, Escherichia coli.
(ii) Diplobacillus : When rod-shaped bacteria are arranged in pairs, they are called Diplobacillus. Lactobacillus, Corynebacterium diptheriae, Moraxella lacunata, Diplobacillus.
(iii) Streptobacillus: Rod-shaped bacteria are called Streptobacillus if they are arranged in chains. For example- Bacillus tuberculosis, Streptobacillus moniliformis.
(iv) Palisadebacillus : If the rod-shaped bacteria are parallel to each other and form a structure like oleic tissue, it is called palisade bacillus. For example, Lampropedia sp.
(v) Coccobacillus: If the bacteria are elongated or ovoid, they are called coccobacillus. For example – Salmonella, Mycobacterium, Coxiella burnetti.
3. Spirillum: Viruses that have a squiggly or coiled appearance are called Spirillum bacteria. For example, Spirillum minus, Treponema.

Bacteria that are round in appearance are called coccus bacteria. Different types of coccus bacteria are-
(i) Micrococcus : Spherical bacteria are called Micrococcus if they are isolated or isolated. For example, Micrococcus denitrificans, Micrococcus aureus, Micrococcus flavus.
(ii) Diplococcus : Spherical bacteria in pairs or pairs are called diplococcus. For example, Diplococcus pneumonia.
(iii) Streptococcus Streptococcus: Spherical bacteria are called Streptococcus if they are arranged in chains. For example, Treptococcus lactis, Treptococcus strep and Treptococcus pyrogens.
(iv) Tetracoccus : Spherical bacterial cells divided into two different layers and arranged in groups of four are called tetracoccus. Such as Gaffkyacoccus tetragena, Tetracoccus sp.
(v) Staphylococcus : Spherical bacteria clustered together like bunches of grapes are called Staphylococcus. For example, Staphylococcus aureus.
(vi) Sarcina : A certain number of spherical bacterial cells arranged regularly is called Sarcina. For example – Sarcina lutea.

1. Coccus
Bacteria that are round in appearance are called coccus bacteria. Different types of coccus bacteria are-
(i) Micrococcus : Spherical bacteria are called Micrococcus if they are isolated or isolated. For example, Micrococcus denitrificans, Micrococcus aureus, Micrococcus flavus.
(ii) Diplococcus : Spherical bacteria in pairs or pairs are called diplococcus. For example, Diplococcus pneumonia.
(iii) Streptococcus Streptococcus: Spherical bacteria are called Streptococcus if they are arranged in chains. For example, Treptococcus lactis, Treptococcus strep and Treptococcus pyrogens.
(iv) Tetracoccus : Spherical bacterial cells divided into two different layers and arranged in groups of four are called tetracoccus. Such as Gaffkyacoccus tetragena, Tetracoccus sp.
(v) Staphylococcus : Spherical bacteria clustered together like bunches of grapes are called Staphylococcus. For example, Staphylococcus aureus.
(vi) Sarcina : A certain number of spherical bacterial cells arranged regularly is called Sarcina. For example – Sarcina lutea.
2. Bacillus
Bacteria that look rod-shaped are called bacillus. Different types of bacillus are-
(i) Monobacillus : Rod shaped bacteria are called monobacillus if they are single. For example- Bacillus albus, Escherichia coli.
(ii) Diplobacillus : When rod-shaped bacteria are arranged in pairs, they are called Diplobacillus. Lactobacillus, Corynebacterium diptheriae, Moraxella lacunata, Diplobacillus.
(iii) Streptobacillus: Rod-shaped bacteria are called Streptobacillus if they are arranged in chains. For example- Bacillus tuberculosis, Streptobacillus moniliformis.
(iv) Palisadebacillus : If the rod-shaped bacteria are parallel to each other and form a structure like oleic tissue, it is called palisade bacillus. For example, Lampropedia sp.
(v) Coccobacillus: If the bacteria are elongated or ovoid, they are called coccobacillus. For example – Salmonella, Mycobacterium, Coxiella burnetti.
3. Spirillum: Viruses that have a squiggly or coiled appearance are called Spirillum bacteria. For example, Spirillum minus, Treponema.
4. Archaic bacteria: Archaic bacteria are called archaic bacteria. For example – Vibrio cholera.
5. Pleomorphic: Bacteria that do not have a specific shape are called pleomorphic bacteria. For example, Rhizobium mayense.
6. Square shaped bacteria: Square bacteria with four arms are called square bacteria. For example, Haloquadratum.
7. Star-shaped bacteria: Bacteria that look like stars are called star-shaped bacteria. Such as- Stella humosa, Stella vacuolata.
8. Hyphae or Microscopic Bacteria: Bacteria that are long hyphae with thin walls are called microscopic bacteria. Such as Candidatus savagella, Streptomyces.

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.