Microbiology is the study of microorganisms like bacteria, fungi and viruses. There are several branches of microbiology including bacteriology, mycology, virology and parasitology. Bacteriology is the study of bacteria and their characteristics such as their cell structure, genetics and role in causing disease. Bacteria can be classified based on their shape, cell wall composition, mode of nutrition and respiration. They reproduce through binary fission. Mycology is the study of fungi which have cell walls made of chitin. Fungi are classified based on their sexual reproduction and morphology. They can reproduce sexually through spores or asexually through budding or hyphal growth. Viro

1. MICROBIOLOGY –
BRANCHES

2. What is microbiology ?
 Microbiology is the scientific study of microorganisms, those
being unicellular (single cell), multicellular (cell colony), or acellular (lacking
cells).
 Microbiology is the study of a variety of living organisms which are invisible
to the naked eye like bacteria and fungi and many other microscopic
organisms.
 Although tiny in size these organisms form the basis for all life on earth.
 These microbes as they are also known to produce the soil in which plants
grow and the fix atmospheric gases that both plants animals use.
 About 3 billion years ago at the time of formation of the earth, microbes
were the only lives on earth.
 Microorganisms have played a key role in the evolution of the planet earth.

3. Branches of microbiology
There are various different branches in microbiology and these include the following:
1. Bacteriology- The study of bacteria
2. Mycology –The study of fungi
3. Phycology- The study of photosynthetic eukaryotes. (Algae- Seaweed)
4. Protozoology – The study of protozoa (Single-celled eukaryotes)
5. Virology- The study of viruses, non-cellular particles which parasitize cells.
6. Parasitology- The study of parasites which include pathogenic protozoa certain insects and helminth
worms.
7. Nematology- The study of nematodes.

4. BACTERIOLOGY

5. What is bacteriology ?
 Bacteriology is a branch of microbiology that is concerned with the study of bacteria
(as well as Archaea) and related aspects.
 It's a field in which bacteriologists study and learn more about the various
characteristics (structure, genetics, biochemistry and ecology etc) of bacteria as well
as the mechanism through which they cause diseases in humans and animals.
 One of the very first organisms to evolve on earth was probably a unicellular
organism, similar to modern bacteria.
 Ever since then, life has evolved into a multitude of life forms over many millennia.
 However, we can still trace our ancestry back to this single-celled organism.
 Today, bacteria are considered as one of the oldest forms of life on earth.
 Even though most bacteria make us ill, they have a long-term, mutual relationship with
humans and are very much important for our survival.

6. BACTERIA - STRUCTURE

7. Structure of Bacteria
The structure of bacteria is known for its simple body design. Bacteria are single-celled microorganisms
with the absence of the nucleus and other cell organelles; hence, they are classified as prokaryotic
organisms.
They are also very versatile organisms, surviving in extremely inhospitable conditions. Such organisms are
called extremophiles. Extremophiles are further categorized into various types based on the types of
environments they inhabit:
1. Thermophiles
2. Acidophiles
3. Alkaliphiles
4. Osmophiles
5. Barophiles
6. Cryophiles

8.  Another fascinating feature of bacteria is their protective cell wall, which is made
up of a special protein called peptidoglycan.
 This particular protein isn’t found anywhere else in nature except in the cell walls
of bacteria.
 But few of them are devoid of this cell wall, and others have a third protection
layer called capsule.
 On the outer layer, one or more flagella or pili is attached, and it functions as a
locomotory organ.
 Pili can also help certain bacteria to attach themselves to the host’s cells. They do
not contain any cell organelle as in animal or plant cell except for ribosomes.
 Ribosomes are the sites of protein synthesis.
 In addition to this DNA, they have an extra circular DNA called plasmid. These
plasmids make some strains of bacteria resistant to antibiotics.

9. Classification of Bacteria
Bacteria can be classified into various categories based on their features and characteristics. The
classification of bacteria is mainly based on the following:
• Shape
• Composition of the cell wall
• Mode of respiration
• Mode of nutrition
Type of Classification Examples
1. Based on shape

10. Type of Classification Examples
Peptidoglycan cell wall Gram-positive bacteria
Lipopolysaccharide cell wall Gram-negative bacteria
2. Based on composition of cell wall
Type of Classification Examples
Autotrophic Bacteria Cyanobacteria
Heterotrophic Bacteria All disease-causing bacteria
3. Based on mode of nutrition
Type of Classification Examples
Anaerobic Bacteria Actinomyces
Aerobic Bacteria Mycobacterium
4. Based on mode of respiration

11. Reproduction of bacteria
 Bacteria follow an asexual mode of reproduction, called binary fission.
 A single bacterium divides into two daughter cells.
 These are identical to the parent cell as well as to each other.
 Replication of DNA within parent bacterium marks the beginning of the fission.
 Eventually, cell elongates to form two daughter cells.
 The rate and timing of reproduction depend upon the conditions like temperature and availability of
nutrients.
 When there is a favourable condition, E.coli or Escherichia coli produces about 2 million bacteria every 7
hours.
 Bacterial reproduction is strictly asexual, but it can undergo sexual reproduction in very rare cases.
 Genetic recombination in bacteria has the potential to occur through conjugation, transformation, or
transduction.
 In such cases, the bacteria may become resistant to antibiotics since there is variation in the genetic
material (as opposed to asexual reproduction where the same genetic material is present in generations)

12. BACTERIA – REPRODUCTION

13. Useful Bacteria
 Not all bacteria are harmful to humans.
 There are some bacteria which are beneficial in different ways.
Listed below are few benefits of bacteria:
1. Convert milk into curd – Lactobacillus or lactic acid bacteria
2. Ferment food products – Streptococcus and Bacillus
3. Help in digestion and improving the body’s immunity system –
Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria
4. Production of antibiotics, which is used in the treatment and
prevention of bacterial infections – Soil bacteria

14. Harmful Bacteria
 There are bacteria that can cause a multitude of illnesses.
 They are responsible for many of the infectious diseases like
pneumonia, tuberculosis, diphtheria, syphilis, tooth decay.
 Their effects can be rectified by taking antibiotics and prescribed
medication.
 However, precaution is much more effective.
 Most of these disease-causing bacteria can be eliminated
by sterilizing or disinfecting exposed surfaces, instruments, tools
and other utilities.
 These methods include- application of heat, disinfectants, UV
radiations, pasteurization, boiling, etc.

15. MYCOLOGY

16. What is mycology ?
 The term "mycology" is derived from Greek word "mykes" meaning
mushroom.
 Therefore mycology is the study of fungi.
 The ability of fungi to invade plant and animal tissue was observed in early
19th century but the first documented animal infection by any fungus was
made by Bassi, who in 1835 studied the muscardine disease of silkworm
and proved the that the infection was caused by a fungus Beauveria
bassiana.
 In 1910 Raymond Sabouraud published his book Les Teignes, which was a
comprehensive study of dermatophytic fungi.
 He is also regarded as father of medical mycology.
Importance of fungi
 Fungi inhabit almost every niche in the environment and humans are
exposed to these organisms in various fields of life.

17. General properties of fungi
1. They are eukaryotic; cells contain membrane bound cell organelles including nuclei, mitochondria,
golgi apparatus, endoplasmic reticulum, lysosomes etc. They also exhibit mitosis.
2. Have ergosterols in their membranes and possesses 80S ribosomes.
3. Have a rigid cell wall and are therefore non-motile, a feature that separates them from animals.
All fungi possess cell wall made of chitin.
4. Are chemoheterotrophs (require organic compounds for both carbon and energy sources) and
fungi lack chlorophyll and are therefore not autotrophic.
5. Fungi are osmiotrophic; they obtain their nutrients by absorption.
6. They obtain nutrients as saprophytes (live off of decaying matter) or as parasites (live off of
living matter).
7. All fungi require water and oxygen and there are no obligate anaerobes.
8. Typically reproduce asexually and/or sexually by producing spores.
9. They grow either reproductively by budding or non-reproductively by hyphal tip elongation.
10. Food storage is generally in the form of lipids and glycogen.

18. CLASSIFICATION OF FUNGI
Based on Sexual reproduction:
1. Zygomycetes: which produce through production
of zygospores.
2. Ascomycetes: which produce endogenous spores
called ascospores in cells called asci.
3. Basidiomycetes: which produce exogenous spores
called basidiospores in cells called basidia.
4. Deuteromycetes (Fungi imperfecti): fungi that
are not known to produce any sexual spores
(ascospores or basidiospores). This is a
heterogeneous group of fungi where no sexual
reproduction has yet been demonstrated.
Zygomycetes Ascomycetes
Basidiomycetes Deutromycetes

19. Based on Morphology:
1. Moulds (Molds): Filamentous fungi Eg: Aspergillus
sps, Trichophyton rubrum
2. Yeasts: Single celled cells that buds Eg:
Cryptococcus neoformans, Saccharomyces
cerviciae
3. Yeast like: Similar to yeasts but produce
pseudohyphae Eg: Candida albicans
4. Dimorphic: Fungi existing in two different
morphological forms at two different
environmental conditions. They exist as yeasts in
tissue and in vitro at 37o C and as moulds in their
natural habitat and in vitro at room temperature.
Eg: Histoplasma capsulatum, Blastomyces
dermatidis, Paracoccidiodes brasiliensis,
Coccidioides immitis
Moulds Yeasts
Yeast like fungi Dimorphic fungi

20. Morphology of fungi
 All fungi have typical eukaryotic morphology.
 They have rigid cell wall composed of chitin, which may be layered with mannans, glucans and other
polysaccharides in association with polypeptides.
 Some lower fungi possess cellulose in their cell wall.
 Some fungi such as Cryptococcus and yeast form of Histoplasma capsulatum possess
polysaccharide capsules that help them to evade phagocytosis.
 Inner to the cell wall is the plasma membrane that is a typical bi-layered membrane in addition to
the presence of sterols.
 Fungal membranes possess ergosterol in contrast to cholesterol found in mammalian cells.
 The cytoplasm consists of various organelles such as mitochondria, golgi apparatus, ribosomes,
endoplasmic reticulum, lysosomes, microtubules and a membrane enclosed nucleus.
 A unique property of nuclear membrane is that it persists throughout the metaphase of mitosis
unlike in plant and animal cells where it dissolves and re-forms.
 The nucleus possesses paired chromosomes.

22. Reproduction in fungi
 Fungi reproduce by
 Asexual reproduction is the commonest mode in most fungi with fungi participating
in sexual mode only under certain circumstances.
 The form of fungus undergoing asexual reproduction is known as anamorph (or
imperfect stage) and when the same fungus is undergoing sexual reproduction, the
form is said to be teleomorph (or perfect stage).
 The whole fungus, including both the forms is referred as holomorph.
(Taxonomically, the teleomorph or the holomorph is used, but practically it is more
convenient to use the anamorph.)
1. Asexual
2. Sexual
3. Parasexual

23. ASEXUAL REPRODUCTION

24. PARASEXUAL REPRODUCTION

25. Importance of Spores
A. Biological
1) Allows for dissemination
2) Allows for reproduction
3) Allows the fungus to move to new food source.
4) Allows fungus to survive periods of adversity.
5) Means of introducing new genetic combinations into a population
B. Practical
1) Rapid identification (also helps with classification)
2) Source of inocula for human infection
3) Source of inocula for contamination

26. FUNGAL DISEASES (MYCOSES) Mycoses can be conveniently studied as:
1. Superficial mycoses
I. Superficial phaeohyphomycosis
II. Tinea versicolor
III. Black piedra
IV. White piedra
2. Cutaneous mycoses
I. Dermatophytosis
II. Dermatomycosis
3. Subcutaneous mycoses
I. Chromoblastomycosis
II. Rhinosporidiasis
III. Mycetoma
IV. Sporotrichosis
V. Subcutaneous phaeohyphomycosis
VI. Lobomycosis
4. Systemic (deep) mycoses
I. Blastomycosis
II. Histoplasmosis
III. Coccidioidomycosis
IV. Paracoccidioidomycosis
5. Opportunistic mycoses
I. Candidiasis
II. Cryptococcosis
III. Aspergillosis
6. Other mycoses
I. Otomycosis
II. Occulomycosis
7. Fungal allergies
8. Mycetism and mycotoxicosis

27. VIROLOGY

28. What is Virology?
 Virology is the branch of microbiology which mainly deals with a study of various
types of viruses, including their characteristics, agents, submicroscopic, parasitic,
viral diseases and particle of genetic material that are present in the protein coat.
 Virology is a stream of science that mainly focuses on aspects such as their
immunity, the ability to destroy or infect the host cells, their evolution,
classification, structure, composition, several ways of infecting, different ways of
culturing them, their use in laboratory, various methods to isolate them and their
physiology.
Viruses
 Viruses are non-cellular microscopic organisms, which are composed of genetic
material and protein that can invade living cells.
 They belong to the family viridae and genus virus.

29. Characteristics of Viruses
 They have no cell nucleus.
 They do not have an organized cell structure.
 They typically have one or two strands of DNA or RNA.
 They are enclosed in a protective coat of protein called the capsid.
 They do not respire, do not metabolize and do not grow but they do
reproduce.
 They are considered both as living and nonliving things, as they are
inactive outside the host cell, and are active when present inside
host cell.

31. Types of Viruses
Based on the type of nucleic acid, viruses are classified into the following types:
1. RNA Virus
 The virus that possesses RNA as genetic material is called RNA virus.
 They can either be a single-stranded or a double-stranded RNA.
 Some of the diseases caused by the RNA virus to humans include common cold, hepatitis, polio, West Nile
fever, influenza, SARS, and measles. All plant viruses are examples of the RNA virus.
 Mutation rates are higher for the RNA virus.
 Therefore, it may be considered as a one of the main reason for lacking back in preventing effective
vaccines to treat and prevent certain viral diseases.
 Double-stranded RNA virus comprises of distinct virus that differs widely based on host-virus such as
fungi, bacteria, genome, virion, and organization.
 A single-stranded RNA are categorized based on senses that are positive sense or negative sense.
1.Positive-sense RNA is similar to mRNA. They are usually translated into host cells.
2.Negative-sense RNA must be converted into positive sense RNA before translation using RNA polymerase.

32. RNA VIRUS

33. 2. DNA Virus
The virus that possesses DNA as a genetic material is called DNA virus. They are DNA dependent and
they replicate using DNA polymerase. They are usually double stranded DNA but in some cases, they can
either be single-stranded DNA.
Bacteriophages, cyanophages and most of the animal virus are examples of DNA virus.
Based on the type of host and genetic material. There are three types of virus.
1.Animal viruses –The viruses which infect and live inside the animal cell including humans are called
animal viruses. They contain DNA or RNA as genetic material. Some examples of animal viruses are rabies
virus, influenza virus, poliovirus, mumps virus, etc.
2.Plant viruses – The viruses which infect plants are called as the plant viruses. They contain RNA as a
genetic material, which remains enclosed in the protein coat. Some examples of plant viruses are potato
virus, tobacco mosaic virus, beet yellow virus, turnip yellow virus etc.
3.Bacteriophage – The viruses which invade and infects bacterial cells are called as the bacteriophage.
They contain DNA as genetic material. There are varieties of bacteriophages. Usually, each kind of
bacteriophage will attack only one species or only one strain of bacteria.

35. Viral Disease
 There are many viruses that can infect people and make them sick.
 One of the most common viral infectious diseases is influenza which are
the main causes of flu.
 Other diseases caused by virus include the common cold, measles,
mumps, yellow fever, hepatitis, AIDS, etc.
 Some virus called oncovirus also leads to a certain form of cancers.
 The most common among them is cervical cancer and liver cancer.

36. What is Bacteriophage?
 A bacteriophage is a virus that infects a bacterial cell and reproduces inside it.
 They vary a lot in their shape and genetic material.
 A bacteriophage may contain DNA or RNA.
 The genes range from four to several thousand.
 Their capsid can be isohedral, filamentous, or head-tail in shape.
Bacteriophage Structure
The bacteriophage consists of a polyhedral head, a short collar and a helical tail.
 Head- The head consists of 2000 capsomeres with double-stranded DNA enclosed within.
 Tail- The tail consists of an inner hollow tube which is surrounded by a contractile sheath with
24 annular rings. The distal end consists of a basal plate with tail fibres at each corner. The
bacteriophage attaches to the bacteria with the help of these tail fibres.

38. PHYCOLOGY

39. What is phycology ?
 Phycology is the branch of science that deals with the study of algae.
 It also includes the study of various other prokaryotic organisms like blue-green algae and
cyanobacteria. It is also known as algology.
 Algae are photosynthetic, eukaryotic organisms that are found in an aquatic environment.
 They lack true roots, leaves, and stem and do not produce flowers.
 Some are unicellular like Chlamydomonas, while others are multicellular like seaweeds and sargassum.
 Algae has great ecological importance.
 Phytoplanktons form a vital part of the food chain.
 A few algae are commercial sources of iodine, alginic acid, agar, potash, etc.
 Many large algal species are a food source for many humans.
 Few species are used in sewage-oxidation ponds.
 Algal products are also used in insulating materials such as bricks, filters, and scouring powder.
 This field became recognized in the 19th and 20th century. Phycologists focus on freshwater or
marine algae.

40. What are Algae?
 Algae exist in environments ranging from oceans, rivers, and lakes to ponds, brackish waters and even
snow.
 Algae are usually green, but they can be found in a variety of different colours.
 For instance, algae living in snow contain carotenoid pigments in addition to chlorophyll, hence giving
the surrounding snow a distinctive red hue.

41.  Multicellular examples of algae include the giant kelp and brown algae.
 Unicellular examples include diatoms, Euglenophyta and Dinoflagellates.
 Most algae require a moist or watery environment; hence, they are
ubiquitous near or inside water bodies.
 Anatomically, they are similar to another major group of photosynthetic
organisms – the land plants.
 However, that is where the differences end as algae lack many structural
components typically present in plants, such as true stems, shoots, and
leaves.
 Furthermore, they also do not have vascular tissues to circulate essential
nutrients and water throughout their body.

42. Characteristics of Algae
Specific general characteristics of algae are common to plants as well as animals.
For instance, algae can photosynthesize like plants, and they possess specialized structures
and cell-organelles, like centrioles and flagella, found only in animals. Listed below are some of the
general characteristics of algae.
 Algae are photosynthetic organisms
 Algae can be either unicellular or multicellular organisms
 Algae lack a well-defined body, so, structures like roots, stems or leaves are absent
 Algaes are found where there is adequate moisture.
 Reproduction in algae occurs in both asexual and sexual forms. Asexual reproduction occurs by
spore formation.
 Algae are free-living, although some can form a symbiotic relationship with other organisms.

43. Types of Algae
There are many types of algae. However, these are some of the more prominent types:
1. Red Algae
 Also called Rhodophyta, it is a distinctive species found in marine as well as freshwater ecosystems.
 The pigments phycocyanin and phycoerythrin are responsible for the characteristic red colouration of
the algae.
 Other pigments that provide green colouration (such as chlorophyll a) are present.
 However, they lack chlorophyll b or beta-carotene.
2. Green Algae
 It is a large, informal grouping of algae having the primary photosynthetic pigments chlorophyll a and b,
along with auxiliary pigments such as xanthophylls and beta carotene.
 Higher organisms use green algae to conduct photosynthesis for them.
 Other species of green algae have a symbiotic relationship with other organisms.
 Members are unicellular, multicellular, colonial and flagellates.
 Prominent examples of green algae include Spirogyra, Ulothrix, Volvox, etc.

44. GREEN ALGAE RED ALGAE

45. 3. Blue-green Algae
 In the past, blue-green algae were one of the most well-known types of algae.
 However, since blue-green algae are prokaryotes, they are not currently included under algae
(because all algae are classified as eukaryotic organisms).
 Also called cyanobacteria, these organisms live in moist or aquatic environments just like other
algae.
 These include dams, rivers, reservoirs, creeks, lakes and oceans. This class of bacteria obtains
energy through the process of photosynthesis.
 Ecologically, some species of blue-green algae are significant to the environment as it fixes the
nitrogen in the soil. Hence, these are also called nitrogen-fixing bacteria. E.g. Nostoc, Anabaena,
etc.
 However, other types of blue-green algae can be toxic to human beings. They can either be
neurotoxic (affects the respiratory or nervous system, causing paralysis) or hepatotoxic (causes
the liver to fail).
 Moreover, some can act as the indicators of environmental health, signalling the extent of
pollution.

46. BLUE GREEN ALGAE

47. Examples of Algae
Prominent examples of algae include:
 Ulothrix
 Fucus
 Porphyra
 Spirogyra
ULOTHRIX FUCUS PORPHYRA
SPIROGYRA

48. PARASITOLOGY

49. What is parasitology ?
 Parasitology is the study of species that depend on others for survival that cause harm to the species on
which it depends.
 They can be plant or animal.
 The former is a type of plant that depends on another plant for its life cycle.
Those in the animal kingdom are broadly broken down into three groups:
1. Protozoa, the animal-like single-cell organisms that can be ingested or transmitted by insect bites. Malaria
is an example of this. Mosquitoes carry the protozoa which then infects the host when the mosquito feeds,
making its way into the bloodstream
2. Parasitic worms called helminths such as the tapeworm which lives inside the human gut, typically ingested
from eating undercooked meat from an infected animal . Some parasitic worms in tropical countries can
burrow into the skin of the foot
3. Arthropods such as insects and arachnids that carry disease or through their biological functions, cause
them. The most common example in the west today are ticks and flea - human and animal. This group also
includes the sexually-transmitted pubic lice

50.  Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological
discipline, the scope of parasitology is not determined by the organism or environment in question but by
their way of life.
 This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell
biology, bioinformatics, biochemistry, molecular biology, immunology, genetics, evolution and ecology.

51. PROTOZOOLOGY

52. What is protozoology ?
 The term protozoology defined the study of protozoans.
 In the latter half of the 17th century, Netherland scientist Antonie van
Leeuwenhoek first observed the protozoans under a simple microscope.
 A person who was specialized in protozoology is known as protozoologists.
Protozoans are common and can easily found around the world.
 Many protozoans show particular interest in human beings.
 As they cause various diseases like amoebic dysentery, malaria, and African
trypanosomiasis.
 Certain protozoans will have an extensive fossil record, they are termed
foraminifera.
 They are much useful for the geologist to locate petroleum deposits.
 Also, researchers are widely using the protozoans as an experimental organism
during the study of cells and molecular biology.

53. What are Protozoans?
 Protozoans are the plural form of protozoa or protozoan.
 The protozoa is a subkingdom, which comes under the kingdom Protista.
 But they are commonly placed under the kingdom called Animalia.
 More than 50,000 free-living species have been described under the sub-classification protozoa.
 Protozoans are the single-celled organisms found across the world in most habitats.
 Many protozoan species are free-living, but they cause diseases to higher animals.
 Infection caused by them ranges from asymptomatic to life-threatening.
 The infection ranges are completely depending on the species and strains of the parasites and their host
resistance.
 According to Protozoology, the shells in sedimentary rocks holds the fossil records of protozoa, which were
present in the pre-Cambrian era.
 Usually, all organisms will have protozoa in their body but only a few species cause infection to the host.

54. Where Can We Find Protozoans?
 Protozoans are widely found in moisture habitats.
 As the protozoans are small in size, they are easily distributed from one place to another.
 Marine protozoans will settle in the beach stand, the surface of the water, deep sea,
planktonic habitats, algal mats, and antarctic cols environments.
 The temperature availability, oxygen requirements, and salinity are poor for marine
protozoans.
 The polluted waters will offer rich characteristics for protozoans.
 Likewise, the soil-dwelling protozoans are widespread over the dry sands of deserts and
other various types of soil surfaces.
 In general, protozoans are widely distributed near the soil surface.

55. Structure of Protozoans
 Protozoans are the unicellular microscopic eukaryotes, which have relatively complex internal structure
and they can carry out complex metabolic processes.
 Some protozoans have propulsion structure and others will have movement.
 The size of the human parasitic protozoans ranges less than 50 μm.
 The smallest protozoa are ranged between 1 to 10 μm long.
 As protozoans are eukaryotes, the nucleus is enclosed in a membrane.
 Except for ciliate protozoa, all others have a vesicular nucleus.
 The protozoan organelles have similar functions to the organs of higher animals.
 Also, protozoans will have projections for helping the locomotion of species.
 They are cilia, pseudopodia, and flagella. Some protozoa have pellicles on their outer surface.
 They are sufficient to maintain a distinctive shape.

56. PROTOZOA STURUCTURE

57. Protozoa life cycle
 Protozoans Life Cycle Protozoa life cycle falls under different stages and they have a wide
difference in structure and activity.
 The protozoa will frequently multiply and actively feed in a particular stage.
 This stage is known as trophozoites.
 The trophozoites in greek means ‘animal that feeds’.
 These stages are usually associated with pathogenesis in parasitic species.
 While coming to hemoflagellates protozoans, it terms amastigote, epimastigote, promastigote, and
trypomastigote during the trophozoite stages.
 Here the presence and absence of flagellum and its position of kinetoplast will relate to it.
 The stage of Apicomplexa is termed tachyzoite and bradyzoite.
 The Merozoite stage can observe both during sexual and asexual reproduction of protozoa.
 During sexual reproduction, the protozoa go under gametocytes.
 Some protozoa go under the cysts stage, which is the protective membrane around the species.
 Usually, multiplication occurs inside the cysts and releases more than one organism.

59. Protozoa reproduction
 Protozoans Reproduction Binary fission is the most common form of asexual reproduction in the
protozoans like amoebas and flagellates.
 Sometimes, the multiple asexual division will occur during protozoans’ asexual reproduction.
Apicomplexa can undergo both sexual and asexual reproduction.
 During the binary fission reaction, the organelles of the individual will divide into two complete
organisms.
 That division is transverse in the ciliates and longitudinal in the flagellates, but amoebas don’t have an
apparent axis.
 Endodyogeny is also a kind of asexual division that occurs in toxoplasma and some other protozoa.
During this process, two daughter cells forms within the parent cells and the wall ruptures to release
smaller progeny.
 Apicomplexa & Schizogony commonly undergoes asexual division.
 Here, the nucleus is divided many times, and then the cytoplasm divides into smaller uninucleate
merozoites.

60.  Toxoplasma, Plasmodium, and other apicomplexans undergo the sexual cycle.
 During this process, they involve in fertilization to form the zygote, the
production of gametes, encystation of the zygote to form an oocyst, and the
formation of infective sporozoites (sporogony) within the oocyst.
 Some protozoa require two different host species, they are having complex life
cycles.
 But other protozoa required only a single host to complete their life cycle.
 That’s why a single infective protozoan entering a susceptible host can create
an immense population inside the host.
 But, the death of the host and the host’s defense mechanisms can limit the
reproduction of the protozoans.

62. NEMATOLOGY

63. What is nematology ?
 Nematology is the scientific discipline concerned with the study of nematodes, or roundworms.
 Although nematological investigation dates back to the days of Aristotle or even earlier,
nematology as an independent discipline has its recognizable beginnings in the mid to late 19th
century.
 ematologists in the 1800s also contributed to other scientific fields in important ways.
 Butschli (1875) first observed the formation of polar bodies by nuclear subdivision in a
nematode, Beneden (1883) was studying Ascaris megalocephala when he discovered the
separation of halves of each of the chromosomes from the two parents and the mechanism of
Mendelian heredity, and Boveri (1893) showed evidence for continuity of the germ plasm and
that the soma may be regarded as a by-product without influence upon heredity.
 Caenorhabditis elegans is a widely used model species, initially for neural development, and then
for genetics.
 WormBase collates research on the species.

64. What is nematodes?
 Nematodes are a group of worms. They occur naturally and are very hard to detect
visually.
 These are common soil pests that affect plants.
 The soil at low levels contains numerous Nematodes. Nematodes can enter the farm
through infected transplants.
 They are parasites of both plants and animals and attack the insects also.
 However, they cause severe damage to plants. But not all Nematodes are harmful to the
plants.
 Some play an essential role in nutrient recycling.Commonly known as roundworms, they are
unsegmented vermiform pests.
 They are free-living organisms.
 Sometimes they enter the plant to extract nutrients from the root cell.
 They stress tolerance of the plant. Plants abundant with water and nutrients help can
tolerate nematode attacks.
 Once they are present in the soil, It is almost impossible to eliminate.

65. History
 History In 1758, Carolus Linnaeus described some nematode genera (such
as Ascaris), then included in the taxon of worms, Vermes.
 The name of the group Nematoda, also called “nematodes", originally was
defined by Karl Rudolphi in 1808.
 The term came from Nematoidea, defined from Ancient Greek.
 It was later treated as family Nematodes by Burmeister in the year
1837.

66. Nematodes Characteristics
1. Tubular in appearance. It has an elongated and thin body (hair-like).
2. The alimentary canal is distinct, but the head and tail are not visually different.
3. The majority of these are tiny and can be microscopic.
4. They are free-living organisms.
5. They reproduce sexually.
6. They produce amoeboid sperm cells.
7. They have a nervous system.
8. They are parasites of both plants and animals.
9. They have cuticles that moult periodically.

67. Anatomy
 Nematodes are about 5 to 100 µm thick and 0.1 to 2.5 mm long.
 They could be from the microscopic range to as much as 5 cm, while some could be even larger,
reaching over 1m in length. The body has ridges, rings, bristles, or other distinctive structures.
 The radially symmetric head of a nematode is relatively distinct, while the rest of the body is
bilaterally symmetrical, having sensory bristles protruding outwards around the mouth.
 The mouth, which often bears teeth, has either three or six lips.
 The caudal gland is often found at the tip of the tail.
 The epidermis is a single layer of cells covered by thick collagenous cuticles.
 The cuticle is of a complex structure and has distinct layers.
 Beneath the epidermis, a layer of longitudinal muscle cells is found.
 The relatively rigid cuticle with the muscles forms a hydroskeleton.
 Projections originate from the underlines of muscle cells towards the nerve cords in which
nerve cells normally extend fibres into the muscles.