Microbiology is the study of microscopic organisms including unicellular eukaryotes and prokaryotes. Viruses, though not living, are also studied. There are more microbes in and on the human body than human cells. Branches of microbiology include virology, mycology, parasitology, bacteriology. Microorganisms can be beneficial or pathogenic. Viruses are obligate intracellular parasites that can only replicate inside host cells. Bacteria are unicellular prokaryotes that have diverse shapes and are classified by Gram staining as Gram-positive or Gram-negative based on cell wall structure.

1. MICROBIOLOGY
Danstan Phyoka Phiri
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2. MICROBIOLOGY
• Microbiology is the study of unicellular life forms that
cannot be seen with the unaided eye.
OR
• Microbiology is the scientific study of unicellular or
cell-cluster microscopic organisms.
• This includes eukaryotes such as fungi and protists,
and prokaryotes.
• Viruses, though not strictly classed as living organisms, are also
studied.
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3. •There are more microorganisms on and inside
our body than there are cells that make up our
entire body.
•Microorganisms are also referred to Microbes
(Short name).
•BRANCHES like;
•Virology, mycology, parasitology, bacteriology
and other branches.
•A microbiologist is a specialist in microbiology
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4. TYPES OF MICROORGANISMS
1. Viruses
2. Bacteria
3. Protozoa
4. Fungi and Moulds
5. Protista
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5. VIRUSES
• A virus is a small infectious agent that can replicate only
inside the living cells.
• Living organisms that cannot replicate without the host cell
• An infective agent that typically consists of a nucleic acid
molecule in a protein coat, is too small to be seen by light
microscopy, and is able to multiply only within the living
cells of a host.
• A piece of code which is capable of copying itself and
typically has a detrimental effect, such as corrupting the
system or destroying data.
• Viruses infect all forms of life, from animals and plants to
bacteria and archaea.
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7. PROPERTIES OF VIRUSES
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• Ideas differ on whether viruses are a form of life, or organic
structures that interact with living organisms.
• They are considered both as living and non living things, as
viruses are inactive when they are present outside of host cells
and are active inside of host cells.
• As they make use of raw materials and enzymes of the host cell to
reproduce and causes several infections
• Accepted forms of life use cell division to reproduce,
• Whereas viruses spontaneously assemble within cells
• They do not grow
• No cure for viruses but vaccination can prevent them from
spreading

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•They do not have a cellular structure,
•which is often seen as the basic unit of life.
•Viruses are metabolically inert:
•they do not independently reproduce or move on
their own
•The nucleic acid is composed of DNA or RNA
which can either be single or double stranded
•DNA viruses tend to replicate within the nucleus of
host cells, whereas RNA viruses generally do so in
the cytoplasm

9. •They have been described as "organisms at the edge
of life",
• Since they resemble organisms in that they possess genes
and evolve by natural selection,
• They do not respire, do not metabolize,
• Ribosomes and enzymes are absent, which are needed for
metabolism (protein formation)
• And do not grow but they do reproduce by creating
multiple copies of themselves through self-assembly
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10. HOW THEY OPERATE?
•After infecting the cell, virus insert the
genetic material into the host
•And take over that host’s function
•The host cell then produces more viral
proteins and genetic material instead of the
usual cellular products
•CALLED obligate intracellular parasites
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11. • Advantages of Viruses
They are useful in delivering genes to target cells and play a vital role in gene
therapy researches.
• Disadvantages of Viruses
There are many pathogenic viruses, which causes harm for human beings,
plants and animals.
In human beings the diseases caused by viruses are: HIV, influenza, herpes,
hepatitis small pox, cowpox, etc.
The diseases caused by viruses in plants are tobacco mosaic viruses, etc.
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12. STRUCTURE OF VIRUSES
•Viruses display a wide diversity of
shapes and sizes, called morphologies.
•In general they are much smaller than
bacteria
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13. • A complete virus particle, known as a virion (before
entering a cell, they exist in this form),
• Consists of nucleic acid surrounded by a protective coat of
protein (capsid),
• Proteins associated with nucleic acid are known as
nucleoproteins, and
• The association of viral capsid proteins with viral nucleic
acid is called a nucleocapsid.
• Complex viruses code for proteins that assist in the
construction of their capsid.
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•Some Viruses have a lipid envelope present
when the virus is outside the cell
• Some viruses have spikes (glycoproteins)
which are used for attachment to the host
cells.
•The capsid is made from proteins encoded
by the viral genome and its shape serves as
the basis for morphological distinction

15. STRUCTURE OF VIRUS
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16. SHAPES OF VIRUSES
1. Rod shape
2. Spherical shape
3. Filamentous
• Usually shapes are determined by the capsid
a) Helical shape - TMV
b) Icosahedral shape: most animal viruses
 Usually 3-dimensional and the virus looks like a 20-sided figure
with 12-evenly spaced corners
c) Complex shape (non-std): Typical of bacteriophage – A
combination of helical and icosahedral shapes e.g
polyhedral virus
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17. BACTERIOPHAGES
•A virus that infects bacteria;
•Also called a phage.
•Virus that attacks/infects and is
reproduced in the bacterium
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18. TRANSMISSION OF VIRUSES
• Direct contact transmission: This refers transmission via physical
contact between an infected and uninfected subject through kissing,
biting, or sexual intercourse, for example.
• Indirect transmission: Here, the virus is transmitted via contact with
contaminated objects or materials such as medical equipment or
shared eating utensils.
• Common vehicle transmission: This transmission mode refers to
when individuals pick up the virus from food and water supplies that
are contaminated with feces. This often causes epidemic disease.
• Airborne transmission refers to the respiratory infection that occurs
when the virus is inhaled.
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19. SOURCES OF VIRUSES
• Three competing theories try to explain the origin of viruses.
• Regressive, or reduction hypothesis: Viruses started as independent
organisms that became parasites. Over time, they shed genes that did
not help them parasitize, and they became entirely dependent on the
cells they inhabit.
• Progressive, or escape hypothesis: Viruses evolved from sections of
DNA or RNA that "escaped" from the genes of larger organisms. In
this way, they gained the ability to become independent and move
between cells.
• Virus-first hypothesis: Viruses evolved from complex molecules of
nucleic acid and proteins either before or at the same time as the first
cells appeared on Earth, billions of years ago (Peter Crosta , 2017)
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20. PHASES/CYCLES OF VIRAL
REPRODUCTION
•There are two
1. Lytic
2. Lysogenic
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21. LYTIC
• Once a virus has infected a host cell, it can replicate within that cell
thousands of times.
• Rather than dividing and reproducing in the way that cells do, viruses go
through a process called the lytic cycle.
• First, the virus replicates its DNA and protein coats, which are then
assembled into new virus particles.
• This causes the host cell to burst or “lyse,” which is why the cycle is
so-called.
• AFTER BURSTING, new virus particles that are released once the
cell has burst then infect surrounding host cells.
• The process can take as little as twelve hours, as is the case with the
norovirus, or as long as several days, as is the case with the Ebola
virus.
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22. LYSOGENIC
• Some complex viruses called phages bind their DNA to that
of their host cell or deposit small pieces of their DNA in the
cytoplasm.
• At this point the cell is called prophage
• When the cell then divides, the viral DNA is copied into the
daughter cells.
• Lysogenic cycle, is less common than the lytic cycle.
• λ (lambda) virus, which infects the E. coli bacterium
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26. BACTERIA
Singular: bacterium)
•Are a large group of unicellular,
prokaryotic microorganisms
•Bacteriology,
A branch of microbiology.
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27. DOMAINS
• TWO branches, Bacteria (formerly called Eubacteria), and Archaea,
(formerly Archaebacteria)
• The name archaea means “archaic” or“ancient.”
• Most known species of archaea live in extreme environments thought to
resemble harsh environments present millions of years ago.
• They are not like bacteria in many ways.
• They differ in the makeup of their cell walls.
• their membrane lipids, and
• in their genetics and metabolism.
• For example, archaeal cell walls do not have peptidoglycan; a protein-
carbohydrate compound found in bacterial cell walls.
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28. • Archaeal cell walls have different amino acids than bacterial cell
walls do.
• Archaea are like eukaryotic cells in that archaeal genes have
introns, portions of DNA that do not code for amino acids and that
are transcribed into RNA but are removed before being translated
into proteins
•First discovered in extreme environments, such
as swamps, salt lakes, and hot springs.
•Recently, scientists believed that archaea lived
only in these extreme environments.
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29. ARCHAEAL GROUPS
• Genetic analysis of archaea has revealed at least three groups
of archaea
• Methanogens are named for their unique way of getting
energy:
• they convert hydrogen gas and carbon dioxide into methane gas.
• Oxygen is poisonous to them, can live only in anaerobic environments: such as
in deep fresh water, marine mud, swamp mud, and sewage.
• The methane that bubbles out at sites such as swamps is called marsh gas.
• Methanogens also thrive in the intestinal tracts of organisms such as cows and
termites.
• A cow can belch between 200 and 400 liters of methane per day.
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30. HALOPHILES
• Salt-loving archaea
• Live in environments that have very high salt
concentrations; great salt lake and the dead sea.
• High salt concentrations would kill most bacteria but
favor the growth of their adaptability
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31. THERMOACIDOPHILES
• in very acidic environments that have very high temperatures,
• hot springs
• Some thermoacidophiles live at temperatures up to 110°C (230°F) and at
a pH of less than 2.
• also live near volcanic vents on land or near hydrothermal vents called
black smokers.
• Black smokers are cracks in the ocean floor that leak very hot, dark-colored, acidic water, as
shown in Figure 23-2.
• Scientists have found large communities f worms, clams, crabs, and mussels living near these
thermal vents.
• These communities live at great depths and in total darkness,
• where photosynthesis cannot take place,
• so they depend on thermoacidophilic archaea as a primary source of food
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32. DOMAIN BACTERIA
• Most known prokaryotes are bacteria.
• They occur in many shapes and sizes and have distinct
biochemical and genetic characteristics.
• This wide variety of shapes is determined by the
bacterial cell wall and cytoskeleton,
• and is important because it can influence the ability of
bacteria to acquire nutrients, attach to surfaces, swim
through liquids and escape predators.
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33. • Three basic shapes,
• Rod-shaped: bacilli
• Sphere-shaped: cocci, and
• Spiral shaped: spirilla
• When cocci occur in chains: streptococci
• Grapelike clusters of cocci: staphylococci
• Neustria form diploids (pairs)
• Others have tetrahedral or cuboidal shapes
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34. SHAPES OF BACTERIA
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35. GRAM STAIN
• Based on the structure of their cell walls THROUGH a
laboratory technique called the Gram stain.
• Gram negative bacteria have cell walls that are complex and
have relatively small amounts of peptidoglycan.
• Take up the second, red dye of the Gram stain process which
makes the cells appear reddish pink under a microscope.
• Gram-positive bacteria are simpler and have more
peptidoglycan.
• They retain the purple dye in their cell walls and appear
purple under a microscope
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37. THE GRAM’S STAINING METHOD
• Probably the most commonly used staining procedure
in microbiology.
• Extremely useful in identifying bacteria.
It is important that you understand the color changes that
occur at each step in the Gram stain.
Also important that you understand the function of each
reagent used in this procedure.
It takes some practice and patience to be able to reliably
Gram stain.
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38. THE GRAM’S STAINING METHOD
• The Gram stain is a DIFFERENTIAL STAIN which allows most
bacteria to be divided into two groups
Gram-positive bacteria and Gram-negative bacteria.
• The technique is based on the fact that the Gram positive cell wall has
a stronger attraction for crystal violet when Gram's iodine is applied
than does the Gram negative cell wall.
Gram's iodine is known as a MORDANT.
It is able to form a complex with the crystal violet that is attached more tightly
to the Gram-positive cell wall than to the Gram-negative cell wall.
• This complex can easily be washed away from the Gram-negative cell
wall with ethyl alcohol.
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39. • Gram-positive bacteria, however, are able to retain the crystal
violet and therefore will remain purple
after DECOLORIZING with alcohol.
• Since Gram-negative bacteria will be colorless after
decolorizing with alcohol, COUNTERSTAINING with
safranin will make them appear pink.
• It is known, however, that the two groups of bacteria have
very different cell walls and
• that the type of cell wall dictates the way a bacterium responds to
the Gram stain.
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40. GRAM STAINING PROCEDURE:
• Cover with CRYSTAL VIOLET for 20 seconds. (PRIMARY STAIN)
• Gently rinse off the stain with water and shake off the excess.
• Cover with GRAM'S IODINE for one minute. (MORDANT)
• Pour off the Gram's iodine.
• Run 95% ETHYL ALCOHOL down the slide until the solvent runs clear
(about 10-20 seconds).
• This step is critical! Thick smears require more time than thin ones. (Decolorizing
agent)
• Rinse with water to stop the action of the alcohol.
• Cover with SAFRANIN for 20 seconds.(COUNTER STAIN)
• Gently rinse off the stain with water. Clean off the bottom of the slide with
95% alcohol.
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41. • Gram-positive bacteria possess a thick cell wall
• Retain crystal violet color and stain dark violet or pulple after washing with
alcohol e.g. streptococcus, streptomyces, Enterococcus)
• Contains many layers of peptidoglycan and teichoic acids.
• In contrast, Gram-negative bacteria have a relatively thin cell wall
• Decolorize to accept counterstain. Stain red (safranin) e.g. enterobacter,
Escherichia coli.
• Consisting of a few layers of peptidoglycan surrounded by a second lipid
membrane containing lipopolysaccharides and lipoproteins.
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42. GRAM POSITIVE BACTERIA
• streptococcal species; causes strep throat and
• Clostridium botulinum; causes botulism.
• Botulinum toxin is used medicinally to treat painful muscle contractions and, more recently, to
erase “frown lines” from the face.
• Lactic acid bacterial species; genus Lactobacilli, which turn milk sour and make
yogurt,
• Anthrax caused by the Grampositive rod Bacillus anthracis,
• B. anthracis is often linked to its use as a biological weapon
• Actinomycetes; grow in soil and make antibiotics, chemicals that inhibit the
growth of or kill other microorganisms.
• Antibiotics kill neighboring bacteria and fungi that compete for resources.
• Streptomycin (genus Streptomyces) and tetracycline are examples of antibiotics
that are used medicinally.
• Members of the genus Mycobacteria, another genus of actinomycetes, cause
tuberculosis and Hansen’s disease (leprosy).
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44. • capsule. These sugars bind to the cell wall and protect the cell against drying or
harsh chemicals.
• also helps protect a pathogenic (disease-causing) bacterium from the host’s white blood
cells, which could otherwise engulf the bacterium. A capsule
• Pili (singular, pilus) are short, hairlike protein structures on the surface of some
bacteria.
• help bacteria connect to each other and to surfaces, such as those of a host cell.
• Can also serve as a bridge to pass genetic material between bacteria.
• channel for plasmid transfer from one cell to another.
Also used for attachment to substrate.
• Stalks: (in stalked bacteria) – for attachment to substrate
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45. ENDOSPORES
• Thick-coated, resistant structure formed by some gram-positive
bacteria
• When environmental conditions become harsh.
• The harsh conditions may destroy the original cell, but the endospore containing the cell’s dna
can survive.
• Can resist high temperatures, strong chemicals, radiation, drying, and
other environmental extremes.
• When good conditions return, the endospore gives rise to a normal
bacterial cell.
• Species of the genera bacillus and clostridium can form endospores.
• The endospores of c. Botulinum can germinate in improperly sterilized
canned foods.
• Make a toxin that if eaten can cause the nerve disease botulism.
• While rare, botulism is often fatal if it is not treated promptly.
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46. MOVEMENT: FLAGELLUM
Run away from danger,
Locate food
Towards or away from light
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47. TYPES OF FLAGELLATION
1.Polar: found at cell poles
i. Monotrichous – have one flagella at the poles. Zig-zag
movement
ii. Lophotrichous – more than one flagella at the poles
iii. Amphitrichoous – flagella at both poles
2.Peritrichous: flagella located all around the bacterio
body
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49. Chemotaxis AND Myxobacteria
• Movement toward or away from a stimulus is called taxis
• chemotaxis, bacteria react to chemical stimuli by moving
toward food or away from a toxin.
• Species of the genus Myxobacteria, form a layer of slime
• Wavelike contractions of the outer membrane move the organisms
through the slime.
• Spiral-shaped bacteria move by a corkscrew-like rotation.
• Filaments inside the organism’s cell walls contract and cause the
bacterium to turn and move ahead.
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50. NUTRITION AND METABOLISM
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51. PROKARYOTIC HABITATS
 obligate anaerobes; cannot live where molecular oxygen, O2, is
present.
 Clostridium tetani causes the nerve disease tetanus.
 Facultative anaerobes; can live with or without oxygen.
 Escherichia coli, which is common in the human digestive tract
 obligate aerobes; need oxygen to live
 Mycobacterium tuberculosis: TB
 Prokaryotes have varying temperature requirements for growth.
 Psychrophilic (cold-loving); prokaryotes grow well at 0°C to 20°C (32°F to
68°F).
 Their cellular enzymes and cell membranes work well at cold temperatures.
Some prokaryotes of the
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52. • Mesophiles; that grow best at temperatures between
20°C (68°F) and 40°C (104°F) are
• Humans are also classified as mesophiles
• Thermophiles; very hot temperatures between 45°C
(113°F) and 110°C (230°F
• Acidophiles; grow best at a pH of 6.5 to 7.5 (7.0 is
neutral).
• such as those that make yogurt and sour cream from milk,
favor acidic environments
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53. REPRODUCTION IN BACTERIA
Asexual e.g. Binary fission
During binary fission, the single DNA molecule
replicates and both copies attach to the cell membrane
the two daughter DNA molecules are pulled to
opposite ends of the cell.
Finally, the cell membrane pinches in two to form two
identical daughter cells
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54. •Despite being an effective way of reproduction in
bacteria,
•Binary fission does produce problems since the cells
produced are identical,
•They are all susceptible to the same types of
antibiotics.
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55. GENETIC (BACTERIAL) RECOMBINATION
•Prokaryotes can exchange pieces of DNA that
can be added to the cell’s DNA without
reproduction.
•This process can be accomplished through one of
the following processes
1.Conjugation,
2.Transformation, Or
3.Transduction
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56. 1. Transformation occurs when a prokaryote takes in DNA from its
outside environment.
• Some bacteria are capable of taking up DNA remnants of dead bacterial cells
from their environment
2. Conjugation is the process by which two prokaryotes bind together
and one cell transfers DNA to the other cell through a structure
called a sex pilus.
3. transduction, a virus obtains a small part of DNA from a host
prokaryote. The virus then copies itself inside the host, and new
copies of the prokaryotic DNA are made with the viral DNA. After
the new viruses have been released, they carry the prokaryotic gene
to the next prokaroyote
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57. TRANSDUCTION
•generalized and specialized transduction
•Bacteriophage infects another bacterium, it injects
the DNA fragment from the previous bacterium.
• DNA fragment then becomes inserted into the DNA of
the new bacterium. This is generalized transduction.
•Specialized transduction, fragments of the host
bacterium's DNA become incorporated into the viral
genomes of the new bacteriophages.
• DNA fragments can then be transferred to any new
bacteria that these bacteriophages infect
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58. IMPORTANCE
•Bacteria are vital in recycling nutrients, with many steps
in nutrient cycles depending on these organisms, such as
the fixation of nitrogen from the atmosphere and
putrefaction.
•Some bacteria are normal flora of the body (helps in
manufacturing of vitamins in the body).
Used in food production
Used in production of antibiotics
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59. ADVERSE EFFECTS
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1. Causes diseases, and
2. Decomposition of food substances.
However, most bacteria have not been characterized,
and only about half of the phyla of bacteria have
species that can be grown in the laboratory

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61. FUNGI
 Eukaryotic, non-photosynthetic (Achlorophylic) organisms, and most are
multicellular heterotrophs (unable to synthesize their own food )
 Most fungi are microscopic molds or yeasts.
 Molds, such as the fungi that grow on bread and oranges, are tangled masses
of filaments of cells.
 Yeasts: unicellular fungi whose colonies resemble those of bacteria.
 Usually a kingdom of multicellular eukaryotic organisms
 Have important roles in nutrient cycling in an ecosystem
 Decomposers of dead organic matter
 There is considerable variation in the structure, size, and complexity of various
fungal species.
 They include the microscopic yeasts, the molds seen on contaminated bread, and
the common mushrooms.
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62. MYCOLOGY
• STRUCTURE OF FUNGI
• Filaments of fungi are called hyphae
• Have cell walls ontaining chitin, a polysaccharide that also makes up the
exoskeleton of insects, crustaceans, and other arthropods.
• The presence of chitin distinguishes cell walls of fungi from those
of plants,
• which have cellulose but no chitin.
• Mycelium-mass of hyphae that forms the body of a fungus.
• In some species, the cells that make up hyphae are divided by
cross sections called septa (singular, septum).
• Septate fungi-cells are divided by cross walls
• coenocytic fungi (Aseptate) - the cytoplasm passes through and
among cells of the hypha uninterrupted by cross walls.
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64. FUNGAL GROWTH
• Hyphae increase in length by cellular growth and division at the tip.
• As the hyphae grow, the size of the mycelium increases.
• Saprophytic-When hyphae encounter organic matter, such as a tree trunk or
dead animal, they secrete digestive enzymes and then absorb the digested
nutrients.
• SIZE: From the microscopic yeast to the largest single organism in the
world.
• Several species of fungi can change form in response to changes in their
environment.
• For example, Histoplasma capsulatum, which causes a severe disease in humans that
can resemble tuberculosis,
• normally grows as a mycelium in soil.
• When it invades a human, the increased temperature and available nutrients cause the
fungus to grow unicellularly as a yeast.
• Dimorphism- the ability to exist in two different forms
• Dimorphic-the ability to shift from the yeast form to the mold form and vice versa
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65. • They can reproduce sexually or asexually
• Majority of fungi are spore producers
• Examples include: Molds, Penicillin, Yeast, Truffles,
Mushrooms
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REPRODUCTION

66. ASEXUAL
• Asexually, fungi produce thousands of genetically identical haploid
spores, usually on modified cells of the hyphae.
• When these spores are placed in favorable environmental conditions,
they germinate and grow new hyphae, each of which can form a
mycelium and produce thousands of new asexual spores.
• A variety of asexual spores are formed by different fungi.
• Sporangiophores: specialized hyphae that look like upright stalks. THEY
ARE CONTAINED IN A SAC CALLED A sporangium
• conidia (singular): formed without the protection of a sac.
• Conidia are formed on top of a stalk-like structure called a conidiophore.
• Penicillium, which is used to produce penicillin and certain types of cheeses, is a fungus
that reproduces asexually by means of conidia.
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67. •May also occur by fragmentation.
•In this process, a septate hypha dries and shatters,
releasing individual cells that act as spores.
•The fungus that causes athlete’s foot reproduces
this way.
•Yeasts reproduce by a process called budding,
•A process in which part of a yeast cell pinches itself
off to produce a small offspring cell.
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69. SEXUAL
• Fungi are neither male nor female.
• Instead, they occur in mating types that are sometimes called minus and
plus.
• When two different mating types of the same species encounter one another,
the hyphae of one mating type fuse with the hyphae of the opposite mating
type.
• These fused (Cloned) hyphae give rise to a specialized structure, which
produces and scatters genetically diverse spores.
• This ability of fungi to reproduce both sexually and asexually provides an adaptive
advantage.
• When the environment is favorable, rapid asexual reproduction can ensure an
increased spread of the species.
• During environmental stress, sexual reproduction can ensure genetic diversity,
increasing the likelihood that offspring will be better adapted to the new
environmental conditions.
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71. NUTRITION OF FUNGI
Fungi grow best where there is a rich supply of organic
matter.
Most fungi are saprobic, obtaining nutrients from dead
organic matter.
Since they are achlorophylic, fungi cannot perform
photosynthesis and must obtain their nutrients from
preformed organic matter.
 They are therefore chemo heterotrophic organisms.
pH- Most fungi grow at an acidic pH of about 5.0, although
some species grow at lower and higher pH levels.
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72. Temperature- Most fungi grow at about 25°C (room
temperature),
Except for pathogens, which grow at 37°C (body
temperature).
Energy - They store glycogen for their energy needs
and use glucose and maltose for immediate energy
metabolism.
Oxygen- Most species are aerobic,
Except for the fermentation yeasts that grow in both
aerobic and anaerobic environments.
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73. USES OF FUNGI
•Fungi have a variety of uses that make them very
important. These include:
1. Mycorrhizal relationship between some of the
fungi and plants benefits various plants in many
ways.
• For instance, whereas the fungi obtains nutrients from
the plant, the fungi may make various material such as
phosphates readily available for the plant.
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74. INSECTICIDES AND MEDICINES
Some of the fungi act as biological insecticides.
For instance, such Fungi as Beauveria bassiana allow
farmers to control such pests as the emerald ash borer that
tend to cause damage to plants.
On the other hand, such fungi as Penicillum species are
important because they are used to develop vaccines to
treat various diseases.
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76. COMMON FUNGAL INFECTIONS
Fungi may infect the skin, hair, nails, and tissues of the body.
Ringworm - can occur almost anywhere on the skin.
Athlete’s foot - occurs on the foot and between the toes
Candidiasis (commonly known as a yeast infection) –
 By Candida albicans – commonly found in the mouth, intestine,
and, in women, in the vaginal tract. Generally,
 C. albicans exists in balance with other microorganisms,
 such as bacteria that live in and on the body.
 Abnormal balance of the microorganisms, due to use of antibiotics,
or when pregnancy or illness occurs, causes C. albicans to flourish
and cause candidiasis
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78. PROTISTS
• Single-celled or simple multicellular eukaryotic
organisms that generally do not fit in any other
kingdom
• A diverse collection of eukaryotic organisms, such as
protozoa, algae, slime molds, and water molds.
• Sometimes described as animal-like, plantlike, or
fungus-like.
• However, these organisms lack the cellular
differentiation found in animals, plants, and fungi.
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79. CHARACTERISTICS
• Eukaryotes
• Most are microscopic,
• but a few protists, such as some algae, are macroscopic
• Protists are the most diverse group of eukaryotes.
• Have varying body plans,
• Types of movement, and
• Means of obtaining food.
• Most living protists contain mitochondria.
• Some protists, (Euglena) also contain chloroplasts.
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80. CHARACTERISTICS
• Ecology- Exist throughout aqueous environments and
soil, occupying a range of trophic levels.
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81. MOTILITY
1. Flagellates -They move around with whip-like tails
called flagella,
2. Ciliates- Using hair-like structures called cilia,
3. Pseudopods – Using foot-like structures called
pseudopodia (Pseudopodial Movement)
4. Myonemes (Peristaltic movt) - are small thread-like
contractile fibrils usually located in the inner layer of
ectoplasm.
• Others do not move at all.
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82. DIGESTION
•May absorb food via their cell membranes, some,
e.g. amoebas, surround food and engulf it,
•and yet others have openings or "mouth pores" into
which they sweep food.
•All protozoa, digest their food in stomach-like
compartments called vacuoles.
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83. 1. Holozoic or Zoo-Trophic Nutrition - involves the
processes like intake of food, i.e., ingestion,
digestion, absorption and egestion of undigested
residues
2. Pinocytosis - It is related to the ingestion of liquid
food by invagination of the general body surface.
(also called cell-drinking)
3. Autotrophic or Holophytic Nutrition - e.g.,
Euglena, Noctiluca
4. Saprozoic Nutrition
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84. PARASITIC NUTRITION
• The parasitic forms feed either holozoically or saprozoically.
• Thus, the parasites may be grouped into two categories
depending on the nature of food and their mode of feeding
1. Food-robbers: The parasites feeding upon the undigested or
digested foodstuffs of their hosts, such as some ciliate parasites
like Nyctotherus, Balantidium
2. Pathogenic: The protozoan parasites causing harm to their hosts,
usually feed upon the living tissues of the host.
 They absorb liquid food through their general body surface, e.g.,
Trypanosoma, Plasmodium, etc
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85. 6. Coprozoic Nutrition - Certain free-living
protozoans are in habit of feeding upon the faecal
matters of the other organisms like Clamydophrys
and Dimastigamoeba.
7. Mixotrophic Nutrition - Some Protozoa nourish
themselves by more than one method at the same
time or at different times due to change in
environment e.g., Euglena gracilis and Peranema are
both saprozoic and autotrophic in their nutrition, and
some flagellates are both autorophic and zootrophic.
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86. ECOLOGICAL ROLE
• Thus, they play an important role in the transfer of
bacterial and algal production to successive trophic
levels.
• As predators, they prey upon unicellular or
filamentous algae, bacteria, and micro-fungi.
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87. • Are both herbivores and consumers in the decomposer
link of the food chain.
• They also control bacteria populations and biomass to
some extent.
• The malaria parasites (Plasmodium spp.),
trypanosomes and leishmania are also important as
parasites and symbionts of multicellular animals.
• Symbiont is an organism that is very closely associated
with another organism (usually a large, host).
• Can live in, on, or sometimes very close to the host
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88. CLASSIFICATION
• Classified by the characteristics that resemble those of
fungi, plants, and animals.
• Fungi-like - Reproduction of some protists resembles
the reproduction of fungi
• Plant-like - capture light energy for photosynthesis
• Animal – like - move and consume other organisms,
as animals do
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89. LIFE CYCLE
Some protozoa have complex life cycles requiring two
different host species;
 Others require only a single host to complete the life cycle.
A single infective protozoan entering a susceptible
host has the potential to produce an immense
population.
However, reproduction is limited by events such as
death of the host or by the host's defense mechanisms,
 Which may either eliminate the parasite or balance parasite
reproduction to yield a chronic infection.
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90. For example, malaria can result when only a few
sporozoites of Plasmodium falciparum are introduced by a
feeding Anopheles mosquito into a person with no
immunity.
a motile spore-like stage in the life cycle of some parasitic
sporozoans (e.g. the malaria organism), which is typically the
infective agent introduced into a host.
Repeated cycles of schizogony in the bloodstream can
result in the infection of 10 percent or more of the
erythrocytes
About 400 million parasites per milliliter of blood.
Schizogony is an asexual reproduction by multiple fission
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91. LIFE CYCLE
• Some protozoa have life stages alternating between
Excystation & Encystation. E.g Trophozoits and Cysts
• As cysts, protozoa can survive harsh conditions,
• such as exposure to extreme temperatures or harmful
chemicals,
• Long periods without access to nutrients, water, or oxygen.
• Being a cyst enables parasitic species to survive
outside of a host, and allows their transmission from
one host to another.
• Cysts are stages with a protective membrane or thickened wall.
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92. TROPHOZOITES
• When protozoa are in the form of trophozoites (Greek, tropho = to
nourish), they actively feed and they multiply frequently.
• ENCYSTATION- The conversion of a trophozoite to cyst form, while
the process of transforming back into a trophozoite is known as
EXCYSTATION.
• Protozoa can reproduce by binary fission or multiple fissions.
• Multiple fission, a form of cell division that produces more than two offspring.
• Both types of fission produce offspring that are genetically identical to the parent cell.
• Some protozoa reproduce sexually: conjugation.
• Two individuals join and exchange genetic material stored in a small second nucleus.
• Cells divide to produce four offspring.
• Offspring are genetically different from the parent cells.
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94. LIFE CYCLE OF SCHISTOSTOMA
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