Download unit5hbacteriaprotist fungi

BACTERIA. PROTISTS. FUNGAL
AND VIRUSES
Microbiology is the study of microorganisms, a collection of
organisms that are generally only be visible with a microscope.
Members of the microbial world are very diverse and include:
bacteria, protists, fungi and viruses.
MICROSCOPES:
• Microscopes permit extremely small objects to be
seen, objects measured in the metric system in
micrometers (um) and nanometers(nm).
• A micrometer is equivalent to a millionth of a meter,
while a nanometer is a billionth of a meter.
• Bacteria, fungi, protozoa, and unicellular algae are
normally measured in micrometers, while viruses are
commonly measured in nanometers.
• A typical bacterium measures about 2 micrometers in
length and 1micrometer in width.
There are various types of microscopes
available for use in microbiology:
1. light microscope: the common light microscope used in lab is
the compound microscope because it contains two types of
lenses (ocular and objective)
2. Electron microscope: source of energy is a beam of
electrons:2
types:
• a. transmission electron microscope: (TEM) scans internal
structures of the organism
• b. Scannins electron microscope: (SEM) scans external
structures of an organisms
• • Both TEM and SEM give a 3D view of microorganisms but
the draw back is the organisms must be dead.
• The ability to see clearly two items as separate objects
under the microscope is called resolution.
• The resolving power of a lens refers to the size of the
smallest object that can be seen with that lens.
• Most microscopes exhibit parfocal which means that
the microscope remains in focus when one switches
from one objective to the next objective.
• The total magnification of a microscope is the
objective power times the ocular power.
• The numerical aperture (NA) refers to the widest cone
of light that can enter the lens; the NA is engraved on
the side of the objective lens.
• To increase the resolution with oil-immersion lens (
one that is exceedingly narrow, and most light misses
it and is poorly seen without the resolution) immersion oil
is used (it has the same light-bending ability as the glass
slide, so keeps light in a straight line as it passes through
the glass slide.
STAINING TECHNIQUES:
• Because microbial cytoplasm is usually transparent, it is necessary
to stain microorganisms before they can be viewed with a light
microscope.
• In some cases, staining is unnecessary, for example when
microorganisms are very large or when motility is to be studied, and
a drop of the microorganisms can be placed directly on the slide and
observed...this is called a wet mount.
• A wet mount can also be prepared by placing a droop of culture on a
cover slip and then inverting it over a hollowed-out slide....this is
called a hanging drop.
• In preparation for staining, a small sample of
microorganisms is placed on a slide and permitted to air
dry.
• The smear is heat fixed by quickly passing it over
aflame.
• Heat fixing kills the organisms, makes them adhere to
the slide, and permits them to accept the stain.
• Simple stain techniques can be performed with basic
dyes such as crystal violet or methylene blue, positively
charged dyes that are attracted to the negatively
charged materials of the microbial cytoplasm.
• Differential staining distinguish two kinds of organisms
ex gram stains.
CLASSIFICATION:
• Morphological characteristics are useful in the
identification of microorganisms, especially when
aided by differential staining techniques.
• The possession of various enzymes as determined by
biochemical tests is used in the identification of the
microorganism.
• Serological tests, involving the reactions of
microorganisms with specific antibodies, are useful in
determining the identity of strains and species as well as
relationships between organisms.
BACTERIA:
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1.
2.
3.
4.
Bacteria are divided into four divisions.
. Archaebacteria live in harsh conditions,
Eubacteria-true bacteria,
Cyanobacteria- blue-green algae,
Prochorobacetia-new group little known)
•
•
A group of bacteria derived from a single cell is called a strain.
Closely related strains constitute a species.
•
Bacteria are divided into sections based on Gram-stain
reaction,
cellular morphology, oxygen requirements, and nutritional
properties.
•
The entire kingdom is composed of prokaryotes.
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1.
2.
3.
•
•
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4.
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b.
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> Characteristics include:
Unicellular prokaryotes
both heterotrophic and autotrophic
Cell shape includes;
a. bacillus: rod shape
b. coccus: sphere shape
c. spirillium: spiral shape
Cell grouping includes:
a. Staphlo: clusters
Strepto: chain
Both aerobic and anaerobic
Spirochetes and Spirilla:
• Spirochetes have a spiral shape, a flexible cell wall and
motility mechanisms based on structures called axial
filaments.
• They are very slender and difficult to see under the light
microscope.
• They are cultivated with great difficulty (some not at all)
andare classified based on morphology and
pathogenicity.
• Certain spirochetes inhabit water environments while
othersare parasites of arthropods and warm blooded
animals
• Ex of a spirochete is
• Borrelia burgdorferi {agent of lyme
disease),
• Treponema pallidum (agent of syphilis) and
Leptospira interrosans (agent of leptospirosis)
• Spirillia have spiral shape, a rigid cell wall, and motility
mechanisms based on polar flagella.
• The genera Spirillum, Aquaspirillum and Azospirulum are
widely dispersed, all being aerobic
• Ex include Spirillum minor ( rat bite fever),
Camplobacter jejuni (intestinal infection accompanied
by diarrhea)
Gram-Negative Rods and Cocci
1. Bdellovibrios are aerobic gram-negative, curved rods that prey
on other bacteria. They attach to the surface of a bacterium,
rotates, and bores a hole through the host cell wall. Ex Bdellovibrio
bacteriovorus
2. Pseudomonads: aerobic, gram-negative rods, motility is with polar
flagella. Ex Pseudomonas aersinosa which causes urinary tract
infections and infections of burned tissue
3. Azotobacter and Rhizobium: important for their ability to fix
nitrogen in the environment.
4. Enterobacteria: facultatively anaerobic, inhabit the human
intestines
Ex Salmonella ( agent for salmonellosis) Klebsiella (agent
pneumonia),
E. coli
5. Vibrios: curved, gram-negative, facultatively
anaerobic rods. Ex Vibrio cholerae (cholera)
6. Pasteurellas: small size and enable to move. Ex
Haemophilus influenza (meningitis)
7. Sulfur bacteria: important in sulfur cycle for their ability
to use sulfur and convert it to other compounds that can
be used by plants to synthesize sulfur-containing amino
acids.
8. Veillonella: gram negative cocci, anaerobic diplococci,
part of the normal flora of the mouth and
gastrointestinal tract.
9. Gliding bacteria: move by gliding in a layer of slime,
which they
produce
10. Mvxobacteria: gliding bacteria, aerobic rods,
nonphotosynthetic
11. Sheathed bacteria: filamentous bacteria with cell walls
enclosed in a sheath of polysaccharides and
lipoproteins.
12.Photoautotrophic bacteria: obtain their energy
from sunlight Ex Cyanobacteria
13..Chemoautotrophic bacteria: gram negative
bacteria deriving their energy from chemical
reactions involving inorganic material. Ex
Nitrobactera
GRAM-POSITIVE BACTERIA:
1. Streptococci: spherical bacteria, aerobic, certain species partly
destroy the red blood cells ( alpha-hemolytic) others completely
destroy the blood cells (beta-hemolytic), Ex Streptococcus
pneumoniae (bacterial pneumonia), Streptococcus pyosenes (strep
throat)
2. Staphylococci: normally associated with the skin and mucous
membranes, certain species cause boils and abscesses. Ex
Staphylococcus aureus (food poisoning)
3. Lactobacilli: rod-shaped single cells or chains, produce lactic acid,
associated with the flora of the mouth
4. Bacillus and Clostridium species: gram positive rod
shaped bacteria, produce highly resistant endospores,
found in the soil, air ex Bacillus anthracis (anthrax),
Clostridium (tetanus)
5. Corynebacteria: gram positive rods ex
Corynebacterium diptheria (human diptheria)
6. Actinomyces and Arthrobacter: Actinomyces are
positive rods, assumes many shapes and usually form
branching filaments, cause lumpy jaw. Arthrobacter:
found in soil and many degrade
herbicides and pesticides.
ACID FAST BACILLI:
1. Mycobacteria: are rod-shaped, the presence
ofmycoloic acid makes the bacteria very difficult to
stain, but when heat or other agents are used to force
carbolfuschsin (stain) into the cytoplasm, the bacteria
resisted colorization with a dilute acid-alcohol solution.
• Therefore,
they are called acid-fast. Ex Mycobacteria tuberculosis
(tuberculosis) M. leprae (leprosy)
2. Norcardioforms: include nine genera of aerobic, acid
fast rods form short filaments, found throughout nature
in many types of soil and aquatic environments. Ex N.
asteroids (infection of human lungs)
ARCHAEBACTERIA:
• Differ from all other bacteria (Eubacteria)
• Ex include:
• 1) methanogens (anaerobic found in swamps,
sewage
2) halobacteria (high-salt environment)
• 3) extreme thermophiles (live at extremely high
temperatures)
SUBMICROSCOPIC BACTERIA:
1. Rickettsiae:
•
Obligate intracellular parasite, rod or coccoid shaped,
cannot be seen with light microscope, gram stain not used for
identification (however walls are characteristically gram negative),
cultivation in lab difficult
• This pathogen is responsible for Rocky
Mountain spotted fever, epidemic typhus, Q fever and ehrlichiosis
2. Chlamydia:
• an extremely tiny bacteria, acts as an obligate
intracellular parasite, gram stain not used for identification (
typically gram negative) growth cycle takes place within host cell.
• Responsible for: psittacosis (disease of lung tissue), trachoma
(disease of eye) and chlamydia (infection of reproductive tract)
3. Mycovlasmas:
•
extremely small bacteria, lacks cell walls, vary in
shape (pleomorphic), causes mild pneumonia in humans, and
problems with the respiratory tract and urinary tract
VIRUSES:
• Depending on one's viewpoint, viruses may be
reguarded as complex aggregates of nonliving
chemicals, or very simple living microbes.
• Viruses are not placed in a kingdom.
• They are not composed of cells and are incapable of
growth without a host cell
• They are noncellular genetic elements that use a living
cell for their replication and have an extracellular state.
• Viruses are ultramicroscopic particles containing
nucleic acid surrounded by protein, and in some
cases other macromolecular components such as a
membrane-like envelope.
• The virus particle is also known as a virion.
• The viron is metabolically inert and does not grow or
carry on respiratory or biosynthetic functions.
• There are no technical names for viruses.
Viral Structure and Replication:
• Viruses vary in size and shape (smallest viruses are
about 0.02um, largest .3 um) (poll virus among smallest,
smallpox among largest)
• Certain viruses contain RNA, while other viruses have
DNA.
• The Nucleic acid portion of the viruses is known as the
genome.
• The genome of the virus is surrounded by a protein coat
known as a capsid, which is formed from a number of
individual protein molecules called capsomeres.
• The combination of genome and capsid is called the
viral nucleocapsid
• Some kinds of viruses contain envelopes ( encloses the
nuceocapsid)
• The envelope contains viral-specified proteins that make
it unique (ex herpes, chickenpox, infectious
mononucleosis)
The nucleocapsid of the virus is constructed according
to certain symmetrical patterns: Examples
1. rabies is helical (lone rods,with thir capsids as hollow
cylinders surrounding nucleic acids)
2. polio and head colds have icosahedral symmetry
meaning the capsid is composed of 20 faces, each
shaped as an equilateral triangle),
3. polyhedral viruses (adenovirus such as herpes) are
many sided)
• Projections from the envelope are known as spikes,
which sometimes help the virus attach to the host
cell exAIDs
•
Bacteriophases are viruses that multiply within
bacteria
• During viral replication, a virus induces a living host
cell to synthesize the essential components for the
synthesis of new viral particles.
Steps of viral replication include:
1. Attachment: virus adsorbs to a susceptible host cell
2. Penetration: of virus or viral genome in the cell.
3. Replication: protein capsid is stripped away from the genome, and
the genome is freed in the cell cytoplasm.
4. Assemble: Once the viral genomes and capsomeres have been
synthesized, they are assembled to form new virions. After the
assembly is complete, the virions are ready to be released into the
environment.
5. Release: of new viral particles (varies ex host cell may become
exhausted and release virions ,ift he host cell experiences death
then it is called a lytic cycle of reproduction
• Lysogenic cycle: certain viruses remain active within
their host cells for a long period without replicating. (
virus is called a temperate virus, or proviruse because
they do not bring death to host immediately)
• HOST RANGE:
• Refers to the spectrum of host cells in which a virus
can multiply
(animal virus, bacterial virus plant virus)
• A virus can only infect certain species in each range.
TAXONOMY OF VIRUSE:
• Classification of viruses is based on type of nucleic
acid, morphological class, size of capsid, and
number of capsomeres.
• Other considerations include: virus's susceptibility
to microbial control agents, immunological
properties, site of multiplication, and
method of transmission.
VIRAL MEASUREMENTS:
• Viruses are generally to small to be
seen under the light microscope, and
thus to determine their number in terms
of a detectable effect on a host cell,
virus infectious units are expressed per
volume of fluid.
ANTIVIRAL AGENTS:
• Antibiotics cannot be used to inactivate viruses
because viruses do not perform the biochemical
functions that antibiotics interfere with.
• However some drugs can interfere with viral
replication.
• Protection against viral disease can be rendered by
using a viral vaccine( composed of inactivated(
dead) or attenuated (weakened viruses)
ONCOGENY:
• A number of types of cancer are now known to be
caused by viruses.
• (oma suffix attached to affected tissue)
• Viruses capable of producing tumors are called
oncogenic viruses and include adenoviruses, herpes
viruses, pox viruses, and papovaviruses
FUNGI:
• Include several thousand species of eukaryotic,
spore bearing
organisms that obtain simple organic compounds by
absorption.
• They have no chlorophyll and reproduce by both
sexual and asexual means.
• The study of fungi is called mycology, and fungal
diseases are called mycoses.
• Together with bacteria, fungi are the major
decomposers of organic materials in the soil.
Two major groups of organisms make up
the fungi
1. filamentous fungi called mold
2. unicellular fungi called yeasts
STRUCTURE AND PHYSIOLOGY:
• There is considerable variation in the structure, and size
of fungi
• Molds consists of long, branching filaments of cells
called hyphae (the visible hyphae mat is called a
mycelium)
• Yeasts are microscopic unicellular fungi, that reproduce
asexually by budding.
• Some species of fungi have the ability to shift from yeast
form to the mold form and vice versa... these fungi are
called dimorphic.
• Many fungal pathogens exist in the body in the
yeast form but revert to the mold form in lab.
• Reproduction in yeasts usually involves spores.
• Asexual spores may also be formed within a
sac, in which case they are called
sporansiospores.
• Most fungi grow best where there is a rich
supply of organic matter, most being
saprophytic.
• Most fungi grow best at an acidic pH of about 5 and a
temperature of 25 C (room temp), however, pathogenic fungi
grow best at a temp of 37C (body temp)
• Fungi store glycogen for their energy needs and are aerobic, except
for the fermentation yeasts that grow in both aerobic and anaerobic
conditions.
• Asexual reproduction occurs in the fungi when spores form by
mitosis, and sexual reproduction allows for compatible nuclei to
unite within the mycelium and form sexual spores
CLASSIFICA TION OF FUNGI:
• Fungal spores are important in the identification of
the fungus, since the spores are unique in shape,
color and size.
1. Division Zygomycota: produce sexual spores known
as zygospores as well as asexual sprangiospores. Ex
Rhizopus found on fruits vegetables and breads
2. Division Ascomycota; form their sexual spores within a
sac called an ascus...and are called sac fungi EX
include powdery mildews and fungi that causes dutch
elm disease and Saccharomyces
(fermentation yeast)
3. Division Basidiomycota: are called basidiomycetes or
club fungi because a club shaped structure called a
basidium is formed after sexual reproduction.
 The spores are called basidiospores
 . The fruiting bodies are called basidiocarps.
 Ex of a basidiocarp is a mushroom.
 One of the organisms of meningitis is the basidiomycete

Cryptococcus neoformans and the mushroom Amanita
is poisonous to humans.
• 4. Division Deuteromycota: lack a known sexual cycle
of reproduction and are said to be imperfect.
• When its sexual cycle is discovered, a fungus from this
division is usually reclassified.
• EX athlete's foot, ringworms
• Slime mold: have characteristics of both molds and
protozoa.
• The amoeba stage is called the plasmodium, which has
many nucli.
• The amoeba stage ends when the plasmodium matures
or encounters a harsh environment
• Water molds: belong to the group known as
oomycetes.
• They resemble other fungi because they have branched
filaments and form spores. Certain water molds
parasitize fish.
FUNGAL DISEASES:
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3.
4.
Systemic mycoses: fungal infection deep within
body and affect many tissues and organs.
Subcutaneous mycoses are fungal infections beneath
the skin.
Cutaneous mycoses affect hair, nails, and skin
Superficial mycoses are localized on hair shafts and
superficial skin cells.
Opportunistic mycoses are caused by normal flora or
fungi that are not normally pathogenic...can infect any
tissue
UNICELLULAR ALGAE:
• Algae are eukaryotic organisms that have no roots, stems, or
leaves, but do have chlorophyll and carry out photosynthesis.
• They can be multicellular or unicellular.
• Unicellular algae occur most frequently in water, especially in
plankton.
• Reproduction in algae occurs in both asexual and sexual forms,
binary fission also takes place
• During sexual reproduction, algae form differentiated sex cells that
fuse to produce a diploid zvsote
•
• The zvgote develops into a sexual spore, which germinates under
favorable conditions.
DIVISIONS OF UNICELLULAR ALGAE:
• 5 divisions classified in the kingdom protista
1. Division Chlorophyta: possess green chlorophyll pigments and
carotenoids. Ex chlamydomonas
2. Division Charophyta: EX stoneworts, may be a source of
limestone,
cover the bottoms of ponds
3. Division Euslenophyta: Ex euglena, contain chlorophyll and
carotenoid pigments for photosynthesis and reproduce by binary
fission
4. Division Chrysophyta: Ex diatoms, brown and yellow-green algae.
Contain chlorophyll and a special carotenoid pigment called
fucoxanthins (golden-brown color)
5. Division Pyrrophvta: Ex dinoflagellates, contain chlorophyll,
carotenoid and xanthophylls pigments, cause red tides
PROTOZOA:
• Eukaryotic microorganisms, are heterotrophs and feed on bacteria
and paniculate organic material.
• Asexual reproduction is by fission, budding, sexual reproduction is
by conjugation.
• Most are aerobic, but a few anaerobic species can be found in
human or animal intestines.
• Vary is size and shape,
• Many alternate between a free-living vegetative form (trophozoite)
and a resting form (cyst) depending on environmental conditions
• main types of locomotor organelles:flagella, cilia, and pseudopodia.
•
CLASSIFICATION OF PROTOZOA:
1. Mastigophora: have 1 or more flagella, reproduction by
fission,
group members cause intestinal distress. Ex Giardia
lamblia,
Trypanosoma brucei (sleeping sickness), euglena is
also placed here.
2. Sarcodina: move by pseudopodia, but flagella may
be present in reproductive stage. Ex Entamoeba
histolytica ( amoebic dysentery)
3. Ciliophora: move by means of cilia, Ex paramecium
4. Apicomplexa: form spores at one stage in their life
cycle so are also known as Sporozoa. Ex
Pneumocvstis carinii (lethal pneumonia in AIDs),
malaria and toxoplasmosis are also classified here.
HELMINTHS:
• There are a number of parasitic animals that spend part or all other
their lives in humans.
• Most of these animals belong to 2 phyla, Platyhelminthes
(flatworms), and Aschelminthes (roundworms)...both commonly
referred to a helminthes.
• Helminths are multicellular eukaryotic heterotrophs generally
possessing digestive, circulatory, nervous, excretory, and
reproductive systems (hermaphroditic or dioecious).
• Parasitic helminthes must be highly specialized to live inside their
hosts.
Differences that distinguish Parasitic
Helminths from their free-living relatives:
1. They either lack a digestive system or have a
greatly simplified one.
2. Nervous system is reduced due to the lack of need
to search for food and respond to the environment
3. Locomotion is either reduced or completely absent
due to transfer from host to host
4. Reproductive system is often more complex, it
produces more fertilized eggs, by which a suitable
host is infected.
PLATYHELMINTHES:
Members are flattened form top to bottom, and
have an incomplete digestive system and only
one mouth.
Classification of Platvhelminthes:
1. Trematodes: (flukes) named according to the tissue of
the definitive host in which the adult live (ex lung fluke,
blood fluke)
a. Parasonimus westermanni (lung fluke) lives in the
bronchioles,grows to 12mm long and 6mm wide, eggs
usually coughed up,swallowed and excreted in feces
b. Clonorchis sinensis: (Chinese liver fluke) eating raw
or undercooked fish
c. Schistosoma: burrow through skin of human host and
entercirculatory system, usually found in certain
abdominal andpelvic veins.
Cestoda: (tapeworms) intestinal parasites,
composed of a head (scolex) with suckers, body
divided into segments(proglottids).
a) Taenia sasinata: (beef tapeworm) lives in
humans and can reach lengths up to 6 meters,
thefeces of an infected human contains
thousands of eggs.
b) Taenia pisiformis: dog tapeworm
c) Echinococcus granulosus: tiny tapeworm
found in the intestines of dogs, cats ,wolves and
foxes., humans sever as the intermediate host
and is a dead end for the parasite unless the
human is eaten by an animal
2.
ASCHELMINTHES: ( ROUNDWORMS)
• Aschelminthes are cylindrical in shape and tapered
at each end, have a complete digestive system,
consisting of a mouth, an intestine, and an anus,
• Most are dioecious, males being smaller than
females and having a hooked tail
• Parasites of humans belong only to the class
consisting of nematodes.
NEMATODES:
•
Nematode infections of humans can be divided into
two categories
a) Those in which the egg is infective
b) Those in which the larva is infective
Parasitic Nematodes include:
1. Ascaris lumbricoides: largest roundworm to infect
humans(intestines), reaches a length of up to 30cm.
 Is dioecious with male being smaller and having a
hooked tail.
 Diagnosis is made when adult worms are excreted with
feces
2. Enterobius vermicularis: adult pinworm, spends its
entire life in human host. Adult pinworms are found in
human intestines,females migrate to anus to deposit
eggs in perianal skin,
 Diagnosis is by using a Graham sticky tape method
(tape placed on perianal skin in such a way as to
expose sticky side to eggs and then tape is
microscopically examined for eggs.
3. Necator americanus: Hookworms, Adults live in small
intestines of humans, eggs excreted with feces, larvae
hatch and live in soil, they enter host by penetrating
host's skin...enter the blood or lymph vessels which
transport them to the lungs... where they are coughed
up and swallowed, transporting the larvae to the
intestines.
 Diagnosis is eggs in feces... name is derived from the
hooks located around the mouth that are used for
attachment and removing food from host tissue. Infect
humans in the larvae form.
• Trichinella spiralis: usually acquired by eating
encysted larvae in pork or bear meat. In the human
digestive tract, the larvae are freed from cyst, mature
and reproduce.
• The larvae enter lymph and blood vessels in the
intestines and migrate through out the body...they
encyst in muscles and other tissue where they
remain until ingestedby another host
ARTHROPODS AS VECTORS:
•
Those that carry disease-causing microorganisms
are called vectors.
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1.
2.
3.
4.
5.
> Representative classes of arthropods include: >
Arachnida: (8 legs) spiders, mites, ticks
Crustacea :(4 antennae) crabs, crayfish
Chilopoda: (2 legs per segment) centipedes
Diplopoda: (4 legs per segment) millipedes
Insecta (6 legs) bees, flies
TERMS:
• Definitive host: An organism that harbors the adult,
sexually mature form of a helminthic parasite
• Intermediate host: An organisms that harbors the
larvae stage of a helminthes