Micro-Organisms
1.3 Aspects of Biology
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Key Concepts
Structure and function of parts of bacteria, fungi and viruses
Extra-cellular digestion by bacteria and fungi
Aerobic and anaerobic respiration
Bacterial reproduction by binary fission
Viral reproduction
Excretion of toxins
Other life processes for bacteria, fungi and viruses
Culturing micro-organisms
Conditions for growth of micro-organisms – temperature, food, moisture, pH,
oxygen.
Disinfectants, antiseptics and antibiotics
Disease
Nutrient cycles – carbon and nitrogen
Food production
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Living, Non-living or Dead?
• Biology is the study of living things
• A living object is an object that caries out
life functions
• A non-living object is an object that has
not been alive
• A dead object is an object that was once
alive
Revision
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Functions of Living organisms
Biologists have decided that an object is living if it carries out the following 8 functions:
Movement: all or part of the living object can move
Respiration: living things obtain energy from food during respiration
Sense the environment: living things respond to changes in their environment
Circulation: living things circulate gases and other chemicals
Growth: living things grow
Reproduction: living things produce new offspring
Excretion: living things are able to get rid of waste products from their bodies
Nutrition: living things can make their own food or obtain it by eating other living or onceliving (dead) things.
Mrs C. Gren.
Revision
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Living or Non-Living?
fire
fish
virus
algae
jellyfish
coral
mould
bacteria
amoeba
crystals
yeast
fungus
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The three domains of Life
All living organisms are divided into three
domains based on their similarity.
The Archaea were the first type of living
organism found on Earth. They are all
unicellular, (single cell) prokaryote (simple
cells without a nucleus) organisms.
The Bacteria are also unicellular and
prokaryote.
The Eukaryotes are both unicellular and
multicellular. Their cells contain a nucleus
plus mitochondria. This domain contains
fungi, protisa, plants and animals.
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The Five Kingdoms of Life
The traditional
division of living
organisms.
There is much more
variety between the
Monera Kingdom
(divided into the
Bacteria and
Archaea Domains)
than there is
between the
remaining 4
kingdoms that make
up the Eukaryote
Domain.
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Plant Classification
Scientists
universally use
a classification
system
developed from
Linnaeus (1753)
to catergorise
every species of
living organism
so far
discovered.
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Animal Classification
Current classification systems have
developed from Linnaeus' original
work. However, modern
classification systems are much
more complicated having many
levels of hierarchical organization.
These systems are also taxonomic
(structural and physiological
connections between organisms),
phylogenic (classification based on
genetic connections between
organisms), and are structurally
based on Darwin's theory of
evolution.
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Micro-organisms
Living
Non-living
Fungi - Eukaryote
Viruses
Bacteria - Prokaryote
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Cell Types
“Animal”
“Plant”
“Bacteria”
“Virus”
enclosed by a
plasma
membrane and
containing a
membranebound nucleus
and organelles.
>small
vacuoles, no
chloroplasts,
no cell wall.
similar to the animal cell,
but
>does not have
centrioles, lysosomes,
cilia, or flagella (except
some photosynthetic
protists).
>It does have a rigid cell
wall, central vacuole,
plasmodesmata, and
chloroplasts.
Does not
have
nucleus or
organelles
(except
ribosomes).
Not considered
living or
consisting of cells
but contains
genetic material
(RNA/DNA)
similar to all other
living things.
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Cell Structure - Prokaryotes
Absence of nucleus
No organelles in
cytoplasm (except
ribosomes)
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Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
>lack cell nucleus
>DNA/RNA material stored in a
single loop in an area called the
nucleoid
>have no membrane bound
organelles.
>reproduce asexually by binary
fission
>have membrane bound
nucleus containing genetic
material
>DNA stored on Chromosomes
>has membrane bound
organelles (mitrochondria –
respiration, Chloroplasts –
photosynthesis)
>usually reproduce sexually by
meiosis
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Unicellular and Multicellular
Unicellular
Multicellular
>fully functioning (MRS C
GREN) independent cell unit
>can be grouped into colonies
(eg algae) but are still able to
separate and survive
>most kingdoms have
examples of unicellular
organism
>cells within an organism are specialised to
perform a life function (or part of one)
>single cells cannot live independently
>all cells co-ordinate into one organism to
collectively perform all the functions of life.
>generally Plant and Animal kingdoms are
multicellular
Human - Animal
Paramecium - Protist
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Micro-organisms
Micro-organisms (or microbes)
are very small organisms, which
are usually only visible with the
aid of a microscope. Sometimes
a colony of micro-organisms can
be seen with the naked eye.
Micro-organisms which have
single cells are unicellular.
Those made of many cells are
multicellular. Some have no
cells at all – viruses.
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Relative size of Micro-organisms
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Cell membrane
Ribosome
Mitochondria
Nucleus
Animal cell
0.1nm
1nm
10nm
100nm
1µm
10µm
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100µm
1mm
Leaf
Leaf cross-section
Plant Cell
DNA
Scale of size
10mm
Microscopes
Most cells are to small
to be clearly seen by
eye and require a
microscope to view.
Magnification: the
number of times the
image is enlarged
Resolution: the clarity
and ability to see detail
in the image
The branch of biology
relating to preparation
and viewing tissue
under a microscope is
known as Histology.
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Microscopes
arm - this attaches the eyepiece and body
tube to the base.
base - this supports the microscope.
body tube - the tube that supports the
eyepiece.
coarse focus adjustment - a knob that
makes large adjustments to the focus.
diaphragm - an adjustable opening under
the stage, allowing different amounts of
light onto the stage.
eyepiece - where you place your eye.
fine focus adjustment - a knob that
makes small adjustments to the focus (it is
often smaller than the coarse focus knob).
high-power objective - a large lens with
high magnifying power.
inclination joint - an adjustable joint that
lets the arm tilt at various angles.
low-power objective - a small lens with
low magnifying power.
mirror (or light source) - this directs light
upwards onto the slide.
revolving nosepiece - the rotating device
that holds the objectives (lenses).
stage - the platform on which a slide is
placed.
stage clips - metal clips that hold a slide
securely onto the stage.
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RULES FOR A
Biological drawing
1. Use unlined paper.
2. Draw in pencil.
3. Always print.
4. Leave at least a 5mm margin on all four sides of the paper.
5. Center the title and print it in capital letters.
6. Center the drawing on the page.
7. Never cross lines.
8. Never use the plural form of a work when pointing to a single object or part.
9. Do little or no erasing.
10. When using the scientific name of an organism in places other than the title,
remember that the genus or first part of a scientific name is always
capitalized. The species or second part of a scientific name is not.
FOR EXAMPLE:
Canis familiaris is the genus and species name for a dog.
In a
title it would be CANIS FAMILIARIS
11. Print your name and other information as specified by your teacher.
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Virus
Viruses are not plants, animals, or
bacteria. Viruses are not living organisms
because they are unable to carry out all of
the characteristics of living organisms
without invading a living cell and ‘hijacking’
it’s processes. Viruses do not posses cells
or cell components of their own.
They cannot synthesise proteins, because
they lack ribosomes. Viruses cannot
generate or store energy.
Because viruses can not survive without
cells, scientists predict that they originated
from rogue pieces of DNA/RNA strand.
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Examples of viruses
Rabies virus
Influenza virus
Bacteriophage virus
Viruses can take
numerous forms
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Virus Structure
Spikes
Protein Coat
Lipid layer
RNA/DNA strands
Example – HIV Virus
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Virus Structure
All viruses contain:
Spikes
Protein Coat
Lipid layer
RNA/DNA strands
Example – HIV Virus
>Nucleic acid, either
DNA or RNA (but not
both),
>a protein coat
(capsid), which
encases the nucleic
acid.
 Some viruses are
also enclosed by an
envelope of fat and
protein molecules.
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Function of Virus
Capsid - The capsid is the protein
Components
shell that encloses the nucleic acid;
The capsid has three functions:
1) it protects the nucleic acid from
digestion by enzymes,
2) contains special sites on its surface
that allow the virus to attach to a
host cell, and
3) provides proteins that enable the
virus to penetrate the host cell
membrane and, in some cases, to
inject the infectious nucleic acid into
the cell's cytoplasm.
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Function of Virus
Components
Nucleic Acid - Just as in cells, the
nucleic acid (DNA or RNA) of each
virus encodes the genetic
information for the synthesis
(creation) of all proteins. While the
double-stranded DNA is responsible
for this in prokaryotic and
eukaryotic cells, only a few groups
of viruses use DNA. Most viruses
have single-stranded RNA. The
genetic material can only make
protein when it is slotted into the
DNA of a host cell.
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Culturing Virus
Viruses will not grow on
agar (jelly made from
seaweed with nutrients)
because they cannot feed.
They need living cells to
reproduce in and are often
grown in fertile hen’s eggs.
The introduction of microorganisms onto agar or into
living cells is known as
inoculation.
It is to dangerous to grow
viruses in the school
laboratory as all viruses are
Pathogens (harmful to living
organisms).
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Reproduction of viruses
Absorption
Viruses can enter an organism through any
cavity or broken surface of an organism. Once
inside, they find a host cell to infect.
Entry
The Virus attaches to a specific cell type and
‘injects’ its genetic material.
Replication
The viruses genetic material joins into the cell
DNA and viral protein is made.
Assembly
Various pieces of viral protein are constructed
into individual viral particles (or virions).
Release
The newly created virions break through the cell wall
(killing it) and proceed to infect other cells.
Lysogenic Cycle
Extra
Once inside the host cell, some
viruses, such as herpes and HIV, do
not reproduce right away. Instead,
they mix their genetic instructions
into the host cell's genetic
instructions. When the host cell
reproduces, the viral genetic
instructions get copied into the host
cell's offspring. The host cells may
undergo many rounds of
reproduction, and then some
environmental or predetermined
genetic signal will stir the "sleeping"
viral instructions. The viral genetic
instructions will then take over the
host's machinery and make new
viruses as described above. This
cycle, called the lysogenic cycle, is
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shown in the figure above.
Targeted cells
The virus attaches to the target cell, usually
through specific protein-protein interactions
between capsid and cell surface receptors.
Only then can the genetic material be taken
into the host cell.
There are three requirements that must be met
to ensure successful infection of a virus:
1. sufficient virus must be present
2. the cells must be susceptible and permissive
(matching) to the virus,
3. and local defenses (immune system) must
be absent.
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Fungi
FUNGI ARE:
• Made of tangled threads called HYPHAE
• Parasites or decomposers
• Spread by spores
• Fuzzy- looking!
Fungi
Fungi can either be multicellular such
as mushrooms and mould or unicellular
such as yeast.
The Fungi have their own Kingdom but
share similarties with both plants – do
not move around, and animals – can not
make their own food.
Fungi are either parasitic – feeding off
live hosts or saprophytic – feeding off
dead organisms.
Fungi make up an important part of the
food chain as decomposers – breaking
down dead organic mater and returning
the nutrients so they are availible to
other organisms.
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Fungi Structure
Spores
Sporangium
Stalk
hyphae
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Fungi Structure (Multicellular)
>Spores, haploid (only half
the chromosomes) used for
reproduction – both asexual
(growing into an exact copy)
or sexual (when combining
with a spore from another
fungus)
>Sporangium or fruiting
body. The visible part of the
fungi that produces and
distributes the spores.
> Hyphae, the feeding
threads. A mat of hyphae is
called a mycelium. The
hyphae can also be involved
in sexual reproduction when
they come in contact with SJ Gaze
hyphae from another fungus.
Fungus Reproduction
• Can be ASEXUAL – by spreading spores
• Can be SEXUAL – where two hyphae touch
Fungi Reproduction
Fungi Asexual Reproduction
1.Special spore capsules or cases called sporangia develop and
produce the spores. These spores are haploid – they have only half the
number of chromosomes. They can be either + or – strains. (rather than
male or female).
2. Millions of spores are released to float in the air
3. When spores land on tissue they germinate, sending out hyphae that
rapidly branch and invade the new host.
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Fungi Sexual Reproduction
1. Fungi form a gamete producing
area called a Gametangia.
2. Gametangia from a + strain
and a – strain join – but still from
the same species of fungi.
3. The 2 gametes (haploid) fuse
to form a diploid zygote with a full
set of chromosomes.
4. The zygote grows to produce
spores (haploid)
5. This process allows the fungi to
produce variation amongst the
offspring
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Fungi Nutrition
Multicellular fungi are made
up of a mass of very fine
threads called hyphae, which
invade the tissue of the host
organism or dead matter.
Fungi feed like bacteria by
releasing digestive enzymes
onto food, then reabsorbing
the nutrients. This is called
extra-cellular digestion.
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Fungi Extra-cellular Digestion
Steps to feeding;
1. Enzymes are released from the hyphae.
2. The food material outside the hyphae is digested.
3. The food molecules are small enough to diffuse into the hyphae.
Fungal hypha
Enzymes secreted to
break up large
particles
Large food particle
Smaller food
particles
absorbed
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Fungi Respiration
This can be aerobic (with oxygen) or anaerobic (without oxygen).
Bread and wine yeasts respire anaerobically, producing carbon
dioxide and alcohol. This is important in wine making, brewing of
beer and rising of bread. The process is called fermentation.
Sugar
C6H12O6
alcohol
+
CH3CH2-OH
+
carbon dioxide
2CO2
(+ 2ATP)
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Fungi Excretion
Carbon dioxide and
alcohol (ethanol) are
waste products of yeasts.
Other fungi may produce
different waste products
including toxins.
Toxins excreted by fungi
that kill or stop the growth
of bacteria are known as
antibiotics.
Humans have made use
of the antibiotics produced
by fungi to fight harmful
bacteria in their bodies.
The most commonly used
antibiotic is produced by
the penicillin sp. of fungi.
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Helpful vs. Unhelpful Fungi
UNHELPFUL:
HELPFUL:
• Mould is a fungus that
is unhelpful when it
gets on food like bread
and spoils it
• However, humans eat some
moulds like the “blue” in blue
cheese!
• Yeast is a fungus that
is unhelpful to humans
when it causes
infections like “Thrush”
• However, yeast is useful in
fermentation to make beer,
wine and ginger beer and for
making bread rise
• Penicillin is a fungus
that looks really bad for
you
• However, Penicillin is an
important antibiotic medicine
HOW TO MAKE A CULTURE…
•
Collect a “swab” and petri dish
•
Wash your hands - to avoid contamination of plate
•
Swab area you have been asked to investigate
•
Lift up side of petri dish lid without taking it off - to avoid contamination
•
Swab agar hard enough to leave microbes on - take care not to tear agar
•
Close lid and tape sides of the petri dish - so you can still see your cultures
•
Write your name and place you swabbed in small writing on bottom of
dish - so you can still see your cultures
IDENTIFYING MICROBES
• Name: M. luteus (type of bacteria)
• How you identify it: bright yellow, shiny,
& smooth
• Name: Staphylococcus aureus (type of
bacteria)
• How you identify it: large & creamcolored
• Name: Streptococcus pyogenes (type
of bacteria)
• How you identify it: smaller than
staphylococcus & white
• Name: Corynebacteria (type of
bacteria)
• How you can identify it: dry and crinkly
• Name: Fungi
• How you can identify it: fuzzy
Bacteria
BACTERIA:
• Are microscopic
• Are made up of one cell
• Are round, long & thin, or spiral shaped
• Need food and warmth to grow
• Use enzymes to digest food
Unique features of Bacteria
Bacteria are sufficiently different to be classified within their
own domain, separate from the plants, fungi, protists and
animals. Bacteria have a vast variety of different lifestyles
and survival methods.
They have no mitochondria, the cell membrane is the site
of energy release.
The DNA is in a single loop rather than chromosomes
Outside the cell membrane is a cell wall and often a slime
capsule for protection
There may be a flagellum to help the bacterium move.
size – they are much smaller
All bacteria are prokaryotes – they have no nucleus
membrane, just an area that the DNA occupies
Bacteria cell
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Examples of Bacteria
Streptococcus pyogenes
These spherical bacteria
are common inhabitants
of the throat. Sometimes
they can cause strep
throat or even more
serious disease like
necrotizing fasciitis
(commonly called flesheating bacteria)
Bacteria Structure
Cell wall
Cell
membrane
flagellum
Slime capsule
cytoplasm
RNA/
DNA
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Nutrition
Bacteria may be parasitic (feeding off other organisms) or
saprophytic. Bacteria feed by extra-cellular digestion. They
secrete enzymes outside their cell membrane and cell wall.
The enzymes digest the food into small particles that can
be absorbed through the cell membrane. This is similar to
fungi feeding.
Respiration
Respiration is the process of obtaining energy by chemically
breaking down food, In animals and plants, oxygen is
needed to break down the food into carbon dioxide, water
and energy. This is called aerobic respiration. Most bacteria
respire aerobically, while others do not need oxygen (and
may even be killed by it). This type of respiration is called
anaerobic respiration.
Respiration
Respiration is the process of obtaining energy by chemically
breaking down food, In animals and plants, oxygen is
needed to break down the food into carbon dioxide, water
and energy. This is called aerobic respiration. Most bacteria
respire aerobically, while others do not need oxygen (and
may even be killed by it). This type of respiration is called
anaerobic respiration.
Anaerobic
respiration
Aerobic
respiration
harmful
useful
harmful
useful
>Gangrene - foulsmelling
discharge, dead
tissue, and gas
formation within
the tissue
>yoghurt
production
>production of
biogas
>waste
processing
>electricity
generation
>Food rotting –
sour milk
>Nitrogen fixing
bacteria
>Cheese
production
>GE insulin
production
Excretion
Bacteria excrete waste products. Sometimes these are
harmful and are known as toxins. A disease-causing
bacterium is called a pathogen.
Reproduction
• Happens when one bacteria cell reaches its maximum size
and divides into two identical cells
• This division is called BINARY FISSION
• Some bacteria can divide every fifteen minutes
Parent cell
DNA copied
Cell divides
Two
identical
new cells
are made
Conditions needed for bacterial growth
Bacteria need the following conditions for growth:
Energy – in the form of food
Moisture
Warmth – cooling bacteria reduces their growth rate, but
does not usually kill them. Refrigerators and freezers
preserve food by slowing down the growth of bacteria.
Oxygen – For aerobic bacteria only. Oxygen may kill
anaerobic bacteria.
pH – bacteria grow better under the right conditions of pH
(acidity or alkalinity). Bacteria grow well on the human skin,
as it is slightly acidic.
Nutrient recycling
Bacteria and fungi decompose (break down) dead plants
and animals into simpler materials that can be used by
plants. That is why bacteria and fungi are often referred to
as decomposers.
In the carbon cycle, micro-organisms break down dead
plants and animals, releasing carbon dioxide and water. The
carbon dioxide is absorbed by plants and used in
photosynthesis. Minerals present in the dead material return
to the soil.
In the nitrogen cycle, micro-organisms break down animal
and plant proteins into nitrate ions, which can be absorbed
directly by plants.
Nitrogen Cycle
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Carbon Cycle
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USING FUNGI TO...make wine & beer
• The microbe used in beer & wine making is a fungus
called YEAST
• The YEAST makes alcohol by anaerobic respiration or
FERMENTATION
GLUCOSE
+ OXYGEN
CARBON DIOXIDE + WATER
• In WINE-MAKING, the YEAST uses the SUGAR in the
fruit for FERMENTATION
• In BEER-MAKING, the YEAST uses the SUGAR in the
malted barley for FERMENTATION
Food Production
Micro-organisms play essential roles in the manufacture of
such foods as bread and cheese, and also in the brewing
and wine making industries.
USING BACTERIA TO…make yoghurt
YOGHURT IS MADE:
From milk that has had bacteria added to it
By BACTERIAL FERMENTATION
When bacteria feed on the Lactose (sugar) in the Milk and
makes LACTIC ACID and water
Stages in yoghurt production
STEP PROCESS
WHAT MICROBE DOES
1
Milk is pasteurised
This is to reduce the amount of
unhelpful bacteria in the milk
2
Milk is cooled and
bacteria are added
Two yoghurt-making bacteria are
added
3
Yoghurt is incubated
This is to encourage the bacteria to
grow and divide by binary fission
4
Flavour is added
The lactic acid made by the bacteria
gives the yoghurt its “tangy” taste…
just add fruit!
Yoghurt making
The milk is pasteurised for 10 minutes at 95°C. This kills the bacteria in
the milk. The milk is then homogenised to make sure none of the
parts of milk separate out. The milk is then cooled and kept in a
fermentation tank at 43°C. Yoghurt starter culture containing the two
bacteria, streptococci and lactobacilli is added. This is called
inoculation.
The mixture is incubated at this temperature for 4 to 6 hours. During
this time the bacteria grow, reproduce and use lactose sugar for
respiration. They excrete lactic acid as a waste product of their
respiration. The lactic acid changes the flavour of the yoghurt and
coagulates the proteins in the milk to form yoghurt.
When the amount of lactic acid in the yoghurt gets to 0.9% the tank is
cooled down to 22°C. Fruit and flavour may be then added then the
yoghurt is packaged. It is then cooled and stored in a fridge at 5°C.
storage at this temperature slow down the activity of any bacteria in
the yoghurt so it lasts longer.
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Complete the following table to describe the key steps in the yoghurt making process
Key step
Description of what happens in each step
Pasteurised
Homogenised
Inoculation
Incubated
Packaged
Stored
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Complete the following table to describe the key steps in the yoghurt making process
Key step
Description of what happens in each step
Pasteurised
10 minutes at 95°C, kills harmful bacteria already in the milk
Homogenised
Shaken up so milk doesn’t separate out in its parts (water,
cream, fat etc) Cooled and kept at 43°C
Inoculation
A starter culture of useful bacteria is added to the milk
Incubated
Kept warm at 43°C for 4 to 6 hours which is the ideal growing
conditions for the bacteria
Packaged
Cooled down to 22°C, fruit and flavour added and put into packs
for selling
Stored
Kept in a fridge at 5°C so bacteria does not grow any more and
the yoghurt lasts longer
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Stages in wine making
STEP PROCESS
WHAT MICROBE DOES
1
Grapes
crushed
Yeast on the grape skins is mixed in
with the juice of the fruit
2
Juice & skins
are left at
25oC.
Yeast on grape skins uses the sugar
in the fruit juice to make alcohol and
carbon dioxide gas - fermentation
3
Wine is stored
in barrels for
up to 18mths
Fermentation stops before the wine is
put in barrels so the microbe doesn’t
do anything in this step.
Infectious Diseases - Definitions
Disease – a pathological condition of body parts or tissues
characterized by an identifiable group of signs and
symptoms.
Infectious disease – disease caused by an infectious agent
such as a bacterium, virus, protozoan, or fungus that can
be passed on to others.
Infection – occurs when an infectious agent enters the body
and begins to reproduce; may or may not lead to disease.
Pathogen – an infectious agent that causes disease.
Host – an organism infected by another organism.
Virulence – the relative ability of an agent to cause rapid
and severe disease in a host.
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Transmission of Infectious Diseases
Agents that cause infectious diseases
can be transmitted in many ways.
Through the air
Through contaminated food or water
Through body fluids
By direct contact with contaminated
objects
By animal vectors such as insects,
birds, bats, etc.
Courtesy of VOA
Chinese students
wearing masks during a
SARS outbreak
Courtesy of CDC
Aedes aegypti mosquito
Known to transmit
Dengue fever
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Classification of Infectious Disease
By duration
Acute – develops and runs its course quickly.
Chronic – develops more slowly and is usually less severe, but may
persist for a long, indefinite period of time.
Latent – characterized by periods of no symptoms between
outbreaks of illness.
By location
Local – confined to a specific area of the body.
Systemic – a generalized illness that infects most of the body with
pathogens distributed widely in tissues.
By timing
Primary – initial infection in a previously healthy person.
Secondary – infection that occurs in a person weakened by a
primary infection.
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How Infectious Agents Cause Disease
Production of poisons, such as
toxins and enzymes, that
destroy cells and tissues.
Direct invasion and destruction
of host cells.
Triggering responses from the
host’s immune system
leading to disease signs and
symptoms.
Courtesy of CDC
Human
Immunodeficiency Virus.
HIV-1 virions can be seen
on surface of
lymphocytes.
Reducing the Spread of Infectious Diseases
• Vaccines
• Antimicrobial drugs
• Good personal hygiene and
sanitation
• Protection against mosquitoes
• Quarantine