Transcript notes - Bloomscool

Microbes
“Investigate biological ideas relating to interactions
between humans and microorganisms”
AS 90950 (Sci 1.11)
Internal
4 credits
Time: 6 weeks (or so)
MICROBE TYPES
Micro-organisms are also called microbes.
little
life forms
There are three main types of microbe:
Bacteria
Fungi
Viruses
Check out their comparative sizes...
If we were keeping pets….
What would this need?
-
If we were keeping pets….
What would these need?
-
GROWING MICROBES
Bacteria and fungi can be cultured (grown on an agar
plate).
Agar is a jelly made from seaweed that has nutrients
added so the microbes have plenty of food.
Swab
Petri dish
Nutrient agar
Plates can have microbes added very easily. Anything
that may have been contacted by microbes can be
used to inoculate (add microbes to) the plate.
We will do one control for the whole
class.
You may like to inoculate your plate from
more than one source. Keep track of
which is which:
3 4
2
1
BACTERIAL STRUCTURE
Bacteria are single celled organisms, and smaller than most
plant and animal cells. The are unique life forms as they have
no nucleus.
Like plants, bacteria have a cell wall
(lets them keep their shape).
They also have a cell membrane.
Inside is the cytoplasm.
This includes the genetic material,
which may be DNA or similar.
The cell may also have plasmids,
(extra bits of genetic information).
There is an outer slimy capsule,
(stops it drying out).
The flagellum (tail)helps propel
the wee fella about.
BACTERIAL REPRODUCTION
Bacteria use a process
called Binary Fission…
two bits
split
in which they replicate their
genetic information and
divide into 2 new cells.
Genetic
information is
copied
The cell begins
to divide
2 bacteria are
formed
This makes their growth in ideal conditions incredibly fast.
BACTERIAL FEEDING
Bacteria feed using a process called Extra-cellular
Digestion.
In this they secrete a digestive enzyme,
which digests the food particles,
and then they absorb the nutrients. Yummy!
secrete
Food
(substrate)
digest
absorb
COLONY GROWTH
They need anything any other pet needs...
Food (nutrition)
Warmth (NOT “heat” – heat kills)
Moisture
Space to grow
What difference does Temperature make?
From left to right the
incubation temperatures of
these three otherwise
identically treated samples
are:
4°C, 20°C, and 28°C.
Obviously bacteria need
warmth to reproduce best.
FUNGI
Fungi may be single celled, like yeast, or a complex
multi-cellular organism, such as a mushroom.
Yeast is a single cellular
fungus. It is used in
baking and brewing.
Bread mould is a multicellular fungus.
FUNGI FEEDING AND STRUCTURE
Spores
Structure:
It is made up of a Sporangium,
that produces spores (for
reproduction), and hyphae,
which grow (like roots) into the
substrate (food source).
Hyphae
secrete
digest
absorb
Sporangium
Hyphae
Substrate
Feeding:
Fungi feed by extra-cellular
digestion through their
hyphae (like bacteria).
VIRUSES
Viruses are tiny, non-cellular microbes.
They are always pathogens (disease causing), because
they harm other living things to reproduce.
Like all living things Bacteria and Fungi carry out MRS
GREN processes.
Viruses are not really living things at all. They can’t move
by themselves, they can't reproduce without other cells,
they don't respire, or excrete, or feed.
Structure:
Viruses are very simple. They have
genetic material (DNA or RNA)
enclosed in a protective protein
coat.
They may also have some apparatus
to help attach to host cells.
VIRUS REPRODUCTION
Viruses attach to a host
cell,
inject their genetic
information,
use host cell processes
to make more copies
until the cell bursts.
In doing so they
reproduce very rapidly,
and destroy many host
cells.
This is what causes us
disease.
Viruses are so small they can only be seen using a
Scanning Electron Microscope.
CONTROLLING MICROBES 1
Microbes can also be controlled (in foods) by using:
Heat (e.g. Pasteurising)
Drying (e.g. Freeze drying)
Keeping cold – fridge/freezer
Acid
Salt
Keeping microbes out
Experiment results:
Comparing the antibacterial
effect of:
1. CuSO4 solution
2. Acid
3. Base
4. NaCl solution
CONTROLLING MICROBES 2
Pathogens can be chemically controlled by using:
Disinfectants – strong, used on surfaces
Antiseptics – weaker, used on skin
Antibiotics – originally from microbes (e.g.
penicillin),
used internally
Experiment results:
Comparing the antibacterial
effect of (at 50% dilution):
1. Water
2. Pams
3. Pinoclean
4. Jeyes
MICROBE WAY OF LIFE
Bacteria and fungi are consumers.
This means that they feed on other things to gain their
nutrition.
They are either:
●
Saprophytes (FEED on dead things/waste) or
●
Parasites (FEED on living things – a host -)
●
A symbiotic microbe is one that lives in harmony
with its host (mutually beneficial).
Which are these?
E. coli, a bacteria naturally present in your gut, which
helps to digest some nutrients.
Fungi and bacteria in a compost heap break down the
organic material.
Thrush, a fungus that causes itching and discomfort.
RESPIRATION
Bacteria and fungi respire, like us, aerobically (with O2).
Glucose
+
O2
CO2
+ H 2O +
Energy
Unlike us, some microbes can also respire anaerobically
(without O2). Their toxins (waste products) are usually
more poisonous than aerobes.
Instead of making water, they may make acids, or maybe
ethanol.
Glucose
+
O2
CO2
+ H 2O
+
Energy
Ethanol (in yeast) or
Lactic acid (in bacteria
that make yoghurt) etc
HELPFUL MICROBES
Many bacteria and fungi do important jobs, such as
breaking down (decomposing) dead matter and waste,
and recycling the nutrients.
Bacteria are also important in digestion and food
production (yoghurt and cheese etc).
Fungi are used in brewing and fermentation and
medicines (penicillin).
Viruses are always harmful.
But they can be used for the biological control of
unwanted organisms (e.g. RCD), as well as having
potential medical value.
HARMFUL MICROBES
Many microbes are pathogens (cause disease).
Your body is a great place for microbes as it is warm, moist,
and there is plenty to eat.
If they flourish they cause disease. If a disease is
contagious the microbe can be transferred between people
or other animals such as mosquitoes, flies and rats.
The ways that bacteria and fungi cause disease are:
1.
Feeding directly on your cells, destroying them.
2.
Excreting (waste products) toxins that damage cells.
Microbes also cause harm by spoiling food.
DISEASES
Viruses are always pathogens.
Herpes
A tomato virus
Diseases
Bacteria
Fungi
Virus
Salmonella
Athletes foot
Chicken Pox
Tetanus
Ringworm
AIDS
Syphilis
Thrush
Colds
BODIES DEFENCES
Your body is adapted to fight diseases:
1. Physical barrier – skin. Orifaces are protected by
secretions: ear wax, mucous, lysosome (antiseptic) in
saliva, urine, tears (also salty).
2. Phagocytes – White Blood Cells that engulf and destroy
foreign bodies. Dead WBCs form pus.
3. Antibodies are formed to attach to specific antigens on
the surface of pathogens. The body can “remember” how
to make these so often will not get the same disease
twice. This is called immunity.
Artificial immunity can be created by putting a weakened
form of the disease into your body (vaccination), or by
putting in pre-prepared antibodies from another animal.
RESISTANCE
By natural selection, microbes can adapt to be unaffected
(resistant) to an antibiotic or antiseptic.
This is caused by microbes coming into contact with an
antimicrobial but without being killed by it. E.g. Underprescribed or under taken doses of antibiotics.
Resistance means that we are constantly having to develop
new antibiotics.