Transcript Micro-organisms

Micro-organisms
B1.8
Microbes
• Also called micro-organisms
• They are extremely numerous and
found in most environments.
• Most are harmless, some are
essential, some are harmful.
• They are very small, e.g. 0.5-0.8
microns (1000 microns= 1mm)
Microbes
• Bacteria and fungi
perform MRS C GREN
•Movement
•Growth
•Respiration
•Reproduction
•Sensitivity
•Excretion
•Circulation
•Nutrition
Microbes
• Pathogens: disease causing
micro-organisms.
• Contagious: a disease which is
easily passed from one person
to another
Microbes
• Most microbes are consumers i.e. they
feed on other organisms.
• Some are saprophytes (feed on dead
organisms) others are parasites (feed on
living organisms without killing them).
• The most common life form, e.g. 100
million per 1g soil.
• They occupy most habitats
Microbes
Microbes break down complex carbon
compounds to simpler ones They
release CO2 in respiration making it
available for plants to use in
photosynthesis. They also recycle
nitrogen compounds and phosphates.
Bacteria
• Bacteria consist of only a single cell, but don't let
their small size and seeming simplicity fool you.
They're an amazingly complex and fascinating
group of creatures. Bacteria have been found that
can live in temperatures above the boiling point
and in cold that would freeze your blood. They
"eat" everything from sugar and starch to sunlight,
sulfur and iron. There's even a species of bacteria—
Deinococcus radiodurans—that can withstand
blasts of radiation 1,000 times greater than would
kill a human being.
Bacteria
Where They're Found
• Bacteria live on or in just about every
material and environment on Earth from soil
to water to air, and from your house to
arctic ice to volcanic vents. Each square
centimetre of your skin averages about
100,000 bacteria. A single teaspoon of
topsoil contains more than a billion
(1,000,000,000) bacteria.
Microbes
•Main types are:
–Bacteria
–Fungi
–Viruses.
Bacteria
Bacteria
• Chromosome: carry the code for
making chemicals and structures
within the cell and to store
information for cell division.
• Capsule: a slimy protective layer
around bacteria
Bacteria
• Cell wall: Rigid structure found
outside the cell membrane for
protection and support
• Flagella: Provides movement
• Cell membrane: The outer
membrane of a cell, which separates it
from the environment. Also called a
plasma membrane
Bacteria
Controlling bacterial diseases has
caused the world population to
increase and has lengthened
human life span.
Bacterial diseases include tetanus,
meningitis, salmonella, TB and
whooping cough.
Bacteria
• Growth (reproduction) is by binary
fission i.e. splitting in two
• The number of bacteria will initially
increase exponentially.
Bacteria
Time (hours)
No of bacteria
0
1
2
Calculate the
number of
bacteria after 8
hours if one
spore replicates
every half hour.
1
4
8
2
16
32
3
64
128
4
256
512
5
1024
2048
6
4096
8192
7
16384
32768
8
65536
Time (hours)
No of bacteria
0
1
2
Calculate the
number of
bacteria after 8
hours if one
spore replicates
every half hour.
1
4
8
2
16
32
3
64
128
4
256
512
5
1024
2048
6
4096
8192
7
16384
32768
8
65536
Bacteria
70000
60000
50000
40000
30000
20000
10000
0
0
1
2
3
4
5
6
7
8
Bacteria
Bacteria feed by extra-cellular
digestion
1. Food
2.
3.
Secrete
is broken
absorbed
digestive
down
byenzymes
bacteria
Bacteria
FOOD
Bacteria
• The absorption of food into the
bacteria relies on diffusion.
• Diffusion: when particles move from
where there is a high
concentration (lots of them) to a
low concentration (few of them)
Most particles start here
More here now
Bacteria
Waste products diffuse out through
the membrane.
Some are toxic but others are
useful.
• Most bacteria are aerobic (need
O2), some are anaerobic (don’t
need O2).
Bacteria
• Factors that limit microbe growth
are:
–Not enough food
–Not enough oxygen
–Not enough space
–Too much toxic waste
produced
Bacteria
In adverse (harsh) conditions,
bacteria form protected spores
which can survive for many years
Uses of bacteria
Food production
• Cheese – bacteria curdles the
protein in milk causing it to solidify
and taste different
Uses of bacteria
Uses of bacteria
Food production
• Yoghurt – bacteria converts lactose
sugar in milk to lactic acid producing a
semi-solid with a different taste
Culturing
• Bacteria and fungi need a medium
to grow in or on. E.g. agar or
nutrient broth.
Culturing
• All media and equipment need to
be kept sterile often by autoclaving
– i.e. boiling under pressure.
Culturing
• Cultures are
incubated upsidedown at 20-30° C
to stop
condensation
forming and
dropping onto the
colonies.
Culturing
• Fuzzy colonies on agar are
fungi.
• Smooth, shiny colonies are
bacteria.
Culturing
Viruses cannot
be grown on
agar, they need
living cells e.g.
fertilised eggs.
Viruses
Viruses are:
• Very small
• Simple in structure
–protein coat surrounds & protects
the genetic material
–genetic material controls what the
virus can do
Viruses
Viruses
• Viruses are NOT alive, they
need living cells to reproduce.
Protein
Coat
Genetic
Material
Viruses
4. Viruses
1.
2.
3.
DNA material
copiedcopied
emerge
injected
by
from
cellby
cell
into
cellcell
destroying it in the process.
Host
Cell
Viruses
• Fighting off viruses is complicated
by:
–They mutate (change form) rapidly
–Each new form requires a new
antibody.
–They may invade the body faster
than new antibodies can be
produced.
Fungi
• Types:
–Yeasts: for bread and brewing.
–tiny one-celled fungi.
Fungi
–Moulds: have a fuzzy or furry
appearance and often grow on
old food.
Fungi
–Mushrooms
and
Toadstools
grow in soil.
Fungi
Structure has two main parts:
• Hyphae: threads that spread
through the food
• Sporangia: the part that makes
spores
Spores
Sporangia
Hyphae
Bread mould
Growing
medium
Feeding
Feed by extra-cellular
digestion.
Hyphae secrete digestive
enzymes and absorb
nutrients
Enzymes are chemicals
that speed up a
reaction (biological
catalysts).
Reproduction
Fungi make
microscopic cells
called spores which
have tough coats.
Millions of spores are
released into the air
Reproduction involving only
one parent is called asexual.
When two parents are
involved in making offspring
it is called sexual
reproduction.
• Like bacteria, fungal spores can
survive a very long time.
The Mummy’s Curse
• Several people have suggested that
illnesses associated with the ancient
Egyptian tombs may have a rational
explanation based in biology. Dr.
Ezzeddin Taha, of Cairo University,
examined the health records of museum
workers and noticed that many of them
had been exposed to Aspergillus niger,
a fungus that causes fever, fatigue and
rashes. He suggested that the fungus
might have been able to survive in the
tombs for thousands of years and then
was picked up by archaeologists when
they entered.
Outside the tomb of
King Tut shortly after it
was opened in 1922.
The Mummy’s Curse
• In 1999 a German microbiologist, Gotthard
Kramer, from the University of Leipzig,
analyzed 40 mummies and identified several
potentially dangerous mould spores on each.
Mould spores are tough and can survive
thousands of years even in a dark, dry tomb.
Although most are harmless, a few can be
toxic.
• Kramer thinks that when tombs were first
opened and fresh air gusted inside, these spores
could have been blown up into the air. "When
spores enter the body through the nose, mouth
or eye mucous membranes, " he adds, "they
can lead to organ failure or even death,
particularly in individuals with weakened
immune systems."
A statue of a Pharoah
looks silently on as
archaeologists disturb
sacred ruins.
Mummy’s Curse http://www.unmuseum.org/mummy.htm
• For this reason archaeologists now wear protective gear
(such as masks and gloves) when unwrapping a mummy,
something explorers from the days of Howard Carter and
Lord Carnarvon didn't do.
• So was the curse of the mummy a mould spore named
Aspergillus flavus or Cephalosporium? Or was it all media
hype? Or is there another explanation?
In this photo, Gregg Landry, an engineer
from the Boston firm iRobot, places a robot
inside the shaft of the Great Pyramid in
Cairo in October 2005. The new robot has
been designed by a university in Singapore
to climb the two narrow shafts which might
lead to an undiscovered burial chamber in
the pyramid of Cheops at Giza, on the
outskirts of Cairo.
Microbe invasion
• Pathogens enter the body
by air, contaminated food
or water, from insects,
contact, in body fluids.
• They enter through
body openings
including broken skin.
• Disease = a harmful
illness
Immunisation
• Vaccination = inject dead or weakened
pathogen for body to produce own
antibodies
• Catch disease and develop own antibodies
• Inject antibodies from another source
Antibiotics
• Produced naturally by fungi
• Kill bacteria
• Interfere with cell wall and
membrane processes so it
can’t carry out life processes
Antibiotic Resistance
Antibiotics kill most bacteria but
some few may survive and
produce offspring that are also
resistant to antibiotics.
This is made worse when people
don’t take antibiotics as directed.
Bacteria which are only slightly
resistant may survive.
Antibiotic Resistance
4. Antibiotics
1.
2.
3.
A
Bacteria
Resistant
randominvade
bacteria
mutation
wipe out
your
now
produces
allbody
but
multiply.
thea
slightly
new
bacterium
different bacteria
Life processes of microorganisms and their effects
Respiration – releases CO2
(wine, bread) and lactic acid
(yoghurt)
Reproduction – increases
numbers of microbes and so
allows small initial numbers to
change large amounts of food
Uses of fungi
Food production
• wine – fungus ferments sugar in
grapes producing alcohol and
carbon dioxide.
Uses of fungi
Food production
• bread – fungus ferments sugar
and starch in flour producing CO2
gas by respiration which causes
bread to rise
Food preservation
Food needs to be kept
Human bodies reaction to infection
• Temperature rises above 37°C
• Lymph nodes swell with increased
production of more WBC’s/lymphocytes,
phagocytes
Nutrient cycles
• Carbon
• Nitrogen
Nutrient cycling
• Plants absorb nutrients from the soil.
• Plants photosynthesise using light, water and
carbon dioxide to make glucose which is used
as food by plants.
• Animals eat plants and absorb the nutrients
and glucose.
Nutrient cycling
• When plants and animals die, or excrete, their
bodies still contain glucose and other
nutrients.
• Microorganisms break down (decompose)
dead organisms and release the nutrients
which can be reused by living organisms.
Nutrient cycling
• Nitrogen cycling also uses
bacteria in the soil to convert
nitrogen in the air into nitrogen in
the soil.
• Other bacteria convert nitrogen in
the soil into nitrogen in the air.
• Plants use soil nitrogen as a
nutrient.
Nutrient cycling
• Carbon dioxide is absorbed by plants
and used to make glucose and other
carbon-based products.
• These become carbon dioxide again
when the plant is burnt or the
products are used in cellular
respiration.
• Burning and respiration both make
carbon dioxide.
• Animals do respiration also.