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)

• Bacteria and fungi perform MRS C GREN

Microbes

•Movement

•Respiration

•Sensitivity

•Circulation

•Growth

•Reproduction

•Excretion

•Nutrition

•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.

Microbes

• 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.  

Bacteria

•Main types are:

–Bacteria

–Fungi

–Viruses.

Microbes

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

Bacteria

Calculate the number of

bacteria after 8 hours if one

spore replicates every half

hour.

Time (hours) No of bacteria

0 1

2

1 4

8

2 16

32

3 64

128

4 256

512

5 1024

2048

6 4096

8192

7 16384

32768

8 65536

Calculate the number of

bacteria after 8 hours if one

spore replicates every half

hour.

Time (hours) No of bacteria

0 1

2

1 4

8

2 16

32

3 64

128

4 256

512

5 1024

2048

6 4096

8192

7 16384

32768

8 65536

0

10000

20000

30000

40000

50000

60000

70000

0 1 2 3 4 5 6 7 8

Bacteria

Bacteria feed by extra-cellular digestion

Bacteria

1. Secrete digestive enzymes

FOOD

BacteriaBacteria

FOOD

2. Food is broken down3. Food absorbed by 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)

Bacteria

Most particles start here

More here now

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

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

Uses of bacteria

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 upside-down at 20-30° C to stop condensation forming and dropping onto the colonies.

• Fuzzy colonies on agar are fungi.

• Smooth, shiny colonies are bacteria.

Culturing

CulturingViruses cannot be grown on agar, they need living cells e.g. fertilised eggs.

VirusesViruses are:

• Very small

• Simple in structure–protein coat surrounds & protects

the genetic material

–genetic material controls what the virus can do

Viruses

• Viruses are NOT alive, they need living cells to reproduce.

Viruses

Protein Coat

Genetic Material

Viruses

Host Cell

1. DNA material injected into cell2. DNA material copied by cell3. Viruses copied by cell4. Viruses emerge from cell destroying it in the process.

• 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.

Viruses

• 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

Fungi

–Mushrooms and Toadstools grow in soil.

Structure has two main parts:

•Hyphae: threads that spread through the food

•Sporangia: the part that makes spores

Fungi

Spores

Sporangia

Hyphae

Growing mediumBread mould

FeedingFeed 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.

• 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.

Mummy’s Curse http://www.unmuseum.org/mummy.htm

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

• Produced naturally by fungi• Kill bacteria• Interfere with cell wall and

membrane processes so it can’t carry out life processes

Antibiotics

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

Antibiotic Resistance1. Bacteria invade your body2. A random mutation produces a slightly different bacteria3. Antibiotics wipe out all but the new bacterium4. Resistant bacteria now multiply.

Life processes of micro-organisms 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

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

Uses of fungi

Food needs to be kept

Food preservation

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

• 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.

Nutrient cycling