Demonstrate understanding of biological ideas relating to micro-organism

Introduction to the topic and key words list

Microorganisms are very tiny one-celled organisms, viruses, fungi, and bacteria, and are found everywhere in the world. They are found in all living things, plants and animal. There are more microorganisms on and inside your body than there are cells that make up your entire body. Microorganisms can live in the air, on land, and in fresh or salt water environments. Some of them, pathogens, can be harmful and causes diseases, but there are some microorganisms that are needed for living things to survive.A good introduction to microbes and you.

Links to get started

Key Words List

  • A really good powerpoint that covers the topic link
  • No brain too smalls recap of the topic here
  • CELLS alive - A general microbes information website.
  • Microbes and food - Information and illustrations about a variety of microbes and their interactions with food, in producing food, spoiling it and causing food poisoning
  • Infectious diseases – Pathogens - Good overview with structures and functions of microbes and other info. Includes Bacteria, Fungi (yeast), Viruses; (skip Protozoa and Parasites); How pathogens are spread; How pathogens cause disease; Growth of pathogen populations. Has a quiz at the end.

Micro-organisms will be selected from: bacteria, fungi, and viruses.

Biological ideas relating to micro-organisms will be selected from: Excellent notes for this section can be found here

The structure of micro-organisms


image wikicommons

  • Bacterium typically occur in the following forms:
  • cocci (spherical)
  • bacillus (rod)
  • spirillum (spiral)

Bacteria are commonly rod shaped or spherical (cocci). An example of the structure of a bacillus (rod shaped) bacterium is shown on the right.

  • Nuclear material (DNA) - controls the cell's processes
  • Cytoplasm - fluids that hold the internal structure
  • Cell membrane - controls the movement of substances in and out of the cell
  • Cell wall - maintains the shape of the bacteria.
  • Some bacteria have the following additional parts:
  • capsule - a hard and rigid protective layer
  • slime layer - a soft and slimy layer
  • flagella (singular: flagellum) - helps with movement of the bacterium.

Many bacteria do not exist alone. They will exist in chains or groups – many individuals joined together.

Average prokaryote cell- en.svg

And Khan academy has another great video


Yeast - tiny, single celled fungi used in bread-making due the CO2 byproduct of respiration.

Mould - A fungi made of many threads. Grows on exposed food sources.

Mushrooms and Toadstools - a large fungi that grows in soil. It is composed of the following structures:

sporangium- part of a fungus that produces spores.

Spores - reproductive cells produced by a fungushyphae - fine root-like threads that break down and absorb food.

Structure of fungus.jpg


Viruses are extremely tiny and are much smaller than a bacterium cell. There are a variety of different types of viruses. In year 11, we will learn about the phage virus. This type of virus infects the E. Coli bacterium which is a usually harmless. The bacterium can be found in the lower intestine of animals.The phage virus composes of the following parts:

Genetic material (DNA or RNA) - controls the virus' processes.

Protein case - protects the virusTail fibre - a hollow tube which genetic material passes through during infection.

Sheath - irreversibly binds the virus onto the bacterium resulting in its contraction and the tail fibre being pushed into the bacterium.


Culturing of micro-organisms

website showing how this is done.

• Bacteria / Fungi need food / nutrients / moisture for growth which the agar plate provides. Viruses need living cells to reproduce / replicate them, and so cannot grow on an agar plate.

• Fungus is furry as they have sporangia (which grow upwards into the air) / hyphae (which grow on the surface of the agar)

• Bacteria colonies are shiny because they have no sporangia / have slime / shiny capsules.

Once on the agar, the conditions are ideal for the bacteria and fungi to grow. Both bacteria and fungi are able to use extracellular digestion to digest food by secreting enzymes from their cell walls. This gives them the energy needed to reproduce. Fungi look fuzzy as they have sporangia / hyphae above the agar and bacteria look smooth as they have a slime capsule. Fungi are able to release spores from these sporangia to reproduce. Because the plate was incubated at 25°C, the conditions for reproduction were ideal, and they were able to reproduce fast. Bacteria reproduce by binary fission by duplicating their DNA and pinching their cell wall to form two cells and as they had both nutrients and a warm environment they were able to reproduce to visible levels. Because viruses need living cells to reproduce / replicate them, they cannot grow on an agar plate.

Bacteria growth curves

information can be found here

life processes of micro-organisms

Life processes usually are covered by MRS GREN. I will cover for you these basically below.

Life processes of micro-organisms will be selected from:

  • the nutrition,
  • growth,
  • respiration,
  • reproduction,
  • excretion of bacteria and fungi
  • reproduction of viruses.


Extracellular digestion - Fungi/ Bacteria

Part - Hyphae - threads used for feeding, growth and spreading themselves.

1. Secrete enzymes, chemicals that speed up the breakdown of food into smaller particles (nutrients). This is done through the walls of their fine feeding hyphae.

2. Digest the food (outside the microbe)

3. Reabsorb the digested food through the hyphae walls.

The reabsorbed nutrients is used for growth and repair or used in respiration to release energy.

Fungi are saphrophytes which means they feed on dead material and they feed by extracellular digestion. They live in moist, warm, nutrition rich environments.

Growth (talking about the size of an organism)

Bacteria and Fungi both grow larger using nutrition gained by digesting food. They also make energy using respiration. Viruses do not grow as they have no chemical processes of their own.

Reproduction Bacteria

Bacteria reproduce by binary fission a form of asexual reproduction. In ideal conditions (eg warm, moist, plentiful food) a bacteria can divide in two every twenty minutes. This means that they are able to reproduce extremely rapidly, with each division doubling the number of bacteria.

Reproduction Fungi

Fungi generally reproduce by spore production, a form of asexual reproduction. In ideal conditions (similar to those listed above for bacteria) this mode of reproduction takes time, as it relies upon the formation of sporangia. However, each sporangium can release a huge number of spores.

Yeast is a type of fungi which can reproduce by budding. This is a form of asexual reproduction similar to binary fission, resulting in offspring with identical genetic material.

Once produced fungal spores can be carried by wind or water a distance from the original plant. In contrast, new bacteria will remain where they are produced.

Reproduction Virus

  1. How Viruses Infect Cells
  2. The basic process of viral infection and virus replication occurs in 6 main steps.
  3. Adsorption - virus binds to the host cell.
  4. Penetration - virus injects its genome into host cell.
  5. Viral Genome Replication - viral genome replicates using the host's cellular machinery.
  6. Assembly - viral components and enzymes are produced and begin to assemble.
  7. Maturation - viral components assemble and viruses fully develop.
  8. Release - newly produced viruses are expelled from the host cell.

Environmental factors that affect the life processes of micro-organisms.

Below section is from this link - click for the rest of it.

Environmental factors will be selected from:


Temperature: Bacteria can grow at all temperatures between the freezing point of water and the temperature at which protein or protoplasm (the fluid inside them) coagulates (turning into a not so runny liquid). Somewhere between these maximum and minimum points lies the optimum temperature at which the bacteria grow best.

Temperatures below the minimum stop bacterial growth but do not kill the organism. However, if the temperature is raised above the maximum, bacteria are soon killed. Most cells die after exposure to heat treatments in the order of 70°C for 15 seconds, although spore-forming organisms require more severe heat treatment, e.g. live steam at 120°C for 30 minutes.

Bacteria can be classified according to temperature preference: Psycrophilic bacteria grow at temperatures below 16°C, mesophilic bacteria grow best at temperatures between 16 and 40°C, and thermophilic bacteria grow best at temperatures above 40°

oxygen availability

Oxygen is used by aerobic bacteria during the process of cellular respiration as a final electron acceptor. For aerobic organisms, oxygen is an absolute requirement for their energy-yielding properties. Certain microorganisms grow in oxygen-free environments and are described as anaerobic. Organisms such as these produce odoriferous gases in their metabolism, including hydrogen sulfide gas and methane. Certain pathogenic species, such as Clostridium species, are anaerobic.


Bacteria need nutrients for their growth and some need more nutrients than others. Lactobacilli live in milk and have lost their ability to synthesise many compounds, while Pseudomonas can synthesise nutrients from very basic ingredients.

Bacteria normally feed on organic matter; as well as material for cell formation organic matter also contains the necessary energy. Such matter must be soluble in water and of low molecular weight to be able to pass through the cell membrane. Bacteria therefore need water to transport nutrients into the cell.

If the nutrient material is not sufficiently broken down, the micro-organism can produce enzymes (chemicals) which split the nutrients into smaller, simpler components so they can enter the cell. Inside the cell the nutrients are broken down further by other enzymes, releasing energy which is used by the cell.


Bacteria cannot grow without water. Many bacteria are quickly killed by dry conditions whereas others can tolerate dry conditions for months; bacterial spores can survive dry conditions for years.


(including pH, toxins, antibiotics, disinfectants)


disinfectants are chemicals that kill/ eliminate/ destroy/ inhibit growth of harmful/ pathogenic micro-organisms/ bacteria, reducing the chance of infection through food/ contamination/ or areas that present a high risk of infection (eg, plates, chopping boards, kitchen areas, door handles, etc.).


The effects of environmental factors on the life processes

nutrient cycling and role in ecosystems

  • Decay – bacteria and fungi - How decomposers decay things, and how it can be prevented to preserve foods. Info and a Test Bite
  • Biological compounds activity - Interactive animation on the carbon, oxygen and nitrogen cycles (after an overview of what is in the organic molecules of proteins, carbohydrates and fats). Supported by the text revision and test here.

Fungi break down/ feed on dead organic matter/ wastes containing carbon/ nitrogen/ amino acids/proteins.

When they respire/ excrete they release carbon dioxide into the atmosphere.

The CO2 can be absorbed by plants (to do photosynthesis).

The fungi help to convert the nitrogen in amino acids/ proteins into ammonia/nitrates. These nutrients can then be absorbed by plants from the soil (as nutrients).

Food production and preservation

  • High food temperatures kill bacteria.
  • Heating the can sterilises it / removes bacteria / enzymes in bacteria denatured / destroyed.
  • Sterilising kills bacteria / prevents introduction of MOs.
  • No air so no bacterial growth.
  • Sealing the can prevents MOs entering.
  • Removal of air removes oxygen or source of bacteria. Refrigerating food affects a named MO life process / slows micro-organisms growth / respiration / reproduction.
  • High food temperatures kill MOs so they cannot respire or reproduce, which means the food will not spoil unless opened / will be safe for consumption.

Sewage treatment

• Sewage treatment reduces the spread of disease / prevents destruction of waterways by raw sewage / reduces the smell of raw sewage / sewage contains lots of bacteria.

• sewage treatment is important as it helps to recycle nutrients / water

• An aeration tank contains high level of oxygen (DO NOT accept air).

• Aerobic bacteria survive / reproduce / feed in the aeration tanks.

• The sewage that enters the aeration tank contains organic waste / faeces etc.

• The products of the treatment are carbon dioxide and water. (Some sludge is also produced for further processing.)

• Air is needed to oxygenate the tank / bacteria need the oxygen to survive / respire.

• The bacteria carry out out aerobic respiration as they feed on the contents.

• Bacteria breakdown / decompose the solid / organic waste.

Human faeces contain large quantities of bacteria. Preventing these from entering drinking water and food reduces the risk of infection spreading / as naturally occurring bacteria break down waste in waterways, they use large amounts of dissolved oxygen, making the water anaerobic / killing the fish / plants.

• As the bacteria feed on the organic material in the tank, they carry out aerobic respiration. This produces carbon dioxide and water as waste products. The air entering the tank helps maintain a high level of oxygen. If the oxygen levels fell, the bacteria would not be able to use aerobic respiration / respiration would become anaerobic.

• As the bacteria feed on the organic material in the tank, they carry out aerobic respiration. This produces carbon dioxide and water as waste products. Without air / oxygen being pumped into the tank, the bacteria are unable to carry out aerobic respiration, and instead their respiration becomes anaerobic. For this reason the aeration tank has air pumped in to it. If conditions in the tanks remain highly oxygenated, the aerobic bacteria are in the best conditions for them to feed and reproduce. This means that the tank will continue to function as it should and the bacteria will continue to convert the organic waste to carbon dioxide and water. If the conditions change, and the tank loses its oxygen supply, anaerobic bacteria / respiration will take over as the aerobic bacteria will not be able to survive. This will result in the tank becoming smelly, and the production of methane.

Food poisoning

Whats a pathogen?

diseases – Pathogens

Campylobacter bacteria cause food poisoning when people eat infected food such as chicken. The bacteria then multiply rapidly in the digestive system causing the poisoning symptoms.

Freezing food means that the bacteria are dormant/ not reproducing. Refrigeration slows the rate of reproduction of bacteria. In comparison, keeping food on the bench leads to faster reproduction as this is near the optimal temperature for bacterial reproduction. Therefore freezing/ refrigeration is more likely to reduced the risk of food poisoning High temperatures kill bacteria. If chicken is not thoroughly cooked in middle it will not be hot enough to kill all bacterial spores, and this may lead to food poisoning.

disease in plants

microbial attack on everyday materials (helpful and harmful)


Infectious diseases and their treatment - This interactive e-source about how the body copes with disease allows you to complete summary sheets to check you progress as you go.

Resistance to antibiotics and genetic mutation

Variation/ mutations can occur in bacterial populations which may mean that some strains are not affected by a particular antibiotic.

Failing to take a full course of antibiotics means that the more resistant bacteria manage to survive.

The resistance is passed on to subsequent generations. Those resistant bacteria become more numerous, so eventually that antibiotic will no longer work.

Taking antibiotics correctly would result in pathogens being killed by the initial treatment.

Extra links (thanks bioticfactor)

Fighting back - An interactive animation in which you, playing the role of the immune system, try to figure out how to overcome and infection of the mumps. Also details why AIDS is so devastating.

How Herd Immunity Works - Why it is important for everyone who can to be vaccinated. A 10 minute video.

Making vaccines - An interactive where you follow the instructions to make 6 different types of vaccines.