Microorganisms

Starter What do these foods have in common?

Interesting Facts Microbes first appeared on earth about 3.5 billion yrs ago, before any other organsim. (humans have only been around for less that a million years) Microbes are so tiny that a billion of them would fit on a 10 cent piece. There are more types of microbes than any other species on the earth, they make up 60% of all living matter. Microbes are ubiquitous (everywhere). There’s about 10 million bacteria on each of your feet.

Interesting Facts We have only known about microbes for about 350 years, when the first microscope was invented. Microbes were only linked to disease in the late 1800s.

Who are the Microbes? Bacteria Fungi Algae Protozoa Viruses

What are Microbes? Very small organisms you cannot see with the naked eye These organisms are unicellular – a single cell that carries out the processes of life. Some are harmful and cause disease by releasing toxins – pathogens Others can be beneficial – yoghurt, bread, compost Some feed on dead and decaying material - saprophytes

Bacteria They are very small, it length can range from They are everywhere over your skin , in the air and living inside you 1 1000 20 mm to

Bacterial Shapes

Bacterial Structure

Structures explained Most bacteria have a thick outer covering called the cell wall. Just within the cell wall is the cell membrane which allows substances to be transported in and out of the cell. Along the surface of the bacteria cell, you might encounter structures called pilus, whose job is to help the bacteria stick to surfaces. Bacteria might also need to move around in their environment, so they can have structures called flagella, which resemble tails. The watery interior of the cell is called cytoplasm, and it has the texture of jelly. Sprinkled throughout the cell are small roundish structures called ribosomes. Ribosomes make proteins for the cell. Every prokaryote cell has DNA floating within the cytoplasm, which usually looks like a twisted strand of spaghetti. DNA contains the instructions for the cell, basically it is the control centre.

Bacteria are Living Things M R S G E N

Reproduction

Bacterial Reproduction Remember, in ideal conditions, some bacteria can reproduce as often as once every 20 minutes. E.g. Time (Min) No of Bact 1 200 1024 40 4 240 4096 80 16 280 16 384 120 64 320 65 536 160 256 360 262 144

Graph of Bacterial Numbers Against Time Number of Bacteria Time (min)

Bacterial Growth

Bacterial Growth The rapid increase in numbers in the steep part of the graph is called exponential growth. This will not continue, eventually lack of food or space or a build-up of toxic waste products will cause the number of bacteria to level off and then decrease.

Conditions Needed for Bacterial Growth Energy Moisture Warmth Oxygen pH

Bacterial Spore Formation If conditions for bacterial growth are unsuitable, bacteria may secrete a thick spore wall and survive for years. If conditions become suitable, the spore wall will rupture and the bacteria will resume growth.

Bacterial Nutrition Most bacteria are consumers – they don’t make their own food. Parasitic Bacteria feed off living material. Saprophytic Bacteria live on dead plant or animal material.

Bacterial Nutrition Bacteria feed by producing enzymes, which pass through the cell membrane and break food down outside the bacteria. The broken-down food then enters the bacteria through the cell membrane. This is called extracellular digestion.

Bacterial Excretion Bacteria excrete waste products Sometimes these are harmful and are known as toxins.

Bacterial Respiration Respiration is the process of obtaining energy by chemically breaking down food. Most bacteria respire aerobically. Some bacteria respire anaerobically (some bacteria may be killed by oxygen)