Bacteria

Microorganisms Microorganisms (microbe) are

very small organisms which are usually only visible through a microscope.

Some microbes are unicellular (one cell) while others are multicellular (more than one cell).

Microorganisms

Uni - Euglena

Multi - Mould

Bacteria Bacteria are unicellular microorganisms

typically a few micrometres in length.

They were first observed by Anton van Leeuwenhoek in 1676, using a single-lens microscope. He called them “Animalcules”.

Bacteria have a wide range of shapes, ranging from spheres to rods and spirals.

How Big are ... ?

Bacteria Types Cocci – spherical

bacteria.Streptococcus pyogenes

(causes strep throat).

Bacilli – rod shaped.Salmonella enterica

(causes typhoid fever).

Bacteria Shapes Vibrio – bent rods.Vibrio cholerae

(causes cholera).

Spirilla – Spiral shaped.Treponema pallidum

(causes syphillis).

Bacteria Shapes

Bacteria Structure Copy and Label the following

diagram…

Cilia

1

2

3

5

4

6

7

8

Bacteria Structure Capsule – A slimy outer shell that

gives protection.

Cell Wall – Provides structure and support.

Cell Membrane – Controlsmovement of materials inand out of the bacteria.

CapsuleCell Wall

Cell Membrane

Bacteria Structure Nuclear Material (DNA) – Controls all

cell processes which take place in the cytoplasm.

Bacteria Have No Nucleus!

Cytoplasm – The semi-fluid interior of the cell where chemical reactions occur.

Bacteria Structure Flagella – Tail-

like projection used to help the bacteria move around.

Reproduction Bacteria reproduce asexually by a

process known as Binary Fission.

The bacteria grow larger, the DNA replicates, then the cell splits in two.

In ideal conditions, bacteria can reproduce as often as every 20 minutes.

Binary Fission Each new bacterium is genetically

identical.

Binary Fission Video

Binary Fission A certain kind of

bacteria can reproduce every 20 minutes.

Complete the table on the right and plot the bacteria's growth against time on a line graph.

Time (min) No. Bacteria

0 120406080100120140160180

↓400

Binary Fission The rapid increase in numbers in the

steep part of the graph is called exponential growth.

Eventually the lack of food and build up of waste products will cause the number of bacteria to level off and even decrease.

Time (min)

No.

Bac

teria

Reproduction If conditions are inhospitable,

some bacteria can produce spores which can survive for years.

What conditionsare required for growth?

How Bacteria Feed Most bacteria are consumers,

meaning they feed off other organisms as they can not make their own food.

Bacteria fall into two main feeding groups:

ParasitesSaprophytes

How Bacteria Feed Parasite – an organism which lives

and feeds off other living organisms.

Saprophyte – an organism that feeds off dead material.

E.G. compost

How Bacteria Feed Bacteria feed by releasing digestive

enzymes which pass through the cell membrane and break food down outside the bacteria.

The broken down food then enters the bacteria.

This process is called extracellular digestion.

Extracellular Digestion