Bacteria are microscope prokaryotic organisms (click here to learn about prokaryotes). They can live independent of a host, being autotrophs or heterotrophs and can replicate at a phenomenal pace through Binary fission. This is shown in the video to the right.

Bacteria are found throughout the world and inhabit some of the harshest environments on the earth.  

Although we think that bacteria are evil and cause nothing but disease, they actually play an important part in decomposition, nitrogen fixation and help us in every day life.

In fact we use bacteria to produce cheese

Bad bacteria will produce enzymes, waste products and toxins which can affect our cells, tissue and cellular processes.

Syphilis, typhoid, chlamydia, tetanus and pnemonia are all caused by bacteria.

The video to the right shows a dog who has been infected with tetanus.

Tetanus is caused by Clostridium tetani. A bacteria which produces a toxin that affects the Central Nervous System.

As you can see by the video, the toxin causes stiffness in the jaw and other muscles. Death will occur when the muscles associated with breathing contract and no longer allow ventilation.

Clostridium tetani is an obligate anaerobe, meaning it can’t grown in the presence of oxygen.

This is why the danger of developing tetanus usually arises in deep wounds.

Tetanus

Crown Gall

Crown Gall is a disease in plants caused by Agrobacterium tumefaciens.

This bacteria doesn't kill the plant cells, it actually causes plant cells to proliferate (divide rapidly). The bacteria produce Auxin (a plant hormone) causing nearby plant cells to multiply. This provides food and nutrients to the bacteria.

Eventually the cells become tumour cells, growing uncontrollably, providing lots of food for the pathogen.

Characteristics of bacteria

As you can see from the information above, there are many different types of bacteria.

Each species of bacteria have number of different physical and chemical features.

Scroll over each word to see the structural features.

We can analyse the chemistry and structure of a bacteria’s cell wall through a gram stain analysis.

Gram positive bacteria have a thick cell wall of peptidoglycans.

They are also generally more susceptible to penicillin.

Gram negative bacteria have a complex, multi layered cell wall with layers of peptidoglycans and an additional outer membrane layer. They are generally less susceptible to penicillin.