Bacteria

Bacteria are single celled microbes. The cell structure is simpler than that of other organisms as there is no nucleus or membrane bound organelles. Instead their control centre containing the genetic information is contained in a single loop of DNA. Some bacteria have an extra circle of genetic material called a plasmid. The plasmid often contains genes that give the bacterium some advantage over other bacteria. For example it may contain a gene that makes the bacterium resistant to a certain antibiotic.

When conditions are favourable such as the right temperature and nutrients are available, some bacteria likeEscherichia coli can divide every 20 minutes. This means that in just 7 hours one bacterium can generate 2,097,152 bacteria. After one more hour the number of bacteria will have risen to a colossal 16,777,216. That’s why we can quickly become ill when pathogenic microbes invade our bodies

Bacteria come in three main shapes:

• Spherical (like a ball) 
  
  These are usually the simplest ones. Bacteria shaped like this are called cocci (singular coccus).


• Rod shaped
  
  These are known as bacilli (singular bacillus).
  Some of the rod-shaped bacteria are curved; these are known asvibrio.


• Spiral
  
  These known are as spirilla (singular spirillus).
  If their coil is very tight they are known as spirochetes