• Not all bacteria are dangerous.microscope image by christemo from Fotolia.com
  
  Microscopy-uk.org.uk states that, "Bacteria are all around us. They exist in the air, on our bodies, and on the surfaces that we touch." These bacteria have been studied, named and categorized by microbiologists. Medical professionals benefit from learning about common types of bacteria because understanding these microorganisms helps them to evaluate and remedy various bacterial infections.
  
  

Cocci

• Cocci bacteria are spherical in shape. Cocci bacteria can be identified as either gram positive or gram negative. Staphylococcus is a form of gram positive cocci that can infect humans. Staphylococcus infections affect different parts of the body, causing irritation of the skin or sometimes the eyes. Streptococcus is another form of gram positive cocci, which often causes throat infections. Neisseria meningitis and neisseria gonorrhea are forms of gram negative bacteria that cause meningitis (which affects the brain and spinal cord) and gonorrhea (a sexually transmitted infection).
  
  

Bacilli

• Bacilli are rod-shaped bacteria that can measure between 5 and 30 microns long. Bacilli may be either gram negative or gram positive. Corynebacterium diphtheriae is one type of gram positive bacilli. This type of bacteria is responsible for causing diphtheria, which affects the nose and throat. Another type of gram positive bacilli is Lactobacillus. Lactobacillus is a harmless bacteria found in the digestive system. Some gram negative bacilli are enterobacteria (responsible for several types of food poisoning) and haemophila influenzae (causing chest infections).
  
  

Spirochaetes

• Spirochaetes bacteria include vibrios bacteria, which are shaped like a curved rod, and treponema, which are spiral-shaped. Vibrios cholerae bacteria thrive in stagnant water and can cause cholera. Cholera is a common intestinal infection in impoverished areas. Treponema is frequently carried by ticks and causes Lyme disease, which sometimes results in paralysis if left untreated.
  
  

Other Types of Bacteria

• Other less common types of bacteria outlined by Typesofbacteria.co.uk are Rickettsia (causing typhus), and mycoplasma (causing pnumonia). Rickettsia can live only inside other living cells, and mycoplasma does not have a cell wall.