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[[Image:Bacterial cell.png|right|200px]]

[[Image:Bacterial cell.png|right|200px]]

'''Bacteria''' are single-celled microorganisms.  Modern [[pathology]] and [[medicine]] are based on the findings of [[Louis Pasteur]] that bacteria cause many ailments.  

'''Bacteria''' are single-celled microorganisms.  Modern [[pathology]] and [[medicine]] are based on the findings of [[Louis Pasteur]] and later [[Robert Koch]] and [[Charles Laveran]] that bacteria cause many ailments.

Bacterial [[disease]] was a source of fear for humankind for most of [[history]]. This fear was largely abated by the development of [[antibiotic]] drugs in the last half of the 1900s. The general impression was that most bacterial diseases could be cured, relatively quickly and easily. But bacteria [[evolution|evolve]] resistances to certain types of antibiotics, making their continued treatment in a recurrent infection difficult at times.<ref>[http://www.chemheritage.org/educationalservices/pharm/antibiot/readings/evolve.htm antibiot-readings]</ref> Bacterial disease is becoming a more serious medical problem, particularly in hospitals which tend to harbor a population of drug-resistant bacteria.

Bacterial [[disease]] was a source of fear for humankind for most of [[history]]. This fear was largely abated by the development of [[antibiotic]] drugs in the last half of the 1900s. The general impression was that most bacterial diseases could be cured, relatively quickly and easily. But bacteria gain resistance to certain types of antibiotics, making their continued treatment in a recurrent infection difficult at times.<ref>[http://www.chemheritage.org/educationalservices/pharm/antibiot/readings/evolve.htm antibiot-readings]</ref> However, this is not [[evolution]], since the bacteria do not change from one type to another, they only gain or lose a few genes involved in the antibiotic and no new information is created. Bacterial disease is becoming a more serious medical problem, particularly in hospitals which tend to harbor a population of drug-resistant bacteria.

Bacteria are tiny one-celled organisms present throughout the environment that require a microscope to be seen.  The vast majority of bacteria are not harmful to human beings. Many of them are normally found on or in the human body, and not only do not cause disease, but provide some benefit. For example, the human gut normally contain a complement of ''intestinal flora'' which assist digestion.

Bacteria are tiny one-celled organisms present throughout the environment that require a microscope to be seen.  The vast majority of bacteria are not harmful to human beings. Many of them are normally found on or in the human body, and not only do not cause disease, but provide some benefit. For example, the human gut normally contain a complement of ''intestinal flora'' which assist digestion.