What are Microbes/Microorganisms ?

Using a self-designed single-lens microscope, the Dutch merchant / amateur scientist Anton van Leeuwenhoek (1632-1723) first observed microorganisms, which he called “ANIMALCULES”

Microorganisms are microscopic organisms.   They can be either:

•  A single cell

•  Cell clusters

•  Multicellular, more complex organisms

Microorganisms belong to diverse groups - including:

•  Prokaryotes (Organisms whose cells lack a membrane-bound nucleus)

•Bacteria.  Single celled

• Archaea (Not considered pathogens or parasites)

•  Eukaryotes (Organisms whose cells contain a nucleus and other structures (organelles) enclosed within membranes)

•Protozoa.  e.g. Giarda lamblia, Amoeba proteus, Cryptosporidium spp.

•Fungi.  e.g. Candida Albicans

•Algae.  e.g. seaweed

•Microscopic plants (blue/green algae) contain chlorophyll, enabling them to make their own food from light and carbon dioxide; e.g. chlorella, spirulina;

•Micro-animals e.g. dust and spider mites, rotifers, planarians

Microbes live in all ecosystems (the biosphere) and perform many essential functions:

•  Decomposers

•  Fix Nitrogen - separate the nitrogen atoms in nitrogen gas, making them available for many life essential processes (E.g. in DNA and proteins)

•  Fermentation

•Convert sugars into alcohol in beer/wine

•Convert sugar into lactic acid - for food preservation (sauerkraut, yogurt), leavening (produces Carbon dioxide) or food pickling (producing acetic acid), or eliminating antinutrients

•   Natural body flora - keeps pathogenicmicrobes in balance

•   Biotechnology / Medicine - E.g. antibiotics

Some microorganisms can cause pathogenic disease

Pathogenic disease occurs when a germ/infectious agent, called a pathogen (i.e. Pathogenic Bacteria, Virus, Fungi/Yeast or protozoa) causes disease or illness to its host.   

-   Some bacteria which are a normal part of the body's flora, can become pathogenic.    if their numbers get out of control or they move to and multiply in an area where they are not supposed to be

-   Pathogens can infect the body by various transmission routes.    Affected by the widely varying length of survival of the microorganism outside of the body:

•  Droplet contact - coughing or sneezing on another person

•  Direct physical contact - touching an infected person, including sexual contact

•  Indirect contact - usually by touching contaminated soil or a contaminated surface

•  Airborne transmission - if the microorganism can remain in the air for long periods

•  Fecal-oral transmission - usually from contaminated food or water sources

•  Vector borne transmission - carried by insects or other animals

For more on the role of microbes in disease:

Bacteria

Viruses

Fungi

Protozoa