Also, some microbes also lead a symbiotic type of lifestyle in most multicellular organisms. There's a community of beneficial microoraganims living in human intestines is called microflora.

Microorganisms are capable of producing many enzymes necessary for the building up and breaking down of organic compounds, bacteria are widely 'employed' by humans.

Bioremediation: is the use of living organisms for cleaning up oil spills and soil and water pollutants. Sewage treatment techniques are based on biofiltration of some toxic organic material by converting it into something that can be safely discharged into the environment. Bacteria that break down environmental pollutants are sometimes called biofilters.

Pharmaceutical: Microbes used for medicinal production. One of the most important groups of medicines, antibiotics, is produced by fungi and bacteria. The name antibiotics means 'against life'. It is appropriate, because they attack bacteria and other unicellular organisms that are pathogenic for humans. Most antibiotics used today were found originally in fungi. Fungi are saprophytes, meaning that they get their nourishment from dead animals or plant matter.  

Science: Bacteria can multiply and mutate easily, some of them are commonly used for scientific research in genetics and molecular biology. Bacteria and viruses also make good 'vehicles' for engineered genes that are inserted into the recipient's DNA.

http://www.skwirk.com/p-c_s-4_u-92_t-212_c-710/beneficial-microorganisms/nsw/beneficial-microorganisms/small-world-microbiology-/microorganisms-and-the-human-body

-Direct: Direct physical contact (body surface to body surface) between infected or colonized individuals and susceptible hosts. 

Examples:

Shaking hands; kissing; coitus; transmission

Common cold; sexually transmitted diseases; infections

Precautions: Hand hygiene; masks; condoms

-Indirect: Infectious agent deposited onto an object or surgery (fomite) and survives long enough to transfer to another person who subsequently touches the object.

Examples of transmission: Not washing your hands between patients; or contaminated instruments

Examples of infections: RSV; Norwalk; Rhinovirus; even influenza

Precautions: Sterilizing instruments; disinfect surfaces and toys in school

-Droplet: Is transmission through air. Droplets are relatively large and projected up to about one meter.

Example of transmission: Coughing; sneezing; or (in healthcare) during suctioning

Examples of infections: Menigococcus; pertussis; influenza; respiratory viruses.

Precautions: Masks; cover mouth; move school desks more than a meter apart; side-step all coughers!

Non-contact

-Airborne: Transmission through aerosols (airborne particles) that may contain organisms in droplet nuclei or in dusts. It can be spread through ventilation systems I hospitals, or doctor's offices.

Ex of infections: TB; Varicella; measles; smallpox; chickenpox (and maybe influenza).

Precautions: Masks; negative pressure rooms in hospitals.

-Vehicle: A single contaminated source spreads the infection (or poison) to multiple hosts. This can be a common source or a point source.

Ex of transmission: Point source: foodborne outbreak from an infected batch of food; most cases will typically cluster around the site (like a restaraunt

http://www.jhsph.edu/departments/epidemiology/tracks/infectious-disease-epidemiology/

http://www.ph.ucla.edu/epi/bioter/anthapha_def_a.html

Amebiasis