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* There are unknown risks if genetic engineering experiments escape into the wild ("We don't know").
* There are unknown risks if genetic engineering experiments escape into the wild ("We don't know").


'''Readers are encouraged to check out [http://www.macrovu.com/image/GMimg/infoMrlUnknwnsInGMv7.pdf "What we know--and what we don't know--about ecological risks of genetically engineered plants"] knowledge map on risk from [http://www.stanford.edu/~rhorn/ Robert Horn at Stanford].'''
'''Readers are encouraged to check out [http://www.macrovu.com/image/GMimg/infoMrlUnknwnsInGMv7.pdf "What we know--and what we don't know--about ecological risks of genetically engineered plants" as of 2001] knowledge map on risk from [http://www.stanford.edu/~rhorn/ Robert Horn at Stanford].'''
 
* ''If you have a more recent and easy-to-read summary of Risk than the paper from 2000/2001, then add it here.''


== Who is a "biohacker"? ==
== Who is a "biohacker"? ==

Revision as of 07:33, 3 October 2009

Intro    In The News    Educational    Equipment    Projects    Kits    Methods    DIYbio.org    DIYbio googlegroup    FriendFeed - DIYbio    http://c.statcounter.com/5195189/0/1a5d59b0/1/0.png

DIYbio FAQ v1.5: "The biohacker's FAQ"

This FAQ for DIYbio is actively maintained by it's editors, and by you! Edit your contributions directly or email updates to the DIYbio email list, diybio@googlegroups.com.
Major contributors (in alphabetical order):
The contents of this FAQ are copyright under the OpenWetWare Copyright policy (Creative Commons Attribution-ShareAlike 3.0 Unported). When quoting any content of this FAQ elsewhere, include a full hypertext link back to the main FAQ page.

DIYbio FAQ v1.3: "The biohacker's FAQ"

Please update this FAQ mercilessly with Q&A !


This Frequently Asked Questions document is for the DIYBio mailing list. This FAQ is now split into multiple topics for easier reading.


FAQ Revision History

  • 1.0 - copied on 4/7/2009 from heybryan.org...DIYbio_FAQ
  • 1.1 - some updates to clarify original version
  • 1.2 - new sections, reorg, + sections about DIY agar DOI:10.1007/BF00152620 --jcline@ieee.org
  • 1.3 - expand projects sections. Add Laboratory Basics section. --jcline@ieee.org


What is DIYbio, as an organization?

DIYbio is an organization that aims to help make biology a worthwhile pursuit for citizen scientists, amateur biologists, and DIY biological engineers who value openness and safety. This will require mechanisms for amateurs to increase their knowledge and skills, access to a community of experts, the development of a code of ethics, responsible oversight, and leadership on issues that are unique to doing biology outside of traditional professional settings.


DIYbio is a distributed community of amateur or professional biologists, industry professional or amateur engineers, biomedical engineers, life scientists, computer scientists, etc. Our activities range across a broad spectrum, from molecular naturalism (sequencing part of your own genome or bacterial populations) to biological engineering to building low-cost, open-source alternative lab equipment (Gel Box 2.0) to writing open source software for biology, to creating open source hardware systems and manufacturing.

<html> <div style="float:left;"><object width="560" height="315"><param name="allowfullscreen" value="true" /><param name="allowscriptaccess" value="always" /><param name="movie" value="http://vimeo.com/moogaloop.swf?clip_id=3454392&amp;server=vimeo.com&amp;show_title=1&amp;show_byline=1&amp;show_portrait=0&amp;color=00ADEF&amp;fullscreen=1" /><embed src="http://vimeo.com/moogaloop.swf?clip_id=3454392&amp;server=vimeo.com&amp;show_title=1&amp;show_byline=1&amp;show_portrait=0&amp;color=00ADEF&amp;fullscreen=1" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" width="560" height="315"></embed></object><br /><a href="http://vimeo.com/3454392">The DIYbio Community - Presented at Ignite Boston 5 (2009)</a> from <a href="http://vimeo.com/macowell">mac cowell</a> on <a href="http://vimeo.com">Vimeo</a>.<br /><br /></div> <object width="560" height="340" style="float:left;"><param name="movie" value="http://www.youtube.com/v/-IIWH6Hhcnc&hl=en&fs=1&rel=0"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/-IIWH6Hhcnc&hl=en&fs=1&rel=0" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="560" height="340"></embed></object> <div style="clear:both"> </div><br /> </html>


What is DIYbio's mission?

Are we moving to a future where everyone performs a little genetic engineering? Is genetic engineering safe? Are GMO's safe? Is genetic engineering safe for hackers or everyone to perform? Aren't there too many risks or unknowns?

Today, everyone performs a "little" computer use, whereas decades ago leaders in the computer field claimed regular people would never need a computer. Decades before that, leaders in the transportation field claimed regular people would never need a car or would never need high speed travel. Eventually these technologies became usable enough for everyone, and somewhat indispensable. Looking many decades ahead, genetic engineering will likely be a common place activity, as with any technology.

Regarding whether genetic engineering is safe for hackers or for everyone:

  • There are many unknowns in genetic engineering ("We don't know").
  • There are many more unknowns than we currently know are unknown ("We don't know what we don't know").
  • There are methods to contain genetic engineering experiments to a clean laboratory with only small amounts of risk ("We can reduce the possibility of problems during experimentation").
  • There are unknown risks if genetic engineering experiments escape into the wild ("We don't know").

Readers are encouraged to check out "What we know--and what we don't know--about ecological risks of genetically engineered plants" as of 2001 knowledge map on risk from Robert Horn at Stanford.

  • If you have a more recent and easy-to-read summary of Risk than the paper from 2000/2001, then add it here.

Who is a "biohacker"?

How can I find out more and contribute?

Many ways! Here's a brief overview:

So far, we mainly communicate through the mailing list. There is also a lower volume DIYbio announce mailing list, which occassionally has announcements that the community might be interested in. Also, there are groups for:

You're welcome to subscribe to the mailing lists- in fact, we encourage it.

There are other forums:

What are the Guidelines for Posting to the DIYBio mailing lists and/or Forums?

As the DIYBio mailing list membership grows, it is more important to follow good guidelines for easier readability within discussions.

Please:

  • Follow proper quoting rules:
 One should reply using the standard technique:

    User C. wrote:
    > User B. wrote:
    > > User A. wrote:
    > > > blablabla
    > > blubberblubber
    > laberlaber

For complete information see conventional netiquette.

    • When quoting another author, keep the attribution line ("On such-and-such-date, Jonathan Cline wrote:").
    • Delete portions of the paragraph which do not pertain to the new reply. This is known as "Trimming the post".
      • Replace deleted text with "[...]" if it changes the placement of words or sentences in a paragraph.
  • Trim all quoted text to be the minimum necessary to follow the discussion.
  • Add your message below any quoted text. This means "write your reply at the bottom".
    • Do not "top post". "Top posting" is when the reply is added above the quoted text. This is not as easy to read when there are many replies in a thread. For this reason, do not "top post", only add the reply at the bottom. Many mail programs have a setting to "reply at top" or "reply at bottom" -- always set it to "Reply at bottom" or manually perform this action yourself.
  • Change the 'Subject' of the email when the topic changes.


There are many other resources available to learn about netiquette:

Where can I see an archive of previous DIYbio discussions and questions?

Right over here.

Some of our favorites ("member picks") include discussions on ..


Is there a group in my area?

There's probably a group nearby- maybe at least somebody somewhat interested in getting together for lunch or maybe sitting down over a bench and doing serious experiments- at any rate, you can find out about those near you by checking out the map below or diybio.org/local.

<html> <iframe width="575" height="350" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="http://maps.google.com/maps/ms?ie=UTF8&amp;hl=en&amp;msa=0&amp;ll=42.358163,0.0&amp;z=1&amp;spn=0,0&amp;msid=117373025318808082442.00045fd549f07830e0465&amp;output=embed&amp;s=AARTsJqk9drOPzgJzPIckjwHnoC0bQwDAA"></iframe><br />

<a href="http://maps.google.com/maps/ms?ie=UTF8&amp;hl=en&amp;msa=0&amp;ll=42.358163,0.0&amp;z=2&amp;spn=0,0&amp;msid=117373025318808082442.00045fd549f07830e0465&amp;source=embed">View a larger map, or to add yourself or your group to the map.</a> You'll need to sign into your Google account in order to add a new point. Here's a <a href="http://skitch.com/jasonmorrison/bycdy/add-a-point.png-png-image-864x494-pixels-scaled-70">screenshot of how to add a new point on the map</a>. </html>

You may also be interested in other local science groups around the world:

Are there any videos from regional groups?

DIYbio-NYC: Shot glass DNA extraction

<html><div style="clear:both;"></div></html>

DIYbio-SF: Tito's food coloring electrophoresis

<html><div style="clear:both;"></div></html>

DIYbio-boston: diybio visits the fablab

<html><div style="clear:both;"></div></html>


Has DIYbio been in the news?

Yes.


What are some educational resources for DIYBio and Biology? What are all these terms and technologies DIYBio keeps discussing?

See DIYBio FAQ: Education & Resources


What equipment do I need to perform DIYBio-related projects?

See DIYBio FAQ: Equipment


What is open source hardware?

http://p2pfoundation.net/Open_source_hardware

"Open Source Hardware is hardware that keeps its designs available in a way similar to the open source in software." There is no defacto license for open source hardware yet. Some websites (like ponoko, thingiverse, unptnt) put hardware CAD files under a "Creative Commons" license. However, it's still unknown how this is likely to interface with the legal systems around the world (i.e., patents). And it's not necessarily true that putting something directly into the public domain is the best way to go either. So, the future is presently unclear- in terms of legal issues.

DIYbio has many big supporters of standardized packaging formats (like .tar.gz, .deb, .tar, .rpm, etc.) for automatic downloading of hardware components and instructions on how to build the components. There are some sites that almost implement this (but not quite) such as instructables, ponoko, thingiverse, odesigns, unptnt, etc.

'Slashdot discussions


Projects

What Projects has DIYBio completed? What projects are DIYBio contributors working on now? Who is working on what? Who do I contact to offer to collaborate on a project?

See DIYBio FAQ: Projects.

Please add your own project info to the DIYBio FAQ: Projects topic!


Appendix 1 - list of Synthetic Biology Companies

Appendix 2 - List of Equipment Suppliers

New Equipment

  • please expand this list

Surplus/Auction Equipment

Appendix 3 - Laboratory Basics

USING PHYSICAL AGENTS TO CONTROL MICROORGANISMS

This section is quoted from BIOL 230 MICROBIOLOGY LABORATORY MANUAL by Dr. G.E. Kaiser, Copyright © Gary E. Kaiser, Updated: March 4, 1999


A. INTRODUCTION TO THE CONTROL OF MICROORGANISMS

Control of microorganisms is essential in order to prevent the transmission of diseases and infection, stop decomposition and spoilage, and prevent unwanted microbial contamination.

Microorganisms are controlled by means of physical agents and chemical agents. Physical agents include such methods of control as high or low temperature, desiccation, osmotic pressure, radiation, and filtration. Control by chemical agents refers to the use of disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial chemicals.

Basic terms used in discussing the control of microorganisms include:

1. Sterilization Sterilization is the process of destroying all living organisms and viruses. A sterile object is one free of all life forms, including bacterial endospores, as well as viruses.

2. Disinfection Disinfection is the elimination of microorganisms from inanimate objects or surfaces.

3. Decontamination Decontamination is the treatment of an object or inanimate surface to make it safe to handle.\

3. Disinfectant A disinfectant is an agents used to disinfect inanimate objects but generally to toxic to use on human tissues.

4. Antiseptic An antiseptic is an agent that kills or inhibits growth of microbes but is safe to use on human tissue.

6. Sanitizer A sanitizer is an agent that reduces, but may not eliminate, microbial numbers to a safe level.

5. Antibiotic An antibiotic is a metabolic product produced by one microorganism that inhibits or kills other microorganisms.

6. Chemotherapeutic antimicrobial chemical Chemotherapeutic antimicrobial chemicals are synthetic chemicals that can be used therapeutically.

7. Cidal An agent that is cidal in action will kill microorganisms and viruses.

8. Static An agent that is static in action will inhibit the growth of microorganisms.

B. TEMPERATURE

Microorganisms have a minimum, an optimum, and a maximum temperature for growth. Temperatures below the minimum usually have a static action on microorganisms. They inhibit microbial growth by slowing down metabolism but do not necessarily kill the organism. Temperatures above the maximum usually have a cidal action, since they denature microbial enzymes and other proteins. Temperature is a very common and effective way of controlling microorganisms.

1. High Temperature

Vegetative microorganisms can generally be killed at temperatures from 50°C to 70°C with moist heat. Bacterial endospores, however, are very resistant to heat and extended exposure to much higher temperature is necessary for their destruction. High temperature may be applied as either moist heat or dry heat.

a. Moist heat

Moist heat is generally more effective than dry heat for killing microorganisms because of its ability to penetrate microbial cells. Moist heat kills microorganisms by denaturing their proteins (causes proteins and enzymes to lose their three-dimensional functional shape). It also may melt lipids in cytoplasmic membranes.

1. Autoclaving

Autoclaving employs steam under pressure. Water normally boils at 100°C; however, when put under pressure, water boils at a higher temperature. During autoclaving, the materials to be sterilized are placed under 15 pounds per square inch of pressure in a pressure-cooker type of apparatus. When placed under 15 pounds of pressure, the boiling point of water is raised to 121°C, a temperature sufficient to kill bacterial endospores.

The time the material is left in the autoclave varies with the nature and amount of material being sterilized. Given sufficient time (generally 15-45 minutes), autoclaving is cidal for both vegetative organisms and endospores, and is the most common method of sterilization for materials not damaged by heat.

2. Boiling water

Boiling water (100°C) will generally kill vegetative cells after about 10 minutes of exposure. However, certain viruses, such as the hepatitis viruses, may survive exposure to boiling water for up to 30 minutes, and endospores of certain Clostridium and Bacillus species may survive even hours of boiling.

b. Dry heat

Dry heat kills microorganisms through a process of protein oxidation rather than protein coagulation. Examples of dry heat include:

1. Hot air sterilization

Microbiological ovens employ very high dry temperatures: 171°C for 1 hour; 160°C for 2 hours or longer; or 121°C for 16 hours or longer depending on the volume. They are generally used only for sterilizing glassware, metal instruments, and other inert materials like oils and powders that are not damaged by excessive temperature.

2. Incineration

Incinerators are used to destroy disposable or expendable materials by burning. We also sterilize our inoculating loops by incineration.

c. Pasteurization

Pasteurization is the mild heating of milk and other materials to kill particular spoilage organisms or pathogens. It does not, however, kill all organisms. Milk is usually pasteurized by heating to 71.6°C for at least 15 seconds in the flash method or 62.9°C for 30 minutes in the holding method.

2. Low Temperature

Low temperature inhibits microbial growth by slowing down microbial metabolism. Examples include refrigeration and freezing. Refrigeration at 5°C slows the growth of microorganisms and keeps food fresh for a few days. Freezing at -10°C stops microbial growth, but generally does not kill microorganisms, and keeps food fresh for several months.


C. DESICCATION

Desiccation, or drying, generally has a static effect on microorganisms. Lack of water inhibits the action of microbial enzymes. Dehydrated and freeze-dried foods, for example, do not require refrigeration because the absence of water inhibits microbial growth.

D. OSMOTIC PRESSURE

Microorganisms, in their natural environments, are constantly faced with alterations in osmotic pressure. Water tends to flow through semipermeable membranes, such as the cytoplasmic membrane of microorganisms, towards the side with a higher concentration of dissolved materials (solute). In other words, water moves from greater water (lower solute) concentration to lesser water (greater solute) concentration.

When the concentration of dissolved materials or solute is higher inside the cell than it is outside, the cell is said to be in a hypotonic environment and water will flow into the cell (Fig. 1). The rigid cell walls of bacteria and fungi, however, prevent bursting or plasmoptysis. If the concentration of solute is the same both inside and outside the cell, the cell is said to be in an isotonic environment (Fig. 2). Water flows equally in and out of the cell. Hypotonic and isotonic environments are not usually harmful to microorganisms. However, if the concentration of dissolved materials or solute is higher outside of the cell than inside, then the cell is in a hypertonic environment (Fig. 3). Under this condition, water flows out of the cell, resulting in shrinkage of the cytoplasmic membrane or plasmolysis. Under such conditions, the cell becomes dehydrated and its growth is inhibited.

The canning of jams or preserves with a high sugar concentration inhibits bacterial growth through hypertonicity. The same effect is obtained by salt-curing meats or placing foods in a salt brine. This static action of osmotic pressure thus prevents bacterial decomposition of the food. Molds, on the other hand, are more tolerant of hypertonicity. Foods, such as those mentioned above, tend to become overgrown with molds unless they are first sealed to exclude oxygen. (Molds are aerobic.)

E. RADIATION

1. Ultraviolet Radiation

The ultraviolet portion of the light spectrum includes all radiations with wavelengths from 100 nm to 400 nm. It has low wave-length and low energy. The microbicidal activity of ultraviolet (UV) light depends on the length of exposure: the longer the exposure the greater the cidal activity. It also depends on the wavelength of UV used. The most cidal wavelengths of UV light lie in the 260 nm - 270 nm range where it is absorbed by nucleic acid.

In terms of its mode of action, UV light is absorbed by microbial DNA and causes adjacent thymine bases on the same DNA strand to covalently bond together, forming what are called thymine-thymine dimers (see Fig. 4). As the DNA replicates, nucleotides do not complementary base pair with the thymine dimers and this terminates the replication of that DNA strand. However, most of the damage from UV radiation actually comes from the cell trying to repair the damage to the DNA by a process called SOS repair. In very heavily damaged DNA containing large numbers of thymine dimers, a process called SOS repair is activated as kind of a last ditch effort to repair the DNA. In this process, a gene product of the SOS system binds to DNA polymerase allowing it to synthesize new DNA across the damaged DNA. However, this altered DNA polymerase loses its proofreading ability resulting in the synthesis of DNA that itself now contains many misincorporated bases. In other words, UV radiation causes mutation and can lead to faulty protein synthesis. With sufficient mutation, bacterial metabolism is blocked and the organism dies. Agents such as UV radiation that cause high rates of mutation are called mutagens.

The effect of this inproper base pairing may be reversed to some extent by exposing the bacteria to strong visible light immediately after exposure to the UV light. The visible light activates an enzyme that breaks the bond that joins the thymine bases, thus enabling correct complementary base pairing to again take place. This process is called photoreactivation.

UV lights are frequently used to reduce the microbial populations in hospital operating rooms and sinks, aseptic filling rooms of pharmaceutical companies, in microbiological hoods, and in the processing equipment used by the food and dairy industries.

An important consideration when using UV light is that it has very poor penetrating power. Only microorganisms on the surface of a material that are exposed directly to the radiation are susceptible to destruction. UV light can also damage the eyes, cause burns, and cause mutation in cells of the skin.

2. Ionizing Radiation

Ionizing radiation, such as X-rays and gamma rays, has much more energy and penetrating power than ultraviolet radiation. It ionizes water and other molecules to form radicals (molecular fragments with unpaired electrons) that can disrupt DNA molecules and proteins. It is often used to sterilize pharmaceuticals and disposable medical supplies such as syringes, surgical gloves, catheters, sutures, and petri plates. It can also be used to retard spoilage in seafoods, meats, poultry, and fruits.


USING DISINFECTANTS ANTISEPTICS AND SANITIZERS TO CONTROL MICROORGANISMS

This section is quoted from BIOL 230 MICROBIOLOGY LABORATORY MANUAL by Dr. G.E. Kaiser, Copyright © Gary E. Kaiser, Updated: March 4, 1999


A. DISINFECTANTS, ANTISEPTICS, AND SANITIZERS

Disinfection is the elimination of microorganisms from inanimate objects or surfaces, whereas decontamination is the treatment of an object or inanimate surface to make it safe to handle.

a. The term disinfectant is used for an agent used to disinfect inanimate objects or surfaces but is generally to toxic to use on human tissues.

b. The term antiseptic refers to an agent that kills or inhibits growth of microbes but is safe to use on human tissue.

c. The term sanitizer describes an agent that reduces, but may not eliminate, microbial numbers to a safe level.

Because disinfectants and antiseptics often work slowly on some viruses - such as the hepatitis viruses, bacteria with an acid-fast cell wall such as Mycobacterium tuberculosis, and especially bacterial endospores, produced by the genus Bacillus and the genus Clostridium, they are usually unreliable for sterilization - the destruction of all life forms.

There are a number of factors which influence the antimicrobial action of disinfectants and antiseptics, including:

1. The concentration of the chemical agent.

2. The temperature at which the agent is being used. Generally, the lower the temperature, the longer it takes to disinfect or decontaminate.

3. The kinds of microorganisms present. Endospore producers such as Bacillus species, Clostridium species, and acid-fast bacteria like Mycobacterium tuberculosis are harder to eliminate.

4. The number of microorganisms present. The more microorganisms present, the harder it is to disinfect or decontaminate.

5. The nature of the material bearing the microorganisms. Organic material such as dirt and excreta interferes with some agents.

The best results are generally obtained when the initial microbial numbers are low and when the surface to be disinfected is clean and free of possible interfering substances.

There are 2 common antimicrobial modes of action for disinfectants, antiseptics, and sanitizers:

1. They may damage the lipids and/or proteins of the semipermeable cytoplasmic membrane of microorganisms resulting in leakage of cellular materials needed to sustain life.

2. They may denature microbial enzymes and other proteins, usually by disrupting the hydrogen and disulfide bonds that give the protein its three-dimensional functional shape. This blocks metabolism.

A large number of such chemical agents are in common use. Some of the more common groups are listed below:

1. Phenol and phenol derivatives

Phenol (5-10%) was the first disinfectant commonly used. However, because of its toxicity and odor, phenol derivatives are now generally used. These include orthophenylphenol, hexachlorophene, triclosan, hexylresorcinol, and chlorhexidine. Orthophenylphenol is the agent in Lysol®, O-syl®, Staphene®, and Amphyl®. Hexachlorophene in a 3% solution is combined with detergent and is found in PhisoHex®. Triclosan is a chlorine-containing phenolic antiseptic very common in antimicrobial soaps and other products. Hexylresorcinol is in throat lozenges and ST-37. A 4% solution of chlorhexidine in isopropyl alcohol and combined with detergent (Hibiclens® and Hibitane®) is a common handwashing agent and surgical handscrub. These agents kill most bacteria, most fungi, and some viruses, but are usually ineffective against endospores. They alter membrane permeability and denature proteins.

2. Soaps and detergents

Soaps are only mildly microbicidal. Their use aids in the mechanical removal of microorganisms by breaking up the oily film on the skin (emulsification) and reducing the surface tension of water so it spreads and penetrates more readily. Some cosmetic soaps contain added antiseptics to increase antimicrobial activity.

Detergents may be anionic or cationic. Anionic (negatively charged) detergents, such as laundry powders, mechanically remove microorganisms and other materials but are not very microbicidal. Cationic (positively charged) detergents alter membrane permeability and denature proteins. They are effective against many vegetative bacteria, some fungi, and some viruses. However, bacterial endospores and certain bacteria such as Mycobacterium tuberculosis and Pseudomonas species are usually resistant. They are also inactivated by soaps and organic materials like excreta. Cationic detergents include the quaternary ammonium compounds such as benzalkonium chloride, zephiran, diaprene, roccal, ceepryn, and phemerol.

3. Alcohols

70% solutions of ethyl or isopropyl alcohol are effective in killing vegetative bacteria, enveloped viruses, and fungi. However, they are usually ineffective against endospores and non-enveloped viruses. Once they evaporate, their cidal activity will cease. Alcohols denature membranes and are often combined with other disinfectants, such as iodine, mercurials, and cationic detergents for increased effectiveness.

4. Acids and alkalies

Acids and alkalies alter membrane permeability and denature proteins and other molecules. Salts of organic acids, such as calcium propionate, potassium sorbate, and methylparaben, are commonly used as food preservatives. Undecylenic acid (Desenex®) is used for dermatophyte infections of the skin. An example of an alkali is lye (sodium hydroxide).

5. Heavy metals

Heavy metals, such as mercury, silver, and copper, denature proteins. Mercury compounds (mercurochrome, metaphen, merthiolate) are only bacteriostatic and are not effective against endospores. Silver nitrate (1%) is sometimes put in the eyes of newborns to prevent gonococcal ophthalmia. Copper sulfate is used to combat fungal diseases of plants and is also a common algicide. Selinium sulfide kills fungi and their spores.

6. Chlorine

Chlorine gas reacts with water to form hypochlorite ions, which in turn denature microbial enzymes. Chlorine is used in the chlorination of drinking water, swimming pools, and sewage. Sodium hypochlorite is the active agent in household bleach. Calcium hypochlorite, sodium hypochlorite, and chloramines (chlorine plus ammonia) are used to sanitize glassware, eating utensils, dairy and food processing equipment, hemodialysis systems, and treating water supplies.

7. Iodine and iodophores

Iodine also denatures microbial proteins. Iodine tincture contasns a 2% solution of iodine and sodium iodide in 70% alcohole. Aqueous iodine solutions containing 2% iodine and 2.4% sodium iodide are commonly used as a topical antiseptic. Iodophores are a combination of iodine and an inert polymers such as polyvinylpyrrolidone that reduces surface tension and slowly releases the iodine. Iodophores are less irritating than iodine and do not stain. They are generally effective against vegetative bacteria, Mycobacterium tuberculosis, fungi, some viruses, and some endospores. Examples include Wescodyne®, Ioprep®, Ioclide®, Betadine®, and Isodine®.

8. Aldehydes Aldehydes, such as formaldehyde and glutaraldehyde, denature microbial proteins. Formalin (37% aqueous solution of formaldehyde gas) is extremely active and kills most forms of microbial life. It is used in embalming, preserving biological specimens, and in preparing vaccines. Alkaline glutaraldehyde (Cidex®), acid glutaraldehyde (Sonacide®), and glutaraldehyde phenate solutions (Sporocidin®) kill vegetative bacteria in 10-30 minutes and endospores in about 4 hours. A 10 hour exposure to a 2% glutaraldehyde solution can be used for cold sterilization of materials.

9. Ethylene oxide gas

Ethylene oxide is one of the very few chemicals that can be relied upon for sterilization (after 4-12 hours exposure). Since it is explosive, it is usually mixed with inert gases such as freon or carbon dioxide. Gaseous chemosterilizers, using ethylene oxide, are commonly used to sterilize heat-sensitive items such as plastic syringes, petri plates, textiles, sutures, artificial heart valves, heart-lung machines, and mattresses. Ethylene oxide has very high penetrating power and denatures microbial proteins. Vapors are toxic to the skin, eyes, and mucous membranes and are also carcinogenic. Another gas that is used as a sterilant is chlorine dioxide which denatures proteins in vegetative bacteria, bacterial endospores, viruses, and fungi.


B. EVALUATION OF DISINFECTANTS, ANTISEPTICS, AND SANITIZERS

It is possible to evaluate disinfectants, antiseptics, and sanitizers using either in vitro or in vivo tests. An in vitro test is one done under artificial, controlled laboratory conditions. An in vivo test is one done under the actual conditions of normal use.


C. EFFECTIVENESS OF HAND WASHING

There are 2 categories of microorganisms, or flora, normally found on the hands. Resident flora are the normal flora of the skin. Transient flora are the microorganisms you pick up from what you have been handling. It is routine practice to wash the hands prior to and after examining a patient and to do a complete regimented surgical scrub prior to going into the operating room. This is done in order to remove the potentially harmful transient flora, reduce the number of resident flora, and disinfect the skin.

Actual sterilization of the hands is not possible since microorganisms live not only on the surface of the skin but also in deeper skin layers, in ducts of sweat glands, and around hair follicles. These normal flora are mainly nonpathogenic staphylococci (Lab 15) and diphtheroid bacilli.

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