The Law Of Unintended Consequences

So yesterday’s post introduced the law of unintended consequences. Hopefully, this wasn’t the first time you’d heard of this idea, but just in case it was, let’s define what is meant: The law of unintended consequences is that every action has consequences. Imagine this as ripples in a pond when a rock is dropped in: rock creates the first splash, but that splash then ripples outward and the ripples can have impacts themselves, separate from the initial impact of the rock into the water. It’s worth noting that unintended consequences may not be unwanted consequences; sometimes, the ripple effect turns out to be exactly what you want. However, if you experimental design goes wrong, you can probably guarantee that the cause was one of these ripple effects gone wrong. Let’s start by looking at a simple example: you’re sitting in a boat on a lake. You’ve got a full glass of an icy cold beverage. You pluck out one of the ice cubes and decide to toss it into the lake. It makes a nice splash, and you see it ripple outwards. You decide to try this again, but with a bigger chunk of ice. You set your very full glass of icy cold beverage down and reach into the cooler, fishing out an enormous chunk of unbroken ice. You toss this overboard with a decent amount of force. You get the same satisfying splash, but this time, the ripples are substantial enough that they rock your boat. This is enough to spill your icy cold beverage. As you sit back down, your pants get wet in the spilled icy beverage. Jumping up in alarm, you rock the boat further, and as this is actually just a little boat, it’s enough to overturn the boat. You’ve now fallen into the water, along with your cooler, your icy beverage, and everything else you had on the boat. Fortunately, you were in relatively shallow water, so you’re able to get to your feet and keep your head above water. You can right your boat and then begin to find all the things you spilled, putting them back into the boat, but you really don’t know if you can get back into the boat yourself without overturning it again.

Tossing the ice and seeing the ripples are the intended consequences. Everything else is unintended consequences, from the spilled drink, to the wet pants, the upended boat, the spilled contents. In an experiment, this long list of extra effects from ripples is an indication of the things that can go wrong unless you think things through in advance.

So, what might this look like in your lab? Let’s imagine you’re looking for the minimum bactericidal concentration of an antibiotic against a strain of E. coli that you suspect may have developed resistance to multiple antibiotics. You want to be certain that the drug of choice will be effective against the bacteria, so doing the MBC test correctly is important.

I haven’t discussed the how-to on doing an MBC before; I’ll be doing an entry on that later. For the moment, we’ll assume you know how: you culture your sample to ensure you have enough to do your test, do an isolation plate to make sure you test only the bacteria of interest, reculture that bacteria, do a count in the microscope to determine the concentration, then inoculate a series of broths made with the antibiotic of interest. Incubate for 24 hours, take the tubes without growth, and inoculate plates without any antibiotics. Whichever plate produces no growth from a broth with the lowest possible dose of the antibiotic determines the minimum bactericidal concentration. I go over these details (there are more) to give you a quick overview of the places where you can have unintended consequences from your decisions.

What if you decided to use tap water when you made up your culture broth? It’s possible that autoclaving the broth before its cultured would negate any unintended consequences of using water that wasn’t sterile, but some bacteria thrive on saline environments while others are inhibited by too much salinity. The use of deionized water would control for any variation in salinity that even autoclaving could not remove. That would help limit the impact on your bacteria’s growth either through enhancing the growth or inhibiting it.

But you used tap water, so the water has a little too much chlorine in it, compared to what would be in DI water. You don’t think this will be a big deal: gram negative bacteria are classically grown on MacConkey’s Agar, which has bile salts and NaCl to inhibit gram positive growth, so increased salinity shouldn’t be an issue. That is, unless the chlorine content is above even what the bacteria is able to tolerate compared to the MacConkey’s agar, leading to a reduced growth during the initial growth and culture, before you even attempt the MBC. That means before you’ve started testing the antibiotic, you’ve created a hostile environment that kills your bacteria - and invalidated your results.

You thought of that, which is why you used DI water instead, and made sure to sterilize everything in the autoclave before you started your test. In fact, everything went perfectly. You got the results you needed: this specific strain of E. coli is resistant to cephalosporins, but not to the quinolones. You pass this information on. What you don’t know is that the patient can’t safely take quinolones - the best drug to treat this patient’s infection isn’t safe for the patient. The unintended consequence here is that the doctor must decide to either treat with a less effective drug, or risk treatment with a drug the patient won’t react well to.

This is the challenge of rising antibiotic resistance, the challenge faced by researchers in the study yesterday. Even when science is done right, what works in the lab may not work in the clinic. This is the law of unintended consequences. The best way to try to prevent them is to always do more research. There’s no guarantee that research will find everything you need, but not doing the book work (or journal work, or internet work) will leave you hurting more often than it won’t.

I mentioned that sometimes the unintended consequences can be beneficial: aspirin is a classical example of this. When acetylsalicylic acid was first derived as an alternative to the salicylic acid from white willow bark (which caused digestive issues when used, another example of unintended consequences) it was used to treat pain. It was later found to serve as an anticoagulant as well, and has since gained widespread acceptance in treatment of heart attacks or strokes. This was a positive unintended consequence.

This isn’t a new idea: in 1936, Robert K. Merton listed possible causes of unintended consequences. See if you can identify which causes may be at play in our above scenarios.

1. Ignorance, or the inability to anticipate every possible outcome.
2. Errors of analysis or resulting from following habits that worked in past situations but do not necessarily apply to the current one.
3. Immediate interests overriding long term interests
4. Basic values that may prohibit certain actions over others (even if the resulting long term consequences could be unfavorable).
5. Self-defeating prophecies, or the drive to solve problems before they occur (possibly preventing such problems).

By being aware of the possible causes, you may be able to prevent mistakes yourself in the future. Research helps prevent ignorance related errors, along with errors of analysis. Being certain you understand the risks, benefits, and your own moral and ethical compass will help limit the consequences from immediate interests or basic value conflicts. Finally, remember that all scientists are human, and learn from your mistakes. Like the overturned boat, you gather yourself, pick up the pieces, and move forward.

Better isn't always better?

In another link from LinkedIn, we have a story about a study started 12 years ago, in Africa. In the US, iron supplementation is a common part of pregnant women's life; the benefits to the developing child can't be overestimated. In Africa, many children suffer from iron-deficient anemia. It seemed a natural solution to supplement the diet with iron supplements and other vitamins. However, during the study, more children on the supplement died than those not on the supplement, bringing the study to an abrupt and early end. I'll let you read the story for yourself; the reasons for the confusing results still aren't entirely understood, but are being sought out in order to hopefully correct both the nutrient deficient and the fatal result of correcting it in areas where malaria is endemic. I highlight it, however, not only because it's another LinkedIn story, but because it serves as an excellent reminder of the law of unintended consequences: solving one problem may cause another, or several others. While this is a large-scale example of unintended consequences, even in your lab work, you may encounter the same problems. Look for more detail on this idea in future posts.

So what's a doi?

Straight from the wiki: A digital object identifier (DOI) is a character string (a "digital identifier") used to uniquely identify an object such as an electronic document.

It is similar to an ISBN, which serves to uniquely identify books, but uniquely identifies electronic documents. It must be purchased, registered, and maintained. Thus, any document with a DOI is more likely to come from a reputable source.

On Wikipedia

When I first started college, there was no wikipedia (yes, I did just date myself), and professors were still adapting to the existence of the internet. Today, they’re adapting to ubiquity of the internet and the ease of access. Nowhere is this more obvious than in their hesitation to accept wikipedia.I will admit that not all articles on wikipedia are rigorously reviewed or accurate. Worse, once you leave wikipedia.com and wander into other wiki-type sites, you find sites that have smaller populations to monitor content and thus correct mistakes. These mistakes are why professors are hesitant to accept wikipedia as resources for academic papers. I am, however, unwilling to reject wikipedia entirely, so this is my guide to intelligent use of wikipedia in academia. Please note that if your professor tells you not to use wikipedia as a source, you should treat these tips the way you would any other search engine - uncited. If, however, your instructor is willing to accept a wiki source, you might try printing out your article (or grabbing a pdf copy at the time you access it so that there’s no concern about later edits), then go ahead and cite away. I’ve not had instructors willing to accept wikipedia entries, but that hasn’t stopped me from using them the same way I use search engines. In fact, unlike many search engines, wiki has an advantage - it gathers useful information in a single location and then provides citations for that information. Following the links to those external sources is the way to use wikipedia as a source and still keep your professors happy. Let’s look at two different examples. This first picture is the wikipedia entry for Pseudomonas pseudoalcaligenes, the bacteria isolated in the petri plate in my avatar. As you can see, there’s not much information, but there are a lot of links to follow out, so once I go to this one page, it becomes much easier to find other, more authoritative sites from this one. Further, among those references are peer-reviewed articles: the fact that the link starts “doi” is a giveaway that they come from sources every professor will accept.

Next is another wikipedia entry, this time, for “Gram negative”. I got here just by following the link in the first article. Look at how much more detailed this article is: pictures, drawings, sections dividing the information. Note, too, that there’s a section that’s been flagged for review. Wikipedia isn’t a perfect source, and I’m not trying to suggest that it is: this should never be a final source for information. But there is a wealth of information here that you can mine, links to follow out to sources that you can consider adequately authoritative to cite. This actually brings me to an important point, one that I don’t think many professors stress enough when they make a blanket ban on information sources. In science classes especially, you’ll hear your professors stress the importance of critical thinking and applying what you learn over rote memorization. It’s the difference between knowing that gram positive cells stain violet, and understanding that they stain violet because their cell walls are thicker and thus retain more of the violet dye. It’s comprehension. That comprehension, application, and critical thinking also allows you to look at your sources and decide if they are acceptable or not. That’s the sort of skill that your professors are looking for when they assign those sorts of papers, and when they ban an entire source of information, the question becomes if they find the information that unreliable or your skills that untested. My guess is that it is a combination of both. However, until we, as a student body, can demonstrate that we are capable of discerning useful information from junk, then sites like wikipedia will continue to languish, unheeded and ignored, or at best, as search engines. So ask yourself: What am I looking for? Will this answer my questions? Can I find the answer to my questions by following the links provided? Are these sources reliable? Does this make sense? And the most important question, the one that all that makes a scientist: Why?

An introduction to metric prefixes

This won’t give all the metric prefixes to you, but then, you won’t generally need them all. Most of the time, you’re working with just a few basic prefixes: kilo-, centi-, milli-, and micro-. In the internet age, we’re also a little more familiar with mega-, giga-, and even tera- (some of you may even have heard of peta-). In microbiology, being familiar with nano- , pico-, and even the Angstrom are useful, but if you can remember how to do the basic format, then it’ll be easier to put all the rest of these into place.

I know this is a little much to take in at once, but I’ll walk you through it. Each vertical line on this longer horizontal one represents a power of 10, or 10 multiplied by itself a given number of times, which is the same this as 10 raised to a given power or 10 to a given exponent.. At the central point, marked by the U, 10 is multiplied by itself 0 times. 10 to the 0 power equals 1, so this represents the base unit. That’s what the U represents: Unit. That’s also what the b below it means: base. Move one space to the left, and you get 10 to the first power, or 10. Move one space to the right, and you get 10 raised to -1, or 0.1 (one tenth). This pattern continues: Two spaces to the left is 10 to second, or 100, two to the right is 0.01 (one one-hundredth). Three spaces take you to 1000 on the left and 0.001 on the right.

That’s what makes the metric system so simple - everything is a factor of 10. There are no quarters or eighths or other fractional measurements to figure out. It’s all about moving a decimal point back and forth, and if you can draw a number line and keep the prefixes straight, then the rest becomes gravy.

The base unit of length in the metric system is the meter. If you’re used to working in the US system, then visualize a yard-stick. A meter is just longer than a yard - just over 39 inches (there’s also around 2 kilometers for every 3 miles, but I’m getting ahead of myself). We’ll start with the meter as our base unit and add our prefixes onto that. (The other units shown are L for liter, the measure for volume, and g for gram, which is the metric unit of mass. Note that in SI, which is the scientific standard, the basic unit of mass is actually the kilogram. However, for simplicity, we’ll just work with the meter).

1 meter (1 m) is just that, 1 meter. Since the metric system operates on a base 10 system, then moving the decimal right or left by one unit adds a prefix. Move the decimal one place to the left, and you have 10 meters (10 m) or 1 dekameter (1 dam). Move the decimal one place to the right, and now you have 0.1 meters (0.1 m) or 1 decimeter (1 dm). If you start 1 meter and move the decimal 2 units to the left, you have 100 meters (100 m) or 1 hectometer (1 hm). Go to the right instead, and you have 0.01 meters (0.01 m) or 1 centimeter (1 cm).

Continue following this pattern: 1000 meters are 1 kilometer (1 km). 1/1000 of 1 meter, or 0.001 meter is 1 millimeter (1 mm).

There are names for the prefixes for 10,000 and 100,000, as well as .0001 and .00001, but these are so rarely used that I must admit I don’t know them. Instead, we skip ahead to 1,000,000 meters or 1 megameter (1 Mm), 1,000,000,000 meters or 1 gigameter (1 Gm), 1,000,000,000,000 meters or 1 terameter (1 Tm), and 1,000,000,000,000,000 meters or 1 petameter (1 Pm). You’ll know that we really don’t use any of these prefixes with meters - once we get to lengths so vast that they are measured as millions, billions, trillions, and so on, of meters, we actually start moving over to different units, a derived unit, the light year (the distance light travels in one year).

On the other side of the decimal, however, in discussing fractions of a meter, 0.000 001 meters is 1 micrometer (1μm). This is sometimes also referred to as 1 micron.The next unit, 0.000 000 001 meters is 1 nanometer (1 nm) and 0.000 000 000 001 meters is 1 picometer (1 pm). Finally, there’s a very special unit of length, 0.1 nanometers or 0.000 000 000 1 meters that is equal to 1 Ångström (1 Å). Note: this is not Am, Angstrommeters, and there are no Angstromgrams or Angstromliters. This is the one little exception - it is a special unit of length named for a Swedish physicist. Officially, it should contain the dots (diacritics) over the o and the ring over the A, even though these are often omitted when being written in English.

So, to summarise:

I remember this with the following mnemonic:

King Henry died by drinking chocolate milk, mother. That sentence gives me the most frequently used prefixes, (kilo, hecto, deka, base units, deci, centi, milli, micro) which is enough to build the basic metric line. I use the comma to remind me to leave spaces between milli- and micro-, and for most things, that’s enough. Even working in microbiology, I really only need to learn the bottom half of the table, pictured below, and that’s a lot easier to learn once you have the basics mastered.

Do you have to use this? Not at all. If you have your own mnemonic, use that. If you can learn it another way, go with it. I’m just offering you the tools that have served me.

If nothing else, remember: once you start with length, mass, and time (meters, grams, and seconds) every other unit is derived (made) from that, and everything is in powers of 10. You may like ounces, pounds, tablespoons, inches, feet, yards, and so on, but keep in mind that there are more units and harder conversions between them than metric. At the very least, metric offers ease of use that the US system doesn’t. The more you use it, the more intuitive it gets. Also, if you’re in science or medicine, you MUST learn it.