Biology for Writers: The Human Microbiome

Good morning, everyone! Happy Monday! It’s the second week of November (already!), so here I am with a quick post on a bioscience topic which may be of interest to some of the writers who read my blog (and don’t have that much background in science). Let’s get right to it!

The Overview

One of the biggest topics in science right now is the human microbiome. What is a microbiome, you ask? Well, it’s simply the entire set of microbes that inhabit the human body.

Image source

Yes, that’s right–there are microbes in you, right now, and they’re even supposed to be there! As a matter of fact, there are more bacteria, archaea (basically extreme-environment microbes), and unicellular fungi in your body than there are human cells. Yes, you heard that right–we humans are more microbial than human. Blows your mind a little, doesn’t it?

So what do these microbes do for us? Are they good for anything, or do they just sit there? Well, my friends, I’m glad you asked. Let’s take a look at some of the parts of our bodies where our normal microbes are most influential.

The Mouth

We all know about dental plaque, and brushing our teeth so we don’t get it. (Seriously, I hope you all brush your teeth, ’cause plaque is disgusting.) But your mouth also contains 50-100 billion normal bacteria of at least 500 different species, mostly anaerobes, or bacteria that don’t require oxygen to live. (In fact, some anaerobes die when exposed to oxygen.) Streptococcus mutans and S. sanguinis, the organisms that cause plaque when they build up into a biofilm, are both “facultative anaerobes,” which means that they can either use oxygen or not depending on conditions in their environment (the mouth). Many other normal mouth bacteria can cause problems for the human host if there is bleeding in the mouth, or some other abnormal condition, bringing up an important point for the microbiome in general: Microbes that are normal inhabitants of our bodies (“normal flora” or “microbiota”) can be pathogenic if they are moved to a different spot or if something abnormal happens. These are called “opportunistic pathogens,” and we’ll see more of them as we move through the body.

The Gastrointestinal Tract

This is one of the places where the human microbiome is most important and best characterized; a lot of work has been done linking the gut microbiome composition to everything from diet to Parkinson’s disease. And gut microbes do a lot for us. For instance, we can’t digest vegetables without our gut microbes, and other microbes make vitamin K for us. That’s pretty darn helpful of them, don’t you think?

But when I say “gut microbiome,” what am I talking about? It turns out that not every part of the human body is colonized by microbes; accessory organs such as the liver and pancreas are sterile, and the stomach has a very low level of microbes due to the high acid content there (the stomach’s pH, a measure of its acidic content, is about 2–so very acidic). Not many things can survive the acidic environment of the stomach, which is why it’s great for digestion. One Helicobacter species, however, survives by burrowing into the stomach lining and secreting basic compounds, which neutralize the surrounding acid to create a neutral pH (good for life). This species can also cause stomach ulcers when it has lived in the stomach lining for a long time.

So if the stomach doesn’t have very many microbes, where is this gut microbiome I’ve been telling you about? Most of the gut microbiota live in the ileum (the last part of the small intestine) and in the colon (also known as the large intestine), where, as I mentioned, they help us digest our food, give us nutrients, and take up space so invaders can’t enter. This is known as a “mutualism,” in which both symbiotic partners benefit from their relationship. How do the bacteria benefit from us? Well, most parts of the body are at a neutral pH, which as I’ve already said is good for life, and they remain at a constant warm temperature, which allows microbes to grow.

I also just want to point out quickly that taking too many antibiotics can interrupt your gut microbes, and thus actually make you susceptible to sickness, since with space freed up by antibiotic treatment, pathogens can easily colonize your gut. Since this post is mainly about the microbiome, that’s all the space I can give to this extensive topic, but if you’re interested in learning more, feel free to comment below!

The Skin

The skin is one of our first defenses against microbes, since we are constantly sloughing off dead skin cells, but it is also colonized by many microbes. Similar to the gut microbiome, these take up space on your skin, preventing infection by pathogens. The skin microbiome also includes Staphylococcus aureus, an opportunistic pathogen which normally lives on the skin surface, but can cause problems when it penetrates deeper into the body. For instance, if you have a deep puncture wound, your normal S. aureus may get under your skin (literally) and cause nasty carbuncles and things when it infects you. So if you’re writing a novel and your character gets wounded, this is one thing that could follow that up if you want to give them extra torture be realistic about the consequences of wounding.

Find out More!

Here are some resources if you’d like to find out more about the human microbiome!

Human Microbiome Project–This would be a great resource if you want to find out some of the specific microbes that exist in each place on the human body (there are many, many more microbes than the ones I talked about today).

The Gut Microbiome in Health and Disease–A scientific paper about the gut microbiome. (Please note this is intended for a scientific audience, so it may be a bit dense.)

When Gut Bacteria Change Brain Function–An interesting general-audience article about how gut bacteria impact the brain.

I will continue to add more resources here as I find them! If you find interesting resources, feel free to let me know in the comments and I will consider adding them to this page.

That’s it for my first Biology for Writers post! Are you thinking of using the microbiome in your story? If so, how? Is there anything else you’d like to know about the microbiome? (I’m definitely not an expert, but I can point you to more resources if you’d like!) Are there other biology topics you’d like to see addressed in this monthly post series? Let me know in the comments!


The Synthetic Biology Equation: Engineering + Bioscience = The Future of Biotech

(Perhaps that title is a bit audacious; I don’t claim to be able to predict the future of anything. But it’s entirely possible that synth bio will play a big role in biotech in the future. Let’s explore that more below. . . .)

Good morning, everyone! I was traveling last week, which prevented my putting up this post on Saturday as usual, and I decided to postpone it till today.

One of the classes I took last semester was Biotechnology and Society, and I decided to write my final paper on synthetic biology after the teacher mentioned the first production of a self-replicating “man-made” cell by a group of scientists in California.

Before I dig into that a bit more, though, let me define synthetic biology (or synth bio for short): it is the full-scale application of engineering techniques to biological systems. How is it different from regular genetic engineering/GMO production, then? The answer lies in the scale of said engineering: for genetic engineering, it’s on the gene level, one or more genes plus regulatory elements (regulating the expression of the gene) within an organism. For synth bio, though, engineering is on the level of an entire chromosome or even a genome, either wholescale editing or rewriting from the ground up. Essentially, synth bio is genetic engineering on steroids.

Image result for stephane leduc
Stephane Leduc, author of La Biologie Synthetique


A little history: Synthetic biology was first conceived, if not put into practice, way back in 1912 when Stephane Leduc, a French scientist, published La Biologie Synthetique. In this book, Leduc stated that the consistent and controlled reproduction of natural processes seen in other sciences, like chemistry, was lacking in biology at his time. Synthetic biology couldn’t take off, though, without the development of molecular biology in the mid-1900s, starting with Crick and Watson’s discovery of DNA structure (a topic for another time). Then, the development of fast, easy sequencing sparked our current age of genomics, the study of whole genomes, and synthetic biology had all the tools it needed to become a practiced discipline.

This brings us up to recent developments. Just last year, a research group at the J. Craig Venter Institute, headed by Venter himself, succeeded in creating a self-replicating bacterium with a synthetic genome, the first of its kind. The bacterium, JCVI-syn3.0, has only what Venter’s team determined was the minimal genome necessary for life, a feat they accomplished by “mixing and matching” genes of the small bacterium Mycoplasma mycoides to find which ones a bacterium could live without. In future, Venter and his team see the use of similar synthetic bacteria not only to learn about life, but to engineer it for specific purposes, like biofuel production.

Image result for jcvi syn 3.0
A colony of JCVI-syn3.0


The question is: how synthetic is JCVI-syn3.0? Technically, it’s not really a man-made bacterium. Only the genome was man-made, and that was really only adapted from the genome of M. mycoides. The “shell” the genome was inserted into was simply a living bacterium with the genome removed. This is a big step for synthetic biology, but it has a long way to go before it is truly dictionary-definition synthetic.

What do you think? Have you heard of synthetic biology? Did you hear about the production of JCVI-syn3.0? Tell me in the comments!

Bacteria and Bioplastics

Hello, everyone! It’s the second Saturday of the month, which means I am here with a science post. I’ve been taking a class about biotechnology (which actually ended this past week), so I’ve been finding various biotech things to give presentations about and so forth. Today’s topic, bacteria-produced bioplastics, was one of those biotech things.

What is bioplastic? I’m glad you asked! Bioplastics are biodegradable plastics which are being investigated to replace petroleum-based plastics, since they could reduce costs and environmental impacts of plastic use. A major type of bioplastic, which I’m going to focus on today, is the polyhydroxyalkoanates (PHAs for short). These are polyesters (a type of organic molecule) naturally produced in bacteria as reserves of carbon and energy. They can then be broken down when the bacterium needs the carbon or energy, which makes them truly biodegradable. (Fun fact: I read about a PhD student who got a certain bacterium to produce 80% of its weight in PHAs by using ice cream as a nutrient medium.)

Image result for alcaligenes eutrophus
Alcaligenes eutrophus, a PHA-producing bacterium.

PHAs have many and varied potential applications. They have been proposed as a packaging for foods like cheese, as biodegradable containers for things like drugs and fertilizers, as a material for disposable items like razors, cups, and shampoo bottles, and in the medical field, to be used as a material for things like sutures and bone replacements. Their properties are similar to those of currently used plastics like polypropylene, which could make the transition smoother if they were to go into use.


The difficulty, up until recently, has not been getting the bacteria to make PHAs, but getting the PHAs out of the bacteria. Last month, however, it was reported that a Spanish research team has developed and patented a method for genetically engineering a predatory bacterium, Bdellovibrio bacteriovorus, to break down the PHA producers, but not the PHAs. A number of companies are already interested in using this method commercially; it could be used for extracting valuable enzymes and other proteins as well as for bioplastic production. This method is much safer and less expensive than previous methods that used things like chemical detergents to extract PHAs. I think it’s a big step forward in making PHAs practical.

Image result for bdellovibrio bacteriovorus
Bdellovibrio bacteriovorus, the predatory bacterium


Here are my sources if you want to learn more:

What do you think of this technology? Would you use a bioplastic? Have you ever heard of this before? Share in the comments!