AP Biology class blog for discussing current research in Biology

Tag: human

Yes, Some of Us Have Different Human Ecosystems.

Our human ecosystems inside of us are composed of countless quantities of cells. However, only 10% of those cells are human cells.  Jeroen Raes , a Biologist based in Belgium, made a vital and fascinating discovery about the other 90%. He discovered that there are three different possible ecosystems inside individual humans. Each person has one of these three ecosystems: bacteriode, prevotella or ruminococcus. These ecosystems are composed of hundreds of trillions of harmless bacteria. One could explain our relationship with these bacteria as symbiotic, as we give them a share of food and they return the favor by helping us digest food and convert it to energy. Furthermore, these bacteria help us fight disease, and can even make us happier by triggering our neurons to release more serotonin. Raes’ experiment tested people from the US, Japan, and Denmark. Despite each regions unique diets, Raes claims to have found no correlation between diets and their individual ecosystems. Furthermore, Raes found no correlation between their age/genetic makeup and individual ecosystems.

People who have the bacteriode system “have a bias” toward bacteria that get most of their energy from proteins and carbohydrates. Bacteriode ecosystems also have more bacteria that make greater quantities of vitamins C, B2, B5, and H. On the contrary, both prevotella and ruminococcus ecosystems mostly digest proteins that are sugar coated. Both of these ecosystems also have more bacteria that create vitamin B1 and folic acid.

Raes’ findings have yielded very confusing results. Even Raes has conceded that he is unsure as to why only three total human ecosystems exist. Moreover, Raes admits his sample size of only a few hundred people will increase with more time and funding. Raes hopes to further his research on these unique human ecosystems, and potentially find links to obesity, diabetes, Crohn’s disease, and autism.


Secure Passcodes : Not Just For Your Computer… But For Your Gut

What is the Human Gut Microbiome?

Human gut microbiomes are made up of all the bacteria present in your gut. The Bacteria in your gut outnumbers the cells by a ratio of 10 to 1. While the presence of that much bacteria sounds like a bad thing, it can be confirmed that “the gut microbiome is very important for human health—that much we certainly know”.  The nearly 100 billion Bacteria cells per gram are actually what helps the body digest food and remove the bacteria that is bad for your gut.


(Left) Bacteria on vs not on the intestines       (Right) Gut Microbiome Graphic

A Unique Passcode

As said above, the human gut microbiome is essential to digesting food but more importantly keeping our body healthy. The thought of controlling a person’s gut bacteria in order to keep them healthy and fight illness is fascinating to scientists. The key to using the microbiome to fight sickness is in the “passcode” that is essential to unlocking its potential. Each microbe, according to recent research, requires a unique passcode. The research done by scientists according to says that once there is a way to determine the “passcode” it will unlock a whole new world of probiotic treatment in the future.

Why Else is the Microbiome important

According to other research done within the past few years, it has been found that sleep can also be linked to the human gut and stomach. The quality of sleep a person gets can be linked to their “biological rhythms, immune function, and nutrient metabolism” however it is still unknown to what extent the microbiome is affecting human sleep.


While researchers still have many questions about the human gut microbiome and how it contributes to health, wellness, and overall human biology, once they have come to some more concrete conclusions the impacts of controlling the bacteria in the human gut would exponentially improve the health of many people. It may sound weird that your bacteria have a “passcode” with which to be controlled, but hey, conclusive findings of the microbiome could even help you get a better night’s sleep! And who doesn’t want that?

The Human Brain vs. Chimpanzee Brains – The TH Gene

Well let’s start off with, what is the TH gene? The TH gene is a “protein encoded by this gene is involved in the conversion of tyrosine to dopamine. It is the rate-limiting enzyme in the synthesis of catecholamines, hence plays a key role in the physiology of adrenergic neurons.” How does this even relate to human and chimpanzee brains?

However, here’s a little background to the dimensions of the human brain compared to the chimpanzee brain. Modern humans share about 95% of their genetic code with chimpanzees.  Yet, human brains are three times larger, have many more cells, and would therefore have more processing power than a chimpanzee. Does this mean chimpanzees do not function as efficiently as the human brain or are there just some areas a human brain can be efficient on better as for the chimpanzee brain as well ?

According to two researchers from Yale University, Ying Zhu and André Sousa, TH was found highly expressed in human neocortex, but absent from chimpanzee neocortex. Sousa states, “The neocortical expression of this gene was most likely lost in a common ancestor and reappeared in the human lineage.” Since the gene is absent from the chimpanzee cortex, does this mean that they do not produce any dopamine? Do chimpanzees produce dopamine in a different way?

At the end of the day, we can conclude that human and chimpanzee brains do have a vast majority of similarities. Alternatively, there are certain aspects to the chimpanzee and human brain that allow us to differentiate the two and continue to allow for extensive research in such fields. I challenge you to discover something specific about the human brain and chimpanzee brain that are both extremely similar and different. What will you discover next?

Evolution of Human Lifespans


(Locutus Borg, Wikimedia Commons)

Humans have started living longer and healthier lives. According to research conducted by various international teams, the last two centuries have had a greater percent increase in human lifespan than the past millions of years did.

The research teams compared the average lifespan of the most developed societies to the average lifespan of modern-day hunter-gatherer populations, which most closely resemble the lifespan and lifestyle of early humans. The researchers found that developed countries, such as Sweden, have average lifespans of eighty years now (an increase from the mid-thirties range it was in 200 years ago). On the other hand, hunter-gatherer populations such as the Hadza in Tanzania live only ten to twenty years longer than wild primates.

Such drastic improvements in human longevity are attributed to the advent of several post-industrial era features, including modern medicine and supermarkets. However, males trail behind females in terms of lifespan by at least three to four years– something that has not changed since the beginning of primate history.

The exact reason for the lifespan gender gap is unknown. Some hypotheses propose that males are more at-risk because they carry one X-chromosome and one Y-chromosome, as opposed to the females’ two X-chromosomes, which makes males more susceptible to disease. Another possible explanation centers around harmful male-related behavior, such as fighting. What do you think is the most likely reason for the gender gap?

Possible Connections between the Gut Microbiome and the Brain

It is not a new concept that gut bacteria affects a person’s health. But this article published in The Atlantic explains how they may even affect the human brain. Some researchers believe that the microbiome may play a role in regulating how people think and feel. Scientists have found evidence that this community of bacteria (trillions of cells that together weigh between one and three pounds) could play a crucial role in autism, anxiety, depression, and other disorders.


Much of the most intriguing work has been done on autism. For years, it has been noted that about 75 percent of people with autism also have some gastrointestinal abnormality, like digestive issues or food allergies. This has prompted scientists to search for potential connections between the gut microbiome and autism; recent studies find that autistic people’s microbiome differs significantly from those of control groups. Caltech microbiologist Sarkis Mazmanian specifically focuses on a species called Bacteroides fragilis, which is seen in smaller quantities in some children with autism.  Mazmanian and several colleagues fed B. fragilis from humans to mice with symptoms similar to autism. The treatment altered the makeup of the animals’ microbiome, and more importantly, improved their behavior: They became less anxious and communicated more with other mice.

Perhaps the most well-known human study was done by Emeran Mayer, a gastroenterologist at UCLA. He recruited 25 subjects (all healthy women) for four weeks. He had 12 of them eat a cup of commercially available yogurt twice a day, while the rest didn’t. Yogurt is a probiotic, meaning it contains live bacteria. In this case it contained four species: bifidobacterium, streptococcus, lactococcus, and lactobacillus. Before and after the study, subjects were given brain scans to gauge their response to a series of images of facial expressions—happiness, sadness, anger, and so on.

To Mayer’s surprise, the results showed significant differences between the two groups. The yogurt eaters reacted more calmly to the images than the control group. “The contrast was clear,” says Mayer. “This was not what we expected, that eating a yogurt twice a day for a few weeks would do something to your brain.” He thinks the bacteria in the yogurt changed the makeup of the subjects’ gut microbes, and that this led to the production of compounds that modified brain chemistry.

As scientists learn more about how the gut-brain microbial network operates, they think it could be manipulated to treat psychiatric disorders. And because these microbes have eons of experience modifying our brains, they are likely to be more precise and subtle than current pharmacological approaches, which could mean fewer side effects. “I think these microbes will have a real effect on how we treat these disorders,” neuroscientist John Cryan says. “This is a whole new way to modulate brain function.”

Junk Food Encourages Disease

According to a recent discovery posted in Science News, a typical American diet, consisting of poorly nutritional foods, leaves one prone to getting sick by weakening their immune system. Interestingly enough, this issue is rooted in cells that are not your own. In your gut microbiome, there are countless varieties and numbers of bacteria, all working away at the food that passes through your gut. Now, these bacteria are actually quite manipulative, and besides from feeding off of the food that you eat, teach your immune system what to attack, like an instructor or tutor for your immune system, albeit a biased one. These bacteria have colonized your body. They’re not just going to let some pathogen get in the way of their free meal ticket.

(What it looks like in there)

What happens when you eat certain foods, like junk foods, is that your gut microbiome changes. Different bacteria thrive on the fatty or sugary foods while other bacteria that survive off of more complex starches and carbs fade away, changing the demographic of your gut microbiome. This limited variety also limits the amount of invaders your immune system knows as hostile, or understands how to deal with, and therefore, you are more susceptible to disease, or medical complications.

(Actual photo of a biofilm found in the gut)

This was proven by taking samples from fit and obese humans and inserting them in otherwise sterile mice. Their resulting microbiomes grew, and the mice with the obese implant suffered more medical problems than the mice with the fit implant. This is because there were not enough “trainer” bacteria in the first mice’s gut to help train it to fend off disease, and thus it got sick more easily. So don’t go blaming your immune system the next time you get sick. It may be your fault for avoiding real, nutritional food (not just salad), and not taking care of it.

The moral of the story is to eat your vegetables and serve the bacterial overlords that have taken host in your body.

They’re good for you.

Trust me.


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