News » Chapter 14 Host-Microbe Interactions

Gut microbes’ role in species divergence

Contributed by mcoplan on Aug 16, 2013 - 10:01 AM

It is well known that gut microbes play an important role in the health of many organisms.  Seth Bordenstein and Robert Brucker, biologists at Vanderbilt University, were curious to see what other effects these microbes may have on an organism.  They studied the role of microbes in three related species of parasitic jewel wasps.  Two of the species, Nasonia giraulti and N. longicornis, are closely related, whereas the third species, N. vitripennis, diverged about 1 million years ago.  Offspring of  a cross between N. giraulti and N. longicornis generally result in surviving offspring.  However, when either specie was breed with N. vitripennis, almost all male larvae in the second generation die. 

The Microbes in Our Bodies are as Unique as We Are

Contributed by tjtownsend on Aug 14, 2013 - 09:59 AM

In a world of bacteria, the tiny microbes that inhabit the human gut can reveal a lot about an individual.  The human body houses such a high amount of microbes that it significantly outnumbers the number of human cells a person has.  Recently, scientists have sought to better understand the vast number of microbes in the colon, in order to use this information to better human health.

The American Gut Project is dissecting thousands of stool samples to truly understand what microbes exist in the colon, what each microbes function is, and how this information can be used to improve certain diseases linked to the colon.  In the midst of the project, research has shown that the microbes in the human gut are deeply connected to the health of each individual, linking type 2 diabetes, colitis, asthma, depression and weight gain to colon microbes. 

As scientists collect and analyze poop, they have found that no two people contain the same exact makeup of microbes.  The reason the gut microbes differ from individual to individual remains unclear.  However, there are some patterns that are emerging. To create a “supergut” of microbes, one should eat a diet rich in onions, garlic, and leeks.  Cooking vegetables al dente has been shown to increase microbe diversity because the body has to work harder to break down the food so more of that food ends up in the colon.  Like all other diets, the more diverse the plate is, the more diverse fiber that can be consumed, also leading to a healthy, diverse colon.  The scientists of the American Gut Project encourage everyone to get a little dirty and keep windows open, exercise outside and work in a garden.  Those who own dogs have more diverse microbes as well.  Exposure to these environmental microbes helps flourish the colon microbes.  

Stomach Bug uses novel mechanism to infect cells

Contributed by bungerer on Aug 01, 2013 - 12:12 PM

At the UT Southwestern Medical Center, researchers are investigating a seafood contaminant that thrives in the summer. This contaminant, Vibrio paraphaemolyticus, is a bacterium that causes a stomach flu and has a novel mechanism by which it infects cells. The bacterium inject proteins, known as effectors which regulator biological activity, into the cell. VopQ is an important effector and is the focus of this research. Once into the cell, VopQ disrupts autophagy. Autophagy is the process of recycling nutrients to be reused as metabolites for the cell. The mechanism by which VopQ disrupts autophagy is novel. VopQ creates gated ion channels in the cell membrane. These channels are pores that only permit regulated ions and/or small molecules to pass through the cell membrane. They also have an open and close mechanism for the particles, similar to a gate. 

Corals buddy up with bacteria

Contributed by eduardojpina on Jul 26, 2013 - 03:17 PM

In a new study conducted by researchers at the Woods Hole Oceanographic Institution (WHOI) and King Abdullah University of Science and Technology (KAUST), there is new evidence of a complex symbiotic relationship between certain species of reef building coral and bacteria that wasn't previously understood. It has been known that many coral form symbiotic relationships with many other organisms, such as algae. Researchers have already understood that a species of reef building coral, Stylophora pistillata, hosts a group of bacteria called Endozoicomonas. However, where these bacteria live and what they do for the coral isn't well known.

Gut Bugs Could Explain Obesity-Cancer Link

Contributed by hmelfman on Jul 24, 2013 - 03:09 PM

Obesity is associated with increased risks of certain types of cancers, such as colorectal and liver cancer. The mechanism behind this relationship in humans is still unknown, but recent research has shown that gut microbiota may play a role. Scientists at the Cancer Institute of the Japanese Foundation for Cancer Research in Tokyo studied the relationship between gut microbes and the development of liver cancer using lean and obese mice. By exposing the mice to a cancer-causing chemical shortly after birth, all of the obese mice and a few of the lean mice developed cancer. The cancerous tumors in the obese mice contained a very high level of deoxycholic acid (DCA), which is known to damage DNA and cause inflammation of the liver. DCA is a byproduct of the break down of bile acids by certain gut microbes. The next question was what led to the increased levels of DCA. The scientists found that the obese mice have a different mix of bacteria in their guts, including gram-positive bacterial strains that are less existent in lean mice. They proved that this mix of bacteria was associated with increased DCA levels. An antibiotic targeting the gram-positive bacteria led to decreased DCA levels and reductions in cancer incidence.

Therefore, the mechanism is as follows. Obesity causes gut microbiology changes. Gut bugs that are gram-positive bacteria strains leads to elevated levels of DCA in the body. The more DCA present, the greater the risk for developing liver cancer. If further research proves that a similar mechanism is seen in humans, then this information can be used to screen for liver cancer and to decrease ones risk of developing cancer.

Gut microbes may put barrier between species

Contributed by keis.yamamoto on Jul 23, 2013 - 02:51 PM

<font face="Times New Roman, serif" style="color:rgb(0,0,0);font-size:medium;">A recent study, conducted by Professor Seth Bordenstein of Vanderbilt University, proposed that two species of jewel wasp, <font face="Times New Roman, serif" style="color:rgb(0,0,0);font-size:medium;">Nasonia giraulti</font><font face="Times New Roman, serif" style="color:rgb(0,0,0);font-size:medium;"> and </font><font face="Times New Roman, serif" style="color:rgb(0,0,0);font-size:medium;">Nasonia Vitripennis</font><font face="Times New Roman, serif" style="color:rgb(0,0,0);font-size:medium;">, remain separate species largely because of microbe interference, not lethal incompatibility in DNA, as many biologists believed.</font></font>

Intestinal Bacteria May Fuel Inflammation and Worsen HIV Disease

Contributed by jmidso on Jul 17, 2013 - 09:10 AM

Surprisingly, the human body consists of more bacterial cells than human cells. An important region where bacteria reside is the intestinal tract. The bacterial community present plays an important role not only in food absorption, but also in the body’s immune response. The bacterial community is dynamic and adapts as its environment, the human body, changes. As the title suggests, researchers hypothesized that HIV infection would have a significant impact the intestinal bacterial community and that this change in part causes the chronic inflammation found in many HIV patients.

Bugs provide new insights into relationships between animals and bacteria

Contributed by tmpernsteine on Jul 15, 2013 - 09:18 PM

A unique three-tiered symbiotic relationship is now being studied in order to better understand how organisms transfer and share genes in mutualistic interactions. Surprisingly, this gene transfer is not analogous to how mitochondria and chloroplasts have evolved with their host genome. 

Invasive Ladybird has Biological Weapon

Contributed by georgen on Jul 12, 2013 - 07:33 PM

The harlequin ladybird Harmonia axyridis, one of the world’s most invasive insects, has become an invader of Europe and North America. Initially introduced for biological pest control, the harlequin ladybird, native to Asia, is now harming indigenous ladybird species, specifically the seven-spotted ladybird Coccinella septempunctata. Previously, some scientists believed the harlequin’s success was due to a harmonine, a toxic antibacterial chemical found in its blood. However, entomologist Andreas Vilcinskas of Justus-Liebig-University in Giessen, Germany believes the harlequin’s success is partly due to the presence of a single-celled parasite. 

Intestinal microbes are linked to obesity and cancer

Contributed by zretzlaff on Jul 12, 2013 - 07:50 AM

Today, there is an epidemic in the United States that was not apparent 50 years ago. This epidemic is obesity amongst adults and children in this country. Blame for obesity has been set upon processed foods and sedentary lifestyles, but it wasn’t until Eiji Hara of Tokyo turned his attention towards microbes in the intestine that other significant factors were considered to be risks of obesity as well.

Hara executed two types of experiments. In one experiment, he fed mice different diets to make them obese or lean, but each group was still exposed to a carcinogen. In another experiment, he focused on mice genetically susceptible to being obese even while fed a normal diet.

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