Life After Death

Since Halloween is right around the corner, I found it fitting to write about life after death. This doesn’t go along the lines of the Walking Dead craze of zombies. I’m talking about microbes and how they interact with your body after death. An article by Mo Costandi ventures into the idea of what microbes do during the process of decomposition to bodies that are left out in the elements. There are five stages of decay that occur when a body is decomposing: the fresh stage, bloating stage, active and advanced decay stage, and the dry/remains stage. Microbes are found to mostly be active during the fresh and bloating stage of this process.

                The human body acts as a host to many different bacteria and they inhabit in communities in and on our body. A well-known area where a community resides is in the gut. When we are alive, most of our internal organs do not possess microbes. Once we die, however, the immune system stops working and bacteria is allowed to spread freely. The spread of bacteria leads to the guts and soft tissue around the gut to be digested from the inside out. This spread of bacteria around the body to the digestive system, liver, spleen, heart, and brain is known as the thanatomicrobiome (death microbiome). A study of the thanatomicrobiome indicates that samples from different organs in a cadaver were very similar to each other’s microbiome, while samples of the same organ from different cadavers were very different. This indicates that the microbiome varies from person to person based on how they lived before and where they are after they die.

                Another interesting highlight found in this article was that different stages of decomposition are associated with a different composition of cadaver bacteria. The stage of putrefaction, where the breakdown of soft tissues even further into gases, liquids, and salts, indicates a shift in bacteria. This shift is shown by a change from aerobic bacteria to anaerobic bacteria in the body. The shift is most likely due to the lack of oxygen coming through the body now that it is starting to decompose. This stage of feeding on body tissue and fermenting the sugar in them to produce gaseous by-products of methane, hydrogen sulfide, and ammonia leads to the bloating stage. The bloating stage occurs mostly in the abdomen where the gas builds up. From this point on, the insides of the body is more exposed to the elements, especially if the stomach bursts from built-up gas. Insects, scavengers, and other microbes are now involved in the decomposition process and introduce or take away microbes within the cadaveric ecosystem.

                An understanding of the studies of the decomposition process done at body farms, such as STAFS (which is mentioned in this article often), and the composition of the bacterial communities could help forensics teams learn when, where and how a person died. Having a better knowledge of the relationship between the bacterial communities and how they influence one another in the decomposition process along with other outside factors (such as bugs or scavengers) could be a refined tool to help determine the time of death.

Source: https://www.theguardian.com/science/neurophilosophy/2015/may/05/life-after-death

Virus Carrying DNA of Black Widow Spider Toxin

            As we trek through our biology classes, I have found that it sucks to become sick because of a virus but they are very interesting to learn about. This week, I found that biologists at Vanderbilt University published an article where they sequenced the genome of the WO virus, which infects the bacterial parasite Wolbachia, and discovered that the phage carries DNA from a eukaryotic association module. The eukaryotic association module (EAM) is a group of genes that vary in function, which were found in this case to be toxins, host-microbe interactions, host cell suicide, and secretion of proteins through the cell membrane. This was a surprising discovery because EAM has never been reported in bacteriophage genomes.

            To further clarify, there is a difference between eukaryotic and bacterial viruses. Eukaryotic viruses tend to hijack genes that are directly from the eukaryotic host, which is what they use to evade, manipulate, and counter-strike antiviral immune responses. Bacterial viruses, also known as bacteriophages, integrate genetic material from their bacterial host, such as toxins, photosynthesis, and pigment genes that contribute to the fitness of the bacterial host. Phage WO appeared to have a unique content with the cellular exit, entry, and defense mechanisms of the two domains of life.

            Specifically found in the EAM region that is preserved in this bacteriophage is the portion of DNA that is related to the black widow spider toxin gene. Another interesting finding from this sequencing process was that WO shares a number of other segments of DNA with animal genomes, which would be found more in the typical eukaryotic viruses and not the bacteriophages. It is suspected that pores are made in the membrane of the arthropod cells that surround the Wolbachia and allows the phage to overcome the bacterial and arthropod membranes that surround it.

            This discovery can use Wolbachia to fight dengue fever and Zika virus because it prevents the viruses from reproducing in the Aedes aegypti mosquito. Using this approach could help spread the new bacterial parasite through the mosquito population and substantially decrease the spread of the virus. Genetically engineering Wolbachia could further increase the effectiveness against the virus.

Source: Sarah R. Bordenstein, Seth R. Bordenstein. Eukaryotic association module in phage WO genomes from Wolbachia. Nature Communications, 2016; 7: 13155 DOI: 10.1038/ncomms13155

https://www.sciencedaily.com/releases/2016/10/161011131301.htm

Altering the "flavor" of humans could help fight malaria

I personally hate mosquito bites as much as anyone else does. They make you extremely itchy and they puff up into ugly hives if you scratch them too much. Along with the annoying side effects of the bites, they also have the ability to transfer diseases. Malaria has more recently become a threat that people use to get someone to wear bug spray, to avoid mosquito season, and to avoid going outside after a certain time or weather condition. Malaria is an infectious disease of humans and animals that is transmitted by the bite of the female Anopheles gambiae mosquito. Despite the decades of effort put to eradicate and control mosquitoes, there is still an estimation of millions of people that are infected every year. Malaria is seen as a terrifying disease because there is not a vaccine for it. Treatment can be used if the disease is caught early enough, but it is expensive and difficult to transport to the areas where it is needed most. A large amount of effort has been put towards eliminating the stages of parasite transmission or to limit the size of the mosquito population, but not much is known about the A.gambiae mosquito. Most insect research about the olfactory systems is based off of what is learned from Drosophilia melanogaster.

 According to Johns Hopkins Medicine, a study has been done to have a better understanding of how female A. gambiae mosquitoes receive and process olfactory information from their sensory regions by seeing where the olfactory neurons from those regions go to in the brain. The researchers GRP (green fluorescent protein) as a tag to make certain neurons glow green. Those neurons that glowed green were the ones that receive the complex odors through the odorant receptors (OR). The OR is what is used to distinguish humans from other animals. The ORs are located in the antennae and maxillary palps on the mosquito, and the stimulation of the neurons showed a glowing green path to the antennal lobes of the brain. The surprising result was that the other sensory receptor, the labella, showed that the OR neurons went to the subesophageal zone, which is associated with the sense of smell in other flies and insects. Their findings suggest that the sense of smell and taste combine in the brain to create a “flavor” to the mosquitoes, which is what encourages them to bite us. The mosquitoes most likely pick up on the bodily odors and influence them on whether or not they want to bite us based on how appetizing we seem to them.

This research could be important for the future of malaria prevention and also mosquito control. The mosquito control could be done by finding a way to repel mosquitos by either deterring their long range signals by targeting the antennal neurons and make it less likely that they will come close to us or by making us less appetizing in the direct contact by targeting the labellar neurons. A repellant can be made to not smell as bas for humans as other repellants but could smell disgusting to the mosquitos to where they will not bite us. The drop in mosquito bites could potentially starve the females and decrease the mosquito population, while also decreasing the risk of malaria.

Article Source:

Olena Riabinina, Darya Task, Elizabeth Marr, Chun-Chieh Lin, Robert Alford, David A. O’Brochta, Christopher J. Potter. Organization of olfactory centres in the malaria mosquito Anopheles gambiae. Nature Communications, 2016; 7: 13010 DOI: 10.1038/ncomms13010

Cite Page Found:

Johns Hopkins Medicine. “Altering the ‘flavor’ of humans could help fight malaria.” ScienceDaily. ScienceDaily, 10 October 2016. <www.sciencedaily.com/releases/2016/10/161010103830.htm>. 

Circadian clocks and breast cancer

The article that I ran across for this week discusses how the disruption of your circadian clock could increase your chances of getting breast cancer. A circadian clock is driven by environmental cues and drives 24-hour rhythms in the cellular processes in almost every tissue in the body. The circadian clock controls cellular processes, which means that is plays a role in cell division. The disruption of circadian rhythms can be associated with abnormal cell divisions that occur in cancer.  The environmental cue that is most talked about in the article is the exposure to light in the natural day and night cycle. The modern western lifestyle that we live may have an influence on the onset and progression on breast cancer by the disruption of our internal clocks. This disruption could be brought upon our circadian clocks by irregular shift work, repeated bouts of jet lag, and during ageing.

The suprachiasmatic nucleus is a central pacemaker that coordinates circadian rhythms by the use of light to be the established time-giver. As we know, the exposure to natural light indicates to our bodies that we need to wake up and be active, while the lack of natural light lets us know that we need to rest. This time of rest is when our body has the chance to rejuvenate itself and work to keep a healthy system. The article indicated that women who work irregular shift patterns have a higher frequency of hormone-related breast cancer. The definition used for irregular night shifts refers to working a mix of nights and days during the week. An example of this could be nurses, who are on-call a majority of the time and work all-times of the day if it is necessary. Their circadian clocks do not have enough time adjust to the new shift pattern before it is changed again.

             The thought of cancer has always been seen as scary and as something that is all too real when it comes into your life or to someone close to you. Breast cancer is what many women fear as they grow older, especially if someone in their family has had it before. An example of this would be myself because my grandmother had breast cancer and I have my concerns about whether or not I have the possibility of getting breast cancer as well. Now I have learned that my life as a college student with constant changes in my sleeping patterns provides even more of a risk. I realize that this is important information for everyone who lives a nocturnal lifestyle and that it could lead to a lifestyle change to avoid increasing you risk of cancer. 

Link to Source: http://download.springer.com/static/pdf/658/art%253A10.1186%252Fs13058-016-0743-z.pdf?originUrl=http%3A%2F%2Fbreast-cancer-research.biomedcentral.com%2Farticle%2F10.1186%2Fs13058-016-0743-z&token2=exp=1475782567~acl=%2Fstatic%2Fpdf%2F658%2Fart%25253A10.1186%25252Fs13058-016-0743-z.pdf*~hmac=b4dd6fe3fe7ee81f1fff5313b4331f4a2fc5e2c1af4e37bdc86311eebc4dc975

Citation: Blakeman, V.; Williams, J.; Meng, Q.; Streuli, C.; Breast Cancer Research. 2016. 10.1186/s13058-016-0743-z