Delving into the Diversity of The Plague of Justinian

Wayson stain of Yersinia pestis showing the characteristic
Yersinia pestis. U.S. Center for Disease Control [Public domain], via Wikimedia Commons.
Human teeth play a key role in our understanding of how organisms evolve. Whenever a possible new member of the hominid family is uncovered, the shape and number of teeth are used to place that individual in the family tree. Teeth also harbor information about pathogens that have plagued humans for millennia. Because bacteria use our bloodstream as a transport system, protected places that can preserve DNA—like the pulp of teeth—are a rich medium for uncovering information about humans and the microbes that infected them.

Teeth have been the choice for identifying the infectious agent behind the Plague of Justinian in the sixth century and the Black Plague in the 14th century. In fact, Yersinia pestis, the bacterium responsible for these plagues, has infected humans as far back as the Neolithic. But what can we learn about the pandemic strain or strains of Y. pestis described in historical records? A team of researchers from Europe and the US, many of whom have been delving into the history of Y. pestis for the last decade, wanted to further investigate the Plague of Justinian. They studied bacterial DNA extracted from human remains found in Western European communal graves that were dated to around 541–750, the period of the historically documented Plague of Justinian. Their investigation examined the bacteria’s diversity and how far it spread during this “First Pandemic” of plague. Continue reading “Delving into the Diversity of The Plague of Justinian”

Expanding the Plague Family Tree: Yersinia pestis in the Neolithic

Yersinia pestis. See page for author [Public domain], via Wikimedia Commons

In recent years, scientists have been able to refine their molecular tools to resurrect ancient DNA from human graves and determine that yes, Yersinia pestis was the causative agent for the Black Death in the 14th century and the Plague of Justinian in the 6th century.  As more and more human graves have been uncovered, their DNA has revealed many secrets that scientists even ten years ago were unable to discover. With the ability to sequence entire genomes of bacteria that died with their hosts hundreds and even thousands of years ago, researchers are exploring the rise and possible spread of Y. pestis. Each new member sequence adds to the Y. pestis family tree, pinpointing the origin of this bacteria as it diverged from its ancestor Y. pseudotuberculosis. Peering into the past, scientists have been able to track down a strain of Y. pestis from individuals in a Swedish passage grave that is basal to known strains and that the authors of a Cell article suggest has interesting implications.

This pathogenic journey into history started by analyzing ancient DNA data sets from the teeth of individuals present in a communal passage grave in Gökhem parish, located in western Sweden, for any disease-causing microbial sequences that might be present. Y. pestis was flagged in one 20-year-old female dated 4,867–5,040 years ago. The bacterial sequences from this individual, named Gok2, were more closely aligned with Y. pestis than the Y. pseudotuberculosis reference genome. Continue reading “Expanding the Plague Family Tree: Yersinia pestis in the Neolithic”

Black-Footed Ferrets: Back from the Brink

Bff = black footed ferret
Giving some love to a BFF (Black-Footed Ferret).

Today is Valentine’s Day (February 14) and our thoughts turn to doing something special for a significant other (so),  a best friend (bf) or best friend forever (bff).  In this blog we consider doing something special for a bff, but the bff at focus here is not human.

This bff is the black-footed ferret.

That’s correct—we’re talking about the weasel-like critter with the black mask, black tail tip and black feet. This small, wiry animal, with the help of some particularly dedicated humans, has had an amazing come-back story since the 1970s, when these ferrets were believed to be extinct.

About the BFF (Black-Footed Ferret)
The black-footed ferret, Mustela nigripes, is a member of the family Mustelidae, which includes mink, badger, marten, fisher, polecat and wolverine (of course domestic ferrets are also members of this family). Like mink and other members of the mustelidae, bff are long, slender animals that average 18 to 24 inches in length. Black-footed ferrets weigh 1½ –2½ lbs. Female ferrets are “jills”, males are “hobs” and juvenile ferrets are “kits”. The average life span of a black-footed ferret in the wild is 1–3 years. Continue reading “Black-Footed Ferrets: Back from the Brink”

Digging Up More Clues in the History of the Black Death

Bubonic plague victims in a mass grave in 18th century France. By S. Tzortzis [Public domain], via Wikimedia Commons
Bubonic plague victims in a mass grave in 18th century France. By S. Tzortzis [Public domain], via Wikimedia Commons
My last blog post on the Black Death highlighted research that suggested that the reintroduction of Yersinia pestis, the causative agent of the pandemic, originated in Europe during the 14–18th centuries rather than from Asia, the hypothesized origin. In my post, I wrote about my curiosity regarding what an Asian skeleton positive for Y. pestis from that same time period would reveal about the strain or strains that were circulating. Well, a team of researchers has been exploring the issue of strain circulation and an Asian connection, and recently published what they gleaned from additional historic Y. pestis samples in Cell Host & Microbe.

Teeth from 178 individuals in three different locations (two European, one Asian) were screened for Y. pestis infection using the plasminogen activator (pla) gene. Continue reading “Digging Up More Clues in the History of the Black Death”

The Black Death: World Traveler or Persistent Homebody?

Spread of the Black Death. By Timemaps (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons.
In the last six years, researchers have untangled the origins of devastating human plagues, sequenced the genome of a Yersinia pestis strain responsible for the Black Death and explored how long this bacterium has been with humans. However, the information arising from this research begs more questions. How many variations of Y. pestis occurred during the 14–17th centuries, the second pandemic that began with the Black Death? Did these differences reflect the location in which the Y. pestis-positive skeletons were found? What were the geographic source or sources of these plagues? A recent PLOS ONE article examined Y. pestis found in German remains separated by 500km and 300 years to answer to some of these questions. Continue reading “The Black Death: World Traveler or Persistent Homebody?”

Yersinia pestis Reveals More Secrets From the Grave

Yersinia pestis. By A.Myasnikov for Wiki (Self made work) [CC0], via Wikimedia Commons
Fridays are generally reserved for fun posts to share prior to the weekend. As we all know, fun is relative and to me, the latest news about how long Yersinia pestis has been entwined with human history is intriguing. I enjoy writing about the latest historical finding of Y. pestis even if I do earn a black reputation among my blogging colleagues (pun intended). Therefore, as soon as I saw the Cell article about Y. pestis found in Bronze age human teeth, I knew my blog topic was at hand.

Y. pestis has long been suspected in several plagues that occurred in the last two millennia. Publications in 2011 and 2013 used DNA extracted from teeth of human remains dated to the 14th century Black Death and 6th century Plague of Justinian to confirm Y. pestis was the causative agent in those devastating plagues. These results beg the question: How long has Y. pestis been infecting humans? The phylogenic trees generated from recent studies suggested Y. pestis has been with humans for as little as 2,600 years and as long as and 28,000 years. Equipped with these DNA-based tools, Rasmussen et al. asked if they could find evidence of Y. pestis in older human remains. Continue reading Yersinia pestis Reveals More Secrets From the Grave”

The Intersection of Plague and National Parks

Plague cases in the United States over 42 years. Copyright Centers for Disease Control and Prevention.
American national parks have spectacular scenery enjoyed by hikers worldwide. It’s one way people can enjoy some of the preserved wild places in North America. Due to this intersection of humans and wild animals, a bacterium that is endemic to the southwestern United States has infected a few humans after trips to Yosemite National Park, sparking many news headlines about the plague and closure of a few camping sites for chemical treatment to reduce local flea populations. In total, this summer has seen six cases of infection and unfortunately, three deaths from the plague. Continue reading “The Intersection of Plague and National Parks”

All You Need is Pla (for Pneumonic Plague)

Yersinia pestis. By Mrs Robinson at bg.wikipedia (Transferred from bg.wikipedia) [Public domain], from Wikimedia Commons.
Writing about Yersinia pestis or the Black Death, has earned me a reputation among Promega Connections bloggers. I am interested in what researchers have been able to piece together about the causative agent of ancient plagues, what modern research shows about how Y. pestis spreads in the body and the continuing reservoirs in modern times, resulting in publication of eight blog posts on the subject. Understanding Y. pestis bacterium is of continuing interest to researchers. How did Yersinia pestis evolve from the humble Yersinia pseudotuberculosis, a pathogen that causes gastrointestinal distress, into a virulent pneumonic plague that is a global killer? One strategy for answering this question is to look at the genomic tree of Y. pestis and trace which strains had what characteristics. In a recent Nature Communications article, Zimbler et al. explored the role of the plasmid pPCP1 in Y. pestis evolution and the signature protease Pla it expresses. Continue reading “All You Need is Pla (for Pneumonic Plague)”

Tracking the Beginning of a Pathogenic Bacterial Infection

Yersinia pestis by U.S. Center for Disease Control [Public domain], via Wikimedia Commons.
Understanding the course of a pathogenic infection involves not only understanding what ultimately kills the host or how the bacterium or virus enters the body but also how it establishes itself in the host organism. What is the receptor that allows a virus to enter the cell? Which cells does a bacterium first target or how does it evade an immune response? While other studies of bacteria like Yersina pestis have looked at imaging the bacterial burden in model mice, questions remain about how this bacterium gets from the skin after an infected flea bites to the draining lymph nodes, where the bacteria replicate and enter the bloodstream and infection becomes fatal. A recent PLOS Pathogens article examined how the nonmotile Y. pestis disseminated itself starting from a tiny innoculation mimicking a flea bite on a mouse ear and following pathogen interaction with the host from skin to lymph node. Continue reading “Tracking the Beginning of a Pathogenic Bacterial Infection”