Malaria and foot odor-the missing link!

Via Gawker.com and the LA Times, here’s a news alert that all college students should be mindful of. Researchers at the London School of Hygiene and Tropical Medicine have published in the medical journal PLOS One a new defense against malaria transmission. Malaria is a disease which affects a large proportion of the world’s population, with an estimated 220 million cases (nearly 1 in 20 people) worldwide in 2010. It is caused by the several species of the protozoan genus Plasmodium, and transmission requires specific species of mosquitoes that are essential for the life cycle of Plasmodium. There are treatments for malaria that can help infected patients to clear the parasite, but there is currently no vaccine. Main methods for control for the transmission of malaria have traditionally focused on controlling the reproduction of mosquitoes.

The experiments conducted by the researchers were simple; new adult female mosquitoes were fed human blood which was either infected or uninfected with Plasmodium. Following verification of infection, mosquitoes were introduced to socks (20 Den panty sock, HEMA, The Netherlands) that had been worn for 20 hours beforehand

…by a male volunteer of whom the relative attractiveness to An. gambiae s.s. compared to 47 other men is known…

Control socks, of course, were fresh right out of the package. The researchers constructed a mesh matrix, and measured the rate at which the mosquitoes landed on the matrix (landing rate).

As can be clearly noted from their data figure, infected mosquitoes were 4 times as likely to be attracted to the human odor than uninfected mosquitoes. The authors conclude that the presence of Plasmodium is altering the behavior of the mosquitoes, which may increase the rate of transmission as the population of infected vectors (the mosquitoes) rises. They suggest that current mathematical models for malaria transmission may be underestimating the rate at which the protozoan spreads through populations, as generally uninfected mosquitoes are used in behavioral studies and do not take into account the effects of the parasites themselves on vector-host interactions. Effective malaria control programs need to accurately model all aspects of parasite/vector/host interactions.

From the point of view of the pathogen (Plasmodium,) this is a perfect strategy. Plasmodium species depend upon the mosquito vector for the sexual portion of their life cycle, and this requires approximately 2 to 3 weeks to occur. As this occurs, it is advantageous for the organism not to be transmitted to a new host during a blood meal. However, after sexual maturation has occurred and the new sporozoites migrate to the salivary glands of the mosquito, modification of behavior will allow the subsequent transmission back into a new host during as the mosquito feeds. Long time fans of BIO230 will recall how another Apicomplexan protozoan, Toxoplasma gondii, has been found to potentially modify its host’s behavior, leading to the inappropriately named “Crazy Cat Lady Syndrome.”

Synergism in action: co-infection of a yeast and a bacterium

C. albicans (pink) in murine kidney. Image copyright D. Singleton, YCP

An article in the latest issue of Infection and Immunity caught my attention: “Candida albicans-Staphylococcus aureus Polymicrobial Peritonitis Modulates Host Innate Immunity” describes work by researchers at the Louisiana State University Health Science Center. Many models of infectious disease use virulence studies in animals such as mice. A typical experiment may infect an animal with a defined number of pathogenic organisms, and changes in health of the animal are measured–this is the basic premise of Koch’s Postulates, where the etiologic agent of a disease can be experimentally determined. Some diseases of humans may not be well mimicked in animal models, and this presents a problem when trying to study significant human diseases.

The work summarized here examined the disease produced by two separate pathogens, the Gram positive bacterium Staphylococcus aureus, and the fungus Candida albicans. Infection of mice with either one of these pathogens was non lethal at the infectious doses used in their experiments. However, when an animal was co-infected with both the bacterium and the fungus at the same time and at the same individual dose, a 40% mortality rate was observed, with significant infiltration of the organisms into the peritoneum and other target organs. At the same time, a number of important immune system signalling hormones were also elevated in mice who were co-infected with both pathogens, leading to a much higher inflammatory response in those animals. Mice treated at the same time with the inflammation inhibitor indomethacin did not die. Further injection of mice with a second inflammatory medidator prostaglandin E2 at the same time as administering indomethacin overrode the protective effects of indomethacin, and significant mortality of mice was again observed. The authors conclude that combination of pathogens have very important effects on the innate immune response, and that the lethality of the disease is exacerbated by the powerful inflammatory response.

Nosocomial infections are a critical issue in US health care, with billions of dollars annually being adding to the total costs of our health care. The graphic to the left from our textbook illustrates the relative contributions of various classes of pathogens; the sections of the pie labeled “Gram-positive bacteria” and “Yeast” are comprised primarily of the two species in this report, S. aureus and C. albicans. Many of the organisms responsible for causing nosocomial infections do so due to the a perfect storm of conditions in health care–a population very susceptible individuals, healthy carriers moving between patients, use of antibiotics leading to resistance, medical procedures which can bypass normal routes of entry for these pathogens. The first inclination upon developing a nosocomial infection is to combat it with antibiotics, and in fact many surgical procedures may involve the prophylactic use of antibiotics to help avoid this outcome. But the use of antibiotics themselves can lead to problems in the form of rampant antibiotic resistance and loss of efficacy of those drugs. This research shows that an alternative approach that tweaks the host’s immune response might also be effective.

GOT TOXINS? SOAK ‘EM UP WITH SCIENCE!

Constance Heidel (3 PM Micro) found an article about nanosponges via the science blog Live Science. This technology has the possibility of adsorbing things like toxins, bacteria, and viruses from the body using artificial microscopic devices (nanosponges) directly from the bloodstream. Here is Constance’s take on this topic:

She blinded me with science!

There was a motion picture released in 1966 called “Fantastic Voyage” that is considered one of the best science-fiction films ever made. While the movie may not be visually stunning (compared to today’s CGI-driven films), it is a truly in a league of its own in terms of conceptual brilliance.

Plot: A failed assassination attempt leaves a scientist in a coma. In order to save him, a task force is assembled upon The Proteus, a submarine. Then the crew and submarine are reduced to microscopic size and injected into the scientist’s bloodstream in order to operate on the surgically inaccessible clot in his brain using a laser. This team travels throughout his bloodstream, marveling at the wonders of the human body at a microbiological level. They must reach the brain within 60 minutes or else the effect will wear off and they will return to full-size. To further complicate things, the voyage is being compromised by a crew member who is a saboteur and is prepared to risk everything to stop the mission.

While the concept of shrinking a crew and submarine down to a microscopic level is definitely better left to science-fiction books and films, there are concepts and themes in the movie that were way beyond its time and are relevant today. Analogously to this film, scientists continue to wage biochemical wars within the human body in order to diagnose, treat and cure. Alas, there is a new battle looming on the horizon!

“I don’t know what’s causing it. Virus, bacteria or evil spirits, but I’m trying to find out.” – McCoy, Star Trek: The Deadly Years (Season 2, episode 12, 1968)

Dammit Jim, I’m a doctor not a scientist! 

Don’t worry about it, Bones. The researchers at the University of California, San Diego have it all under control. They have invented a nanosponge which is capable of safely removing a broad range of toxins from our blood stream. Most antidotes or treatments against venoms, bacteria or bioweapons are targeted to counteract a specific molecular structure, like a lock and key mechanism. These nanosponges are more like a like a skeleton key. They work by absorbing pore-forming toxins, regardless of the toxins’ molecular structure. So it doesn’t matter if it is a virus, bacteria or evil spirits… these nanosponges are coming in there to eradicate them.

Liangfang Zhang, a nanoengineering professor at the UCSD Jacobs School of Engineering stated, “Instead of creating specific treatments for individual toxins, we are developing a platform that can neutralize toxins caused by a wide range of pathogens.”

Nanosponges: Troops against toxins

The word “sponge” doesn’t exactly conjure up images worthy of villains as epic as Darth Vader, but trust me… these aren’t your average loofahs. These microscopic sponges are sheathed in a suit of armor made of red blood cells. It is this design that allows the nanosponges to act as decoys and destroy.

Cross section of nanosponge)
(Photo Credit: Zhang Research Lab)

By using a centrifuge, Zhang’s team is able to separate red blood cells from a sample of blood. The cells are then put into a solution that causes them to lyse. This releases the hemoglobin and leaves the skin of the RBCs behind. At this point, the globular nanoparticles (which are made of a biocompatible polymer core) are mixed with the skins until they’re fully cloaked with the red blood cell membrane. This cloaking allows the nanosponges to be undetected to the immune system and serve as a decoy to absorb the toxins away from their cellular targets. Unlike a red blood cell, the nanosponge’s center is made of lactic acid. This organic material acts like a scaffold to keep the membrane from falling apart once the toxins are trapped.

Each nanosponge is approximately 85 nanometers in diameter and they are 3,000 times smaller than that of a red blood cell. Scientists only need the membrane from one red blood cell to synthesize thousands of nanosponges. This is the stuff science fiction films are made of: “In a single dose, an army of nanosponges will be deployed to conquer your bloodstream. They will evade your immune system, outnumber your red blood cells, intercept toxins and deliver them to your liver in order to save your life!” The coolest part is, this is science NON-fiction!

To see a nanosponge in action, check out this video:

The war wages on…

The efficacy of this treatment was demonstrated through a study in mice. A lethal dose of MRSA was given to the mice, which normally causes acute death. The control group didn’t receive any treatment and all of the mice died as expected. When nanosponges were injected two minutes before the toxin was administered, an overwhelming number of mice survived – 89 percent. When the nanosponges were administered two minutes after the lethal dose was administered, an impressive amount – 44 percent – survived. Surviving mice were studied further and it was shown that the nanosponges accumulated primarily in the liver and were safely metabolized without any damage. Studies also showed that the nanosponges also have a half-life of about 40 hours. These results were published in Nature Nanotechnology.

The most virulent toxins in MRSA were used in the experiments with great success. It can be deduced that toxins with lower virulence factors would have an even higher success rate. These nanosponges are capable of removing a broad class of dangerous substances from the bloodstream including toxins produced by E. coli, S. aureus, venom from snakes, bees, sea anemones and more. With more and more strains of bacteria becoming resistant to antibiotics, nanosponges could work with or in lieu of most antibiotic treatments that are being prescribed today.

The goal of these experiments is to lead to approved therapies on human patients as soon as possible. Before that can happen, the researchers’ must pursue clinical trials. Follow this “fantastic voyage” on Twitter @UCSD_Nanomed for the latest on this promising technology!

Automobile fuel from E. coli

An automobile engine partly opened and colored to show components. (Photo credit: Wikipedia)

An article in the New Scientist caught my eye this morning, “Bacteria churn out first ever petrol-like biofuel,” which is a popular press summary of an article recently published in the Proceedings of the National Academy of Sciences. I’ve written about the challenges of using microorganisms as sources of biofuel previously, but the problems with using microorganisms are two-fold; first, the process is most useful if the organism can utilize a carbon source which is available in large amounts and is poorly degradable on its own such as cellulose, and second, the process should generate the most useful potential fuel product possible, and the organism should stop any further metabolism at that point. Ethanol is a common endpoint for many fermentation processes, and is something that is readily generated in large scale industrial processes. Unfortunately, biological production of ethanol as a fuel requires the further purification of the ethanol before it can be used, and the purification process uses energy as well limiting the net energy obtained in the procedure. Current production of other fuel additives by bacteria generate products that can be used in internal combustion engines, but not effectively, and they tend to degrade the engine over time. It would therefore be highly desirable to enable bacteria to biochemically synthesize hydrocarbon molecules which are identical to the ones used in petroleum-based fuels.

Figure 1 from Howard et al. White indicates E. coli genes, Green indicates B. subtilis genes, Red indicates P. luminescens and N. punctiforme genes, and Blue indicates C. Camphora genes

Researchers at the University of Exeter developed an artificial biochemical pathway in E. coli by introducing a number of genes from other microorganisms related to the synthesis of long chain hydrocarbons. E. coli on its own will produce long chain fatty acids, but these are not useful end products for use as a biofuel. Introducing genes related to fatty acid biosynthesis from two other bacteria, Photorhabdus luminescens (see this article for my story of this organism in a completely different context) and Nostoc punctiforme, which allowed E. coli  to use its existing fatty acids to produce branched chain alkanes. Genes introduced from Cinnamomum camphor (a plant), and Bacillus subtilis (another bacterium) were used to enable E. coli to produce the fatty acids which were best able to enter the new pathway for forming fuel molecules.

The authors demonstrated by several analytic methods that production of industrially relevant long chain alkanes was accomplished by the introduction of these genes into E. coli. Future directions for the research are several fold. First, the process must be scaled up in order for it to be useful. Second, this process started with glucose as the initial carbon source, which is energetically costly to produce in itself. Third, the process laid out in the flow chart to the left is not terribly efficient; altering the expression of various components may force the pathway to be more efficient, but this leads to another problem. Long chain alkanes are extremely hydrophobic and will actively disrupt membranes they come into contact with. Organisms that produce these compounds would additionally need to be able to resist the effects of the toxic compounds they produce.

The normal microbial flora of Bigfoot

Stories of fantastical creatures such as Bigfoot continue to capture the American imagination. Reports come in frequently detailing otherworldly encounters that cannot be explained by science alone. Fragmentary sightings and incomplete evidence do little to bolster support for the existence of Bigfoot, however the recent sequencing of the Bigfoot genome and close-to-home encounters raise enthusiasm for some armchair conjecture about the Biology of Bigfoot. In particular, we can make predictions as to the makeup of the intestinal microbial flora of Bigfoot, and develop the tools in order to characterize these organisms.

Recently, York College Biology faculty and students returned from the Pennsylvania Academy of Sciences annual meeting, held in Bradford, PA–near the epicenter of Pennsylvania Bigfoot sightings. YCP Senior Rob Harvey spent some time in the field looking for physical evidence, and has shared his experiences. His photographic evidence presented here leaves little doubt that something lives in the woods near the Pennsylvania/New York border.

The normal intestinal microbial flora of animals plays a critical role in maintenance of health, both by producing metabolites that might not be included in the diet, and by helping to prevent the overgrowth of pathogens. The flora of humans can change over time, as the interactions between our cells, normally non-pathogenic microbes, and disease-causing organisms constantly shifts. The types of organisms are also determined by diet in different animals, with strict herbivorous animals having a defined type of microbial flora, while carnivores will have a different flora.

Bigfoot is probably not a plant eater

The diet of Bigfoot can be inferred from the photographic evidence presented here; the complete dismemberment of the skeletal remains strongly suggests the makeup of Bigfoot’s diet. This in turn implies that the microbial flora of Bigfoot will have much more in common with the polar bear and the Komodo dragon than the domesticated cow. Further characterization of Bigfoot’s intestinal microbiome awaits biological samples. However, the scarcity of studies of the microbiome of carnivores tells us that obtaining samples is potentially dangerous fieldwork.

Rob’s pocket multitool next to a mysterious footprint

Rob will continue his field studies and will hopefully bring back to the YCP Microbiology Research Labs an elusive “scat” sample that will help us to characterize Bigfoot’s intestinal flora. We will use these samples for DNA isolation and Polymerase Chain Reaction amplification, using primers to amplify the evolutionary conserved ribosomal sequence. Amplification using eukaryote specific primers directed against the 18S gene will allow us to characterize fungal and protozoan inhabitants of Bigfoot’s colon, as well as to rapidly confirm that it is a sample actually from Bigfoot by comparing with the now-published Bigfoot genome. Amplification using prokaryotic specific primers directly against the 16S gene will allow us to characterize Bacterial and Archaeal inhabitants, which will help us to create a complete picture of Bigfoot’s unseen passengers.

Who’s Side Is Our Microbiota Really on When It Comes to Viruses?

Samantha Yohe (3 PM Micro) found a review article which further examines the beneficial role of the normal microbiota. In class, we described how these organisms can compete for nutrients with pathogenic microorganisms, and since they for the most part are better at doing this than pathogens, they can keep other bacteria, fungi, etc. from growing well. However, this model doesn’t really do much to explain the developing role of the normal microbiota in helping to prevent viruses from infecting us, since viruses do not need to compete for nutrients on their own. Here is Samantha’s summary:

Figure 1 from Wilks and Golovkina; overall stimulation of the immune system occurs due to the presence of the normal bacterial flora

After reading the article, Influence of Microbiota on Viral Infections from the NCBI website one isn’t sure about their resident microbiota’s intentions. Are these intentions good or are they bad?

Our normal flora is a significant variable when it comes to our current state of well-being. This flora has the opportunity to aid in the protection of our health against viral pathogens and much more. Microbiota coats the entry-ways of our body including skin, mucous membranes, and so on. It shows microbial antagonism making it difficult for a virus to wreak havoc on our system due to such an unwelcoming environment for the virus to flourish. But, our flora can have even more effects that help protect us from such infectious agents. One example from the article is that of mice and their susceptibility to the Influenza A virus. It was shown that mice treated with antibiotics that caused depletion of their natural commensals were more susceptible to the virus than those that were left untreated. This protection seen by commensals seems indirect according to researchers. The reason being is that the resident flora causes the release of inflammasome which in turn initiates migration of T-cells, the immune systems natural response to such infection.

The “dark side” to microbiota can show direct assistance in viral replication when looking at mice infected with oral poliovirus. In the article, mice were infected with poliovirus and some were treated then with antibiotics while others were left to fend it off with the aid of their normal flora. Results showed that those treated with the antibiotic had less of a mortality rate than those that were not. They also found that those mice treated by antibiotics still released the virus but its transmission ability was reduced. Researchers also found in their study that 3 viruses from 3 different families depended heavily on resident bacteria within the gastrointestinal tract of mice in order to reproduce. This quandary proposed another question to the researchers as far as human viruses go. HIV-1 is spread across our mucous membranes which are composed richly of commensal bacteria. Researchers question whether or not HIV-1 may be using our own flora to reproduce and transmit itself much like that of the poliovirus in mice.

The same researchers in this article also found that Mouse Mammary Tumor Virus (MMTV) uses immune response of Toll-receptors within the body of the infected mouse to create immunity for itself. MMTV was able to create its own immunity by taking advantage of the tolerogenic qualities of the normal flora of the mouse.

Now and for the rest of time clinical fields must remember the multitudes of bacteria that take up residence on and within our bodies and their interactions with numerous agents they come into contact with.  The interactions going on between our very own microbiota and these possible pathogens could mean the difference between protection and infection.