But it was just a dip in the lake: a look into the parasitic disease Schistosomiasis

by KS#1

You know the feeling you get after a Thanksgiving meal when your stomach is so full it makes your abdomen appear to protrude with a “food baby?”  Now imagine that same feeling, without being full.  In fact, imagine it while feeling starved, malnourished, and dehydrated.  These are a few of the symptoms of schistosomiasis; a disease caused by eukaryotic microbes from the Schistosoma genus. Why should we care?  Let’s imagine for a minute that we are 8 years old again. The summer temperature is scorching and we are craving nothing more than a dip in the lake out back.  Now, here in the US and in other highly developed countries, that would be fine.  However, in some regions of Africa, our 8 year old selves have just subjected our bodies to possible infection and subsequent schistosomiasis. Schistosomiasis is one of the most infectious parasitic diseases in the world, second only to malaria (1). Approximately 240 million people are infected each year (2), most commonly through unsanitary conditions and contaminated fresh water sources.  Unfortunately, that includes most lakes and rivers in southern and sub-Saharan Africa. Even the Nile River has been known to play host to the infectious larvae of schistosomes (1).  It should come as no surprise then, that children are the most commonly infected age group, as they are the most likely to play in contaminated waters. 

Figure 1: The life cycle of Schistosomes.  The human is the location of

 the adult blood fluke.  The fluke then lays eggs which are excreted into the

 environment to hatch into miracidium.  These miracidium can then  infect

 snails, where transformation from miracidium into sporocytes can occur.

  The sporocytes give rise to cercariae (the larval stage) which can swim

 freely in fresh water to infect humans through skin penetration.

Of clinical isolates, the two most commonly isolated schistosomes are Schistosoma haematobium and Schistosoma mansoni, both found in warmer climates with most infectious cases deriving from African populations (1).  The life cycle of these blood flukes is fairly simple, rotating between the human – where the adult fluke is found – and the snail, the intermediate host (3). The blood fluke miracida (the pre-larval hatched form of Schistosomas) infect snails where the fluke transforms into sporocysts.  These give rise to cercaria (infectious larvae) which can then survive in fresh water to infect humans through skin penetration.  Now, our bodies are well equipped to battle most pathogens, and if the initial burrow site causes any inflammation, the cercaria are destroyed by various immunological pathways.  Unfortunately, should our bodies not react to the initial infection, the cercaria make their way to the lungs or liver, where they develop into the adult form.  It is from there that they migrate into the intestinal (S. masoni) or urinary (S. haematobium ) tracts to lay their eggs.  The eggs are then excreted back into the environment to hatch into miracida and the cycle begins again (1, Figure 1).   

Going back to our example, simple childhood tendencies have given rise to a blood fluke navigating its way through our bodies. What does this mean as a patient? We can expect to develop a rash at the site of infection which is typically mild and often goes untreated.  In 1-2 months the symptoms have progressed and we begin to experience fever, chills, cough and muscle aches - common influenza symptoms.   Since viral infections pass, no drastic action is taken and only the symptoms are treated. A year or so later, we now experience abdominal pain, difficulty passing urine, and blood in the stool or urine.  These symptoms clearly indicate something is wrong and a trip to the doctor is arranged. The doctor sends urine and stool samples to the lab to check for the presence of eggs and sends a blood sample for serological analysis.  The urine and blood tests come back positive for infection with S. haematobium.  In some rare cases, eggs can be deposited in the brain or nervous tissue which can lead to severe migraine-like headaches, sporadic paraphasia, and brain lesions.  In such a case, diagnosis may need to occur through surgical excision of the lesions and biopsy (4).  Luckily, this time the fluke appears to have settled solely in the urinary tract. The doctor prescribes Praziquantel, the only anti-helmintic medicine available to treat helminthes infections.  Symptoms subside and diagnostic tests reveal we are no longer infected with the parasite. 

Great! Right…? Well, yes, but there are drawbacks to this route of treatment.  Unfortunately, Praziquantel is only a treatment, not prevention.  Subsequent infections may still occur upon exposure to more contaminated water.  Currently, there is ongoing research to find a suitable candidate for vaccine production against these parasites in hopes of combating this truly unfortunate disease.  Most recently, Lochmatter et al. discovered that immunization of mice with the first extracellular domain of SmTOR (S. mansoni tetraspanning orphan receptor) led to a decrease in adult worm burden.  Immunization also led to the production of anti-rSMTORRed1 (the first domain name) antibodies which may act as a memory response to any further inoculation with the parasite (5).  Lochmatter et al.’s paper is set to be put to print in December 2012 so currently no data on re-inoculation is available. 

So what can be done in the meantime?  Prevention is most successful through avoiding any interaction with contaminated waters; just a splash can cause infection if the skin is weak or already injured.  If contaminated waters are the only water source in the area, small amounts should be boiled for at least 1 minute and cooled before consumption or bathing. Control of the snail populations can also be an effective measure of prevention. However, any chemical treatments of contaminated waters may harm other species in the area, and if not continued, could allow re-inhabitation of the snails (1).  While we wait for a better solution, the best that community education can do is inform the public about these parasites and the subsequent disease, and hope that parents don’t let their children go for that dip in the lake.

References

1.     Global Health – Division of Parasitic Diseases and Malaria. Parasites – Shistosomiasis. Centers for Disease Control and Prevention.  Last updated 7 November 2012.  Accessed 14 November 2012.

2.     World Health Organization. Schistosomiasis. 2012. Accessed 14 November 2012.

3.     Mitreva, Maedonka.  The genome of a blood flue associated with human cancer. Nature Genetis. 27 January 2012. 44:116-118.

4.     Imai, Kentaro; T. Koibuchi, T. Kumagai, T Maeda, Y. Osada, N. ohta, M. Koga, H. Nakamura, T. Miura, A. Iwamoto, and T. Fujii.  Cerebral schistosomiasis due to Schistosoma haematobium confirmed by PCR analysis of the brain specimen.  Clinical Journal of Microbiology. October, 2011. 49(10):3703-3706. 

5.     Lochmatter, C.; C.L. Schneider, K. Ingram, J. Keiser, and J.A. Schifferli. Schistosoma masoni tetraspanning orphan receptor (SmTOR): a new vaccine candidate against schistosomiasis. Clinical & Experimental Immunology. 1 November 2012 (online publication, set for release in print December 2012).  170(3):342-357.

Heteromita globosa: The Antarctic Sewer Scrubber

Heteromita globosa and its flagella

by AB

Antarctica is home to icebergs, penguins, and…soil flagellates? With average temperatures as low as -80°F and no trees, flowering plants or nutrients, it is difficult to understand how any microorganism could survive in such a cold environment.  Studies show, however, that Antarctica is home to a range of terrestrial microbiota called psychrophiles that can operate at extremely cold temperatures.  These microorganisms not only survive the cold temperature fluctuations, but they fulfill important functions such as maintaining other microbial populations and preventing biofilm build-up. According to H.G. Smith, the microbiota that exists in this environment consists of those that can adapt physiologically in order to survive, grow, and reproduce in unfavorable climates (1).

The “small (5-20 Ixm), nonpigmented bacteriophagous heterotroph” Heteromita globosa is the most prevalent protozoan soil flagellate in the fell-fields of Antarctica (See Figure 1) (2). H. globosa implements a unique form of feeding and locomotion in which its flagella produces currents to bring in essential nutrients and swim from place to place. While these psychrophiles perform optimally at temperatures as low as 1.5°C, cold temperature-induced encystment, or enclosure in a cyst form, occurs below 1.5°C and excystment, or breaking out of the cyst, occurs slightly above 1.5°C (See Figure 2). Due to the extreme temperature fluctuations and thermal periods in Antarctic terrestrial environments, H. globosa can readily adapt, allowing them to survive the freeze and thaw cycles (2).

Heteromita globosa in a cyst

The combined effort of this organism’s psychrophilic adaptations for excystment and encystment, ability to feed off nutrients brought in by the flagella, and mobility make it successful.  Compared to other microorganisms of the same environment, H. globosa confers “greater mobility, growth rates and synchrony of temperature-induced excystement at low sub-optimal temperatures”, or temperatures below 1.5°C (2). From a practical perspective, H. globosa is a huge consumer of bacteria in biofilm and microbial communities.  This trait makes it an important component of biogeochemical cycling in the ground waters of Antarctica as well as a source of carbon transfer and nutrient regeneration (3).

In order to conserve this cycle of encystment and excystment, H. globosa implements specific mechanisms to maintain the fastest growth while competing with similar microorganisms (3). In a study, H.G. Smith compared the population growth rates of H. globosa with the ciliated Protozoa Colpoda cucullus.  While C. cucullus has not been isolated in the Antarctic zone, like H. globosa, it can survive in extremely dry and cold temperature-fluctuating conditions.  When growing H. globosa at sub-optimal temperatures, it was found that the growth rate was slower in conditions favorable to other soil flagellates. Comparing these low temperatures to C. cucullus showed that this organism was not able to withstand the same temperature fluctuations as H. globosa. In fact, C. cucullus could not grow in temperatures below 5°C while H. globosa grew in temperatures slightly lower than 1.5°C. The fact that H. globosa was able to withstand these cold temperature fluctuations demonstrates its versatility as a microorganism. Compared to other microorganisms that are found in similar environments, H. globosa has the mechanisms to best adapt to the Antarctic environments, making it a microbial force to be reckoned with.

In addition to housing the mechanisms needed to survive the frigid seasons in Antarctica, H. globosa is a significant biofilm reducer in aquifers at cold temperatures.  As previously stated, protozoan soil flagellates are the primary consumers of bacteria not only in Antarctica but in several environments. Bacteria clog the tiny pores spaces in aquifers inhibiting sewage disposal, “microbe-enhanced oil recovery, groundwater recharge, and in situ bioremediation” (4). They form biofilms in these pores by expelling exopolymer slime, creating insoluble biogas, and gathering into a biomass.  H. globosa grows in contaminated aquifers along with bacteria, producing nutrients that “stimulate bacterial metabolism” in order to cause biodegradation (4). H. globosa reverses the effects of bacterial biofilms by grazing on these biofilms and increasing porosity and permeability in these aquifers. In doing this, they induce bioremediation, or removal of pollutants, inhibiting the biofilm-forming bacteria from clogging the pores.

These findings have prompted environmental researchers to consider H. globosa as an important mediator of biofilm reduction.  By studying the relationship between bacteria and protozoan soil flagellates like H. globosa, new trategies that increase the effectiveness of these aquifers in cold regions like Antarctica can be improved.  It has been found that the bacterivorous protozoa like H. globosa “coexist with bacteria [by] thriving on organism contaminants on the subsurface” (4). This method of feeding allows H. globosa to remineralize components that bacteria generate, causing biodegradation and destruction of biofilms produced.  This is a huge advantage to bioremediation projects including maintaining hydrolytic conductivity in aquifers that are normally clogged with bacterial biofilms.  By inducing aquifers with H. globosa as well as other protozoan soil flagellates, bacterial biofilms will be reduced, maintaining hydrolytic power and proper sewage disposal.

While it is difficult to understand why anything would prefer to inhabit extremely cold, temperature-fluctuating regions and live in sewage systems, evidence shows that H. globosa contains the microbial machinery to thrive in this type of environment. Its unique flagellar feeding mechanisms, psychrophilic behavior, and ability to degrade bacterial biofilms enable it to be the most prevalent protozoan soil flagellate in Antarctica. So while most Antarcticans will spend the winter season in front of the fireplace, H. globosa will be scrubbing the sewers.

References:

1. H.G. SMITH . 1996. Diversity of Antarctic terrestrial protozoa. Biodiversity and Conservation (5). [cited 2012 Nov 15] 1379-1394. Available from: http://www.springerlink.com/content/t2xr52876rl78j67/fulltext.pdf?MUD=MP
2. H. G. Smith a1, J. Hughes a1 and S. J. Moore a1 . 2004. Growth of Antarctic and temperate terrestrial Protozoa under fluctuating temperature regimes. Antarctic Science. [cited 2012 November 15] Volume 2 / Issue 04 /pp 313-320. Available from: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=222941
3. Denis V. Tikhonenkov 1 and Yuri A. Mazei 2 . 2006. Heterotrophic flagellates from freshwater biotopes ofMatveev and Dolgii Islands (the Pechora Sea). Protistology (4) [Internet]. [**Last Updated**, cited 2012 November 15] (4), 327337. Available from: http://www.egf-penza.ru/kaf/zoo/mazei/pdf/32.pdf
4. Richard G. Mattison, Hironori Taki, and Shigeaki Harayama. 2002. The Bacterivorous Soil Flagellate Heteromita globosa Reduces Bacterial Clogging under Denitrifying Conditions in Sand-Filled Aquifer Columns. Applied and Environmental Microbiology. [cited 2012 November 15] 68(9): 4539–4545. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC124123/

Euglena gracilis: A Closer Look

by Tina Soltani

Take a deep breath. As you inhale, oxygen enters into your lungs and carbon dioxide is then exhaled. Organisms like us require this oxygen for our everyday function. Most of us are generally aware that oxygen comes from trees and plants. But what many people are probably not aware of is that many microbes are also responsible for the oxygen we breathe. Through photosynthesis, phytoplanktons, such as diatoms and dinoflagellates, and euglenoids, like Euglena gracilis, contribute to the oxygen supply found on Earth. E. gracilis’s ability to photosynthesize allows it to consume carbon dioxide and release oxygen, which we then breathe. With carbon dioxide levels rising every year and contributing to global warming, microbes, such as E. gracilis, are essential in combating this issue. A species as versatile as this deserves a more in-depth analysis. Now take another breath and read on. 

Euglena gracilis in its free-living flagellated state (8)    

Euglena gracilis are free-living flagellated protists and contain chloroplasts; they are not known pathogens. They are part of one of the most primitive eukaryotic groups, the euglenoids. They are primarily found in freshwater habitats, but they can also inhabit marine and soil environments. E. gracilis tends to favor more alkaline environments; neutral or acidic environments are not conducive for nutrition or reproduction, although they can withstand such conditions (1). An interesting fact about E. gracilis: it is both chemoheterotrophic and photoautotrophic, meaning that it can not only consume organic molecules around it but it can produce its own food source as well. As a chemoheterotroph, E. gracilis is able to utilize a number of organic molecules such as ethanol, lactate, glucose, lactose and malate as carbon sources. As a photoautotroph, it utilizes carbon dioxide as its carbon source when undergoing photosynthesis (2,3). One of the most fascinating attributes of E. gracilis is its reaction to light beyond food production. E. gracilis is well known for its ability to lose chloroplasts when grown under constant darkness conditions, but then regain this ability when exposed to light again. When grown in the dark, they lose their chlorophylls and the chloroplasts regress to form proplastids; upon exposure to light they can re-differentiate chloroplasts (3).

There is no known sexual reproduction in E. gracilis. They usually reproduce by longitudinal binary fission in either a free-swimming or encysted state. If conditions are favorable, reproduction usually occurs in the free-swimming state, whereas if the environment is too hot or lacks water or the proper nutrients, E. gracilis resorts to an encysted state and remains that way until conditions become favorable again (1). The genome of E. gracilis has not been fully mapped yet. There has been difficulty conclusively classifying E. gracilis; they share similarities to protists, fungi animals and plants. Santos Ferreira et al were able to determine using expressed sequence tags (ESTs) of E. gracilis cDNAs that about 61% of these ESTs had similarities with proteins of known function. A breakdown of the known 61% of ESTs revealed that these proteins have similarities to different group classifications – 36% protist, 21% plant, 2% animal, 1% fungi and 1% prokaryote (4). E. gracilis is thought to have an endosymbiotic relationship with green algae, possibly due to the consumption of a eukaryotic alga. E. gracilis is well suited for the study of endosymbiosis and endosymbiotic gene transfer (EGT) because its plastid was acquired by secondary endosymbiosis, but no remains of the endosymbiotic nucleus is present (5). Endosymbiosis (or primary endosymbiosis) is when an organism lives inside another organism or its cells. Secondary endosymbiosis, then, occurs when an organism engulfs another organism that has underdone primary endosymbiosis. This loss of nucleus from the algae suggests that E. gracilis has transferred key genetic material from these algae, and a separate nucleus within E. gracilis is no longer required. The occurrence of EGT makes it difficult to map out a phylogenetic tree, and is certainly the case for E. gracilis. Phylogenetic trees are designed to reflect scenarios of vertical evolution with descent from a single common ancestor; E. gracilis has two (5).

Current levels of atmospheric CO2 levels as

of October 2012 (9)

E. gracilis is also a key component in biological carbon dioxide fixation. Because of its high tolerance of carbon dioxide, E. gracilis is one of the many favorable microalgae considered for projects centered on carbon dioxide sequestration (6). Chae et al used E. gracilis as a model by which to study the effects of elevated carbon dioxide and how it affects the ability to photosynthesize. They found that E. gracilis could withstand an environment containing up to 40% carbon dioxide. E. gracilis can also convert carbon dioxide to oxygen at a much more rapid rate than some other photosynthetic microbes (2,7). This suggests E. gracilis as one of the possible solutions to global warming attributed by the increase in carbon dioxide emissions.

Experiments by Santos Ferreira et al and Chae et al are just the beginning in understanding the complexity of E. gracilis and how, despite extensive research, there is still much unknown regarding Euglena species. Further research in their genomic sequence can give scientists further understanding in how their genetic makeup has evolved over time and why it shares so many similarities to other types of organisms found in other kingdoms. It can also highlight at what point in time E. gracilis began its endosymbiotic relationship with green algae. Additional investigations in its ability to withstand such high amounts of carbon dioxide and still be able to function relatively well can offer a better understanding of a possible evolutionary adaptation to climate change. Because current carbon dioxide levels are progressively increasing, photosynthetic organisms like Euglena are crucial for carbon fixation. No matter what the future holds, thanks to Euglena gracilis, we can all breathe a little easier.

References:

1. Tannreuther, George W., 1922. Nutrition and Reproduction in Euglena. Zoological Library, University of Missouri. Mit 52 Textabbildungen, 367-383.

2. Euglena and Euglena gracilis. <http://en.wikipedia.org/wiki/Euglena> and <http://microbewiki.kenyon.edu/index.php/Euglena_gracilis>

3. Regnault, Annie, Francoise Piton and Regis Calvayrac, 1990. Growth, Proteins and Chlorophyll in Euglena Adapted to Various C/N Balances. Phytochemistry, Vol 29(12): 3711-3715.

4. dos Santos Ferreira, Veronica, Iara Rocchetta, Visitacion Conforti, Shellie Bench, Robert Feldman and Mariano J. Levin, 2007. Gene expression patterns in Euglena gracilis: Insights into the cellular response to environmental stress. Gene 389:136-145.

5. Ahmadinejad, Nahal, Tal Dagan and William Martin, 2007. Genome history in the symbiotic hybrid Euglena gracilis. Gene 402:35-39.

6. Ono, Eiichi and Joel L. Cuello. Selection of optimal microalgae species for CO2 sequestration. <http://www.netl.doe.gov/publications/proceedings/03/carbon-seq/PDFs/158.pdf>

7. Chae, S.R., E.J. Hwang and H.S. Shin, 2006. Single cell protein production of Euglena gracilis and carbon dioxide fixation in an innovative photo-bioreactor. Bioresource Technology 97:322-329.

8. Figure 1 http://www.britannica.com/EBchecked/media/5411/Euglena-gracilis

9. Figure 2 http://www.co2now.org

On Coccolithophores and Climate Change

by EG

Al Gore discussed in his famous novel, “An Inconvenient Truth,” the impending doom of global warming stating “there is an air of unreality in debating these arcane points when the world is changing in such dramatic ways right in front of our eyes because of global warming.”  Global warming is the effect of several different factors including the Earth’s natural cycle, but the most prominent factor is due to us: greenhouse gas emissions such as water vapor, CO₂, and methane.  This is understood by most who believe in global warming; however, many may not be aware that microorganisms play a large role in the global warming cycle.  Soil-dwelling anaerobic organisms emit two of the major greenhouse gases previously mentioned: CO₂ and methane.  Organisms that reside in the ocean play an even larger part, considering the ocean is about 70% of the Earth’s surface¹. These organisms have a positive role in global warming; they commonly use photosynthesis to live, therefore using CO₂ and respiring oxygen, aiding in reducing the CO₂ levels.  This is important because the total CO₂ emitted accounts for 9-26% of the greenhouse effect².

Figure 1. EHUX cell. Photo from

  Dr. Marcus Geisen and the  National

 History Museum

A few organisms may, however, cause production of CO₂ in oceans,
 such as Emiliania huxleyi. E. huxleyi, EHUX for short, is a Eukaryotic coccolithophore that is a single-celled phytoplankton covered with ornamented calcite disks³ (Figure 1). EHUX is unusual in that not only its shell but the soft section inside can be found in sediment. This is possible because it produces chemical compounds resistant to decomposition, known as alkenones. These alkenones can be found in marine sediment long after the soft section of the organism has decomposed, making it very useful to scientists to estimate past sea surface temperatures⁴

Figure 2: EHUX bloom seen from space

 in the Barents Sea off the coast of Russia.

 Photo from  Jeff Schmaltz from the

 NASA Earth Observatory.

EHUX is the most abundant coccolithophore in Earth’s oceans and is found everywhere except the polar regions. These blooms are formed in nutrient rich waters, causing an extremely anoxic environment, thereby killing marine wildlife and other microorganisms that reduce CO₂ concentrations. The continual shedding of their coccolith disks makes the oceanic blooms visible from space, as seen in Figure 2. EHUXs’ ubiquity causes these blooms to be quite massive, sometimes spanning more than 100,000 square kilometers (over 38,600 square miles), accounting for approximately 75% of the photosynthetic plankton in that area⁵. This may seem advantageous to have a 38,000 square mile area of photosynthetic organisms that take up CO₂ and respire oxygen, but these organisms also produce dimethylsulfoniopropionate (DMSP). DMSP turns into dimethylsulfide (DMS) which can cause dense clouds to form over the ocean, blocking the sunlight used by the photosynthetic bacteria. Not all sunlight is blocked, but nonetheless, the heating of the ocean may decrease over time if this were to happen continually, resulting in a decrease in loss of polar ice caps and ice mass inhabited by penguins, polar bears and other polar wildlife. Unfortunately, since EHUX is not found at the poles due to its extreme cold temperature, this would not have a great effect on these regions.

Several research experiments have been conducted using E. huxleyi as a model organism for changing ocean conditions and its effects. A study led by Robert Charlson claims that DMS, a source of cloud condensation, affects the reflectance of the clouds and therefore the Earth’s radiation and temperature. Charlson et al claimed that to counteract global warming due to an increase of atmospheric CO₂, an equal amount of DMS would be needed⁶. This seems reasonable but their research on this subject matter has many inadequacies; it is still unknown how climate affects DMS emissions, or how the microbes react to the changing climate⁶. It is also unlikely that massive blooms would have more advantages than disadvantages in terms of other marine life.

In addition to the Charlson et al research, a study done by Marion van Rijssel and Winfried Gieskes showed that in higher temperatures the cell size of E. huxleyi decreased, but the amount of DMSP generated per cell increased⁷. However, they found that there was a two-fold drop in DMSP produced by EHUX in the temperature range of 5-15^oC which is the normal temperature of the euphotic (uppermost) layer of water where EHUX is found⁷.  This evidence supports the claim that because of global warming, the euphotic zone will be the warmest, resulting in an increase of DMSP production, thus an increase in DMS production to create clouds.  An important note the authors make is that only a small fraction of the total DMSP produced by all algal blooms, not solely EHUX blooms, will escape to the atmosphere.  Even in the atmosphere it is not guaranteed to create a cloud and if it does, it would likely be a very small cloud not nearly large enough to offset the effects of the heated ocean as Charlson et al claimed⁷. It is clear that research with EHUX and its ability to create safe byproducts for humans, wildlife, and the environment is limited. As of now there is much left unknown but if further research continues to show promising results, this organism may be our answer to ridding ourselves of, or delaying the monster hanging over our heads: global warming.

Two and a half billion years ago oxygen began to accumulate on this planet and 200,000 years ago when anatomically modern humans appeared, we began to destroy it. As technology has improved, one would think that ways to combat or decrease the amount of greenhouse gases emitted would be apparent but instead we put billions of dollars into war and absurd campaign ads. Before we leave our children, grandchildren, and even great grandchildren with a doomed planet, we need to take necessary steps to improve our energy use. This means using nuclear, solar, and wind energy and not relying on coal and oil. Now, with new research and discoveries of microorganisms that do amazing things, we may see ourselves turning to microbial engineering in order to delay the Earth’s inevitable fate. Organisms such as E. huxleyi demand further research but look promising in supplying us with naturally found compounds that, unlike CO₂, may help our planet. There are still many unanswered questions: will massive DMS clouds pollute our air and cause sickness? Will massive EHUX blooms kill off marine life and therefore our seafood industry and a major source of coastal economies? What about the potential of other organisms in the ocean or in the soil? These organisms and these questions demand attention; but like science, there will always be more to learn. It is up to us and the next generations to call attention to this global crisis and use our resources to find answers to these questions

References

1.     National Oceanic and Atmospheric Administration.  “Ocean.”  Date Accessed: November 15, 2012.  http://www.noaa.gov/ocean.html

2.     Russell, Randy. “The Greenhouse Effect & Greenhouse Gases.” Windows to the Universe.  June 1, 2007.

3.     Young, Jeremy.  “Emiliania huxleyi.” Natural History Museum. Date Accessed: November 15, 2012.  http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/climate-change/emiliania-huxleyi/index.html

4.     DOE Joint Genome Institute U.S. Department of Energy.  “Emiliania huxleyi CCMP1516 main genome assembly.”  Date Accessed: November 15, 2012.  http://genome.jgi-psf.org/Emihu1/Emihu1.home.html

5.     Tyrrell, T. and Merico, A. (2004) Emiliania huxleyi: bloom observations and the conditions that induce them. In,Thierstein, H.R. and Young, J.R. (eds.) Coccolithophores: from molecular processes to global impact. Berlin, Germany, Springer, 75-97.

6.     Charlson RJ, Lovelock JE, Andreae MO, & Warren SG.  1987.  “Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate.”  Nature. 326:655-661.

7.     Van Rijssel, Marion & Gieskes, Winfried W.C.  2002.  “Temperature, light, and the dimethylsulfoniopropionate (DMSP) content of Emiliania huxleyi (Prymnesiophyceae).” J of Sea Res.  48:17-27.

Naegleria fowleri: Thanksgiving in Your Brain

Picture this scenario.  It is a hot summer day and you are hanging out with your friends at the local Walmart causing nothing but trouble trying on clothes you are not going to buy, cruising around on the handicap carts, and playing freeze tag.  Being such a sweltering day you decide to give the Walmart employees a break by heading over to the lake to cool off and take a dip.  Arriving at the beach you shut the car off, swing open the door, and race to the water.  Showing off for your friends you take a giant leap at the edge of the water, go airborne, super-man, and then finish by gracefully diving into the water.  Unfortunately for you, you were not graceful enough and receive a nice sinus flushing.  Other than a minor lingering headache that hangs around the rest of the day, you are fine, for now.  Normally they say what you do not know does not hurt you, but in this case it will kill you.  Funny how a day full of fun and pranks can turn in to one of unbearable pain, vomiting, and death, all thanks to the water-borne amoeba Naegleria fowleri.

N. fowleri life stages

            Unbeknownst to you, the water that flushed your sinuses contained the free-living amoeba N. fowleri.  To make matters worse, it has begun burrowing its way through your skull towards your brain, where it will feast.  N. fowleri was first cultured and documented by the medical scientists M. Fowler and R. F. Carter in Southern Australia 1965 (1).  They, as is common practice today, extracted the amoeba from the dead body of a N. fowleri victim.  The problem with this practice is the patient is all ready dead, so they cannot be helped.  Interestingly N. fowleri exists in three diverse morphological states: the classic amoebic trophozoite, the flagellate, and the cyst.  Trophozoites are the actively breeding, feeding, and infecting morphology of N. fowleri.  In this form it is motile via active sinusoidal/limacine (oscillating) locomotion and reproduces strictly by binary fission (2).  Trophozoites transform into the flagellate form when ionic concentrations are changed, but this has only been observed under laboratory conditions.  Common in nature however is the highly resilient cyst form of N. fowleri, which Trophozoites transform to under nutrient starvation or harsh conditions (1).  Understanding the variant morphological forms and how they lead to a N. fowleri infection may help shed light on possible treatments.

Food-cup shown by red arrow (1).    

            Upon arriving in your nose, and if conditions are right, the amoeba will find itself at the olfactory neuroepithelium, the thin tissue loaded with nerve endings that connects your nasal passageway to your brain.  At this point it is believed that your own cells phagocytose, or engulf, N. fowleri cells, bringing them inside your own cells possibly to generate an immune response (2).  Depending upon the virulence of the N. fowleri strain inoculated in your nose, the amoeba will begin burrowing its way towards your brain, evading an immune response.  It literally follows the nerves directly to the brain, eating tissue as it goes.  In culture N. fowleri has indistinguishable surface structures called “food-cups” that are believed to act as a mouth for the organism, nibbling away at tissue and engulfing it piece by piece in a process called trogocytosis (3).  Within a few days of burrowing N. fowleri will reach your brain, upon which it will kill you.  Reaching the brain is like thanksgiving for the amoeba, as it literally goes on a feeding frenzy gorging on your neural flesh.  N. fowleri also begins reproducing at this point, increasing the number of trophozoites in your skull, amplifying the effects of the infection.

            Upon reaching the cranial cavity and reproducing the infection is now considered primary amebic meningoencephalitis (PAM).  PAM is described as a rapidly fatal disease of the central nervous system (1).  The problem with a N. fowleri infection, PAM, and for you is that detecting the infection early enough is difficult as the symptoms associated with PAM are extremely vague.  With PAM you may experience an intense headache, fever, nausea, vomiting, stiff neck, and potentially a few seizures, all of which would not lead you to the idea that a microbe is slowly burrowing into your brain killing you.  Adding to the confusing symptoms is the fact that you are a healthy, immune-competent young adult; this distinguishes N. fowleri from other free-living amoeba in that it is not an opportunistic infector, but a direct pathogen (2).  In the end you will die a brutally painful death as your brain hemorrhages and you slowly bleed to death

            Depending upon the virulence of the N. fowleri strain eating its way into your brain, your body may or may not develop an effective immune response on its own.  Your first defense is going to be the complement system.  If you are lucky complement will bind to N. fowleri cells, opsonize it (cover the cell surface), and potentially destroy it.  If you are not lucky N. fowleri will simply absorb the complement proteins, negating its immunological effect, or it will express regulatory surface markers that avoid the attention of complement all together.  Next in line are your phagocytic leukocytes, macrophages and neutrophils.  Depending upon the virulence of the amoeba your leukocytes will either destroy the N. fowleri, or be destroyed.  Your body does generate plenty of antibodies against N. fowleri, but without competent cells to react to the antibodies effects they are useless (1).  If your body fails to eliminate the N. fowleri infection on its own you are out of luck.  Currently there are no clinically used drugs that affectively treat a N. fowleri infection.  Doctors have tried using various combinations of Amphotericin B and fluconazole, potent anti-fungal drugs that both target the membrane bound molecule ergosterol, along with rifampin, a drug that prohibits DNA transcription.  The combination has shown promise in the laboratory, but has seen little effect in patients (1).

            While N. fowleri is found in just about every warm body of water possible, the frequency of infection is relatively low with about one case per year (2).  The only way to avoid a possible infection is to stay out of contaminated water all together.  While that is not entirely feasible for some people, I would say you can play the odds, enjoy the water and pray that you are not the one person a year who is brutally killed by the brain eating amoeba, Naegleria fowleri.

Submitted by KH

References:

1.              Cabral, Guy A. "The Immune Response to Naegleria fowleri Amebae and Pathogenesis of Infection." FEMS Immunology & Medical Microbiology. 51.2 (2007): 243-259.

2.              Visvesvara, Govinda S. "Pathogenic and Opportunistic Free-living Amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea." FEMS Immunology & Medical Microbiology. 50.1 (2007): 1-26.

3.              Marciano-Cabral F.  “Cytopathology of pathogenic and nonpathogenic Naegleria species for cultured rat neuroblastoma cells.”  Applied Environmental Microbiology.  51. (1986): 1133-1137.