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Posts by Anne
A Malaria Vaccine
The disease malaria is caused by a protozoan parasite with several different life cycle stages that occur inside mosquitoes and inside an infected person. Most parasites with complex life cycles have been difficult to prevent by inventing a vaccine against infection. Scientists have been trying to perfect a malaria vaccine for more than two decades with little success.
In late 2011, Ghana’s Kwame Nkrumah University finished studies on a new malaria vaccine that, although not perfect, reduces the risk of malaria by about 50 percent. The final phase of clinical testing of the vaccine was conducted in 6,000 children of sub-Saharan Africa, where malaria has always taken a high toll. The disease kills more than a million people each year, mostly children under age 5 in sub-Saharan Africa.
The Ongoing Listeria Outbreak
A food-borne outbreak associated with Listeria-contaminated cantaloupes continues to take lives. The outbreak began in mid-summer of 2011 when contaminated melons from a farm in upstate New York and another in Colorado were implicated by the U.S. Food and Drug Administration as the source of the pathogen Listeria monocytogenes. In a few months, more than 100 people were sickened from eating the melons and about two dozen people died.
Cantaloupes have been implicated in other food-borne outbreaks in the past. No one is sure why the melon is a higher risk for carrying food-borne pathogens than other fruits. Most fruits can carry germs on their skin because they pick up contamination from fertilizers or from animals that move through the growing fields before harvesting. Contamination can enter the edible portion of the fruit when it is sliced. But cantaloupes are rather porous compared with fruits such as apples. The pathogens might be able to penetrate the melon’s outer skin even without slicing open the fruit.
Listeria monocytogenes is one of the more prevalent food-borne pathogens worldwide. It is found almost everywhere in soil and yet little information has been gathered on how it survives in nature. The organism is known to inhabit the digestive tract of humans and many other animal species. Microbiologists also know this pathogen tolerates cold temperatures that slow down the growth of most other bacteria. This attribute of Listeria allows it to proliferate in refrigerated foods and explains why outbreaks occur from eating cheeses, deli meats, and fruit salads, even when these foods were properly refrigerated.
The disease listeriosis has symptoms similar to almost every other type of food-borne illness: nausea, vomiting, and diarrhea. But L. monocytogeneses also attacks the nervous system in serious infections. Like most pathogens, it presents a greater danger to people in the so-called “high-risk” health groups: pregnant women, the elderly, young children, people with chronic disease, and the immunocompromised.
Bacteria and Colon Cancer Linked?
In 2011, two research teams working independently concluded that certain bacteria of the large intestine can be linked to higher rates of colon cancer. Microbiologists have long known that bacteria of the genus Fusobacterium inhabit the human mouth and the human intestines and that of other animals. In the intestines, these bacteria ferment sugars and produce mainly butyric acid. Until now, that activity was the organism’s only claim to fame.
The recent studies indicate that Fusobacterium infiltrate intestinal tissue in patients with colon cancer. This finding led researchers to propose that Fusobacterium may be linked in some way to the events leading to cancer. But microbiologists do not know if Fusobacterium is part of the cancer’s cause or whether the bacteria simply find cancerous tissue easier to infect then healthy tissue.
Often the presence of a microbial species in the body gives a good indication of a disease. But Fusobacterium normally lives in the body and is part of a person’s normal flora. It is much more difficult to figure out if normal flora are causing disease or are taking advantage of conditions in the body due to a disease that has been caused by something else. For the moment, there is no reason to fear the bacteria living inside your intestines and vital to good health and nutrition.
Microbiofuels on the Way?
Hydrogen is one of nature’s simplest molecules. Made of two hydrogen atoms (H2), this gas consists of only two protons and two electrons. Scientists have developed car prototypes that run on H2 rather than gasoline and hope this will offer yet another promising avenue in the search for vehicles using alternatives to fossil fuels. Even better news comes from the world of microbes where several major groups of organisms produce H2 as a normal end product of their metabolism. Could these microbes become a major future source of a new biofuel, a microbiofuel?
Among the microbes that emit H2 are bacteria that ferment sugars in anaerobic (no oxygen) environments, cyanobacteria, specialized photosynthetic bacteria called purple nonsulfur bacteria, and many algae. Cyanobacteria and green algae have been studied as the most promising H2-producers because of their ability to make H2 from water.
Microbiologists caution that microbiofuel-powered vehicles powered still have significant hurdles to overcome. The H2-producing reaction must be harnessed inside specially designed bioreactors. In addition, scientists must learn how to manipulate the microbe’s growth to favor H2 production. The water-to-hydrogen reaction inside microbes also produces an oxygen molecule. Despite the abundance of oxygen around us, this element is very toxic to microbial cells. But the good news about microbial H2 production makes it a goal worth achieving. H2-producers are found almost everywhere in soil and water. They need little to keep them going because, except for fermenting microbes, they are photosynthetic. Simply supply light and water and the microbes do the rest.
Most new technologies that radically change industries start out as too expensive for today’s practical purposes. But without continued research in these technologies, society would never invent anything. The temptation to develop microbes that grow readily in the environment (cheap) and naturally convert sunlight (free) to a fuel that would help break our dependence on fossil fuels seems to be too great to ignore.
If the job of getting hydrogen fuel from algae still lies decades away, biodiesel from algae may be much closer on the horizon. Diesel fuel is like gasoline in that it comes from crude oil, but diesel is made in refineries by a different process and used in specially designed engines that differ from gasoline combustion engines. In seeking alternatives to fossil fuels, scientists have for a long time investigated the possibility of making diesel out of non-crude oil sources. If these sources are of biological origin, like plants or microbes, we call the fuel “biodiesel.”
Algae may offer one of the most economic ways to produce biodiesel. Algae grow readily in ponds exposed to sunlight and air from which they absorb carbon dioxide. When algae grows, the cells store energy in the form of oils. Is the harvesting of algae for making biodiesel a practical answer to our need for alternative fuels? Is “oilgae” in our future?
Small entrepreneur companies as well as behemoth oil companies have experimented with algae biodiesel. One approach involves growing mats of algae on the surface of large ponds exposed to sunlight. The mat can be skimmed off the top of the pond and then either pressed to express the oils or treated with an industrial solvent that dissolves the oil. A refining process is then used for turning the algae extract into a fuel.
How close are we to adding algae oil to our list of fossil fuel alternatives? A process for getting fuel from algae has already been designed. But even this seemingly inexpensive process has special requirements with high costs. For example, an algae fuel producer must have sufficient land to build the algae ponds and pay for a large volume of water to keep the ponds working. Entrepreneurs have experimented with indoor algae tanks, which take up less space but also require special lighting to keep the algal photosynthesis reactions going. A few companies are designing new types of algae that grow by fermenting sugars rather than use photosynthesis. This innovation cuts down space and lighting costs. At least one company has in the past few years experimented with a way to harvest the oil from algae without killing them. This would reduce the need for growing a new batch of algae after each harvest.
Will the naysayers win out over the dreamers in our quest to investigate every possible new fossil fuel alternative? In 2008, about 15 algae biodiesel companies were trying their hand at producing this fuel. Since then, the oil companies BP, Shell, Exxon, Valero, and Chevron added research projects in this area. Shell has already scrapped the idea and finds no promise in oilgae. The route to success will probably avoid massive algae-growing operations that use enormous amounts of land and water. Perhaps oilgae technology that has yet to be uncovered will come from new ways to engineer algae tanks or bioreactors, a more efficient oil harvesting process, and oil refining compatible with a new generation of vehicles.
Viruses to the Rescue
Viruses are particles of only a few nanometers in width and which infect living cells. (A nanometer is one-billionth of a meter.) Because of their tiny size, scientists have long considered viruses to be a perfect fit for nanotechnology, the science of objects measured on a nanometer scale. University of California scientists have developed a technique for getting certain viruses to self-assemble into thin films, long strands, and other structures that might be useful in nanotechnology and in human health.
The Berkeley scientists have induced viruses to make three different types of films of increasing complexity. These films may eventually be developed as substitutes for natural substances in the body. Viral films might become precursors for making artificial collagen, skin, or components of the eye. In the future, substances assembled by viruses may be useful in helping the body repair damaged tissue or control abnormal tissue growth.
The virus being studied in these experiments is called M13. M13 is a bacteriophage, which is a virus that infects only bacterial cells and not any other living thing. Thus, M13 is safe for study and for any future uses in medicine.