News Release

Tips from the Journals of the American Society for Microbiology

Peer-Reviewed Publication

American Society for Microbiology

ORAL TRANSMISSION OF HIV IS POSSIBLE

When exposed to high levels of human immunodeficiency virus (HIV), the cells lining the mouth can develop a low-level infection, a finding that increases our understanding of the risks of oral transmission of the disease. Researchers from Charles R. Drew University and the University of California, Los Angeles, report their findings in the March 2003 issue of the Journal of Virology.

"The majority of HIV type 1 infections occur via mucosal contact, and there are several reports indicating that the oral mucosa may be one route of exposure," say the researchers. "It is difficult to confirm that oral mucosa is a major transmission portal because of the correlation between oral-genital contact and other transmission risk behaviors."

In the study, the researchers tested the ability of HIV to infect oral mucosal cells known as normal human oral keratinocytes (NHOK). They found that when exposed to high concentrations of the virus, the cells established a low-level, productive infection that could subsequently transfer to other cells in the body.

"Human saliva contains several types of anti-HIV activity that may help protect an individual against a small virus inoculum. However, if individuals are exposed to inocula containing a heavy viral load, it is conceivable that the oral epithelium could be infected and thus serve as a beachhead for HIV-1 infection," say the researchers.

(X. Liu, J. Zha, H. Chen, J. Nisitani, P. Camargo, S.W. Cole and J.A. Zack. 2003. Human immunodefiency virus type 1 infection and replication in normal human oral keratinocytes. Journal of Virology, 77: 3470-3476.)

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BACTERIA PRODUCE ELECTRICITY

Scientists from the University of Massachusetts have developed a strategy for a fuel cell that uses bacteria to convert organic matter into electricity. They report their findings in the March 2003 issue of the journal Applied and Environmental Microbiology.

While the concept of a microbial-based fuel cell is not entirely new, previous studies have noted several problems in their development. One important problem was that in order to produce electrical current, the bacteria required the addition of toxic chemicals as mediators.

In this study, the researchers tested the ability of a recently identified bacterium, called Geobacter sulfurreducens, to produce an electrical current. When grown in a microbial fuel cell using graphite rods, the bacteria were able to produce a stable, low-level electrical current without the need for a toxic mediator.

"These studies demonstrate that G. sulfurreducens grows on the surface of energy-harvesting anodes in mediator-free microbial fuel cells, forming a stable, attached population that can continually produce electrical current via the oxidation of organic matter," say the researchers. "These findings greatly expand the potential for using microorganisms to convert organic matter to electricity."

(D.R. Bond and D.R. Lovley. 2003. Electricty production by Geobacter sulfurreducens attached to electrodes. Applied and Environmental Microbiology, 69: 1548-1555.)

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Bacteria May Protect Unpasteurized Cheese from Foodborne Disease

German researchers found that a bacterium may be a simple answer to preventing Listeria in cheese. Their findings appear in March 2003 issue of the journal Applied and Environmental Microbiology.

In the study, cheese was ripened with or without the bacterium Lactobacillus plantarum. The results showed complete inhibition to listeria bacteria in the cheese produced with L. plantarum. The reason for the inhibition appears to be a compound produced by L. plantarum called pediocin. The authors did express a mild concern over an observation that in some cases listeria may become resistant.

"The addition of a L. planatarum culture is a potent measure for combating listeria in a contaminated production line, but because of the potential development of resistance, it should not be used continuously over a long time in a production line," say the researchers.

(M. Loessner, S. Guenther, S. Steffan, S. Scherer. 2003. A pediocin-producing Lactobacillus plantarum strain inhibits Listeria monocytogenes in a multispecies cheese surface microbial ripening consortium. Applied and Environmental Microbiology, 69. 3: 1854-1857.)

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