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Tips from the Journals of the American Society for Microbiology: June 2002

American Society for Microbiology

Gene protects baker's yeast from freezing

Researchers from Spain have identified a gene that helps baker's yeast survive freezing temperatures. They report their results in the June 2002 issue of the journal Applied and Environmental Microbiology.

In the study, the scientists identified a number of genes in the yeast Saccharomyces cerevisiae, commonly known as baker's yeast, which appeared to be turned on when the yeast was exposed to sub-freezing temperatures. Further investigation revealed that one of the genes, ERG10, helped protect the yeast from freezing.

Commercial bread dough is often stored frozen, which can kill yeast cells and severely reduce the dough's ability to rise after thawing. "Consequently, the improvement of the freeze tolerance in baker's yeast is of significant commercial importance," say the researchers, adding that their findings could "open up the possibility of design strategies to improve the freeze tolerance of baker's yeast."

S. Rodriguez-Vargas, F. Estruch and F. Randez Gil. 2002. Gene expression analysis of cold and freeze stress in baker's yeast. Applied and Environmental Microbiology, 68: 3024-3030.)

Measuring contamination in meat using infrared light

A real-time method that rapidly tests meat for spoilage uses a spectroscope to measure compounds produced by microorganisms on the meat. Researchers from the University of Wales present this new methodology in the June 2002 issue of the journal Applied and Environmental Microbiology.

The process, called fourier transform infrared spectroscopy (FT-IR), uses infrared light waves to identify specific organic compounds within the meat. The technique measures the absorption of various wavelengths of infrared light by the meat. The pattern of absorption creates a unique fingerprint for each compound.

In the study the researchers tested the ability of FT-IR to detect the biochemical byproducts of microbial contamination in chicken breasts left at room temperature to spoil. Every hour, FT-IR measurements were taken directly from the meat surface and microbial counts were taken by standard culture methods. Estimates made from FT-IR in less than 60 seconds were similar to the final counts made by culturing.

"Using FT-IR, we were able to acquire a metabolic snapshot and quantify, non-invasively, the microbial loads of food samples accurately and rapidly (within 60 seconds) directly from the sample surface," say the researchers.

(D.I. Ellis, D. Broadhurst, D.B. Kell, J.J. Rowland and R. Goodacre. 2002. Rapid and quantitative detection of the microbial spoilage of meat by fourier transform infrared spectroscopy and machine learning. Applied and Environmental Microbiology, 68: 2822-2828.)

Oral vaccine boosts existing tuberculosis vaccine

An experimental oral vaccine appears to boost the existing tuberculosis vaccine in mice, say researchers from Statens Serum Institute in Copenhagen, Denmark. Their findings appear in the June 2002 issue of the journal Infection and Immunity.

The current BCG vaccine for tuberculosis remains a mainstay of control programs world wide, but while it continues to be effective protecting children from systemic tuberculosis, it no longer appears to be effective in protecting many adults from the pulmonary version of the disease. The researchers have developed an oral vaccine that by itself does not elicit immunity but does boost immunity to protective levels in adult mice that had already been given the BCG vaccine.

"Despite decades of effort and enormous expenditure, tuberculosis remains of the world's most devastating diseases," say the researchers. "The approach outlined in this report offers the possibility of a simply administered oral booster vaccine specifically targeted to the prevention of adult pulmonary tuberculosis."

(T.M. Doherty, A. Weinrich Olsen, L. van Pinxteren and P. Anderson. 2002. Oral vaccination with subunit vaccines protects animals against aerosol infection with Mycobacterium tuberculosis. Infection and Immunity, 70: 3111-3121.)

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Full copies of all above articles can be accessed through the ASM website at http://www.asmusa.org/pcsrc/tip.htm.

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