Tips from the Journals of the American Society for Microbiology

December 19, 2002


Researchers from Greece and Belgium have isolated bacteria in Greek cheese that produces an antimicrobial peptide which could be used as a natural preservative in some foods and fresh cheeses. Their results appear in the December 2002 issue of Applied and Environmental Microbiology.

Lantibiotics are antimicrobial compounds produced by bacteria which are of increasing interest to scientists because they can kill a variety of bacteria responsible for food-borne disease and spoilage without causing harm to humans. Scientists have identified the bacterium, Streptococcus macedonicus, in Greek Kasseri cheese which produces the food-grade lantibiotic, macedocin, when grown in milk. Macedocin appears to be active against a broad spectrum of bacteria.

"The need for expanded and legal use of bacteriocins in foods is obvious, especially in light of consumers' demands for safe and minimally processed foods that have adequate shelf life and are convenient and the global need for increasing the supply of healthy and safe foods," say the researchers. "Thus, the use of S. macedonicus as a protective starter culture in food fermentations seems to be a straightforward option."

(M. D. Georgalaki, E. Van den Berghe, D. Kritikos, B. Devreese, J. Van Beeumen, G. Kalantzopoulos, L. De Vuyst, E. Tsakalidou. 2002. Macedocin, a food-grade lantibiotic produced by Streptococcus macedonicus ACA-DC 198. Applied and Environmental Microbiology, 68.12: 5891-5903.)


Certain species of lactobacilli may protect women from gonorrhea, say researchers from the Uniformed Services University in Bethesda, Maryland. They report their findings in the December 2002 issue of the journal Infection and Immunity.

In the study, the researchers tested the ability of four species of lactobacilli commonly found in the vagina to inhibit the reproduction of Neisseria gonorrhoeae, the bacterium that causes gonnorhea, under different pH conditions. While all four inhibited growth in acidic conditions, only two were able to inhibit growth under neutral pH. The researchers believe that the lactobacilli were able to inhibit growth by producing hydrogen peroxide.

"On the basis of these data, one might hypothesize that the capacity of commensal lactobacilli to protect women against gonorrhea may depend on both the species and stage of menstrual cycle," say the researchers.

(D.C. St. Amant, I.E. Valentin-Bon and A.E. Jerse. 2002. Inhibition of Neisseria gonorrhoeae by Lactobacillus species that are commonly associated with the female genital tract. Infection and Immunity, 70:7169-7171.)


Symbiotic bacteria in the digestive tracts of microscopic worms produce a compound that is an effective ant repellent, say researchers from the University of California, Davis, and the University of Wisconsin, Madison. They report their findings in the December 2002 issue of the journal Applied and Environmental Microbiology.

Microscopic worms, known as nematodes, reproduce inside and kill some insects and are increasingly being used as natural alternatives to chemical pesticides in agricultural production. The researchers have discovered that the same bacteria that the nematodes use to kill their insect hosts also produce a compound called ant-deterrent factor (ADF) that discourages scavengers, such as ants, from consuming the dead insects before the nematodes inside mature.

"Scavengers, such as ants, can adversely affect the persistence of entomopathogenic nematodes being used as biological control agents," say the researchers. "Future research is needed to elucidate the nature of ADF, isolate the gene(s) required for the expression of ADF and determine the range of its activity against insects and other arthropods or vertebrates. The results of such studies may lead to an enhancement of ADF activity and ADF-fortified nematode application as a viable approach to agricultural and structural pest management."

(X. Zhou, H.K. Kaya, K. Heungens and H. Goodrich-Blair. 2002. Response of ants to a deterrent factor(s) produced by symbiotic bacteria of entomopathogenic nematodes. Applied and Environmental Microbiology, 68: 6202-6209.)

American Society for Microbiology

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