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Journal Highlights

Do Food Starter Cultures Ferment Trouble? 

Use of lactic acid bacteria in food processing dates to the Neolithic era. Currently, probiotic strains are gaining popularity in functional foods. But now, Enterococcus is emerging as a leading opportunistic nosocomial pathogen, often in multidrug-resistant form, brewing controversy over that microbe's use in food (see p. 293). 

Tracy J. Eaton and Michael J. Gasson of the Institute of Food Research, Norwich, United Kingdom, show that medical isolates of Enterococcus had more virulence determinants than did food isolates, which had more than starter strains. They demonstrated that starter strains can acquire virulence determinants from medical strains, and identified multiple pheromone-encoding genes, which facilitate plasmid-mediated gene transfer, in both food and starter strains. The results suggest that the use of Enterococcus in food should be carefully evaluated, says Eaton. This team is conducting studies of starter strains that have acquired virulence determinants by conjugation from medical strains. 

(T. J. Eaton and M. J. Gasson. 2001. Molecular screening of Enterococcus virulence determinants and potential for genetic exchange in food and medical isolates. Appl. Environ. Microbiol. 67:1628-1635.) Abstract | Full Text

Single Amino Acid Substitution Enables Foot and Mouth Virus To Infect Guinea Pigs 

Sobrino

RNA viruses adapt relatively easily to new hosts, raising the specter of emergent diseases. Francisco Sobrino and colleagues of the Universidad Autónoma de Madrid show that a single amino acid replacement resulted in adaptation of the RNA virus responsible for foot-and-mouth disease (FMDV) to the guinea pig. “Our work highlights the huge potential for variation and adaptation to new hosts of an important animal virus,” says Sobrino. Additionally, “Our results illustrate that nonstructural proteins, not directly involved in the cell receptor-virus interactions, can modulate the virus host range.” Sobrino plans to try to characterize the functional role of these nonstructural proteins. 

(J. I. Núńez, E. Baranowski, N. Molina, C. M. Ruiz-Jarabo, C. Sánchez, E. Domingo, and F. Sobrino. 2001. A single amino acid substitution in nonstructural protein 3A can mediate adaptation of foot-and-mouth disease virus to the guinea pig. J. Virol. 75:3977-3983.)  Abstract | Full Text

Teichoic Acid Net Charge Influences Staph Ability To Colonize Implants 

Peschel

Staphylococcus aureus is responsible for a large percentage of infections associated with implanted biomedical devices. The molecular basis of primary adhesion to artificial surfaces is not understood, and efforts to prevent colonization by modifying plastic surfaces have had little success. Andreas Peschel and colleagues of the University of Tübingen now show that teichoic acids, highly charged cell wall polymers, play a key role in the first step of biofilm formation. Teichoic acid mutants bearing a stronger negative surface charge due to lack of D-alanine esters failed to colonize polystyrene and glass, says Peschel. “We conclude that increasing the repulsive electrostatic forces between implanted device and bacterial surface should reduce the risk of implant-associated infections.”

“We are now studying further features of the staphylococcal cell envelope to obtain a better understanding of interactions with innate or implanted host components,” says Peschel. 

(M. Gross, S. E. Cramton, F. Götz, and A. Peschel. 2001. Key role of teichoic acid net charge in Staphylococcus aureus colonization of artificial surfaces. Infect. Immun. 69:3423-3426.) Abstract | Full Text

Phage-Mediated Transduction More Common than Was Thought 

Sander and Schmieger

Horizontal gene transfer is important both evolutionarily and in risk assessments of release of genetically modified organisms. In bacterial systems, phage-mediated general transduction has widely been neglected, because few transducing phage/host systems are known. Horst Schmieger and Michaela Sander of Ludwig-Maximilians-Universität München, Munich, Germany, have developed a method for host-independent detection of transducing phage that works in any natural habitat, that succeeds even when host bacteria cannot be cultured, and that can be applied even to eukaryotic hosts. It is based on PCR amplification of phage-encapsulated 16S rDNA, and shows that phage mediated transduction is “much more common than we expected,” says Schmieger. 

(M. Sander and H. Schmieger, 2001. Method for host-independent detection of generalized transducing bacteriophages in natural habitats. Appl. Environ. Microbiol. 67:1490-1493.) Abstract | Full Text

Zinc Finger Protein ZFR Required for Perigastrulation Growth and Survival 

Meagher

Transition from pre- to postimplantation development leads to initiation of complex cellular differentiation, a dramatic decrease in cell cycle length, and a commensurate increase in an embryo's size. These changes require sophisticated control mechanisms. Madeleine J. Meagher and Robert E. Braun of the University of Washington had shown that mutation of the mouse gene encoding the zinc finger protein, ZFR, fatally disrupted postimplantation and gastrulation-stage development. The homozygous mutant embryos “form mesoderm but they are delayed in their development and fail to form normal anterior embryonic structures,” the researchers now report. “Loss of ZFR function leads to both an increase in programmed cell death and a decrease in mitotic index...” Many genes with similar gastrulation stage defects, such as Brca1 and -2, and huntingtin, “play critical roles at later developmental stages,” says Meagher. “Future experiments may include generation of homozygous Zfr null embryonic stem cells and embryo chimeras to dissect the role of Zfr in different germ cell layers, and creation of a conditional mutation for studying the gene in spermatogenesis.”

(M. J. Meagher and R. E. Braun. 2001. Requirement for the murine zinc finger protein ZFR in perigastrulation growth and survival. Mol. Cell. Biol. 21:2880-2890.) Abstract | Full Text

Cationic Antimicrobial Peptides Show Synergy 

Cationic antimicrobial peptides are gaining recognition as components of the immune systems of all species. By taking measurements of fractional inhibitory concentrations, Robert E. W. Hancock and Hong Yan of the University of British Columbia demonstrate for the first time that cationic antimicrobial peptides from mammals are synergistic with one another and with human lysozyme. “Since these agents are being developed as a novel class of antibiotics, this synergy should be exploited,” says Hancock. 

“We have also recently observed that these peptides have an ability to activate transcriptional responses in macrophages that are consistent with an important role in stimulating antimicrobial innate immunity that is separate from their ability to kill bacteria,” says Hancock. “We are very interested to know if the synergy observed in killing also occurs for these non-antimicrobial functions.”

(H. Yan and R. E. W. Hancock. 2001. Synergistic interactions between mammalian antimicrobial defense peptides. Antimicrob. Agents Chemother. 45:1558-1560.) Abstract | Full Text