Journal Highlights

New Extremophile Produces Viscous Polysaccharide

Microorganisms from deep-sea hydrothermal vents produce a variety of industrially intriguingcompounds such as thermostable enzymes, biologically active molecules, hydrocarbon-degradingbacteria, and novel polysaccharides. Gerard Raguenes, Jean Guezennec, and others of IFREMER, theCentre National de la Recherche Scientifique, and Universite Paris 6, have characterized a new aerobicheterotrophic bacterium from an active hydrothermal vent. A subspecies of Alteromonas macleodiidubbed fijiensis, the bacterium produces a novel heteropolysaccharide with a viscosity similar to that ofxanthan, a bacterial metabolite commonly used as a thickener in foods and in various industrial products.

The new compound could find applications in the food industry as well as in wastewater treatments. Chemical and rheological studies are in progress to evaluate possible applications.

(G. Raguenes, P. Pignet, G. Gauthier, A. Peres, R. Christen, H. Rougeaux, G. Barbier, and J.Guezennec. 1996. Description of a new polymer-secreting bacterium from a deep-seahydrothermal vent, Alteromonas macleodii subsp. fijiensis, and preliminary characterization of thepolymer. Appl. Environ. Mirobiol. 62:6773.)

First Allelic Exchange in M. tuberculosis

Genetic studies of Mycobacterium tuberculosis as well as development of vaccines have beenhampered by the inability to introduce specific chromosomal mutations. In recombination experimentswith Escherichia coli, short substrates have failed to yield allelic exchange in Mycobacterium bovis BCGand M.tuberculosis.

V. Balabramanian, William R. Jacobs, Jr., and colleages at the Albert Einstein College of Medicinereport development of a reliable method for performing allelic exchanges, using a cosmid vector. "Although BCG is one of the most widely used vaccines, its variable efficacy necessitates thedevelopment of newly attenuated M. tuberculosis-based vaccines," the authors write. "Making preciselydefined nonrevertible mutations in the M. tuberculosis genome is an essential step in the development ofsuch vaccines." Additionally, "the leucine auxotrophic mutant appears to be a powerful tool forgenetically dissecting the virulence mechanisms of M. tuberculosis," says Jacobs.

(V. Balabramanian, M. S. Pavelka, Jr., S. S. Bardarov, J. Martin, T. R. Weiabrod, R. A. McAdamB. R. Bloom, and W. R. Jacobs, Jr. 1996. Allelic exchange in Mycobacterium tuberculosis with longlinear recombination substrates. J. Bacteriol. 178:273-279.)

Mutation in SerA Homolog May Cause Neurometabolic Syndrome

2-Hydroxyglutaric aciduria is a genetically caused neurometabolic disease. While investigatingmetabolic relationships between pyridoxal 5'-phosphate and serine biosynthesis in Escherichia coli, GenshiZhao and Malcolm E. Winkler discovered that the SerA enzyme catalyzes a previously undetected reductionof alpha-ketoglutarate to 2-hydroxyglutaric acid (2-HGA).

The authors suggest that mutations in the human homolog of the E. coli SerA enzyme may contribute tothe human genetic disease. "This is the first time the route of 2-HGA biosythesis has been figured out in anyorganism, and that is going to be a starting point to look at the metabolism of this compound in bacteria andhumans," Winkler says.

Winkler expects to collaborate on further studies with colleagues at Baylor College of Medicine. "Theyhave had patients with this syndrome and already have cell lines. We plan to pull out the gene encoding theSerA homolog from the human cell lines and see if it has mutated."

(G. Zhao and M. E. Winkler. 1996. A novel alpha-ketogluta-rate reductase activity of the serA-encoded 3-phospho-glycerate dehydrogenase of Escherichia coli K-12 and its possible implications forhuman 2-hydroxyglutaric aciduria. J. Bacteriol. 178:232-239.)

Immobilized Yeasts Produce Finer Wine

Glycerol is a very important constituent of wine, contributing to sweetness and possibly to body andfullness. It is the major end product of yeast fermentation after ethanol and carbon dioxide.

Maurizio Ciani and Luisa Ferraro of the Universita di Perugia tested use of Candida stellate as a fermen- tation starter to increase glycerol content in wines. By immobilizing C. stellate cells, they were able to raiseboth glycerol production and the fermentation rate while minimizing unwanted glycolytic end products.

The novel, sequential fermentation approach, using immobilized Candida cells plus freeSaccharomyces cells, indicates that immobilization can be combined with traditional unit processes to yielda more desirable wine.

(M. Ciani and L. Ferraro. 1996. Enhanced glycerol content in wines made with immobilized Candidastellata cells. Appl. Environ. Microbiol. 62:128-132.)

T-Lymphocyte Developmental Switch Revealed

RANTES (regulated upon activation, normal T cell expressed and secreted) is a C-C chemokinewhich is an important regulator of inflammation. "Inhibitors of RANTES expression may be useful asanti-inflammatory agents, while inducers may be useful in AIDS or cancer therapy," says Alan M.Krensky, of the Division of Immunology and Transplantation Biology, Stanford University School ofMedicine. B. D. Ortiz, A.M. Krensky, and P. J. Nelson have described two cis-acting elements of thehuman RANTES promoter contributing to full activity in T lymphocytes, as well as an early and a late-acting transcriptional regulatory pathway. "The data suggest that T lymphocytes undergo adevelopmental switch after activation," says Krensky.

"We plan to characterize the novel transcription factors binding to these regulatory regions and applythese findings to the development of novel immunotherapies involving induction or inhibition of RANTESexpression," says Krensky.

(B. D. Ortiz, A. M. Krensky, and P. J. Nelson. 1996. Kinetics of transcription factors regulating theRANTES chemokine gene reveal a developmental switch in nuclear events during T-lymphocytematuration. Mol. Cell. Biol. 16:202-210.)

Drosophila Homolog for Human Transcription Factor

Transcription factors play a very important role in determining pattern and morphogenesis. Peter Toliasand others from the Public Health Research Institute have cloned and characterized the Drosophila homologof human NF-Xl, dubbed Shuttle Craft (STC). NF-X1 is a cytokine-inducible transcription factor whichregulates expression of class II major histocompatibility complex genes.

"We have defined a new family of putative transcription factors characterized by sevencopies of a novel cysteine-rich DNA-binding motif," says Tolias. The authors further established that STCmutant embryos are unable to coordinate peristaltic contraction waves required for hatching and so die.

"This behavioral defect is accompanied by subtle morphological abnormalities in the central nervoussystem," says Tolias. "Our future objective is to study the role that STC protein plays in axon guidance andnerve cord development by identifying additional genes that it interacts with and regulates."

(N. D. Stroumbakis, Z. Li, and P. P. Tolias. 1996. A homolog of human transcriptionfactor NF-X1 encoded by Drosophila shuttle craft gene is required in the embryoniccentral nervous system. Mol. Cell. Biol. 16:192-201.)

Precision Integration for Gene Therapy

Retroviruses are now widely used as vectors for gene delivery. However, their usefulness is limited byinability to target integration of foreign DNA to a specific site.

Now Helene Goulaouic and Samson A. Chow of UCLA School of Medicine have succeeded in biasingthe integration events to within 30 bp of DNA bound by a site-specific binding protein, by fusing the bindingprotein to the C terminus of human immunodeficiency virus type 1 integrase.

Future plans include increasing the specificity of integration with new fusion proteins and in vivo testing. "We hope that our work can lead to development of a vector for genetic -engineering in higher eukaryotesand for gene therapy, in which the delivery of foreign genes to a specific site is desirable or crucial," says Chow.

(H. Goulaouic and S. A. Chow. 1996. Directed integration of viral DNA mediated by fusion proteinsconsisting of human immunodeficiency virus type I integrase and Escherichia coli LexA protein. J.Virol. 70:37-46.)

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