July 1998

Table of Contents
ASM News Issues

Journal Highlights

Legionella Isolated from Soil Amoeba

Since the discovery of Legionella pneumophila, the number of described species from this genus has risen dramatically. Many of these species can be cultured in vitro in free-living amoebae and other protozoa.

Anthony L. Newsome of Tennessee State University and coworkers have isolated a Legionella species from an amoeba taken directly from the soil. 16S ribosomal DNA analysis indicates that the legionellae are probably members of a new species. The relationship with the amoeba may lead to protection and dissemination of Legionella spp. These results suggest that bacteria pathogenic to protozoa may be similarly dangerous to humans. Newsome plans to determine the frequency of infection of amoebae by legionellae. "We have no idea how often these interactions occur," he says.

(A.L. Newsome, T. M. Scott, R. F. Benson, and B. S. Fields. 1998. Isolation of an amoeba naturally harboring a distinctive Legionella species. Appl. Environ. Microbiol. 64:1688-1693.)

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Metabolic Enzyme on Candida albicans Cell Surface Is Also a Host Ligand Protein

Candida albicans is a serious agent of infection, especially in immunocompromised patients. Previously, M. Luisa Gil of the University of Valencia, Spain, and colleagues discovered that GAPDH protein is on the cell surface of Candida cells in an immunogenic and enzymatically active form. Now they find it can bind to fibronectin and laminin. "The cell wall of C. albicans appears to be much more dynamic and complex than initially thought, and one is left with the impression that this structure is like a Pandora's box," says Gil. She plans to work on its structure, function, and virulence, as well as immune response to GAPDH to determine its potential as an antigen for diagnosis and vaccine.

(D.Gozalbo, I. Gil-Navarro, I. Azorin, J. Renau-Piqueras, J. P. Martinez, and M. L. Gil. 1998. The cell wall-associated glyceraldehyde-3-phosphate dehydrogenase of Candida albicans is also a fibronectin- and laminin-binding protein. Infect. Immun. 66:2052-2059.)

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Culture Media May Greatly Misrepresent Nature

Studies of microbial activities in the laboratory which use defined culture media may greatly misrepresent actual behavior in nature.

Daniel Cullen of the USDA Forest Products Laboratory, Madison, Wis., and colleagues compared RNA transcripts for a cellulose synthesized by a well-characterized fungus, Phanerochaete chrysosporium, in defined media, with those from wood chips. "We found the patterns of gene expression in wood to be dramatically different from the patterns previously observed in defined or semidefined media," says Cullen. "The methodology developed for quantitative analysis of specific cellulose mRNAs in wood can be applied to other gene families, fungal species, or wood species," says Cullen. "We are now studying expression of ligninolytic genes in wood."

(M. A. Vallim, B. J. H. Janse, J. Gaskell, A. A. Pizzirani-Kleiner, and D. Cullen. 1998. Phanerochaete chrysosporium cellobiohydrolase and cellobiose dehydrogenase transcripts in wood. Appl. Environ. Microbiol. 64:1924-1928.)

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Different Origins Likely for Pathogenicity Islands in Helicobacter pylori

Infection with H. pylori is strongly associated with a variety of ills in addition to ulcer. Heterogeneity of clinical outcome is related to differences in virulence. Colonization with cagA-positive H. pylori correlates with increased risk of gastric cancer and other sequelae. cagA is part of a pathogenicity island and is assumed to have been integrated into the H. pylori chromosome relatively recently.

Zhi Jun Pan, a postdoctoral fellow in the laboratory of Arie van der Ende at the University of Amsterdam, had observed that prevalence of cagA-positive H. pylori in Chinese patients with peptic ulcer disease is universally and unusually high. van der Ende and colleagues compared sequences of parts of cagA, and the results suggest different origins for the pathogenicity islands in Dutch and Chinese patients. van der Ende plans to compare the virulence of gene products from the two pathogenicity islands and to search isolates from other geographic locations for different pathogenicity islands.

(A.van der Ende, Z.-J. Pan, A. Bart, R. W. M. van der Hulst, M. Feller, S.-D. Xiao, G. N. J. Tytgat, and J. Dankert. 1998. cagA-Positive Helicobacter pylori populations in China and the Netherlands are distinct. Infect. Immun. 66:1822-1826.)

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Novel DNA Polymerase in Archaea

When the genome of Methanococcus jannaschii was sequenced two years ago, researchers were perplexed that it contained only one recognizable sequence of DNA polymerase.

Yoshizumi Ishino of the Biomolecular Engineering Research Institute, Osaka, Japan, and colleagues have isolated and characterized a homolog of a novel heterodimeric DNA polymerase, which is entirely different from known DNA polymerases, from M. jannaschii. This discovery "further confirms that archaea are truly different from bacteria and eukaryotes," says Ishino. Ishino plans to study the mechanism of DNA replication in the archaea and to use the polymerase in studies of molecular phylogeny.

(Y. lshino, K. Komori, I. K. O. Cann, and Y. Koga. 1998. A novel DNA polymerase family found in archaea. J. Bacteriol. 180:2232-2236.)

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Endoplasmic Reticulum Needed for Peroxisome Assembly

Peroxisomes are required most notably for lipid metabolism and breakdown of hydrogen peroxide. Peroxisome biogenesis disorders are lethal.

Vladimir I. Titorenko and Richard A. Rachubinski of the University of Alberta show that the endoplasmic reticulum (ER) is essential for peroxisome assembly. They propose that peroxisomes are formed from membrane-bound vesicles that bud from the ER and fuse. Some peroxisomal membrane proteins pass through the ER on their way to the peroxisome, becoming glycosylated as they do. "We are currently establishing conditions that permit this vesicular fusion to occur in the test tube and which aim to reconstitute the peroxisome assembly process outside the cell," says Rachubinski. This "will help us better understand the molecular bases and cellular events involved in generation of peroxisome biogenesis disorders."

(V. I. Titorenko and R. A. Rachubinski. 1998. Mutants of the yeast Yarrowia lipolytica defective in protein exit from the endoplasmic reticulum are also defective in peroxisome biogenesis. Mol. Cell. Biol. 18:2789-2803.)