Background: There is growing interest in the immune-stimulating effect and in particular, the anti-allergic effect, of lactic acid bacteria (LAB). However, no comprehensive studies have been done that compare the immune-stimulating potential of LAB strains. Methods: The in vitro immune-stimulating effects on Th1/Th2 balance of more than 100 LAB strains were compared in splenocytes from ovalbumin-sensitized Th2-polarized mice. The in vivoanti-allergic ability of strain KW3110 was studied in the Th2-polarized model by detecting serum IgE concentration, Th1/Th2 cytokine secretion from splenocytes, and the expression of co-stimulatory molecules on macrophages. Results: In vitro studies from Th2-polarized splenocytes, using IL-12 as a Th1 parameter and IL-4 secretion as a Th2 parameter revealed a wide variety of IL-12-inducing and IL-4-repressing activities, depending on the strain of LAB, not depending on the species. However, evaluation of individual strains in vivo revealed that after exposure to Lactobacillus paracasei KW3110 strain, the serum IgE elevation elicited by repeated OVA injection of mice was strongly inhibited. Cytokine secretion from splenocytes 20 weeks after KW3110 administration showed increased IL-12 and decreased IL-4 expression. Both CD40 and B7-1 expression on macrophages was upregulated by administration of KW3110. Conclusions: Improving the consequences of the Th1/Th2 imbalance by administration of LAB was dependent upon the LAB strain rather than the LAB species. Oral KW3110 administration in the mouse allergy model directed the Th1/Th2 balance toward Th1 through the maturation of APCs and inhibition of serum IgE elevation.

Studies of field-effect control of the high mobility electrons in MBE-grown selectively doped GaAs/n-Al x Ga1-x As heterojunctions are described. Successful fabrication of a new field-effect transistor, called a high electron mobility transistor (HEMT), with extremely high-speed microwave capabilities is reported.

We have analyzed a locus on the annotated Lactobacillus plantarum WCFS1 genome that showed homology to the staphylococcal agr quorum-sensing system and designated it lam for Lactobacillus agr-like module. Production of the lamBDCA transcript was shown to be growth phase dependent. Analysis of a response regulator-defective mutant (⌬lamA) in an adherence assay showed that lam regulates adherence of L. plantarum to a glass surface. Global transcription analysis of the wild-type and ⌬lamA strains in early, mid-, and late log phase of growth was performed using a clone-based microarray. Remarkably, only a small set of genes showed significant differences in transcription profiles between the wild-type and lamA mutant strains. The microarray analysis confirmed that lamBDCA is autoregulatory and showed that lamA is involved in regulation of expression of genes encoding surface polysaccharides, cell membrane proteins, and sugar utilization proteins. The lamBD genes encoding the putative autoinducing peptide precursor (LamD) and its processing protein (LamB) were overexpressed using the nisin-controlled expression system, and culture supernatants were analyzed by liquid chromatography/mass spectrometry (LC/MS) to identify overproduced LamD-derived peptides. In this way, a cyclic thiolactone pentapeptide that possesses a ring structure similar to those of autoinducing peptides of the staphylococcal agr system was identified. The peptide was designated LamD558, and its sequence (CVGIW) matched the annotated precursor peptide sequence. Time course analysis of wild-type culture supernatants by LC/MS indicated that LamD558 production was increased markedly from mid-log to late log growth phase. This is the first example of an agr-like system in nonpathogenic bacteria that encodes a cyclic thiolactone autoinducing peptide and is involved in regulation of adherence.Regulation of physiological changes in bacterial populations in many cases has been shown to be dependent on specific cell densities and growth phases. This phenomenon of cell densitydependent gene expression has been termed quorum sensing and was initially found to regulate bioluminescence in Vibrio fischeri (15). Since then, a large variety of quorum-sensing systems has been discovered in both gram-negative and grampositive bacteria (29). Well-studied examples of quorum sensing-regulated features in gram-positive bacteria include genetic competence in Bacillus subtilis (55) and Streptococcus pneumoniae (8), virulence and biofilm formation in Staphylococcus aureus (39, 65) and Enterococcus faecalis (16,44), and the production of antimicrobial peptides, including bacteriocins and lantibiotics, in various lactic acid bacteria (26,38). To regulate these quorum-sensing systems, bacteria produce extracellular signaling molecules that are responsible for cell-tocell communication. While many gram-negative bacteria communicate via N-acyl-homoserine lactones, peptides are the most common and well-studied signaling molecules in grampositive bacteria; here these peptides are...

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The ATFi gene, which encodes alcohol acetyltransferase (AATase), was cloned from Saccharomyces cerevisiae and brewery lager yeast (Saccharomyces uvarum). The nucleotide sequence of the ATFI gene isolated from S. cerevisiae was determined. The structural gene consists of a 1,575-bp open reading frame that encodes 525 amino acids with a calculated molecular weight of 61,059. Although the yeast AATase is considered a membrane-bound enzyme, the results of a hydrophobicity analysis suggested that this gene product does not have a membrane-spanning region that is significantly hydrophobic. A Southern analysis of the yeast genomes in which the ATF] gene was used as a probe revealed that S. cerevisiae has one ATF) gene, while brewery lager yeast has one ATF1 gene and another, homologous gene (Lg-ATFI). Transformants carrying multiple copies of the ATF) gene or the Lg-ATFJ gene exhibited high AATase activity in static cultures and produced greater concentrations of acetate esters than the control.

Alcohol acetyltransferase (AATase) catalyzes the esterification of isoamyl alcohol by acetyl coenzyme A. The enzyme was solubilized from the microsomal fraction of Saccharomyces cerevisiae Kyokai No. 7, using Triton X-100 and then purified by a series of chromatographic separations: Poly Buffer Exchanger 94 (PBE94), DEAE Toyopearl, Toyopearl HW60, hydroxyapatite, Octyl-Sepharose CL-4B, and hexanol-affinity column chromatography. When the solubilized enzyme was put on PBE94, two active fractions were obtained. The enzyme obtained after affinity column chromatography had a single band on an SDS polyacrylamide gel, and its molecular mass was estimated to be 60 kDa. The enzyme was most active at pH 8.0 and 25 degrees C. It was stable between pH 7.5 and 8.5, but was unstable at temperatures above 10 degrees C. The activity was markedly inhibited by heavy metal ions such as Cd2+, Cu2+, Zn2+, and Hg2+, and sulfhydryl reagents. The Km for acetyl-CoA was 0.19 mM. The internal peptide sequences were also identified.

A broad-specificity delta 9 desaturase gene was cloned from the cyanobacterium Anacystis nidulans. The enzyme introduces a cis-double bond at the delta 9 position of both 16 and 18 carbon saturated fatty acids linked to many kinds of membrane lipids. The gene was stably introduced into tobacco plants under transcriptional control of the cauliflower mosaic virus 35S promoter, and the enzyme was targeted into plastids by the transit peptide of the pea RuBisCO small subunit. The transgenic plants had a highly reduced level of saturated fatty acid content in most membrane lipids and exhibited a significant increase in chilling resistance.

The reduction of acetate ester synthesis by aeration and the addition of unsaturated fatty acids to the medium has been reported to be the result of the reduction in alcohol acetyltransferase (AATase) activity induced by inhibition of this enzyme. However, regulation of the AATase gene ATF1 has not been reported. In this study, ATF1 gene expression was studied by Northern analysis, and the results showed that the ATF1 gene was repressed both by aeration and by unsaturated fatty acids. The results also showed that the reduction of AATase activity is closely related to the degree of repression of ATF1 mRNA, which suggested that the gene repression is the primary means of reducing AATase activity in vivo. Using the Escherichia coli lacZ gene as a reporter gene, it was shown that a 150-bp fragment of the 5 flanking sequence played a major role in the repression by aeration and unsaturated fatty acid addition.