With the emergence of high-throughput screening in the pharmaceutical industry in the early 1990's, organic chemists were faced with a new challenge: how to prepare large collections of molecules (the libraries) to "feed" the high-throughput screen? The unique exploratory power of some reactions (such as the 40 year-old Ugi four-component condensation) was soon recognized to be extremely valuable to produce libraries in a time- and cost-effective manner. Over the last five years, industrial and academic researchers have made these powerful transformations into one of the most efficient and cost-effective tools for combinatorial and parallel synthesis.

Aims: To determine the fate of Bacillus cereus spores or vegetative cells in simulated gastric medium. Methods and Results: The effects of acidity on the survival of B. cereus in a medium simulating human stomach content was followed on spores at pH 1AE0-5AE2, and on vegetative cells at pH 2AE5-5AE7. Gastric media (GM) were prepared by mixing equal volumes of a gastric electrolyte solution with J broth (JB), half-skim milk, pea soup and chicken. At pH 1AE0 and 1AE4, the number of spores slightly decreased in GM-JB and GM-pea soup and remained stable in GM-milk and GM-chicken. A rapid marked decrease (always higher than 2AE0 log CFU ml )1 in 2 h) in vegetative cell counts was observed at pH below 4AE2, 4AE0, 3AE6 and 3AE5 in GM-chicken, GM-JB, GM-milk and GMpea soup, respectively. Between pH 5AE0 and 5AE3, B. cereus growth was observed in GM-JB (1AE2 log CFU ml )1 increase after 4 h) and in GM-pea soup (1AE8 log CFU ml )1 increase after 4 h). Conclusions: Bacillus cereus spores are very much more resistant to gastric acidity than vegetative cells. This resistance strongly depends on the type of food present in the GM. Significance and Impact of the Study: Our results suggest that the probability that viable B. cereus cells enter the small intestine, where they can cause diarrhoea, strongly depends on the form of the ingested cells (spores or vegetative cells), on what food they are ingested with, and on the level of stomach acidity.

A novel enzyme-linked immunosorbent assay (ELISA) and a confirmatory Western blot (WB) to detect human antibodies against Francisella tularensis were evaluated. The ELISA was based on partially purified lipopolysaccharide (LPS), the WB on whole antigen of F. tularensis. Positive WB showed a typical LPS ladder. Sensitivity and specificity of the ELISA, as assessed in 104 positive sera and 1149 'normal' sera from healthy young adults, were 99.0% and 97.1% respectively. Sensitivity of the WB was close to 100%, whereas specificity was 99.6%. Antibodies against the LPS of F. tularensis were detected in four of the 'normal' sera in both ELISA and WB. The assays were further evaluated using sera of individuals from Norway, Sweden and Kosovo suspected to be infected in tularemia outbreaks. Results revealed that the combination of ELISA and WB is suitable for laboratory confirmation of tularemia as well as for large-scale epidemiological studies.

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In Leuconostoc mesenteroides subsp. mesenteroides 19D, citrate is transported by a secondary citrate carrier (CitP). Previous studies of the kinetics and mechanism of CitP performed in membrane vesicles of L. mesenteroides showed that CitP catalyzes divalent citrate Hcit In bacteria, metabolic energy present in the form of ATP and ion gradients of H ϩ and Na ϩ are used to drive various endergonic reactions associated with cellular growth. The two forms of metabolic energy can be interconverted by the action of membrane-bound F 0 F 1 -ATPases that couple the translocation of an H ϩ (or Na ϩ ) to the hydrolysis/synthesis of ATP. In fermentative organisms, ATP is usually formed by substratelevel phosphorylation (glycolysis; arginine deaminase pathway), which is subsequently used to generate an electrochemical gradient of protons across the cytoplasmic membrane (proton motive force [pmf]) (16). Recently, a different mechanism of pmf generation was discovered that is of particular importance in the energetics of certain anaerobes and allows the F 0 F 1 -ATPase to function in the synthesis mode, i.e., the pmf drives the synthesis of ATP. The mechanism involves the action of secondary transporters and is therefore termed secondary metabolic energy generation (7). The pmf is formed indirectly during the metabolic breakdown of weak acids. The anionic forms of the acids are transported into the cell by an electrogenic secondary carrier that translocates net negative charge into the cell, generating a membrane potential. The internal degradation of the substrate involves a decarboxylation step that consumes a scalar proton, which results in the formation of a pH gradient (11). The anions are taken up in exchange with a metabolic end product of the pathway (precursor/product exchange) or by a uniport mechanism, in which case the end product leaves the cell by passive diffusion.Examples of pathways using the exchange type of uptake are oxalate fermentation in Oxalobacter formigenes (1), malolactic fermentation in Lactococcus lactis (17), and histidine decarboxylation in Lactobacillus buchneri (15), and an example of a pathway using the uniporter mechanism is malate and citrate fermentation in the acidophilic bacterium Leuconostoc oenos (18,20).Cometabolism of glucose and citrate by the lactic acid bacterium Leuconostoc mesenteroides results in a growth advantage relative to growth on glucose alone. The increased growth rate is usually attributed to a metabolic shift in the heterofermentative pathway for glucose breakdown, yielding additional ATP (2, 4, 9, 21). In the absence of citrate, acetyl-P formed from glucose is reduced to ethanol, which balances the redox equivalents produced in the other steps of the phosphoketolase pathway (see also Fig. 1). In the presence of citrate, the redox equivalents are shuttled to pyruvate produced from citrate, yielding D-lactate, and acetyl-P is converted into acetate via the acetate kinase pathway, which results in the production of ATP. In a previous study in this laboratory, the cataly...