A method was developed for the detection of the fecal coliform bacterium Escherichia coli, using the polymerase chain reaction and gene probes, based on amplifying regions of the uid gene that code for 1,-glucuronidase, expression of which forms the basis for fecal coliform detection by the commercially available Colilert method. Amplification and gene probe detection of four different regions of uid specifically detected E. coli and Shigella species, including B-glucuronidase-negative strains of E. coli; no amplification was observed for other coliform and nonenteric bacteria.

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Polymerase chain reaction (PCR) amplification and gene probe detection of regions of two genes, lacZ and lamB, were tested for their abilities to detect coliform bacteria. Amplification of a segment of the coding region of Escherichia coli lacZ by using a PCR primer annealing temperature of 50°C detected E. coli and other coliform bacteria (including Shigella spp.) but not Salmonella spp. and noncoliform bacteria. Amplification of a region of E. coli lamB by using a primer annealing temperature of 50°C selectively detected E. coli and Salmonella and Shigella spp. PCR amplification and radiolabeled gene probes detected as little as 1 to 10 fg of genomic E. coli DNA and as few as 1 to 5 viable E. coli cells in 100 ml of water. PCR amplification of lacZ and lamB provides a basis for a method to detect indicators of fecal contamination of water, and amplification of lamB in particular permits detection of E. coli and enteric pathogens (Salmonella and Shigella spp.) with the necessary specificity and sensitivity for monitoring the bacteriological quality of water so as to ensure the safety of water supplies.

Background:Researchers typically search for disease markers using a "targeted" approach in which a hypothesis about the disease mechanism is tested and experimental results either confirm or disprove the involvement of a particular gene or protein in the disease. Recently, there has been interest in developing disease diagnostics based on unbiased quantification of differences in global patterns of protein and peptide masses, typically in blood from individuals with and without disease. We combined a suite of methods and technologies, including novel sample preparation based on carrier-protein capture and biomarker enrichment, highresolution mass spectrometry, a unique cohort of wellcharacterized persons with and without Alzheimer disease (AD), and powerful bioinformatic analysis, that add statistical and procedural robustness to biomarker discovery from blood. Methods: Carrier-protein-bound peptides were isolated from serum samples by affinity chromatography, and peptide mass spectra were acquired by a matrixassisted laser desorption/ionization (MALDI) orthogo-

To detect low levels of microorganisms in environmental samples by using polymerase chain reaction (PCR)-gene probe detection, samples were concentrated by filtration. Fluoropore (Millipore Corp.) filters were compatible with PCR DNA amplification, whereas various other filters including nitrocellulose and cellulose acetate filters inhibited PCR amplification. By concentrating cells on Fluoropore filters and releasing the DNA by freeze-thaw cycling, PCR DNA amplification could be performed without removing the filter. Concentration with Fluoropore FHLP and FGLP filters permitted the detection of single cells of microorganisms in 100-ml samples by PCR-gene probes.