Abstract: The present invention provided compositions, methods and kits for detection and quantitation of pathogenic organisms. The composition of the invention is an oligonucleotide probe comprising a bacteriophage covalently linked to one site on an oligonucleotide probe complementary to a conserved region of a pathogenic organism. At a second site, the oligonucleotide probe is linked to a matrix. The oligonucleotide probe contains a region complementary to one strand of a restriciton endonuclease recognition site or an oligoribonucleotide moiety. The number of pathogenic organisms present in a biological fluid sample may be quantitated in accordance with the method of the invention by combining the composition of the invention with the sample, allowing hybridization to occur. Hybridization generates a DNA-RNA hybrid, and by adding the appropriate nucleolytic enzyme capable of cleaving DNA-RNA hybrids; bacteriophage will be released for measurement.

Abstract: Disclosed is a protein construct including a chemically modified lambdoid tail protein having a chemically reactive amino acid residue linked to a target molecule. Also disclosed is an infective lambdoid bacteriophage displaying on its outer surface the chemically modified tail protein. In addition, methods of detecting a molecule-of-interest in a solution and methods of detecting cells producing a molecule-of-interest which utilize the infective lambdoid bacteriophage having the chemically modified tail protein are disclosed.

Abstract: Disclosed is an infective lambdoid bacteriophage which includes a protein construct comprising a genetically modified major tail protein truncated at its carboxy terminus, and a target molecule peptide bonded to the carboxy terminus of the tail protein. Also disclosed are nucleic acids encoding the construct and methods of detecting a molecule-of-interest in a solution and of detecting a cell which produces a molecule-of-interest.

Abstract: Disclosed is a method for isolating a mutant cell that excretes a desired compound. The method includes culturing a plurality of auxotrophic pretreated starter cells and auxotrophic feeder cells in the presence of a reversibly noninfective, modified lambdoid bacteriophage. If the treated starter cell produces the desired compound, the bacteriophage will be rendered infective and infect the feeder cell. The feeder cell, in turn, will excrete a metabolite required by the starter cell and the starter cell will excrete a metabolite required by the feeder cell, enabling the cells to cross-feed, grow, and produce a colony containing a starter cell which produces the desired compound.

Abstract: Disclosed is a method for isolating a mutant cell that secretes a desired compound at a level greater than that secreted by a starter cell from which the mutant cell is derived. The method includes contacting a plurality of auxotrophic feeder cells and auxotrophic starter cells together in the solid growth medium. The starter cells produce the desired compound required by the feeder cells and the feeder cells produce a metabolite required by the starter cells. These cells are cultured to produce a plurality of primary colonies, the largest of which include at least one of the mutant cells which overproduces the desired compound.