The U.V. sensitivity of bacteria: its relation to the DNA replication cycle

Author: Hanawalt, P.C. Description: A striking increase in the shoulder of the UV survival curve but no change in the limiting slope is obtained when cultures of Escherichia coli strain TAU complete the DNA replication cycle in the absence of concommitant protein synthesis prior to irradiation. The UV sensitivity of protein synthesis or RNA synthesis is not altered significantly by this treatment. In contrast to the result for strain TAU, there is no significant change in the UV survival curve for the UV sensitive E. coli Bs-1 when its DNA…

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Microfluidic droplet application for bacterial surveillance in fresh-cut produce wash waters

Author: Harmon, J.B.; Gray, H.K.; Young, C.C.; Schwab, K.J. Description: Foodborne contamination and associated illness in the United States is responsible for an estimated 48 million cases per year. Increased food demand, global commerce of perishable foods, and the growing threat of antibiotic resistance are driving factors elevating concern for food safety. Foodborne illness is often associated with fresh-cut, ready-to-eat produce commodities due to the perishable nature of the product and relatively minimal processing from farm to the consumer. The research presented here optimizes and evaluates the utility of microfluidic…

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Survey of microbial quality of plant-based foods served in restaurants

Author: Sospedra, I.; Rubert, J.; Soriano, J.M.; Mañes, J. Description: This study was carried out to evaluate the microbiological quality of plant-based foods obtained from foodservice establishments. The samples included cereals, legumes, fruits and vegetables. According to the European Commission Regulation (No. 2073/2005 and No. 1441/2007) and Spanish microbiological criteria (No. 3484/2000), vegetables were the plant-based dishes where more samples exceed the adopted limits of mesophilic aerobic counts and Enterobacteriaceae. Furthermore, Staphylococcus aureus and Escherichia coli were also found in several vegetable dishes. E. coli and Salmonella spp. were detected…

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Detection of hepatitis E virus and other livestock-related pathogens in Iowa streams

Author: Givens, C.E.; Kolpin, D.W.; Borchardt, M.A.; Duris, J.W.; Moorman, T.B.; Spencer, S.K. Description: Manure application is a source of pathogens to the environment. Through overland runoff and tile drainage, zoonotic pathogens can contaminate surface water and streambed sediment and could affect both wildlife and human health. This study examined the environmental occurrence of gene markers for livestock-related bacterial, protozoan, and viral pathogens and antibiotic resistance in surface waters within the South Fork Iowa River basin before and after periods of swine manure application on agricultural land. Increased concentrations of…

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Grapefruit juice and its furocoumarins inhibits autoinducer signaling and biofilm formation in bacteria

Author: Girennavar, B.; Cepeda, M.L.; Soni, K.A.; Vikram, A.; Jesudhasan, P.; Jayaprakasha, G.K.; Pillai, S.D.; Patil, B.S. Description: Cell-to-cell communications in bacteria mediated by small diffusible molecules termed as autoinducers (AI) are known to influence gene expression and pathogenicity. Oligopeptides and N-acylhomoserine lactones (AHL) are major AI molecules involved in intra-specific communication in gram-positive and gram-negative bacteria respectively, whereas boronated-diester molecules (AI-2) are involved in inter-specific communication among both gram-positive and gram-negative bacteria. Naturally occurring furocoumarins from grapefruit showed >95% inhibition of AI-1 and AI-2 activities based on the Vibrio…

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Improved M13 phage cloning vectors and host strains: nucleotide sequences of the M13mp18 and pUC19 vectors

Author: Yanisch-Perron, C.; Vieira, J.; Messing, J. Description: Three kinds of improvements have been introduced into the M13-based cloning systems. (1) New Escherichia coli host strains have been constructed for the E. coli bacteriophage M13 and the high-copy-number pUC-plasmid cloning vectors. Mutations introduced into these strains improve cloning of unmodified DNA and of repetitive sequences. A new suppressorless strain facilitates the cloning of selected recombinants. (2) The complete nucleotide sequences of the M13mp and pUC vectors have been compiled from a number of sources, including the sequencing of selected segments….

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Rat insulin genes: construction of plasmids containing the coding sequences

Author: Ullrich, A.; Shine, J.; Chirgwin, J.; Pictet, R.; Tischer, E.; Rutter, W.J.; Goodman, H.M. Description: Recombinant bacterial plasmids have been constructed that contain complementary DNA prepared from rat islets of Langerhans messenger RNA. Three plasmids contain cloned sequences representing the complete coding region of rat proinsulin I, part of the preproinsulin I prepeptide, and the untranslated 3′ terminal region of the mRNA. A fourth plasmid contains sequences derived from the A chain region of rat preproinsulin II. Subject headings: Animals; Base Sequence; Codon; DNA/isolation & purification; DNA Restriction Enzymes/metabolism;…

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Isolation and characterization of efficient plasmid transformation mutants of Mycobacterium smegmatis

Author: Snapper, S.B.; Melton, R.E.; Mustafa, S.; Kieser, T.; Jacobs, W.R.J. Description: Recent development of vectors and methodologies to introduce recombinant DNA into members of the genus Mycobacterium has provided new approaches for investigating these important bacteria. While most pathogenic mycobacteria are slow-growing, Mycobacterium smegmatis is a fast-growing, non-pathogenic species that has been used for many years as a host for mycobacteriophage propagation and, recently, as a host for the introduction of recombinant DNA. Its use as a cloning host for the analysis of mycobacterial genes has been limited by…

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Membrane protein architects: the role of the BAM complex in outer membrane protein assembly

Author: Knowles, T.J.; Scott-Tucker, A.; Overduin, M.; Henderson, I.R. Description: The folding of transmembrane proteins into the outer membrane presents formidable challenges to Gram-negative bacteria. These proteins must migrate from the cytoplasm, through the inner membrane and into the periplasm, before being recognized by the beta-barrel assembly machinery, which mediates efficient insertion of folded beta-barrels into the outer membrane. Recent discoveries of component structures and accessory interactions of this complex are yielding insights into how cells fold membrane proteins. Here, we discuss how these structures illuminate the mechanisms responsible for…

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Synergistic actions of Rad51 and Rad52 in recombination and DNA repair

Author: Benson, F.E.; Baumann, P.; West, S.C. Description: In the yeast Saccharomyces cerevisiae, mutations in the genes RAD51 or RAD52 result in severe defects in genetic recombination and the repair of double-strand DNA breaks. These genes, and others of the RAD52 epistasis group (RAD50, RAD54, RAD55, RAD57, RAD59, MRE11 and XRS2), were first identified by their sensitivity to X-rays. They were subsequently shown to be required for spontaneous and induced mitotic recombination, meiotic recombination, and mating-type switching. Human homologues of RAD50, RAD51, RAD52, RAD54 and MRE11 have been identified. Targeted…

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