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Effect of Length of Time before Incorporation on Survival of Pathogenic Bacteria Present in Livestock Wastes Applied to Agricultural Soil. M. L. Hutchison, 2004.In response to reports that the contamination of food can occur during the on-farm primary phase of food production, we report data that describes a possible cost-effective intervention measure . The effect of time before soil incorporation of livestock wastes spread to land on the rate of decline of zoonotic agents present in the waste was investigated . Fresh livestock wastes were inoculated with laboratory-cultured Salmonella, Listeria, and Campylobacter spp . and Escherichia coli O157 before they were spead onto soil . Incorporation of the spread wastes was either immediate, delayed for 1 week, or did not occur at all . Bacterial decline was monitored over time and found to be significantly more rapid for all waste types when they were left on the soil surface . There were no significant differences in initial bacterial decline rates when wastes were spread in summer or winter . Our results indicate that not incorporating contaminated livestock wastes into soil is a potential intervention measure that may help to limit the spread of zoonotic agents further up the food chain . The implications of these findings are discussed in relation to current advice for livestock waste disposal . The NorR Protein of Escherichia coli Activates Expression of the Flavorubredoxin Gene norV in Response to Reactive Nitrogen Species. Matthew I. Hutchings, 2002.The Escherichia coli norVW genes encode a flavorubredoxin and NADH:(flavo)rubredoxin reductase, respectively, which are involved in nitric oxide detoxification under anaerobic growth conditions . Here it is shown that the norVW genes also have a role in protection against reactive nitrogen intermediates generated from nitroprusside . Transcription from the norV promoter is activated by the presence of nitroprusside in the growth medium; activation requires the product of a divergently transcribed regulatory gene, norR . Two "Wild-Type" Variants of Escherichia coli  70: Context-Dependent Effects of the Identity of Amino Acid 149.Nicole E. Baldwin, 2002.The identity of amino acid 149 of Escherichia coli 70 has been reported variably as either arginine or aspartic acid . We show that the behavior of both a region 1.2 deletion and a single-amino-acid substitution at position 122 are greatly affected by the identity of amino acid 149 .
Cloning and Analysis of a DNA Fragment Stimulating Avermectin Production in Various Streptomyces avermitilis Strains. Yong-Soon Hwang, 2003.To isolate a gene for stimulating avermectin production, a genomic library of Streptomyces avermitilis ATCC 31267 was constructed in Streptomyces lividans TK21 as the host strain . An 8.0-kb DNA fragment that significantly stimulated actinorhodin and undecylprodigiosin production was isolated . When wild-type S . avermitilis was transformed with the cloned fragment, avermectin production increased approximately 3.5-fold . The introduction of this fragment into high-producer (ATCC 31780) and semi-industrial (L-9) strains also resulted in an increase of avermectin production by more than 2.0- and 1.4-fold, respectively . Subclones were studied to locate the minimal region involved in stimulation of pigmented-antibiotic and avermectin production . An analysis of the nucleotide sequence of the entire DNA fragment identified eight complete and one incomplete open reading frame . All but one of the deduced proteins exhibited strong homology (68 to 84% identity) to the hypothetical proteins of Streptomyces coelicolor A3(2) . The orfX gene product showed no significant similarity to any other protein in the databases, and an analysis of its sequence suggested that it was a putative membrane protein . Although the nature of the stimulatory effect is still unclear, the disruption of orfX revealed that this gene was intrinsically involved in the stimulation of avermectin production in S . avermitilis . The Curing Agent Sodium Nitrite, Used in the Production of Fermented Sausages, Is Less Inhibiting to the Bacteriocin-Producing Meat Starter Culture Lactobacillus curvatus LTH 1174 under Anaerobic Conditions. Jurgen Verluyten, 2003.Curvacin A is a listericidal bacteriocin produced by Lactobacillus curvatus LTH 1174, a strain isolated from fermented sausage . The response of this strain to an added curing agent (sodium nitrite) in terms of cell growth and bacteriocin production was investigated in vitro by laboratory fermentations with modified MRS broth . The strain was highly sensitive to nitrite; even a concentration of 10 ppm of curing agent inhibited its growth and both volumetric and specific bacteriocin production . A meat simulation medium containing 5 ppm of sodium nitrite was tested to investigate the influence of the gas phase on the growth and bacteriocin production of L . curvatus LTH 1174 . Aerating the culture during growth had no effect on biomass formation, but the oxidative stress caused a higher level of specific bacteriocin production and led to a metabolic shift toward acetic acid production . Anaerobic conditions, on the other hand, led to an increased biomass concentration and less growth inhibition . Also, higher maximum volumetric bacteriocin activities and a higher level of specific bacteriocin production were obtained in the presence of sodium nitrite than in fermentations under aerobic conditions or standard conditions of air supply . These results indicate that the inhibitory effect of the curing agent is at least partially masked under anaerobic conditions .
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