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Growth Limits (growth + limit)
Selected AbstractsGENERATION OF BIOLUMINESCENT MORGANELLA MORGANII AND ITS POTENTIAL USAGE IN DETERMINATION OF GROWTH LIMITS AND HISTAMINE PRODUCTIONJOURNAL OF FOOD SAFETY, Issue 2 2009MEHDI ZAREI ABSTRACT A mini-Tn5 promoter probe carrying the intact lux operon of Photorhabdus luminescens (pUT mini-Tn5 luxCDABE) which allowed measurement of light output without the addition of exogenous substrate was constructed. It was used to create a pool of chromosomally lux -marked strains of Morganella morganii. Also plasmid-mediated expression of bioluminescence in M. morganii was assessed using plasmid pT7-3 luxCDABE. No significant differences in growth and histamine formation characteristics of the lux -marked strains and wild type M. morganii strain were observed. Luminescent strain of M. morganii was used in experiments in which the correlation between light output, viable cell count and histamine formation was assessed. During the exponential growth phase, a positive linear correlation was observed between these three parameters in trypticase soy broth-histidine medium at 37C. It was demonstrated that expression of bioluminescence had not had a significant effect upon both growth rate and histamine production. Thus, the measurement of bioluminescence was found to be a simple, fast and reliable method for determination of viable cell count and histamine content. PRACTICAL APPLICATIONS Constructing predictive models in microbiology requires a large number of data on desired factors. Commonly used traditional methods of counting viable cells and measuring histamine, e.g., to model the growth limits of M. morganii as a function of different intrinsic and extrinsic factors, are time consuming and laborious, and require a lot of laboratory space and materials. According to the results of this research, measurement of bioluminescence is a simple, fast and reliable method for the determination of viable cell count and histamine content during the exponential growth phase. Thus, it can be used as a labor- and material-saving selective data capture method for constructing predictive models in many different areas. [source] The growth limits of a large number of Listeria monocytogenes strains at combinations of stresses show serotype- and niche-specific traitsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008S. Van Der Veen Abstract Aims:, The aim of this study was to associate the growth limits of Listeria monocytogenes during exposure to combined stresses with specific serotypes or origins of isolation, and identify potential genetic markers. Methods and Results:, The growth of 138 strains was assessed at different temperatures using combinations of low pH, sodium lactate, and high salt concentrations in brain heart infusion broth. None of the strains was able to grow at pH , 4·4, aw , 0·92, or pH , 5·0 combined with aw , 0·94. In addition, none of the strains grew at pH , 5·2 and NaLac , 2%. At 30°C, the serotype 4b strains showed the highest tolerance to low pH and high NaCl concentrations at both pH neutral (pH 7·4) and mild acidic conditions (pH 5·5). At 7°C, the serotype 1/2b strains showed the highest tolerance to high NaCl concentrations at both pH 7·4 and 5·5. Serotype 1/2b meat isolates showed the highest tolerance to low pH in the presence of 2% sodium lactate at 7°C. ORF2110 and gadD1T1 were identified as potential biomarkers for phenotypic differences. Conclusions:, Differences in growth limits were identified between specific L. monocytogenes strains and serotypes, which could in some cases be associated with specific genetic markers. Significance and Impact of the Study:, Our data confirm the growth limits of L. monocytogenes as set out by the European Union for ready-to-eat foods and provides an additional criterion. The association of L. monocytogenes serotypes with certain stress responses might explain the abundance of certain serotypes in retail foods while others are common in clinical cases. [source] GENERATION OF BIOLUMINESCENT MORGANELLA MORGANII AND ITS POTENTIAL USAGE IN DETERMINATION OF GROWTH LIMITS AND HISTAMINE PRODUCTIONJOURNAL OF FOOD SAFETY, Issue 2 2009MEHDI ZAREI ABSTRACT A mini-Tn5 promoter probe carrying the intact lux operon of Photorhabdus luminescens (pUT mini-Tn5 luxCDABE) which allowed measurement of light output without the addition of exogenous substrate was constructed. It was used to create a pool of chromosomally lux -marked strains of Morganella morganii. Also plasmid-mediated expression of bioluminescence in M. morganii was assessed using plasmid pT7-3 luxCDABE. No significant differences in growth and histamine formation characteristics of the lux -marked strains and wild type M. morganii strain were observed. Luminescent strain of M. morganii was used in experiments in which the correlation between light output, viable cell count and histamine formation was assessed. During the exponential growth phase, a positive linear correlation was observed between these three parameters in trypticase soy broth-histidine medium at 37C. It was demonstrated that expression of bioluminescence had not had a significant effect upon both growth rate and histamine production. Thus, the measurement of bioluminescence was found to be a simple, fast and reliable method for determination of viable cell count and histamine content. PRACTICAL APPLICATIONS Constructing predictive models in microbiology requires a large number of data on desired factors. Commonly used traditional methods of counting viable cells and measuring histamine, e.g., to model the growth limits of M. morganii as a function of different intrinsic and extrinsic factors, are time consuming and laborious, and require a lot of laboratory space and materials. According to the results of this research, measurement of bioluminescence is a simple, fast and reliable method for the determination of viable cell count and histamine content during the exponential growth phase. Thus, it can be used as a labor- and material-saving selective data capture method for constructing predictive models in many different areas. [source] Primary growth and morphological markers of interannual growth limits in Cupressaceae from PatagoniaBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2004JAVIER GROSFELD The present study shows experimentally that primary growth of the native Patagonian Cupressaceae Austrocedrus chilensis (D. Don) Pic.-Serm et Bizz., Fitzroya cupressoides (Molina) I. M. Johnst. and Pilgerodendron uviferum (D. Don) Florin is potentially continuous. External morphological markers of interannual growth limits have been identified for the main axes of these species after several years of observation. Such limits correspond with axis portions in which internodes are relatively short and leaves have a small distal free end forming an acute angle with the axis. The causality of these results and their utility for studying the productivity, adaptation to different environments, population management and conservation of these threatened species are discussed. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 146, 285,293. [source] | ||||||||||