影响微生物致病机制的基因组和环境压力因素.pdf

1、The Genomic and Environmental Stressors that Impact Microbial PathogenesisAlvin LeeFood Safety Summit 2024Food Environment Physical/chemical environments ProductionProcessingPreservationStorageTransportationConsumption Microbiological quality evaluationsStandardized proceduresAntaris Consulting Adap

2、tedUn-adaptedpH 5.8pH 3.3pH 7.6pH 7.6pH 3.3Classic acid stress example by Foster&Hall in 90s on Salmonella ATRStress Adaptation“Asituationwherebyabriefexposuretoasuboptimal physical or chemical environment thatenables the cells to resist subsequent exposure tothe same or other types of harsher treat

3、ment towhich the species is normally susceptible.”Ray et alStress AdaptationRay et alTypes of StressBacterial cells alter lipid composition(membrane)Maintained fluid stateProportion of cyclopropane fatty acids in the cell membraneregulated by cyclopropane fatty acid synthaseLeads to Gram negative pr

4、essure,acid and oxidativeresistanceMechanisms of Stress AdaptationMechanisms of Stress AdaptationCurrent Concept:Gene Response Shock ProteinsStress ProteinsSpecific or nonspecific Inducible or constitutive Aid for adaptation to other stressorsRay et al Bacteria contain a primary factor that is respo

5、nsible for transcription ofhousekeeping genes necessary for growth and survival Many bacteria encode multiple alternative factorsThe level and activity of the alternative factors are highly regulated and can varydepending on environmental or developmental signals Example:rpo systems Usually regulate

6、d by a regulatory gene Gram(-)rpoH and rpoE for heat response and rpoS for general stress,celldensity and starvationStress-Related GenesSigma Factors E.coli can choose between 7 factors to fine tune its transcriptional outputJ.Helmann.Sigma factors in gene expression.2005;10.1038/npg.els.0003829Emer