Lecture+11+Viruses++_color_

Lecture+11+Viruses++_color_ -...

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http://www.youtube.com/watch?v=XnSEDkXIpjw Viruses February 3, 2012 FST104
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B. Food-borne viruses are more difficult to culture than bacteria And are more difficult to detect: Electron microscopy (to visualize it) Antibodies PCR (nucleic acid) Properties of Viruses Obligate parasites •Do not grow on laboratory culture media •Require living cells for propagation (examples: tissue culture and chick embryos) C. Food-borne viruses do not form “natural” taxonomic groups Properties of Viruses International Committee on Taxonomy of Viruses ( ICTV ) Based on nucleotide sequence comparisons http://www.ictvonline.org/virusTaxInfo.asp 2285 species of virus
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Components of viruses Capsid proteins Nucleic Acid dsDNA ssDNA dsRNA (+)ssRNA (-)ssRNA ssRNA-RT dsDNA-RT D. All food-borne viral pathogens are “Naked” (lack a lipid envelope) Enveloped and Naked viruses
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Viruses have different structural forms http://www.microbelibrary.org/images/kaiser/viral%20cycle/viral_life_cycle.html Naked viruses share similar life cycles Life cycles of naked viruses
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bacterial pathogens Some can even survive moderate chlorination procedures Food-borne viruses survive weeks to months in water supplies Virus survival Endospores > Naked > Gm+ bacteria > G- bacteria> Enveloped Survive disinfection, freezing, and acid pH Stress survival (vegetative) viruses viruses Control of food/water borne viruses Keep viruses out of food by using good food handling hygiene Prevent harvest of shellfish from polluted water Use heat to kill viruses (>60 degrees C)
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Lecture+11+Viruses++_color_ -...

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