tailieunhanh - Nature and Properties of Micro-organisms

Smallest to largest Prions Viruses Bacteria Fungi | Nature and Properties of Micro-organisms Nature and Properties of Micro-organisms Laura JV Piddock Smallest to largest Prions Viruses Bacteria Fungi Prions Infectious protein No DNA or RNA Normal cellular form of protein vs. pathological form Pathological form found in neural tissue and tonsils PrP-C & PrP-Sc Pathology Spongiform encephalopathy: transmissible, familial Transmission: oral, operative (neural tissue, dura, corneas), ??? blood Resistance to disinfectants Formaldehyde increases infectivity Viruses DNA or RNA Shell of protein (capsid) surrounding nucleic acid Classification on basis of nucleic acid DNA viruses: eg Herpes simplex virus (HSV) RNA viruses: eg influenza virus DNA viruses: herpes simplex virus (HSV) RNA viruses: Influenza Viruses Obligate intracellular parasites Use host cell for nucleic acid and protein synthesis Cell attachment: target for blocking antibody vaccines Intracellular replication: target for antiviral drugs . retroviruses (RNA) . HIV RNA DNA Viral effects on host cells Degeneration (cytopathic effect): CMV Cell lysis Cell fusion, syncytia formation: RSV Cell proliferation Transformation: malignancy (parvoviruses) Latent infection - no sign of infection until reactivation ‘cold sores’ (HSV) chickenpox shingles (VZV) CMV hepatitis owl eye effect inclusion body Varicella zoster virus (VZV) VZV: Chickenpox VZV: Shingles Re-activation of latent infection Suppression of cell mediated immunity Bacteria Unicellular, prokaryotes DNA and RNA Binary fission No mitochondria Rigid cell wall containing peptidoglycan Eubacteria Classified according to: size & shape cell wall (Gram stain) aerotolerance Gram stain reaction positive - purple negative - pink Shape coccus - round (chains? clusters?) bacillus - rod Wound swab: S. .