Acellular microbes Flashcards
the smallest virus is about the size of
large hemoglobin molecule of RBC
genome of a typical virion consists of
either DNA or RNA surrounded by capsid
nucleocapsid =
nucleic acid + capsid (protein coat)
features that distinguish viruses from living organisms
- lack of enzymes necessary in energy production
- unable to replicate on their own
- depend on the resources of host cells
which type of viruses is more resistance to adverse conditions, why?
nonenveloped (naked) viruses, since attachment proteins are on the capsid (stronger than envelope)
single-stranded positive sense RNA functions as
mRNA in viruses
Bacteriophages
bacterial viruses (viruses that infect bacteria)
vibrio cholera
virulent bacteriophages
always causes a lytic cycle which ends with the destruction of the bacterial cell
temperate phages (lysogenic)
Their DNA remains integrated into the bacterial cell chromosome
do not immediately initiate the lytic cycle like Virulent bacteriophages
latent virus
viruses that do not initiate biosynthesis right away
cold sores (latent virus infections)
cold sores (fever blisters)
Caused by Herpes simplex virus I (HSV I)
the cold sores come and go
what are the triggers for latent virus infections
fever, sunlight, or excessive stress
genital herpes
caused by Herpes simplex virus II (HSV II)
shingles
painful nerve disease
Caused by Varicella zoster virus (VZV)
Causes chickenpox (Varicella) as primary infection
when the body’s immune defenses become weakened by old age or disease, the latent chickenpox virus resurfaces to cause shingles (zoster)
Epstein-Barr virus (EBV)
a type of herpes virus
causes infectious mononucleosis (not a type of cancer)
causes three types of human cancers:
a-nasopharyngeal carcinoma
b-Burkitt lymphoma
c- B-cell lymphoma
human herpesvirus 8 (HHV-8)
Kaposi carcinoma: cancer common in AIDS
hepatitis B and C (HBV or HCV)
hepatocellular (liver) carcinoma
Human papillomavirus (HPV) (DNA VIRUS)
Causes cervical cancer and other parts of the genital tract
Retrovirus (RNA virus)
They have enzyme reverse transcriptase which turns RNA to DNA which
is integrated into the host cell genome
● They have long incubation periods
● Examples:
a. HIV→ AIDS → making patients immunocompromised and more
prone to cancers
b. Human T-lymphotropic virus type 1 → causes T-cell leukemia
to what receptor does HIV bind to
CD4
anti-P24 antibodies
very specific test to identify HIV
marker: major capsid protein (p24)
Mimivirus
giant virus recovered from amebas (host)
‘mimics’ bacteria
contain DNA and RNA
Megavirus
has the largest capsid diameter (440 nm)
the largest and most complex genome of all viruses
inclusion bodies
remnants viruses seen in infected cells
used as a diagnostic tool
cytoplasmic inclusion bodies
- negri bodies (in nerve cells) → seen in rabies
- Guarnieri bodies → in smallpox
- Inclusion bodies seen in AIDS or HIV
intranuclear inclusion bodies
- Owl eyes → seen in cytomegalovirus
- Herpes virus and poliovirus inclusion bodies
antiviral agents
drugs used to treat viral infections
disrupts critical phases in viral cycle
viroids
infectious RNA molecules (only in plants)
smaller than viruses
Prions
small infectious proteins that convert normal protein molecules into non-functional ones
Ebola virus
transmitted by bats, causes hemorrhagic fever, high mortality
Zika virus
transmitted by mosquitoes
responsible for a large number of birth defects
