Exam 3 - Microbiology Flashcards
complete virus particle
virion
what are some properties of viruses?
must have a host, can affect all cell types, and need to use an electron microscope to visualize it
The basic structure of viruses?
Nucleic acid and protein capsid
all virions contain a ___________
nucleocapsid
virions that have envelopes are called
enveloped viruses
virions lacking envelopes are called
naked viruses
what are capsids?
large macromolecular structures which serve as protein coat or virus
what do capsids do?
protect viral genetic material and aid in its transfer between host cells
what are capsids made up of?
protein subunits called protomers
what are the types of capsids?
helical, icosahedral, and complex
what is unique about the capsid of a bacteriophage?
it would be binal, and fall under complex because it has both icosahedral and helical
protein capsid and nucleic acid come together to make a
nucleocapsid
what do helical capsids look like?
shaped like hollow tubes with protein walls
what do icosahedral capsids look like?
a regular polyhedron with 20 equilateral faces and 12 vertices
what are examples of capsids with complex symmetry?
poxviruses and large bacteriophages
what is the envelope of a virus
outer, flexible, membranous layer of the virus
where do animal virus envelopes arise from?
host cell plasma or nuclear membranes
what are viral envelope proteins?
viral encoded and may project from the envelope surface as spikes or peplomers
what are viral envelope proteins used?
involved in viral attachment to host cell, used for identification of virus, may have enzymatic or other activity, may play a role in nucleic acid replication
what are the viral multiplication steps?
- attachment to host cell
- entry
- uncoating of genome
- synthesis
- assembly
- release
the turning of all or part of an organism in a particular direction in response to an external stimulus
tropism
receptor determines host preference, may be specific tissue
tropism
one reproductive choice
virulent phage
what does virulent phages do?
multiply immediately upon entry, lyse bacterial host cells
two reproductive options
temperate phages
what do temperate phages do?
reproduce lytically as virulent phages do, remain within host cell without destroying it
temperate phage changes phenotype of its host
lysogenic conversion
advantage to lysogeny for virus
phage remains viable but may not replicate
what are the three types of infection in eukaryotic cells?
cytocidal, persistent, cytopathic
what does cytocidal infection result in
cell death through lysis
persistent infections may last
years
cytopathic infections
degenerative changes, abnormalities
growth or lump of tissue
tumor
abnormal new cell growth and reproduction due to loss of regulation
neoplasia
reversion to a more primitive or less differentiated state
anaplasia
spread of cancerous cells throughout the body
metastasis
complex, multistep process that often involves oncogenes
carcinogenesis
cancer-causing genes, may come form the virus, may be transformed host proto-oncogenes which are involved in normal regulation of cell growth and differentiation
oncogenes
possible mechanisms by which viruses cause cancer
altered cell regulation, carry oncogene into cell and insert it into host genome, insertion of promoter or enhancer next to cellular proto-oncogene
virus belonging to papillomavirus family, nonenveloped icosehedral capsids, over 120 known viruses
HPV
what is the most common sexually transmitted disease?
HPV
HPV can infect by
infecting keratinocytes of skin or mucous membrane, warts, cancers
types of warts for HPV
plantar warts, verrucae vulgaris, anogenital codylomata
types of cancers with HPV
types 16, 18, 31, and 45; cervical (most common associated with HPV); degrade p53
Non-sexual transmission of HPV
direct contact, autoinoculation, prenatal
prevention of HPV
abstinence, condoms, vaccine
how many deaths is HIV responsible for
30 million
when was HIV first recognized by the CDC
1981
caused by human immunodeficiency virus; RNA virus family Retroviridae
Acquired Immune Deficiency Syndrome (AIDS)
how can you get HIV?
when infected blood, semen, or vaginal secretions come in contact with uninfected person’s broken skin or mucous membranes; mother to child; contaminated sharps/needles
what can’t you get HIV from?
urine, coughing, sharing utensils, tears, saliva, sweat, casual contact (hugs, kissing)
HIV Life Cycle
- Attachment
- Entry
- RNA –> DNA
- Integration into human genome as provirus
what happens in the attachment stage of HIV?
attaches to CD4 cells (T helper cells and other cells)
what happens in the RNA –> DNA stage of HIV?
reverse transcriptase
all HIV-infected individuals who have fewer than 200 CD4+ T cells/microliter of blood or a CD4+ cell percentage of lymphocytes of less than 14
AIDS
how to diagnose HIV?
viral isolation and culture; detect reverse transcriptase activity or viral antigens; detect anti-HIV antibodies in the blood; PCR - genome analysis
treatment for HIV?
no cure for AIDS; most successful treatment involves a combination of drugs
is there an available vaccine for HIV currently
no, but ongoing research
destruction or removal of all viable organisms
sterilization
killing, inhibition, or removal of disease causing (pathogenic) organisms
disinfection
agents, usually chemical, used for disinfection; usually used on inanimate objects
disinfectants
reduction of microbial population to levels deemed safe (based on public health standards)
sanitization
prevent of infection of living tissue by microorganisms
antisepsis
chemical agents that kill or inhibit growth of microorganisms when applied to tissue
antiseptics
use of chemicals to kill or inhibit growth of microorganisms within host tissue
chemotherapy
agents that kill microorganisms or inhibit their growth
antimicrobial agents
cidal agents ____
kill
static agents ______ ________
inhibit growth
conditions influencing the effectiveness of antimicrobial agent activity
population size, population composition, concentration or intensity of an antimicrobial agent, duration of exposure, temperature, local environment
how does population size effect antimicrobial agent activity
larger populations take longer to kill than smaller populations
how does population composition affect antimicrobial agent activity
microorganism differ markedly in their sensitivity to antimicrobial agents
physical control methods of microbial growth
heat, filtration, radiation
how does moist heat work?
destroys viruses, fungi, and bacteria; boiling will not destroy spores and does not sterilize; degrades nucleic acids, denatures proteins, and disrupts membranes
how does steam sterilization work?
must be carried out above 100 degrees using an autoclave; effective against all types of microorganisms including spores; quality control
how does pasteurization work?
controlled heating at temperatures well below boiling; used for milk, beer, and other beverages; process does not sterilize but does kill pathogenes present and slow spoilage by reducing the total load of organisms present
how does dry heat sterilization work?
less effective than moist heat sterilization, requiring higher temperatures and longer exposure times; oxidizes cell constituents and denatures proteins
what does dry heat incineration do
bench top incinerators are used to sterilize inoculating loops used in microbiology laboratories
how does filtration work
reduces microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms
ultraviolet radiation
wavelength of 260 is the most bactericidal; causes thymine dimers preventing replication and transcription
gamma radiation penetrates deep into objects; destroys bacterial endospores
ionizing radiation
what are the chemical control agents
disinfection, antisepsis, sterilization
when would you use moist sterilization
boil advisory
when would you use steam sterilization
liquids, solids, things that aren’t heat sensitive
when would you use dry sterilization?
glassware
when would you use filtration sterilizaiton?
antibiotics, vitamins, hormones
when would you use gamma radiation sterilization
food, plastic pipette, heat sensitive, sutures, plastic tubing
commonly used as laboratory and hospital disinfectants; act by denaturing proteins and disrupting cell membranes
phenolics
among the most widely used disinfectants and antispetics; bactericidal, fungicidal, but not sporicidal; denatures proteins and possibly dissolve membrane lipids
alcohols
any of five elements: fluorine, chlorine, bromine, iodine, and astatine; important antimicrobial agents
halogens
skin antispetic; oxidizes cell constituents and iodinates proteins; at high concentrations may kill spores
iodine
oxidizes cell constituents; important in disinfection of water; destroys vegetative bacteria and fungi
chlorine
detergents that have antimicrobial activity and are effective disinfectants
quaternary ammonium compounds
aldehydes are what
sporocidal drugs
what would you use to sterilize glass?
ethylene oxide and betapropiolactone
who discovered antibiotics?
Alexander Fleming
more than half of our antibiotics are produced by species of
streptomyces
narrow spectrum of microbial activity
affects gram-positive bacteria but few gram-negative
broad spectrum antibiotic
affects a broad range of gram-positive bacteria and gram-negative bacteria
lipopolysaccharide layer of gram-negative
porin channels
action of antimicrobial drugs
inhibits cell wall synthesis, protein synthesis, nucleic acid synthesis, synthesis of essential metabolites, and injures plasma membrane
common core structure of penicillin
B-lactam ring and side chain
inhibitors of the cell wall
penicillin, carbapenam, polypeptide(bacitracin and vancomycin)
what inhibits protein synthesis?
tetra, erthro, chloram, strepto
what inhibits the plasma membrane
polymyxin B
what inhibits DNA
Cipro
What inhibits RNA
rifampicin
what inhibits competitive inhibitors:
sulfa drugs
extracted from the culture of penicillium
natural penicillin
narrow spectrum of activity, drug of choice against staphlyococci, streptococci, and several species of spirochetes; acidity of stomach diminishes its concentration
Penicillin G
stable in the stomach
Penicillin V
created to overcome disadvantages of natural penicillins
semisynthetic penicillins
effective against many gram-negative and gram-positive; ampicillin and amoxicillin
extended-spectrum penicillin
interfere with DNA replication and RNA synthesis
nucleic acid synthesis
folic acid is necessary for synthesis of what
protein, DNA, and RNA
agents affect fungal sterols
antifungal drugs
what percentage of infectious illnesses are caused by viruses
60%
what percentage of infectious illnesses are caused by bacteria
15%
what are the target steps in viral infection
- entry and fusion inhibitors
- uncoating, genome integration, and nucleic acid synthesis inhibitors
- interference with assembly and release protease inhibitors
- exit inhibitors
test to guide chemotherapy
diffusion method
what is the disk-diffusion method
disk impregnated with known concentration of agent place don agar with organism
what cells are resistant to antimicrobial drugs
persister cells
bacteria resistant to a large number of antibiotics
superbugs
mechanisms of resistance
enzymatic destruction or inactivation of the drug, prevention of penetration to the target site within the microbe, alteration of the drug’s target site, rapid efflux of the antibiotic
enzymatic destruction or inactivation of the drgu
mainly affects antibiotics that are natural products
prevention of penetration
porin opening so molecules can’t pass into periplasmic space; gram-negative bacteria are usually more resistant
alteration of drug’s target site
modification of the target site which neutralizes the effects of antibiotics without significantly affecting cellular function
rapid efflux of antibiotics
proteins in the plasma membrane of gram-negative bacteria, pumps expel antibiotics, pump normally there to eliminate toxic substances
