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Microbiology > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

viruses

A
  • infects humans, animal, plants, fungi, protozoa, algae, and bacterial cells
  • consist of a genome of either DNA or RNA and surrounded by capsid composed of copsomeres
  • enveloped or noneveloped
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2
Q

virions

A

complete virus particles

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3
Q

virus sizes

A

10-300 nm

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4
Q

capsid

A

protein coat surrounding DNA/RNA

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5
Q

capsomeres

A

individual protein units that make of capsid

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6
Q

envelope

A

outer envelope composed of lipids and polysaccharides

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7
Q

5 properties that distinguish viruses form living cells

A

1) have either DNA or RNA (living have both)
2) unable to replicate on their own
3) do not divide by binary fission, mitosis, or meiosis
4) lack genes/enzyme necessary for energy production
5) depend on ribosomes, enzymes, and metabolites of host cells for protein and nucleic acid production

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8
Q

enveloping process

A

1) virus transported to host cell membrane
2) cytoplasm of membrane proteins bind nucleocapsid
3) nucleocapsid enveloped by host cell membrane
4) host cell provides viral envelope through budding process
5) host cell releases enveloped vision

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9
Q

how viruses are classified (8)

A
  • type of genetic material (DNA or RNA)
  • shape and size of capsid
  • number of capsomeres
  • enveloped or non-eveloped
  • hype of host it infects
  • disease it produces
  • target cells
  • immunologic/antigenetic properties
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10
Q

type of genetic material

A
  • double stranded DNA
  • single stranded RNA
  • single stranded DNA
  • double stranded RNA
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11
Q

shape and size of capsid

A
  • most viral genomes are circular but some are linear
  • bacteriophages are smallest
  • E. coli is very large
  • variability and wide degree of sizes
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12
Q

bacteriophages (phages)

A
  • viruses that infect bacteria

- virulent and temperate bacteriophages

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13
Q

virulent bacteriophages

A
  • always cause the lytic cycle which ends in destruction of bacterial cell
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14
Q

lytic cycle steps (5)

A

1) attachment
2) penetration (injection of DNA)
3) biosynthesis
4) assembly
5) release

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15
Q

steps of multiplication fo animal viruses

A

1) attachment
2) penetration
3) uncoating (need to penetrate nucleus)
4) biosynthesis
5) assembly

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16
Q

how to animal viruses escape from host cell?

A
  • through either cell lysis or by budding

- viruses that escape by budding become enveloped viruses

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17
Q

latent virus infection

A
  • viral infections in which the virus hides from hosts immune system by entering cells and tissues and remaining dormant
  • immunosuppression can cause flareup
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18
Q

latent virus infection example

A
  • herpers
  • once acquired it stores away and never completely goes away
  • chicken pox may be followed years later by shingles as its the same virus
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19
Q

antiviral agents

A
  • antibiotics are not effective against viral infections
  • antivirals are drugs used to treat viral infections
  • interfere with virus-specific enzymes and virus production by disrupting critical multiplication phases or inhibiting synthesis or DNA/RNA/proteins
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20
Q

oncogenic viruses (oncoviruses)

A
  • viruses that cause cancer

- include: Epstein-Barr virus, HPV (cervical cancer), human T-lymphotropic virus type 1 (leukemias)

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21
Q

human immunodeficiency virus (HIV)

A
  • causes acquired immunodeficiency syndrome (AIDS)
  • enveloped single-stranded RNA virus
  • primary target are CD4+ cells (helper cells) aka T-lymphocytes
  • undergoes reverse transcriptase
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22
Q

reverse transcriptase

A
  • enzyme that transforms RNA to DNA in order to integrate into host DNA
  • if it can’t do this then it can’t infect the cell
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23
Q

viroids

A
  • short, naked fragments of single-stranded RNA which can interfere with metabolism of plants
  • transmitter between plants in same manner as viruses
  • ex: spindle tuber and citrus exocortis
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24
Q

prions

A
  • small infectious proteins that cause fatal neurological diseases in animals and humans
  • most resistant to disinfectants
  • mechanism of disease causation is unknown
  • ex: scrapes, bonnie spongiform encephalopathy (mad cow disease), and Creutzfeldt-Jacob disease
25
Q

3 major phenotypic categories of bacteria

A
  • gram - with cell wall
  • gram + with cell wall
  • lacking cell wall (mycoplasma spp.)
26
Q

classification groups of bacteria (10)

A
  • cell morphology (shape)
  • staining reactions
  • motility
  • colony morphology
  • atmospheric requirement
  • nutritional requirements
  • biochemical and metabolic activities
  • enzyme produces
  • pathogenicity
  • genetic composition
27
Q

cell morphology

A
  • cocci (round)
  • bacilli (rods)
  • curved and spiral
28
Q

cocci

A
  • average 1um
  • singly
  • in pairs (diplococci) gonorrhoea
  • in chains (streptococci) strep throat
  • in clusters (staphylococci) boils
  • packets of 4 (tetrad)
    packets of 8 (octad)
29
Q

bacilli

A
  • short, long, thin, thick, pointed, or curved
  • average 1 x 3um
  • singly
  • in pairs (diplobacilli)
  • in chains (streptobacilli)
  • in long filaments
  • or branched
  • ex: escherichia, klebsiella, proteus, pseudomonas, haemophilus, and bacillus spp.
30
Q

coccobacilli

A
  • extremely short bacilli
31
Q

curved bacteria

A
  • vibrio spp., campylobacter spp., helicobacter spp.
32
Q

spiral bacteria

A

treponema spp, borrelia spp. (causes relapsing fever)

33
Q

3 categories of staining procedures

A

1) simple
2) structural (capsule, spore, flagella)
3) differential (gram and acid-fast)

34
Q

bacteria staining

A
  • bacterial smears must be fixed prior to staining

- fixation process serves to kill organisms, preserve their morphology, and anchor smear to slide

35
Q

two most common fixation techniques

A

1) heat fixation - not standardized, excess heat will distort morphology
2) methanol fixation - standardized, preferred method, removes water from bacteria

36
Q

gram staining procedure

A
  • divides bacteria into gram +/-
  • gram + = blue/purple
  • gram - = pink/red
  • gram + cell wall have thick peptidoglycan making it difficult to remove violet-iodine complex
  • gram - cell wall have thin peptidoglycan making it easier to remove crystal violet, cells are subsequently stained with safranin (ethanol removes iodine)
37
Q

acid-fast staining procedure

A
  • some bacteria are neither purple or pink after gram staining and known as gram-variable bacteria (mycobacterium spp.)
  • often identified using acid-fast stain
  • carbol fuchsin is red dye driven through bacterial cell wall with heat
  • heat softens cell wall
  • mycobacteria are not decolonized by acid-alcohol mixture so they are acid-fast
38
Q

motility

A
  • if bacteria are able to swim they are motile
  • often associated with flagella and less often with axial filaments
  • spiral are mostly motile; 50% to bacilli are motile; cocci are generally nonmotile
  • motility can be demonstrated by semisolid agar method or hanging drop technique
39
Q

semisolid agar method for motility

A
  • bacteria is tabbed into tube to semisolid medium to see its movement
40
Q

hanging drop technique for motility

A
  • slide with bacteria placed hanging over hole to observe motility
41
Q

colony morphology

A
  • bacterial colony contains millions of organisms
  • colony morphology varies form one species to another
  • includes size, colour, shape, elevation, and appearance of edge/margin of colony
  • can also include result of enzymatic activity on various media
  • not most definitive way of identification
42
Q

colony size determination

A
  • determined by organisms generation time

- start with single bacterial cell and follow replication

43
Q

atmospheric requirements

A
  • obligate aerobes - need O2
  • microaerophilic aerobes - need some O2
  • facultative anaerobes - can use O2 or not
  • aerotolerant anaerobes - can tolerations O2 but don’t need it
  • obligate anaerobes - can’t have O2
  • capnophilic organisms grow best in increased concentrations of CO2 (5-10%)
44
Q

relationship with O2 from most O2 to least O2

A

obligate aerobes (10-20%), microaerophiles (5%), facultative anaerobes, aerotoleratn anaerobes, obligate anaerobes (0%)

45
Q

determining O2 requirements

A
  • using thioglycollate broth (THIO)
  • bacteria placed in broth in tube with different concentrations of O2 in different areas of tube
  • determined by where the bacteria grows in tube
46
Q

nutritional requirements

A
  • all bacteria require some form of elements like carbon, hydrogen, O2, sulfur, phosphorus, and nitrogen for growth
  • some require special elements like calcium, iron, or zinc
  • nutritional needs are usually characteristic for that species and can be important clues to identity
47
Q

fastidious organisms

A
  • organisms with especially demanding nutritional requirements
  • fussy
48
Q

biochemical and metabolic activities

A
  • bacteria produce waste products and secretions as they grow (some enzymes)
  • pathogenic strains can be identifies by enzymes secreted
  • some bacteria in certain environments produce gases like CO2 and hydrogen sulfide
49
Q

determining biochemical and metabolic activities

A
  • bacteria is inoculated into various substances to determine whether they possess the enzymes necessary to break down those substances
50
Q

pathogenicity

A
  • many pathogens causes disease because they possess capsules, pili, or endotoxins or because they secrete exotoxins and exoenzymes that damage cells and tissues
  • ex: neisseria meningitides, salmonella type, shigella spp., vibrio cholera, yersina pestis, and treponema pallidum
51
Q

testing pathogenicity

A
  • done by injecting bacteria into mice or cell cultures
52
Q

genetic composition

A
  • molecular diagnostic procedures done to analyze organisms DNA or RNA
  • composition is unique to each species
  • DNA probes make is possible to identify an isolate without relying on phenotypic characteristics
  • the use of 16S rRNA sequencing can determine degree of relatedness between 2 bacteria
53
Q

unique bacteria

A
  • rickettsias, chlamydias, and mycoplasmas are bacteria but they don’t have all attributes of typical bacterial cells
54
Q

rickettsias and chlamydias

A
  • have gram - cell wall and are obligate intracellular pathogens so they must live in a host cell
  • rickettsias have leaky membrane
  • chlamydias are energy parasites meaning they need to use ATP molecules produced by host cell
55
Q

mycoplasmas

A
  • smallest of the cellular microbes
  • lack cell wall and assume different shapes (pleomorphic)
  • resistant to drugs like penicillin that attack cell wall
  • produce tiny fried egg looking colonies on artificial media
  • cause primary atypical pneumonia and genitourinary tract infections in humans
56
Q

photosynthetic bacteria

A
  • include purple, green, and cyano bacteria

- purple and green don’t produce O2, cyano do

57
Q

oxygenic photosynthesis

A
  • photosynthesis that produces O2
58
Q

aoxygenic photosynthesis

A
  • photosynthesis that does not produce O2
59
Q

archaea

A
  • means ancient discovered in 1977
  • prokaryotic
  • more closely related to eukaryotes than bacteria
  • vary in shape
  • some can live in extremes of acid, heat, or salt
  • have cell wall but no peptidoglycan

Microbiology (18 decks)

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