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Microbiology > Acellular pathogens > Flashcards

Acellular pathogens Flashcards

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Biology 101 flashcards
1
Q

Obligatory intracellular parasite

A

Require living host cells to multiply

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2
Q

Describe the basic characteristics of viruses

A

Obligatory intracellular parasite, Contain DNA or RNA, contain protein coat, No ribosomes, no ATP generating mechanism

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3
Q

What is meant by host range?

A

Host range is the spectrum of host cells a virus can infect, most viruses infect only specific types of cells in one host (determined by specific host attachment sites and cellular factors)

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4
Q

What is a bacteriophage?

A

Virus that infects bacteria, range from 20nm to 1000 nm in length

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5
Q

Define and describe the components of a virion

A

A virion is a complete, fully developed viral particle, nucleic acid (DNA or RNA), can be single or double stranded; linear or circular, Capsid (protein coat made of capsomeres/subunits), Envelope (lipid, protein, and carbohydrate coating on some viruses), spikes (projections from outer surface for attachment or gaining entry into a host)

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6
Q

Helical viruses

A

Hollow, cyclindrical capsid

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7
Q

Polyhedral viruses

A

Many-sided, geometric in shape

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8
Q

Enveloped viruses

A

Has outer coating lipid, protein, or carbohydrate

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9
Q

Complex viruses

A

Complicated structures (bacteriphages)

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10
Q

Nonenveloped viruses

A

naked viruses

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11
Q

Suffix -virus

A

Genus names end in -virus

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12
Q

Suffix -viridae

A

Family name ends in -viridae

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13
Q

Suffix -ales

A

Order name ends in -ales

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14
Q

Viral species

A

A group of viruses sharing the same genetic information and ecological niche (host)

  • Descriptive common names are used for species
  • Subspecies are designated by a number
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15
Q

What do viruses need to be grown in labs?

A

Viruses must be grown in living cells

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16
Q

How are bacteriophages grown in a lab?

A

Bacteriophages are grown in bacteria, bacteriophages form plaques, which are clearings on a lawn of bacteria on the surface of agar-each plaque corresponds to a single virus; can be expressed as plaque-forming units (PFU)

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17
Q

Growing animal viruses in the lab

A
  • In living animals
  • In embryonated eggs (virus injected into the egg/ viral growth is signaled by changes or death of the embryo)
  • In cell cultures (Tissues derived from living organisms)- Tissues are treated with enzymes to separate cells, virally infected cells detected via their deterioration, known as cytopathic effect (CPE), continuous cell lines are used-Henrietta Lacks
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18
Q

Describe the one-step growth curve for viral multiplication

A
  1. Inoculum
  2. Eclipse period- virus invaded host cell
  3. Burst- virions released from host cell *acute infection
  4. Viral titer-measure of how many viruses in filtrate
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19
Q

Describe the lytic cycle for phages

A
  1. Attachment – Phage attaches by the tail fibers to the host cell
  2. Penetration – the phage injects its DNA into the host cell by penetrating through the cell membrane
  3. Biosynthesis – the phage DNA replicates inside the cell, synthesizing new phage DNA and proteins
  4. Maturation – the replicated material assembles into fully formed viral phages (each made up of a head, a tail and tail fibers)
  5. Lysis – the newly formed phages are released from the infected cell
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20
Q

Describe the lysogenic cycle for phages

A

In contrast to the lytic cycle, phages infecting bacteria via the lysogenic cycle do not immediately kill their host cell. Instead, they combine their genome with the host genome, allowing the bacteria to replicate the phage DNA along with the bacterial genome. The incorporated copy of the phage genome is called the prophage.

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21
Q

Generalized transduction

A

Random bacterial genes incorporated into capsid; can be transferred to another bacteria when infected; lytic or lysogenic phages

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22
Q

Specialized trasnduction

A

Specific bacterial genes transferred to another bacterium via a phage; When prophage excises, extra host DNA is taken; changes genetic properties of the bacteria

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23
Q

Multiplication of animal viruses

A
  1. Attachment- viruses attach to cell membrane
  2. Entry- by receptor mediated endocytosis of fusion
  3. Uncoating- by viral or host enzymes
  4. Biosynthesis- production of nucleic acids and proteins
  5. Maturation- nucleic acid and capsid proteins assemble
  6. Release- by budding (enveloped viruses) or rupture
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24
Q

The biosynthesis of DNA viruses

A

DNA viruses replicate their DNA in the nucleus of the host using viral enzymes; Synthesize capsid in the cytoplasm using host cell enzymes.

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25
Q

Adenoviridae (DNA virus)

A

Double stranded DNA, non enveloped; respiratory infections in humans, tumors in animals

26
Q

Double stranded DNA, non enveloped; respiratory infections in humans, tumors in animals

A

Adenoviridae

27
Q

Poxviridae (DNA virus)

A

Double stranded DNA, enveloped; cause skin lesions, vaccinia and smallpox viruses (orthopox virus)

28
Q

Double stranded DNA, enveloped; cause skin lesions, vaccinia and smallpox viruses (orthopox virus)

A

Poxviridae

29
Q

Herpesviridae (DNA virus)

A

Double stranded DNA, enveloped; HHV1-8 (simplex virus, cold sores, varicellovirus, chickenpox, lymphocryptovirus, mononucleosis, cytomegalovirus, roseolovirus, rhadinovirus, and kaposi’s sarcoma)

30
Q

Double stranded DNA, enveloped; HHV1-8 (simplex virus, cold sores, varicellovirus, chickenpox, lymphocryptovirus, mononucleosis, cytomegalovirus, roseolovirus, rhadinovirus, and kaposi’s sarcoma)

A

Herpesviridae

31
Q

Papoviridae (DNA virus)

A

Double stranded DNA, nonenveloped; papillomavirus (causes warts, can transform cells and cause cancer)

32
Q

Double stranded DNA, nonenveloped; papillomavirus (causes warts, can transform cells and cause cancer)

A

Papoviridae

33
Q

Hepadnaviridae (DNA virus)

A

Double stranded DNA, enveloped; Hepatitis B virus, use reverse transcriptase to make DNA from RNA

34
Q

Double stranded DNA, enveloped; Hepatitis B virus, use reverse transcriptase to make DNA from RNA

A

Hepadnaviridae

35
Q

Biosynthesis of RNA viruses

A

Virus multiplies in the host cell’s cytoplasm using RNA-dependent RNA polymerase (replicase)

36
Q

ssRNA + sense strand

A

Viral RNA serves as mRNA for protein synthesis

37
Q

ssRNA - antisense strand

A

Viral RNA is transcribed to a + strand to serve as mRNA for protein synthesis

38
Q

dsRNA

A

Double stranded RNA both + and -

39
Q

+ Picornaviridae (RNA virus)

A

Single stranded RNA, + strand, non enveloped; enterovirus, rhinovirus, hepatitis A virus

40
Q

Single stranded RNA, + strand, non enveloped; enterovirus, rhinovirus, hepatitis A virus

A

Picornaviridae

41
Q

+ Togaviridae (RNA virus)

A

Single stranded RNA, + strand, enveloped; alphavirus (transmitted by arthropods), rubivirus (rubella)

42
Q

Single stranded RNA, + strand, enveloped; alphavirus (transmitted by arthropods), rubivirus (rubella)

A

Togaviridae

43
Q
  • Rhabdoviridae (RNA virus)
A

Single stranded RNA, - strand, Lyssavirus (rabies), numerous animal diseases

44
Q

Single stranded RNA, - strand, Lyssavirus (rabies), numerous animal diseases

A

Rhabdoviridae

45
Q

Reoviridae (RNA virus)

A

Double stranded RNA, nonenveloped, reovirus, rotavirus (mild respiratory inf. and gastroenteritis)

46
Q

Biosynthesis of RNA viruses that use DNA

A

Single stranded RNA produce DNA- use reverse transcriptase to produce DNA from the viral genome/ viral DNA integrates into the host chromosome as a provirus

47
Q

Retroviridae (RNA virus that uses DNA)

A

Lentivirus (HIV), oncoviruses

48
Q

Viruses and cancer

A

May develop long after viral infection; Cancers caused by viruses are not contagious

49
Q

Sarcoma

A

Cancer of connective tissue

50
Q

Adenocarcinomas

A

Cancers of glandular epithelial tissue

51
Q

Oncogenes

A

Transform normal cells into cancerous cells

52
Q

Oncogenic viruses

A

Become integrated into the host cell’s DNA and induce tumors

53
Q

Tumor specific transplant antigen and T antigen

A

A transformed cell harbors a tumor specific transplant antigen (TSTA) on the surface and a T antigen in the nucleus

54
Q

DNA oncogenic viruses

A 
Adenoviridae
Herpesviridae
Poxviridae
Papoviridae
Hepadnaviridae
55
Q

RNA oncogenic viruses

A

Retroviridae- Viral RNA is transcribed to DNA (reverse transcriptase) which can integrate into host DNA; HTLV 1 and 2 cause adult T cell leukemia and lymphoma

56
Q

Latent virus

A

Remains in asymptomatic host cell for a long period of time- may reactivate due to changes in immunity (cold sores/shingles)

57
Q

Persistent viral infection

A

Occurs gradually over a long period; generally fatal, subacute sclerosing panencephalitis (measles virus)

58
Q

What is a prion?

A

Proteinaceous infectious particles; inherited and transmissible by ingestion, transplant, and surgical instruments…spongiform encephalopathies (mad cow disease, crentzfeldt jakob disease, gertsmann-straussler-scheinker syndrome, fatal familial insomnia, sheep scrapie)

59
Q

PrPc

A

Normal cellular prion protein, on cell surface

60
Q

PrPsc

A

Scrapie protein; accumulates in brain cells, forming plaques

61
Q

Plant viruses

A

Enter through wounds or via insects; plant cells are generally protected from disease by an impermeable cell wall

62
Q

Viroids

A

Short pieces of naked RNA; cause potato spindle tuber disease

Microbiology (7 decks)

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