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Infectious Agents > Bacterial Classification and Morphology > Flashcards

Bacterial Classification and Morphology Flashcards

1
Q

Eukaryotic

A

All organisms, microscopic and macroscopic, except bacteria and blue green algae

  • true nucleus
  • histones
  • diploid
  • sexual and asexual
  • no cell wall
  • 80S
  • mitochondrial membrane for electron transport
  • sterols present in cytoplasmic membrane
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2
Q

Prokaryotic

A

Simpler cell types

  • 0.3-0.2 um in diameter
  • supercoiling
  • haploid
  • asexual
  • cell wall with murein
  • 70S
  • cytoplasmic membrane for electron transport
  • sterols absent
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3
Q

Why are differences between prokaryotes and eukaryotes important?

A

Reveal their different strategies for survival
- eukaryotes: adaptation and specialization
- prokaryotes: divide and conquer
Allow antimicrobials targeting unique bacterial structures

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4
Q

Fungi

A

Eukaryotic, multicellular, but similar to bacteria in complexity without differentiation into specialized tissues and organs
- all cells remain simple and similar, despite remaining permanently attached in a large organism

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5
Q

Bacterial nomenclature

A

Classical binomial Linnean system

  • species and genus name
  • number of species may be included in a genus
  • first word is the genus name and is always capitalized
  • second word is species name and is not capitalized
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6
Q

Taxonomy

A

System of classification that groups bacteria with similar properties and is used to distinguish those that are different

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7
Q

Species

A

Basic taxonomic unit

  • bacterial species are not equivalent to eukaryotic species, since bacteria are haploid and produce asexually!
  • prokaryotes: species is defined as a group of strains with unique phenotypic properties and exhibit more than 70% whole genome DNA-DNA hybridizations among strains
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8
Q

Bacterial strain

A

Consists of descendants from a single isolate in pure culture (a clonal population)
- type strain: originally described isolate of the species

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9
Q

Is sexual reproduction used as a criterion for classification of bacteria?

A

NO

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10
Q

Polyphasic taxonomy

A

Uses combined systems of DNA sequence and phenotypic characteristics

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11
Q

DNA sequence

A
  • DNA-DNA hybridization (70%)
  • 16S rRNA sequence (97%)
  • Multilocus sequence typing
  • Average nucleotide identity (95%)
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12
Q

Phenotypic characteristics

A
  • chemical analyses of structural components
  • serologic reactivity
  • enzyme profile
  • nutritional requirements
  • morphology
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13
Q

Keys

A

Used in clinical laboratory to classify bacteria into convenient groups of clinical interest

  • uses biochemical reactions, sugar fermentations, etc
  • useful in identifying bacteria quickly with little materials
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14
Q

Tree of Life

A
  • archebacteria (archea): extremophilic environmental bacteria
  • eubacteria (true bacteria)
  • eukaryota
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15
Q

Eubacteria are phenotypically divided based on

A
  • cell envelope type: gram positive or negative
  • cell morphology: cocci, bacilli, spirilla
  • motility
  • multiplication: binary fission, budding, etc
  • cell association
  • dependence on living cells for growth
  • atmospheric requirements
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16
Q

Cell association

A
  • long chains: streptococci
  • clusters: staphylococci
  • cubical packets of 4 or 8: tetrads or sarcinae
  • pairs: diploccoci or diplobacilli (are always end to end, not on top of each other)
17
Q

Obligate requirements

A

Require oxygen, oxidize only, respire

- stick to the top layer of a test tube

18
Q

Obligate anaerobes

A

Killed by oxygen, ferment only or use anaerobic respiration

  • still respire but use an electron carrier that is not oxygen
  • stick to bottom of tube
19
Q

Faculative anaerobes

A

Could oxidize or ferment

  • prefer to grow aerobically
  • mostly stick to the top, but distribute throughout the tube
20
Q

Microaerophilic

A

Require reduced oxygen

- stick a little below the top

21
Q

Aerotolerant

A

Do not require oxygen, not killed by oxygen, ferment only

- are evenly distributed throughout the tube

22
Q

Capnophilic

A

Require increased carbon dioxide

23
Q

Microscopy

A

Most common units of measurement are the micron or micrometer (10^6 m) or nanometer (10^9 m)

24
Q

Light microscope

A

Bright field, staining required

  • max resolving power of 0.2 um under optimal conditions
  • 1000 X magnification commonly used with oil immersion
25
Q

Darkfield and phase contrast microscopy

A

Used to observe unstained, living cells and movement

- resolution to 0.1 um

26
Q

Fluorescent microscopy

A

Used in research and diagnostic labs

  • immunofluorescence
  • resolution to 0.1 um
27
Q

Electron microscopy

A

Scanning and transmission

  • internal or surface detail available
  • resolution to 0.0003 um (0.3 nm)
28
Q

Preparation for staining

A
  • drop of liquid containing bacteria is placed on a glass slide and allowed to dry
  • dried film is fixed onto slide using a chemical fixative or heat (passing slide thru a flame coagulates cell surface protein and sticks the bacteria to the slide)
  • stains are used that stain specific cell components (cytoplasm, flagella, cell wall, membranes, granules, nuclei, and spores)
29
Q

Positive stains

A

Have an affinity for one or more cell components

  • simplest stains are colored cationic salts (basic dyes) that combine with phosphate groups (negatively charged) of nucleic acids
  • ex: methylene blue
30
Q

Negative stains

A

Acidic dyes that do not penetrate cells

  • background contrasts with cells
  • ex: India ink
31
Q

Differential stains

A

Used to separate bacteria into groups based on their ability to take up and retain certain dyes
- ex: Gram stain, acid fast stain

32
Q

Gram stain

A

Divides all eubacteria into 2 groups
- primary stain: Gentain or crystal violet, all bacteria take it up
- mordant: Gram’s iodine and decreases crystal violet solubility
- decolorizer: ethyl alcohol removes purple dye from some bacteria, but not others
- counterstain: Safranin
= bacteria that retain purple dye and resist decolorization are Gram positive, bacteria that were decolorized take up counterstain and are Gram negative

33
Q

What is Gram’s stain used to determine?

A
  • GR: gram’s reaction
  • A: arrangement (spatial orientation resulting as a consequence of growth
  • M: morphology (form of cells)
34
Q

How to determine gram’s reaction without staining

A

Add a bacterial colony to a drop of 10% KOH and stir

  • if solution is soapy, stringy, slimy, or viscous then bacteria are gram negative
  • reaction is caused by saponification of phospholipids in the outer membrane
35
Q

Unstained

A

Both gram-positive and gram-negative organisms are clear

36
Q

Crystal violet

A

Both gram-positive and gram-negative organisms are violet

37
Q

Iodine

A

Both gram-positive and gram-negative are violet

38
Q

Decolorization

A
  • gram positive organisms are violet

- gram negative organisms are clear

39
Q

Safranin

A
  • gram positive organisms are purple

- gram negative organisms are red

Infectious Agents (44 decks)

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