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LSCI 230: Microbiology > Taxonomy > Flashcards

Taxonomy Flashcards

1
Q

Nomenclature

A
  • Binomial system used to name all cellular organisms
  • Names are descriptive and derived from Latin and Greek
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2
Q

What are stromatolites

A

Microbial mats consisting of layers of filamentous prokaryotes, sediments and extracellular matrix

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3
Q

Origin or cellular life: Theories

A
  • Surface origin hypothesis
  • Subsurface origin hypothesis
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4
Q

Surface origin hypothesis

A
  • The first membrane-enclosed, self-replicating cells arose out of primordial soup rich in organic and inorganic compounds in ponds on Earth’s surface
  • Dramatic temperature fluctuations (day/night) and mixing from meteor impacts, dust clouds, and storms argue against this hypothesis
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5
Q

Subsurface origin hypothesis

A
  • Life originated in hydrothermal springs on the ocean floor
  • Conditions would have been more stable
  • Steady and abundant supply of energy (e.g., H 2 and H 2 S) was likely available at these sites
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6
Q

Origin of cellular life: Emergence steps

A
  1. Prebiotic chemsitry:
    * Biological building blocks
  2. Precellular life:
    * RNA world
    * Protein synthesis
    * DNA
  3. Early cellular life:
    * Lipid bilayers
  4. LUCA
  5. Diversification of Bacteria & Archaea
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7
Q

RNA world theory

A

First self-replicating system may have been RNA
* RNA can bind small molecules
* RNA has catalytic activity
* RNA can be copied like DNA

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8
Q

LUCA

A

Population of early cells from which
cellular life may have diverged into ancestors of modern-day Bacteria and Archaea

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9
Q

Origin of Life: Conditions

A

Early Earth was anoxic and much hotter than present day

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10
Q

2 methods of classification

A
  • Phenetics: Overall similarity
  • Phylogenetics: Evolutionary relationships
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11
Q

Phenetics: Rules

A
  • All characteristics should be considered of equal importance
  • Classification should be base on as many features as possible.
  • Organisms should be grouped based on overall similarity
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12
Q

Similarity/Jaccard coefficient

A

S = # shared/total
Sj = # shared/(total - negative shared)

  • 0.85 = species similarity
  • 0.65 = genus similarity
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13
Q

Phenon

A

Group of organisms that have characters in common

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14
Q

Phylogenetics

A
  • Fossil record
  • Ribosomal RNA sequencing
  • Multi-locus sequence typing
  • Whole genome sequencing
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15
Q

Ribosomal RNA sequencing: Steps

A
  • Amplification of the gene encoding SSU rRNA
  • Sequencing of the amplified gene
  • Analysis of sequence in reference to other sequences
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16
Q

SSU rRNA

A
  • Contains conserved & variable region
  • Evolutionary relationship
    between 2 organisms = # of mutations in each region.
  • Few differences: closely related
  • Many differences: loosely related
17
Q

Multi-locus sequence typing (MLST)

A
  • Method in which several different “housekeeping genes” from a species are sequenced and aligned to the respective sequences of other individuals of the same species
  • Can distinguish between very closely related strains
18
Q

Phylogenetic tree

A

Graphic illustration of the relationships among sequences
* Branch length = the number of changes that have occurred along that branch
* Branches = the order of descent & ancestry of the nodes
* Nodes: putative common ancestor

19
Q

Polyphasic approach to taxonomy

A
  1. Phylogenetic analysis (SSU rRNA)
  2. Phentypic analysis (motility, capsule, virulence…)
  3. Genotypic analysis (presence/absence of specific genes)
20
Q

Identification

A
  • Comparison of its properties with those of organisms that have already been classified and named
  • Dichotomous key
  • Serotyping
21
Q

Serotyping

A

Based on the binding of specific antibody to surface structure:
* LPS: O serotypes
* Capsule: K serotypes
* Flagella: H serotypes
* H1N1, Hemagglutinin 1, Neuraminidase 1

Positive reaction: agglutination

22
Q

Ancient Vs Modern stromatolites

A
  • Ancient stromatolites: Anoxygenic phototrophic filamentous bacteria
  • Modern stromatolites: Oxygenic phototrophic cyanobacteri

LSCI 230: Microbiology (14 decks)

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