….the branch of science concerned with
classification, especially of organisms; systematics. A
…. the evolutionary development and
diversification of a species or group of organisms
Microorganisms can generally be grouped into three
categories: wic are?
rods, cocci, and spirals
…….. are small and have simple shapes, so it is difficult to classify them on the basis of morphology. Exceptions are the.......
Bacteria and Archaea
cyanobacteria and actinomycetes
Evolutionary history of a group of organisms
Inferred indirectly from nucleotide sequence data
Molecular clocks (chronometers)
-Certain genes are measures of evolutionary change
Major assumptions: nucleotide changes occur at a
constant rate, are generally neutral, and are random
-Needs to be calibrated with fossils record
..... have many easily distinguished features eg body plans and developmental processes, that can be used to describe hierarchies of relatedness
gram positive have no wall while gram -ve have a ........
unlike ....., microbes are morphologically simple and shape may have little to do with phylogeny
plants and animals wit complex morphology
bergey' manual for classification provided a useful way to classify ana unknown microbe based on structural,biochemical and phusiological characteristics. wat is the con for this system?
it is not based on evolutionary framework eg the gram negative bacteria are not a phylogenetically coherent group
The universal phylogenetic tree is based on..........
SSU rRNA genes
the 16s/18s rRna is the .................
regions in wic nucleotide sequence is conserved in all cells.
central component in protein synthesis
why use the 16s/18s rRna as a molecular chronometer?
universally distributed and conserved structure
coded for in organeller, nuclear, and prokaryotic genomes
slow-and fast evolving portions: hr and minute hands
statistically sufficient number of nucleotides
ancient and essential function
no lateral gene transfer lgt
The science of identification, classification,
The study of the diversity of organisms and
Links phylogeny with taxonomy
The polyphasic approach to taxonomy uses
1. Phenotypic analysis
2. Genotypic analysis
3. Phylogenetic analysis
Phenotypic analysis examines the
morphological, metabolic, physiological,
and chemical characters of the cell
E.g. fatty acid analysis
No universally accepted concept of species for
Current definition of prokaryotic species
Collection of strains sharing a high degree of
similarity in several independent traits
Most important traits include 70% or greater
DNA DNA hybridization and 97% or greater
16S rRNA gene sequence identity
16S rRNA gene sequences are useful in
taxonomy; serve as “gold standard” for the
identification and description of new species
Proposed that a bacterium should be considered a
new species if its 16S rRNA gene sequence differs
by more than 3% from any named strain, and a new
genus if it differs by more than 5%
the universal phylogenetic tree is based on.....
ssu rRna genes
incorporated into the ancestor to the
eukaryotic cell: aerobic respiration:
incorporated into the eukaryotic cell:
Increased the metabolic diversity
species are of the same species if they share > 97% 16s rRna seq homology and > 70% genomic hybridization