MICROBIAL DIVERSITY
Lecture One: Introduction and Classification
Vocabulary Microorganisms - An organism that is only seen under a
microscope.
Microbes - a microorganism.
Horizontal Gene Transfer - the movement of genetic information
between organisms, including the spread of antibiotic resistance
genes among bacteria fueling pathogen evolution.
Heterotroph - an organism deriving its nutritional requirements
from complex organic substances.
Peptidoglycan - a substance that forms the cell walls of bacteria,
consisting of glycosaminoglycan chains interlinked with short
peptides.
Why Do Microbes Matter? ● Microbes can survive in environments where no other life
forms can survive.
● They can survive with or without oxygen.
● They are nitrogen-fixing organisms.
● They are less complex than animals or plants - basic
cells.
● Microbes are capable of Horizontal Gene Transfer.
● Rapid growth rates - efficient for research.
● Diverse metabolic pathways.
Importance of Prokaryotes are largely responsible for creating atmosphere and
Microorganisms soil billions of years ago. Example: cyanobacteria produced
oxygen through photosynthesis.
Microorganisms promote life via the cycling of chemical
components such as:
Nitrogen fixation - reduction of N2 to (ammonia) NH3 by
prokaryotes which is the only way nitrogen sources are
replenished.
Organic compounds produced from CO2 - photosynthetic
plants, algae and prokaryotes are involved in this process and
serve as building blocks for heterotrophic organisms.
Decomposition - prokaryotes and fungi are responsible for this.
Carl Woese In 1977, Carl Woese proposed 3 Domains of life, based on the
sequencing of ribosomal RNA (16S or 18S rRNA).
A three-domain system consists of Bacteria, Archaea
(Prokaryotes) and Eukarya (Eukaryotes).
, In Woese’s revised Tree of Life, it is shown that Archaea are
more related to Eukarya than Bacteria.
Image:
https://study.com/academy/lesson/archaea-bacteria-similarities-differences.html
Classification Microbes are classified based on similarities
● Phenotypic (Morphology)
● Genotypic (DNA homology)
Image:
https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/12-ultrastructure-of-
cells/prokaryotic-versus-eukaryot.html
,Taxonomy Hierarchy
Image: Source Unknown
NB: Learn species names
Carl Linnaeus created the binomial nomenclature system.
Species are assigned a Latinized two-part name. Species can
have multiple strains.
Extra Note: Difference Similarities
Between Bacteria and ● Can be pathogenic.
Viruses ● Microbes (All very small).
Viruses
● Smaller than bacteria.
● Not living.
● Need a host to reproduce.
● Short course of illness (days).
● Immune system can cure itself.
Bacteria
● Larger than viruses.
● Alive.
● “Good bacteria” exists.
● No host cell needed and can reproduce alone.
● Long course of illness (weeks).
● Antibiotics are needed.
Domain: Bacteria ● True bacteria (Eubacteria)
● These are the most abundant organisms on earth.
● Characteristics
- No true nucleus, no introns in DNA (Introns:
sections of mRNA that don’t code for a protein)
- Very small, unicellular organisms
- No cell organelles
- Cell walls contain peptidoglycan (Gram +/- cells)
- Reproduce by binary fission (No sexual
, reproduction)
Image: https://www.biologyonline.com/dictionary/bacteria
Domain: Archaea Similar features to bacteria but more closely related to
eukaryotes.
● No peptidoglycan in cell walls
● Different lipid composition of membranes to bacteria
● Gene translation mechanism is similar to eukaryotes
● Intron may be present in DNA (similar to eukaryotes)
Archaea inhabit extreme habitats, such as areas with high levels
of salt, high pressures, extreme pH levels and high temperatures.
Examples are methanogens, thermophiles and halophiles.
Image:
https://www.knowswhy.com/difference-between-archaebacteria-and-eubacteria/
Domain: Eukarya This domain consists of fungi, protists, plants and animals.
● True nucleus with nuclear membrane
● Compartmentalization - in eukaryotic cells, organelles live
and “work” in separate areas within the cell as to perform
their specific functions more efficiently.
Lecture One: Introduction and Classification
Vocabulary Microorganisms - An organism that is only seen under a
microscope.
Microbes - a microorganism.
Horizontal Gene Transfer - the movement of genetic information
between organisms, including the spread of antibiotic resistance
genes among bacteria fueling pathogen evolution.
Heterotroph - an organism deriving its nutritional requirements
from complex organic substances.
Peptidoglycan - a substance that forms the cell walls of bacteria,
consisting of glycosaminoglycan chains interlinked with short
peptides.
Why Do Microbes Matter? ● Microbes can survive in environments where no other life
forms can survive.
● They can survive with or without oxygen.
● They are nitrogen-fixing organisms.
● They are less complex than animals or plants - basic
cells.
● Microbes are capable of Horizontal Gene Transfer.
● Rapid growth rates - efficient for research.
● Diverse metabolic pathways.
Importance of Prokaryotes are largely responsible for creating atmosphere and
Microorganisms soil billions of years ago. Example: cyanobacteria produced
oxygen through photosynthesis.
Microorganisms promote life via the cycling of chemical
components such as:
Nitrogen fixation - reduction of N2 to (ammonia) NH3 by
prokaryotes which is the only way nitrogen sources are
replenished.
Organic compounds produced from CO2 - photosynthetic
plants, algae and prokaryotes are involved in this process and
serve as building blocks for heterotrophic organisms.
Decomposition - prokaryotes and fungi are responsible for this.
Carl Woese In 1977, Carl Woese proposed 3 Domains of life, based on the
sequencing of ribosomal RNA (16S or 18S rRNA).
A three-domain system consists of Bacteria, Archaea
(Prokaryotes) and Eukarya (Eukaryotes).
, In Woese’s revised Tree of Life, it is shown that Archaea are
more related to Eukarya than Bacteria.
Image:
https://study.com/academy/lesson/archaea-bacteria-similarities-differences.html
Classification Microbes are classified based on similarities
● Phenotypic (Morphology)
● Genotypic (DNA homology)
Image:
https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/12-ultrastructure-of-
cells/prokaryotic-versus-eukaryot.html
,Taxonomy Hierarchy
Image: Source Unknown
NB: Learn species names
Carl Linnaeus created the binomial nomenclature system.
Species are assigned a Latinized two-part name. Species can
have multiple strains.
Extra Note: Difference Similarities
Between Bacteria and ● Can be pathogenic.
Viruses ● Microbes (All very small).
Viruses
● Smaller than bacteria.
● Not living.
● Need a host to reproduce.
● Short course of illness (days).
● Immune system can cure itself.
Bacteria
● Larger than viruses.
● Alive.
● “Good bacteria” exists.
● No host cell needed and can reproduce alone.
● Long course of illness (weeks).
● Antibiotics are needed.
Domain: Bacteria ● True bacteria (Eubacteria)
● These are the most abundant organisms on earth.
● Characteristics
- No true nucleus, no introns in DNA (Introns:
sections of mRNA that don’t code for a protein)
- Very small, unicellular organisms
- No cell organelles
- Cell walls contain peptidoglycan (Gram +/- cells)
- Reproduce by binary fission (No sexual
, reproduction)
Image: https://www.biologyonline.com/dictionary/bacteria
Domain: Archaea Similar features to bacteria but more closely related to
eukaryotes.
● No peptidoglycan in cell walls
● Different lipid composition of membranes to bacteria
● Gene translation mechanism is similar to eukaryotes
● Intron may be present in DNA (similar to eukaryotes)
Archaea inhabit extreme habitats, such as areas with high levels
of salt, high pressures, extreme pH levels and high temperatures.
Examples are methanogens, thermophiles and halophiles.
Image:
https://www.knowswhy.com/difference-between-archaebacteria-and-eubacteria/
Domain: Eukarya This domain consists of fungi, protists, plants and animals.
● True nucleus with nuclear membrane
● Compartmentalization - in eukaryotic cells, organelles live
and “work” in separate areas within the cell as to perform
their specific functions more efficiently.
