Microbiology Introduction
Brock chapter 1 + 13.1 – 13.4
Microorganisms are small organisms consisting of one cell or a cluster of
cells. They are diverse in form/function and inhabit every environment
supporting life. They live in microbial communities and are the oldest form
of life.
Microorganisms are a major fraction of Earth’s biomass; they surround
plants and animals and affect human life through symbiosis. In the three
domains of life (Bacteria, Archaea and Eukarya) only animals and plants in
the Eukarya group are not microorganisms; everything else exists from
microorganisms. Fungi are also microorganisms, but they can have
multicellular lifeforms (mushrooms).
Only a very small percentage of microorganisms are pathogens. Most
microbes are beneficial, or even essential.
The Cell
Bacteria are the dominant form of microbes. They are
unicellular. A cell is a living compartment that
interacts with the environment and other cells.
Elements of the microbial structure are:
- Cytoplasmic (cell) membrane; barrier inside vs.
outside.
- Cytoplasm; aqueous, macromolecules, small
organics, ions.
- DNA/Nucleoid; genetic material.
- Ribosomes; protein-synthesizing structures.
- Cell Wall: Present in all prokaryotes and many
eukaryotes; structural strength.
Prokaryotes are very simple compared to eukaryotes.
The main difference is that eukaryotes have membrane-bound organelles
with specific functions in their cells; they
have compartmentalized cell functions
(like mitochondria) and are thus more
organized than prokaryotes.
In eukaryotes, DNA is also membrane-
,bound in the nucleus. In prokaryotes the DNA is condensed but does not
have a membrane.
The genome of an organism is their full complement of genes. Herein
there is also a difference between prokaryotes and eukaryotes. Eukaryotic
DNA has linear chromosomes and is held within the nucleus. It is also
much larger (up to billions in base pairs).
Prokaryotic DNA is a single circular chromosome, which is much smaller
and compact (0,5 – 10 million base pairs), but there may also be plasmids
(extrachromosomal DNA), which has special properties (like antibiotic
resistance). These plasmids can be exchanged.
All cells have a metabolism; they can transfer nutrients or chemical
compounds from one form into the other, and by doing this they gain
energy. In order to achieve this metabolism, a few things are required;
Enzymes; these are protein catalysts.
Transcription; DNA needs to be converted to RNA.
Translation: RNA needs to be translated to a protein by the
ribosomes.
Metabolism is the sum of all chemical reactions in the cell, and can be
divided into:
o Catabolism: This is the transformation of molecules to produce
energy and building blocks. It is the ATP production.
o Anabolism: This is the synthesizing of macromolecules; the energy
gets used to produce biomass.
,If you look at the cell, it has genetic functions
and catalytic functions.
Genetic functions are the replication of DNA,
transcribed and translated into proteins. Proteins
in a cell can be many things; they can be part of
the cell structure or the enzymes that perform
the catalytic functions.
In Catabolism the energy is conserved and
then transferred into ATP (ADP + P), by using
enzymes.
There are different kind of energy sources that
can be used for catabolism; either chemicals
(chemotrophy) or light (phototrophy).
If an organism uses the oxidation of
organic compounds as an energy
source, they are called
chemoorganotrophs. If they use the
oxidation of inorganic compounds,
they are called chemolithotrophs –
this only happens in prokaryotes.
If an organism uses light as an energy
source, they are called phototrophs.
They can do this through oxygenic
photosynthesis, which produces O₂
(Cyanobacteria, algae), or anoxygenic
photosynthesis, which does not
produce O₂ (purple and green bacteria).
Once there is enough ATP, the production of biomass can start
(anabolism). Making this biomass can also be done in two different ways;
- Autotrophs; the carbon source used is CO₂ in the air. Most
phototrophs and chemolithotrophs are autotrophs. They are primary
producers.
- Heterotrophs; their carbon source are organic compounds; they
feed on the products of other organisms.
Morphology:
Major morphologies of
prokaryotic cells
The most dominant cell
types are coccus and
rods.
, Morphology typically does not predict physiology, ecology, phylogeny or
other properties of a prokaryotic cell. The selective forces involved in
morphology are optimalization for nutrient intake (small cells and high
surface-to-volume ratio cells), swimming motility (helical or spiral-shaped
cells) or gliding motility (filamentous bacteria).
Prokaryotes can be 0.2 to >700 µm in diameter; most cultured rod-shaped
bacteria are 0.5 – 4.0 µm wide and <15 µm long. Eukaryotic cells are 2 to
>600 µm in diameter.
There are advantages to being small; the smaller the organism, the larger
the surface-volume ratio. This means that the cytoplastic membrane is
larger compared to the volume of cytoplasm. In prokaryotes, the
cytoplasmic membrane is where the energy metabolism takes place; so
with more cytoplasmic membrane and less volume to take care of, the
organism is more efficient. This way, smaller cells can have higher activity.
There is a limit to this; there is still volume necessary to store cell
materials (DNA, ribosomes, proteins). Cellular organisms <0.15 µm in
diameter are unlikely.
Microbial Life
Bacteria
- Prokaryotes,
- Usually undifferentiated single cells 1-10 µm long but vary widely,
- >30 phylogenetic lineages, mostly diverse species with diverse
physiologies and ecological strategies.
Archaea
- Prokaryotes,
- Less morphological diversity than Bacteria,
- Mostly undifferentiated cells 1-10 µm long,
- <10 well-described phyla,
- Historically associated with extreme environment, but not all
extremophiles,
- Unclear whether also parasites or pathogens of plants and animals.
Eukarya
- Plants, animals, fungi, algae, protozoa,
- First were unicellular, may have appeared 2 billion years ago,
- At least 6 kingdoms,
- Very dramatically in size, shape and physiology.
Viruses
- Obligate parasites that only replicate within a host cell,
- Not cells and do not carry out metabolism – they take over other
metabolic systems to replicate.
- Have small genomes of double-stranded or single-stranded DNA or
RNA.
- Very diverse and classified based on structure, genome composition
and host specificity.
Brock chapter 1 + 13.1 – 13.4
Microorganisms are small organisms consisting of one cell or a cluster of
cells. They are diverse in form/function and inhabit every environment
supporting life. They live in microbial communities and are the oldest form
of life.
Microorganisms are a major fraction of Earth’s biomass; they surround
plants and animals and affect human life through symbiosis. In the three
domains of life (Bacteria, Archaea and Eukarya) only animals and plants in
the Eukarya group are not microorganisms; everything else exists from
microorganisms. Fungi are also microorganisms, but they can have
multicellular lifeforms (mushrooms).
Only a very small percentage of microorganisms are pathogens. Most
microbes are beneficial, or even essential.
The Cell
Bacteria are the dominant form of microbes. They are
unicellular. A cell is a living compartment that
interacts with the environment and other cells.
Elements of the microbial structure are:
- Cytoplasmic (cell) membrane; barrier inside vs.
outside.
- Cytoplasm; aqueous, macromolecules, small
organics, ions.
- DNA/Nucleoid; genetic material.
- Ribosomes; protein-synthesizing structures.
- Cell Wall: Present in all prokaryotes and many
eukaryotes; structural strength.
Prokaryotes are very simple compared to eukaryotes.
The main difference is that eukaryotes have membrane-bound organelles
with specific functions in their cells; they
have compartmentalized cell functions
(like mitochondria) and are thus more
organized than prokaryotes.
In eukaryotes, DNA is also membrane-
,bound in the nucleus. In prokaryotes the DNA is condensed but does not
have a membrane.
The genome of an organism is their full complement of genes. Herein
there is also a difference between prokaryotes and eukaryotes. Eukaryotic
DNA has linear chromosomes and is held within the nucleus. It is also
much larger (up to billions in base pairs).
Prokaryotic DNA is a single circular chromosome, which is much smaller
and compact (0,5 – 10 million base pairs), but there may also be plasmids
(extrachromosomal DNA), which has special properties (like antibiotic
resistance). These plasmids can be exchanged.
All cells have a metabolism; they can transfer nutrients or chemical
compounds from one form into the other, and by doing this they gain
energy. In order to achieve this metabolism, a few things are required;
Enzymes; these are protein catalysts.
Transcription; DNA needs to be converted to RNA.
Translation: RNA needs to be translated to a protein by the
ribosomes.
Metabolism is the sum of all chemical reactions in the cell, and can be
divided into:
o Catabolism: This is the transformation of molecules to produce
energy and building blocks. It is the ATP production.
o Anabolism: This is the synthesizing of macromolecules; the energy
gets used to produce biomass.
,If you look at the cell, it has genetic functions
and catalytic functions.
Genetic functions are the replication of DNA,
transcribed and translated into proteins. Proteins
in a cell can be many things; they can be part of
the cell structure or the enzymes that perform
the catalytic functions.
In Catabolism the energy is conserved and
then transferred into ATP (ADP + P), by using
enzymes.
There are different kind of energy sources that
can be used for catabolism; either chemicals
(chemotrophy) or light (phototrophy).
If an organism uses the oxidation of
organic compounds as an energy
source, they are called
chemoorganotrophs. If they use the
oxidation of inorganic compounds,
they are called chemolithotrophs –
this only happens in prokaryotes.
If an organism uses light as an energy
source, they are called phototrophs.
They can do this through oxygenic
photosynthesis, which produces O₂
(Cyanobacteria, algae), or anoxygenic
photosynthesis, which does not
produce O₂ (purple and green bacteria).
Once there is enough ATP, the production of biomass can start
(anabolism). Making this biomass can also be done in two different ways;
- Autotrophs; the carbon source used is CO₂ in the air. Most
phototrophs and chemolithotrophs are autotrophs. They are primary
producers.
- Heterotrophs; their carbon source are organic compounds; they
feed on the products of other organisms.
Morphology:
Major morphologies of
prokaryotic cells
The most dominant cell
types are coccus and
rods.
, Morphology typically does not predict physiology, ecology, phylogeny or
other properties of a prokaryotic cell. The selective forces involved in
morphology are optimalization for nutrient intake (small cells and high
surface-to-volume ratio cells), swimming motility (helical or spiral-shaped
cells) or gliding motility (filamentous bacteria).
Prokaryotes can be 0.2 to >700 µm in diameter; most cultured rod-shaped
bacteria are 0.5 – 4.0 µm wide and <15 µm long. Eukaryotic cells are 2 to
>600 µm in diameter.
There are advantages to being small; the smaller the organism, the larger
the surface-volume ratio. This means that the cytoplastic membrane is
larger compared to the volume of cytoplasm. In prokaryotes, the
cytoplasmic membrane is where the energy metabolism takes place; so
with more cytoplasmic membrane and less volume to take care of, the
organism is more efficient. This way, smaller cells can have higher activity.
There is a limit to this; there is still volume necessary to store cell
materials (DNA, ribosomes, proteins). Cellular organisms <0.15 µm in
diameter are unlikely.
Microbial Life
Bacteria
- Prokaryotes,
- Usually undifferentiated single cells 1-10 µm long but vary widely,
- >30 phylogenetic lineages, mostly diverse species with diverse
physiologies and ecological strategies.
Archaea
- Prokaryotes,
- Less morphological diversity than Bacteria,
- Mostly undifferentiated cells 1-10 µm long,
- <10 well-described phyla,
- Historically associated with extreme environment, but not all
extremophiles,
- Unclear whether also parasites or pathogens of plants and animals.
Eukarya
- Plants, animals, fungi, algae, protozoa,
- First were unicellular, may have appeared 2 billion years ago,
- At least 6 kingdoms,
- Very dramatically in size, shape and physiology.
Viruses
- Obligate parasites that only replicate within a host cell,
- Not cells and do not carry out metabolism – they take over other
metabolic systems to replicate.
- Have small genomes of double-stranded or single-stranded DNA or
RNA.
- Very diverse and classified based on structure, genome composition
and host specificity.
