Protocells may be a reasonable model for the evolution of cells: because
- They are organized systems of parts with substances interacting, in
some cases catalytically. - They have an interior that is distinct from the exterior environment.
- They can self-replicate.
The earliest cells?
This fossil from Western Australia is 3.5 billion years old.
Its form is similar to that of modern filamentous
cyanobacteria (inset).
Bacteria and archaea represents the first split in
the tree of life
The earliest split in
the tree of life
resulted in two
major groups:
Bacteria and
Archaea.
* The third domain,
Eukarya, which
includes all plants,
animals, and fungi,
arose through
phylogenetic
contributions from
both bacteria (via
endosymbiosis)
and archaea.
What are bacteria anyway?
Bacteria are prokaryotes:
unicellular organisms that lack nuclei and other membrane-
enclosed organelles.
First visualization of bacteria
Van Leeuwenhoek is known for as Father of Microbiology, was
one of the first to observe bacteria under microscope.
How can we classify the
bacteria?
Based on the structure of the cell wall
Based on their shape
Gram Stain meaning
The Gram stain method separates bacteria into two groups.
Differences are due to the structure of the cell wall.
Gram-positive
bacteria retain the violet dye.
Gram-positive bacteria have a thick layer of peptidoglycan outside the
cell membrane.
Gram-positive bacteria have a thick peptidoglycan cell wall that retains
the violet dye and appears deep blue or purple.
Gram-negative
bacteria retain the red dye.
Gram-negative bacteria have a thin layer of peptidoglycan in the
periplasmic space between the cell membrane and another outer
membrane.
Gram-negative bacteria have a thin peptidoglycan layer that does not
retain the violet dye, but picks up the counterstain and appears pink to
red.
Bacterial cell
shapes:
Sphere—coccus,
occur singly or in
plates, blocks, or
clusters
Rod—bacillus
Spiral—spirillum
Bacilli and spirilli
shapes may form
chains or clusters.
Bacteria Vibrio
The milky blue area near the Horn of Africa
represents a large, bioluminescent bloom
of bacteria, as seen from space.
Bacteria in Yellow Stone
Cyanobacteria Synechococcus
*pH: 7–9
*Temperature: 52–74°C (126–165°F)
*Location: Mammoth Hot Springs, Upper,
Midway, and Lower geyser basins
Koch’s postulates
Microorganism is always found in persons
with the disease.
* It can be taken from the host and grown in
pure culture.
* A sample of the culture causes the disease
in a new host.
* The new host also yields a pure culture.
Bacteria in Yellow Stone
Cyanobacteria Calothrix
*pH: 6–9
*Temperature: 30–45°C (86–113°F)
*Location: Mammoth Hot Springs, Upper,
Midway, and Lower geyser basins
Bacteria can be
pathogenic and
non-pathogenic
A small minority of bacteria are
pathogens
Microbiomes
Many prokaryotes live in and on other organisms.
* Human health depends in part on the health of our microbiomes,
bacterial communities that live in and on our bodies.
* Every surface of your body is covered with diverse communities of
bacteria.
Legionella pneumophila: History
The bacterium got its name
after 1976 during an American
Legion convention in
Philadelphia
The generic term “legionellosis”
was afterwards used to
describe bacterial infections
that range from a mild illness
(Pontiac fever) to a severe and
potentially lethal pneumonia
(Legionnaires disease)
Legionella pneumophila:
Disease Patterns
Legionella bacteria infect annually about 15,000 people in US
while similar statistics were reported in Europe. Numbers can
be much higher since milder infections are not reported
* About 10% of these cases are lethal, particularly for
older/weaker people.
* More severe is the nosocomial legionellosis, and hospital
outbreaks increase the fatality rates up to 50%.
Facts on Legionella disease
- Legionella bacteria can cause severe infections or even permanent
health problems - Treatment requires antibiotics for several weeks up to years for
chronic cases - Better understanding of mechanisms causing these infections and
death is of great importance. - Striking similarities of their pathogenicity mechanisms to those of
Coxiella Burnetti, Rickettsiella grylli or even Mycobacterium
tuberculosis.
Legionella pneumophila
Thin aerobic bacteria
Non-spore forming
Gram-negative
Legionella bacteria are ubiquitous and
mainly parasitize freshwater protozoa.
Pathogenic strains can survive and
replicate within alveolar macrophages
after inhalation of aerosols (eg from
air-conditioning systems, hot baths,
showers)
Extensive studies are required to understand the
pathogenicity mechanisms.
Extensive studies are necessary for drug design.
The bacterial Vacuole (LCV):
A phagolysosome-like compartment
Legionella bacteria require
the formation of a specific
vacuole inside the host cell
where they can replicate
and proliferate
Bacteria are…
Cheap
Very easy to grow
Grow fast
We can make bacteria work for us…
We can “trick” bacteria
to produce proteins for
us
We can study the function of
these proteins
Why are bacteria important for studying the origin of life?
A. They are multicellular
B. They resemble early life forms
C. They evolved after plants
D. They contain nuclei
b
-
Plasma Membrane84
-
Cell and Organelles48
-
DNA structure35
-
DNA replication51
-
transcription and translation69
-
mendelian inheritance65
-
recombination and gene mapping66
-
population genetics and hardy Weinberg equilibrium66
-
bacteria119
-
Viruses101
-
gene regulation90
-
cell cycle83
-
microscope definition19
