Download Life in a different time frame

Life in a different time frame
Paulina Tamez Hidalgo, PhD student
And so life began
Early life 3.5-3.8 billion
years ago
•Unicellular organisms
Photosynthetic bacteria
arose prior to 2.8 billion
years
•Shaping Earth’s
atmosphere
Despite the great variety
of animals and plants that
have populated the Earth
•Microbes are the
dominant life forms
present throughout
almost all our planet’s
After all these years…
1. Bacteria have colonized every known environment
2. They have developed an extremely wide variety of
metabolic types
Source of energy
Sunlight
Source of
carbon
Organic
compounds
Organic
compound
s
Photoheterotrop Chemoheterotrop
hy
hy
(photosynthetic (Enterobacteria)
bacteria)
CO2
Photoautotroph
y
(purple nonsulfur bacteria)
Inorganic
compounds
Lithoheterotrop
hy
(Iron bacteria)
Chemoautotrophy Lithoautotrophy
(methanogens)
(acetogens)
3. They evolved in various shapes and sizes
Coccoid and rodshaped
(Streptococcus and
Bacillus)
Comma’s form
(Vibrio cholerae)
Club shaped
(Clostridium
botulinum)
Filamentous
(Anabaena)
Helical form
(Helicobacter pylori)
Spirochaete
(Treponema
pallidum)
4. They have not changed dramatically as have been
demonstrated by studying ancient bacteria isolated from
 Abdominal tissue of bees trapped in amber 25 to 40 million
years old
(Cano and Borucki, 1995)
 Inside a salt crystal 250 million years old
(Vreeland et al., 2000)
 Ancient glacial ice 750,000 years old
(Christner et al., 2003)
Why they remain for so long?
Certain type of bacteria (Firmicutes), wide-spread form
“endospores”
 Dormant form to which bacteria can reduce itself
 Not a reproductive structure
 Remain dormant for long periods of time
 When the conditions are favorable, can reactivate itself to a
vegetative cell (active stage)
Endospores of Bacillus subtilis
Inside an Endospore
: mix of proteins, amino polysaccharides
and lipids
: a complex protein shell, contains enzymes
that are involved in germination
: a thick layer of
peptidoglycan
: a relatively dry compartment that houses the
spore, dipicolinic acid, and small acid-soluble
proteins
: DNA
Sensitive to its surroundings.
It has the ability to react to the reintroduction small amounts of nutrients
that results in the almost immediate conversion of dormant back to an
actively growing cell
Dormancy as strategy to survive
For years, was thought that the deep sub-seabed (high-pressure,
minimal oxygen and low supply of nutrients and energy) was an
uninhabitable environments
In the late 80’s microbial cells were discovered in sediment
cores
Since then, our knowledge about this deep biosphere has
expanded
 There is a log-log linear decrease with depth
 Higher in the surface sediment and relatively lower at several hundred
meters below (where the sediment has been deposited many million
years ago)
Barker, (2012)
Living microbes were buried thousand to millions years ago
How do they remain active?
a) Consuming nutrients at a very slow rate
The slowly growing bacteria are important for the global
storage of organic carbon and thereby for the oxygen
content of the atmosphere
Different sampling
sites at the Peru
margin
Lomstein et al. (2012)
b) Forming endospores
Vegetative cells
X Mur-based measurements
DPA-based measurements
Endospores are also abundant in the
terrestrial environment
Ammann et al. (2011)
 Uncertain the ratio of vegetative cells versus
endospores cells
 Little is still known regarding the factors controlling
their abundance and distribution in soil and sediments
 The link between environmental conditions,
biogeochemical zonation, and endospore abundance
is poorly known
measurements on:
Total organic carbon (TOC) and total nitrogen
(TN)
Amino acids
Amino sugars
Dipicolinic acid
Cell counts
Dormancy as strategy to live the long
life
Questions?