OLIGOTROPHS ; microbial life at low nutrients.

2.  Presenter : Tahir Ali
 Presented To: Dr Sagheer Ahmed
 Roll # College/uni: 852/023814
Govt. post graduate college of science wahdat
road lahore.

3. Oligotrophs: From Greeks oligos mean ‘few’ and
trophos means ‘food’.
Definition:
An oligotroph is an organism that can live in an
environment that offers very low levels of nutrients.
They may be contrasted with copiotrophs, which
prefer nutritionally rich environments.
Oligotrophs are characterized by:
 slow growth,
 low rates of metabolism,
 and generally low population density.

4. e.g:
1.Oligotrophic bacterium sphingomonas sp.
 Single copy of rRna operon .
 Relatively small in size and genome.
2. Cyclolasticus oligotrophicus:
 Same as sphingomonas sp.
3. Arthrobacter sp
4. Pseudomonas sp
5. Caulobacter sp.
6. Certain lower fungi.

5. Occurrence;
 Deep oceans sediments
 Caves
 Glacial and polar ice
 Aquifers
 Leached soil
These environments are known as oligotrophic
environments.
The term “oligotrophic” is commonly used to
describe terrestrial and aquatic environments with
very low concentrations of nitrates, iron,
phosphates, and carbon sources.

6. Characteristics Adaptations;
 A substrate uptake system (i.e in case of aerobic
culture oxygen is substrate) that is able to acquire
nutrients from its surrounding.
 Have large surface area to volume ratio( high
density of transporter sites).
 An inherent resistance to environment stresses e.g
heat, hydrogen peroxide and ethanol.

7. Complex regulatory mechanism is activated in
response to starvation (limited nutrients level):
 Expression of starvation genes results in reduction
in size and the formation of ultra micro bacteria,
usually by a process of reductive division.

8.  Protective starvation proteins are synthesized .
 Amino acids uptake increases.
 At this stage cells may enter a dormant ,anabiotic
state that permits them to survive for a long period
of time without any division
Reductive Division;
It is a form of cell adaptations to adverse environmental conditions.
Reductive division allows the cell to gain advantage under
conditions of starvation due to increased surface to volume ratio,
producing more spherical cells .

9.  1. Antarctica
 Antarctic environments offer very little to sustain
life as most organisms are not well adapted to
live under nutrient-limiting conditions and cold
temperatures (lower than 5 °C).
 As such, these environments display a large
abundance of psychrophiles that are well
adapted to living in an Antarctic biome.
 Most oligotrophs live in lakes where water helps
support biochemical processes for growth and
survival.

10. 2.Crooked Lake:
 is an ultra-oligotrophic glacial lake with a
thin distribution of heterotrophic and
autotrophic microorganisms.
 The microbial loop plays a big role in cycling
nutrients and energy within this lake, despite
particularly low bacterial abundance and
productivity in these environments.
Species discovered in this lake include:
Ochromonas, Chlamydomonas, Scourfeldia,
Cryptomonas and Akistrodesmus falcatus.

11. 3. Oligotrophic soil environments(Deeper):
 The oligotrophic soil environments include
agricultural soil, frozen soil, et cetera.
 Various factors, such as decomposition, soil
structure, fertilization and temperature, can
affect the nutrient-availability in the soil
environments.
 e.g Collimonas is one of the species that are
capable of living in the oligotrophic soil.
 Collimonas form symbiont relation with fungi.

13. References:
 Environmental microbiology by Alan H. varnam.
 Environmental microbiology by Eugene L. Medsen.
 Slideshare.net
 Wikipedia.net