Chemistry Reference
In-Depth Information
subterranean plant surfaces. For example, the pigmented bacteria which are rarely found in
the rhizosphere, and laminate leaf surfaces and solar radiation affect the ecology of the
phyllosphere and promote bacteria to produce pigments as sun screen and will not damage
the cell components. There are two general strategies for osmo-adaptation of prokaryotes
like bacteria under osmotic stress conditions: (1) accumulation of inorganic ions, and (2)
accumulation of low molecular weight organic molecules. In the first strategy, osmotic
equilibrium is maintained which involves the selective influx of potassium (K
+
) and chloride
(Cl
-
) into the cytoplasm. The extremely halophilic archaea of the family
Halobacteriaceae
and
the bacterium
Salinibacter ruber
as well as the moderately halophilc bacteria of the order
Haloanaerobiales
accumulate enormous quantities of K
+
and Cl
-
. The second strategy of osmo-
adaptation, on the other hand, involves the accumulation of a limited range of low-
molecular-weight organic solutes. These include many compounds which are called
compatible solutes including amino acids like proline, glycinebetaine, simple sugars,
polyols, and their derivatives. Some microorganisms, such as hyper/thermophiles, utilize a
combination of both strategies by accumulating negatively charged compatible solutes [86]
and potassium. Great deals of attention have been paid to proline and glycinebetaine as
compatible solutes accumulated as a result of salt or water stress. Relatively few prokaryotes
are capable of de novo synthesis of these compounds. The intracellular concentrations of
these solutes can be regulated in accordance with the external salt concentration, provide
microorganisms with a large degree of flexibility and the possibility to adapt to a wide range
of salt concentrations. However, energetically the production of massive amounts of such
solutes can be costly.
4.3.
Prosopis
cineraria
Prosopis cineraria
is the only species that grow rarely in desert of Qatar. The genus
Prosopis
contains around 45 species of spiny trees and shrubs found in the subtropical regions of
Americas, Africa, Western Asia, and South Asia. They often thrive in arid soil and are
resistant to drought, on occasion developing extremely deep root systems. The microbiology
analyses of
P. cineraria
trees in Qatar [87] showed that the bark was colonized by large
number of bacteria as compared to the leaves. Gram- positive cocci and spore forming bacilli
bacteria are characterized by thick cell wall that is comprised of peptidoglycan (amino acid
polypeptide and a sugar), and the isolated bacilli genus were spore forming that can be
survive in hot, dry conditions, and high irradiation with limited damage to the cell. These
are the most dominant epiphytic form on both leaves and bark. The pigmented bacteria, red
yellow, and orange, were isolated from leaves and bark which exposed to long duration of
light, that pigments well keep the bacterial cells undamaged and resistant to irradiation. The
observed high content of organic matter, soil nutrients, clay and moisture in the sub-canopy
locations of
P. cineraria
trees significantly affect the richness of the below canopy sites [87].
The bacterial soil populations in the rhizosphere are higher than the non-rhizosphere sits
and the lowest bacterial count occurred in the outer canopy soil. Moreover, the presence of
plant litter, animal droppings together with the already existed soil chemical nutrients in the
sub canopy positions of
P. cinerearea
trees possibly increase the enrichment of these patches.
