Endosymbiotic theory (or Symbiogenesis) is an evolutionary theory that was initially proposed more than 100 years ago to explain the origins of eukaryotic cells from the prokaryotic ones. This theory postulated that several key organelles of eukaryotes could have been originated as a symbiosis between separate organisms. Later in the 1920s, this idea was extended to explain the origins of mitochondria and, some 30 years ago, it was definitively accepted. According to this theory, a pro-bacteria was hosted by an eukaryotic cell and evolved within it, providing the host with all the ATP that is needed (therefore acting as a cellular “power house”). Some other studies were confirming this hypothesis by assessing that substantial gene additions were impossible without the energetic boost provided by the colonizing mitochondrion in the eukaryotic lineage.
More recently this idea was questioned by a work in which the authors analyzed the cellular energetics and genomics data from a wide variety of species obtaining an indication that, relatively to the ATP requirements of a cell throughout its life, the costs of a gene at the DNA, RNA, and protein levels decline with cell volume in both bacteria and eukaryotes. These costs are usually sufficiently large to be perceived by natural selection in bacterial populations, but not in eukaryotes experiencing high levels of random genetic drift.
Cyanobacteria
are the most primitive group of photoautotrophic prokaryotic micro-flora,
probably appeared on the Earth during Precambrian era while there was no
ozone-shield and intense solar light with high incidence of harmful ultraviolet
(UV) radiation. Survival of life under extreme condition of UV radiation ishighly menacing. The high-energetic UV (280–400 nm) radiation has great
potential for cell damage either through direct effects on biologically relevant
key machinery such as DNA, proteins and lipids, or indirect effects via the
production of reactive oxygen species (ROS), leading to mutagenesis, and loss
of fundamental cellular physiology and metabolic functions.
However, in
the face of adverse effects of intense solar radiation, cyanobacteria developed
some efficient repair mechanisms along with various enzymatic/non-enzymaticdefense systems to counteract the harmful effects of UV radiation. Moreover,
owing to strong defense systems, cyanobacteria are so far surviving and
thriving well as dominant primary producers over a wide range of aquatic and
terrestrial ecosystems including the extreme habitats such as deserts, hot
springs, acidic, saline, and extremely cold polar region
Early detection of oral premalignant lesions which might
evolve into oral cancer by screening methods using suitable markers is
critical. Saliva as a diagnostic fluid seems to be promising and has a number
of advantages when compared to the blood-based testing. Histopathologicaldiagnosis is still gold standard when diagnosing oral premalignant lesions,
however, studies upon the role of salivary cytokines show promising results
although more studies are needed on a larger sample. Cytokines have an
important role in oral diseases and increased levels of interleukin 6 (IL-6)
and tumor necrosis factor alpha (TNF-alpha) have been reported in patients with
cancer and premalignant lesions such as oral lichen planus and oral submucous
fibrosis. Brailo et al.reported significantly increased levels of salivary IL-6
and TNF-alpha in patients with oral leukoplakia when compared to healthy
controls.
Furthermore, the levels of salivary IL-6 and TNF-alpha did not
correlate with the size of leukoplakic lesions nor with its localization.
Recently, Brailo et al.reported that salivary IL-1β and IL-6 were significantly
higher in oral cancer patients than in patients with leukoplakia and control
group. No significant differences in salivary TNF-α between either of thegroups were seen. Sharma et al.reported increased salivary IL-6 levels in
patients with leukoplakia and coexisting periodontitis and in periodontitis
patients in comparison to the healthy controls. The same authors found that in
the leukoplakia group, increased salivary IL-6 level was noticed together with
increase in the severity of dysplasia. Sharma et al.concluded that the use of
tobacco had a significant role in the elevation of salivary IL-6 which is
contrary to the results of Brailo et al.
Pioneering work on the synthesis and properties of these MC NS have been reported over the past few years.reported the 2D single-sheet GaS and GaSe transistors via a micromechanical cleavage technique, demonstrating excellent electron differential mobility.obtained ultrathin GaSe NS by mechanical cleavage-solvent exfoliation method, which demonstrated fast response, high responsivity and quantum efficiency in photodetectors. The layered GaSe NS can also be used as a Li-ion battery (LiB) anode reported multilayer GaTe flakes which exhibit a higher photoresponsivity than graphene, MoS2, and other layered compounds, showing promising applications in optoelectronic and photosensitive devices.
2D InSe ultrathin sheets have been reported as a promising candidate in optoelectronic devices, such as field-effect transistors and highly responsive photodetectors fabricated few-layered InSe on rigid (SiO2/Si plate) and flexible (polyethylene terephthalate) substrates, yielding superior photoresponsivities of conducting broad band photodetection from 450 to 785 nm.
in oxygenic photosynthesis, two photosystems (PS II and PS I), using light, work in series to extract electrons from water to generate reducing power (in the form of NADPH) in linear electron transport, while the energy of the protons after water photo-oxidation is conserved in the form of ATP. Additionally, a cyclic electron flux (CEF) around PS I is also coupled to the formation of ATP . Together, NADPH and ATP drive the conversion of CO2 intocarbohydrates. CEF is central to the regulation of photosynthesis , but its quantification, six decades after the discovery, has been difficult because of the absence of net formation of a product or consumption of a reactant .
An indirect method has been used whereby the steady-state total electron flux through PS I (ETR1) and the linear electron flux through both photosystems (LEF) are determined, with both measurements made in the same leaf tissue under identical conditions. The difference (ΔFlux = ETR1 − LEF) is an upper estimate of CEF because ETR1 in general includes other partial electron fluxes through PS I. ΔFlux in greenhouse-grown spinach leaves increases with irradiance, and does not reach a maximum even when LEF is light-saturated .
More recently this idea was questioned by a work in which the authors analyzed the cellular energetics and genomics data from a wide variety of species obtaining an indication that, relatively to the ATP requirements of a cell throughout its life, the costs of a gene at the DNA, RNA, and protein levels decline with cell volume in both bacteria and eukaryotes. These costs are usually sufficiently large to be perceived by natural selection in bacterial populations, but not in eukaryotes experiencing high levels of random genetic drift.
