Phototactic motility of Synechocystis Sp. uniwg from brackish environment
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Date
2009
Authors
Toh, Pamela Shi Ying
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Abstract
Although type IV pilus has been implicated in the phototactic motility of
some unicellular cyanobacteria, its regulatory mechanism and the effect of
environmental factors on motility are still unknown. Equally important is the
ability of cyanobacterial cells to anchor themselves to an environment that is
conducive for survival. In this study, the motility of a newly isolated unicellular
brackish cyanobacterium Synechocystis sp. UNIWG was compared with its
morphologically and phylogenetically similar freshwater cyanobacterium
Synechocystis sp. PCC6803. The phototactic motility of Synechocystis sp.
UNIWG on semisolid BG-11 medium with various concentrations of nitrogen
source was significantly faster than that of Synechocystis PCC6803.
Interestingly, the cell surface of Synechocystis sp. UNIWG showed the presence
of rigid spicules when grown in liquid BG-11, a phenomenon that was absent in
Synechocystis PCC6803. Negative staining of Synechocystis sp. UNIWG
revealed the presence of two distinct pilus morphotypes, which resembled type
IV pili and thin pili of Synechocystis PCC6803. This suggested a similar pattern
of phototactic motility in both strains. However, the rigid spicules on
Synechocystis sp. UNIWG seem to be more of a hindrance during type IV
motility. It was found that the spicules were degraded when the cells moved,
such as under prolonged darkness and/or depletion of nitrogen source,
indicating that the function of the spicules is to attach the cell to an environment
that is conducive for its survival. Thus, Synechocystis sp. UNIWG shows
phototaxis regulation that is more complex than Synechocystis PCC6803. In
addition, Synechocystis sp. UNIWG exhibited tolerance to salinity ranges
between 2-8 g L-1 and other metal ions such as calcium, mangan and
magnesium are required for the phototactic response of this strain.
Description
Master
Keywords
Biological Science , Phototactic , Brackish