Thermophilic cyanobacteria employ tightly regulated physiological and metabolic strategies to thrive at elevated temperatures. Adaptations such as heat-stable photosystems enable sustained growth at extreme temperatures , while dynamic remodeling of pigment composition helps protect cells from intense light and thermal stress. At the same time, flexible metabolic regulation particularly in nitrogen and energy metabolism allows these organisms to maintain photosynthetic activity while tolerating fluctuating environmental conditions typical of hot spring ecosystems.
Mastigocladus laminosus
A thermophilic cyanobacterium capable of nitrogen fixation that can also adapt to growth at temperatures below its optimal range. It is motile via gliding and forms branching filaments. The organism develops gelatinous, cartilaginous, or spongy mats that are dull blue-green to olive-green in color and exhibits a growth rate of approximately 1.5 doublings per day. It shows low tolerance to hydrogen sulfide and produces spores that are resistant to freezing and desiccation.
Thermosynechococcus elongatus
Thermosynechococcus elongatus BP-1 is a thermophilic, unicellular cyanobacterium commonly used as a model organism for oxygenic photosynthesis. It grows optimally at high temperatures (approximately 50-55 °C) and performs efficient light-driven carbon fixation using well-organized photosystems. Because its photosynthetic machinery especially Photosystem I and II is highly stable and well characterized, this organism is widely studied to understand photosynthesis, energy conversion, and thermal adaptation in cyanobacteria.
Synechococcus sp.
These organisms may be thermophilic or mesophilic and are typically obligate photoautotrophs that perform aerobic photosynthesis. Their small cells are cylindrical, ovoid, or rod-shaped and occur singly, in pairs, or in short chains, lacking a surrounding sheath. Cells often form irregular aggregates held together by a slime layer and reproduce through repeated binary fission in a single plane. Most species are nonmotile, while motile forms move by gliding and display positive phototaxis. Currently, 28 species of Synechococcus have been described.