Nostoc commune
1. Classification
a. Higher order taxa
a. Higher order taxa i. Domain: Bacteria
Phylum: Cyanobacteriota Class: Cyanophyceae Order: Nostocales Family: Nostocaceae (1)
b. Species Nostoc commune (2)
2. Description and significance
Nostoc commune is a cyanobacteria living in freshwater often found growing on soils and rocks. N. commune forms spherical colonies with trichomes consisting of filaments with a gelatinous polysaccharide matrix, which allows it to survive in harsh conditions (3). N. commune is found all over the world including temperate and tropical habitats but also in extreme areas, like polar regions, due to its ability to fix nitrogen. Because of its capacity for nitrogen fixation and its survival without water, N. commune has potential to improve the sustainability of farming practices (4). N. commune also has anti-inflammatory and antioxidant features: the cyanobacteria’s ability to repress pro-inflammatory cytokines can subdue inflammatory diseases (3). Much research has been conducted on its efficacy in the medical field, including lowering serum cholesterol levels (5) and anti-infective (6), antibacterial (7), and antioxidant properties (8).
3. Genome structure
The genome of N. commune has not been sequenced so far. However, other species of the Nostoc genus have had their genome sequenced, such as the Nostoc sp. strain NIES-3756. This specific strain was found to have one chromosome and two plasmids – two in the case of the NIES-3756 strain (9). What makes N. commune unique is its extreme desiccation tolerance where such colonies can sustain cell growth without differentiation for over 100 years (10). This phenomenon is called cryptobiosis, the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill (11). The extracellular polysaccharide (EPS) in N. commune colonies account for more than 60% of the dry weight (12). The hindrance or removal of EPS is governed by the distinctive sigJ gene that regulates the extracellular polysaccharide (13). With the transcription of sigJ, the absence of EPS causes a significant reduction in the stress tolerance of photosynthesis during desiccation. This specialized extracellular polysaccharide is what makes N. commune unique to other bacteria in its genus and to other bacteria overall. N. commune’s specialized EPS, among other things, allow for the cell to tolerate freezing up to -60ºC in Antarctic Deserts (14) and to –269 °C in liquid helium in the laboratory (15).
4. Cell structure
N. commune is a Gram-negative photosynthetic cyanobacterium that is well adapted to terrestrial environments, as it has the ability to regulate metabolic processes based on the resources available and the ability to withstand harsh temperatures. In natural habitats, N. commune forms non-spherical, irregularly spreading, macroscopic colonies. When N. commune is wet, it is observed to be bluish-green, olive-green, or brown in appearance with a slippery texture, but in dry conditions, it transforms into a crisp, brownish mat (16). At the cellular level, the bacteria consist of trichomes of cells embedded in a jelly-like-extracellular matrix (17). The gelatinous polysaccharide matrix allows N. commune to fix nitrogen in harsh conditions with no oxygen or no light (18).
5. Metabolic processes
At a temperature of 0-30ºC and proper moisture levels, N.commune carries out oxygenic photosynthesis and metabolic activities (19, 20), but under dry conditions, the process is inhibited. Light becomes dangerous when not being absorbed so N.commune deactivates photosystem II. This is because if photosynthesis is halted while photochemical reactions are active due to inhibition of the Calvin cycle, strong reductants or oxidants could be created and these could harm the organism (21). Extracellular pigments like the brownish scytonemin and mycosporine-like amino acids absorb ultraviolet light and play a role in protecting the cells from high irradiance and UV radiation (19). Several types of cells are present in N.commune including heterocysts that fix atmospheric nitrogen, providing nitrogen and nutrition to the filamentous cells (22).
6. Ecology
N. commune is found across the globe in a wide range of landscapes due to its unique ability to withstand harsh temperatures. Colonies have been found to avoid the extremely cold and dry habitats of Antarctic valleys and the Arctic, to hot desert soils around the world like the Sonoran desert in Arizona. N. commune can be found in a variety of habitats in all seven continents of the world (10, 23). N. commune has been found near Lake Colleen, in southern Victorian Land, and Antarctica, where the temperatures reach close to -60°C (24). N.commune is ecologically important in dry environments because it acts as a pioneer species, providing an ecosystem with the required organic nutrients and ingredients for other organisms to survive (25).
7. Pathology
N. commune does not enact any harmful effects on plants or animals. Generally, many of the species within the Nostoc genus can produce cyanotoxins, hepatotoxic microcystin, cyclic heptapeptides, and β-methylamino-l-alanine, a neurotoxic non-protein amino acid (26 & 27). 33% of the Nostoc strains exhibit cytotoxic activity against mammalian cells. The only hazardous consequence of N. commune is that due to its slippery nature, it could pose a dangerous covering on rocks which categorizes it as a fall risk to pedestrians (28).
8. Current Research
N. commune has been traditionally used as a health and immune promoter for years. The isolated polysaccharides from N. commune vauch exhibit strong antibacterial and antimicrobial properties. Additionally, there are current studies exploring the anticancer and tumor-preventing potential of N. commune (29). Furthermore, N. commune exhibits impressive anti-inflammatory features. This quality can be attributed to the isolation of noscomin, an extracellular diterpenoid, and metabolite granting the microbe with antibacterial properties. Noscomin exhibits antibacterial activity against Bacillus cereus, Staphylococcus epidermidis, and Escherichia coli. However, there is ongoing research on the additional benefits of noscomin (7). Another isolated, secondary metabolite, reduced scytonemin, was shown to play a critical role as a second messenger in regulating anti-inflammatory effects (30). The anti-inflammatory effects could also be attributed to the methods N. commune employs to prevent the production of pro-inflammatory cytokines. Ingesting N. commune could be a safer and more natural anti-inflammatory drug than manufactured pharmaceuticals on the market (31). N. commune has wide environmental applications. It could potentially be a new and sustainable treatment for industrial wastewater; N. commune decreased the amount of biological and chemical pollutants in wastewater by 70%, especially metals (32). In addition, N. commune’s nitrogen fixation capabilities have been tested numerous times. N. commune, in both aerobic and anaerobic conditions, exhibits nitrogen fixation when combined with glucose. However, aerobic conditions demonstrate a slightly higher nitrogen fixation activity (18). Not only does N. commune use polysaccharides to express antimicrobials and antibacterials, but it maintains water and resists dehydration, even in extreme environments. While N. commune growth in an environment lacking oxygen is slow, it remains alive and plant growth plates incubated with this microbe continue to increase (12). Moreover, cyanobacteria, such as N. commune, can grow in nitrogen-limited and harsh conditions (33).
9. Authorship Statement
Classification and overall editing were completed by Selah Youn. The Introduction of the N. commune was completed by Yuki Ando. Organism key points including genome structure, cell structure, metabolic processes, and ecology were completed by Vasisht Poosapati. Current Research was articulated by Audrey Shen. Organism key points on pathology and other important sections, authorship statement, Chat GPT reformations, bibliography, and picture descriptions were done by Adam Milewski. Further research and acquisition of more information about N. commune was completed by all group members. =10. Photos
11. References
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