Cyanobacterium Nostoc Flagelliforme Research Articles

Characterization of Corrinoid Compounds in the Edible Cyanobacterium <i>Nostoc flagelliforme</i> the Hair Vegetable

Vitamin B12 contents in the edible cyanobacterium Nostoc flagelliforme, also known as hair vegetable, were assayed using a microbiological method. We detected high vitamin B12 contents in samples of naturally grown cells (109.2 ± 18.5 μg/100g dry weight) and cultured cells (120.2 ± 53.6 μg/100g dry weight). However, commercially available hair vegetable samples, which comprised fake substitutes and Nostoc, had variable contents (4.8 - 101.6 μg/100g dry weight) because concomitant fake items contain very low vitamin B12 contents. To evaluate whether natural and cultured N. flagelliforme samples contained vitamin B12 or pseudovitamin B12, corrinoid compounds were purified and identified as pseudovitamin B12 (approximately 72%) and vitamin B12 (approximately 28%) using silica gel 60 TLC bioautography and LC/MS. The results suggested that N. flagelliforme contains substantial amounts of pseudovitamin B12, which is inactive in humans.

Emulsifying, Flocculating, and Physicochemical Properties of Exopolysaccharide Produced by Cyanobacterium Nostoc flagelliforme

The emulsifying, flocculating, and physicochemical properties of purified exopolysaccharide (EPS) of terrestrial cyanobacterium Nostoc flagelliforme cultured in liquid media were investigated. The EPS was defined as heteropolysaccharide composed by 41.2 % glucose, 21.1 % galactose, 21.0 % mannose, 2.5 % fructose, 3.6 % ribose, 1.7 % xylose, 0.6 % arabinose, 3.0 % rhamnose, 0.9 % fucose, and 4.3 % glucuronic acid. The EPS possessed higher intrinsic viscosity than other cyanobacterial strains as reported and displayed pseudoplastic behavior in aqueous solution. The EPS produced more stable emulsions with tested hydrocarbons and oils than xanthan gum, and the emulsification indexes with n-hexadecane, liquid paraffin, and peanut oil were higher than 50 %, indicating the strong emulsion-stabilizing capacity. The EPS showed peak flocculating rates of 93.5 and 86.1 % in kaolin and MgO suspension, respectively, and exhibited a better flocculation performance than Al2(SO4)3 and xanthan gum. These results demonstrated that the EPS of N. flagelliforme was a very promising candidate for numerous industrial applications, as it had higher intrinsic viscosity, good emulsification activity, and excellent flocculation capability.

Effect of UV-B radiation on the synthesis of UV-absorbing compounds in a terrestrial cyanobacterium, Nostoc flagelliforme

Effects of two intensities (1 and 5 W m−2) of UV-B radiation on the synthesis of UV-absorbing compounds in a terrestrial cyanobacterium Nostoc flagelliforme were investigated. UV-B radiation resulted in lower biomass. Short period (less than 12 h) of UV-B radiation caused an increase of chlorophyll a content, but subsequent duration of treatment (more than 24 h) resulted in a rapid decrease. N. flagelliforme synthesized UV-absorbing compounds such as scytonemin and mycosporine-like amino acids (MAAs) in response to UV-B radiation. Upon 48 h of exposure to UV-B radiation, scytonemin content in cells increased by 103.8 and 164.0 % at 1 and 5 W m−2, respectively. Oligosaccharide-linked mycosporine-like amino acids increased by 145.5 % after 12 h at 5 W m−2 and 114.5 % after 48 h at 1 W m−2 UV-B radiation. HPLC analysis showed that nine MAAs existed in N. flagelliforme cells both from liquid suspension culture and field colony. But the concentration and kinds of them were different. At the two distinct levels of UV-B radiation, the content of particular MAAs increased, declined, or remained unchanged. Moreover, the appearance of two new MAAs was observed.

Effects of temperature, pH, and UV radiation on alkaline phosphatase activity in the terrestrial cyanobacterium Nostoc flagelliforme

Cyanobacteria produce phosphatases in response to phosphorus deficiency as some other autotrophs. However, little has been documented on the effects of key climate change factors, such as temperature rise and solar UV radiation (280–400 nm), on cyanobacterial alkaline phosphatase activity. Here, we found that the terrestrial cyanobacterium Nostoc flagelliforme showed higher activity of the enzyme with increasing temperature and pH levels, exhibiting maximal values at 45 °C and pH 11, respectively. However, when exposed to solar radiation in the presence of UV-A (320–400 nm) and UV-B (280–320 nm), significant reduction of the enzyme activity was observed at a photosynthetically active radiation (PAR) level of 300 W m−2 (1,450 μmol photons m−2 s−1), which is equivalent or lower than the noontime level of solar PAR at the organism's habitats. UV-A and UV-A + UV-B induced about 21 and 39 % inhibition of the enzyme activity in the 3-h exposures. The decrease in the activity of phosphatase can be attributed to the UV radiation-induced inactivation of the enzyme and indirectly to the UV radiation-induced production of reactive oxygen species.

Effects of UV-B Radiation and Periodic Desiccation on the Morphogenesis of the Edible Terrestrial Cyanobacterium Nostoc flagelliforme

The terrestrial cyanobacterium Nostoc flagelliforme Berk. et M. A. Curtis has been a popular food and herbal ingredient for hundreds of years. To meet great market demand and protect the local ecosystem, for decades researchers have tried to cultivate N. flagelliforme but have failed to get macroscopic filamentous thalli. In this study, single trichomes with 50 to 200 vegetative cells were induced from free-living cells by low light and used to investigate the morphogenesis of N. flagelliforme under low UV-B radiation and periodic desiccation. Low-fluence-rate UV-B (0.1 W m(-2)) did not inhibit trichome growth; however, it significantly increased the synthesis of extracellular polysaccharides and mycosporine-like amino acids and promoted sheath formation outside the trichomes. Under low UV-B radiation, single trichomes developed into filamentous thalli more than 1 cm long after 28 days of cultivation, most of which grew separately in liquid BG11 medium. With periodic desiccation treatment, the single trichomes formed flat or banded thalli that grew up to 2 cm long after 3 months on solid BG11 medium. When trichomes were cultivated on solid BG11 medium with alternate treatments of low UV-B and periodic desiccation, dark and scraggly filamentous thalli that grew up to about 3 cm in length after 40 days were obtained. In addition, the cultivation of trichomes on nitrogen-deficient solid BG11 medium (BG11(0)) suggested that nitrogen availability could affect the color and lubricity of newly developed thalli. This study provides promising techniques for artificial cultivation of N. flagelliforme in the future.

Molecular Cloning of Maltooligosyltrehalose Trehalohydrolase Gene from Nostoc flagelliforme and Trehalose-Related Response to Stresses

A genomic DNA fragment encoding a putative maltooligosyltrehalose trehalohydrolase (NfMTH) for trehalose biosynthesis was cloned by the degenerate primer- PCR from cyanobacterium Nostoc flagelliforme. The ORF of NfMTH is 1,848 bp in length and encodes 615 amino acid residues, constituting a 70 kDa protein. The deduced amino acid sequence of NfMTH contains 4 regions highly conserved for MTHs. By expression of NfMTH in E. coli, the function of this protein was demonstrated, where the recombinant protein catalyzed the hydrolysis of maltooligosyl trehalose to trehalose. The expressions of MTH and maltooligosyltrehalose synthase in the filaments of N. flagelliforme were upregulated significantly under dehydration stress, NaCl stress, and high temperature-drought stress. The accumulations of both trehalose and sucrose in the filaments of N. flagelliforme were also improved significantly under the above stresses. Furthermore, trehalose accumulated in smaller quantities than sucrose did when under NaCl stress, but accumulated in higher quantities than sucrose did when under temperature-drought stress, indicating that both trehalose and sucrose were involved in N. flagelliforme adapted to stresses and different strategies conducted in response to various stress conditions.

Effect of mixed carbon substrate on exopolysaccharide production of cyanobacterium Nostoc flagelliforme in mixotrophic cultures

The effects of organic carbon sources on cell growth and exopolysaccharide (EPS) production of dissociated Nostoc flagelliforme cells under mixotrophic batch culture were investigated. After 7 days of cultivation, glycerol, acetate, sucrose, and glucose increased the final cell density and final EPS concentrations, and mixotrophic growth achieved higher biomass concentrations. The increase in cell growth was particularly high when glucose was added as the sole carbon source. On the other hand, EPS production per dry cell weight was significantly enhanced by adding acetate. For more effective EPS production, the effects of the mixture of glucose and acetate were investigated. Increasing the ratio of glucose to acetate resulted in higher growth rate with BG-11 medium and higher EPS productivity with BG-110 medium (without NaNO3). When the medium was supplemented with a mixture of glucose (4.0 g L−1) and acetate (2.0 g L−1), 1.79 g L−1 biomass with BG-11 medium and 879.6 mg L−1 of EPS production with BG-110 medium were achieved. Adopting this optimal ratio of glucose to acetate established in flask culture, the culture was also conducted in a 20-L photobioreactor with BG-11 medium for 7 days. A maximum biomass of 2.32 g L−1 was achieved, and the EPS production was 634.6 mg L−1.

Consumption offa cai Nostocsoup: A Potential for BMAA exposure fromNostoccyanobacteria in China?

Grown in arid regions of western China the cyanobacterium Nostoc flagelliforme--called fa cai in Mandarin and fat choy in Cantonese--is wild-harvested and used to make soup consumed during New Year's celebrations. High prices, up to $125 USD/kg, led to overharvesting in Inner Mongolia, Ningxia, Gansu, Qinghai, and Xinjiang. Degradation of arid ecosystems, desertification, and conflicts between Nostoc harvesters and Mongol herdsmen concerned the Chinese environmental authorities, leading to a government ban of Nostoc commerce. This ban stimulated increased marketing of a substitute made from starch. We analysed samples purchased throughout China as well as in Chinese markets in the United States and the United Kingdom. Some were counterfeits consisting of dyed starch noodles. A few samples from California contained Nostoc flagelliforme but were adulterated with starch noodles. Other samples, including those from the United Kingdom, consisted of pure Nostoc flagelliforme. A recent survey of markets in Cheng Du showed no real Nostoc flagelliforme to be marketed. Real and artificial fa cai differ in the presence of beta-N-methylamino-L-alanine (BMAA). Given its status as a high-priced luxury food, the government ban on collection and marketing, and the replacement of real fa cai with starch substitutes consumed only on special occasions, it is anticipated that dietary exposure to BMAA from fa cai will be reduced in the future in China.

Effect of cell water amount on photosynthetic yield in the cyanobacterium Nostoc flagelliforme and involvement of NADPH dehydrogenase-mediated cyclic electron transport

Nostoc flagelliforme is a terrestrial cyanobacterium, and water is one of the most important factors limiting its photosynthetic yield. The aims of the present study were to investigate the effect of cell water amount on photosynhetic yield and the role of NADPH dehydrogenase (NDH-1)-mediated cyclic electron transport in this effect. The role of NDH-1-mediated cyclic electron transport was assessed by measuring NDH-1 expression, several chlorophyll fluorescence parameters, and photosynthetic O2 evolution at several time points after cell water had been redried. The results indicated that the highest rate of NDH-1-mediated cyclic electron transport, reflected by post-illumination increase in chlorophyll fluorescence and NDH-1 amount, was only obtained when the cells contained about 1.8 times water relative to dry weight. This was consistent with observed changes in photosynthetic yield, reflected by O2 evolution. However, the highest photochemical activity of photosystem II, reflected by Fv/Fm and qP, could be maintained when N. flagelliforme cells included water in a broad range. This implies that the effect of cell water amount on photosynthetic yield is related to NDH-1-mediated cyclic electron transport. The possible mechanisms of this effect are discussed.

The odd behaviour of carbonic anhydrase in the terrestrial cyanobacterium Nostoc flagelliforme during hydration–dehydration cycles

The terrestrial cyanobacterium Nostoc flagelliforme, inhabiting arid areas, withstands prolonged periods of dehydration. How dehydration and occasional wetting affect inorganic C acquisition in this organism is not well known. As inorganic C acquisition in cyanobacteria often involves carbonic anhydrases (CA), we studied the effect of cycles of hydration and dehydration on the extracellular and intracellular CA activities, at the pH values presumably associated with dew or rain wetting. The external CA of N. flagelliforme (or of the microorganismal consortium of which N. flagelliforme is the main component) is activated by hydration, especially at low pH, and it may facilitate inorganic C acquisition when N. flagelliforme colonies are wetted by dew. Internal CA is present in dry colonies and is rapidly inactivated upon rehydration, therefore an anaplerotic role for this enzyme is proposed.

PHOTOSYNTHETIC INSENSITIVITY OF THE TERRESTRIAL CYANOBACTERIUM NOSTOC FLAGELLIFORME TO SOLAR UV RADIATION WHILE REHYDRATED OR DESICCATED1

Photosynthetic performance of the terrestrial cyanobacterium Nostoc flagelliforme (M. J. Berkeley et M. A. Curtis) Bornet et Flahault during rehydration and desiccation has been previously characterized, but little is known about the effects of solar UV radiation (280–400 nm) on this species. We investigated the photochemical activity during rehydration and subsequent desiccation while exposing the filamentous colonies to different solar radiation treatments. Photochemical activity could be reactivated by rehydration under full‐spectrum solar radiation, the species being insensitive to both ultraviolet‐A radiation (UVAR; 315–400 nm) and ultraviolet‐B radiation (UVBR). When the rehydrated colonies were exposed for desiccation, the effective PSII photochemical yield was inhibited by visible radiation (PAR) at the initial stage of water loss, then increased with further decrease in water content, and reached its highest value at the water content of 10%–30%. However, no significant difference was observed among the radiation treatments except for the moment when they were desiccated to critical water content of about 2%–3%. At such a critical water content, significant reduction by UVBR of the effective quantum yield was observed in the colonies that were previously rehydrated under indoor light [without ultraviolet radiation (UVR)], but not in those reactivated under scattered or direct solar radiation (with UVR), indicating that preexposure to UVR during rehydration led to higher resistance to UVR during desiccation. The photosynthetic CO2 uptake by the desiccated colonies was enhanced by elevation of CO2 but was not affected by both UVAR and UVBR. It increased with enhanced desiccation to reach the maximal values at water content of 40%–50%. The UV‐absorbing compounds and the colony sheath were suggested to play an important role in screening harmful UVR.

Photosynthetic response to salt of aquatic-living colonies of the terrestrial cyanobacterium Nostoc flagelliforme

Aquatic-living colonial filaments of the terrestrial cyanobacterium Nostoc flagelliforme, developed from single cells in laboratory under aquatic conditions, were cultured at different salt concentrations (0-400 mM), and their photosynthetic responses were investigated to see their physiological tolerance. Light-saturated photosynthesis, photosynthetic efficiency and dark respiration showed the highest values in treatments at 20 mM NaCl for 24 or 48 h incubation. Changes in salt level exerted little influence on light saturation point and light compensation point. Patterns of photosynthetic performance as a function of salt were the same after 48 h as those after 24 h treatment, with the largest values at 20 mM NaCl, though photochemical efficiency increased with increased NaCl concentrations in the colonies treated for 48 h. From an applied point of view, the laboratory-generated aquatic living colonies are able to tolerate salt stress when transferred from aquatic to terrestrial environments.

Studies on the photosynthesis of the terrestrial cyanobacterium Nostoc flagelliforme subjected to desiccation and subsequent rehydration

The photosynthetic response of Nostoc fiagelliforme to desiccation and rehydration was investigated. The initial, variable and maximal chlorophyll fluorescence increased from the beginning of desiccation (fully hydrated), reached maxima at a water loss of about 35% and then decreased with further water loss. The area over the fluorescence induction curve reached a maximum at a water loss of about 70%. Pigment contents of chlorophyll a, phycocyanin and allophycocyanin were constant during the photosynthetic recovery phase following rehydration. A fast initial phase of recovery was completed within half an hour after rehydration, and further changes in 77 K fluorescence emission spectra were mainly related to the fluorescence level at 695 nm. A decrease in fluorescence intensities from phycobiliproteins was not detected from 0.5 to 24 h. The initial fluorescence was high at the beginning of rehydration and decreased sharply during photosynthetic recovery. This decrease appeared to be mainly related to the activation or repair of photosystem II (PS II) rather than changes in the coupling and assembly of phycobilisomes. The change of variable fluorescence and the PS II photochemical efficiency value (Fv/Fm) correlated well with the recovery of PS II activity during rehydration. Nostoc fiagelliforme required light and de novo protein synthesis to recover its photosynthetic activity fully during rehydration. In darkness, Fv/Fm recovered 3.4% of activity in dried field samples but 18.9% of activity in samples dry for 2 days. When light was provided in the presence of chloramphenicol, Fv/Fm recovered 10.1% or 39.5% of activity in dried field samples and in samples dry for 2 days, respectively.

Fatty acid profile of the edible filamentous cyanobacterium Nostoc flagelliforme at different temperatures and developmental stages in liquid suspension culture

The fatty acid profile of Nostoc flagelliforme (strains FACHB838 and CCAP1453/33), an edible terrestrial cyanobacterium, at different temperatures (i.e., 15, 20, 25 and 30 °C) and developmental stages (hormogonia, filaments, seriate and aseriate) in liquid suspension culture was investigated. The cyanobacterial species could be classified as Type IIB according to the existing taxonomic system based on fatty acid profiling, due to the presence of C18:3 and the absence of C16:2 and C16:3 fatty acids. Within the temperature range investigated, the content of C18:3n3 increased at the expense of C18:2n3 as temperature decreased, while the fatty acid suites remained unchanged. The degree of fatty acid unsaturation also increased with decreasing temperature, with the highest being 1.28 and 1.37 at 15 °C for the strains FACHB838 and CCAP1453/33, respectively. With respect to the effect of developmental stages, there was a slight variation in fatty acids composition and contents in the two strains without changing the fatty acid suite. At the aseriate stage at 25 °C, the highest C18 fatty acid proportion amounted to 63.17 and 65.08% and the degree of fatty acid unsaturation peaked at 1.32 and 1.31 in the strains FACHB838 and CCAP1453/33, respectively, indicating more long chain unsaturated fatty acids were accumulated at this stage.

Cell differentiation and colony alteration of an edible terrestrial cyanobacterium Nostoc flagelliforme, in liquid suspension cultures.

Morphological characteristics of an edible terrestrial cyanobacterium Nostoc flagelliforme in liquid suspension cultures under photoautotrophic conditions are presented. Different cell forms alternated in a regular manner during the experimentation period (30 d). N. flagelliforme exhibited a very complex life cycle in terms of colony morphology, including mainly 4 different colony morphological forms, viz. hormogonia, filaments, seriate colonies and aseriate colonies. Under laboratory conditions it formed spherical colonies on solid media but not threadlike colonies as it did under natural conditions. The overall life span of the alga was not altered by the existence of different nitrogen sources in the media despite the depression of some cell forms or colony morphologies. Compared with growth on the medium with urea and ammonium as nitrogen sources, the alga on standard medium had a short period of hormogonia and aseriate colony, suggesting that both ammonium and urea could stimulate the formation of hormogonia, at the same time inhibiting the formation of heterocystous cells. The new information on the growth and morphology of N. flagelliforme could be potentially used for the scale-up or field cultivation.