Heat-Stress Responses Differ among Species from Different ‘Bangia’ Clades of Bangiales (Rhodophyta)

The red alga ‘Bangia’ sp. ESS1, a ‘Bangia’ 2 clade member, responds to heat stress via accelerated asexual reproduction and acquires thermotolerance based on heat-stress memory. However, whether these strategies are specific to ‘Bangia’ 2, especially ‘Bangia’ sp. ESS1, or whether they are employed by all ‘Bangia’ species is currently unknown. Here, we examined the heat-stress responses of ‘Bangia’ sp. ESS2, a newly identified ‘Bangia’ clade 3 member, and Bangia atropurpurea. Intrinsic thermotolerance differed among species: Whereas ‘Bangia’ sp. ESS1 survived at 30 °C for 7 days, ‘Bangia’ sp. ESS2 and B. atropurpurea did not, with B. atropurpurea showing the highest heat sensitivity. Under sublethal heat stress, the release of asexual spores was highly repressed in ‘Bangia’ sp. ESS2 and completely repressed in B. atropurpurea, whereas it was enhanced in ‘Bangia’ sp. ESS1. ‘Bangia’ sp. ESS2 failed to acquire heat-stress tolerance under sublethal heat-stress conditions, whereas the acquisition of heat tolerance by priming with sublethal high temperatures was observed in both B. atropurpurea and ‘Bangia’ sp. ESS1. Finally, unlike ‘Bangia’ sp. ESS1, neither ‘Bangia’ sp. ESS2 nor B. atropurpurea acquired heat-stress memory. These findings provide insights into the diverse heat-stress response strategies among species from different clades of ‘Bangia’.

On Bangia atropurpurea (Bangiales, Rhodophyta), the strictly protected red alga in Serbia

The first observation of the red alga Bangia atropurpurea (Bangiales, Rhodophyta) in Serbia was in 1991 in the Trgoviski Timok River (Eastern Serbia). From 1991 to 2017, the species was sporadically observed at four more locations in three hillmountain rivers in Southwestern (the Gvozdacka River and the Raska River) and Eastern (the Nisava River - two localities) Serbia. More intensive research on this alga was carried out from 2017 to 2020, and a total of 220 localities in 132 hillmountain watercourses were studied. Bangia atropurpurea was recorded at six locations in Southwestern and Eastern Serbia. Five of these locations represent new B. atropurpurea localities in Serbia (the Brusnicka River, the Golijska Moravica River, the Panjica River, the Resava River, and the second locality in the Trgoviski Timok River), while one of them is already known from previous studies (the Raska River). The species was found in running, moderately hard and very hard, well-oxygenated, slightly alkaline waters, mainly low in inorganic nutrients, and in highly variable values of temperature and conductivity. Despite the long period since its first observation in Serbian rivers, the species is still known in a small number of localities. The small number of localities, low relative abundance, and various anthropogenic influences affecting its habitats have led the species to be recognized as endangered and strictly protected in Serbia. The intensive development of small hydropower plants which have emerged in recent years may threaten B. atropurpurea habitats.

Photosynthetic performance of two freshwater red algal species

Photosynthetic performances of two freshwater red algal populations from freshwaters of the Carpathian basin were measured in this study. Populations were collected from different habitats: Bangia atropurpurea from Lake Balaton and Batrachospermum gelatinosum from the Tapolca stream. Their photosynthesis was studied in a wide range of temperature (5–35 °C) and light intensity (0–1150 μmol m−2 s−1) in a photosynthetron. We found both species’ photosynthesis maxima at 25 °C but B. atropurpurea had significantly higher photosynthetic production. Low and medium values were calculated for the species’ photoadaptation parameters. Compensation light intensities determined in this study were similar to those obtained in previous studies. Both species utilized light efficiently; photoinhibition was detected only at two measuring temperatures for Bangia and at four measuring temperatures for Batrachospermum. P-T characteristics of the species revealed that both have temperature optima at 25 °C under high and medium light intensities but there are no such remarkable optima at low irradiance. The biomass specific respiration of both species increased with increasing temperature. We confirmed the good light utilization of these red algal species but found temperature optima higher than reported previously.

Evaluation of antioxidant properties of phycobiliproteins and phenolic compounds extracted from Bangia atropurpurea

Bangia atropurpurea is a freshwater red filamentous alga. In this study, we report on the recovery yield of purified phycobiliproteins, total phenolic content (TPC) and their antioxidant capacity. B. atropurpurea suspended in phosphate buffer (pH 7.2), saturated with ammonium sulphate and further isolated R-phycoerythrin and phycocyanin from phycobilisome structure by gel filtration with Sephadex G-200. Phenolic compounds extracted by variable polarity solvents to exhibit optimum yield. Folin–Ciocalteu method was used to determine the TPC, while 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric-reducing antioxidant power (FRAP) assays were used to quantitate the antioxidant activity of phycobiliproteins and phenolic compounds. B. atropurpurea predominantly contains R-phycoerythrin 54.80 % of the total protein extracted at purity ratio A562 to A280 of 4.45 while, phycocyanin displayed 16 % recovery yield at purity ratio A615 to A280 of 2.18. The purified R-phycoerythrin exhibited better antioxidant activity than phycocyanin extract and BHT synthetic antioxidant by exhibiting (IC50%=7.66 ±0.81µg/mL) and 54.74 ± 0.11 mg GAE/1g extract for, DPPH scavenging and FRAP assay, respectively. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of purified R-phycoerythrin and phycocyanin proteins have showed apparent single band at molecular weight of 19.6 kDa and 17.5 kDa, respectively. The methanol-soluble extract displayed the utmost TPC, 80.97±0.53 mg GAE/1g extract compared to phenolic content in other organic solvents used for extraction. In accordance with TPC, methanol-soluble extract exhibited as the most effective DPPH radical scavenging and ferric reduction, (IC50%=14.63±0.79 µg/mL) and 37.79±0.27 mg GAE/1g extract, respectively. The presence of R-phycoerythrin, phycocyanin and phenolic compounds in an array, amplifies the antioxidant property of B. atropurpurea.