| 1. |
- Ferro, Lorenza, 1989-
(författare)
-
Wastewater treatment and biomass generation by Nordic microalgae : growth in subarctic climate and microbial interactions
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nordic native microalgal strains were isolated, genetically classified and tested for their ability to grow in municipal wastewater. Eight of the isolated strains could efficiently remove nitrogen and phosphate in less than two weeks. Two of these strains, Coelastrella sp. and Chlorella vulgaris, were found to have high biomass concentration and total lipid content; also two Desmodesmus sp. strains showed desirable traits for biofuel-feedstock, due to their fast growth rates and high oil content.The adaptation to subarctic climate was comparatively evaluated in three Nordic strains (C. vulgaris, Scenedesmus sp. and Desmodesmus sp.) and a collection strain (S. obliquus). Their growth performance, biomass composition and nutrients removal was investigated at standard (25°C) or low temperature (5°C), under continuous light at short photoperiod (3 h light, 25°C) or moderate winter conditions (6 h light, 15°C). Only the Nordic strains could grow and produce biomass at low temperature, and efficiently removed nitrogen and phosphate during both cold- and dark-stress. Phenotypic plasticity was observed in Scenedesmus and Desmodesmus under different growth conditions, adaptation to low temperature increased their carbohydrate content. Short photoperiod strongly reduced growth rates, biomass and storage compounds in all strains and induced flocculation in C. vulgaris, which, however, performed best under moderate winter conditions.The symbiotic relationships between the Nordic microalga C. vulgaris and the naturally co-occurring bacterium Rhizobium sp. were investigated batchwise under photoautotrophic, heterotrophic and mixotrophic conditions, comparing the co-culture to the axenic cultures. The photoautotrophic algal growth in BG11 medium mainly supported Rhizobium activity in the co-culture, with no significant effects on C. vulgaris. In synthetic wastewater, a synergistic interaction only occurred under mixotrophic conditions, supported by CO2/O2 exchange and a lower pH in the culture, resulting in higher biomass and fatty acids content and more efficient wastewater treatment in the co-culture. Under heterotrophic conditions, the lower biomass production in the co-culture suggested a competition for nutrients, although nutrients removal remained efficient.A pilot-scale high rate algal pond (HRAP) located in Northern Sweden was inoculated with the collection strain Scenedesmus dimorphus UTEX 417 and operated from spring to autumn. Using metabarcoding of 18S and 16S rRNA genes, the microbial diversity of eukaryotic and prokaryotic communities was revealed. S. dimorphus was initially stable in the culture, but other microalgal species later colonized the system, mainly due to parasitic infections and predation by zooplankton in summer. The main competitor algal species were Desmodesmus, Pseudocharaciopsis, Chlorella, Characium and Oocystis. Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were the most abundant bacterial phyla in the HRAP. The structure of the microbial communities followed a seasonal variation and partially correlated to environmental factors such as light, temperature and nutrients concentrations.Overall, these results contribute with new knowledge on the establishment and optimization of microalgal-based wastewater treatment systems coupled with biomass generation in Nordic areas. The use of native microalgal species is proposed as a potential strategy to overcome the limitations posed to algal cultivation in subarctic regions.
|
|
| 2. |
- Mishra, Laxmi S., 1983-
(författare)
-
FtsH metalloproteases and their pseudo-proteases in the chloroplast envelope of Arabidopsis thaliana
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- By cleaving peptide bonds, proteases either activate or degrade proteins and maintain protein quality control in response to various developmental stimuli and environmental factors. My work has focused on elucidating the role of the filamentation temperature sensitive protein H (FtsH) proteases. FtsHs belong to a membrane-embedded class of proteases found in eubacteria, animals and plants, which are located in the organelles of endosymbiosis (mitochondria and chloroplasts). They possess an AAA+ (ATPase associated with various cellular activities) and a peptidase M41 domain containing the HEXXH consensus sequence in the Zn2+ metalloprotease domain. FtsH proteases are known to form ring-like homo- or hetero-hexameric complexes. Arabidopsis thaliana, the model plant used in this study, contains seventeen AtFtsH proteases, of which twelve are presumably proteolytically active and five presumably proteolytic inactive members, known as AtFtsHi (i for inactive). In AtFtsHi members, the HEXXH motif is either deleted (AtFtsHi3) or mutated (AtFtsHi1, 2, 4, 5). Twelve AtFtsHs (AtFtsH 1, 2, 5–9, 11, 12 and AtFtsHi 1-5) are targeted to the chloroplast, whereas the remaining three (AtFtsH 3, 4 and 10) are mitochondrial. In Paper I, we demonstrate that AtFtsH12 interacts with AtFtsHi1, 2, 4, 5 to form a heteromeric complex. Abundance of these AtFtsH12-AtFtsHi complexes alters the accumulation of TIC (translocon on the inner chloroplast membrane) complexes. Transgenic mi12 (miRNA) knockdown plants that express lower amounts of AtFtsH12 displayed a pale-seedling and an aberrant chloroplast phenotype. mi12 plants displayed lowered total chlorophyll (Chla+Chlb) amount compared to wild type (WT), complementation lines and native AtFtsH12 promoter overexpressor (ox12) lines. Our biochemical studies identified drastic modifications in the total proteome of mi12 seedlings. N-terminome analyses of mi12 seedlings showed undisturbed plastidic protein maturation. In Paper II, we have shown that single mutants depleted in AtFTSHI1, 2, 4 or 5 are embryo-lethal, suggesting the pseudo-proteases to have an indispensable role in seed germination. This study further identified “weak” Atftshi1, Atftshi4, Atftshi3-1(kd) and Atftshi3-2 homozygous mutants, which develop into plants with altered photosynthetic efficiency. Field experiments were performed to determine the Darwinian fitness of these homozygous as well as heterozygous AtFtsHi mutants. The results suggested AtFtsHi enzymes to be critical during early developmental stages. A complete Atftshi3 knockdown mutant (Atftshi3-1(kd)) was identified (described in Paper III), which is not embryo-lethal and tolerates drought better than WT plants. Atftshi3-1(kd) leaves were smaller with fewer and smaller stomatal aperture. Above ground, Atftshi3-1(kd) leaves displayed lowered stomatal conductance and increased WUEi (intrinsic water-use efficiency), while below ground, the root-associated bacterial community showed a typical drought stress response. Upregulated transcripts of the ABA-responsive genes in leaves of Atftshi3-1(kd) compared to WT indicate the drought tolerance to be controlled independently of ABA. To conclude, AtFtsHi pseudo-proteases affect various stages of plant development and abiotic stress management, especially drought.
|
|
| 3. |
- Funk, Christiane, et al.
(författare)
-
D1' centers are less efficient than normal photosystem II centers
- 2001
-
Ingår i: FEBS Letters. - 0014-5793 .- 1873-3468. ; 505:1, s. 113-117
-
Tidskriftsartikel (refereegranskat)abstract
- One prominent difference between the photosystem II (PSII) reaction center protein D1 ' in Synechocystis 6803 and normal D1 is the replacement of Phe-186 in D1 with leucine in D1 '. Mutants of Synechocystis 6803 producing only D1 ', or containing engineered D1 proteins with Phe-186 substitutions, were analyzed by 77 K fluorescence emission spectra, chlorophyll a fluorescence induction yield and decay kinetics, and flash-induced oxygen evolution. Compared to D1-containing PSII centers, D1 ' centers exhibited a 50% reduction in variable chlorophyll a fluorescence yield, while the flash-induced O-2 evolution pattern was unaffected. In the F186 mutants, both the P680(+)/Q(A)(-) recombination and O-2 oscillation pattern were noticeably perturbed.
|
|
| 4. |
- Hall, Michael, et al.
(författare)
-
The HhoA protease from Synechocystis sp. PCC 6803 : novel insights into structure and activity regulation
- 2017
-
Ingår i: Journal of Structural Biology. - : Elsevier. - 1047-8477 .- 1095-8657. ; 198:3, s. 147-153
-
Tidskriftsartikel (refereegranskat)abstract
- Proteases play a vital role in the removal of proteins, which become damaged due to temperature or oxidative stress. Important to this process in the cyanobacterium Synechocystis sp. PCC6803 is the family of Deg/HtrA proteases; HhoA (sll1679), HhoB (sll1427) and HtrA (slr1204). While previous studies have elucidated the structures of Deg/HtrA proteases from Escherichia coli and from the chloroplast of the higher plant Arabidopsis thaliana, no structural data have been available for any Deg/HtrA protease from cyanobacteria, the evolutionary ancestor of the chloroplast. To gain a deeper insight into the molecular mechanisms and regulation of these proteins we have solved the structure of the Synechocystis HhoA protease in complex with a co-purified peptide by X-ray crystallography. HhoA assembles into stable trimers, mediated by its protease domain and further into a cage-like hexamer by a novel interaction between the PDZ domains of opposing trimers. Each PDZ domain contains two loops for PDZ-PDZ formation: interaction clamp one and two (IC1, IC2). IC1 interacts with IC2 on the opposing PDZ domain and vice versa. Our structure shows a peptide bound to a conserved groove on the PDZ domain and the properties of this pocket suggest that it binds substrate proteins as well as the neo C-termini of cleaved substrates. In agreement with previous studies showing the proteolytic activity of HhoA to be activated by Ca2+ or Mg2+, binding of divalent metal ions to the central channel of the trimer by the L1 activation loop was observed.
|
|
| 5. |
- Alling, Teodor, et al.
(författare)
-
Nordic microalgae produce biostimulant for the germination of tomato and barley seeds
- 2023
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Microalgal biomass may have biostimulating effects on plants and seeds due to its phytohormonal content, and harnessing this biostimulating effect could contribute to sustainable agriculture. Two Nordic strains of freshwater microalgae species Chlorella vulgaris and Scenedesmus obliquus were each cultivated in a photobioreactor receiving untreated municipal wastewater. The algal biomass and the supernatant after algal cultivation were tested on tomato and barley seeds for biostimulating effects. Intact algal cells, broken cells, or harvest supernatant were applied to the seeds, and germination time, percentage and germination index were evaluated. Seeds treated with C. vulgaris, in particular intact cells or supernatant, had up to 25 percentage units higher germination percentage after 2 days and an overall significantly faster germination time (germinated on average between 0.5 and 1 day sooner) than seeds treated with S. obliquus or the control (water). The germination index was higher in C. vulgaris treatments than in the control for both tomato and barley, and this was observed for both broken and intact cells as well as supernatant. The Nordic strain of C. vulgaris cultivated in municipal wastewater thus shows potential for use as biostimulant in agriculture, adding novel economic and sustainability benefits.
|
|
| 6. |
- Ferro, Lorenza, 1989-, et al.
(författare)
-
Growth performance and nutrient removal of a Chlorella vulgaris-Rhizobium sp. co-culture during mixotrophic feed-batch cultivation in synthetic wastewater
- 2019
-
Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 44
-
Tidskriftsartikel (refereegranskat)abstract
- The subarctic green algal strain Chlorella vulgaris 13-1, newly isolated from Northern Sweden, and its co-occurring bacterium Rhizobium sp. were tested for their ability to produce valuable biomass and remove nutrients from synthetic wastewater during mixotrophic feed-batch cultivation at multiple hydraulic retention times (HRTs = 7, 5 and 3 days). The algal-bacterial co-culture showed better performance compared to the corresponding axenic cultures (HRT = 7 days), with a biomass concentration of 0.63 +/- 0.03 g/L and removal rates of 49.5 +/- 6.1% TOC, 55.7 +/- 8.04% TN and 95.6 +/- 3.6% TP at steady-state. Culture stability and a high nutrient removal capacity were recorded in the algal-bacterial co-culture even at HRTs of 5 and 3 days. Interestingly, reducing the HRT from 7 to 5 days resulted in a higher lipid content of the biomass, further reduction of the HRT to 3 days enhanced both daily biomass productivity (1.03 g/L/day) and nutrient assimilation. Mixotrophic co-cultivation of C. vulgaris-Rhizobium sp. can successfully be applied for wastewater reclamation in continuous mode at HRT of 3-7 days, and thus is suitable for both summer and winter conditions in Nordic countries.
|
|
| 7. |
- Hernández-Prieto, Miguel Angel, 1975-
(författare)
-
The Small Cab-like Proteins in the cyanobacterium Synechocystis sp. PCC 6803
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Small Cab-like Proteins (SCPs) in the cyanobacterium Synechocystis sp. PCC 6803 accumulate in cells grown under different stress conditions. Genes coding for SCPs have been found in all sequenced organisms performing oxygenic photosynthesis and even in the genomes of cyanophages. Deletion of multiple scp genes in Synechocystis resulted in mutants with severely impaired growth and altered pigment content. These findings indicate the importance of SCPs in photosynthesis; however, their specific function is not well understood. SCPs share a chlorophyll-binding motif with the plant light harvesting complex, suggesting that they bind chlorophyll. Here I describe my findings, which unambiguously show that SCPs are able to bind chlorophyll in vitro. Although they affect both the stoichiometric ratio of Photosystem I to II and chlorophyll stability, they do not seem to be directly involved in non-photochemical quenching. I was able to reveal the location of the SCPs within the cyanobacterial cell: in stressed cells they attach to Photosystem II in the thylakoid membrane. Furthermore, I revealed the presence of another light-harvesting like (Lil)/SCP protein in Synechocystis sp. PCC 6803. The gene, slr1544, codifying for this newly characterised LilA protein, co-transcribes together with scpD and also appears to bind to Photosystem II during stress.
|
|
| 8. |
- Mehariya, Sanjeet, et al.
(författare)
-
Biopolymer production from biomass produced by Nordic microalgae grown in wastewater
- 2023
-
Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 376
-
Tidskriftsartikel (refereegranskat)abstract
- Biomass from four different Nordic microalgal species, grown in BG-11 medium or synthetic wastewater (SWW), was explored as inexpensive carbohydrate-rich feedstock for polyhydroxybutyrate (PHB) production via microbial fermentation. Thermochemical pre-treatment (acid treatment followed by autoclavation) with 2% hydrochloric acid or 1% sulphuric acid (v/v) was used to maximize sugar yield prior to fermentation. Pre-treatment resulted in ∼5-fold higher sugar yield compared to the control. The sugar-rich hydrolysate was used as carbon source for the PHB-producing extremophilic bacterium Halomonas halophila. Maximal PHB production was achieved with hydrolysate of Chlorococcum sp. (MC-1) grown on BG-11 medium (0.27 ± 0.05 g PHB/ g DW), followed by hydrolysate derived from Desmodesmus sp. (RUC-2) grown on SWW (0.24 ± 0.05 g PHB/ g DW). Nordic microalgal biomass grown on wastewater therefore can be used as cheap feedstock for sustainable bioplastic production. This research highlights the potential of Nordic microalgae to develop a biobased economy.
|
|
| 9. |
- Mehariya, Sanjeet, et al.
(författare)
-
Improving the content of high value compounds in Nordic Desmodesmus microalgal strains
- 2022
-
Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 359
-
Tidskriftsartikel (refereegranskat)abstract
- Nordic Desmodesmus microalgal strains (2-6) and (RUC-2) were exposed to abiotic stress (light and salt) to enhance lipids and carotenoids. The biomass output of both strains increased by more than 50% during light stress of 800 μmol m-2 s-1 compared to control light. The biomass of Desmodesmus sp. (2-6) contained most lipids (15% of dry weight) and total carotenoids (16.6 mg g-1) when grown at moderate light stress (400 μmol m-2 s-1), which further could be enhanced up to 2.5-fold by salinity stress. Desmodesmus sp. (RUC-2) exhibited maximal lipid (26.5%) and carotenoid (43.8 mg L-1) content at light intensities of 400 and 100 μmol m-2 s-1, respectively. Salinity stress stimulated lipid accumulation by 39%. Nordic Desmodesmus strains therefore are not only able to tolerate stress conditions, but their biomass considerably improves under stress. These strains have high potential to be used in algal bio-factories on low-cost medium like Baltic seawater.
|
|
| 10. |
|
|
