Comparative Genomics and Physiological Investigation of a New Arthrospira/Limnospira Strain O9.13F Isolated from an Alkaline, Winter Freezing, Siberian Lake.

Cyanobacteria from the genus Arthrospira/Limnospira are considered haloalkalotolerant organisms with optimal growth temperatures around 35 °C. They are most abundant in soda lakes in tropical and subtropical regions. Here, we report the comprehensive genome-based characterisation and physiological investigation of the new strain O9.13F that was isolated in a temperate climate zone from the winter freezing Solenoye Lake in Western Siberia. Based on genomic analyses, the Siberian strain belongs to the Arthrospira/Limnospira genus. The described strain O9.13F showed the highest relative growth index upon cultivation at 20 °C, lower than the temperature 35 °C reported as optimal for the Arthrospira/Limnospira strains. We assessed the composition of fatty acids, proteins and photosynthetic pigments in the biomass of strain O9.13F grown at different temperatures, showing its potential suitability for cultivation in a temperate climate zone. We observed a decrease of gamma-linolenic acid favouring palmitic acid in the case of strain O9.13F compared to tropical strains. Comparative genomics showed no unique genes had been found for the Siberian strain related to its tolerance to low temperatures. In addition, this strain does not possess a different set of genes associated with the salinity stress response from those typically found in tropical strains. We confirmed the absence of plasmids and functional prophage sequences. The genome consists of a 4.94 Mbp with a GC% of 44.47% and 5355 encoded proteins. The Arthrospira/Limnospira strain O9.13F presented in this work is the first representative of a new clade III based on the 16S rRNA gene, for which a genomic sequence is available in public databases (PKGD00000000).

The toxicological effects of oxybenzone, an active ingredient in suncream personal care products, on prokaryotic alga Arthrospira sp. and eukaryotic alga Chlorella sp.

Oxybenzone (OBZ; benzophenone-3, CAS# 131-57-7) is a known pollutant of aquatic and marine ecosystems, and is an ingredient in over 3000 personal care products, as well as many types of plastics. The aim of this study is to explore the different toxicities of OBZ on an eukaryotic (Chlorella sp.) and a prokaryotic algae (Arthrospira sp.). OBZ is a photo-toxicant, with all observed toxicities more sever in the light than in the dark. Cell growth and chlorophyll inhibition were positively correlated with increasing OBZ concentrations over time. Twenty days treatment with OBZ, as low as 22.8 ng L-1, significantly inhibited the growth and chlorophyll synthesis of both algae. Both algae were noticeably photo-bleached after 7 days of exposure to OBZ concentrations higher than 2.28 mg L-1. Relatively low OBZ concentrations (0.228 mg L-1) statistically constrained photosynthetic and respiratory rates via directly inhibiting photosynthetic electron transport (PET) and respiration electron transport (RET) mechanisms, resulting in over production of reactive oxygen species (ROS). Transmission and scanning electron microscopy showed that the photosynthetic and respiratory membrane structures were damaged by OBZ exposure in both algae. Additionally, PET inhibition suppressed ATP production for CO2 assimilation via the Calvin-Benson cycle, further limiting synthesis of other biomacromolecules. RET restriction limited ATP generation, restricting the energy supply used for various life activities in the cell. These processes further impacted on photosynthesis, respiration and algal growth, representing secondary OBZ-induced algal damages. The data contained herein, as well as other studies, supports the argument that global pelagic and aquatic phytoplankton could be negatively influenced by OBZ pollution.

Detailed characterization of the Arthrospira type species separating commercially grown taxa into the new genus Limnospira (Cyanobacteria).

The genus Arthrospira has a long history of being used as a food source in different parts of the world. Its mass cultivation for production of food supplements and additives has contributed to a more detailed study of several species of this genus. In contrast, the type species of the genus (A. jenneri), has scarcely been studied. This work adopts a polyphasic approach to thoroughly investigate environmental samples of A. jenneri, whose persistent bloom was noticed in an urban reservoir in Poland, Central Europe. The obtained results were compared with strains designated as A. platensis, A. maxima, and A. fusiformis from several culture collections and other Arthrospira records from GenBank. The comparison has shown that A. jenneri differs from popular species that are massively utilized commercially with regard to its cell morphology, ultrastructure and ecology, as well as its 16S rRNA gene sequence. Based on our findings, we propose the establishment of a new genus, Limnospira, which currently encompasses three species including the massively produced L. (A.) fusiformis and L. (A.) maxima with the type species Limnospira fusiformis.

Structural and Physicochemical Characterization of Spirulina (Arthrospira maxima) Nanoparticles by High-Resolution Electron Microscopic Techniques.

The objective of this work was to obtain Spirulina (Arthrospira maxima) nanoparticles (SNPs) by using high-impact mechanical milling and to characterize them by electron microscopy and spectroscopy techniques. The milling products were analyzed after various processing times (1-4 h), and particle size distribution and number mean size (NMS) were determined by analysis of high-resolution scanning electron microscopic images. The smallest particles are synthesized after 3 h of milling, had an NMS of 55.6±3.6 nm, with 95% of the particles being smaller than 100 nm. High-resolution transmission electron microscopy showed lattice spacing of ~0.27±0.015 nm for SNPs. The corresponding chemical composition was obtained by energy-dispersive X-ray spectroscopy, and showed the presence of Ca, Fe, K, Mg, Na, and Zn. The powder flow properties showed that the powder density was higher when the average nanoparticle size is smaller. They showed free flowability and an increase in their specific surface area (6.89±0.23 m2/g) up to 12-14 times larger than the original material (0.45±0.02 m2/g). Fourier transform infrared spectroscopy suggested that chemical damage related to the milling is not significant.

Divergence in three newly identified Arthrospira species from Mexico.

Arthrospira (Spirulina) is a microalgae that has a unique set of biological characteristics which are very useful for a broad range of applications. Based on its worldwide requirements, this investigation was conducted to collect, isolate and identify the local Arthrospira strains in the central and western part of Mexico. We have successfully collected, isolated and identified (morphologically as well as molecularly) three Arthrospira strains from different regions in Mexico. Morphological studies were conducted by analyzing the size and shape of the helix, the spiral pattern, cell length and width with the help of light microscopy and for molecular analysis, the 16S rRNA and internally transcribed spacer (ITS, 16S-23 rRNA) gene partial sequence were used followed by phylogenetic analysis. The three species were completely different in their filament size and width whereas their ITS sequences were the same in size and more than 87 % similar in nucleotide sequence. The resulted morphological and phylogenetic analysis concluded that the three stains were identified as Arthrospira platensis. Inspite of their morphological variations and differences they were grouped genetically into one cluster along with the A. platensis of reported strains of Gene Bank database (NCBI). One of the isolated strains NPS-0, is probably the biggest Arthrospira strains ever reported and can be suitable for industrial scale biomass and protein production.

Kinetics and dynamics for light state transition in cyanobacterium Spirulina platensis cells.

Light state transition in oxygenic organisms was defined as the ability to equalize the excitation of the two photosystems for maximal photosynthetic efficiency. In cyanobacteria, extensive researches on state transition have continuously provided new knowledge in the past decades but the molecular mechanism and physiological significance are still ambiguous. In this work, kinetics and dynamics of the transition from state 1 to state 2 in cyanobacterium Spirulina platensis cells were studied at different intensity of orange light from 10 to 120 µmol m(-2) s(-1). It was revealed that the state transition worked constantly independent of light intensity while the rates varied. The synchronous fluorescence kinetics for phycobilisome (PBS) and photosystem components indicated that the state transition was entirely regulated by "mobile PBS", and continuously changed fluorescence amplitudes suggested a series of intermediate states were involved between state 1 and state 2. The dynamic property of PBS movement during the state transition was revealed by (1,0) distribution of photo-linkable PBSs, indicating a collective movement of all PBSs. The results suggest that state transition in cyanobacteria possesses not only physiological but also photochemical significance.

Polyhydroxyalkanoate (PHA) synthesis by Spirulina subsalsa from Gujarat coast of India.

Cyanobacteria have many unexploited potential for natural products with a huge variability in structure and biological activity. Their products are species specific and substrate+growth condition specific. Under stress conditions they are reported to produce biopolymers like EPS and PHA, which can be produced extracellularly and intracellularly, respectively. Polyhydroxyalkanoates are polymers of biological origin, they are also capable of being completely broken down to water and carbon dioxide by microorganisms found in a wide range of environments, such as soil, water, and sewage. We have studied marine cyanobacteria Spirulina subsalsa from Veraval coast, Gujarat, India, producing PHA under increased sodium chloride (NaCl) concentration (5% enhancement to the ASNIII medium), The biopolymer was chemically characterized through FTIR, NMR, TGA, and DSC. The present study shows increased PHA accumulation in S. subsalsa by twofold increased NaCl concentration in the growth media.

Variable pressure and environmental scanning electron microscopy: imaging of biological samples.

The use of elevated gas pressures in the sample chamber of a scanning electron microscope (i.e., variable pressure SEM, or VPSEM) together with specialized electron detectors create imaging conditions that allow biological samples to be examined without any preparation. Specific operating conditions of elevated pressures combined with sample cooling (usually restricted to the environmental SEM range) can allow hydrated samples to be maintained in a pristine state for long periods of time. Dynamic processes also can be easily observed. A wider range of detector options and imaging parameters introduce greater complexity to the VPSEM operation than is present in routine SEM. The current instrumentation with field emission electron sources has nanometer-scale beam resolution (approx 1 nm) and low-voltage beam capability (0.1 kV). However, under the more extreme variable pressure conditions, useful biological sample information can be achieved by skilled operators at image resolutions to 2 to 4 nm and with primary electron beam voltages down to 1.0 kV. Imaging relating to electron charge behavior in some biological samples, generally referred to as charge contrast imaging, provides information unique to this VPSEM and environmental SEM that closely relates to luminescence imaged by confocal microscopy.

Factors indicating culture status during cultivation of Spirulina (Arthrospira) platensis.

Factors indicating culture status of two Spirulina platensis strains were monitored in a batch mode cultivation for 36 days. Changing mode in all factors showed a common turning point, indicating shift of cell or culture status. Mean biomass productivity was highly sustained until day 22, chlorophyll a concentration peaked on day 22, pH value was >12 on day 22, coil number was abruptly shortened on day 22, and floating activity was sustained at greater than 79% after day 22, indicating that day 22 is a criterion reflecting phase-transfer in cell physiology in a batch culture system. Many of these changes may have been caused by increased pH, suggesting that pH control is essential for mass production of S. platensis. Fluctuations in floating activity were likely induced by the number of cellular gas vacuoles. Consequently, coil number per trichome and floating activity of S. platensis could readily act as simple indicators for determination of culture status or harvesting time of cells.