Cloning and characterization of hoxH genes from Arthrospira and Spirulina and application in phylogenetic study.
ABSTRACT Partial hoxH genes of 2 cyanobacterial genera, including 5 strains of Arthrospira and 2 strains of Spirulina, were cloned and characterized. This gene encodes the large subunit of nickel-iron hydrogenase. The results showed that these genes comprised 1349 nucleotides in Arthrospira and 1343 nucleotides in Spirulina, respectively. The GC contents of hoxH were 45.7% to 47.3% in Arthrospira and up to 50.4% to 50.9% in Spirulina. The hoxH gene was demonstrated to be single copy by Southern analysis, and its transcription was verified by reverse transcriptase polymerase chain reaction in Arthrospira platensis FACHB341. The similarities of nucleotide sequences among the 5 strains of Arthrospira ranged from 95.7% to 99.8%, which are higher than those between Arthrospira and Spirulina (72.9-77.0%). However, similarity between the 2 Spirulina strains was only 72.5%, slightly lower than that between the 2 genera. A phylogenetic tree based on hoxH was constructed. All 5 strains of Arthrospira formed a monophyletic clade, which was highly supported by bootstrap value, while the 2 strains of Spirulina were separated into 2 different clades.
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ABSTRACT: Environmental and nutritional conditions that optimize the yield of hydrogen (H(2)) from water using a two-step photosynthesis/fermentation (P/F) process are reported for the hypercarbonate-requiring cyanobacterium "Arthrospira maxima." Our observations lead to four main conclusions broadly applicable to fermentative H(2) production by bacteria: (i) anaerobic H(2) production in the dark from whole cells catalyzed by a bidirectional [NiFe] hydrogenase is demonstrated to occur in two temporal phases involving two distinct metabolic processes that are linked to prior light-dependent production of NADPH (photosynthetic) and dark/anaerobic production of NADH (fermentative), respectively; (ii) H(2) evolution from these reductants represents a major pathway for energy production (ATP) during fermentation by regenerating NAD(+) essential for glycolysis of glycogen and catabolism of other substrates; (iii) nitrate removal during fermentative H(2) evolution is shown to produce an immediate and large stimulation of H(2), as nitrate is a competing substrate for consumption of NAD(P)H, which is distinct from its slower effect of stimulating glycogen accumulation; (iv) environmental and nutritional conditions that increase anaerobic ATP production, prior glycogen accumulation (in the light), and the intracellular reduction potential (NADH/NAD(+) ratio) are shown to be the key variables for elevating H(2) evolution. Optimization of these conditions and culture age increases the H(2) yield from a single P/F cycle using concentrated cells to 36 ml of H(2)/g (dry weight) and a maximum 18% H(2) in the headspace. H(2) yield was found to be limited by the hydrogenase-mediated H(2) uptake reaction.Applied and Environmental Microbiology 09/2008; 74(19):6102-13. · 3.95 Impact Factor
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ABSTRACT: Some species of cyanobacteria naturally produce hydrogen gas as a byproduct of anaerobic fermentation at night using fixed-carbon compounds that are produced photosynthetically in daylight under aerobic conditions. The nutrient requirements for optimal activity of these two systems of metabolic energy production are different and in some cases incompatible. Resolving these conflicting needs has not been widely considered, yet is critical for application of cyanobacteria as efficient cell factories for hydrogen production. The filamentous nondiazotrophic cyanobacterium Arthrospira maxima ferments in the dark both intracellular fixed-carbon compounds and added glucose, producing hydrogen exclusively via a bidirectional NiFe hydrogenase. We show that the hydrogenase activity in cell extracts (in vitro) and whole cells (in vivo) correlates with the amount of Ni2+ in the growth medium (saturating activity at 1.5 mu M Ni2+). This and higher levels of nickel in the medium during photoautotrophic growth cause stress leading to chlorophyll degradation and a retarded growth rate that is severe at ambient solar flux. We show that A. maxima acclimates to micromolar nickel concentrations at reduced light intensity after a delay which minimizes chlorophyll degradation and restores normal growth rate. Nickel adaptation permits normal biomass accumulation while significantly increasing the rate of fermentative hydrogen production. Relative to nickel-free media (only extraneous Ni2+), the average hydrogenase activity in cell extracts (in vitro) increases by 18-fold, while the average rate of intracellular H-2 production within intact cells increases 6-fold. Nickel is inferred to be a limiting cofactor for hydrogenase activity in many cyanobacteria grown using photoautotrophic conditions, particularly those lacking a high-affinity Ni2+ transport system. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.International Journal of Hydrogen Energy. 04/2008; 33:2014-2022.
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ABSTRACT: Anatoxin-a is a potent neurotoxin produced by several species of cyanobacteria. This alkaloid may cause fatal intoxication to exposed organisms and this has raised concerns over the increasing popularity of food supplements containing cyanobacteria. These are being marketed with alleged health properties for animal and human consumption. These supplements most commonly contain the genera Spirulina (Arthrospira) and Aphanizomenon and their consumption represent a potential route for anatoxin-a exposure in cases where adequate quality control is not undertaken. In this work, several dietary supplements containing cyanobacteria from different commercial suppliers were evaluated for the presence of anatoxin-a by high performance liquid chromatography with fluorescence detection. Additionally, the presence of the previously derivatized anatoxin-a was confirmed by using Gas chromatography-mass spectrometry. A total of 39 samples were analysed in the study. Results showed that three of the samples (7.7%) contained anatoxin-a, at concentrations ranging from 2.50 to 33 microg g(-1). Quality control of cyanobacterial food supplements is required to avoid potential health effects in humans and animals.Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 07/2009; 47(9):2189-95. · 2.99 Impact Factor