Year-round sustainable biomass production potential of Nannochloris sp. in outdoor raceway pond enabled through strategic photobiological screening.

Microalgae cultivation utilizes the energy of sunlight to reduce carbon dioxide (CO2) for producing renewable energy feedstock. The commercial success of the biological fixation of carbon in a consistent manner depends upon the availability of a robust microalgae strain. In the present work, we report the identification of a novel marine Nannochloris sp. through multiparametric photosynthetic evaluation. Detailed photobiological analysis of this strain has revealed a smaller functional antenna, faster relaxation kinetics of non-photochemical quenching, and a high photosynthetic rate with increasing light and temperatures. Furthermore, laboratory scale growth assessment demonstrated a broad range halotolerance of 10-70 parts per thousand (PPT) and high-temperature tolerance up to 45 °C. Such traits led to the translation of biomass productivity potential from the laboratory scale (0.2-3.0 L) to the outdoor 50,000 L raceway pond scale (500-m2) without any pond crashes. The current investigation revealed outdoor single-day peak areal biomass productivity of 43 g m-2 d-1 in summer with an annual (March 2019-February 2020) average productivity of 20 g m-2 d-1 in seawater. From a sustainability perspective, this is the first report of successful round-the-year (> 347 days) multi-season (summer, monsoon, and winter) outdoor cultivation of Nannochloris sp. in broad seawater salinity (1-57 PPT), wide temperature ranges (15-40 °C), and in fluctuating light conditions. Concurrently, outdoor cultivation of this strain demonstrated conducive fatty acid distribution, including increased unsaturated fatty acids in winter. This inherent characteristic might play a role in protecting photosynthesis machinery at low temperatures and in high light stress. Altogether, our marine Nannochloris sp. showed tremendous potential for commercial scale cultivation to produce biofuels, food ingredients, and a sustainable source for vegetarian protein.

Enhanced Algal Photosynthetic Photon Efficiency by Pulsed Light.

We present experimental results demonstrating that, relative to continuous illumination, an increase of a factor of 3-10 in the photon efficiency of algal photosynthesis is attainable via the judicious application of pulsed light for light intensities of practical interest (e.g., average-to-peak solar irradiance). We also propose a simple model that can account for all the measurements. The model (1) reflects the essential rate-limiting elements in bioproductivity, (2) incorporates the impact of photon arrival-time statistics, and (3) accounts for how the enhancement in photon efficiency depends on the timescales of light pulsing and photon flux density. The key is avoiding "clogging" of the photosynthetic pathway by properly timing the light-dark cycles experienced by algal cells. We show how this can be realized with pulsed light sources, or by producing pulsed-light effects from continuous illumination via turbulent mixing in dense algal cultures in thin photobioreactors.

Tetramerization at Low pH Licenses DNA Methylation Activity of M.HpyAXI in the Presence of Acid Stress.

Methylation of genomic DNA can influence the transcription profile of an organism and may generate phenotypic diversity for rapid adaptation in a dynamic environment. M.HpyAXI is a Type III DNA methyltransferase present in Helicobacter pylori and is upregulated at low pH. This enzyme may alter the expression of critical genes to ensure the survival of this pathogen at low pH inside the human stomach. M.HpyAXI methylates the adenine in the target sequence (5'-GCAG-3') and shows maximal activity at pH 5.5. Type III DNA methyltransferases are found to form an inverted dimer in the functional form. We observe that M.HpyAXI forms a nonfunctional dimer at pH 8.0 that is incapable of DNA binding and methylation activity. However, at pH 5.5, two such dimers associate to form a tetramer that now includes two functional dimers that can bind and methylate the target DNA sequence. Overall, we observe that the pH-dependent tetramerization of M.HpyAXI ensures that the enzyme is licensed to act only in the presence of acid stress.

Functional analysis of an acid adaptive DNA adenine methyltransferase from Helicobacter pylori 26695.

HP0593 DNA-(N(6)-adenine)-methyltransferase (HP0593 MTase) is a member of a Type III restriction-modification system in Helicobacter pylori strain 26695. HP0593 MTase has been cloned, overexpressed and purified heterologously in Escherichia coli. The recognition sequence of the purified MTase was determined as 5'-GCAG-3'and the site of methylation was found to be adenine. The activity of HP0593 MTase was found to be optimal at pH 5.5. This is a unique property in context of natural adaptation of H. pylori in its acidic niche. Dot-blot assay using antibodies that react specifically with DNA containing m6A modification confirmed that HP0593 MTase is an adenine-specific MTase. HP0593 MTase occurred as both monomer and dimer in solution as determined by gel-filtration chromatography and chemical-crosslinking studies. The nonlinear dependence of methylation activity on enzyme concentration indicated that more than one molecule of enzyme was required for its activity. Analysis of initial velocity with AdoMet as a substrate showed that two molecules of AdoMet bind to HP0593 MTase, which is the first example in case of Type III MTases. Interestingly, metal ion cofactors such as Co(2+), Mn(2+), and also Mg(2+) stimulated the HP0593 MTase activity. Preincubation and isotope partitioning analyses clearly indicated that HP0593 MTase-DNA complex is catalytically competent, and suggested that DNA binds to the MTase first followed by AdoMet. HP0593 MTase shows a distributive mechanism of methylation on DNA having more than one recognition site. Considering the occurrence of GCAG sequence in the potential promoter regions of physiologically important genes in H. pylori, our results provide impetus for exploring the role of this DNA MTase in the cellular processes of H. pylori.

Organic elemental composition in fingernail plates varies between sexes and changes with increasing age in healthy humans.

BACKGROUND: Keratin, an alpha-helical fibrous protein, is the primary component of human nail plates. No data on age-related changes in healthy subjects are present. OBJECTIVE: This study investigated whether keratin amount and composition, as indicated by organic elemental composition of fingernails, varies with aging and between sexes. METHODS: Nail clippings from 225 healthy individuals (93 males, 132 females), aged 20-90 years, were analyzed for carbon (C), nitrogen (N), and sulfur (S) contents with an automatic elemental analyzer. C/N and N/S ratios were calculated. The C/N ratio is indicative of keratin composition, i.e. the ratio of alpha-amino acids and protein. The relationship of elemental composition with dietary intake was analyzed by standardized food record. RESULTS: Females have in their nails more sulfur (p < 0.001) and less nitrogen (p = 0.001), and thereby, a lower N/S ratio than males, whereas their carbon content is not different. With aging, the carbon content increases (p < 0.01, both sexes) and the nitrogen content decreases (p = 0.05, females), both leading to an increased C/N ratio (p < 0.001). By contrast, the sulfur content and the N/S ratio do not change with aging (p > 0.05). The carbon content correlates positively with macronutrient intake in females. Nitrogen and sulfur contents are not related with dietary intake. CONCLUSIONS: Results suggest that the N/S ratio is indicative of sex differences and the C/N ratio of aging in healthy humans. The increasing carbon content with ongoing age could be explained by loss of inorganic material from the nails, followed by a subsequent increase of organic material. The increasing C/N ratio gives evidence that keratin composition changes towards a higher amount of alpha-amino acids with aging.

Facile one-pot synthesis of thio and selenourea derivatives: a new class of potent urease inhibitors.

A facile, one-pot synthesis of thio and selenourea derivatives from amines using tetrathiomolybdate 1 and tetraselenotungstate 2 as sulfur and selenium transfer reagents, respectively, is reported. The compounds were tested for their activity as urease inhibitors and some of the compounds showed potent activity in the nanomolar range towards jack bean urease.

Ocular involvement in diabetes mellitus.

Diabetes is a worldwide medical problem and is a significant cause of morbidity and mortality. It has considerable impact on both the patient and the society because it typically affects individuals in their most productive years. It is also one of the leading causes of blindness and visual impairment. A person with diabetes has 25 times the risk of blindness compared to a non-diabetic. This article reviews the variety of ways in which the eye and its adnexa can be involved in diabetes mellitus.

Evaluation of Optineurin as a candidate gene in Indian patients with primary open angle glaucoma.

PURPOSE: To evaluate the role of the optineurin gene (OPTN) in Indian primary open angle glaucoma (POAG) patients from different parts of the country. METHODS: Two hundred patients with POAG and 200 ethnically matched normal controls were recruited from various parts of India for the study. The entire coding region of OPTN along with the intron-exon boundaries were screened by PCR and single strand conformation polymorphism (SSCP) followed by direct sequencing. A rapid screening method was developed for some of the observed variants by denaturing high performance liquid chromatography (dHPLC). Four variants were also confirmed by digesting the amplicon with appropriate restriction enzymes. RESULTS: Seven nucleotide changes were observed in OPTN of which one was a putative mutation in exon 16 (Arg545Gln) that was observed in six POAG patients and not in the controls (p<0.05). The remaining variants comprised four single nucleotide polymorphisms (SNPs) in the coding region (Thr34Thr, Met98Lys, Arg149Arg, and Asn303Lys) and two in intron 6 (879-10G>A and 879-5C>T). But frequencies of the minor allele were not significantly different among the patients and controls. The Met98Lys variant that was identified to be a potential risk factor for NTG and POAG in some Asian populations and also for modulating IOP in Caucasian populations, did not exhibit any significant association to the disease phenotype. CONCLUSIONS: Despite a putative mutation (Arg545Gln) in some patients, the present study does not suggest a significant involvement of OPTN in POAG patients of Indian origin.

Genetics and bioinformatics of primary open angle glaucoma: an Indian perspective.

Glaucoma is the second largest blinding disorder, after cataract, affecting about 67 million people worldwide. In India about 1.5 million people are blind due to glaucoma. Primary open angle glaucoma is the major sub-type of glaucoma affecting all ages and is genetically complex. Myocilin and optineurin are two different genes that have been implicated for primary open angle glaucoma. This review is focused on the studies being conducted in India on primary open angle glaucoma to identify the molecular defects and new directions undertaken using bioinformatic approaches towards a better understanding of the disease.

Antimicrobial properties of star anise (Illicium verum Hook f).

Star anise (Illicium verum Hook f) has been shown to possess potent antimicrobial properties. Chemical studies indicate that a major portion of this antimicrobial property is due to anethole present in the dried fruit. Studies with isolated anethole (compared with standard anethole) indicated that it is effective against bacteria, yeast and fungal strains.