Pawan Kumar Singh

Anticancer compounds from cyanobacterium Lyngbya species: a review

The use of synthetic anticancer drugs and other methods followed in cancer therapy have several side effects; and ineffective methods or drugs give a way to the emergence of drug resistant cancer cells, with the intrinsic metastasis as the aftermath. Anticancer efficacy of many cyanobacterial compounds has been claimed in literature. This review considers 144 compounds isolated and characterized from seven species of the non-nitrogen fixing filamentous cyanobacterium Lyngbya, as the source of antineoplastic agents, which have been screened primarily with cancer cell lines. Structure and information of Lyngbya compounds were retrieved from databases, PubChem, ChemSpider and ChEBI. Information and clinical status of Lyngbya compounds are summarized, and those might be the future anticancer drugs for drug-resistant cancer cells even, as complementary/adduct drugs, if pursued thoroughly in pharmacology and pharmaceutics.

Growth and biochemical characterization of associations between cyanobionts and wheat seedlings in co-culturing experiments

N2-fixing cyanobacteria are unique in their capacity to form symbiotic associations with a wide range of eukaryotic hosts belonging to different plant groups. The present study was undertaken to analyze the interactions of the cyanobiont PI 01 (from Azolla pinnata) and Nostoc PCC 9229 (from Gunnera monoika) with wheat seedlings, in co-culturing experiments. Each of the cyanobionts enhanced significantly the volume of root and shoot biomass in the experimental cultures. The transverse sections of roots in the co-cultured seedlings revealed the presence of aseriate packets of cyanobionts below the root epidermis. The investigated cyanobionts excreted amino acids (His, Met, Val) and sugars into the medium, while indoleacetic acid was detected when the cyanobionts were grown in a tryptophan containing medium. During the co-culturing, sugars and proline were detected in the extracellular filtrates. It can be hypothesized that these sugars and amino acids may serve as signal substances in the development of functional associations between the relevant cyanobionts and the wheat seedlings.

Characterization of the Biocidal Spectrum of Extracellular Filtrates of Microcystis aeruginosa

The effect of dichloromethane (DCM) and ethyl acetate (EA) extract of a cyanobacterium, Microcystis aeruginosa was evaluated against unicellular cyanobacteria and the phytopathogenic fungus Rhizoctonia solani. Fractionation of the filtrate showed the presence of five spots of different Rf values on silica gel coated plates indicating the presence of a number of compounds in the extract. A marked reduction in growth (52%) of the fungus was recorded on the plates supplemented with cyanobacterial extract, indicating the involvement of anti-fungal metabolite(s). The extract did not show any negative influence on seed germination and growth of seedlings of wheat, rice and mung, emphasizing the suitability of the compound for use in agriculture.

Toxicity of biocides to native cyanobacteria at different rice crop stages in wetland paddy field

Biocides (herbicides and insecticides) are intensively being used in rice cultivation, despite several adverse non-target effects on native cyanobacteria. Comparative effects of three herbicides (benthiocarb, butachlor, and 2,4-D) and four insecticides (furadon, phorate, methyl parathion, and ekalux) were studied at field-recommended doses. Field experiments of rice were carried out for three consecutive seasons in completely randomized block designs in both rainy and winter croppings at the Central Rice Research Institute, Cuttack, India. Toxicities of seven biocides individually to native cyanobacteria growing with rice crops in wetland fields were assessed for growth and acetylene reduction activity (ARA); several crop parameters of paddy were estimated concomitantly. It was observed that applications of butachlor and benthiocarb individually significantly decreased growth (15.86 and 17.50%), ARA (0.16 and 0.68%), and N-yield (0.26 and 0.85%) of the native cyanobacteria, whereas these parameters increased (24.04% in growth, 0.25% in ARA, and 0.40% in N-yield) due to the application of 2,4-D. Of the tested insecticides, furadon, phorate, and methyl parathion enhanced the growth (17.8, 10.7, and 11.7%), N2-fixation (0.10, 0.097, and 0.074%), and N-yield (0.16, 0.18, and 0.20%) of cyanobacteria, whereas ekalux had no significant effect on cyanobacteria. On the basis of cyanobacterial parameters, biocides could be recommended for rice crops in the order furadon < phorate < methyl parathion < ekalux. Applications of 2,4-D and furadon individually in comparison to the rest other biocides enhanced rice yield. These finding could help to revise integrated strategies of weed and pest management in wetland rice agriculture to save non-target soil microorganisms, particularly cyanobacteria.

Phylogeny and evolutionary genetics of Frankia strains based on 16S rRNA and nifD-K gene sequences.

16S rRNA and nifD–nifK sequences were used to study the molecular phylogeny and evolutionary genetics of Frankia strains isolated from Hippöphae salicifolia D. Don growing at different altitudes (ecologically classified as riverside and hillside isolates) of the Eastern Himalayan region of North Sikkim, India. Genetic information for the small subunit rRNA (16S rRNA) revealed that the riverside Frankia isolates markedly differed from the hillside isolates suggesting that the riverside isolates are genetically compact. Further, for enhanced resolutions, the partial sequence of nifD (3′ end), nifK (5′ end) and nifD–K IGS region have been investigated. The sequences obtained, failed to separate riverside isolates and hillside isolates, thus suggesting a possible role of genetic transfer events either from hillside to riverside or vice versa. The evolutionary genetic analyses using evogenomic extrapolations of gene sequence data obtained from 16S rRNA and nifD–K provided differing equations with the pace of evolution being more appropriately, intermediate. Values of recombination frequency (R), nucleotide diversity per site (Pi), and DNA divergence estimates supported the existence of an intermixed zone where spatial isolations occurred in sync with the temporal estimates. J. Basic Microbiol. 2015, 54, 1–9

Salinity induced changes in the chloroplast proteome of the aquatic pteridophyte Azolla microphylla

The growth of the nitrogen fixing aquatic pteridophyte Azolla microphylla is severely affected by salinity. Salinity exposure (0.5%) resulted in significant reduction in chlorophyll a and b content, altered chl a/b ratio and photosynthetic efficiency (Fv/Fm). Chloroplasts maintain photosynthesis but are highly sensitive to salinity stress. Chloroplast proteins extracted from A. microphylla was separated by two-dimensional electrophoresis (2DE) and approximately 200 proteins were observed on each gel. Forty two differentially expressed protein spots were detected and out of this 17 could be identified through MALDI-TOF-MS/MS analysis. Out of the 17 identified proteins, 15 were found to be down regulated and 2 proteins were up regulated. Most of the down regulated proteins were associated with Calvin cycle, ATP synthesis, oxygen evolution, photosystem I and ROS scavenging. The results show changes in proteome dynamics of the chloroplasts of A. microphylla and such changes may lead to reduction in growth and metabolism. The primary target of salinity in A. microphylla is photosynthesis and the changes in the proteome dynamics of the chloroplasts lead to reduced growth.

Physico-chemical factors influencing spore germination in cyanobacterium Fischerella muscicola

Spore (akinete) formation in the heterocystous and branched filamentous cyanobacterium Fischerella muscicola involves a significant increase in cell size and formation of several endospores in each of the cells. In present study, the physico‐chemical factors (pH, light sources, nutrient deficiency, nitrogen sources, carbon sources, and growth hormones) affecting the germination of spores of F. muscicola were examined. Increase in spore germination frequency was detected above pH 8 with maximum germination (46.04%) recorded at pH 9, whereas a significant decrease in germination was observed at pH 6 when compared to control (pH 7.6). Spore germination was not observed at pH 5. Among light sources germination frequency followed the following order, that is, red light (39.9%) > white light (33.8%) > yellow light (3.4%) > green light (1.3%) whereas germination did not take place in dark and blue light. Ammonium chloride (NH4Cl) supported maximum (99.5%) germination frequency followed by calcium nitrate (Ca(NO3)2), potassium nitrate (KNO3), and minimum germination was observed in urea. Nutrient (phosphorus, calcium, and magnesium) deficiency significantly enhanced the germination frequency with maximum increase in magnesium (Mg) deficient condition. Further, supplementation of carbon sources (glucose, fructose, and sodium acetate) and growth hormones (IAA and GA) also enhanced the germination frequency in this cyanobacterium. Therefore, it may be concluded that, those factors supporting higher germination frequency could be considered for successful production and use of this cyanobacterium in biofertilizer and other algal production technologies.

Isolation and characterization of high protein and phycocyanin producing mutants of Arthrospira platensis

Cyanobacteria are known to exhibit their efficiency in producing high concentrations of compounds of commercial value. Arthrospira is one such cyanobacterium which is considered as important source of protein (65%) and other nutrients. In present study, chemical mutagenesis using N‐methyl‐Ń‐Nitro‐nitrosoguanidine (NTG), a proven potent mutagen for cyanobacteria was used to bring stable and desirable alteration in Arthrospira platensis ARM 730. Three morphological mutants (G‐1, G‐2, and SF) were selected and characterized. The G‐1 and G‐2 were helical, more bluish in pigmentation than the wild type strain where G‐1 also showed enlarged cell size. The SF mutant was an altered straight‐filament having maximum biomass. Among three mutants, higher protein and phycocyanin contents were observed in G‐1 and G‐2 mutants whereas chlorophyll was less in these mutants as compared to wild type strain indicating change in the pigment ratio. Carotenoid content was higher in SF mutant as compared to wild type and other mutants. Variation in total sugar content was not observed in comparison to wild type strain. The analysis of amino acid spectrum of all the mutants and wild type showed significant increase in proline content. Overall, it is revealed from the results that G‐1 and G‐2 mutants showed higher biomass, phycocyanin, and protein contents in comparison to wild type which indicated their great potential to be used in food and pharmaceutical industries.

Field evaluations of agrochemical toxicity to cyanobacteria in rice field ecosystem: a review

The adverse effects of chemical nitrogen fertilizers affecting soil fertility, water pollution and native microorganisms, particularly cyanobacteria, in wetland rice cultivation have drawn global attention towards the use of alternative sources like N2-fixing cyanobacteria as a biofertilizer for sustainable rice farming. Although chemical nitrogen fertilizers are extensively used for obtaining higher rice yield, they are likely to have a deleterious effect on the growth and N2-fixation of diazotrophs, including cyanobacteria. In addition, biocides (herbicides and insecticides) are widely being used in rice cultivation for optimizing crop yield, but these chemicals also affects non-target organisms adversely. There are several reports indicating impacts of these agrochemicals on cyanobacteria, but most such studies were carried out under laboratory conditions. This article reviews information from different field evaluations on the impact of agrochemicals on cyanobacteria along with rice crop in wetland rice field ecosystem.

Sample preparation method for tissue based proteomic analysis of Azolla microphylla

The nitrogen fixing aquatic pteridophyte Azolla is used as biofertilizer for rice paddy. It is also used as poultry and cattle feed due to high protein content. However, its mass cultivation and exploitation is constrained due to the abiotic stress conditions it is exposed to. The system is interesting due to the presence of symbiotic nitrogen fixing cyanobacteria and its interaction with the carbon fixing host. Therefore these interactions have to be studied at the molecular level using advanced techniques. Proteomics is a technique which can be employed to reveal the mechanism of cross talk between the host and its symbiont as well as its response to abiotc stress. The primary step that contributes to successful proteomic analysis is standardization of sound protocols for protein extraction and sufficient yield to initiate proteomic studies using 2-dimensional electrophoresis. However, reports are not available on the protein extraction procedures in Azolla. Therefore in the present study we attempted to optimize protein extraction protocol in the whole plant, roots and the chloroplast of Azolla microphylla using phenol extraction, TCA-acetone and phosphate buffer methods. Our studies showed the efficacy of phenol extraction method in terms of maximum yield and resolution of proteins in Azolla.