Arsenic tolerance of cyanobacterial strains with potential use in biotechnology / Tolerancia a arsénico de cianobacterias con usos biotecnológicos

The arsenic content of various water bodies in Argentina is higher than the acceptable levels for human and animal uses. Cyanobacteria are widely distributed in aquatic environments and can bioaccumulate arsenic (As). This study presents the response of indigenous cyanobacteria to As(III) and As(V), including the species Tolypothrix tenuis, Nostoc muscorum and Nostoc minutum, previously used with biotechnological purposes. As(III) resulted more toxic than As(V) in all cases, causing cell death in the range of 5-20 mg/l. T. tenuis growth was sensitive to As(V) with lethal inhibition at 625 mg/l, whereas the Noctoc species were stimulated. EC50 values found were 73.34 mg/l for N. muscorum and 989.3 mg/l for N. minutum. Batch cultures of N. minutum showed improvements in both growth parameters and photosynthetic pigment content in the presence of 1,000 mg/l As(V). Increases of 66.7%, 75.5%, 40% and 20.7% in cell productivity, chlorophyll a, total carotenoids and C-phycocyanin respectively were observed, reaching a bioaccumulated arsenic value of 37.4 μg/g at the stationary growth phase.

El contenido de arsénico de diversos cuerpos de agua de Argentina es superior a los niveles aceptados para consumo humano y animal. Las cianobacterias están ampliamente distribuidas en los ambientes acuáticos y pueden bioacumular As. Este estudio presenta la respuesta de cianobacterias autóctonas a As(III) y As(V), incluyendo las especies Tolypothrix tenuis, Nostoc muscorum y Nostoc minutum utilizadas previamente con fines biotecnológicos. As(III) resultó más tóxico que As(V) en todos los casos, causando muerte celular en el rango de 5-20 mg/l. El crecimiento de T. tenuis fue sensible a As(V) con inhibición letal a 625 mg/l. Sin embargo, las especies de Noctoc resultaron estimuladas. Los valores de EC50 encontrados fueron de 73,34 mg/l para N. muscorum y 989,3 mg/l para N. minutum. Los cultivos batch de N. minutum mostraron mejoras en los parámetros de crecimiento y en el contenido de pigmentos fotosintéticos en presencia de 1000 mg/l As(V). Los incrementos observados en productividad celular, contenido de clorofila a, carotenoides totales y C-ficocianina fueron de 66,7 %; 75,5 %; 40 % y 20,7 % respectivamente, alcanzando un valor de arsénico bioacumulado de 37,4 μg/g en la fase estacionaria.

Iron mediated regulation of growth and siderophore production in a diazotrophic cyanobacterium Anabaena cylindrica.

Iron mediated regulation of growth and siderophore production has been studied in a diazotrophic cyanobacterium Anabaena cylindrica. Iron-starved cells of A. cylindrica exhibited reduced growth (30%) when the cells were growing under N2-fixing conditions. In contrast, N03-, NO2-, NH4' and urea grown cells exhibited almost 50% reduction in their growth in the absence of iron as compared to their respective counterparts cultured in the presence of iron. However, at 60 microM of iron, A. cylindrica cells exhibited almost equal growth regardless of the nitrogen source available. Siderophore production in A. cylindrica was started after day 2nd of the cell growth and attained its optimal level on day 5th when the cells were at their mid-log phase. No siderophore production was, however, recorded on day 2nd at all the concentrations of iron tested. The production of siderophore in A. cylindrica further increased with increase in iron concentration and attained its optimum level on day 5th at 60 microM iron. A. cylindrica cells took at least 3 days for initiation of siderophore production and produced about 60% siderophore on day 5th even under iron-starved condition. A. cylindrica produced dihydroxamate type of siderophore.

Interactive effect of metal ions over exponential growth period of microalgal cells.

The interactive effect of metal ions namely chromium and iron has been studied under controlled conditions on the diazotropic cyanobacterium Hapalosiphon stuhlmannii and the photosynthetic green alga Scenedesmus quadricauda over the exponential growth period of the cells. The work describes by employing an exponential cell growth model, the effect of metal ions both individually and in combination, on the physiological and biochemical characteristics e.g. dry weight, chlorophylls, carotenoid and protein content of the cells over the concentration range of 0.1-3.0:0.2-16.0 microg/ml of Cr:Fe. The results reveal that the interactive effect on the dry weight, chlorophyll and protein content of both the algal cells was antagonistic at the bimetallic concentrations of 0.1:16.0, 3.0:0.2 and 3.0:16.0 microg/ml but the interaction on the protein content of both the cells was synergistic at 0.1:0.2 microg/ml of Cr:Fe. Further the degree of antagonism on dry weight was higher in H. stuhlmannii than in S. quadricauda. The degree of antagonism varied with the bimetallic concentrations and was generally lower at the higher metal concentrations. The antagonistic behavior was considered to be due to adsorption of one of the metals hindering the sorption of the other and the synergistic effect, due to adsorption of one enhancing the permeability to the other metal. The varied interactions were possibly due to the formation of metal complexes with the microalgal exudes.

Effect of phytohormones on the growth dynamics and macromolecular contents of two extreme halophilic Cyanobacteria (Phormidium sps).

Two non-heterocystous, filamentous solar saltern extreme halophilic cyanobacteria viz., Phormidium tenue and Phormidium fragile were allowed to grow in different concentrations of phytohormones. Among the phytohormones, Indole-3 acetic acid and Indole-3-butyric acid at 0. l ppm concentration enhanced the growth, pigments and carbohydrate content in P. fragile. The phycobiliprotein production was found higher at 0. l ppm concentration of Indole-3-acetic acid in P. tenue, whereas Indole-3-butyric acid at 50 ppm and 0. 1 ppm concentrations proved to be inhibitory in the protein and carbohydrate contents in P. tenue.

Effect of glyphosate toxicity on growth, pigment and alkaline phosphatase activity in cyanobacterium Anabaena doliolum: a role of inorganic phosphate in glyphosate tolerance.

Response of glyphosate toxicity on photoautotrophic cyanobacterium A. doliolum and its mutant strain was investigated. Chlorophyll a content of both the wild type and mutant strain in the presence of glyphosate (N-phosphonomethyl glycine) initially showed an increasing trend when supplemented with Pi and a declining tendency under the Pi-starved condition. The results suggested that both the wild type and mutant strains were more sensitive to glyphosate in the absence of phosphate. Alkaline phosphatase activity of wild type strain in the presence of Pi, enhanced in response to addition of glyphosate (40 microg/ml), but the activity remained unaltered by addition of glyphosate in the Pi-starved cells, whereas the alkaline phosphatase activity in the mutant strain under both Pi-starved as well as unstarved conditions was stimulated (approximately 5.4 and 3.1-fold, respectively) by addition of glyphosate. The results on alkaline phosphatase activity indicated a glyphosate-induced depletion in the phosphate content of the cells, particularly in the mutant strain, as evident from the stimulated activity of alkaline phosphatase. It is suggested that enzyme activity in the Pi-starved wild type cells may not be influenced any further by glyphosate, as cellular phosphate reserve might not be available for further depletion.

Pigment analysis and ammonia excretion in herbicide tolerant cyanobacteria.

Isolation of cyanobacteria was attempted from herbicide applied rice soils. The predominant genera were Westiellopsis followed by Anabaena, Nostoc and Oscillatoria. The herbicide tolerance was further tested by growing the cyanobacterial cultures in BG-11 medium supplemented with varying concentrations of the commonly used rice herbicide, viz butachlor under in vitro condition. The chlorophyll-a, phycobiliproteins and ammonia excretion were assessed at periodic intervals. Westiellopsis showed the maximum tolerance followed by Anabaena, Nostoc and Oscillatoria.

Role of garlic (Allium sativum L.) in human and plant diseases.

A resurgence of interest in garlic due to recent revelations of its beneficial effects in the treatment of various human and plant diseases and also due to validation of claims made in traditional systems of medicine has resulted a plethora of publications on different aspects of garlic in recent years. Chemical constituents of garlic and their variations on the methods of isolation have been discussed in the present review. Effect of garlic and its constituents against various human and plant pathogenic and saprophytic microorganisms has also been reviewed.

Tolerance of Oscillatoria isolates to agrochemicals and pyrethroid components.

Four isolates of Oscillatoria sp from an Indian paddy field have been tested for their tolerance to agrochemicals and pyrethroid components. The isolates possessed considerable tolerance to agrochemicals and reduced toxicity of pyrethroid components towards fish.

Preliminary study on the impact of preaziquantel on phormidium fragile

This study was conducted to evaluate the toxic effects of increasing concentrations of antischistosomal drug, Praziquantel on growth, pigmentation, enzyme activities, protein and nucleic acids contents of a common cyanobacterium, Phormidium fragile. The statistical analysis revealed that dry biomass yield, chlorophyll a and carotenoids decreased as the drug concentration in the test media increased. On the other hand, the different concentrations of the drug had a stimulatory effect on the protein accumulation as well as the activities of nitrate reductase, GOT, GPT and malate dehydrogenase. Small doses of the drug increased the accumulation of RNA, DNA, phycocyanin and allophycocyanin, while the higher doses suppressed their contents. Phycocyanin seemed to be hardly affected by the addition of the chiral drug

Cobalt-induced inhibition of growth in cyanobacteria Anabaena doliolum and Anacystis nidulans: interaction with sulphur containing amino acids.

Cobalt, above 1 microM concentration was growth inhibitory for both A. doliolum and A. nidulans. Its toxicity was mitigated by sulphur containing amino acids (cystine and cysteine), however, methionine could not mitigate the cobalt toxicity at all.

Characteristics of the methylammonium/ammonium transport systems of the nitrogen-fixing cyanobacterium Anabaena 7120 (ATCC 27893).

NH4(+)-transport in Anabaena 7120 was studied using the NH4+ analogue, 14CH3NH3+. At pH 7, two energy-dependent NH4(+)-transport systems were detected in both N2- and NO3(-)-grown cells, but none in NH4(+)-grown cells. Both transport systems showed a low and a high affinity mode of operation depending on the substrate concentration. One of the transport systems showed Km values of 8 microM (Vmax = 1 nmole min-1mg-1protein) and 80 microM (Vmax = 7 nmole min-1mg-1protein), and was insensitive to L-methionine-DL-sulphoximine, a glutamate analogue and irreversible inhibitor of glutamine synthetase. The other transport system showed Km values of 2.5 microM (Vmax = 0.1 nmole min-1mg-1protein) and 70 microM (Vmax = 0.7 nmole min-1mg-1protein), and was sensitive to L-methionine-DL-sulphoximine. Intracellular accumulation of free 14CH3NH3+ showed a biphasic pattern in response to variation in external 14CH3NH3+ concentrations. A maximum intracellular concentration of 2.5 mM and 7.5 mM was reached in the external 14CH3NH3+ concentration range of 1-50 microM and 1-500 microM, respectively. At pH 9, an energy-independent diffusion of 14CH3NH2 leading to a higher intracellular accumulation and assimilation rate, than that at pH 7, was observed.