Genetical studies on the heterocyst and nitrogen fixation of the blue-green alga Nostoc muscorum

Summary The short-trichome-forming, non-heterocystous and non-nitrogen-fixing (het ^– nif^–) mutant of the nitrogen-fixing blue-green alga Nostoc muscorum was isolated by N-methyl-N-nitro-N-nitrosoguanidine (NTG)-mutagenesis after penicillin enrichment technique and characterized. The mutant did not grow and fix nitrogen in combined-nitrogen-free medium while in nitrate-containing medium it grew well (K=0.112/day, G=64.27 h), although its growth was comparatively poor than the parent alga (K=0.128/day; G=56.14 h). The mutant was stable and both the het ^– and nif ^– characters reverted to wild type (het ⁺ nif⁺) with the reversion frequency of 2.62×10^-7.The het ^– nif^– mutant tolerated 0.5 g/ml of streptomycin sulphate on the agar medium and its streptomycin resistant mutant capable of growing in presence of 10g/ml of streptomycin was isolated spontaneously with a frequency of 1.45×10^-8. These streptomycin resistant isolates (het ^– nif^– str^R) resisted 100 g/ml of streptomycin sulphate on the agar medium and 200 g/ml in liquid medium. Spontaneous virus-resistant mutant of het ^– nif^– str^R was isolated with a mutation frequency of 4.02×10^-4.The data of genetic recombination experiments suggested that there is transfer of both het and nif genes to het ^– nif^– strain with the frequency of 2×10^-6 to 2×10^-5 simultaneously. There was increase in recombination frequency with increasing the incubation period. The virus-resistance marker is also transferred to the sensitive recipient.Abbreviations CFU colony forming units - C–N Chu-10 medium without combined nitrogen - C+N Chu-10 medium with 0.232 g/l calcium nitrate - G generation time - het heterocyst differentiating genes - K specific growth rate constant - MOI multiplicity of infection - nif nitrogen-fixing genes - NTG N-methyl-N-nitro-N-nitrosoguanidine - PFU plaque forming units - str ^R streptomycin resistance - str ^R streptomycin sensitive     

Alloxan: A growth accelerator for a nitrogen-fixing blue-green alga

Effect of Alloxan was studied on a nitrogen-fixing blue-green alga: Westiellopsis prolifica in pure cultures. Concentrations of Alloxan, 10 g to 50 g/ml stimulate the growth of the alga and increase the chlorophyll, carotin and phycocyanin content of the cultures.     

Studies on microbiologically influenced corrosion of SS304 by a novel manganese oxidizer,Bacillus flexus

A manganese oxidizing bacterium was isolated from the surface of steel scraps and biochemical tests and 16S rRNA sequencing analysis confirmed the isolate as Bacillus flexus. Potentiodynamic polarization curves showed ennoblement of open circuit potential, increased passive current, a lowering of breakdown potential, active re-passivation potential and enhanced cathodic current in the presence of B. flexus. Adhesion studies with B. flexus on SS304 specimens with different surface treatments demonstrated decreased adhesion on passivated and FeCl₃ treated specimens due to the removal of MnS inclusions. The present study provides evidence that surface treatment of stainless steels can reduce adhesion of this manganese oxidizing bacterium and decrease the probability of microbiologically influenced corrosion.     

Effect of temperature and arsenic on Aeromonas hydrophila growth,a modelling approach

Aeromonas hydrophila is frequently reported from arsenic affected areas. Present study was aimed to determine the effect of arsenic and temperature on growth of A. hydrophila. The bacteria were isolated from naturally infected fish from a water body in Birbhum, West-Bengal, India, which is reported to be an arsenic-free area. Arsenic concentration in natural aquatic reservoirs (e.g., pond, lake or river) varies from 0–6 mg/L. No significant change in bacterial growth was observed within this range of arsenic exposure. However, variation in temperature impacted the growth of A. hydrophila. A single dimension model was constructed using simple logistic equation. Rate parameters of the model were derived from the experimental observations. Comparison of model results and laboratory observations gives a good conformity regarding the effect of variation of arsenic concentration and temperature change on growth of this bacterium. From the analysis of this model we further get the idea that the maximum growth of A. hydrophila is supposed to be at 31.4°C in absence of arsenic, whereas at 477 mg/L arsenic concentration, the growth of the bacteria totally stops at 30°C.     

Isolation and Characterization of Arsenic-Resistant Bacteria from Contaminated Water-Bodies in West Bengal,India

Bengal Basin is known for severe arsenic contamination. In the present study, we have isolated six bacteria from the arsenic contaminated surface water of Bengal Basin. 16S rDNA sequence analysis identified them as Microbacterium oleivorans, Acinetobacter soli, Acinetobacter venetianus, Acinetobacter junii, Acinetobacter baumannii, Acinetobacter calcoaceticus. All the isolates possess arsenic accumulation potential and high molecular weight plasmid (>10 kb). PCR amplification indicated the presence of arsenic-resistance genes (arsB and aoxB) either in the genome or plasmid or in both in the isolated bacteria (except in Acinetobacter venetianus). Exposure to arsenic affected bacterial growth and induced alteration in cytoplasmic membrane integrity.     

Charge and Discharge Processes and Sodium Storage in Disodium Pyridine‐2,5‐Dicarboxylate Anode—Insights from Experiments and Theory

A combined experimental and computational study of disodium pyridine‐2,5‐dicarboxylate (Na₂PDC) is presented exploring the possibility of using it as a potential anode for organic sodium‐ion batteries. This electrode material can reversibly insert/release two Na cations per formula unit, resulting in high reversible capacity of 270 mA h g^?1 (236 mA h g^?1 after accounting for the contribution from Super P carbon) with excellent cyclability 225 mA h g^?1, with retention of 83% capacity after 100 cycles, and good rate performance with reversible capacity of 138 mA h g^?1 at a 5 C rate. The performance of disodium pyridine dicarboxylate is therefore found to be superior to that of the related and well investigated disodium terephthalate. The material shows two voltage plateaus at about 0.6 V up to Na₂₊₁PDC and then 0.4 V up to full sodiation, Na₂₊₂PDC. The first plateau is attributed to the coordination of inserted Na to nitrogen atoms with bond formation, i.e., a different mechanism from the terephthalate analog. The subsequent plateau is due to coordination to the carboxylic groups.     

Restriction analysis and quantitative estimation of methylated bases of filamentous and unicellular cyanobacterial DNAs.

The DNAs of strains of three cyanobacterial genera (Anabaena, Plectonema, and Synechococcus) were found to be partially or fully resistant to many restriction endonucleases. This could be due to the absence of specific sequences or to modifications, rendering given sequences resistant to cleavage. The latter explanation is substantiated by the content of N6-methyladenine and 5-methylcytosine in these genomes, which is high in comparison with that in other bacterial genomes. dcm- and dam-like methylases are present in the three strains (based on the restriction patterns obtained with the appropriate isoschizomeric enzymes). Their contribution to the overall content of methyladenine and methylcytosine in the genomes was calculated. Partial methylation of GATC sequences was observed in Anabaena DNA. In addition, the GATC methylation patterns might not have been random in the three cyanobacterial DNA preparations, as revealed by the appearance of discrete fragments (possibly of plasmid origin) withstanding cleavage by DpnI (which requires the presence of methyladenine in the GATC sequence).     

Effect of particulate pollution on rate of transpiration in Shorea robusta at Lalpahari forest

The effect of stone dust deposition on the rate of transpiration in Shorea robusta was studied in three principal seasons in a polluted forest in comparison to an almost non-polluted forest. The extent of particulate pollution was determined by measuring suspended particulate matter in the air and dust fall on leaf surface. Macroscopic and microscopic leaf injury symptoms were studied. Scanning electron microscopic examination of leaf surfaces revealed a number of foliar anomalies. Qualitative determination of rate of transpiration in field condition was done by ‘cobalt chloride method’. It was found that transpiration was diminished as a result of foliar dust deposition which not only caused blockage of stomatal aperture but also physical damage to the leaf surface. Thus, particulate air pollution can be considered as one of the external factors regulating the rate of transpiration in plants.     

Lysogeny in the blue-green algaNostoc muscorum

Lysogens were isolated after confluent lysis of the blue-green algaNostoc muscorum by N-1 virus and characterised. The spontaneous liberation of active virus particles in lysogens was not lost after treating them with viricidal concentration of EDTA and virus titre obtained in their cultures was >5×10³ PFU/ml. The virus adsorbed on the lysogens with a slower rate than on parent alga, although it followed the pattern of a first order reaction. The heat treatment (45°C for 14h) of the lysogens failed to induce lysis, whereas mitomycin C (1–2 g/ml) was effective in inducing lysis.List of Abbreviations EDTA ethylene diamine tetra-acetic acid - IM input multiplicity - k adsorption rate constant - k _v specific constant for virus production - MC mitomycin C - PFU plaqueforming units