Transcriptional specificity after mycobacteriophage I3 infection

Transcriptional regulation following mycobacteriophage I3 infection has been investigated. For this purpose, RNA polymerase mutants (rif) of host bacterium, Mycobacterium smegmatis have been isolated and characterised. Phage growth inrifs and rifr cells in presence of rifampicin revealed the involvement of host RNA polymerase in phage genome transcription. This was confirmed by studies onin vivo RNA synthesis as well as by direct RNA polymerase assay after phage infection. Significant stimulation in RNA polymerase activity was seen following phage infection. The maximal levels were attained in about 60 min post infection and maintained throughout the phage development period. The stimulation of polymerase activity was most pronounced when the phage DNA was used as the template. RNA polymerases from uninfected and phage-infected Mycobacterium smegmatis have been purified to homogeniety. The enzyme purification was accomplished by a rapid procedure utilising affinity chromatography on rifampicin-Sepharose columns. Subunit structure analysis of the purified RNA polymerase from uninfected and phage-infected cells showed the presence of α ,β , β ' and σ subunits similar to the other prokaryotic RNA polymerases. In addition, a polypeptide of 79, 000 daltons was associated with the enzyme after phage infection. The enzymes differed in their properties with respect to template specificity. Phage 13 DNA was the preferred template for the modified RNA polymerase isolated from infected cells which may account for the transcriptional switch required for phage development

Requirement for calcium ions in mycobacteriophage I3 DNA injection and propagation

Ca2+ ions are absolutely necessary for the propagation of mycobacteriophage I3 in synthetic medium. These ions are required for successful infection of the host and during the entire span of the intracellular development of the phage. A direct assay of the phage DNA injection using 32[p] labelled phage, shows that Ca2+ ions are necessary for the injection process. The injection itself is a slow process and takes 15 min to complete at 37°. The bacteria infected in presence of Ca2+ tend to abort if the ions are subsequently withdrawn from the growth medium. The effect of calcium withdrawal is maximally felt during the early part of the latent period; however, later supplementation of Ca2+ ions salvage phage production and the mature phage progeny appear after a delayed interval, proportional to the time of addition of Ca2+

Stimulation of valyl- and isoleucyl-tRNA synthetase reactions by polyamines

The aminoacylation of tRNA catalysed by valyl-tRNA synthetase (EC 6.1.1.9) and isoleucyl-tRNA synthetase (EC 6.1.1.5) from Mycobacterium smegmatis is dependent on the presence of divalent metal ions. Polyamines alone, in the absence of metal ions, do not bring about aminoacylation. In the presence of suboptimal concentrations of Mg2+, polyamines significantly stimulate the reaction. Of the cations tested, only Mn2+, Co2+ and Ca2+ can partially substitute for Mg2+ in aminoacylation, and spermine stimulates aminoacylation in the presence of these cations also. At neutral pH, spermine deacylates nonenzymatically aminoacyl tRNA. AMP and pyrophosphate-dependent enzymatic deacylation of aminoacyltRNA (reverse reaction) is also stimulated by spermine. The inhibitory effect of high concentration of KCl on aminoacylation is counteracted, by spermine. The low level of activity between pH 8.5-9.0 at 1.2 mM Mg2+ is restored to normal level on the addition of spermine. The inhibitory effect of high pH on aminoacylation in the presence of low concentration of Mg2+ is also prevntedvby spemine

Primary production

Studies on primary pruuuciion oj ine Indian Seas in general and adjacent ecosystems such as estuaries, mangroves, mud banks and coastal environments in particular are briefly discussed, in the light oJ the data collected over the years by various Expeditions and also by the investigations conducted in localised regions. The results indicated that the general trend of primary production vary both in space and time and also a seaward decrease in the production. The factors affecting and favouring the primary production of the Indian Seas is also presented. The annual production rates of west coast and east coast andpotential estimates of resources derivedfrom primary production is also discussed. The annual carbon production for the EEZ of India has been com^puted as 283 million tonnes and potential harvestable resources available in this region derived as 5.5 million tonnes, based on primary production. Future investigations on productivity through chlorophyll analysis arc also projected

Phytoplankton

Investigations on phytoplankton of the Indian Seas has assumed great significance during the last 5 decades. As these microscopic organisms fluctuated in response to climatic changes, water movements, seasonal variations, nutrient content of the water etc. they form an important and convenient link in the assessment of the stock of potential resources. The shelf and oceanic waters of the Indian seas show fluctuations in the standing crop of phytoplankton due to the effect of two monsoons. Available data indicated that the waters along the west coast of India are more fertile than that along the east coast mainly due to upwelling and other favourable factors conducive to phytoplankton growth. Some of the ecological factors contributing to the pattern of production of phytoplankton are also briefly discussed

Influence of Thermal Effluents on the Growth Characteristics of Phytoplankton in the Waters of Tuticorin Bay

The paper reports the results of investigations conducted in 1990, on the physico-chemical aspects of Tuticorin Bay waters in relation to the abundance of phytoplankton. Selected species of phytoplankton were experimental1y cultured to study the influence of thermal effluents. For this purpose cultures ,vere raised in media collected from 4 stations. showing different extents of pollution. Four species of nannoplankton, namely. l sochrysis galbana (Haptophyceae), Dicrateria inornata (chrysophyceae), Tetraselmis gracilis (Chloro-phyceae) and Chaetoceros calcitrans (Bacillariophyceae) were grown in the water samples collected from selected stations. The experiments showed stimulatory trend of growth for the first 7-8 days and gradual inhibitory effect on the multiplication in subsequent days. Among them, the phytoflagellates (Jsochrysis, Dicrateria and Tetraselmis)showed good growth in the samples of media collected from locations near to the pollution source. The rate of production of both Tetraselmis and Dicrateria, which are known to exist in the polluted waters, indicated enhanced growth in the Bay waters. The growth of the diatom, Chaetoceros has been found to be uniform except in the sample collected from the point nearest to the source of pollution. Though the long-term effects of these samples have not been studied, the experiments revealed the possible effects of.thermal effiuents on the phytoplankton population in the waters of Tuticorin Bay

Quantitative ecology of phytoplankton in the Cochin backwater

A one-year study on the standing crop in terms of chlorophylls, primary production and total-cell counts of four station grids has shown that there were regional and seasonal variations in the magnitude of phytoplankton production in the Cochin backwater. Statistically treated using a microcomputor, a multiple regression relationship has been established between parameters within stations. But th<^ Correlation coefBclent and Standard Regression coefficient have revealed that the plankton production and the related parameters at all the stations were independent of each other and the parameters varied from station to station. Probable reasons are briefly discussed

Polymer Translocation in Crowded Environments

We study the effect of the crowded nature of the cellular cytoplasm on the translocation of a polymer through a pore in a membrane. By systematically treating the entropic penalty due to crowding, we show that the translocation dynamics are significantly altered, leading to novel scaling behaviors of the translocation time in terms of chain length. We also observe new and qualitatively different translocation regimes depending upon the extent of crowding, transmembrane chemical potential asymmetry, and polymer length.Comment: 4 figure

Marine pollution - its effects on living resources with special reference to aquaculture

Due to large scale industrialisation and indiscriminate discharge of effluents with high BOD, toxic chemicals and particulate matter reach the aquatic environment, either directly or indirectly. Enrichment of the coastal waters through nutrients and minerals lead to immediate and long term effects on the biota and fishery resources causing severe eutrophication or mass mortality. Among a large variety of pollutants which reach the aquatic environment, the domestic sewage, agricultural pesticides, industrial wastes, oil and oil dispersants, radioactive wastes and the polluted water from the coconut retting zones causes deleterious effects in the inshore and fish fanning areas

Characterization of a local isolate of Bombyx mori nuclear polyhedrosis virus

Polyhedral bodies of Bombyx mori nuclear polyhedrosis virus, BmNPV (BGL) isolated from infected silkworms around Bangalore were propagated either in the cultured B. mori cell line, BmN or through infection of larvae. Electron microscopic (EM) observations of the polyhedra revealed an average length of 2 μm and a height of 0.5 μm. The purified polyhedra derived virions (PDV) showed several bands in sucrose gradient centrifugation, indicating the multiple nucleocapsid nature of BmNPV. Electron microscopic studies of PDV revealed a cylindrical, rod-shaped nucleocapsid with an average length of 300 nm and a diameter of 35 nm. The genomic DNA from the PDV was characterized by extensive restriction analysis and the genome size was estimated to be 132 kb. The restriction pattern of BmNPV (BGL) resembled that of the prototype strain BmNPV-T3. Distinct differences due to polymorphic sites for restriction enzyme HindIII were apparent between BmNPV (BGL) and the virus isolated from a different part of Karnataka (Dharwad area), BmNPV (DHR)