Dal Lake Research Articles

Molecular Cloning and Genetic Analysis of Functional merB Gene from Indian Isolates of Escherichia coli

Studies were carried out to characterize organomercurial lyase genes from wild type mercury-resistant Escherichia coli isolates, previously collected from five geographically distinct regions of the Indian subcontinent. PCR amplification followed by DNA sequencing of amplified fragments showed three merB identical to the previously characterized mer B from E. coli pR831b that were thus considered as the same gene. The remaining two genes derived from E. coli isolates of an almost mercury-free site (Dal lake, Kashmir) and designated as pIAAD3 merB and pIAAD14 merB showed slight variation (2%) at base. However, this variation in pIAAD3 due to the absence of base "T" at 479 position results in complete frame shift and the predicted MerB-like polypeptide derived from it showed 21.53% divergent at its C terminal end from the previously characterized pR831b MerB. The expression profile of pIAAD3 merB in pQE30 and pUC18 vectors each demonstrated 22.2 kDa proteins. The induced DH5alpha E. coli cells possessing pIAAD3 merB cloned in pUC18 vector split phenyl mercuric acetate (PMA) into benzene and inorganic mercury efficiently, thus giving a clue that the expressed gene product is biologically active. The current study suggests that such genetic changes may take place in the continued absence of mercury pressure, and with such modifications, they finally break down to act as vestigial remnants. Further work is going on in our lab to exploit pIAAD3 merB for the bioremediation of mercury-polluted sites.

Mercury volatilization by R factor systems in Escherichia coli isolated from aquatic environments of India.

Ten Escherichia coli strains isolated from five different aquatic environments representing three distinct geographical regions of India showed significantly high levels of tolerance to the inorganic form of mercury, i.e., mercuric chloride (HgCl(2)). MRD14 isolated from the Dal Lake (Kashmir) could tolerate the highest concentration of HgCl(2), i.e., 55 microg/mL, and MRF1 from the flood water of the Yamuna River (Delhi) tolerated the lowest concentration, i.e., 25 microg/mL. All ten strains revealed the presence of a plasmid of approximately 24 kb, and transformation of the isolated plasmids into the mercury-sensitive competent cells of E. coli DH5alpha rendered the transformants resistant to the same concentration of mercury as the wild-type strains. Mating experiments were performed to assess the self-transmissible nature of these promiscuous plasmids. The transfer of mercury resistance from these wild-type strains to the mercury-sensitive, naladixic acid-resistant E. coli K12 (F(-) lac(+)) strain used as a recipient was observed in six of the nine strains tested. Transconjugants revealed the presence of a plasmid of approximately 24 kb. An evaluation of the mechanism of mercury resistance in the three most efficient strains (MRG12, MRD11, and MRD14) encountered in our study was determined by cold vapor atomic absorption spectroscopy (CV-AAS), and it was noted that resistance to HgCl(2) was conferred by conversion of the toxic ionic form of mercury (Hg(++)) to the nontoxic elemental form (Hg(0)) in all three strains. MRD14 volatilized mercury most efficiently.

Relationship between the persistence of mer operon sequences in Escherichia coli and their resistance to mercury.

Studies related to geographic distribution of E. coli carrying mer operon sequences were carried out on the Indian subcontinent. Out of the 80 E. coli isolates, collected from five geographically distinct regions of India, 68 were found to be resistant to one or the other heavy metal used in the study. Among these isolates, 36 were found to be resistant to the inorganic form (HgCl2) and only 5 to resist both the inorganic and organic forms of mercury. Colony hybridization studies revealed 35 isolates out of 68 to hybridize with the probe. Interestingly, some of the mercury-sensitive isolates (Hgs), especially from the Dal Lake, were found positive in hybridization studies. These findings, supported by mercury volatilization studies, indicate the presence of nonfunctional/vestigial mer sequences in the isolates collected from different environments. On the other hand, few of the mercury-resistant isolates (Hgr) from the Yamuna River did not show any sign of hybridization. Further, volatilization studies also indicated an alternate mode of resistance mechanism operating in them. The studies demonstrate that the mer operon sequences share very high homology among the E. coli isolates collected from different geographical locations, and this metal resistance may be a genetic character that arose from a common ancestral background.

A red bloom of Euglena shafiqii, a new species, in Dal Lake, Srinagar, Kashmir

A bloom of Euglena was observed at the surface of Dal Lake, Kashmir, in the last week of June, 1991. The species exhibited a circadian colour change, from green at dawn to blood-red during the day and again green at dusk. The present new species is, therefore, named Euglena shafiqii. It is distinguished from the cogenus by the structure and occurrence of Z-tubules, chromatophores, nucleus shape and by a coloured pulsating structure at the posterior end. A stress induced transformation from an elongated egg to a round shape is also peculiar. The light absorption spectra of the pigment showed λ maxima at 416, 441, 467 and 485 nm. The red bloom was found in the part of the lake basins which receives waste effluents.

Quantification of suspended solids in Dal lake, Srinagar using remote sensing technology

Indian Remote Sensing satellite (IRS)-1B, Linear Imaging Self Scanner (LISS)-II spectral digital data was analysed to determine the feasibility of quantifying the concentration of suspended solids in the surface water of inland water body, Dal lake, in Srinagar, India. The water samples collected in concurrent with IRS-1B overpass, were analysed to determine the concentration of suspended solids. The results indicate that a positive functional relationship exist between the concentration of suspended solids and the visible wave length bands 1 and 3 and near infrared band 4. It has been observed that as the concentration of suspended solids increase, the spectral response also increases. It is concluded that IRS LISS-H data can be effectively used to quantify suspended sediment concentration in the Dal lake surface water.

Dal Lake Clean-up Strategy: An Example for Others?

Dal Lake Clean-up Strategy: An Example for Others?

Occurrence of a rare euglenoid causing red-bloom in Dal Lake waters of the Kashmir Himalaya

Occurrence of a rare euglenoid causing red-bloom in Dal Lake waters of the Kashmir Himalaya

Euglenoid Red-bloom Contributing to the Environmental Pollution of Dal Lake, Kashmir Himalaya

Euglenoid Red-bloom Contributing to the Environmental Pollution of Dal Lake, Kashmir Himalaya

Impact of mechanical deweeding on Dal Lake ecosystem

The accelerated nutrient enrichment of Dal Lake, Kashmir has augmented the production of aquatic vegetation to the point where many recreational activities have been severely impaired. For providing relief from nuisance conditions mechanical deweeding was introduced in the lake in 1986. The present study assesses the impact of large scale vegetation removal on water quality, plankton population, macrophyte and fish. The concentrations of electrical conductivity, dissolved oxygen, total phosphorus and nitrate-nitrogen changed significantly immediately after deweeding. Phytoplankton species which increased after deweeding include Amphora ovalis, Cymbella cistula,Cosmarium sp.: also rotifers increased (Anuraeopsis fissa,Brachionus calyciflorus and Monostyla bulla).

Phosphorus Budget for Dal, a Himalayan Lake

AbstractThe P‐budget of Dal Lake in Kashmir is described for a 12 month period. The lake is characterized by high P‐loading (7.5 g · m−2 a−1) and had high P‐retention (retention coefficient 0.32). P‐loading in the lake showed positive and negative relations with flushing rate and P‐retention respectively. A negative relation was similarly found existing between flushing and P‐retention. The roles of various biotic and abiotic factors in the P‐budget of the lake are described.

Isolation of enteropathogenic and enterotoxigenic Escherichia coli from the Dal Lake water of Kashmir

Between July and December 1986, 18 strains of enteropathogenic serotypes of Escherichia coli were isolated from the Dal Lake water. Some of these strains were positive for colonization factor antigen. During the same period, 12 strains of heat-labile enterotoxin-producing E. coli were also isolated, all of which were positive for colonization factor antigen I or II. This indicates faecal pollution of this recreational water.

Dissolved organic carbon fluctuations in Dal Lake waters

Dissolved organic carbon (DOC) fluctuations were studied in the surface water of Dal Lake from May 1984 to April 1985, at monthly intervals. Concentration of DOC varied from 0.140 mg l−1 to 0.725 mg l−1. A minimum was recorded in May and September, while an increase was observed during December and January. The fluctuations during the observation period showed a relationship with temperature and pH.

Influence of environmental conditions on the ovarian cycle and serum chemistry of Cyprinus carpio in the Dal lake, Kashmir (India)

SUMMARY 1. The study presents adaptive and acclimatory changes observed in Cyprinus carpio communis L with respect to ovarian cycle and serum levels of electrolytes, calcium, total proteins and albumin as a consequence of wide temperature and sunshine variation in the natural environment of Dal lake in Srinagar, Kashmir (India).2. The atmospheric temperatures in Srinagar show well‐defined seasonal and diurnal variations. During the period of study, the mean monthly average temperature in summer (June‐August) was 24°C whereas in winter (December‐February) it fell to 3.6°C. The total hours of sunshine during the winter months were about half of those found in summer.3. Under local thermal and photo conditions the fish was found to spawn once a year compared to biannual spawning in tropical chmates.4. A significant decrease was found in serum sodium, potassium and chloride concentrations during the months of January and February when the mean minimum atmospheric temperatures reached −2.5°C and −l.2°C respectively.5. The serum calcium levels showed a marked increase during the period corresponding to ovarian maturity and spawning of fish.6. A significant rise in total serum protein concentration was induced by decreased environmental temperatures. Serum albumin levels were found to exhibit a sharp fall coinciding with the spawning period.

Energy content and ecological efficiency of macrophytes in Dal Lake, Kashmir

Energy content and ecological efficiency of macrophytes in Dal Lake, Kashmir

Calcium and Magnesium in Dal Lake, a High Altitude Marl Lake in Kashmir Himalayas

AbstractMonthly sampling of calcium and magnesium in the in‐ and outflows of Dal Lake revealed high concentrations of both during summer. The monthly inputs, outputs and retentions of these alkaline earths were estimated. The lake on an overall basis showed the retention of calcium but not of magnesium. This was suspected to be related and affected by variable flushing rates of water. Most of the calcium and magnesium was present in sediments and only a small fraction in the water and in macrophytes. The calcium balance is discussed in relation to the P‐balance.

The Dal Lake: Reflections on an Anthropological Consultancy in Kashmir

The Dal Lake: Reflections on an Anthropological Consultancy in Kashmir

Ecology and conservation of Dal lake, Kashmir

Studies carried out on the physicochemical characteristics of water and sediments, biological features and nutrient dynamics of Dal Lake by various investigators are reviewed. The results indicate that the direct discharge of sewage from houseboats, reduction of plant cover in the catchment area, interruptions to the flow of water, human encroachments, increase in population within the catchment area, etc, have resulted in the deterioration of water quality, prolific growth of aquatic macrophytes and siltation. Based on the data available some measures are proposed for conservation of the lake's ecosystem.

Environmental Geochemistry of Iron and Manganese in Six Himalayan Lakes

AbstractThe distribution and abundance of iron and manganese, the two important mobile metals, in an aquatic environment have been presented. These metals play an important role in the binding of nutrients and toxic elements by virtue of their high specific area in the oxide form. The concentration of Fe ranged from 1.08 to 5.2 mg/g and that of Mn from 0.27 to 2.17 mg/g. The Dal lake sediments were rich in Fe and those of the Wular lake had the lowest mean concentration of Fe. It was observed that the smaller particle size fractions had a higher metal content in comparison to large size fractions. Data on the selective extraction of Fe and Mn and their accumulation in humus material have also been given.

Interaction of Certain Heavy Metals with Lake Humic Acids

Abstract Present studies were carried out to investigate the interaction properties of humic acids with certain heavy metals—Ca, Zn, Fe and Mn by using their isotopes. Humic acids solubilized maximum portion of the calcium present (97% in case of Dal lake), of which more than 90% was present in uncomplexed form. With 59Fe results were different, solubilizing less than 30% of it and most of this solubilized portion was in complex form. Results are present in detail.

Sediment Composition, Mud‐water Interchanges and the Role of Macrophytes in Dal Lake, Kashmir

AbstractThe particulate phase of lake sediments showed a marked reduction in the concentration of N, P, K and C during late spring and summer. Larger amounts of these elements were found towards the autumn, and these higher levels were maintained through winter until early spring. The reduction in the concentration of these mineral nutrients was greatest during the growing season of the macrophytes.