Analysis of heavy metal accumulation in water and fish (Cyprinus carpio) meat from Umiam Lake in Meghalaya, India.

Water quality around the world is notably declining mainly due to human activities. Low lying water catchment areas are under considerable threat of accumulating higher pollutants including heavy metals due to natural drainage and upstream anthropogenic activities. The major group that gets affected is the aquatic animals. Bioaccumulation of toxic metals in these organisms causes potential threat to human health upon consumption as these metals tend to get biomagnified in higher trophic levels within a food web. Umiam reservoir in Meghalaya is of significant importance to the state as it is the source of hydel power generation and is a popular destination for water sport and adventure facilities. Downstream irrigation, fisheries and drinking water from the lake cater to local anthropogenic needs. In recent times due to the rising population in the capital Shillong which is situated upstream of the lake, the lake is becoming significantly polluted. With this background the present study was aimed at determining the level of heavy metals in water samples of the Umiam lake as well as in the most dominantly occurring fish species, Cyprinus carpio found in the reservoir that is widely consumed. Presence of metal ions was determined using atomic absorption spectroscopy that uses different lamps specific to a metal ion in the sample. The sequence of metal concentrations (in ppm) in the water sample was found to be Se (1.39) > Mn (0.186) > Fe (0.12) > Pb (0.06) > Cd (0.045) > Zn (0.031) > Cu (0.023) > Cr (0.016) > Ni (not detected). Comparing these values with WHO guidelines it was found that the levels of Se and Pb in the waters of the lake are significantly higher than the recommended values [for Se (0.04) and Pb (0.01) respectively]. A similar assessment conducted on fish meat collected from the lake showed high accumulation of Se (1.58 ppm) in the fish muscle. The order of occurrence of other metal ions in the fish muscle was Se>Zn>Fe>Ni>Cu>Cd~Mn>Cr>Pb revealing that if concentration of metal ions such as Zn, Fe, Cu goes up in the water, these ions would get preferentially accumulated in the fish muscle. The higher concentration of Se in the water as well as in the fish meat confirms bioaccumulation of this element. Although selenium is an essential trace element required in the human diet for synthesis of selenocysteine, high concentration in the body may lead to chronic selenium toxicity that manifest as selenosis, a condition associated with changes to the hair and nails, skin lesions and clinical neurological effects. Therefore, consumption of fish meat from the lake over a prolonged period of time may lead to biomagnification of this metal in human increasing the risk of chronic selenium toxicity. This study is important in bringing about awareness to general population about potential dangers of being exposed to continuous heavy metal toxicity, specifically those using this water from the lake for drinking.Â

Increase in intracellular proline content in Anabaena variabilis during stress conditions

The present study deals with the effects of stress due to varying concentrations of sodium chloride, cadmium, pH and exposure to pesticides on intracellular proline accumulation in Anabaena variabilis in laboratory conditions. The stresses induced due to these changes in their growth media were expressed as decrease in growth (by 40% at pH 5; 30% at 50 mM NaCl; 80% at 50 ?M endosulphan and 55% at 10 ?M CdSO4) as measured in terms of chlorophyll a concentrations in the test organism. Low pH (5, 6) had stronger negative effect on growththan increasing alkaline pH. The cyanobacterium showed varying degree of susceptibility to increasing salt, cadmium and endosulphan concentrations. Under all these altered conditions, their intracellular proline concentration was found to increase linearly in the test organism with increase in its amount of stress inducing substances in its vicinity. Proline appears to be a stress provoked substance in A. variabilis. However, there seemed to be a breakdown in the proline synthesis mechanism when concentrations of such compounds reached toxic proportions

Nostoc cyanobiont in the Cyanolichen, Sticta weigelii of Eastern Himalayan Region: Isolation, Physiological and Biochemical Characterization

A cyanobacterium identified as Nostoc sp. was isolated from the cyanolichen, Sticta weigelii (Ach.) Vainio collected from tree barks in the state of Meghalaya and its various physiological and biochemical characters were evaluated. When the lichen thalli were incubated in liquid medium, the Nostoc colonies from these thalli appeared initially in distinct sacs that released individual long heterocystous filaments into the liquid medium upon sub-culturing. The well spaced heterocystsin the filaments had a frequency of 7-8%. Chlorophyll a concentration of the cyanobacterium was higher in comparison to many other Nostoc species isolated from soil and water from the same region. Its photosynthetic activity was 519.24±0.7 nmol O2 evolved µg-1 chl a h-1 whereas respiration was 286.35±0.5 nmol O2 consumed µg-1 chl a h-1. Enzyme assays reflected nitrogenase activity of 6.98 nmol C2H4 produced µg-1 chl a h-1 and GS transferase activity of 712±3.0 nmol γ-glutamyl hydroxymate formed min-1 mg-1 protein. Nitrate reductase activity was substrate inducible. Ammonium uptake was biphasic in nature and glutamine uptake was energy dependent

Significance of cyanobacterial diversity in different ecological conditions of Meghalaya, India

The present study deals with preliminary investigation of cyanobacterial diversity in Meghalaya. A total of 75 samples were collected from 10 different ecosystems and analyzed. 65 strains of cyanobacteria isolated under 11 genera include Nostoc, Anabaena, Calothrix, Cylindrospermum, Gleocapsa, Fischerella, Plectonema, Tolypothrix, Stigonema, Loriella and Westiellopsis. Nostoc was most abundant. Diversity analysis indicated maximum Shannon’s diversity index (H) in Mawlai. Highest Simpson’s diversity index was seen in Sung Valley (0.75). Both Shannon’s and Simpson’s diversity indices were lowest in Mairang. Richness was highest in Sung valley and Syntuksiar with both the sites supporting 17 strains each. Although, highest diversity was recorded from Mawlai, richness recorded at this site was only 11 strains thereby indicating richness need not be a function of diversity in this region. This study revealed the cyanobacterial strains, which can withstand acidic pH and prevail in the region. A study on colonization also identified some potential biofertilizer strains from the region such as Nostoc punctiforme, Nostoc muscurum and Anabaena azollae that could be effective in acidic crop fields

Response and Tolerance of Cyanobacterial Exopolysaccharides to Rice Field Herbicide 2,4-D

This study aimed to check how herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) affects the production of EPS and its composition, growth, and biomass, as well as morphology in a cyanobacterial species isolated from a rice field in Meghalaya, India. Compared to the control cells, the growth of the organism measured in terms of chlorophyll concentration increased after being exposed to 10 and 20 ppm 2,4-D. However, cultures treated with 30 and 40 ppm experienced a decrease in their growth. Likewise, the biomass content of the organism experienced a minuscule increase in content upon exposure to 10 and 20 ppm 2,4-D but was compromised upon exposure to higher doses. When exposed to 10 ppm, the total EPS content, which includes the RPS and CPS content, showed a substantial increase. Maximum EPS production was seen at 20 ppm 2,4-D. However, exposure to 30 and 40 ppm 2,4-D, EPS production in the organism experienced a significant reduction, respectively. All components of EPS, such as uronic acid, neutral sugar, and proteins, individually showed an increase in 10 and 20 ppm 2, 4-D. A similar trend was seen in the organism’s bio-flocculating activity, which increased when exposed to 10 and 20 ppm, respectively. However, this activity in cells exposed to 30 and 40 ppm 2,4-D was severely reduced. Not only the content of EPS but the rate of EPS production was also enhanced in lower concentrations of 2,4-D. Although exposure to 30 ppm 2,4-D, the rate of EPS production was not significantly compromised, 40 ppm exposure adversely affected the rate of EPS production. Furthermore, visualization using scanning electron microscopy revealed the morphological changes induced by the herbicide 2,4-D

Entrapped cyanobacteria: Implications for biotechnology

209-215Immobilized cyanobacteria behaved like spores under adverse conditions. Air dried immobilized cyanobacteria stored under open conditions of light, temperature, air and dust of all seasons retained the ability to regenerate active colonies at least for three years. Upon restoration to liquid media, these regenerated cyanobacterial colonies showed growth and nitrogen fixation comparable to their free-living counterparts by second generation. Air-drying shrinked the gel beads to the size of the mustard seeds and hence, a large amount of such beads could be stored in a small space. This opens up the possibility of convenient storage and transportation of desirable cyanobacterial strains for various purposes including using them as inoculum in crop fields and in poor quality soil to increase the fixed nitrogen content

Biocontrol of Pythium aphanidermatum causing soft rot in ginger with biosurfactant produced by a rhizospheric Bacillus species: Biocontrol of Pythium aphanidermatum with biosurfactant

Plant growth-promoting rhizobacteria benefit plants by producing phytohormones and acquiring vital nutrients from soil. They also form a shield against potential phytopathogens with the production of antimicrobial compounds such as bacteriocin, biosurfactants etc. In the present study, among various rhizobacteria isolated from ginger rhizosphere, the isolate identified as Bacillus altitudinis VS7 that showed a potent biosurfactant producing ability in the preliminary tests was selected for the further study. Compositional analyses indicated that the biosurfactant produced by VS7 was a surfactin like compound, a cyclic lipopeptide. In both microtitre plate and mycelium growth inhibition studies, the biosurfactant showed dose dependent antagonistic activities against Pythium aphanidermatum that causes soft rot in ginger. Although there are reports of biocontrol activity of various rhizobacteria against soft rot in ginger, this is the firstinformation regarding biocontrol activity of a biosurfactant produced by the rhizobacterium B. altitudinis VS7 against P. aphanidermatum

An Efficient Protocol for Long-Term Preservation of Cyanobacteria

A simple modification in preparation of nutrient agar meant for agar slants resulted in a convenient and efficient matrix for long-term cyanobacterial preservation. In the modified protocol, agar concentration was increased and cyanobacterial cells were mixed rapidly in the molten agar before solidification. Solidified mixture was cut into cubes and air dried. The resulting agar flakes were stored in the dark. Periodically some flakes were inoculated in fresh medium to study regeneration of viable filaments in order to access the efficiency of the method in preserving cyanobacteria in dehydrated form. Possible outer contamination could be removed by washing the agar flakes in 1% sodium hypochlorite for one minute prior to their inoculation in fresh medium. The percentage of agar used and amount of cyanobacterial cells entrapped were the factors that influenced the period of preservation. A comparison of some biochemical and physiological characters in six regenerated cyanobacterial strains to their free-living counterparts showed that the dried agar flakes were completely reliable as preserving material for at least a period of three years. During this period the entrapped cyanobacterial cells did not need further maintenance. This process of maintaining cyanobacteria is extremely convenient as it reduces (1) input of chemicals and manpower required for maintaining cyanobacteria in batches (2) possible cross-contamination among various cyanobacteria maintained in liquid batch cultures (3) use of glassware and (4) storage space. In addition, the cells could be maintained in a near dormant state, and that minimized the chances of alterations in their native characters