H. Lee

Effect of aluminum and pH on the growth of Anacystis nidulans

Anacystis nidulans is a typically rod-shaped unicellular cyanobacterium. It is an obligate photoautograph whose photosynthetic apparatus is very is very similar to eukaryotic chloroplasts in functional and molecular aspects. Of the toxic materials discharged, trace and heavy metals are of major concern. Metals are introduced into the environment by industrial agricultural and municipal wastes as well as by natural runoff. Metals emitted into the environment from combustion can also find their way into waterways. Aluminum is one of the most abundant metals in the earths crust. It is reported that water draining from rock strata associated with coal seams may contain acid salts of aluminum, iron and manganese. The toxic effects of aluminum on plant growth have long been known. Several concentrations of aluminum, as well as various pH values were studied, to determine the extent to which some pollutants will effect the growth of Anacystis nidulans. Since reports have indicated that EDTA influences the effect of many metals, studies were performed with and without EDTA.

Inhibition of Herpes Simplex Virus type 1 with the modified green tea polyphenol palmitoyl-epigallocatechin gallate

Green tea polyphenol epigallocatechin gallate (EGCG) is a strong antioxidant that has previously been shown to reduce the number of plaques in HIV-infected cultured cells. Modified EGCG, palmitoyl-EGCG (p-EGCG), is of interest as a topical antiviral agent for herpes simplex virus (HSV-1) infections. This study evaluated the effect of p-EGCG on HSV-infected Vero cells. Results of cell viability and cell proliferation assays indicate that p-EGCG is not toxic to cultured Vero cells and show that modification of the green tea polyphenol epigallocatechin gallate (EGCG) with palmitate increases the effectiveness of EGCG as an antiviral agent. Furthermore, p-EGCG is a more potent inhibitor of herpes simplex virus 1 (HSV-1) than EGCG and can be topically applied to skin, one of the primary tissues infected by HSV. Viral binding assay, plaque forming assay, PCR, real-time PCR, and fluorescence microscopy were used to demonstrate that p-EGCG concentrations of 50 μM and higher block the production of infectious HSV-1 particles. p-EGCG was found to inhibit HSV-1 adsorption to Vero cells. Thus, p-EGCG may provide a novel treatment for HSV-1 infections.

Effects of nickel and pH on the growth of Chlorella vulgaris

Chlorella is a spherical, unicellular, eukaryotic green algae. It is an obligate photoautotrophy containing chlorophylls a and b. It is a frequent symbiont of many other organisms such as paramecium, hydra and sponges and is important in fresh and marine environments, as well as in the soil. For these reasons, it has been suggested that Chlorella be used for metabolic studies as an indicator of environmental pollution. Ability of microorganisms to grow in environments containing high levels of toxic metals is frequently due to the organisms` capacity for adsorption of these ions and the role that they may play as essential cofactors in metalloenzymes as is the case for nickel. The purpose of this study was to determine the effect of nickel on the growth of Chlorella vulgaris. 19 refs., 4 figs., 1 tab.

Effects of Cobalt and pH on the Growth of Chlamydomonas reinhardtii

Chlamvdomonas reinhardtii is a typical unicellular, spherlcal, green algae containing a large chloroplast, two anterior flagella, and chlorophylls a and b. It is an important organism in several diverse environments, mainly fresh water and soil (Bold & Wynne, 1985). As producers, they have great importance in food chains and the accumulation of heavy metals at various trophic levels of algae, higher plants and animals might affect man ( Kelly, 1988). The study of organisms, such as Chlamvdomonas, can provide an indication of the toxic effects of a pollutant on general metabolic processes, as well as acting as an indicator of the level of pollution in the environment. Algae, more than other groups of organisms, may yield information from experimental simulations that have predictive value for field situations. Organisms at higher trophic levels are more complex and not as easily studied (Stokes, 1984). Previous studies have indicated that dependent upon the organism and the test system employed ranging from prokaryotes to eukaryotes, different sensitivities to metal toxicity will be demonstrated (Codina et al., 1993).

Effect of lead and cobalt on the growth of Anacystis nidulans

Lead is toxic to most living things at high exposure and there is no demonstrated biological need. The limit for lead in drinking water as set by US Public Health Service if 0.05 ppm. Previous reports have indicated that algae are not as sensitive to lead as many other organisms. Chelating agents, such as EDTA (Ethylene Diamine Tetraacetic Acid) are able to reduce the toxicity of lead and other metals. In natural habitats this may be due to the effect of reducing agents and amino acids. PH value has been reported to influence the effect of metals. Cobalt is a relatively rare metal produced primarily as a by-product of other metals, chiefly copper. It is used in high temperature alloys and in permanent magnets. Its salts are used in paint dryers as catalysts, and in the production of pigments. Cobalt has been shown to inhibit chlorophyll biosynthesis and the site inhibition by cobalt has been identified. In this study the effect of lead and cobalt on the growth of Anacystis nidulans will be studied.

Antiviral activity of theaflavin digallate against herpes simplex virus type 1

Abstract Tea is the second most consumed drink in the world. The beneficial effects of tea have been mostly attributed to its catechin content. Black tea is derived from the leaves of Camellia sinensis plant, and it is rich in theaflavin polyphenols, in particular theaflavin (TF1), theaflavin-3-monogallate (TF2A), theaflavin-3′-monogallate (TF2B), and theaflavin-3,3′-digallate (TF3). Vero and A549 cells were used to evaluate the effect of purified individual black tea theaflavins as anti-herpes simplex virus 1 agents. With the rise of HSV resistant strains, there is a critical need to develop novel antiherpesviral treatments. Results of the cytotoxicity assay tested by MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium] showed that TF1, TF2, and TF3 are not toxic to Vero and A549 cells at a concentration up to 75μM. The antiviral activity of the individual theaflavins was tested by plaque reduction assay, MTS assay, flow cytometric analysis and confocal microscopy observations. The results showed that TF1, TF2, and TF3 exhibit potent, dose-dependent anti-HSV-1 effect, with TF3 being the most efficient in both Vero and A549 cells. A concentration of 50μM TF3 and above was sufficient to inhibit >99% of the production of HSV-1 viral particles. The anti-HSV-1 effect of TF3 is due to a direct effect on the virions, and treating Vero or A549 cells with TF3 for 1h prior to infection, or treating the cells at different times post infection does not inhibit HSV-1 production. TF3 is stable at vaginal pH, indicating its potential to be a promising natural and affordable remedy against herpes simplex viral infections.

Induction of temperate cyanophage AS-1 by heavy metal – copper

BackgroundIt has been reported that some marine cyanophage are temperate and can be induced from a lysogenic phase to a lytic phase by different agents such as heavy metals. However, to date no significant reports have focused on the temperate nature of freshwater cyanophage/cyanobacteria. Previous experiments with cyanophage AS-1 and cyanobacteria Anacystis nidulans have provided some evidence that AS-1 may have a lysogenic life cycle in addition to the characterized lytic cycle.ResultsIn this study, the possible temperate A. nidulans was treated with different concentrations of heavy metal-copper. CuSO4 with concentrations of 3.1 × 10-3 M, 3.1 × 10-4 M, 3.1 × 10-5 M and 3.1 × 10-6 M were used to detect the induction of AS-1 from A. nidulans. The population of the host, unicellular cyanobacteria Anacystis nidulans, was monitored by direct count and turbidity while the amount of virus produced was derived from plaque forming units (PFU) by a direct plating method. The ratio of AS-1 release from A. nidulans was also determined. From these results it appears that AS-1 lysogenic phage can be induced by copper at concentrations from 3.1 × 10-6 M to 3.1 × 10-4 M. Maximal phage induction occurred at 6 hours after addition of copper, with an optimal concentration of 3.1 × 10-6 M.ConclusionCu2+ is a significant inducer for lysogenic cyanobacterial cells and consequently would be a potential control agent in the cyanobacteria population in fresh water ecosystems.

Temperature-induced activation of freshwater Cyanophage AS-1 prophage

Synechococcus sp. IU 625 is one of the freshwater cyanobacteria responsible for harmful algal blooms (HAB). Cyanophages can serve as natural control agents and may be responsible for algal bloom prevention and disappearance. Cyanophage AS-1, which infects Synechococcus sp. IU 625 (Anacystis nidulans) and Synechococcus cedrorum, plays an important role in the environment, significantly altering the numbers of its hosts. Since seasonal (temperature-dependent) lytic induction of cyanobacterial prophage has been proposed to affect seawater algal blooms, we investigated if the AS-1 lytic cycle could be induced by a shift to high temperature. Our hypothesis was confirmed, as more phages were released at 35°C than at 24°C, with maximal induction observed with a shift from 24 to 35°C. Furthermore, transmission electron microscopy (TEM) images provide direct evidence of lysogenic to lytic conversion with temperature shift. Thus, temperature is an important inducer for AS-1 conversion from lysogenic to lytic cycle and could have applications in terms of modulating cyanobacterial populations in freshwater aquatic environments. The study gives insight into the effect of climate change on the interaction between cyanophage and cyanobacteria in freshwater ecosystems.

Adaption of Synechococcus sp. IU 625 to growth in the presence of mercuric chloride

Resistance to heavy metals is important for the survival of bacteria in contaminated environments. In this study, we show that the unicellular cyanobacterial species Synechococcus sp. IU 625 adapts to growth in the presence of mercuric chloride, recovering from pigmentation and morphological defects. Cells accumulate mercury within 2 h of growth and by 3 days, the total mercury concentration is significantly reduced, with all remaining mercury associated with the cells. This suggests that Synechococcus sp. IU 625 can convert mercury to a volatile form.

Bioinformatic analysis of the metal-binding protein families and heavy metal resistance amongst cyanobacteria

Cyanobacteria are often used as an indicator of the presence and level of pollutants in the environment. They have been especially recognized for their ability to identify contamination of heavy metals. Class II metallothioneins (MTs), usually found in cyanobacteria, are low molecular weight metal-binding proteins and may be required for heavy metal tolerance. It would be important to examine the phylogenetic pattern as well as prokaryotic evolution of metal-binding protein families among cyanobacteria. All the available protein sequences of cyanobacteria metallothioneins from GenBank, PDB and Pfam have been aligned and the phylogenetic tree was constructed by utilizing four multiple sequence alignment software ClustalW, T-Coffee, POA and GCG-PileUp. Eight cyanobacteria included in this study were Synechococcus sp. PCC 7942, Synechococcus sp. WH 8102, Thermosynechococcus vulcanus, Thermosynechococcus elongates BP-1, Nostoc sp. PCC 7120, Gloeobacter violaceus PCC 7421, Oscillatoria brevis, and Magnetospirillum magnetotacticum. 22 reported heavy metal resistant sequences from these 8 species of cyanobacteria were aligned. A phyletic pattern search tool provided by Cluster of Orthologous Groups (COGs) database, a collection of COGs from 63 sequenced prokaryotes and 3 unicellular eukaryotic genomes was also used to select a desired pattern of presence-absence of species. Cn3D 4.1 program was used for structural alignment. The results indicated that the tree was composed by five clusters. Most Synechococcus and Thermosynechococcus were clustered into 2 clades while others had relatively far genetic distance with Synechococcus but closely linked to each other. Structure alignment of metallothionein among cyanobacteria indicated that a major portion of their structure are not identical but with similar properties such as polarity. The results clearly showed several conserved C-X-C motifs near N-and C-terminus of Class II metallothioneins.