A hydroponic system for growing gnotobiotic vs. sterile plants to study phytoremediation processes

In some phytoremediation studies it is desirable to separate and define the specific contribution of plants and root-colonizing bacteria towards contaminant removal. Separating the influence of plants and associated bacteria is a difficult task for soil root environments. Growing plants hydroponically provides more control over the biological factors in contaminant removal. In this study, a hydroponic system was designed to evaluate the role of sterile plant roots, rhizodeposition, and root-associated bacteria in the removal of a model contaminant, phenol. A strain of Pseudomonas pseudoalcaligenes that grows on phenol was inoculated onto plant roots. The introduced biofilm persisted in the root zone and promoted phenol removal over non-augmented controls. These findings indicate that this hydroponic system can be a valuable tool for phytoremediation studies that investigate the effects of biotic and abiotic factors on pollution remediation.

Eichhornia crassipes capability to remove naphthalene from wastewater in the absence of bacteria

The aim of the current study was to investigate the potential of an aquatic plant, the water hyacinth (Eichhornia crassipes) devoid rhizospheric bacteria, to reduce naphthalene (a polyaromatic hydrocarbon) present in wastewater and wetlands. The capability of sterile water hyacinth plants to remove naphthalene from water and wastewater was studied in batch systems. Water hyacinths enhance the removal of pollutants through their consumption as nutrients and also through microbial activity of their rhizospheric bacteria. Experimental kinetics of naphthalene removal by water hyacinth coupled with natural rhizospheric bacteria was 100% after 9 d. Plants, decoupled of rhizospheric bacteria, reduced naphthalene concentration up to 45% during 7 d. Additionally, naphthalene uptake by water hyacinth revealed a biphasic behavior: a rapid first phase completed after 2.5 h, and a second, considerably slower rate, phase (2.5-225 h). In conclusion, water hyacinth devoid rhizospheric bacteria reduced significantly naphthalene concentration in water, revealing a considerable plant contribution in the biodegradation process of this pollutant.

Removal of phenol in a constructed wetland system and the relative contribution of plant roots, microbial activity and porous bed

Analysis of a low organic load constructed wetland (CW) system was performed in order to understand the relative role of its various components contribution in phenol removal (100 mg/L) under controlled plant biomass/gravel/water experimental ratios (50 g/450 g/100 mL). The results [expressed as phenol50/time (hours) required to remove 50% of the initial phenol concentration] showed that the highest phenol removal occurred by combined biofilms from roots and gravel attached (phenol50=19), followed by gravel biofilm (phenol50=105) and planktonic (suspended in water) bacteria (phenol50=>200). An in depth analysis revealed that plants contribution alone (antibiotics sterilized) was minor (phenol50=>89) while roots supported biofilm resulted in a significant phenol removal (phenol50=15). Therefore in this type of CW, the main phenol removal active fraction could be attributed to plant roots' biofilm bacteria.

Diverse effects of ascorbic acid and palmitoyl ascorbate on Helicobacter pylori survival and growth

Among many antioxidants used in the food, pharmaceutical and cosmetic industries, ascorbic acid (AA) is one of the most important. AA has been suggested to decrease the risk of gastric disease (gastritis, duodenal ulcer, and carcinoma) by direct action on Helicobacter pylori. However, there are limited studies on the possible role of AA and its derivatives such as palmitoyl ascorbate (PA) on the growth and survival of H. pylori. In the present study it was demonstrated in vitro that AA in the concentration range 10-20 mg x ml(-1) (50-100 mM) inhibited H. pylori growth in liquid medium under microaerophilic conditions. In contrast, under aerobic conditions AA in the concentration range 2-20 mg x ml(-1) (10-100 mM) significantly increased the survival of H. pylori presumably eliminating the toxic effect of reactive oxygen species on bacterial cells. The hydrophobic derivative of AA, PA (a food antioxidant), demonstrated a strong antibacterial effect, under both aerobic and microaerophilic conditions in the concentration range 0.04-0.4 mg x ml(-1) (0.1-1.0 mM). This effect was also tested on other bacterial strains: Escherichia coli, Proteus vulgaris, Proteus mirabilis, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Clostridium sporogenes and Campylobacter jejuni. Among these bacterial strains, PA showed a similar inhibitory effect on B. cereus and B. subtilis as observed with H. pylori. The results suggest that PA may be considered an important AA derivative in eradication of H. pylori in vitro and in vivo and to decrease the risk for gastric diseases.

Immobilizing humic acid in a sol-gel matrix: a new tool to study humic-contaminants sorption interactions

Humic substances originated from aquatic, soil, or sediment environments are mixtures of humic compounds with various characteristics. Sorption interactions with isolated, well defined humic fractions can be studied either in an aqueous phase ("dissolved humic substances"), or in a solid-phase, by coating mineral particles with the humic materials, or simply by working with humic acid particles (powder) at low pH to minimize dissolution. Each attitude, by definition, can be studied by different experimental techniques and has a different meaning for understanding natural environmental processes. In this study, a new tool for studying sorption interactions is presented. Sol-gel was used as an inert matrix to immobilize (entrap) various humic acids (HAs), and then used to study the interactions of several polycyclic aromatic hydrocarbons (PAHs) with the entrapped HA. Linear and nonlinear sorption coefficients were highly correlated with contaminant hydrophobicity. Sorption of pyrene to immobilized HA was in the order of soil HA > Aldrich HA approximately = peat HA. It was concluded that the entrapped HAs retained their original properties in the gel matrix and were accessible to the external contaminant through the pore network. Additionally, binding coefficients of pyreneto dissolved humic substances and to dissolved organic matter (DOM) were determined from the reduction in pyrene sorption to immobilized HA in the presence of dissolved humic material or DOM in solution. Binding coefficients of pyrene were in the order of the following: dissolved Aldrich HA > dissolved peat fulvic acid (FA) > DOM derived from mature compost > DOM derived from fresh compost.

Surface and subsurface irrigation with effluents of different qualities and presence of Cryptosporidium oocysts in soil and on crops

A large variety of human pathogens are excreted in wastewater including bacteria, viruses, protozoan cysts and helminth eggs. In raw sewage, human pathogens reach high numbers, thereafter decreasing successively at each treatment step. However, the final effluents still contain a large fraction of these pathogens that may pose a serious public health. Among the various crops irrigated with effluents, vegetables are the most vulnerable to contamination. Vegetables, usually eaten raw (uncooked) or with rich dressings (causing regrowth of some pathogenic bacteria) pose the main threat to humans. The importance of microbiological and parasitological criteria for reused water has been repeatedly emphasized. Some microbiological recommendations based on epidemiological data have been established for untreated wastewater, there is still a need to define the criteria for effluent quality required for unrestricted crop irrigation. This paper presents a field study comparison of two irrigation methods: surface and subsurface of field crops (mainly vineyard) and follow-up of Cryptosporidium oocysts in soil at different depths (0 to 90 cm). Oocysts were isolated at all depths without a clear pattern of distribution (0 to 640 oocysts/g). In addition different vegetables irrigated with different effluent qualities were tested for the presence of Cryptosporidium oocysts and Giardia cysts. The highest prevalence of oocysts was found on zucchini that has a sticky and hairy outer surface (80 to 10,000 oocysts/0.5 kg).

Secondary wastewater disposal for crop irrigation with minimal risks

A critical objective for any wastewater reuse program is to close the gap between supply of and demand for water and to minimize health and environmental hazards. Thus, the effects of treated effluent on crops, soils and community health must be considered carefully. When applying wastewater to soil-plant systems, it is to be noted that the passage of water through the soil reduces considerably the number of microorganisms carried out by the reclaimed wastewater. Nevertheless, there is a need to study the real rate of organism decay subject to water quality, soil and vegetable characteristics, and irrigation method. The aim of this work is to determine the fate of the fecal coliforms, coliphages F+ and CN13, and helminth eggs survival during the application of reclaimed wastewater in a vineyard orchard near the City of Arad (Israel) via onsurface and subsurface drip irrigation systems. Wastewater obtained from a stabilization pond, and soil samples were tested and an important decrease of microorganisms was reached in both cases, with the better values obtained with the sub-surface drip irrigation system.

Cinnamon extracts' inhibitory effect on Helicobacter pylori

Ethanol and methylene chloride extracts of cinnamon were compared for their effect on Helicobacter pylori growth and urease activity. Methylene chloride extract was found to inhibit growth of H. pylori, while ethanol extract counteracted its urease activity. Cinnamon extract (from methylene chloride) inhibited H. pylori at concentration range of common antibiotics. Complete inhibition in vitro was achieved by 50 microg/ml in solid medium (egg yolk emulsion agar) and by 15 microg/ml in liquid medium (supplemented brain heart infusion broth). The cinnamon extracts were more inhibitory on free urease than on whole cell urease.

Evaluation of a portable differential continuous flow centrifuge for concentration of Cryptosporidium oocysts and Giardia cysts from water

A portable device was developed and assembled from a stationary differential continuous flow centrifuge usually employed for blood cell separation, for the purpose of concentrating Cryptosporidium and Giardia from large volumes of water. Following compaction onto the wall of the disposable plastic centrifuge bowl and aspiration of residual water, the oocysts and cysts were dislodged by injection of a 20 ml solution containing 0.01% Tween-80 and 1% SDS and vigorous shaking. Following aspiration, the oocysts were pelleted, reacted with specific FITC-conjugated monoclonal antibodies, and enumerated via fluorescence microscopy. The entire procedure required about 2 h. Initially, 55% and 87% of Cryptosporidium oocysts and Giardia cysts, respectively, were recovered from 45 litres of tap water, and 27% and 57%, respectively, from river water. Adjustments in centrifuge speed and flow rates improved recovery to about 90% for Cryptosporidium oocysts and hence, this method compared favourably with the recently developed calcium carbonate flocculation method. It was superior in time requirement and volume flexibility, and showed a distinct advantage over the standard cartridge filtration method in all respects. The continuous flow centrifugation equipment is compact, mobile, flexible, and yields reproducibly high recovery rates. The ease of handling, speed of performance and minimal requirements for post-concentration equipment, reagents and labour make the system highly cost-effective. It appears to offer an improved method, well suited for use by water utilities for monitoring the burden of water-borne protozoan pathogens.

Bacteriophages of enteric bacteria in drinking water, comparison of their distribution in two countries

The presence of bacteriophages infecting enteric bacteria was tested in more than 1500 drinking water samples in Israel and Spain. Bacteriophages tested were somatic coliphages, F-specific bacteriophages and Bacteroides fragilis bacteriophages. The three groups of bacteriophage were isolated in 100 ml water samples by the presence/absence test with similar frequencies, which ranged from 4.4% for somatic coliphages to 6.1% for bacteriophages infecting Bact. fragilis. In contrast, the frequency of isolation of bacteriophages was significantly higher than the frequency of isolation of faecal coliforms, which averaged only 1.9%. No significant differences were observed between the frequencies of isolation between the samples tested in Spain and those tested in Israel. The percentage of groundwater samples containing faecal coliforms and somatic coliphages was reduced significantly by chlorination, despite known deficiencies. However, there was no effect on the occurrence of F-specific bacteriophages and Bact. fragilis bacteriophages.

Sol-gel applications in environmental biotechnology

Sol gel process was applied for three different applications in environmental biotechnology: (1) thin, fluorescein diacetate-doped sol-gel film made possible epifluorescent microscopic examination of adsorbed Escherichia coli CN13 cells without additional staining: (2) Thiobacillus thiooxidans cell-free extract entrapped into sol-gel matrix displayed oxidative activity on H2S in liquid medium; and (3) two media (E. coli (EC) and sulfate-reducing bacteria (SRB)) were doped into sol-gel and used to enumerate environmental samples for E. coli and sulfate-reducing bacteria, by the most probable number (MPN) method. The comparison of the modified method with the standard enumeration method revealed very good correlation. The sol-gel MPN method is sensitive, saves times, and the substrate can be prepared and stored long-term at room temperature (up to 1 year).

In vitro inhibition of Helicobacter pylori by extracts of thyme

Extracts of several plants were tested for inhibitory activity against Helicobacter pylori. Among these plants thyme (aqueous extract) and cinnamon (alcoholic extract) were the most effective. Since aqueous extract of thyme is easier to produce and consume, it was further investigated. Compared with several antibacterials, the thyme extract had a significant inhibitory effect on H. pylori, reducing both its growth and potent urease activity. From the results of this study, the aqueous extract of thyme possesses a therapeutic potential which merits validation by clinical studies.

A simple, rapid and sensitive presence/absence detection test for bacteriophage in drinking water

A rapid, simple and sensitive direct bacteriophage presence detection method for 500 ml drinking water samples has been developed. The method includes a glass device consisting of a jar containing the water sample and an immersible probe filled with solidified soft agar containing bacterial host cells. Host bacteria in logarithmic phase were added to the experimental volume and the probe was submerged. The entire device was incubated in a water bath at 36 degrees C. Plaques of somatic bacteriophage infecting Escherichia coli strain CN13, could be detected within 3 h. Male-specific bacteriophages infecting E. coli F+ amp were detected within 6 h. Bacteriophage infecting the anaerobe Bacteroides fragilis subsp. fragilis HSP40 were detected after 8 h. Application of this device and the associated technique, enabled a one-step detection of 1 pfu of E. coli or Bact. fragilis specific bacteriophage in 500 ml drinking water samples.

Biochemical fingerprints of Legionella spp. by the BIOLOG system: presumptive identification of clinical and environmental isolates

Six Legionella strains were characterized with the BIOLOG identification system. A specific metabolic pattern for the six Legionella strains was observed after 24 h. Several positive reactions were detected intermittently in all six strains tested. The possible application of the BIOLOG system for identification of Legionella spp. from environmental or clinical samples is discussed.

Pig erythrocyte ghost cells used for concentration of enteric viruses from experimentally contaminated clinical specimens

A simple, rapid and efficient procedure of virus concentration from urine, cerebrospinal fluid (CSF), and feces was developed. Pig erythrocyte ghost cells were used to adsorb and elute such viruses as poliovirus LSC-1, echovirus 6, and human rotavirus (clinical isolate). In urine and CSF, the adsorption efficiency range was 80-100% and elution was from 85% to greater than 100%. In addition, poliovirus LSC-1 was used as an experimental model to examine this procedure under various clinical conditions, such as calcium, glucose, amino acids, and urea at high concentrations. These were added to normal urine specimens to simulate pathological conditions. The results suggest that pig erythrocyte ghost cells are an efficient matrix for adsorption and elution of enteric viruses found in clinical specimens of urine, CSF, and feces. This method might be useful in virus concentration from clinical specimens and for preparative microscopy and other clinical laboratory methods that require subsequent virus concentration.

Concentration of Giardia lamblia cysts, Legionella pneumophila, Clostridium perfringens, human enteric viruses, and coliphages from large volumes of drinking water, using a single filtration

Poliovirus, coliphages, Giardia lamblia cysts, Clostridium perfringens spores, and Legionella pneumophila were concentrated simultaneously in a single pass by sequential filtration of large volumes of drinking water through 3- and 1-micron wound electronegative fiberglass cartridge filters (25.4 cm). Filtration was performed under acidic conditions (pH 3.5) in the presence of 0.001 M aluminum chloride to enhance adsorption. Elution of all the microorganisms entrapped or adsorbed to the filters was obtained by a slow backwash elution with a 1.5% beef extract solution, pH 9.75, containing 0.5% Tween 80. Tween 80 was shown to enhance recovery of the bacteriophages, bacteria, and parasites. Giardia cysts were efficiently eluted (71%) and could be reconcentrated by low-speed centrifugation and purified by sucrose density gradient flotation at a final recovery of 52%. Legionella pneumophila cells were eluted at 64% and were further concentrated by low-speed centrifugation at an overall recovery of 55%. C. perfringens spores and coliphages were eluted at efficiencies of 82 and 86%, respectively, and reconcentrated with minimal loss by a detergent - protein flotation method. Poliovirus was eluted at 93% and reconcentrated at 78% efficiency by organic flocculation.

Phage f2 desorption from clay in estuarine water using nonionic detergents, beef extract, and chaotropic agents

Experimentally adsorbed bacteriophage f2 was eluted from clay particles in estuarine water using 1% Tween, 80.3% beef extract, and 0.3 M NaNO3 with 54% recovery. Replacing sodium nitrate with tetrasodium pyrophosphate (0.4 M) increased the recovery to 81%. Estuarine sediments treated with 1% Tween 80 revealed significantly higher male-specific phage elutions.

A highly efficient second-step concentration technique for bacteriophages and enteric viruses using ammonium sulfate and Tween 80

Addition of Tween 80 to a 1.5% solution of beef extract was found to enhance the elution of bacteriophages adsorbed to electronegative filters. When reconcentration of the eluate was attempted by ammonium sulfate precipitation, a floating layer containing most of the viruses was formed. This floating layer can be obtained with several nonionic detergents including Tween 80 and under a salt saturation of 55% with ammonium sulfate, potassium tartrate, and sodium phosphate. Virus recovery ranged from 91 to 103% and was obtained with several bacteriophage strains. With poliovirus type 1, coxsackievirus B-4, and rotavirus SA-11 the recoveries were 100, 20, and 80%, respectively, but toxicity to cell culture was encountered: after removal of the detergent by a second floating layer method the recovery was 32% for poliovirus. Compared with organic flocculation, this method also had both improved recovery for bacteriophages and protective properties for samples frozen at -70 degrees C.

A modified m-CP medium for enumerating Clostridium perfringens from water samples

Medium m-CP, designed for the isolation of Clostridium perfringens from water samples, contains indoxyl beta-D-glucoside, an expensive chemical that is present at a high concentration in this medium. The use of m-CP with three concentrations of indoxyl beta-D-glucoside was tested at 0, 60, and 600 mg/L. Lowering the amount of indoxyl beta-D-glucoside to 60 mg/L (1/10 the recommended concentration) reduced the cost of this medium without affecting its sensitivity.

Ghost cells as sorption matrix for virus concentration from water

Pig erythrocyte membranes were used as adsorbent material for the concentration of bacteriophage phi x-174, MS-2, and f2 from 5 ml of saline solution. The adsorption was carried out at pH 3.5, and the elution was carried out at pH 7.0. Compared with adsorption on 3% beef extract, bacteriophage adsorption on erythrocyte ghost cells yielded 93 to 100%, and elution was 92 to 100%, whereas beef extract organic flocculation yielded adsorption of 0 to 98.8% and elution of 61 to 86.6%. The same procedure but with poliovirus LSC-1 gave 100% adsorption and 91 to 129% elution.

Concentration of simian rotavirus SA-11 from tap water by membrane filtration and organic flocculation

Simian rotavirus SA-11 was concentrated from tap water by adsorption to and elution from microporous filters, followed by organic flocculation. Two types of filters were compared for their ability to concentrate the virus. Both Zeta Plus 60S and Cox AA type M-780 filters were efficient for virus adsorption, but the efficiency of virus elution was higher with Zeta Plus than with Cox filters. Optimum conditions for virus recovery from Zeta Plus filters included an input water pH of 6.5 to 7.5 and the use of 3% beef extract (pH 9.0) for elution. Under these conditions, an average of 62 to 100% of the virus was recovered in the concentrate. Organic flocculation was used as a second-step concentration method, with average recoveries of 47 to 69%. When the two methods were used to concentrate small numbers (7 to 75 PFU/liter) of input rotavirus, an average of 75 +/- 40% recovery was achieved. With large volumes of input water, however, recovery was reduced to 16 +/- 7%.