Evaluation of sulfate rhizofiltration by Carpobrotus chilensis for treating mining waters

Chile, the world's leading copper producer, generates significant volumes of mining waters, some of which cannot be recirculated into the production process. These mining waters are characterized by elevated sulfate (SO 4 2 - ) concentrations, requiring sustainable management strategies for potential reuse. This study aims to evaluate the rhizofiltration technique using Carpobrotus chilensis for treating mining waters with a high SO 4 2 - concentration. Initially, the mining waters exhibited a pH of 7.97 ± 0.16 and a SO 4 2 - concentration of 2,743 ± 137 mg L-1, while the control water had a pH of 7.88 ± 0.08 and a SO 4 2 - concentration of 775 ± 19.0 mg L-1. The plants were hydroponically cultivated in 40 L containers with mining waters and drinking water as a control. Over an 8-week period, the pH of the mining water decreased to 3.12 ± 0.01, and the SO 4 2 - concentration declined to 2,200 ± 110 mg L-1. Notably, the fresh weight of roots was significantly higher in plants grown in mining water (22.2 ± 6.66 g) compared to those in the control treatment (14.3 ± 4.28 g). However, an undesirable increase in the acidity was observed in the mining waters after rhizofiltration, which was attributed to hydrogen sulfate (HSO4-) and/or root exudates. Despite the unexpected increase in acidity, C. chilensis effectively reduced the concentration of SO 4 2 - in mining waters by 20%. Additionally, the C. chilensis roots accumulated 4.84 ± 1.40% of sulfur (S), a level comparable to thiophore plants. This study provides evidence that this non-aquatic plant can be used in sulfate rhizofiltration.

Higher Novel L-Cys Degradation Activity Results in Lower Organic-S and Biomass in Sarcocornia than the Related Saltwort, Salicornia

Salicornia and Sarcocornia are almost identical halophytes whose edible succulent shoots hold promise for commercial production in saline water. Enhanced sulfur nutrition may be beneficial to crops naturally grown on high sulfate. However, little is known about sulfate nutrition in halophytes. Here we show that Salicornia europaea (ecotype RN) exhibits a significant increase in biomass and organic-S accumulation in response to supplemental sulfate, whereas Sarcocornia fruticosa (ecotype VM) does not, instead exhibiting increased sulfate accumulation. We investigated the role of two pathways on organic-S and biomass accumulation in Salicornia and Sarcoconia: the sulfate reductive pathway that generates Cys and l-Cys desulfhydrase that degrades Cys to H₂S, NH₃, and pyruvate. The major function of O-acetyl-Ser-(thiol) lyase (OAS-TL; EC 2.5.1.47) is the formation of l-Cys, but our study shows that the OAS-TL A and OAS-TL B of both halophytes are enzymes that also degrade l-Cys to H₂S. This activity was significantly higher in Sarcocornia than in Salicornia, especially upon sulfate supplementation. The activity of the sulfate reductive pathway key enzyme, adenosine 5'-phosphosulfate reductase (APR, EC 1.8.99.2), was significantly higher in Salicornia than in Sarcocornia These results suggest that the low organic-S level in Sarcocornia is the result of high l-Cys degradation rate by OAS-TLs, whereas the greater organic-S and biomass accumulation in Salicornia is the result of higher APR activity and low l-Cys degradation rate, resulting in higher net Cys biosynthesis. These results present an initial road map for halophyte growers to attain better growth rates and nutritional value of Salicornia and Sarcocornia.

Phytostabilization of arsenic in soils with plants of the genus Atriplex established in situ in the Atacama Desert

In the ChiuChiu village (Atacama Desert, Chile), there is a high concentration of arsenic (As) in the soil due to natural causes related to the presence of volcanoes and geothermal activity. To compare the levels of As and the growth parameters among plants of the same genus, three species of plants were established in situ: Atriplex atacamensis (native of Chile), Atriplex halimus, and Atriplex nummularia. These soils have an As concentration of 131.2 ± 10.4 mg kg(-1), a pH of 8.6 ± 0.1, and an electrical conductivity of 7.06 ± 2.37 dS m(-1). Cuttings of Atriplex were transplanted and maintained for 5 months with periodic irrigation and without the addition of fertilizers. The sequential extraction of As indicated that the metalloid in these soils has a high bioavailability (38 %), which is attributed to the alkaline pH, low organic matter and Fe oxide content, and sandy texture. At day 90 of the assay, the As concentrations in the leaves of A. halimus (4.53 ± 1.14 mg kg(-1)) and A. nummularia (3.85 ± 0.64 mg kg(-1)) were significantly higher than that in A. atacamensis (2.46 ± 1.82 mg kg(-1)). However, the three species accumulated higher levels of As in their roots, indicating a phytostabilization capacity. At the end of the assay, A. halimus and A. nummularia generated 30 % more biomass than A. atacamensis without significant differences in the As levels in the leaves. Despite the difficult conditions in these soils, the establishment of plants of the genus Atriplex is a recommended strategy to generate a vegetative cover that prevents the metalloid from spreading in this arid area through the soil or by wind.

Cloning, expression and decoding of the cold adaptation of a new widely represented thermolabile subtilisin-like protease

AIMS

Cloning, expression and characterization of a new cold-adapted protease with potential biotechnological application, isolated from Antarctic bacteria.

METHOD AND RESULTS

A subtilisin-like gene was isolated from several Antarctic bacterial genus using CODPEHOP-designed primers and a genome walking method. This gene encodes a precursor protein, which undergoes an autocatalytic cleavage resulting in a 34.6 kDa active cold-adapted protease with a maximum activity at 25-35°C and optimum pH of 8.0-9.0. It showed a higher catalytic efficiency at lower temperatures compared to its mesophilic counterpart. Heat-induced inactivation resulted in a very low melting point. Local packing analysis using the homology model indicated Ala284 as an important cold-adaptation determinant, which was corroborated by the site-directed mutagenesis.

CONCLUSIONS

A new thermolabile subtilisin-like protease has been successfully cloned and analysed, and an important hot spot in the evolution of the cold adaptation and substrate specificity of this enzyme was identified and tested.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work reports a new cold-adapted protease with a vast representation amongst Antarctic genus, suggesting therefore its evolutionary success in this cold environment. Likewise, important sites for genetic potentiation have been identified, which are extrapolated to other enzymes of the same kind.

Prediction of retention time of cutinases tagged with hydrophobic peptides in hydrophobic interaction chromatography

Hydrophobic interaction chromatography (HIC) is an important technique for protein purification, which exploits the separation of proteins based on hydrophobic interactions between the stationary phase ligands and hydrophobic regions on the protein surface. One way of enhancing the purification efficiency by HIC is the addition of short sequences of peptide tags to the target protein by genetic engineering, which could reduce the need for extra and expensive chromatographic steps. In the present work, a methodology for predicting retention times of cutinases tagged with hydrophobic peptides in HIC is presented. Cutinase from Fusarium solani pisi fused to tryptophan-proline (WP) tags, namely (WP)2 and (WP)4, and produced in Saccharomyces cerevisiae strains, were used as model proteins. From the simulations, the methodology based on tagged hydrophobic definition proposed by Simeonidis et al. (Phitagged), associated to a quadratic model for predicting dimensionless retention times, showed small differences (RMSE<0.022) between observed and estimated retention times. The difference between observed and calculated retention times being lower than 2.0% (RMSE<0.022) for the two tagged cutinases at three different stationary phases, except for the case of cut_(wp)2 in octyl sepharose-2 M ammonium sulphate. Therefore, we consider that the proposed strategy, based on tagged surface hydrophobicity, allows prediction of acceptable retention times of cutinases tagged with hydrophobic peptides in HIC.

Follicle-stimulating hormone treatment reverses the effect of hypophysectomy on cell proliferation in the chicken embryo ovary

The present study evaluated the effect of FSH treatment on ovarian cell proliferation in the hypophysectomized chicken embryo. Hypophysectomy (Hx) was performed by the partial decapitation technique. Two series of experiments were performed: (a) Hx embryos were treated at 8 days of development with recombinant human FSH (rhFSH) and evaluated at 9 days by measuring BrdU incorporation; (b) Hx embryos were injected with rhFSH and rhCG at 9 days of development and the proliferation rate was measured at 13 days. The presence of mRNA for FSHR and LHR in the ovary of control and Hx embryos was demonstrated by RT-PCR analysis. There was a decrease in the percentage of BrdU labeled cells in the absence of hypophysis at 9 and 13 days of incubation. The decrease was reversed with rhFSH treatment. This effect was observed in the ovarian surface epithelium and the somatic cells of the cortex and the medulla in the 9-day-old embryo. Moreover, the number of somatic, steroidogenic, and germ cells was reduced at 13 days of incubation in the Hx embryo; when treated with rhFSH the number of cells increased to the level of controls. In another experiment, ovaries of 9-day-old chicken embryos were organ cultured for 48 h in a serum-free medium with rhFSH and rhCG separately. The proliferation index was incremented by rhFSH compared to control and rhCG-treated embryos. Therefore, FSH stimulates somatic cell proliferation in the chicken embryo ovary as early as 9 days of development.

Comparison of genotypic and phenotypic techniques for assessing the variability of the fungus Epicoccum nigrum

AIMS

The diversity within a collection of worldwide isolates of Epicoccum nigrum has been studied using several phenotypic approaches. In addition, the abilities of phenotypic and genotypic techniques for the differentiation of a set of isolates are compared.

METHODS AND RESULTS

The methodology used include the study of isozymes (acetyl esterase and alkaline phosphatase), HPLC profile of metabolites and antibiotic activities against a panel of bacteria, yeasts and filamentous fungi, and cytotoxicity against three mammalian cell lines. Two procedures for assessing the relationships within a collection of isolates, using a combination of the techniques, were evaluated, comparing the advantages and disadvantages of each method.

CONCLUSIONS

The results showed that each individual technique allows differentiation of the isolates studied to some degree and that the information provided by each technique could be considered as complementary. Genotypic techniques were more powerful than the phenotypic ones to discriminate among the strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work evaluates the predictive value of several phenotypic techniques on a collection of fungal isolates, and compares the results obtained with genotypic techniques performed on the same strains.

Overproduction, purification, and characterization of beta-1,3-glucanase type II in Escherichia coli

An Escherichia coli recombinant system produced soluble and full-length beta-1,3-glucanase type II (BglII) cloned from the yeast-lytic actinomycete Oerskovia xanthineolytica. The expression system was designed to produce recombinant BglII with a six-histidine peptide fused to the carboxy end of the protein. The expression level was optimized to produce 30% of total protein of E. coli as the recombinant protein, releasing 75% to the extracellular space. The 43-kDa recombinant protein was purified by IMAC to homogeneity and its molecular and biochemical characteristics were studied, showing that there are no important functional differences with those properties described for the BglII purified from O. xanthineolytica.

Presence of a simple tandem repeat in the ITS1 region of the Xylariales

A Simple Tandem Repeat sequence of 11 nucleotides has been found in the ITS1 region of the rDNA of members of Order Xylariales. The number of repetitions detected ranged from one to six, and they could be found in pure tandem or interspersed. The same core sequences have also been found in DNA from other organisms, although usually not repeated in tandem. These repetitions could have been generated by slipped strand mispairing. The presence of this sequence increases the normal rate of divergence in the ITS1 of the Xylariales. The phylogenetic implications of the presence of this sequence in the molecular taxonomy of Xylariales are also discussed.

Inhibitors of farnesylation of Ras from a microbial natural products screening program

Mutant ras oncogenes are associated with various human tumors such as pancreas, colon, lung, thyroid, bladder and several types of leukemia. Prenylation of Ras proteins plays a major role in cell proliferation of both normal and cancerous cells. Normal and oncogenic Ras proteins are posttranslationally modified by a farnesyl group that promotes membrane binding. Inhibitors of farnesyl protein transferase (FPTase), the enzyme that catalyzes the prenylation of Ras proteins, inhibit growth of tumor cells. In an effort to identify structurally diverse and unique inhibitors of FPTase, a program devoted to screening of natural products was initiated. This effort led to the identification of 10 different families of compounds, all of which selectively inhibit FPTase with a variety of mechanisms that are reviewed in this manuscript. These compounds originated from the fermentations of a number of microorganisms, either actinomycetes or fungi, isolated from different substrates collected in tropical and temperate areas. A chemotaxonomic discussion on the distribution of each compound among single or different types of microorganisms, either phylogenetically related or unrelated species, is included.

New genus-specific primers for the PCR identification of members of the genus Saccharomonospora and evaluation of the microbial diversity of wild-type isolates of Saccharomonospora detected from soil DNAs

Members of the genus Saccharomonospora are isolated infrequently, probably due to the low occurrence of these actinomycetes in the environment. Although members of this genus can easily be identified by micromorphological criteria, the extensive chemotaxonomic characterization of each new isolate is a time-consuming task which cannot always be undertaken when handling large numbers of strains as is the case in natural products screening programmes. In this work, the design of one set of genus-specific oligonucleotides which allows rapid detection of members of the genus Saccharomonospora by means of PCR-specific amplification is presented. The genus specificity of these primers was validated on a wide range of collection and wild-type strains, and subsequently applied to evaluate the presence of representatives of this taxon directly from soil DNAs. Partial 16S rDNA sequencing of representative wild-type strains was used to validate their genus assignment. Further analyses of PCR fingerprinting patterns and 16S-23S internal transcribed spacer sequences were used to determine the diversity of wild-type isolates obtained from soils. This study shows the usefulness of the application of these primers for the direct identification of members of this genus and in assessment of its occurrence within natural microbial habitats.

Evaluation of different PCR-based DNA fingerprinting techniques for assessing the genetic variability of isolates of the fungus Epicoccum nigrum

Thirty-six strains of the fungus Epicoccum nigrum, isolated from different substrata and ecosystems of Europe, America and Africa, were analysed using 14 molecular markers included in 5 different genetic fingerprinting techniques: AP-PCR, tDNA-PCR, microsatellite-primed PCR, ARDRA and AFLP. All of the techniques used were able to differentiate the isolates, showing a high genetic diversity within the species. However, the different techniques detected different levels of similarity among the strains; ARDRA shows the most homogeneous results whilst AP-PCR shows the most heterogeneous. The similarity indices achieved for each strain were compared for the different techniques. The distribution obtained by microsatellite-primed PCR was similar to those shown by AP-PCR techniques. tDNA-PCR and AFLP rendered similar distributions, and ARDRA showed remarkably different results from the other techniques. The results also reveal the lack of an overall correlation between geographical or ecological origin of the isolates and their genotypes.

Design of a primer for ribosomal DNA internal transcribed spacer with enhanced specificity for ascomycetes

A primer able to amplify the internal transcribed spacers (ITS) of the ribosomal DNA (rDNA), having enhanced specificity for ascomycetes, was identified by reviewing fungal ribosomal DNA sequences deposited in GenBank. The specificity of the primer, named ITS4A, was tested with DNA extracted from several species of ascomycetes, basidiomycetes, zygomycetes, mastigomycetes and mitosporic fungi (formerly deuteromycetes) and also from plants. The PCR annealing temperature most specific for ascomycetes was found to be 62 degrees C and 64 degrees C for the primer pairs ITS5 + ITS4A and ITS1F + ITS4A, respectively. At these annealing temperatures, all ascomycetous DNA samples were amplified efficiently with the ITS4A primer. The sensitivity limit was in the range 10(-14) g of DNA. This primer could also provide useful tools in suggesting the affinities of many mitosporic fungi with their perfect states.

Mating type-correlated molecular markers and demonstration of heterokaryosis in the phytopathogenic fungus Thanatephorus cucumeris (Rhizoctonia solani) AG 1-IC by AFLP DNA fingerprinting analysis

The destructive soil-borne plant pathogenic basidiomycetous fungus Thanatephorus cucumeris (Frank) Donk [anamorph: Rhizoctonia solani Kühn] is not a homogeneous species, but is composed of at least twelve anastomosis groups (AG), which seem to be genetically isolated. The genetics of several T. cucumeris anastomosis groups has been studied by analysis of heterokaryotic tuft formation in the area of contact between homokaryotic single-spore isolates, revealing that AG 1 is heterokaryotic and bipolar. To prove that tuft formation is due to heterokaryosis, AFLP DNA fingerprinting has been applied to a heterokaryotic T. cucumeris AG 1-IC isolate, its homokaryotic single spore-derived progeny, and newly formed heterokaryons. By means of AFLP markers, it is demonstrated that fluffy tufts formed upon pairing of homokaryons from different mating types are newly formed heterokaryons. Mating type-correlated markers have also been found, which will be useful for future studies of the genetics of this fungal species complex.

Identification at strain level of Rhizoctonia solani AG4 isolates by direct sequence of asymmetric PCR products of the ITS regions

The relatedness of nine isolates of Rhizoctonia solani, belonging to anastomosis group (AG) 4, and one isolate of AG1 was determined by comparative sequence analysis based on direct sequencing of PCR-amplified ribosomal DNA [the internal transcribed spacer (ITS) region and the 5.8 s ribosomal DNA]. The 5.8 s rDNA is completely conserved, but both ITS regions show variation among strains. AG1 was an outgroup based on anastomosis ability and RFLP analyses. Phylogenetic analyses based on the ITS sequences suggest that the analyzed AG4 strains can be divided into three groups that correlate with habitat and virulence.

Thiobacillus ferrooxidans tyrosyl-tRNA synthetase functions in vivo in Escherichia coli

The tyrosyl-tRNA synthetase gene (tyrZ) from Thiobacillus ferrooxidans, an acidophilic, autotrophic, gram-negative bacterium that participates in bioleaching of minerals, was cloned and sequenced. The encoded polypeptide (TyrRZ) is 407 amino acids in length (molecular mass; 38 kDa). The predicted protein sequence has an extensive overall identity (44%) to the sequence of the protein encoded by the Bacillus subtilus tyrZ gene, one of the two genes encoding tyrosyl-tRNA synthetases in this microorganism. Alignment with Escherichia coli TyrRS revealed limited overall identity (24%), except in the regions of the signature sequence for class I aminoacyl-tRNA synthetases. Complementation of an E. coli strain with a thermosensitive mutation in TyrRS showed that the protein encoded by the T. ferrooxidans tyrZ gene is functional and recognizes the E. coli tRNA(Tyr) as a substrate. TyrZ is a single-copy gene as revealed by Southern blot analysis. The gene was localized upstream from the putative promoters of the rrnT2 ribosomal RNA operon. Although no rho-independent transcription terminator was found between the two genes, a 1.3-kb RNA hybridized to a DNA probe derived from the tyrZ gene. The functional relationship between these two transcription units is discussed.

Identification and structural analysis of a ribosomal RNA gene promoter from Thiobacillus ferrooxidans

The 5'-terminus of a rRNA operon (rrnT2) from Thiobacillus ferrooxidans was characterized. The rRNA promoters from this microorganism were identified by means of a functional assay in Escherichia coli. DNA sequencing of the promoter region, upstream the 16 S rRNA gene, showed the presence of a consensus sequence for bacterial ribosomal promoters. Other features such as a 'discriminator' sequence, antiterminator elements and an upstream hexanucleotide common to several rRNA operons were also found. Two other putative transcription promoters were also identified.

Characterization of the two rRNA gene operons present in Thiobacillus ferrooxidans

The organization of rRNA genes from the autotrophic, acidophilic bacterium Thiobacillus ferrooxidans has been examined. Two rRNA operons were found in this microorganism by means of genomic hybridization studies. Recombinant plasmids, pTR-3 and pTR-1 that carry a portion of 16/23 S rDNA from one operon and the 5'-flanking region of the second operon, respectively, were identified and characterized.

Radiation therapy for transitional cell bladder carcinoma. A ten-year experience

From 1969 to 1979, 185 patients with transitional cell bladder carcinoma were curatively irradiated; 147 were treated with radiation alone (RT) and 38 received a combined radiation + surgery (RT + S). At presentation, 40 percent of the patients had obstructive uropathy which yielded a much lower five-year survival (18%) than when it was absent (50%). The overall five-year disease-free survival was 30 percent and 53 percent for patients treated with radical RT and RT + S, respectively. Among patients subjected to preoperative irradiation, downstaging was seen in 40 percent of postsurgical specimens, with 27 percent of the specimens showing no evidence of tumor; these patients had excellent survival. Severe complications were seen in 3 percent, 10 percent, and 27 percent of patients in the radical RT, RT + S, and radical RT + salvage cystectomy groups. Survival results, pelvic controls, and patterns of failure are presented.

Prophylactic versus no brain irradiation in regional small cell lung carcinoma

Among 104 complete responders entered in a randomized prospective trial of treatments for regional small cell undifferentiated carcinoma of the lung, 52 received prophylactic irradiation of the brain, 3,000 rad in 10 fractions, and 52 did not. The median survivals were 53 and 52 weeks respectively, and the incidences of brain metastases were 5% and 20%. Prophylactic brain irradiation was not associated with significant long-term toxicity.

Systemic hemibody irradiation for overt and occult metastases

Hemibody irradiation was initially employed as a palliative technique to treat diffuse metastatic disease in one session as opposed to multiple fields over an extended period. It provides a radiation treatment for disseminated cancer and therefore has been termed "systemic" therapy. Since it is possible to treat both halves of the body sequentially, it allows radiation treatment to the whole body in larger doses than could be accomplished with total-body irradiation. Because of the success in terms of dramatic rapid pain relief and the objective response on metastatic disease, it has been explored in the treatment of occult disease and as consolidation therapy in patients with tumors that have responded to chemotherapy. When hemibody irradiation is combined with chemotherapy, responses have been shown in metastases for several primaries, particularly small cell carcinoma, which is perhaps the most encouraging, and supports further research in the treatment of micrometastatic disease for this tumor type. As the technique moves from its current research phase into more general clinical use, radiation oncologists should become more familiar with the treatment, and the hospitalization originally required may be able to be avoided. An intensive premedication program has been developed to facilitate this. Innovative approaches using radiosensitizers, radioprotectors, hyperthermia, and hyperfractionation are ideas that are starting to be tested and will be further explored in the near future.

Combined modality treatment of regional small cell undifferentiated carcinoma of the lung: a cooperative study of the RTOG and ECOG

Between 1975 and 1979, 271 patients with regional small cell undifferentiated (including oat cell) carcinoma of the lung were entered into a study involving treatment by radiation therapy (4500 cGy (rad) in five weeks) to the primary tumor, mediastinum and supraclavicular lymph nodes, and a randomization to receive or not receive prophylactic treatment of the brain (3000 cGy in two weeks) and a randomization to prophylactic or delayed chemotherapy (cyclophosphamide and CCNU). Analysis of the data indicates that the median survival for responders (53 weeks) was significantly longer than that of the non-responders and partial responders (37 and 34 weeks). Median survival by treatment arm was 48 weeks for thoracic irradiation (TI), brain irradiation (BI), and early chemotherapy (CT), 44 weeks for TI alone, 41 weeks for TI and CT, 38 weeks for TI and BI. Regional complete and partial tumor responses were 52 and 25% for prophylactic chemotherapy and 44 and 35% for delayed chemotherapy. The site of first failure was regional in 12%, regional and distant simultaneously in 21%, and distant only in 46%. Elective brain irradiation significantly reduced the incidence of brain metastases from 21 and 5%, but did not improve survival.

Phase II study of cisplatin, maytansine, and chlorozotocin in small cell lung carcinoma (EST 2578)

Seventy-three patients with small cell lung carcinoma refractory to standard chemotherapy were entered in this phase II randomized study of cisplatin, maytansine, and chlorozotocin. Of the 58 evaluable patients, only one partial response was observed among 21 patients given cisplatin, and no responses were seen among 19 given maytansine or 18 given chlorozotocin. One patient treated with chlorozotocin and two treated with cisplatin experienced life-threatening thrombocytopenia. One third of the maytansine-treated patients experienced moderate or severe neurologic toxicity. The overall median survival was 9.7 weeks. Chlorozotocin treatment was associated with inferior survival (7.7 weeks).

Properties of two marine bacteriophages

Chen, Peter K. (Georgetown University, Washington, D.C.), Ronald V. Citarella, Omar Salazar, and Rita R. Colwell. Properties of two marine bacteriophages. J. Bacteriol. 91:1136-1139. 1966.-Various properties have been determined for two bacteriophages, NCMB 384 and 385, and their host, NCMB 397, a Cytophaga sp., isolated from the marine environment. The purified bacteriophages have been subjected to serological analysis, results of which indicate a high degree of relatedness. Purified, highly polymerized deoxyribonucleic acid (DNA) prepared from the host strain showed an overall base composition of 37 moles% guanine + cytosine (buoyant density of 1.696 g/cc). The bacteriophage DNA, in the native configuration, from NCMB 384 and 385 banded at 1.691 g/cc in a CsCl gradient and the denatured bacteriophage DNA demonstrated a bimodal peak. Stability tests of the bacteriophages in various buffers and diluents suggest a requirement for inorganic cations, most likely Na(+) and Mg(++), for retention of viability.