Showing papers on "Agar plate published in 1982"

Selective medium for isolation of Actinobacillus actinomycetemcomitans

Abstract: A selective medium, TSBV (tryptic soy-serum-bacitracin-vancomycin) agar, was developed for the isolation of Actinobacillus actinomycetemcomitans, TSBV agar contained (per liter) 40 g of tryptic soy agar, 1 g of yeast extract, 100 ml of horse serum 75 mg of bacitracin, and 5 mg of vancomycin The TSBV medium suppressed most oral species and permitted significantly higher recovery of A actinomycetemcomitans than nonselective blood agar medium The distinct colonial morphology and positive catalase reaction of A actinomycetemcomitans easily distinguished this bacterium from Haemophilus aphrophilus, Capnocytophaga species, and a few other contaminating organisms With the TSBV medium, even modestly equipped laboratories will be able to isolate and identify A actinomycetemcomitans from clinical specimens

Rapid Screen for Bacteria Degrading Water-Insoluble, Solid Hydrocarbons on Agar Plates

Abstract: A rapid procedure was devised for detecting on solid media bacteria able to degrade water-insoluble, solid hydrocarbons such as the polycyclic aromatic hydrocarbons phenanthrene, anthracene, and biphenyl After Alcaligenes faecalis AFK2 was inoculated on a plate containing mineral salts agar, an ethereal solution of phenanthrene (about 10%, wt/vol) was sprayed on the surface of the plate, and the plate was incubated at 30 degrees C for 2 to 3 days Colonies showing degradation were surrounded with clear zones on the opaque plate A similar clear zone also was formed around colonies which had been grown on a succinate-mineral salts agar or nutrient agar, followed by spraying of the ethereal solution of phenanthrene and further incubating for 1 day Other phenanthrene-assimilating bacteria, including Beijerinckia Bwt and Pseudomonas SPM64, also formed clear zones on phenanthrene-covered agar plates This method was applicable to detection of bacteria able to assimilate anthracene, naphthalene, and biphenyl

R-plasmid transfer in a wastewater treatment plant.

Abstract: Enteric bacteria have been examined for their ability to transfer antibiotic resistance in a wastewater treatment plant. Resistant Salmonella enteritidis, Proteus mirabilis, and Escherichia coli were isolated from clinical specimens and primary sewage effluent. Resistance to ampicillin, chloramphenicol, streptomycin, sulfadiazine, and tetracycline was demonstrated by spread plate and tube dilution techniques. Plasmid mediation of resistance was shown by ethidium bromide curing, agarose gel electrophoresis, and direct cell transfer. Each donor was mated with susceptible E. coli and Shigella sonnei. Mating pairs (and recipient controls) were suspended in unchlorinated primary effluent that had been filtered and autoclaved. Suspensions were added to membrane diffusion chambers which were then placed in the primary and secondary setting tanks of the wastewater treatment plant. Resistant recombinants were detected by replica plating nutrient agar master plates onto xylose lysine desoxycholate agar plates that contained per milliliter of medium 10 micrograms of ampicillin, 30 micrograms of chloramphenicol, 10 micrograms of streptomycin, 100 micrograms of sulfadiazine, or 30 micrograms of tetracycline. Mean transfer frequencies for laboratory matings were 2.1 X 10(-3). In situ matings for primary and secondary settling resulted in frequencies of 4.9 X 10(-5) and 7.5 X 10(-5), respectively. These values suggest that a significant level of resistance transfer occurs in wastewater treatment plants in the absence of antibiotics as selective agents. Images

Factors influencing the production of hardened glaucous carnation plantlets in vitro

Abstract: Medium type, its water status and the relative humidity in the culture vessel modified carnation leaf development in vitro. Carnation shoot apices cultured on liquid or on 0.8% agar solidified media developed into plantlets having succulent and translucent leaves which are not transplantable to non-aseptic conditions. Increasing the agar and/or sucrose concentration in the medium as well as decreasing the relative humidity in the culture vessel by a desiccant promoted glaucous leaf production. Increased water status (ψH2O and relative humidity) increased shoot proliferation and translucency of leaves. Decreased water status reduced shoot proliferation but induced the formation of glaucous leaves. The culture of apices for 5–6 days on liquid medium prior to their sub-culture to 1.5% agar medium improved shoot proliferation and normal leaf development. An agar slant prevented the submergence of apices in water accumulating on the medium and thus reduced leaf translucency. Survival was further increased by the transfer of plantlets in uncapped culture vessels to a desiccator for 1–2 weeks prior to transplanting to soil.

Comparative Study of Selective Media for Recovery of Yersinia enterocolitica

Abstract: To determine the relative efficacy of pectin agar, cellobiose-arginine-lysine (CAL) agar, Y medium, cefsulodin-irgasan-novobiocin (CIN) agar, MacConkey (MAC) agar, and salmonella-shigella (SS) agar for the recovery of Yersinia enterocolitica, 35 strains of this organism representing the serotypes most commonly associated with human disease in Canada and the United States were inoculated on test media in pure cultures and mixed in fecal specimens. Randomly picked stool specimens were also cultured on these media to determine their selectivity. The ability of test media to support the growth of Y. enterocolitica strains varied markedly. Several strains failed to grow on Y medium, and a few failed to grow on SS agar. There were no significant differences in cultural characteristics and the recovery rates of Canadian and American strains. The combined recovery of the pure cultures of Y. enterocolitica on test media as compared with blood agar was MAC, 75%; SS, 48%; pectin, 70%; CAL, 62%; Y, 15%; and CIN, 85%. The selectivity of the test media expressed as the percent difference of the fecal colony counts obtained on blood agar and the selective media was MAC, 7%; SS, 50%; pectin, 4%; CAL, 65%; Y, >/=99.9%; and CIN, 95%. When stool suspensions containing 10(2) colony-forming units of the test strains were plated, CIN medium yielded 100% recovery of all 35 strains from all fecal samples. The combined recovery rate for other media was CAL, 63%; Y, 14%; and SS, 11%. With 10(1) colony-forming units, CIN yielded a 100% recovery of the test strains, whereas CAL, Y, and SS agar showed a 0% recovery. None of the test organisms was recovered on either MAC or pectin agar at either dilution. The inhibitory effect of Y medium for Y. enterocolitica could be overcome to some extent by reducing the sodium oxalate and sodium desoxycholate content of the medium. One such modified Y medium offered optimum selectivity and ensured greater recovery of Y. enterocolitica when compared with the Y medium. We found CIN agar by far the most effective medium for the recovery of Y. enterocolitica. This medium was highly selective and almost completely inhibited the fecal flora, while at the same time supporting luxuriant growth of Y. enterocolitica. On CIN agar, Y. enterocolitica colonies were distinctive in appearance and measured 1.5 to 4 mm in diameter within 20 to 40 h of incubation.

Isolation of a bile salt sulfatase-producing Clostridium strain from rat intestinal microflora.

Abstract: Bile acid sulfates, formed in human and rat livers, are desulfated by the intestinal microflora. In our study we first isolated from conventional rat feces an unnamed bacterium, termed strain S1, which desulfated the 5 beta-bile salt 3 alpha-sulfates in vitro and in vivo after association with gnotobiotic rats. Strain S1 also possessed 12 alpha-hydroxysteroid dehydrogenase and bile salt-deconjugating activities. The strain was a strict anaerobic, CO2-requiring, gram-negative, sporeforming rod and was designated as belonging to the genus Clostridium. Growth was scarce in culture media, unless in the presence of 0.1% taurine, a sulfur-containing amino acid. Addition of this substance raised the number of bacteria in thioglycolate and peptone yeast media from 10(4) per ml to 10(6) to 10(7) per ml and increased the colony diameter on agar medium from 0.2 mm to 0.5 to 0.9 mm. Sulfatase activity was specific for the 5 beta-bile salt sulfates, leaving the 5 alpha-bile salt sulfates unchanged. In addition, the sulfatase activity was cell bound, and its production was dependent on the composition of the culture medium, although no minimal sulfur medium was required for sulfatase activity.

Characteristics and Identification of Pasteurella and Vibrio Species Pathogenic to Fishes using API-20E (Analytab Products) Multitube Test Strips

Abstract: Morphological, cultural, and biochemical characteristics of Pasteurella spp and Vibrio spp pathogenic to fishes are investigated Vibrio anguillarum, V ordalii, V alginolyticus, V parahaemolyticus, an unidentified Vibrio sp (AN1K), Pasteurella piscicida, and P multocida were cultured on API-20E multitube test strips (Analytab Products) and in Baumann's marine media with similar results The API-20E Profile Index was not useful for classification of fish bacteria studied and, using the index Vibrio sp AN1K was misidentified as P multocida Bacteria studied were also grown on Marine Agar (Difco) and on blood agar at 25 and 37 °C On blood agar at 37 °C some vibrios resembled pasteurellas as a result of pleomorphism and lack of motility Simple diagnostic procedures for identifying Pasteurella spp and Vibrio spp associated with fishes using the API-20E with modifications are presentedKey words: Pasteurella, Vibrio, characteristics, Analytical Profile Index, fish pathology

Cell aggregates in the soft agar “human tumour stem-cell assay”

Abstract: We evaluated colony formation in soft agar by cells obtained after mechanical and/or enzymatic disaggregation of 455 malignant human tumours Counting and assessment of cell colonies in the agar plates were done by inverted microscopy, computerized image analysis, and inspection of serial photomicrographs of the agar plates Our results indicate that standard methods of tumour disaggregation did not usually produce single-cell suspensions and that aggregates of tumour cells varying greatly in size were placed in the agar Most groupings of cells identified as colonies 1-3 weeks after plating arose from enlargement of preexisting aggregates of cells

Enrichment medium and control system for isolation of Campylobacter fetus subsp.jejuni from stools.

Abstract: Enrichment culture with a semisolid medium increased by 6% the isolation rate of Campylobacter fetus subsp. jejuni. The semisolid enrichment medium was also used successfully as a transport medium for Campylobacter isolates. A blood agar plate streaked with Pseudomonas aeruginosa, Clostridium perfringens, and a laboratory strain of Campylobacter was a good control system for the microaerophilic atmosphere. Good growth of all three organisms indicated satisfactory conditions for culturing Campylobacter.

Production of K88, K99, and 987P antigens by Escherichia coli cultured on synthetic and complex media.

Abstract: A synthetic medium (E agar) containing glucose and citric acid as the only organic nutrients was found superior to blood agar, Minca-IsoVitaleX (BBL Microbiology Systems, Cockeysville, Md.) agar and broth, and tryptic soy broth (without glucose) for promoting expression of K99 antigen by Escherichia coli strains isolated from diarrheic calves and piglets.

Rapid identification of Clostridium difficile by toxin detection.

Abstract: Rapid identification of Clostridium difficile in a stool specimen could be accomplished within 24 h by detection of toxin elaborated in an agar or broth culture containing cycloserine and cefoxitin. Broth culture seemed to give a more rapid and sensitive result than the agar plate culture. For cultivation of C. difficile in stool, we recommend the use of chopped meat broth and blood agar plate, the former for toxin detection in 1 to 2 days and the latter for colonial morphology and isolation of a pure culture.

Characterization of stable spontaneous metastatic variant lines of RSV‐transformed mouse fibroblasts

Abstract: The correlation between metastatic potential and a series of biological properties was investigated in two mouse fibrosarcoma lines (SR-BALB and B77-3T3), transformed by different strains of Rous sarcoma virus (RSV). In the absence of selective pressure the metastatic potential was different in the two lines. The SR-BALB sarcoma did produce both spontaneous metastases from s.c. site and i.v. lung colonization with a high incidence (respectively in 60% and 80% of treated animals). Conversely, the metastatic incidence of the B77-3T3 sarcoma was much lower. Differences in lung implantation between the two lines turned out to be even greater when the number of colonies growing in the lung was evaluated. Organ distribution of cells after i.v. injection, tumorigenicity, growth rate in vivo and in vitro, plating efficiency in liquid medium and cloning efficiency in semi-solid agar medium were evaluated in the two lines. A strict correlation was found only between the metastatic potential and the capability of growth in 0.6% ("hard") agar. Such a correlation was supported by the isolation in "hard" agar of highly metastasizing subclones of the low-metastasizing B77-3T3 line.

Two approaches to obtaining low, extracellular deoxyribonuclease activity in cultures of heterocyst-forming cyanobacteria

Abstract: Six out of 158 axenic strains of heterocyst-forming cyanobacteria consistently failed to produce circles of clearing in agar medium containing DNA-methyl green When tested with [3H]DNA and coliphage λDNA, supernatant fluids from cultures of two of these strains [University of Texas Culture Collection (UTEX) strain 2014 and 19-6C-C] showed no detectable deoxyribonuclease activity, and such fluids from another two of the six, and four others, showed low but detectable deoxyribonuclease activity Covalently closed circular (plasmid) DNA was not detectably degraded by supernatant fluids from UTEX 2014 and 19-6C-C and from four of the other strains When λ DNA was incubated with whole cells of certain strains, a sereis of fragments of discrete size was produced, perhaps by cell-bound, periplasmic, restriction endonucleases Inclusion of one-tenth strength saline sodium citrate (SSC) in an eight-fold dilution of the medium of Allen and Arnon had little effect on growth of Anabaena variabilis American Type Culture Collection (ATCC) strain 29413 yet prevented all but slight degradation of plasmid pBR322 or of λ DNA

Gelatin agar medium for detecting gelatinase production by anaerobic bacteria.

Abstract: A new medium, Lombard-Dowell gelatin agar, was developed for detecting gelatinase activity by anaerobic bacteria. The medium contained: Trypticase (BBL Microbiology Systems), 5.0 g; yeast extract (Difco Laboratories), 5 g; sodium chloride, 2.5 g; sodium sulfite, 0.1 g; L-tryptophan, 0.2 g; L-cystine, 0.4 g; hemin, 10.0 mg; vitamin K1, 10.0 mg; agar, 20.0 g; D-glucose, 1.0 g; gelatin, 4.0 g; and distilled water to 1 liter. The pH was adjusted to 7.5. The medium was dispensed in 100- by 15-mm quadrant plastic dishes (5 ml per quadrant). To test for gelatinase activity, we inoculated the medium with a young enriched thioglycolate or chopped meat glucose broth culture or a turbid cell suspension in Lombard-Dowell broth, using a sterile cotton swab, and incubated it under anaerobic conditions for 48 h at 35 degrees C. The quadrants were then flooded with Frazier solution, and clear zones around the bacterial growth were recorded as positive for gelatinase activity. The new medium was tested with a variety of anaerobic bacteria, and the results were compared with data obtained with the conventional technique for detecting gelatinase activity. Overall, there was satisfactory agreement between the two tests in the detection of gelatinase activity, but the Lombard-Dowell gelatin agar tests was more rapid and somewhat more sensitive than the conventional test.

Anaerobic survival of clinical isolates and laboratory strains of Neisseria gonorrhoea: use in transfer and storage.

Abstract: Eleven laboratory strains and 67 clinical isolates of Neisseria gonorrhoeae were tested for the ability to survive during anaerobic incubation. The survival of the laboratory strains was dependent on auxotype, temperature, and cell density on agar plates. For both the laboratory strains and the clinical isolates, anaerobic survival was better at lower temperatures. We concluded that anaerobic incubation, for as long as 7 days, is useful when transporting or storing N. gonorrhoeae. Images

Primary culture media for routine urine processing.

Abstract: It has been recommended that routine microbiological processing of urine specimens include quantitative plating onto blood agar medium along with a selective and differential agar such as MacConkey agar for gram-negative organisms. Few data have been published to justify this combination. To evaluate the validity of this recommendation 2,553 midstream, clean-voided urine samples were quantitatively plated onto blood agar, MacConkey agar, and colistin-nalidixic acid agar, which is a selective medium for gram-positive organisms. The amounts of growth on each of the three media were compared. Results indicated that the best medium combination was colistin-nalidixic acid agar and MacConkey agar. The use of colistin-nalidixic acid agar instead of blood agar increased the detection of significant growth of enterococci, lactobacilli, and Torulopsis glabrata.

Presence of hydrogen peroxide in media used for cultivation of Neisseria gonorrhoeae.

Abstract: Defined complex media used for cultivation of Neisseria gonorrhoeae were tested for the presence of H2O2 by both a spectrophotometric and a polarographic assay H2O2 (35 to 165 microM) was present in all media tested In the defined media, H2O2 was generated by the interaction of cysteine with other amino acids The addition of the chelator 8-hydroxyquinoline prevented formation of detectable H2O2, suggesting that metal ions were necessary The persistence of H2O2 varied greatly among different media Medium components which affected the presence of H2O2 were pyruvate, oxalacetate, and sodium sulfite Sodium sulfite also generated superoxide radical In liquid medium containing H2O2, the endogenous gonococcal catalase present in an inoculum of about 2 X 10(7) colony-forming units/ml destroyed detectable H2O2 The long lag phase which resulted from a 10-fold lower inoculum could not be shortened by the addition of exogenous catalase Small amounts of residual H2O2 in agar plates of complex medium affected the viability of gonococci which had been suspended in buffer and incubated for 60 min at 37 degrees C Addition of pyruvate or catalase increased viable counts in medium containing H2O2

Detection of heat-labile-enterotoxin-producing colonies of Escherichia coli and Vibrio cholerae by solid-phase sandwich radioimmunoassays.

Abstract: A solid-phase sandwich assay that was able to differentiate heat-labile-enterotoxin-producing colonies of Escherichia coli and choleratoxin-producing colonies of Vibrio cholerae from nontoxigenic colonies is described. Flexible polyvinyl chloride plastic film coated with antibody molecules was allowed to react with partially lysed bacterial colonies in a standard petri dish. The immobilized antigen on the plastic film was then labeled with radioiodinated antibody. Autoradiography identified antigen-containing colonies. As little as 5 to 25 pg of pure toxin contained in a 3- to 4-mm-diameter circle was reliably detected by this method. The synthesis of heat-labile enterotoxin and choleratoxin by cells growing on selective media such as eosin methylene blue agar, MacConkey agar, Endo agar, and thiosulfate-citrate-bile salts-sucrose agar was demonstrated. The method appears to be suitable for large-scale surveys.

Influence of agar and sucrose on the behaviour of dormant apple embryos cultured in vitro

Abstract: SUMMARY Dormant as well as completely after-ripened embryos of Pyrus malus L. var. Golden Delicious were cultured aseptically on media of different compositions. Distilled water was used as the simplest medium. The influence of the addition of agar (8 g 1−1), of mineral substances (macro-and micro-elements of the Heller's medium) and of sucrose (10 or 20 g 1−1) was studied. On the agar-solidified media, three different modes of culture were used, depending upon the nature of the contact between the embryo and the medium. The criteria used to evaluate the depth of dormancy were the germination percentages and the progression in the greening of the cotyledons. Completely after-ripened embryos behaved similarly on all the media used whatever the mode of culture. Dormant embryos behaved differently depending upon the composition of the medium and of the mode of culture. Dormancy was always deeper on agar-solidified media than on liquid media and in the presence of sucrose than in its absence. In order to determine whether these differences in behaviour were due to quantitative differences in the leaching of free abscisic acid (ABA) into the medium, a two-step culture method was introduced, using [14C]ABA. Dormant embryos were cultured first on water-agar containing 10−5 M (±) [2-14C]ABA (355 KBq μmol−1), then on one of the following media deprived of ABA: water-sucrose-agar, water-agar, water. Observations during the first culture indicated that the amount of [14C]ABA absorbed was partially metabolized after only 2 days of uptake. During the course of the second culture, part of the original radioactivity of the embryos (4 days [14C]ABA uptake) was released into the medium. Leaching was much greater and lasted longer on water than on media solidified with agar: it does not depend upon the volume of the liquid used (3 or 15 ml). The presence of sucrose (20 g 1−1) in the agar medium does not modify the amounts of 14C-radioactivity released. The main part of the radioactivity released in water and in water-agar was shown to be ABA.

Comparison of media in the Anaerobe-Tek and Presumpto plate systems and evaluation of the Anaerobe-Tek system for identification of commonly encountered anaerobes.

Abstract: Using a variety of sporeforming and nonsporeforming anaerobic bacteria, we compared 10 differential agar media of the Anaerobe-Tek (A/T) system recently marketed by Flow Laboratories, Inc. (McLean, Va.) with 10 comparable media in Presumpto quadrant plates (Presumpto 1, 2, and 3) developed by the Centers for Disease Control Anaerobic Bacteria Branch. The A/T identification system was evaluated by comparing the species identity of anaerobes determined as recommended by the manufacturer9s instruction manual with the identity of the strains obtained by the Centers for Disease Control Anaerobe Reference Laboratory by using conventional procedures. We also compared reactions obtained with the Presumpto plates with a chopped meat glucose broth culture as a source of inoculum with those obtained by using a turbid cell suspension from growth on blood agar as inoculum. The agreement of results for the 16 characteristics compared ranged from 92.8 to 100%. Comparison of test results obtained with 10 media in the Presumpto plate and A/T systems from the examination of 223 strains of anaerobes, representing 54 different taxa, showed the following agreement between A/T and CDC systems: catalase production, esculin hydrolysis, glucose fermentation, and lecithinase production (100%); inhibition of growth by bile agar (99.6%); lipase production (99%); DNase (98.7%); fermentation of lactose and mannitol (98.2%); starch hydrolysis (96.9%); gelatin hydrolysis (96.4%); and casein hydrolysis (94.6%). Of the 204 strains of common anaerobes tested with the A/T system, only 70% were correctly identified to the species level. However, several strains could have been identified correctly with the A/T system if data on certain other characteristics had been included in the A/T data base.

Selection and fusion of auxotrophic protoplasts of Candida albicans.

Abstract: Auxotrophic mutants of C. albicans obtained by the method described by Henson and McClary (1979) were conditioned in a tris buffered EDTA-dithiothreitol solution then converted to protoplasts by suspension in osmotically stabilized buffer containing β-glucuronidase. Complementary protoplasts were mixed in an osmotically stabilized polyethylene glycol solution and at appropriate times were plated respectively in osmotically stabilized minimal and complete agar media. From colony counts resulting from growth on the respective media, the proportion of fused complementary protoplasts (prototrophic colonies) to the total viable number of colony forming units was determined. Stability tests of selected colonies from the minimal and complete agar revealed multiple revertants, but the numbers declined to low frequencies upon repeated selective plating and isolation. Acridine orange staining of cultures thus stabilized revealed various sizes of cells with their numbers of nuclei (DNA-staining regions) varying from one to five, such that it was not determined whether the prototrophic cultures were monokaryons, heterokaryons or a mixture of the two.

Glutamate as a differential nitrogen source for the characterization of acetylene‐reducing Rhizobium strains

Abstract: A majority (36 of 44) of Rhizobium japonicum strains tested reduced acetylene asymbiotically when grown on an agar medium containing 0.1% (w/v) L-glutamate as a sole nitrogen (N) source. Glutamate as N source led to pinpoint colonies and uniform glutamine synthetase activity of three selected, slow-growing acetylene-reducing strains (R. japonicum L-259 and 110 and a cowpea-type Rhizobium 32H1). The three test strains were characterized further by antibiotic resistance, colony type, cellular morphology, and differential growth on different N sources. The evidence suggests that, in an agar medium, glutamate creates a growth condition leading to acetylene reduction activity, pinpoint colonies and pleomorphism.

Test Tube Method for Counting Bifidobacteria in Commercial Dairy and Pharmaceutical Bacteria Products

Abstract: A culture method was developed suitable for selective cell counting of bifidobacteria in Japanese commercial dairy and pharmaceutical bacteria products.1) A dissolved agar medium was added at 45°C to the bacterial suspension in the bottom of a test tube to achieve a deep culture medium, then the culture was incubated. The present culture method in the agar column, tentatively called the test tube method by the authors, was suitable for carrying out anaerobic incubation for viable cell counting of bifidobacteria.2) Modified Garche's agar with lithium chloride (MGL agar) or with lithium chloride and penicillin G potassium (MGLP agar) was demonstrated to be a suitable medium for the selective cell counting of bifidobacteria by the test tube method described, above since it discriminated the growth of lactobacilli and streptococci.3) Bifidobacteria in commercial dairy and pharmaceutical bacteria products were determined satisfactorily by the present test tube method with MGL agar or with MGLP agar, except for products which contained enterococci.

[48] The Halobacterium group: Microbiological methods

Abstract: Publisher Summary This chapter describes microbiological methods for the isolation, cultivation, and maintenance of Halobacterium strains. It is found that phenotypic instabilities are correlated with complex alterations in Halobacterial plasmid DNA sequences. These observations suggest that rigorous criteria should be established to monitor constantly each wild-type halobacterial strain for genotypic and phenotypic purity. Maintenance or cultivation of halobacterial strains under inappropriate conditions may allow the inadvertent selection of spontaneously occurring pseudo-wildtype strains that are uniquely adapted to a particular laboratory environment. Halobacterium strains can be maintained on RM agar plates for 6 months to 1 year. The plates should be sealed tightly with parafilm to prevent desiccation. RM agar slants tightly sealed with parafilm and stored at 4° preserves Halobacterium strains for 1–2 yrs. Halobacterium strains can be isolated and cultured from natural environments by a variety of techniques. Liquid medium can be prepared by centrifuging the natural medium at 6000 g for 30 min followed by heat or membrane sterilization. Solid medium can be prepared using 1.5% w/v Noble Agar. More rapid growth in these natural media is obtained by supplementation with 0.5% (w/v) peptone.