Showing papers on "Agar plate published in 1988"
TL;DR: Control of gray mold and reduction in blue mold was obtained on Golden Delicious apples and Bosc pears protected with Pseudomonas cepacia isolated from apple leaves and an effective antifungal compound was isolated from the bacterial cells and culture medium.
Abstract: Control of gray mold, caused by Botrytis cinerea, and reduction in blue mold, caused by Penicillium expansum, was obtained on Golden Delicious apples and Bosc pears protected with Pseudomonas cepacia isolated from apple leaves. The bacterium strongly inhibited fungal growth during in vitro screening on nutrient yeast dextrose agar medium. An effective antifungal compound was isolated from the bacterial cells and culture medium. This compound, identified as a pyrrolnitrin, inhibited growth of both fungi at a concentration of 1 mg/L during an agar diffusion test in vitro
268 citations
TL;DR: A modification of Skirrow's medium was developed; cefsulodin was substituted for polymyxin, and amphotericin B was added to inhibitCandida spp.
Abstract: Contaminating bacteria from the oropharynx and bacteria that colonise the stomachs of patients with a high gastric pH impede the isolation ofCampylobacter pylori from gastric biopsy specimens. Commercially available selective supplements are inhibitory to this organism and therefore a specific selective medium is needed for isolation. Potential selective agents were evaluated for their activity against 97 strains ofCampylobacter pylori. A modification of Skirrow's medium was developed; cefsulodin (5 mg/l) was substituted for polymyxin, and amphotericin B (5 mg/l) was added to inhibitCandida spp., a common contaminant of the stomach. No strains ofCampylobacter pylori were inhibited by theCampylobacter pylori selective medium and it supported the growth of all strains compared with the biopsy urease test and Gram stained smear. Colonies were slightly larger and more easily recognised on the new medium compared with those grown on chocolate blood agar. This medium greatly improves the isolation ofCampylobacter pylori and could be used alone, without a non-selective medium.
128 citations
TL;DR: In this paper, the oxidizing power of rice roots was observed in narrow transparent root boxes containing different media, such as agar medium, soil filtrate, soil carbon dioxide, and water.
Abstract: The oxidizing power of rice roots was observed in narrow transparent root boxes containing different media. Plants precultivated in nutrient solution were embedded in semisolid agar medium to observe oxidation of ferrous iron cations and leuco methylene blue as well as solubilization of ferrous sulfide. In the presence of ferrous sulfate reddish brown coloration due to formation of ferric oxide/hydroxide was observed around the roots and on the root surface during one day of incubation. When agar medium blackened by ferrous sulfide was used, the root zone became transparent. Within a few hours leuco methylene blue was oxidized to methylene blue on and near the roots. Furthermore, seedlings were grown in agar medium containing ferrous sulfide inoculated with soil filtrate. Besides diffuse ferric iron precipitation, iron was also deposited on spherically shaped structures in the rhizosphere and near the agar surface as well as in slimy layers appearing on the root surface. The spherical structures and slimy layers were obviously bacterial colonies extending with time. As the roots grew old, parts of them turned black. In the rhizosphere, black spots occurred resembling colonies of sulfate-reducing bacteria. Rice was also grown in sand supplemented with nutrients and iron sulfide. While root growth was straight in agar, it was twisted in the sand medium. Again, heavy ferric iron deposition occurred on the root surface. On older root parts the lateral roots became blackish. The results suggest participation of bacteria in ferric iron deposition in the rhizosphere of rice.
96 citations
TL;DR: A new method for the detection of Strongyloides larvae was established using a small amount of stool placed in the center of an agar plate and was incubated at 37°C for 24 hr, and characteristically aligned bacterial colonies or furrows left by crawling StrongylOides larvae appeared on the agar surface are the positive findings.
Abstract: A new method for the detection of Strongyloides larvae was established. A small amount of stool was placed in the center of an agar plate and was incubated at 37°C for 24 hr. Characteristically aligned bacterial colonies or furrows left by crawling Strongyloides larvae appeared on the agar surface are the positive findings. The larvae gathered in a well made on positive plate were identified. By using this method, Strongyloides was detected in 46 cases (4.5%) out of 1, 017 healthy adults. Whereas, it was detected in 0 and 3 cases (0 and 0.3%) by direct stool smear method and filter paper technique, respectively. Examination of 246 cases by this agar plate method and formalinether method (MGL) revealed that 14 cases (5.7%) were positive by the former and 2 cases (0.8%) by the latter. Agar plate method is not laborious nor expensive, and recommendable for mass examination and for the detection of asymptomatic carriers.
79 citations
TL;DR: Values obtained for enumeration of two strains of E. coli recovered from artificially inoculated raw minced chicken indicate that X-GLUC at 50 μg/ml was as effective as MUG in an agar medium.
78 citations
TL;DR: Heating ofListeria monocytogenes (Scott A strain) in potassium phosphate buffer at 52°C for 1 h led to injury, with the heat-injured cells failing to produce colonies on agar medium containing 5% NaCl.
Abstract: Heating ofListeria monocytogenes (Scott A strain) in potassium phosphate buffer (0.1 M, pH 7.2) at 52°C for 1 h led to injury, with the heat-injured cells failing to produce colonies on agar medium containing 5% NaCl. The detection of injury was based on the use of differential media: plating on tryptose phosphate broth+2% agar and 1% sodium pyruvate (TPBA+P) and on tryptose phosphate broth+2% agar and 5% NaCl (TPBA+S). Only non-injuredListeria formed colonies on TPBA+S whereas both heat-injured and non-injured cells formed colonies on TPBA+P. The bacterial count on TPBA+P minus that on TPBA+S represents the extent of heat injury. A large number of selective agars were tested and compared to TPBA+P for their ability to support repair and colony formation of heat-injuredL. monocytogenes. Media containing 0.025% phenylethanol, 0.0012–0.0025% acriflavin, 0.1–0.2% potassium tellurite, 0.001% polymyxin B sulfate, 5% NaCl or a combination of these ingredients were detrimental to the recovery of heat-injuredL. monocytogenes. Media currently in use forL. monocytogenes are not satisfactory for the recovery of injured cells.
75 citations
TL;DR: The results suggest that the conversion process which occurs between virulent andAvirulent forms of L. pneumophila is a one-way phenomenon from virulence to avirulence and that stable avirulent derivatives can be isolated.
Abstract: Previous investigations have shown that Legionella pneumophila converts from virulence to avirulence after passage on supplemented Mueller-Hinton (SMH) agar and may convert back to virulence after passage in guinea pigs. However, there is no additional information concerning the apparent interconversion of virulent and avirulent derivatives of L. pneumophila cultures. We investigated the stability of a parental virulent culture and its avirulent derivatives and the growth and viability of these cultures on charcoal-yeast extract (CYE) and SMH agars. Avirulent derivatives of a highly virulent L. pneumophila culture were obtained by passage of the virulent parent culture on SMH agar. The only time a virulent L. pneumophila culture was recoverable from an avirulent culture was when the avirulent culture was derived from a saline suspension of a virulent culture which had been passaged only five times on SMH agar. When an avirulent culture was derived from a virulent culture passaged 25 times on SMH agar or from an isolated colony which grew on a SMH agar plate, we were unable to recover a virulent culture after successive passage through guinea pigs. These results suggest that the conversion process which occurs between virulent and avirulent forms of L. pneumophila is a one-way phenomenon from virulence to avirulence and that stable avirulent derivatives can be isolated. Furthermore, our findings suggest that SMH agar acts as a selective medium for the growth of avirulent L. pneumophila, and growth on SMH agar may be a phenotypic marker for avirulence. Virulent cells, although unable to grow on SMH agar, may remain viable for several passages on SMH agar and propagate when inoculated into guinea pigs.
62 citations
TL;DR: Ariflavine-ceftazidime selective agar medium proved to be a highly sensitive medium to recover Listeria spp.
Abstract: Food-associated outbreaks of human listeriosis have emphasized the importance and necessity of screening food for the presence of Listeria isolates-selective agar medium combining acriflavine (10 mg/liter) with ceftazidime (50 mg/liter) was developed. A total of 1,099 cheese production specimens were cultured, from which 157 Listeria isolates. (14.3%) grew. When compared with modified McBride agar, the acriflavine-ceftazidime agar recovered more Listeria isolates (98 versus 65%, P less than 0.001) more rapidly (57% after 48 h of incubation of the enrichment broth versus 35%, P less than 0.01) and in greater amounts. Acriflavine-ceftazidime selective agar medium proved to be a highly sensitive medium to recover Listeria spp. from heavily contaminated food products.
59 citations
TL;DR: A medium was created which reduced growth of Neisseria spp.
Abstract: Several semiselective media for Branhamella catarrhalis have been proposed. These media allow growth of all members of the family Neisseriaceae, and further differentiation is necessary. By addition of 10 micrograms of acetazolamide, a carbonic anhydrase inhibitor, per ml and incubation in air, a medium was created which reduced growth of Neisseria spp. When saliva samples from 178 healthy schoolchildren were screened for the presence of B. catarrhalis, the carrier rate for this organism was estimated to be 48.9% with the selective medium compared with 12.4% when a semiselective medium, which contains only 10 micrograms of vancomycin, 5 micrograms of trimethoprim, and 2 micrograms of amphotericin B per ml, was used and 6.2% when a nonselective blood agar plate was used. The number of Neisseria spp. isolated dropped from 297 on the semiselective agar to 55 on the selective agar.
51 citations
TL;DR: The new model for specific growth rate (length) derived from agar cultures is particularly suited to those situations where a growth-modifying agent alters the branching frequency and the distance between branch points.
Abstract: Cadmium reduced the growth rate of Paxillus involutus in pure cultures either on agar or liquid medium. On Cd-containing agar most of the mycelium grew submerged rather than on the surface as occurs on Cd-free agar. Cadmium increased hyphal density by both increasing the number of laterals at a branch point and decreasing the distance between branch points. These variables were included in a new model to determine the specific growth rate on the basis of mycelial length for the fungus growing on agar. The degree to which Cd reduced the specific growth rate was the same whether based on mycelial length from agar plates according to the new model or on mycelial mass from a liquid medium. The new model for specific growth rate (length) derived from agar cultures is particularly suited to those situations where a growth-modifying agent alters the branching frequency and the distance between branch points.
48 citations
TL;DR: The hemolytic activity of toxic shock syndrome isolates of Staphylococcus aureus is enhanced when agarose is substituted for agar in blood plates or when strains are grown in liquid culture in the presence of 20% (vol/vol) CO2 in air.
Abstract: The hemolytic activity of toxic shock syndrome isolates of Staphylococcus aureus is enhanced when agarose is substituted for agar in blood plates or when strains are grown in liquid culture in the presence of 20% (vol/vol) CO2 in air. Hemolytic activity of a representative panel of toxic shock syndrome isolates was rigorously assessed both on blood agar and in liquid culture to unequivocally identify the predominant hemolysins produced. As determined by isoelectric focusing and Western immunoblotting, 15 of 15 TSS isolates produced gamma-lysin and 10 of 15 produced delta-lysin. None produced beta-lysin, and only 2 of 15 produced alpha-lysin. The low rate of alpha-lysin production was a most striking characteristic, since all strains were found to have the alpha-lysin gene by Southern blot hybridization.
TL;DR: Overall, LPM agar was the most suitable of the media tested even though it was inhibitory to Listeria grayi and Listersia murrayi, and was the best overall since Scott A was inhibited by MVJ.
Abstract: The suitability of seven media for the enumeration of Listeria spp. was evaluated at 30 degrees C for 48 h. The media tested were (i) the original McBride Listeria agar formulation (with glycine); (ii) modified McBride agar containing glycine anhydride; (iii) LiCl-phenylethanol-moxalactam (LPM) agar; (iv) acriflavine-ceftazidime agar; (v) Rodriguez isolation agar (RISA); (vi) modified Vogel-Johnson (MVJ) agar; (vii) cyclohexanedione-nalidixic acid-phenylethanol agar; and tryptose agar as control. A total of 66 organisms were used including 11 Listeria monocytogenes strains and 5 other Listeria spp. For L. monocytogenes strains only, all media performed highly similarly. Of the other Listeria spp., only two grew on MVJ agar and three each grew on LPM and RISA. Only LPM agar inhibited the 50 non-listeriae, including five yeasts, while MVJ agar inhibited all but one yeast. The McBride Listeria agar formulation that contained glycine anhydride was less selective than the original. When pure cultures of 10 bacteria (including one L. monocytogenes strain) were combined and plated on four media, L. monocytogenes colonies were easiest to enumerate on MVJ agar, followed by LPM and RISA. These media ranked in the same order when plated with homogenates of various foods to which was added L. monocytogenes Scott A, but LPM agar was the best overall since Scott A was inhibited by MVJ. Upon microscopic examination of listerial colonies from the plating media, atypical cell morphology was noted with cells being about twofold in size on LPM, MVJ, and acriflavine-ceftazidime agars. Overall, LPM agar was the most suitable of the media tested even though it was inhibitory to Listeria grayi and Listeria murrayi.
TL;DR: In this article, eleven media were evaluated for their suitability in the selective isolation of Aeromonas hydrophila from natural water samples and six mediums were selected for evaluation as recovery selective media on the basis of their efficiency.
Abstract: Eleven media were studied for their suitability in the selective isolation of Aeromonas hydrophila. Preliminary results showed that five of them (inositol-brilliant green-bile salts agar, bile salts-brilliant green agar, Rimler-Shotts agar, xylose-sodium deoxycholate-citrate agar, and dextrin-fuchsin-sulfite agar) allowed the growth of several microorganisms that are usually present in the same samples in which A. hydrophila is found. Six media (mA agar, modified Rimler-Shotts agar, DNase-toluidine blue-ampicillin agar, Pril-xylose-ampicillin agar, MacConkey-trehalose agar, and starch-bile salts agar) were selected for evaluation as recovery selective media on the basis of their efficiency in the isolation of A. hydrophila from natural water samples. mA agar showed the best recovery rate and also an acceptable specificity, but its selectivity was low. Another medium that can be considered is DNase-toluidine blue-ampicillin agar, which showed good accuracy, but its specificity was low.
TL;DR: The causal agent of bacterial gall of carrots (Daucus carota L.) is named Rhizobacter daucus gen. nov., sp.
Abstract: The causal agent of bacterial gall of carrots (Daucus carota L.) is named Rhizobacter daucus gen. nov., sp. nov. and is placed in the family Pseudomonadaceae. This bacterium is a gram-negative, capsulated, straight or curved rod with polar flagella or lateral flagella or both and a cell diameter of 0.9 to 1.3 μm. The bacterial cells accumulate poly-β-hydroxybutyrate granules. Glucose is metabolized oxidatively. The bacteria are positive for oxidase and catalase reactions and are susceptible to vibriostatic agent 0/129 phosphate. Colonies grown on dilute potato-peptone-glucose agar medium are white, tough, and highly plicated; when grown on dilute yeast extract-peptone-glucose agar medium, they are yellowish white. No water-soluble pigment is produced. In liquid media the bacterium grows as abundant, primarily globular floes. R. daucus can use various kinds of carbon sources, including sugars, polysaccharides, and sugar alcohols, but not benzene derivatives. The guanine-plus-cytosine content of the deoxyribonucleic acid is 66.9 to 70.6 mol%. The ubiquinone is Q8. This bacterium induces gall formation on roots of carrots. Strain H6 is designated the type strain and has been deposited with the American Type Culture Collection (ATCC 43778) and the International Collection of Microorganisms from Plants, New Zealand (ICMP 9400) together with four other reference strains (ATCC 43776, ATCC 43777, ATCC 43779, and ATCC 43780; ICMP 9398, ICMP 9399, ICMP 9401, and ICMP 9402).
TL;DR: A new medium, called RAPAMY agar, has been elaborated for the isolation from and the enumeration of Listeria spp.
TL;DR: A collection of 198 clinical isolates of strains belonging to the tribe Proteeae was examined for haemolytic activity on blood agar and in Brain Heart Infusion Broth, finding most strains of the Proteus spp.
Abstract: A collection of 198 clinical isolates of strains belonging to the tribe Proteeae was examined for haemolytic activity on blood agar and in Brain Heart Infusion Broth. The strains were of diverse bacteriocin and O-antigenic types and from a wide variety of sources. They included representatives of all species of Morganella, Proteus and Providencia. Approximately half of the M. morgani strains were haemolytic on blood agar. This activity was not associated with any particular bacteriocin type. The haemolysin was also produced during exponential growth in broth and was thermolabile and calcium dependent. All P. mirabilis strains and some P. vulgaris strains were non-haemolytic on blood agar. However, most strains of the Proteus spp., irrespective of their bacteriocin and antigenic type, produced, over a short period during exponential growth in broth, a heat-stable, cell-associated calcium-independent haemolysin. A smaller proportion of P. vulgaris and P. penneri strains produced, in addition, a thermolabile, calcium-dependent haemolysin which was associated with the formation of large haemolytic zones on blood agar. The relationship of these haemolysins to Escherichia coli haemolysin and their possible role in virulence is discussed. Haemolysin production was not found in any of the 74 strains of four species of Providencia.
TL;DR: Simple colorimetric tests showed that gaseous diffusion was substantially faster through 3.5% porous agar than through the 1% (w/v) non-porous agar frequently used for growing plants under sterile conditions.
Abstract: Porous nutrient agar was prepared under sterile conditions by drawing molten 3.5% (w/v) nutrient agar into a plastic syringe, allowing it to set, extruding it into a test tube and giving the tube a firm flick. Simple colorimetric tests showed that gaseous diffusion was substantially faster through 3.5% (w/v) porous agar than through the 1% (w/v) non-porous agar frequently used for growing plants under sterile conditions. Root systems ofTrifolium subterraneum grew 80–90% larger in porous than in non-porous agar.
Journal Article•
TL;DR: Of 271 Gram-positive, catalase-negative, chain-forming cocci isolated from crevicular and supragingival plaques of 22 adults, 71 stains were clustered as Streptococcus milleri by testing 23 physiological characters.
Abstract: Of 271 Gram-positive, catalase-negative, chain-forming cocci isolated from crevicular and supragingival plaques of 22 adults, 71 stains were clustered as Streptococcus milleri by testing 23 physiological characters. Most of the oral S. milleri strains were nonhaemolytic and formed minute smooth colonies on glucose and sucrose agar plates, while some of the clinical strains were alpha-haemolytic, forming rough colonies on Carlsson's MC agar plate as well as carrying the Lancefield group antigens C, F or G. The strains were divided into two biotypes, and further into six subtypes by their abilities to ferment maltose, salicin and/or lactose. Distribution of the varieties according to the haemolytic, colonial and serological properties among the oral isolates generally corresponded to the tentative biological types of S. milleri.
TL;DR: The technique successfully differentiated the aflatoxigenic potentials of Aspergillus isolates with aflatoxin concentrations in agar media with a direct technique that quantifies the fluorescence of agar containing a flatoxins.
Abstract: Aflatoxin concentrations in agar media were estimated with a direct technique that quantifies the fluorescence of agar containing aflatoxins. Tubes containing 5 ml of an agar medium inoculated with spores of aflatoxin-producing Aspergillus isolates were incubated for 3 days at 30 degrees C and set in a carriage specifically designed to carry culture tubes in a scanning densitometer. Fluorescence (450 nm and above) was elicited in the agar by UV light (365 nm) and photometrically measured. Agar fluorescence directly correlated (r2 = 0.89 +/- 0.05, P less than 0.001) with the concentration of aflatoxin within the range 0 to 18.7 micrograms/g. The lowest aflatoxin concentration detected was 50 ng/g. The technique successfully differentiated the aflatoxigenic potentials of Aspergillus isolates.
TL;DR: The avian strain P-1059 of Pasteurella multocida was grown on blood agar, on dextrose-starch agar (DSA), or in Heddleston's hydrogen sulfide test broth and pili were found on the circumference of the cells grown on either agar or broth medium.
Abstract: SUMMARY. The avian strain P-1059 of Pasteurella multocida was grown on blood agar (BA), on dextrose-starch agar (DSA), or in Heddleston's hydrogen sulfide test broth. Cells were examined for the presence of pili using electron microscopy after staining with phosphotungstic acid, and they were examined for capsule after ruthenium red staining. Pili were found on the capsulated iridescent type, P-10591, and on two non-capsulated variants, the blue, P-1059B, and the gray, P-1059G. Many cells grown on BA were heavily piliated. In contrast, fewer cells grown on DSA had pili, and piliation was only slight to moderate. The P-10591, P-1059B, and P- 1059G produced pellicles when grown on broth medium. Pili were found on the circumference of the cells grown on either agar or broth medium. Occasionally a pilus connecting two cells was seen on cells cultured in broth. Cultivation of the P-10591 on DSA containing the iron-chelating agent a,a'-bipyridyl produced a non-capsulated blue variant. The non-capsulated variant reverted to P-1059I when grown on BA but did not revert when grown on DSA.
TL;DR: R. oligosporus was chosen as the more suitable organism for future studies of the protein enrichment of cassava by solid-state fermentation, although growth was stimulated by the addition of yeast extract and peptone.
Abstract: Colony radial growth rates of Rhizopus oligosporus and Aspergillus oryzae were compared under various conditions on agar plates containing cassava starch. Both organisms grew well on cassava starch as their sole source of carbon and energy, although growth was stimulated by the addition of yeast extract and peptone. Neither organism utilized ungelatinized starch effectively. The optimum initial pH for R. oligosporus was 7, although good growth was obtained at pH 5 when ammonium sulfate was partially replaced by urea. A. oryzae grew well over a range of initial pH values from 5 to 8. Growth of R. oligosporus was inhibited by NaCl concentrations above 0.5% (w/v) while A. oryzae was unaffected up to 4% NaCl. The best colony radial growth rate obtained for R. oligosporus was 1.01 mm/h, which was far superior to that obtained for A. oryzae (0.29 mm/h). R. oligosporus was chosen as the more suitable organism for future studies of the protein enrichment of cassava by solid-state fermentation.
TL;DR: The results suggest that ABA is superior to the other media evaluated for the isolation of Aeromonas strains from stool specimens, but optimal recovery of the organism may require the use of more than one medium.
Abstract: The performance of four media for the isolation of Aeromonas strains from stool specimens, the importance of ampicillin-susceptible Aeromonas strains in the selection of culture media, and the usefulness of beta-hemolysis in screening blood-containing media for Aeromonas strains were evaluated in two phases. In the first phase, 36 of 1,672 stool specimens yielded Aeromonas isolates. Ninety-seven percent of the isolates were detected on blood agar containing 20 micrograms of ampicillin per ml (ABA), and 47% were detected on MacConkey agar containing 100 micrograms of ampicillin per ml and 1% Tween 80. In the second phase of the study, 43 of 1,924 stool specimens yielded Aeromonas isolates. Fifty-one percent of the isolates were detected on blood agar and on modified cefsulodin-Irgasan-novobiocin agar, and 84% were detected on ABA. The combination of ABA and modified cefsulodin-Irgasan-novobiocin agar provided 100% recovery of the Aeromonas isolates encountered. All of the Aeromonas isolates detected on blood agar were also detected on ABA, and 89% of the Aeromonas isolates detected on these media were beta-hemolytic. These results suggest that ABA is superior to the other media evaluated for the isolation of Aeromonas strains from stool specimens, but optimal recovery of the organism may require the use of more than one medium. The results also suggest that the occurrence of ampicillin-susceptible strains is not a limitation on the use of ABA, but at least 10% of Aeromonas isolates will be missed if beta-hemolysis is used to screen ABA plates for these organisms.
TL;DR: Several strains of agar-degrading bacteria capable of fixing N2 were isolated from seawater and eelgrass-bed sediment in Aburatsubo Inlet, Kanagawa, Japan, during the summer of 1986 and were demonstrated to fix N2 anaerobically using agar as the sole carbon source.
Abstract: Summary: Several strains of agar-degrading bacteria capable of fixing N2 were isolated from seawater and eelgrass-bed sediment in Aburatsubo Inlet, Kanagawa, Japan, during the summer of 1986. All strains were Gram-negative, facultatively anaerobic, and required NaCl for growth. They were straight or slightly curved rods and were motile in liquid medium by means of a single polar flagellum. These characteristics as well as the G+C contents of their DNA (44.7-46.1 mol%) placed them in the family Vibrionaceae. These strains produced extracellular agarase on agar medium, yielding reducing sugars and acids as the end products. They expressed significant nitrogenase (acetylene reduction) activities after a few hours of incubation under anaerobic conditions. They utilized combined nitrogen sources both aerobically and anaerobically, but fixed N2 only under anaerobic conditions. Neither yeast extract nor vitamins were required for N2 fixation. These strains were demonstrated to fix N2 anaerobically using agar as the sole carbon source.
TL;DR: High-molecular-weight proteins similar to those produced by these strains in an iron-limited chemically defined medium were detected in cells grown on the surface of various agar media, but these proteins were not produced or were only poorly expressed by the corresponding broth cultures or by cells grown an agar supplemented with iron.
Abstract: The outer membrane proteins of Escherichia coli and Pseudomonas aeruginosa grown in a number of conventional laboratory media were examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) High-molecular-weight proteins similar to those produced by these strains in an iron-limited chemically defined medium were detected in cells grown on the surface of various agar media. In contrast, these proteins were not produced or were only poorly expressed by the corresponding broth cultures or by cells grown an agar supplemented with iron. A catecholic substance could be detected in DST agar extracts subsequent to bacterial growth which was produced to a lesser extent in IST agar and in broth cultures.
TL;DR: Two species of Panagrolaimus found in agar cultures begun in 1981 with nematodes extracted from a sea birds nest on the island of Surtsey coexistence could probably be explained by differences in pattern of colonizing the plates and in different competitive ability and survival during different phases of population development.
Abstract: Two species of Panagrolaimus were found in agar cultures begun in 1981 with nematodes extracted from a sea birds nest on the island of Surtsey. They were provisionally identified as P. superbus and P. detritophagus. Both species had survived successive subculturing and coexisted on the agar plates for about five years. In order to investigate the conditions for this coexistence, the animals were isolated into monospecific agar cultures. P. superbus appeared to be better than P. detritophagus in establishing and starting population development in cultures inoculated with only a few individuals. P. suberbus initially dispersed more rapidly over the agar surface than P. detritophagus, which had a stronger tendency to aggregate in fresh cultures. Both species reached the phase of exponential growth 14-22 days after inoculation. When cultured sympatrically numbers of both species were lower than when cultured alone. The coexistence could probably be explained by differences in pattern of colonizing the plates and in different competitive ability and survival during different phases of population development.
TL;DR: Embryos of all sizes and of both genotypes of pea responded in a similar manner to increasing sucrose concentrations and optimum development was obtained when embryos were cultured in liquid culture at a high osmotic pressure followed by growth on an agar medium at low osmosis pressure.
Abstract: Three different culture media have been examined for their ability to support growth in culture of embryos of two pea lines near-isogenic except for the r-locus. Embryos showed a greater increase in fresh weight on a medium containing 10% sucrose and a high level of a mixture of amino acids than on either one containing an equivalent amount of glutamine as the sole nitrogen source or one containing both inorganic nitrogen and a low level of glutamine. Small embryos (up to 10 mg fresh weight) showed the greatest relative increase in fresh weight. Decreasing the osmotic pressure of an agar medium by lowering the sucrose content to 2% and reducing the concentration of amino acids induced precocious germination. Shoot growth was more sensitive than root growth to increasing sucrose concentrations and optimum development was obtained when embryos were cultured in liquid culture at a high osmotic pressure followed by growth on an agar medium at low osmotic pressure. Alternatively, precocious germination could be induced by removing the cotyledons. Embryos of all sizes and of both genotypes of pea responded in a similar manner.
TL;DR: The use of the inhibitor made it possible to detect penicillinase or type Ic cephalosporinase producers and proved that the PADAC plate might be a useful tool permitting easy, semiquantitative determination of beta-lactamase activity.
Abstract: A new beta-lactamase assay method with agar plates containing pyridinium-2-azo-p-dimethylaniline chromophore (PADAC) (50 microM), a beta-lactamase-labile, chromogenic cephalosporin, was examined. On the PADAC plates inoculated with beta-lactamase-producing gram-negative bacteria (10(4) CFU per spot) and incubated at 37 degrees C, a yellow zone showing hydrolysis of PADAC by beta-lactamase was formed around the colony. The zone diameter increased with incubation time. Examination with Enterobacter cloacae GN7471 revealed that beta-lactamase activity was present in the agar around the colony, decreasing exponentially with increasing distance from the colonial margin; this suggests that the PADAC hydrolysis zone is formed by an extracellular enzyme. At 18 h, significant correlations were obtained between the zone diameters of the 10 species (clinical isolates) examined and their periplasmic beta-lactamase activities determined spectrophotometrically. The addition of clavulanic acid (0.5 to 10 micrograms/ml) inhibited zone formation on the PADAC plates inoculated with type IIIa, Va, Vb, PSE-1, and Ic beta-lactamase producers. When the clinical isolates were tested on plates with clavulanic acid (2 micrograms/ml), inhibition was observed in 41 to 58% of the Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa isolates and in all isolates of Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus vulgaris. Thus, the use of the inhibitor made it possible to detect penicillinase or type Ic cephalosporinase producers. These results proved that the PADAC plate might be a useful tool permitting easy, semiquantitative determination of beta-lactamase activity.
Journal Article•
TL;DR: The results suggest that isoelectric focusing in conjunction with sensitive enzyme systems can be used to detect phenotypic variation between individual nematodes from the same population.
Abstract: Infection of roots transformed with Agrobacterium rhizogenes by Meloidogyne incognita and Heterodera schachtii second-stage juveniles was established in bicompartmental petri dishes. One compartment contained the Murashige and Skoog agar medium and the nematicide oxamyl, and the other compartment contained water agar. Transformed roots of carrot, tomato, alfalfa, cowpea, rape, and sugarbeet were placed in the nutrient compartment and grew over the barrier that divided the petri dishes and into the water agar compartment where juveniles were inoculated. The infective juveniles that thrust their stylets repeatedly into the apical cells of oxamyl-treated roots became immobilized. A comparison with previous studies on intact plants indicated that oxamyl was transported into the root tissues and diffused in the exudates.
TL;DR: A range of fungi grew in a liquid medium lacking added carbon, apparently by scavenging carbon from the medium and laboratory atmosphere and the relevance of oligocarbotrophy and possible chemolithoheterotrophic growth by fungi on thiosulphate to their ability to grow in carbon deficient soils is discussed.
Abstract: A range of fungi grew in a liquid medium lacking added carbon, apparently by scavenging carbon from the medium and laboratory atmosphere. Trichoderma harzianum also grew on a carbon-free medium which was solidified by adding a pluronic polyol. This fungus formed mycelial ‘gossamers’ in a low-carbon medium (50 μg C ml−1), i.e. fine sheets of hyphae showing numerous anastomoses. It also oxidized elemental sulphur in a synthetic soil amended with low concentrations of glucose (10–100 μg C g−1). Thiosulphate stimulated the biomass yield of the fungus in carbon-free liquid media and increased colony radial growth over the first 24 h when grown on an agar medium containing small amounts of carbon. The relevance of oligocarbotrophy and possible chemolithoheterotrophic growth by fungi on thiosulphate to their ability to grow in carbon deficient soils is discussed.
TL;DR: Nine strains of Alteromonas sp.
Abstract: Attempts were made for the isolation of organisms that caused red staining of culture bed (cremona strings) of sporophytes of makonbu and falling of sporophytes from the red-spotted culture bed. Nine strains of Alteromonas sp. were isolated from red-spotted culture beds in the three different nurseries, and were shown to produce prodigiosin-like pigment on double layer agar plates as well as cremona strings covered by soft agar layer, containing viable cells of Escherichia coli. The isolates failed to utilize cell-components of makonbu, such as mannitol, alginate, laminarin and cellulose, but were able to lyse the viable cells of other gram-negative bacteria. According to these properties, it appeared that the isolates grow at the expense of other viable gram-negative bacteria on the cultured bed by lysing them, and produce prodigiosin-like pigment resulting in the staining of cultured bed.