| 1. |
- Blackburn, Nicholas, et al.
(författare)
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Rapid determination of bacterial abundance, biovolume, morphology, and growth by neural network-based image analysis
- 1998
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 64:9, s. 3246-3255
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Tidskriftsartikel (refereegranskat)abstract
- Annual bacterial plankton dynamics at several depths and locations in the Baltic Sea were studied by image analysis. Individual bacteria were classified by using an artificial neural network which also effectively identified nonbacterial objects, Cell counts and frequencies of dividing cells were determined, and the data obtained agreed well with visual observations and previously published values. Cell volumes were measured accurately by comparison with bead standards. The survey included 690 images from a total of 138 samples. Each image contained approximately 200 bacteria. The images were analyzed automatically at a rate of 100 images per h, Bacterial abundance exhibited coherent patterns with time and depth, and there were distinct subsurface peaks in the summer months. Four distinct morphological classes were resolved by the image analyzer, and the dynamics of each could be visualized. The bacterial growth rates estimated from frequencies of dividing cells were different from the bacterial growth rates estimated by the thymidine incorporation method. With minor modifications, the image analysis technique described here can be used to analyze other planktonic classes.
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| 2. |
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| 3. |
- Dopson, Mark, et al.
(författare)
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Potential role of thiobacillus caldus in arsenopyrite bioleaching
- 1999
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 65:1, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the potential role of the three strains of Thiobacillus caldus (KU, BC13, and C-SH12) in arsenopyrite leaching in combination with a moderately thermophilic iron oxidizer, Sulfobacillus thermosulfidooxidans. Pure cultures of T. caldus and S. thermosulfidooxidans were used as well as defined mixed cultures. By measuring released iron, tetrathionate, and sulfur concentrations, we found that the presence of T. caldus KU and BC13 in the defined mixed culture lowered the concentration of sulfur, and levels of tetrathionate were comparable to or lower than those in the presence of S. thermosulfidooxidans. This suggests that T. caldus grows on the sulfur compounds that build up during leaching, increasing the arsenopyrite-leaching efficiency. This result was similar to leaching arsenopyrite with a pure culture of S. thermosulfidooxidans in the presence of yeast extract. Therefore, three possible roles of T. caldus in the leaching environment can be hypothesized: to remove the buildup of solid sulfur that can cause an inhibitory layer on the surface of the mineral, to aid heterotrophic and mixotrophic growth by the release of organic chemicals, and to solubilize solid sulfur by the production of surface-active agents. The results showed that T. caldus KU was the most efficient at leaching arsenopyrite under the conditions tested, followed by BC13, and finally C-SH12.
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| 4. |
- Ericsson, Henrik, et al.
(författare)
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Division of Listeria monocytogenes serovar 4b strains into two groups by PCR and restriction enzyme analysis
- 1995
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 61:11, s. 3872-3874
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Tidskriftsartikel (refereegranskat)abstract
- Altogether, 133 strains of Listeria monocytogenes serovar 4b were investigated, A segment of 2,916 bp containing parts of the two genes inlA and inlB in L. monocytogenes was amplified by the PCR technique. The PCR product obtained was cleaved with the restriction enzyme AluI, and the fragments generated were separated by gel electrophoresis, leading to two distinct groups: PCR-restriction enzyme analysis groups I and II, containing 37 and 96 strains, respectively, The PCR-restriction enzyme analysis method described in this paper could be a useful tool for the subtyping of L. monocytogenes serovar 4b strains.
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| 5. |
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| 7. |
- Kuhn, I, et al.
(författare)
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Diversity, persistence, and virulence of Aeromonas strains isolated from drinking water distribution systems in Sweden
- 1997
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Ingår i: Applied and environmental microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 63:7, s. 2708-2715
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Tidskriftsartikel (refereegranskat)abstract
- The Aeromonas populations in 13 Swedish drinking water distribution systems, representing different treatments, were investigated. From each system, water samples were collected four times during the period from May to September 1994 from raw water and water after treatment and at two to five sites within the distribution system. In total, 220 water samples were collected. From samples containing presumptive Aeromonas, up to 32 colonies were analyzed by the PhenePlate Aeromonas (PhP-AE) system, which is a highly discriminating biochemical fingerprinting method. Selected isolates from different phenotypes (PhP types) were further identified by the API 20 NE system and by gas-liquid chromatography analysis of fatty acid methyl esters (FAMEs). Selected isolates were also assayed for their potential to produce hemolysin and cytotoxin and for their ability to adhere to human intestinal cells. In total, 117 water samples (53%) contained presumptive Aeromonas which numbered up to 10(6) CFU/100 ml in raw water and up to 750 CFU/100 ml in tap water. Among the 2,117 isolates that were subjected to typing by the PhP-AE system, more than 300 distinct PhP types were found, of which the majority occurred only sporadically. Raw (surface) water samples usually contained many different PhP types, showing high diversity indices (Di) (median Di = 0.95). The Aeromonas populations in samples collected from within the distribution systems were less diverse (median Di = 0.58) and were often dominated by one major PhP type that was found on several sampling occasions. Seventeen such major PhP types could be found and were represented in 1,037 isolates (49%). Identification by API 20 NE and FAME analysis revealed that most of the major PhP types were Aeromonas hydrophila or belonged to unidentified Aeromonas species. Hemolysin and cytotoxin production was observed in most major PhP types (representing 87 and 54% of the assayed isolates, respectively), and adherence was found in 89% of the isolates that produced cytotoxin. Thus, the data presented here show that although raw water may contain very diverse Aeromonas populations, the populations seemed to be remarkably stable within the studied water distribution systems, and that some potentially pathogenic Aeromonas strains could persist for several months in drinking water.
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| 8. |
- Petersson, Stina, et al.
(författare)
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Biocontrol of Mold Growth in High-Moisture Wheat Stored under Airtight Conditions by Pichia anomala, Pichia guilliermondii, and Saccharomyces cerevisiae
- 1995
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 61:3, s. 1027-1032
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Tidskriftsartikel (refereegranskat)abstract
- Pichia anomala inhibits the growth of Penicillium roqueforti and Aspergillus candidus on agar. In this investigation, antagonistic activity on agar against 17 mold species was determined. The abilities of Pichia anomala, Pichia guilliermondii, and Saccharomyces cerevisiae to inhibit the growth of the mold Penicillium roqueforti in nonsterile high-moisture wheat were compared by adding 10(3) Penicillium roqueforti spores and different amounts of yeast cells per gram of wheat. Inoculated grain was packed in glass tubes, incubated at 25 degrees C with a restricted air supply, and the numbers of yeast and mold CFU were determined on selective media after 7 and 14 days. Pichia anomala reduced growth on agar plates for ail of the mold species tested in a dose-dependent manner. Aspergillus fumigatus and Eurotium amstelodami were the most sensitive, while Penicillium italicum and Penicillium digitatum were the most resistant. Pichia anomala had the strongest antagonistic activity in wheat, with 10(5) and 10(6) CFU/g completely inhibiting the growth of Penicillium roqueforti. Inhibition was least pronounced at the optimum temperature (21 degrees C) and water activity (0.95) for the growth of Penicillium roqueforti. Pichia guilliermondii slightly reduced the growth of Penicillium roqueforti in wheat inoculated with 10(5) and 10(6) yeast CFU/g, S. cerevisiae inhibited mold growth only weakly at the highest inoculum level. Pichia anomala grew from 10(3) to 10(7) CFU/g of wheat in 1 week To reach the same level, Pichia guilliermondii had to be inoculated at 10(4) CFU while S. cerevisiae required an inoculum of 10(5) CFU to reach 10(7) CFU/g of wheat.
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| 9. |
- Petersson, S., et al.
(författare)
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Biocontrol of Mold Growth in High-Moisture Wheat Stored under Airtight Conditions by Pichia anomala, Pichia guilliermondii, and Saccharomyces cerevisiae (VOL 61, PG 1029, 1995)
- 1995
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Ingår i: Applied and Environmental Microbiology. - Washington : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 61:4, s. 1677-1677
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Tidskriftsartikel (refereegranskat)abstract
- Volume 61, no. 3, p. 1029, Table 1, boxhead over columns 2 to 4: "(CFU/plate)" should read "(log CFU/plate)." FIG. 1 [This corrects the article on p. 1027 in vol. 61.].
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| 10. |
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