A taxonomic study on myxobacteria isolated from fish Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/hd76s381p

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  • Myxobacteria isolated from fish
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  • While the genus Cytophaga has been defined and classified on a morphological basis, knowledge of fresh water members of this group of myxobacteria is scanty. In the present study cultural and morphological characteristics were investigated in an attempt to classify a group of fresh water cytophaga. Microscopic examination revealed all test isolates to exhibit morphological properties of myxobacteria. Vegetative cells were gram negative, long, slender, flexible rods showing gliding or creeping motility and low refractibility. On aging, cells showed various involution or degenerate stages, especially in rich media. As cells aged they lost their typical gliding motility but showed various other types of movement. Typical colonies at 24-48 hours were yellow-orange in color and showed morphological differences between strains. The nutritional content of media was found to be a factor influencing colony morphology. More compact colonies were found on rich media and as the nutrients were diluted, colonies tended to spread and have less coloration. Variation in colony morphology were also noted on different types of media as well as different concentrations of the same medium. Only one strain was found to form fruiting bodies or columnar masses of cells; this organism however, did not form microcysts. Test isolates could be divided into two groups on the basis of growth temperature. The psychrophilic group grew best at 18°C and failed to grow at room temperature; the mesophilic group grew best at room temperature. Members of the psychrophilic group were found to be more sensitive to increased salt concentrations or change in pH and were not able to grow anaerobically. Ten of the mesophiles were capable of growing anaerobically. A number of macromolecules were degraded by the test isolates. Starch, gelatin, chitin, aesculin and tributyrin were hydrolyzed by various test organisms and most of the isolates lysed a variety of dead bacterial cells. Members of the psychrophilic group showed more limited ability to hydrolyze macromolecules than did those of the mesophilic group. Seven of the test organisms oxidized glucose, and seven fermented this sugar; however, none of these oxidizers or fermenters were psychrophiles. Some of the organisms produced black pigment from tyrosine, reduced nitrate, and possessed the enzymes catalase and cytochrome oxidase. All were negative for the production of acids or acetyl methyl carbinol from glucose, cadaverine from lysine, indol from tryptophan and ammonia from arginine. None of the test isolates could utilize glucose as a sole carbon source with ammonia as the sole nitrogen source. Nine amino acids tested would not support growth as the sole nitrogen and carbon source. Five of these were inhibitory for some organisms when added to peptone and mineral basal medium. The majority of the organisms were capable of growing on non-nutrient agar, even after several transfers. Most of the organisms were found to be sensitive to dihydrostreptomycin, penicillin, tetracycline and erythromycin. Only five organisms were sensitive to neomycin. Another five organisms were sensitive to polymyxin B. Most of the isolates were resistant to novobiocin and bacitracin. The resistance to heat varied among the isolates. In general, the psychrophilic group were more sensitive to high temperatures than the mesophilic group. Since none of the organisms were able to survive a temperature of 70°C for 15 minutes, it is likely that resistant forms are not produced by the isolates. The results of this study indicate that cultural and biochemical data are useful in the classification of myxobacteria. Based on the results of this work and previously published data, a new taxonomic scheme for the cytophagas has been proposed.
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  • File scanned at 300 ppi using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 5.0 was used for pdf compression and textual OCR.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2014-03-17T21:16:11Z (GMT) No. of bitstreams: 1 PorterSookH1968.pdf: 1658369 bytes, checksum: 64d34c50c01847806f01fe8c424464b0 (MD5)
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