Biology ETDs

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The possible production of a coagulase-destroying factor (CDF) by 36 strains of Staphylococcus aureus was investigated. Some related characteristics of coagulases produced by these strains were also studied.

Coagulase used for these experiments was prepared by removing cells from the broth of 5-hour cultures. Preparations assayed for CDF activity were made from cell-free 72-hour culture broth. Inactivation was assayed by observ­ing changes in clotting times of 5-hour broth that was diluted with an equal volume of 72-hour broth. Clotting times were determined at intervals during a 72-hour incubation period. These tests failed to show CDF activity from any of the strains studied.

The pH of 5-hour broths ranged from 6.4 to 6.8 while

that of 72-hour broths ranged between 9.0 and 9.5. The only exception to this result was Strain 26; its broth always had a pH of 6.4. Dilution of the 5-hour broth from Strain 110 with a buffer having a pH similar to that of most 72-hour broths increased clotting time, but no correlation between this increase and pH could be made from the data of this study.

Two-fold dilutions increased clotting times by as much as three times that of the undiluted 5-hour broth. During their 72-hour incubation period some broths showed a stabilization of clotting times. It was assumed from previous investigations (Tager, 1948) that cysteine might be associated with this phenomenon. Thin layer chromatography of mercaptoethanol treated material containing coagulase showed that such an association in vitro is likely. Addition of excess cysteine to cultures slowed the degradation of only one type of unstable coagulase. Coagulase of moderate stability and a stable form were not affected by the cysteine treatment. These results suggest that cysteine could have a role in the stabilization but such a relationship is unclear.



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Department Name

UNM Biology Department

First Committee Member (Chair)

James S. Booth

Second Committee Member

John W. Beakley

Third Committee Member

Gordon Verle Johnson

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