Biology ETDs

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The effect of laminar air-flow on the viability of microorganism was investigated. The related factors of inoculum size and carrier medium were also studied. The test surface used in this study was stainless steel. Microorganisms were placed on the test strips and exposed to laminar air-flow. After the chosen exposure period the test strips were placed in a sterile petri dish and covered with tryptic soy agar. Viable counts were taken as the number of colonies developing after incubation. Viable counts obtained with this direct plating method were briefly compared with viable counts obtained by two other assay methods.

It was found that laminar flow renders Staphylococcus aureus, S. epidermidis, and Corynebacterium oseudodioh­theriticum nonviable more rapidly than if the organisms are simply exposed to ambient conditions. Spores of Bacillus subtilis var. niger and B. subtilis 5230 seem adversely affected by laminar flow, but are more resistant than the vegetative cells tested.

Colloidal materials such as tryptic soy broth will increase an organism's resistance to the detrimental effects of laminar flow and dessication in general. Large numbers of organisms survive better in a laminar flow situation than do smaller numbers, this is also true for ordinary dessication.

The direct plating method and the use of insonation in conjunction with direct plating gave comparable viable counts. The levels of ultrasonic energy used in this study did not prove adequate for removing microorganisms from the test strips. Mechanical shaking was also used to remove organisms from the test surface for viable assay, but was found to be unsatisfactory when small numbers of organisms were involved.



Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

John W. Beakly

Second Committee Member

James S. Boots

Third Committee Member

Clarence Clayton Hoff

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Biology Commons