Isolation of Microorganisms from Preservative-Treated Wood

Ponderosa pine stakes, either nontreated or impregnated with various concentrations of pentachlorophenol and fuel oil, or fuel oil only, were exposed to a soil burial test for various lengths of time. The presence of microorganisms was determined by isolation from these stakes on several culture media. Fungi were not found to invade the treated stakes during the exposure times used, while an unidentified bacterium was found both in the nontreated and preservative treated specimens. The bacterium also grew on a medium containing 0.5 percent pentachlorophenol, demonstrating its resistance to the toxicant. The test material consisted of a single board of ponderosa pine sapwood cut into stakes 3/4 by 3/4 inches. Based on 10 randomly selected stakes, the ovendry specific gravity was 0.567 and the stakes contained an average of 30.1 rings per inch. The EMC was 5.94 percent based on ovendry weight. The remaining stakes were numbered from 1 to 200 and divided into four treatment groups. Treatment A consisted of submerging the stakes in 5 percent actual pentachlorophenol containing number 1 fuel oil. Treatment B consisted of 10 percent pentachlorophenol in number 1 fuel oil. Treatment C received fuel oil only, and Treatment D received no solution. The stakes were placed in the ground 20 miles west of Ann Arbor, Mich. The unidentified bacterium has characteristics that make it similar to the genus Alcaligines. This bacterium may or may not be affecting the pentachlorophenol or it may be modifying the preservative with or without a concomitant modification in toxicity.

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