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United States Department of Agriculture

Agricultural Research Service

Title: Growth of Clostridium Species in Anaerobic Media Reduced by Photocatalytic Interaction of Cysteine and Resazurin

item Fukushima, R - U. OF SAN PAOLO
item Weimer, Paul
item Kunz, D - U. OF NORTH TEXAS

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2002
Publication Date: May 22, 2002
Citation: Fukushima, R.S., Weimer, P.J., Kunz, D.A. 2002. Growth of clostridium species in anaerobic media reduced by photocatalytic interaction of cysteine and resazurin [abstract]. American Society for Microbiology Annual Meeting. p. 260-261.

Technical Abstract: Culture media for obligate anaerobes typically contains a chemical reducing agent and a redox indicator (usually resazurin, RNO). Cysteine (Cys) is often used as a reducing agent because of its low toxicity, but Cys reduces the medium only slowly, an inconvenience if the medium is needed immediately, or when preparing medium in large amounts. To simplify medium preparation, we explored the photocatalytic properties of RNO. In the presence of RNO, reduction of N2-gassed CM5 medium by Cys was greatly accelerated under intense light, and the time required for reduction displayed an inverse log-log relationship with light intensity. Room fluorescent and incandescent light of similar intensity facilitated reduction of the medium at similar rates. O2-electrode experiments revealed that light stimulated the rate of Cys-mediated O2 removal, and that this stimulation was dependent on the presence of RNO. Medium reduced under low or high light intensity were indistinguishable in supporting growth of several anaerobic species, including Clostridium beijerinckii, C. butyricum, C. sporogenes, and Thermoanaerobacter saccharolyticum B6A, when measured in terms of lag time, maximum growth rate, and final optical density. The data suggest that RNO-mediated photocatalysis of medium reduction by Cys can improve the efficiency of preparing anaerobic media by shortening or eliminating several commonly-used procedural steps (e.g.,boiling of medium, scrubbing of gas with heated copper, or vacuum degassing of vessels).

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