8] Enrichment culture and isolation techniques particularly for anaerobic bacteria

Abstract

This chapter discusses enrichment culture and isolation techniques particularly for anaerobic bacteria. Successful application of enrichment culture techniques for anaerobic bacteria is dependent upon an orderly use of a sequence of operations. These include a careful choice of material used for the initial inoculum, a suitable medium prepared and handled so that anaerobiosis is achieved, favorable incubation conditions, a well-considered transfer schedule, and a final procedure making possible the isolation of a pure culture. Suitable sources of inocula for the isolation of anaerobic bacteria usually are naturally occurring anaerobic materials. Swamps, black mud, and water containing large amounts of organic substances have been frequently used. Suitable culture media contain the specific substrate of interest, mineral salts, and supplements to provide certain growth factors and anaerobiosis. Usually two or three transfers are necessary to enable the desired organism to dominate the mixed enrichment culture. The timing of the transfers is important and for some bacteria may be the critical step in the entire isolation procedure. Several general methods are available for isolation of pure culture colonies of anaerobic bacteria. Liquefiable solid media with an additive to poise the Eh value and incubation in the absence of atmospheric oxygen achieved by any of several standard procedures may be employed in either the streak or pour plate methods.