Enrichment culture approach

The source of microorganisms and CP-degradation kinetics are key factors in on-site systems. Development of specific microbial cultures for bioremediation of CPs may involve pure and enrichment culture approaches. The approach of isolation and mass cultivation, followed by inoculation of the treatment system, has been applied to systems using, for example, Flavobacteria (O Reilly Crawford, 1989) and Rhodococci (Valo et al., 1989). The Flavobacterium-based processes sometimes involve addition of supplemental carbon and energy sources during CP treatment. 

Conventional approaches to microbiological examination of specimens require that they be cultured to assess the total numbers of specific groups of microorganisms or to determine the presence or absence of particular named species. The majority of samples taken for examination contain mixtures of different species, so simple plating onto an agar surface may fail to detect an organism that is present at < 2% of the total viable population. Various enrichment culture techniques may therefore be deployed to detect trace numbers of particular pathogens, prior to confirmatory identification. 

Fig. 3.4 Natural evolutionary process support the growth of square colonies over the period of evolution. Performing enrichment screening to obtain circled colonies might temporarily endows the culture with larger amount of those colonies however, because of squares evolutionary advantage they will continually outcompete the circled colonies. In contrast to the enrichment screening approach, synthetic intervention or selection can be useful in isolating clones with optimized for both cellular and engineering objectives...

In parallel with molecular nonculture methods, the well-established methods of enrichment culture are more frequently being applied under anaerobic and other nonstandard conditions in an effort to obtain novel microbial types. This approach also suggests that biodegradative capabilities are more widespread in the microbial world than has been appreciated by some. For example, halophiles have been identified which metabolize nitroarenes, and members of the Heliobacterium group are known that catabolize polychlorinated biphenyls (PCBs) and chlorophenols (O Table 15.2). These and other recent observations are expanding the taxonomic range of bacteria that catabolize environmental pollutants. Further experiments are likely to expand this further. 

The importance for proteomic studies of being performed on standardized samples cannot be emphasized enough. Several approaches have been developed to address the problem of tissue heterogeneity. Beads-based sample enrichment (BBSE) and laser capture microdissection (LCM) procedures are emerging as the methods of choice. The aim of these procedures is to eliminate, as much as possible, all confounding and contaminating factors in order to obtain a sample quality that can be compared with cell lines without the disadvantages of in vitro cultures. 

Until 1990, when Giovannoni and Ward applied 16S rRNA sequence analysis by extracting community DNA, microbiologists had to rely on plate counts of bacteria which could be cultured and isolated to obtain an idea of the number of bacteria in the sample.43,44 This new approach allowed the study of the remaining 99% of bacteria which could not be isolated by nutrient media and liquid enrichment. 

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