Selective/enrichment cultures

Enzymes used for biocataly tic processes may be commercially available, identified by screening culture collections, or available from a toolbox of enzymes previously cloned for other projects, or, if necessary, can be identified by enrichment, selection, and screening of strains from soil samples. 

If the micro-organism has been obtained from a culture collection or from a researcher in another laboratory, a recommended medium to promote good growth will normally be suggested. If, on the other hand, the micro-organism has been obtained by an enrichment selection technique, then the enrichment medium itself will self-evidently support growth. 

Current detection methods involve primarily cell culturing in selective broth. Although a variety of selective media and protocols are available, most of these methods require a series of sequential enrichment and culturing steps. These are lengthy, labor-intensive procedures which require further confirmation analyses. In addition, false-negative results may be obtained when Salmonella is outgrown by other organisms. 

This work lead by Kilbane was carried out in collaboration with Petrobras and gave rise to three patents [371,375,376], which protected not only P. ayucida IGTN9m (ATCC N° PTA-806, but also the thermophilic culture Aneurinibacillus sp. IGTN4T (ATCC N° PTA-4581), and strains, P. stutzeri, Yokenella sp., and P. nitroreducen. The P. stutzeri strain was selectively enriched using carbazole as the sole nitrogen source. The experimental results also indicated that the considered strain selectively cleaved the C—N bonds in carbazole. The same behavior was also observed for Yokenella sp. when cultured according to the principles described before. The specific metabolites produced by the conversion of carbazole have not yet been determined. 

The bacterial strains were submitted to the National Collection of Microorganism Cultures of the Pasteur Institute (CNCM) and included R. erythropolis CNCM 1-2204, -2205, -2207, and -2208, and/or R. rhodnii 1-2206. The activity of the microorganisms includes a selective attack on the carbon-sulfur bonds in the organic molecules without significant alteration of the carbon atom structure. As usual, strains were isolated and subjected to successive enrichment phases, in media containing various sources of carbon and DBT as the only sulfur source, then a purification of the enhanced culture led to the fifteen DBT specific strains. From those strains, a subset of ten strains was selected... 

Based on those results, we concluded that, when cultured on the EGF-His-immobilized surface prepared from a mixed SAM of 10% COOH-thiol, highly enriched NSC populations could be produced in large quantities. Over a 5-day culture on the substrate, cells were expanded 32 times. These expanded cells consisted of 98% nestin+ cells that retained multipotency for differentiation into neuronal and glial lineages. This suggested that selective expansion could be repeated for large-scale production of highly enriched NSC cells. 

Pure cultures of Pseudomonas sp. isolated by selective enrichment from activated sludge were reported to degrade 1,4-dichlorobenzene (Spain and Nishino 1987). These authors reported that the 1,4-dichloro-... 

Jacobson, A. P., Thunberg, R. L., Johnson, M. L., Hammack, T. S., and Andrews, W. H. (2004). Alternative anaerobic enrichments to the bacteriological analytical manual culture method for isolation of Shigella sonnei from selected types of fresh produce. J. AOAC Int. 87,1115-1122. 

Plants are improved by appropriate culture, by digging and enriching the soil, by judicious selection of seed animals are improved by careful breeding. By similar processes metals will be encouraged and helped towards perfection. The perfect state of gold will not be reached at a bound it will be gained gradually. Many partial purifications will be needed. As Subtle says in The Alchemist—... 

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