Pure culture transformations

Pure Culture Transformations on Partially Defined Media... 

In determining pathways, pure cultures are easier to work with than are consortia, since consortia make it difficult to determine which organism is responsible for individual steps in the transformation process. Furthermore, consortia are usually... 

The growth of malo-lactic bacteria in wines is favored by moderate temperatures, low acidity, very low levels of S02, and the presence of small amounts of sugar undergoing fermentation by yeast. It is frequently possible to inoculate a wine with a pure culture of a desirable strain of bacteria and obtain the malo-lactic fermentation under controlled conditions. The pure-culture multiplication of the selected strain of bacteria is difficult, however. It is also difficult to control the time of the malo-lactic fermentation—sometimes it occurs when not wanted, and at other times will not go when very much desired. For the home winemaker it is probably most satisfactory to accept the malo-lactic fermentation if it occurs immediately following the alcoholic fermentation. The wines should then be siphoned away from deposits, stored in completely filled containers at cool temperatures, and have added to them about 50 ppm S02. If the malo-lactic fermentation does not take place spontaneously and the wine is reasonably tart, the above described regime of preservation will likely prevent its occurrence. When the malo-lactic transformation takes place in wines in bottles, the results are nearly always bad. The wine becomes slightly carbonated, and the spoiled sauerkraut flavors are emphasized. 

The chimeric tissue problem has been solved by co-cultivating plant protoplasts with A. tumefaciens (Figure 14), then treating these protoplast suspensions with an antibiotic that selectively kills the A. tumefaciens. The protoplasts are plated onto a nurse layer of tobacco cells which feed the individual protoplasts and aid them in regenerating into pure colonies. The colonies ultimately form callus, and this allows for the production of pure cultures of transformed cells. These cultures can then be regenerated into plants. 

An historical perspective of the iron bacteria has been given and over the years geomicrobiologists have studied a variety of bacteria concerned with iron transformations. The absence of pure culture techniques and modern technical sophistication has prevented the clear elucidation of those organisms attacking iron for use as a major nutrient. It is remarkable that it took from 1888, when the concept of chemoautotrophy was advanced by Winogradsky, until 1950 before the existence of a bacterium which is able to grow at the expense of ferrous iron oxidation was unequally demonstrated (Colmer et al., 1950). 

---