Bacteria electrophoretic separation

Figure 23-20 Capillary electrophoretic separation of whole bacteria found in wounds and bedsores. [E. KTodziiiska and B. Buszewski, Anal. Chem. 2009, 81, 8.)...

Differentiation between the species is shown above, in Table 1.3. Electrophoretic separation of cellular proteins for the identification and differentiation of propionic acid bacteria was suggested by Baer (1987). Every strain was characterized by a specific spectrum of proteins that was compared with the spectrum of standard strains . This method is more rapid and accurate than the classical microbiological analysis of propionibacteria, although it could not differentiate between the strains of P. freudenreichii subsp. freudenreichii and P. freudenreichii subsp. shermanii. Modem methods of molecular biology are being used at present for the identification of propionibacteria (see below). 

Animals were inoculated with Enterobacter cloacae and hemolymph was collected as described (11,12). Hemolymph proteins were separated by isoelectric focusing (IEF) on LKB PAG plates at pH 3.5-9.5 according to the manufacturers instructions. To detect antibacterial activity after IEF, the electrophoretic plates were overlaid with phosphate buffered LB agar seeded with E coli strain D31. The antibacterial factors diffused from the IEF plate into the bacteria-containing overlay thus blocking bacterial growth and revealing bands of activity (13). 

Perhaps the ultimate in protein separations is obtained when a two-dimensional electrophoretic approach is used. O Farrell first demonstrated the truly spectacular resolution that may be achieved when proteins are first separated by isoelectric focusing, then transferred to the top of a gradient gel slab and separated by SDS gradient gel electrophoresis(8). Figure 4 shows the results of such a two dimensional separation of the proteins from the bacteria E. coli(9). The "spot capacity" (maximum number of protein spots which could possibly be resolved) in such systems is presently about... 

The most important issue in food quality analysis is food safety. Therefore, the development of rapid methods for the identification and quantification of bacterial contamination in foods is of utmost importance. Thus, a CE method with UV detection was proposed for the identification and quantification of bacterial contamination in food samples. The proposed method allowed for the effective separation of eight different types of bacteria in only 25 min. Electrophoretic resolution was improved by using cations in phosphate buffer (pH 7.0) that interacted with the bacterial surfaces changing its electrical properties and electrophoretic mobility. The validity of the method was established by comparison with the standard plate counting method, where bacterial cells were separated as... 

The analysis starts with screening. Antibiotics can be detected with the help of the bacteria whose growth they inhibit. Their differentiation can be further improved by means of an electrophoretic preliminary separation. 

Capillary electrophoresis (Section 6.3.1.2) of live and dead bacteria show identical retention times their electrophoretic mobilities (ji ) are indistinguishable (Armstrong and He, 2001). However, the electrical conductivity of the cell membrane of a live bacteria is around 10 pS/mm, whereas that of the cell s interior is much higher, around 10 pS/mm due to many ions. When a bacterium dies, the conductivity of the cell membrane (which becomes permeable) becomes much higher (around IpS/mm). If dead bacteria and live bacteria are suspended in deionized water having a conductivity of 2.2 pS/mm, and if dielectrophoresis is employed, describe what kind of dielectrophoretic separation can be achieved. What would be the observed separation behavior of a plastic particle of radius 0.5 pm if its conductivity is 18.5 pS/mm ... 

Extensive results have been obtained on the electrophoretic mobility of larger rigid probes, notably polystyrene spheres, in polymer solutions(35-37). Limited measurements find that electrophoresis with a polymer solution as a support medium gives excellent separations of intact bacteria(38). The following are representative results, ordered approximately by increasing matrix molecular weight. 

---