Degradation point bacterial

Potential Points of Initial Attack for Nonionic Surfactants. Bacterial inocula have been shown to produce enzymes which can initiate degradation at any of three different locations ( of the nonionic surfactant. As depicted in Figure 5, these are ... 

To reduce the loss of contaminants from the collected samples due to volatilization and bacterial degradation, the majority of environmental samples must be preserved by storage within a temperature range of 2-6 °Celsius (C). Samples collected for VOC analysis are particularly susceptible to such losses even at slightly elevated temperatures. Preserved samples represent the sampling point conditions at the time of sampling, and that is why proper preservation upon sample collection is necessary to assure the collected sample representativeness. 

Common to nearly all analyses is preservation with refrigeration at 2-6°C, a practice, which minimizes the volatilization of organic compounds with low boiling points and the bacterial degradation of most organic compounds. That is why we must place samples on ice immediately after they have been collected, ship them in insulated coolers with ice, and keep them refrigerated until the time of analysis. Water samples collected for metal analysis and preserved with nitric acid are an exception to this rule as they may be stored at room temperature. The addition of methanol or sodium bisulfate solution to soil collected for VOC analysis is the only chemical preservation techniques ever applied to soil samples. 

Much of the research in the University of Michigan laboratories has been done with the Hi-Sep 70, a vinyl plastic membrane [Graver Water Conditioning Co., New York, N. Y.] which has an effective pore size of 70 A units and is not subject to bacterial degradation. Unfortunately this material is somewhat brittle and tends to crack at points where fiexure takes place in a dialysis frame. It also tends to change pore size when sterilized in an autoclave. 

The bacterial activities again point to the diversity of the OPA anhydrases. The OT strain JD100 is able to degrade soman, sarin, and dimebu, but not DFP. The bacterial activities reported to date all seem insensitive to ammonium sulfate inhibitions and have molecular weights above that of the hog kidney OPA anhydrase. 

The authors pointed out that the cobalt-dependenq of this enzyme may explain why several axenic bacterial cultures require Co for degradation of TEA and HIBA [21,24,25,60]. Most remarkably, the same gene (nearly 100% identity) was foimd in the finished genome of M. petroleiphilum PMl [22], suggesting a horizontal gene transfer between both cultures. 

Several fatty acids, specifically 15 0, 17 0 and all branched fatty acids, are produced primarily by both aerobic and anaerobic bacteria [55-57] and the sum of those fatty acids has been used to estimate bacterial contributions [58-61]. A comparison of bacterial markers in plankton, sediment trap and sediment samples showed the lowest values, with little variation, in plankton samples (Fig. 3 b), and the greatest bacterial levels in sediments. The sediment traps, containing partially degraded material, had bacterial marker levels intermediate between the other two sample types, and levels of bacterial markers increased with increasing period of deployment. However, there are conflicting theories concerning the usefulness of these markers and, for that reason, bacterial markers should only be employed with caution. For instance, in a recent paper, Harvey and Macko [57] did not find a correlation between total fatty acids attributed to bacteria and bacterial carbon, and they suggest that bacterial fatty acids only be used as qualitative tools to estimate bacterial contributions. Wakeham [62] also points out that fatty acids of common oceanic bacteria may not be compositionally different from planktonic fatty acids so that bacterial... 

---