Microbiology incubator

In the commonest form of microbiological assay used today, samples to be assayed are applied in some form of reservoir (porcelain cup, paper dise or well) to a thin layer of agar seeded with indicator organism. The drug diffuses into the medium and after incubation a zone of growth inhibition forms, in this case as a circle around the reservoir. All other factors being constant, the diameter of the zone of inhibition is, within limits, related to the concentration of antibiotic in the reservoir. 

Althongh the prodnct from the transformation of toluene by mntants of Pseudomonas putida lacking dehydrogenase activity is the cis-2R,3S dihydrodiol, the cis-2S,3R dihydrodiol has been synthesized from 4-iodotoluene by a combination of microbiological and chemical reactions. P. putida strain UV4 was used to prepare both enantiomers of the di-dihydrodiol, and iodine was chemically removed nsing H2 -Pd/C. Incubation of the mixtnre of enantiomers with P. putida NCIMB 8859 selectively degraded the 2R,3S componnd to prodnce toluene cis-2S,3R dihydrodiol (Allen et al. 1995). 

Microbiological oxidation has proven of enormous value in steroid chemistry, often affording selective means of functionalizing remote and chemically inactivated positions. It will bear mentioning that the 11-oxygen for all commercially available corticoids is in fact introduced by such a reaction carried out on plant scale. Preparation of the 1-dehydro analogue of 207 involves biooxidation to introduce the 16-hydroxyl. Incubation of 6a-fluoroprednisolone... 

Potentially mineralizable C and N About 1-5% of organic C and total N Quantities of organic C and N released by indigenous soil microflora during a laboratory incubation. Values are the result of an integration of physical, chemical and microbiological properties of the soil. Indicator of the N fertility of soils and their ability to supply N to crops. 

Paraquat is not degraded significantly in soil during incubation periods up to 16 months at 25°C by chemical or microbiological vectors (Smith and Mayfield 1978). For example, paraquat dichloride applied once annually at 4.48 kg/ha, or 4 times annually at 1.12 kg/ha, remained essentially undegraded in the soil for 6 years (Fryer et al. 1975 Moyer and Lindwall 1985). Massive applications... 

There is a need to measure the activities of enzymes and to correlate these measured activities with microbial diversity in soil. It is conceptually wrong to assume a simple relationship between a single enzyme activity and microbiological activity in soil (Nannipieri et al. 2003). Most of the assays used to determine microbiological activities in soil present the same problem measuring potential rather than real activities (Nannipieri et al. 1990). Indeed, assays are generally made at optimal pH and temperature and at saturating concentration of substrate. Furthermore, synthetic rather than natural substrates are often used, and soil is incubated as a slurry (Nannipieri et al. 1990). 

In a further study the oxidation of the methyl carbon of methanearsonate was associated with the oxidation of soil organic matter in a number of soils. Additions of organic matter to a Norfolk loamy sand greatly increased the decomposition of methanearsonate. In three of the soils, there was no evidence of microbiological adaptation to methanearsonate. In Norfolk loamy sand, however, increasing decomposition of methanearsonate relative to soil organic matter occurred with time of incubation. 

Fig. 16.33 Simultaneous (a) toluene conversion and (b) AQDS reduction by Amsterdam petroleum harbor sediment in anaerobic culture bottles containing bicarbonate-buffered basal medium, supplemented with 25 mM AQDS. The unsupplemented control was prepared in the same manner but without AQDS. The endogenous control (without toluene addition) contained the same amount of hexadecane (0.2% [vol/vol]) as that used for toluene addition. AQDS reduction was quantified spec-trophotometiicaUy as the increase in absorbance at 450 nm. Data are means and standard deviations for tiiphcate incubations in each treatment. Arrows indicate the addition of fresh medium containing AQDS and toluene in depleted bioassay mixtures. (Cervantes et al. 2001) Reprinted with permission. Copyright American Society for Microbiology...

The containers should be inspected for any breach of integrity which may have gone undiscovered during release inspection prior to incubation, or could have occurred during post-inspection handling (e.g., transport to incubator, microbiological inspections). 

Visual inspection is performed and good vials are sent to the Microbiological Section for incubation... 

Incubation conditions shall be suitable for recovery of bioburden and environmental isolates at 20 to 35°C. Microbiology department shall provide a rationale for the selection of their specihc incubation conditions according to the trend analysis of area environmental control and presterilization bioburden isolates. The temperature chosen shall be based upon its ability to recover microorganisms normally found environmentally or in the product bioburden. This same panel of microorganisms shall be used in growth testing the media-hlled containers. 

Excluding cosmetic defects, all units that would be procedurally discarded during production shall not be incubated. The reason for discarding shall be documented. It is important that the procedures for excluding units be sufficiently specihc to ensure consistency between process simulation runs and normal operations. Incubation of nonintegral units would introduce a risk for microbial contamination (e.g., during transport to the microbiology lab or... 

Investigations into performance characteristics have shown that various factors affect the efficiency of the microbiological assays tlieir relative influence depends upon the kind of antibacterials assayed and, especially, tlie test organism (7). Agar composition and pH, type of test strain, incubation temperature, depth of the agar, and the manner of incubation are all parameters of critical importance (7-9). 

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