Microbial growth measurement

After 24 weeks NR in the high N (lOOmg/1), P (150mg/l) system had lost 61.5% of its mass whereas in the low N (lOmg/1), P (15mg/l) system, only 23.6% mass was lost. Control (unfertilised) soil produced least mass loss (17.3%). Microbial growth measured on the mbber pieces were in decreasing... 

Maximal levels for -coumaric and ferulic acids of 30.0 and 6.5 pmol/1 0 g of soil ha e been reported (158) and concentrations of 4 x 10 M and 3 x 10 M, respectively, for these two acids in other soils (161)Other gtudies indicate a similar concentration range of 2.3 x 10 to 10 M for -hydroxybenzoic, vanillic and j>-coumaric acids (169). These levels may be too low to have direct measurable allelopathic effects on plants in greenhouse or growth chamber studies (non-rhizosphere soils, low microbial population). However, in field rhizosphere soils (high microbial population) these levels could be sufficient to influence microbial growth... 

HSA is used therapeutically as an aqueous solution it is available in concentrated form (15-25 per cent protein) or as an isotonic solution (4-5 per cent protein). In both cases, in excess of 95 per cent of the protein present is albumin. It can be prepared by fractionation from normal plasma or serum, or purified from placentas. The source material must first be screened for the presence of indicator pathogens. After purification, a suitable stabilizer (often sodium caprylate) is added, but no preservative. The solution is then sterilized by filtration and aseptically filled into final sterile containers. The relative heat stability of HSA allows a measure of subsequent heat treatment, which further reduces the risk of accidental transmission of viable pathogens (particularly viruses). This treatment normally entails heating the product to 60 °C for 10 h. It is then normally incubated at 30-32 °C for a further 14 days and subsequently examined for any signs of microbial growth. 

Measurement of exoenzymatic activities is potentially useful in detecting the effects of toxicants on heterotrophic biofilm communities. Sensitivity and direct relationship with organic matter use and, therefore, microbial growth make extracellular enzyme activities a relevant tool to assess the toxicity of specific compounds. Use of novel approaches that combine enzymatic and microscopic tools (e.g. ELF-phosphatase) may be extremely useful to detect anomalies at the sub-cellular scale. 

Because standardization is an essential component of soil pH measurement, care must be taken to have good buffers. If the buffers show any indication of contamination, such as material floating in them, soil, or microbial growth, they... 

Odour will return in treated slurry as a result of post treatment fermentation. The concentration of readily fermentable substrates, measured as BOD5, provide an indicator of this problem. In continuous culture without oxygen limitation the BOD5 can be described by a model derived from the Monod (13) model of microbial growth (14). The supernatant BOD5 (g/1) from treatment at 15 to 45°C, was described by equation 3 and the whole BOD5 by equations 4 and 5(15). 

C. L. Cooney, D. I. C. Wang, and R. I. Mateles, Measurement of heat evolution and correlation with oxygen consumption during microbial growth, Biotechnol. Bioeng. 1969, 11, 269-281. 

Williams, P. J. L. 1990. The importance of losses during microbial growth Commentary on the physiology, measurement, and ecology of the release of dissolved organic material. Marine Microbial Food Webs 4 175-206. 

There are many ways to estimate microbial growth. The simplest is visual inspection of colonies growing on agar plates, though this method is difficult to adapt for HTS. There is a well-known correlation between cell density and optical density, which can be exploited in a 96-well microtiter plate format (e.g., [43]). Measurement of the incorporation of radioactive nutrients is an excellent quantitative method, but has fallen from favor due to concerns about spills and contamination. Finally, both spectrophotometric and fluorimetric assays are conveniently adapted to HTS formats, and Alamar blue is only one example of the tools available for this purpose. As mentioned, we have even found it convenient to use simple visual inspection of Alamar blue plates to identify wells of interest. However, quantification obtainable with a microplate reader is attractive in many settings. 

Newly synthesized compounds 22, 23, 25c-e, 26d and 29e were screened in vitro for their antimicrobial activities against Gram positive bacteria Staphylococcus aureus (NCTC-7447), Bacillus cereus (ATCC-14579) and Gram negative bacteria Serratia marcesens (IMRU-70) and Proteus merabitis (NTCC-289) using the paper disk diffusion method for the antibiotic sensitivity technique [60]. The tested compounds were dissolved in N,N-dimclhylformamidc (DMF) to obtain a 1 mg/mL solution. The inhibition zones of microbial growth produced by different compounds were measured in millimeters at the end of an incubation period of 48 h at 28 °C. DMF alone showed no inhibition zone. 

Doubling times Microbial growth rates are measured in terms of doubling times. Dou-... 

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