Microbial substrate adaptation

First, there is a lag phase during which the microbial population adapts to the available test C-substrate. Then, there is the biodegradation phase during which the adapted microbial population begins to utilise the carbon substrate for its cellular life processes, as measured by the conversion of the carbon in the test material to CO2. Finally, the output reaches a plateau when all of the substrate is completely utilised. 

Aelion CM, DC Dobbins, FK Pfaender (1989) Adaptation of aquifer microbial communities to the biodegradation of xenobiotic compounds influence of substrate concentration and preexposure. Environ Toxicol Chem 8 75-86. 

Without appropriate cleanup measures, BTEX often persist in subsurface environments, endangering groundwater resources and public health. Bioremediation, in conjunction with free product recovery, is one of the most cost-effective approaches to clean up BTEX-contaminated sites [326]. However, while all BTEX compounds are biodegradable, there are several factors that can limit the success of BTEX bioremediation, such as pollutant concentration, active biomass concentration, temperature, pH, presence of other substrates or toxicants, availability of nutrients and electron acceptors, mass transfer limitations, and microbial adaptation. These factors have been recognized in various attempts to optimize clean-up operations. Yet, limited attention has been given to the exploitation of favorable substrate interactions to enhance in situ BTEX biodegradation. 

Mineralization of organic residues in soil is mainly carried out by an extremely diverse heterotrophic community referred to as the soil microbial biomass. The soil environment is a rather peculiar natural environment for the growth of microorganisms, in that they have had to adapt to quite extreme growth-limiting factors (a) discontinuous availability of substrates and water and (b) high variability of soil chemical properties (pH, temperature, oxygen supply) that can vary in the soil environment on both the micro and macro scales (Jenkinson and Ladd, 1981). 

Adaptability of Shewanella oneidensis MRl and Escherichia coli in these experiments indicates that microorganisms can continue to metabolize substrate at pressures far beyond those previously reported [34, 35,41], Although an evolutionary component to the adaptation of microbial communities to temperature and salinity is well known [71], whether there might be any evolutionary component for pressure adaptation is still in question. Shewanella MRl belongs to a genus that contains a number of piezophiles however, E. coli clearly does not. Despite this, there is evidence that exposure of E. coli to pressures up to 800 MPa selects a population of cells less sensitive to pressure inactivation [71]. Furthermore, it is well known that the increase in pressure tolerance is also associated with heat tolerance [71]. 

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