Regulation of microbial activity

Alkaloids such as berberine are known to be anti-microbial. They inhibit estarases as well as DNA and RNA polymerases. Moreover, berberine inhibits cellular respiration and acts in DNA intercalation. As a strong anti-microbial agent, berberine may be used in the treatment of AIDS, as it inhibits HIV-I reverse transcriptase. Berberine also has uses in the treatment of infections, specifically eye infections and hepatitis. 

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The relative importance of the MBL and intra-matrix resistance for conversion rates has been described for flat geometry with first- and zero-order kinetics (De Beer 1998). Qualitatively expressed, the greater is the microbial activity of the matrix, the smaller is the penetration depth of the limiting substrate. Consequently, the relative contribution of the mass-transfer resistance inside the matrix decreases. Therefore, the higher the microbial activity, the more important the MBL is for the regulation of microbial activity. The penetration depth of O2, often the limiting substrate, is typically 100 pm in... 

Indicators of microbial activity in soil represent measurements at the ecosystem level (e.g., processes regulating decomposition of organic residues and nutrient cycling, especially nitrogen, sulfur and phosphorus). Measurements at the community level include bacterial DNA and protein synthesis. Frequency of bacteriophages is a measurement at the population level. 

A notorious underestimation of the dynamic properties of microbial and cellular populations results from matching the duration of the respective batch cultivations to the relevant time constant of the biosystem under investigation. However, metabolic regulation of enzyme activities and fluxes often takes place on a time scale of seconds rather than days although the latter may also be true. It is therefore in the scope of promoting biotechnological research to adopt and develop appropriate experimental concepts, methodologies and equipment [397]. 

Microbial secondary metabolites can exert regulation of cellular activities in higher organisms [ 185]. It has been hypothesized that cell-to-cell communication first evolved in unicellular organisms, long before the appearance of specialized... 

Mechanisms involved in the regulation of microbial metabolism can be divided into two general classes—those that alter enzyme concentration and those that alter enzyme activity. Each class is comprised of several specific mechanisms which have been extensively studied and well documented. However, the extent to which identical mechanisms contribute to the coordination of metabolism in higher plants has not yet been resolved. Various aspects of this problem have been discussed in recent reviews which should be consulted for detailed information (Trewavas, 1976 Davies, 1979 Miflin, 1977 Ricard t al., 1977 Stewart and Rhodes, 1977 Wallace, 1976). 

Interleukin-1 OC and (3. IL-1 has radioprotective activity toward BM and other tissues (151,164). IL-1 is produced in response to endotoxin, other cytokines, and microbial and viral agents, primarily by monocytes and macrophages. Other nucleated cells can also produce it. IL-1 appears to play an important role in the regulation of normal hemopoiesis directly by stimulating the most primitive stem cells and indirectly by stimulating other hemopoietic factors, including G-CSF, GM-CSF, M-CSF, and IL-6. 

Recent studies have further examined the iron stress response of pseudomonads using an iron-regulated, ice-nucleation gene reporter (inaZ) for induction of the iron stress response (17,18,84). This particular reporter system was developed by Loper and Lindow (85) for study of microbial iron stress on plant surfaces but was later employed in soil assays. In initial. studies, cells of Pseudomonas fluorescens and P. syringae that contained the pvd-inaZ fusion were shown to express iron-responsive ice-nucleation activity in the bean rhizosphere and phyllosphere. Addition of iron to leaves or soil reduced the apparent transcription of the pvd-inaZ reporter gene, as shown by a reduction in the number of ice nuclei produced. 

Bacteria represent a promising source for the production of industrial enzymes. Bacterial cellulases are an especialfy interesting case in point. Many thermophilic bacterial species produce cellulases that are stable and active at high temperature, resistant to proteolytic attack, and stable to mechanical and chemical denaturation. However, cellulase productivities in bacteria are notoriously low compared to other microbial sources. In this paper bacterial enzyme production systems will be discussed with a focus on comparisons of the productivities of known bacterial cellulase producers. In an attempt to draw conclusions concerning the regulation of cellulase synthesis in bacterial systems, a tentative model for regulation in Acidothennus cellulofyticus has been developed. 

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