Enteric bacteria gene regulation

In enteric bacteria, expression of the nif genes is under general nitrogen regulation by the ntr system. This system consists of essentially a sensor-activator pair of proteins, encoded by ntrB and ntr(d. When fixed nitrogen is limiting, the sensor, NtrB, phosphorylates (and so activates) the activator,... 

Not much is known about the effect of organic acids on another important pathogen, Salmonella spp., but E. coli and Salmonella are both enteric bacteria and seem to have a similar physiology. It is, however, known that medium chain fatty acids (C6-C12, caproic, caprylic, capric, and lauric) are much more effective against Salmonella than the short-chain fatty acids (formic, acetic, propionic, and butyric). Another important finding was that the short-chain fatty acid butyrate specifically down-regulates the expression of invasion genes in Salmonella spp. at low doses. Medium-chain fatty acids and propionate also decrease the ability of Salmonella spp. to invade epithelial cells. This has been found to be in contrast to acetic acid (Van Immerseel et al., 2006). 

B. subtilis and many other Bacilli have the intrinsic potential to differentiate into distinct physiological states. One such state is natural competence, which allows the bacteria to take up DNA from the surrounding environment and to incorporate it into their chromosome by homologous recombination. This process involves over 50 different genes with many different functions ranging from regulated expression of the DNA uptake machinery to incorporation of the ingested DNA into the chromosome [117-119]. For a B. subtilis cell to enter into a state of competence, several criteria must be met and this means that only approximately 10% of the population will ever develop full competence. Nowadays, the most frequently used protocol for transformation of B. subtilis via competence is the one published by Kunst and Rapoport [120]. 

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