Phosphate solubilizing bacteria and their role in plant growth promotion

Protein phosphorylation and regulation of adaptive responses in bacteria.

Mg2+ as an Extracellular Signal: Environmental Regulation of Salmonella Virulence

PhoP-PhoQ is a two-component system that governs virulence, mediates the adaptation to Mg2+-limiting environments, and regulates numerous cellular activities in several gram-negative species. It consists of the inner membrane sensor PhoQ and the cytoplasmic regulator PhoP. The PhoP-PhoQ system is

The Pleiotropic Two-Component Regulatory System PhoP-PhoQ

The gram-negative bacterial species Salmonella enterica and Escherichia coli are members of the family Enterobacteriaceae that spend a good part of their lives as residents of animal hosts. S. enterica is the etiologic agent of gastroenteritis and typhoid fever in humans ([88][1]), whereas E. coli

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Role of Nonhost Environments in the Lifestyles of Salmonella and Escherichia coli

Mutations in Salmonella typhimurium strains lacking nonspecific acid phosphatase mapped in two unlinked loci One of these, phoP, was cotransducible by phage P22 with purB, whereas the second, phoN, was cotransducible by phage P1 with purA Mutants with temperature-sensitive nonspecific acid phosphatase activity (measured in whole cells) were also isolated A phoN mutant with thermolabile whole-cell activity was isolated directly from wild-type LT-2 Several other mutants with temperature-sensitive enzyme activity were also isolated as revertants of phoN mutants These data suggest that phoN might be a structural locus for nonspecific acid phosphatase The observation that a mutation resulting in high level of nonspecific acid phosphatase mapped in phoP suggests a possible regulatory role for this locus

Regulation of nonspecific acid phosphatase in Salmonella: phoN and phoP genes.

The regulation of three Salmonella typhimurium phosphatases in reponse to different nutritional limitations has been studied. Two enzymes, an acid hexose phosphatase (EC 3.1.3.2) and a cyclic phosphodiesterase (EC 3.1.4.d), appear to be regulated by the cyclic adenosine 3' ,5'-monophosphate (AMP) catabolite repression system. Levels of these enzymes increased in cells grown on poor carbon sources but not in cells grown on poor nitrogen or phosphorus sources. Mutants lacking adenyl cyclase did not produce elevated levels of these enzymes in response to carbon limitation unless cyclic AMP was supplied. Mutants lacking the cyclic AMP receptor protein did not produce elevated levels of these enzymes in response to carbon limitation regardless of the presence of cyclic AMP. Since no specific induction of either enzyme could be demonstrated, these enzymes appear to be controlled solely by the cyclic AMP system. Nonspecific acid phsphatase activity (EC 3.1.3.2) increased in response to carbon, nitrogen, phosphorus, or sulfur limitation. The extent of the increase depended on growth rate, with slower growth rates favoring greater increases, and on the type of limitation. Limitation for either carbon or phosphorus resulted in maximum increases, whereas severe limitation of Mg2+ caused only a slight increase. The increase in nonspecific acid phosphatase during carbon limitation was apparently not mediated by the catabolite repression system since mutants lacking adenyl cyclase or the cyclic AMP receptor protein still produced elevated levels of this enzyme during carbon starvation. Nor did the increase during phosphorus limitation appear to be mediated by the alkaline phosphatase regulatory system. A strain of Salmonella bearing a chromosomal mutation, which caused constitutive production of alkaline phosphatase (introduced by an episome from Escherichia coli), did not have constitutive levels of nonspecific acid phosphatase.

Properties of two phosphatases and a cyclic phosphodiesterase of Salmonella typhimurium.

A survey of Salmonella typhimurium enzymes possessing phosphatase or phosphodiesterase activity was made using several different growth conditions. These studies revealed the presence of three major enzymes, all of which were subsequently purified: a cyclic 2' ,3'-nucleotide phosphodiesterase (EC 3.1.4.d), an acid hexose phosphatase (EC 3.1.3.2), and a nonspecific acid phosphatase (EC 3.1.3.2). A fourth enzyme hydrolyzed bis-(p-nitrophenyl)phosphate but none of the other substrates tested. No evidence was found for the existence of an alkaline phosphatase (EC 3.1.3.1) or a specific 5'-nucleotidase (EC 3.1.3.5) in S. typhimurium LT2. All three phosphatases could be measured efficiently in intact cells, which suggested a periplasmic location; however, they were not readily released by osmotic shock procedures. The nonspecific acid phosphatase, which was purified to apparent homogeneity, yielded a single polypeptide band on both sodium dodecyl sulfate and acidic urea gel electrophoretic systems.

R Weppelman

Papers

Regulation of nonspecific acid phosphatase in Salmonella: phoN and phoP genes.

Properties of two phosphatases and a cyclic phosphodiesterase of Salmonella typhimurium.

Resolution and purification of three periplasmic phosphatases of Salmonella typhimurium.