Alginate, inorganic polyphosphate, GTP and ppGpp synthesis co-regulated in Pseudomonas aeruginosa: implications for stationary phase survival and synthesis of RNA/DNA precursors

The regulatory protein AlgR2 in Pseudomonas aeruginosa positively regulates nucleoside diphosphate kinase (Ndk) and succinyl-CoA synthetase, enzymes critical in nucleoside triphosphate (NTP) formation. AlgR2 positively regulates the production of alginate, GTP, ppGpp and inorganic polyphosphate (poly P). An algR2 mutant with low levels of these metabolites has them restored by introducing and overexpressing either the algR2 or the ndk gene into the algR2 mutant. Thus, Ndk is involved in the formation of these compounds and largely prevents the death of the algR2 mutant, which occurs early in the stationary phase. We demonstrate that the 12 kDa Ndk–pyruvate kinase (Pk) complex, previously shown to generate predominantly GTP instead of all the NTPs, has a low affinity for the deoxynucleoside diphosphates and cannot generate the dNTPs needed for DNA replication and cell division; this complex may thus be involved in regulating the levels of both NTPs and dNTPs that modulate cell division and survival in the stationary phase.     

Minor indole alkaloids of Alstonia macrophylla

Three indole alkaloids have been isolated from Alstonia macrophylla Wall. Two of these have been identified as affinisine (I) and picrinine (II). The third, a new base designated picralstonine, has been shown to possess structure (III).     

Genetic Basis of the Biodegradation of Salicylate in Pseudomonas

The genetic basis of the biodegradation of salicylate in Pseudomonas putida R1 has been studied. This strain utilizes the meta pathway for oxidizing salicylate through formation of catechol and 2-hydroxymuconic semialdehyde. The enzymes of the meta pathway are induced by salicylate but not by catechol, and the genes specifying these enzymes are clustered. The gene cluster can be eliminated from some salicylate-positive cells by treatment with mitomycin C and appears to exist inside the cell as an extrachromosomal element. This extrachromosomal gene cluster, termed the SAL plasmid, can be transferred by conjugation from P. putida R1 to a variety of other Pseudomonas species.     

Efficacy and specificity of antisense laminin chain-specific expression vectors in blocking laminin induction by TGFβ1: Effect of laminin blockade on TGFβ1-mediated cellular responses

Transforming growth factorβ1 (TGFβ1) elicits a multitude of cellular responses from the epithelial-derived human colon cancer Moser cells. TGFβ1 induces the expression of laminin and fibronectin, and previous studies show that the induction of fibronectin is functionally associated with the regulation of carcinoembryonic antigen (CEA) expression by TGFβ1 (Huang and Chakrabarty, 1994, J Biol Chem 269:28764–28768). In this study we constructed antisense laminin chain-specific expression vectors and determined their efficacy in blocking the expression and the induction of the large multichain laminin molecule by TGFβ1. We also determined the functional role of laminin in several TGFβ1-mediated responses: growth inhibition, downmodulation of anchorage-independent growth, and cellular invasion. Expression of either antisense laminin chain A, B1, or B2 RNA resulted in a downmodulation of endogenous laminin mRNA expression and blocked the induction of laminin protein by TGFβ1 without affecting the induction of other adhesion molecules such as fibronectin or CEA. It is concluded that antisense RNA directed to only one of the laminin chains was sufficient to disrupt the induction of the complex laminin molecule in quite a specific manner. Expression of antisense laminin RNA downregulated cellular adhesion to extracellular matrix (ECM) laminin and blocked the ability of TGFβ1 to upmodulate adhesion to ECM laminin. Expression of antisense laminin RNA, however, did not alter the downregulating effect of TGFβ1 on cellular proliferation, anchorage-independent growth, or cellular invasion, suggesting that the induction of laminin did not play a significant functional role in these TGFβ1-mediated cellular responses. It is likely that other adhesion pathways may be involved in mediating the action of TGFβ1 in this cell line. J. Cell. Physiol. 178:296–303, 1999. © 1999 Wiley-Liss, Inc.