A carbon starvation survival gene of Pseudomonas putida is regulated by sigma 54

Abstract

By using mini-Tn5 transposon mutagenesis, two mutants of Pseudomonas putida ATCC 12633 were isolated which showed a marked increase in their sensitivity to carbon starvation; these mutants are presumably affected in the Pex type of proteins that P. putida induces upon carbon starvation (M. Givskov, L. Eberl, and S. Molin, J. Bacteriol. 176:4816-4824, 1994). The affected genes in our mutants were induced about threefold upon carbon starvation. The promoter region of the starvation gene in the mutant MK107 possessed a strong 54 -type promoter sequence, and deletion analysis suggested that this was the major promoter regulating expression; this was confirmed by transcript mapping in rpoN ؉ and rpoN mutant backgrounds. The deletion analysis implicated a sequence upstream of the 54 promoter, as well as a region downstream of the transcription start site, in the functioning of the promoter. Two 70 -type Pribnow boxes were also detected in the promoter region, but their transcriptional activity in the wild type was very weak. However, in a 54 -deficient background, these promoters became stronger. The mechanism and possible physiological role of this phenomenon and the possibility that the sequence upstream of the 54 promoter may have a role in carbon sensing are discussed.Recent studies have established that, contrary to earlier implicit assumptions, the so-called nondifferentiating bacteria do undergo an elaborate process of molecular realignment upon starvation which leads to the development of a resistant cellular state. Such differentiated cells possess markedly enhanced resistance to a variety of individual stresses (21,22). These studies have been most advanced in Escherichia coli (15,25,38), but evidence is accumulating that similar processes operate in marine Vibrio species (43) and in Salmonella typhimurium (50). This differentiation involves expression of several temporal classes of starvation genes that code for special resistance proteins and depends on alternate factors. In E. coli, two factors, 38 and 32 , have been implicated in the starvation response, with the former playing a specially critical role (20,27,40). Evidence has also been presented that these factors are regulated primarily at the posttranscriptional level by a mechanism that involves mRNA secondary structure (32, 39) and that carbon starvation in E. coli might be sensed through the accumulation of homoserine lactone (18).Given the ecological niches of E. coli and S. typhimurium, it is probable that they experience periods of feast and famine. Bacteria in many other habitats probably experience an even greater degree of nutrient scarcity with survival being mostly a matter of coping with prolonged starvation. Members of the genus Pseudomonas inhabit soil and groundwater environments which typically are very nutrient poor (11, 16) and thus belong to the latter class of bacteria. Earlier studies established the remarkable starvation resistance of many species of this genus (8, 36). More recently, Molin and his coworkers have shown that...

Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

“…5), at least under the experimental conditions considered. Previous predictions suggested an RpoN involvement wherever the GG-(N10)-GC motif was present (30,47), but others have documented observations similar to those reported here. For example, in Pseudomonas putida, the presence of the GG-(N10)-GC motif does not always imply RpoN-associated regulation (55), and the lack of functional RpoN in this organism was shown previously to be essentially irrelevant to bacterial environmental responses normally associated with RpoN-controlled regulator functions (5).…”

Regulation of Escherichia coli starvation sigma factor (sigma s) by ClpXP protease

“…Yet 50 or more genes, constituting several temporal classes, have been implicated in starvation-induced development of a resistant cellular state in Escherichia coli (19,25). E. coli has been most intensively studied in this respect, but as similar findings have been made in marine vibrios (18), Salmonella typhimurium (32), and Pseudomonas putida (8,17), development of a generalized resistant state is probably a universal response of bacteria to starvation.…”

The alarmone (p)ppGpp mediates physiological‐responsive control at the σ54‐dependent Po promoter

“…1; Sze et al, 1996). In addition to Po, a number of other 54 promoters have been reported to be growth phase regulated in rich media in an analogous manner, including two promoters from the toluene/xylene catabolic TOL plasmid, Pu and Ps (Hugouvieux-Cotte-Pattat et al, Marqué s et al, 1994;Cases et al, 1996), the PnifH promoter involved in nitrogen assimilation (Cases et al, 1996), the DctD-controlled promoter involved in dicarboxylic acid transport (Gu et al, 1994) and a promoter controlling a carbon starvation survival gene (Kim et al, 1995). Here, we have sought to understand how global regulatory events dominate over the specific regulatory mechanism to achieve such an effect.…”