Stringency and relaxation among the halobacteria

Cimmino, Carmen; Scoarughi, Gian Luca; Donini, Pierluigi

doi:10.1128/jb.175.20.6659-6662.1993

Cited by 20 publications

(25 citation statements)

References 20 publications

(9 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In archaea, both relaxed and stringent strains have been observed (3,5,26). In addition, leucine limitation decreased mRNA levels for genes of methanogenesis.…”

Section: Discussionmentioning

confidence: 99%

“…An example of a pathway-specific response is found in the regulation of the trp operon by tryptophan in Methanothermobacter thermautotrophicus, mediated by the TrpY repressor (12,34). On the global level, a subset of archaeal species possesses a stringent response; however, they do not employ the guanosine tetra-and pentaphosphates characteristic of bacterial systems, and the mechanism of stringency in archaea remains unknown (3,5,26).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Global Responses of Methanococcus maripaludis to Specific Nutrient Limitations and Growth Rate

et al. 2008

View full text Add to dashboard Cite

Continuous culture, transcriptome arrays, and measurements of cellular amino acid pools and tRNA charging levels were used to determine the response of Methanococcus maripaludis to leucine limitation. For comparison, the responses to phosphate and H 2 limitations were measured as well. In addition, the effect of growth rate was determined. Leucine limitation resulted in a broad response. tRNA Leu charging decreased, but only small increases in mRNA were seen for amino acid biosynthesis genes. However, the cellular levels of free isoleucine and valine showed significant increases, indicating a coordinate regulation of branched-chain amino acids at a post-mRNA level. Leucine limitation also resulted in increased mRNA abundance for ribosomal protein genes, increased rRNA abundance, and decreased mRNA abundance for genes of methanogenesis. In contrast, phosphate limitation induced a specific response, a marked increase in mRNA levels for a phosphate transporter. Some mRNA levels responded to more than one factor; for example, transcripts for flagellum synthesis genes decreased under conditions of leucine limitation and increased under H 2 limitation. Increased growth rate resulted in increased mRNA levels for ribosomal protein genes, increased rRNA abundance, and increased mRNA for a gene encoding an S-layer protein.

show abstract

“…In archaea, both relaxed and stringent strains have been observed (3,5,26). In addition, leucine limitation decreased mRNA levels for genes of methanogenesis.…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Global Responses of Methanococcus maripaludis to Specific Nutrient Limitations and Growth Rate

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Assay for guanosine polyphosphates. Guanosine polyphosphate production was analyzed by one-dimensional chromatography by the method described by Cimmino et al (6). This technique permits the detection, in a single spot, of about 5 ng of P per 100 mg (dry weight) of cells.…”

Section: Methodsmentioning

confidence: 99%

“…In the wild, these organisms can have either the stringent or the relaxed phenotype, and therefore when the stringent reaction is present, it is not mediated by ppGpp. However, low basal levels of compounds with chromatographic mobilities very similar to that of (p)ppGpp were always observed (6). If these compounds are (p)ppGpp, they must be produced by an alternate pathway, analogous to the relA-independent pathway described in E. coli.…”

mentioning

confidence: 99%

Lack of production of (p)ppGpp in Halobacterium volcanii under conditions that are effective in the eubacteria

1995

Self Cite

View full text Add to dashboard Cite

The stringent halobacterial strain Haloferax volcanii was subjected to a set of physiological conditions different from amino acid starvation that are known to cause production of guanosine polyphosphates [(p)pp Gpp] in eubacteria via the relA-independent (spoT) pathway. The conditions used were temperature upshift, treatment with cyanide, and total starvation. Under none of these conditions were detectable levels of (p)ppGpp observed. This result, in conjunction with our previous finding that (p)ppGpp synthesis does not occur under amino acid starvation, leads to the conclusion that in halobacteria both growth rate control and stringency are probably governed by mechanisms that operate in the absence of ppGpp. During exponential growth, a low level of phosphorylated compounds with electrophoretic mobilities similar, but not identical, to that of (p)ppGpp were observed. The intracellular concentration of these compounds increased considerably during the stationary phase of growth and with all of the treatments used. The compounds were identified as short-chain polyphosphates identical to those found under similar conditions in Saccharomyces cerevisiae.In 1969, Cashel and Gallant reported that wild-type Escherichia coli is capable of producing two unusual compounds originally named magic spots I and II and later identified as guanosine tetra-and pentaphosphates, respectively [collectively referred to as (p)ppGpp] (3). These guanosine nucleotides are generated in a relA-dependent manner by the relA gene product, (p)ppGpp synthetase I, and in a relA-independent manner by the spoT gene product, the SpoT enzyme, which is also implicated in (p)ppGpp degradation. Kinetic studies have shown that pppGpp is formed from GTP, that ppGpp is derived from pppGpp, and that pppGpp inhibits its own synthesis (12).In eubacteria, the rate of stable RNA synthesis at different growth rates is subject to a control mechanism that is distinct from that of other cellular molecules (growth rate control of RNA synthesis). An inverse correlation between the ppGpp concentration, produced in this case by the relA-independent pathway, and the rate of stable RNA synthesis was observed at a wide range of different growth rates (5), which suggested that ppGpp could act as an effector molecule negatively regulating stable RNA synthesis in growth rate control. The isolation by Xiao et al. (21) of relA spoT mutants unable to produce ppGpp permitted Gaal and Gourse (8) to show that ppGpp either is not the mediator or does not act alone, since growth rate control is normal in the double mutants. Hernandez and Bremer have recently shown that in wild-type E. coli, three factors increase with the growth rate: RNA polymerase concentration, RNA polymerase activity, and the distribution of active RNA polymerase between stable and mRNA genes. In an E. coli⌬relA⌬spoT mutant that does not produce ppGpp, RNA polymerase synthesis and activity increase with the growth rate but the distribution of active RNA polymerase between stable and mRNA genes does not. This...

show abstract

“…Archaebacteria also do not apparently form (p)ppGpp (2,12). Mutations that abolish (p)ppGpp accumulation during a stringent response to amino acid starvation have been noted for a marine Vibrio sp.…”

mentioning

confidence: 99%

Functional analysis of a relA/spoT gene homolog from Streptococcus equisimilis

et al. 1996

View full text Add to dashboard Cite

2We examined the functional attributes of a gene encountered by sequencing the streptokinase gene region of Streptococcus equisimilis H46A. This gene, originally called rel, here termed rel S. equisimilis , is homologous to two related Escherichia coli genes, spoT and relA, that function in the metabolism of guanosine 5,3-polyphosphates [(p)ppGpp]. Studies with a variety of E. coli mutants led us to deduce that the highly expressed rel S. equisimilis gene encodes a strong (p)ppGppase and a weaker (p)ppGpp synthetic activity, much like the spoT gene, with a net effect favoring degradation and no complementation of the absence of the relA gene. We verified that the Rel S. equisimilis protein, purified from an E. coli relA spoT double mutant, catalyzed a manganese-activated (p)ppGpp 3-pyrophosphohydrolase reaction similar to that of the SpoT enzyme. This Rel S. equisimilis protein preparation also weakly catalyzed a ribosome-independent synthesis of (p)ppGpp by an ATP to GTP 3-pyrophosphoryltransferase reaction when degradation was restricted by the absence of manganese ions. An analogous activity has been deduced for the SpoT protein from genetic evidence. In addition, the Rel S. equisimilis protein displays immunological cross-reactivity with polyclonal antibodies specific for SpoT but not for RelA. Despite assignment of rel S. equisimilis gene function in E. coli as being similar to that of the native spoT gene, disruptions of rel S. equisimilis in S. equisimilis abolish the parental (p)ppGpp accumulation response to amino acid starvation in a manner expected for relA mutants rather than spoT mutants.As typified by extensive studies with members of the family Enterobacteriacae, bacterial cells subjected to nutrient exhaustion respond with rapid and complex adjustments that involve the metabolism of GTP and GDP analogs bearing pyrophosphate derivatives at the ribose 3Ј-hydroxyl position, collectively abbreviated (p)ppGpp (8). Restriction of accumulation of most stable RNA species, stimulation of certain anabolic activities, and induction of stationary-phase-specific gene expression generally accompany these responses, presumably to facilitate adaptation to the nutritional stress or to ensure cell viability if adaptation is not possible (21).In Escherichia coli, the products of the relA and spoT genes can regulate the accumulation of (p)ppGpp by two apparently independent mechanisms. Synthesis is regulated by the RelA protein, which catalyzes the pyrophosphorylation of GTP (or GDP) using an ATP donor and is activated by codon-specific uncharged tRNA binding to ribosomes engaged in protein synthesis elongation (13,25,26,49). Increased ratios of uncharged to charged tRNA seem to comprise the sole signal for relA-dependent induction of (p)ppGpp synthesis (22). Degradation of (p)ppGpp is inhibited when a primary energy source becomes limiting (17) and leads to (p)ppGpp accumulation without necessarily increasing synthesis; this occurs by inhibiting the activity of a manganese-dependent (p)ppGpp 3Ј-pyrophosphohydrolase...

show abstract

Stringency and relaxation among the halobacteria

Cited by 20 publications

References 20 publications

Global Responses of Methanococcus maripaludis to Specific Nutrient Limitations and Growth Rate

Global Responses of Methanococcus maripaludis to Specific Nutrient Limitations and Growth Rate

Lack of production of (p)ppGpp in Halobacterium volcanii under conditions that are effective in the eubacteria

Functional analysis of a relA/spoT gene homolog from Streptococcus equisimilis

Contact Info

Product

Resources

About