PROKARYOTIC OSMOREGULATION: Genetics and Physiology

Csonka, László N.; Hanson, Andrew D.

doi:10.1146/annurev.mi.45.100191.003033

Cited by 761 publications

(485 citation statements)

References 99 publications

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“…Glycine betaine (GB) is an important osmoprotectant for many species in all domains of life (17,18,20). The widespread use of GB has been explained, in part, by the superior osmoprotection offered by GB as a compatible solute for many organisms (21).…”

Section: Distribution and Biological Roles Of Choline And Gbmentioning

confidence: 99%

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

Wargo

2013

Appl Environ Microbiol

155

121

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Most sequenced bacteria possess mechanisms to import choline and glycine betaine (GB) into the cytoplasm. The primary role of choline in bacteria appears to be as the precursor to GB, and GB is thought to primarily act as a potent osmoprotectant. Choline and GB may play accessory roles in shaping microbial communities, based on their limited availability and ability to enhance survival under stress conditions. Choline and GB enrichment near eukaryotes suggests a role in the chemical relationships between these two kingdoms, and some of these interactions have been experimentally demonstrated. While many bacteria can convert choline to GB for osmoprotection, a variety of soil-and water-dwelling bacteria have catabolic pathways for the multistep conversion of choline, via GB, to glycine and can thereby use choline and GB as sole sources of carbon and nitrogen. In these choline catabolizers, the GB intermediate represents a metabolic decision point to determine whether GB is catabolized or stored as an osmo-and stress protectant. This minireview focuses on this decision point in Pseudomonas aeruginosa, which aerobically catabolizes choline and can use GB as an osmoprotectant and a nutrient source. P. aeruginosa is an experimentally tractable and ecologically relevant model to study the regulatory pathways controlling choline and GB homeostasis in choline-catabolizing bacteria. The study of P. aeruginosa associations with eukaryotes and other bacteria also makes this a powerful model to study the impact of choline and GB, and their associated regulatory and catabolic pathways, on host-microbe and microbe-microbe relationships.

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Section: Distribution and Biological Roles Of Choline And Gbmentioning

confidence: 99%

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

Wargo

2013

Appl Environ Microbiol

155

121

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“…Since proper maintenance of turgor is essential for cell division and survival, bacteria must have active mechanisms to respond to changes in the environmental osmolarity in order to compete successfully for their ecological niche (8,35). Exposure of Bacillus subtilis to a hypersaline environment incites an integrated physiological adaptation reaction that is aimed at restoring the disturbed cellular water balance, maintaining optimal turgor, and protecting cell components from the detrimental effects of high ionic strength.…”

mentioning

confidence: 99%

“…A more effective defense against these growth conditions is the accumulation of large amounts of osmoprotectants which can be amassed to high intracellular levels without disturbing essential functions of the cell (8,35). One of the most important osmoprotectants is glycine betaine.…”

mentioning

confidence: 99%

“…In contrast, the systems mediating the enzymatic conversion of choline into glycine betaine are only marginally stimulated by an increase in medium osmolarity (4). B. subtilis shares the ability to oxidize choline to glycine betaine for osmoprotective purposes with a number of gram-negative and gram-positive bacteria (8,15,35). This process has been most intensively studied at both the molecular and biochemical levels for E. coli (30,31).…”

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confidence: 99%

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Synthesis of the osmoprotectant glycine betaine in Bacillus subtilis: characterization of the gbsAB genes

et al. 1996

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Synthesis of the osmoprotectant glycine betaine from the exogenously provided precursor choline or glycine betaine aldehyde confers considerable osmotic stress tolerance to Bacillus subtilis in high-osmolarity media. Using an Escherichia coli mutant (betBA) defective in the glycine betaine synthesis enzymes, we cloned by functional complementation the genes that are required for the synthesis of the osmoprotectant glycine betaine in B. subtilis. The DNA sequence of a 4.1-kb segment from the cloned chromosomal B. subtilis DNA was established, and two genes (gbsA and gbsB) whose products were essential for glycine betaine biosynthesis and osmoprotection were identified. The gbsA and gbsB genes are transcribed in the same direction, are separated by a short intergenic region, and are likely to form an operon. The deduced gbsA gene product exhibits strong sequence identity with members of a superfamily of specialized and nonspecialized aldehyde dehydrogenases. This superfamily comprises glycine betaine aldehyde dehydrogenases from bacteria and plants with known involvement in the cellular adaptation to high-osmolarity stress and drought. The deduced gbsB gene product shows significant similarity to the family of type III alcohol dehydrogenases. B. subtilis mutants with defects in the chromosomal gbsAB genes were constructed by marker replacement, and the growth properties of these mutant strains in high-osmolarity medium were analyzed. Deletion of the gbsAB genes destroyed the cholineglycine betaine synthesis pathway and abolished the ability of B. subtilis to deal effectively with high-osmolarity stress in choline-or glycine betaine aldehyde-containing medium. Uptake of radiolabelled choline was unaltered in the gbsAB mutant strain. The continued intracellular accumulation of choline or glycine betaine aldehyde in a strain lacking the glycine betaine-biosynthetic enzymes strongly interfered with the growth of B. subtilis, even in medium of moderate osmolarity. A single transcription initiation site for gbsAB was detected by high-resolution primer extension analysis. gbsAB transcription was initiated from a promoter with close homology to A -dependent promoters and was stimulated by the presence of choline in the growth medium.

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“…Control by turgor is supported by the finding that a sudden increase in medium osmolarity, which reduces turgor, is able to turn on expression of the kdpFABC operon transiently (7,8). This model has been challenged by more recent findings (9,10) demonstrating that there is a difference in expression of kdp-FABC when the osmolarity of the medium is increased by a sugar or a salt. Analysis of mutant forms of KdpD that result in constitutive expression of kdpFABC independent of the K ϩ concentration of the medium but retain the ability to respond to changes in medium osmolarity led to the suggestion that KdpD senses two stimuli, decrease in turgor and K ϩ concentration (11).…”

mentioning

confidence: 99%

Truncation of Amino Acids 12–128 Causes Deregulation of the Phosphatase Activity of the Sensor Kinase KdpD of Escherichia coli

Jung

Altendorf

1998

Journal of Biological Chemistry

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The kdpFABC operon, which encodes the structural genes for the high affinity K ؉ transport complex KdpFABC, is regulated by the sensor kinase KdpD and the response regulator KdpE. KdpD is a bifunctional enzyme catalyzing the autophosphorylation by ATP and the dephosphorylation of the corresponding response regulator KdpE. Here, we demonstrate that the phosphatase activity of KdpD is dependent on ATP, whereas GTP, ITP, CTP, ADP, and GDP have no effect. The phosphatase activity requires only ATP binding, because nonhydrolyzable analogs (adenosine-5 -[␥-thio]triphosphate and adenosine-5 -[␤,␥-imido]triphosphate) work as well. However, KdpD proteins missing amino acids 12-128 are characterized by a phosphatase activity that is independent of ATP. These proteins are still able to respond to K ؉ starvation, but an increase in osmolarity is no longer sensed. Comparison of different KdpD sequences reveals a conserved motif in this amino acid region that is very similar to a classical ATP-binding site (Walker A motif). Replacement of the conserved Gly 37 , Lys 38 , and Thr 39 residues in the consensus ATP-binding sequence results in a KdpD protein that causes a kdp-FABC expression pattern comparable with that seen with KdpD proteins missing amino acids 12-128. However, in vitro phosphatase activity is comparable with that of wild-type KdpD. These results suggest that amino acids 12-128 of KdpD are important for its activity and that an additional ATP-binding site in the Nterminal region seems to be involved in modulation of the phosphatase activity.

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PROKARYOTIC OSMOREGULATION: Genetics and Physiology

Cited by 761 publications

References 99 publications

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

Synthesis of the osmoprotectant glycine betaine in Bacillus subtilis: characterization of the gbsAB genes

Truncation of Amino Acids 12–128 Causes Deregulation of the Phosphatase Activity of the Sensor Kinase KdpD of Escherichia coli

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