Simultaneous Accumulation and Degradation of Polyhydroxyalkanoates: Futile Cycle or Clever Regulation?

2009 ◽  
Vol 10 (4) ◽  
pp. 916-922 ◽  
Author(s):  
Qun Ren ◽  
Guy de Roo ◽  
Katinka Ruth ◽  
Bernard Witholt ◽  
Manfred Zinn ◽  
...  
Keyword(s):  
Futile Cycle ◽  
Simultaneous Accumulation

scholarly journals Death by Cystine: an Adverse Emergent Property from a Beneficial Series of Reactions

2015 ◽  
Vol 197 (23) ◽  
pp. 3626-3628 ◽  
Author(s):  
Larry Reitzer
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Sulfur Metabolism ◽  
Emergent Property ◽  
Futile Cycle ◽  
Content Type ◽  
Link Type

In this issue of theJournal of Bacteriology, Chonoles Imlay et al. (K. R. Chonoles Imlay, S. Korshunov, and J. A. Imlay, J Bacteriol 197:3629–3644, 2015,http://dx.doi.org/10.1128/JB.00277-15) show that oxidative stress kills sulfur-restrictedEscherichia coligrown with sublethal H2O2when challenged with cystine. Killing requires rapid and seemingly unregulated cystine transport and equally rapid cystine reduction to cysteine. Cysteine export completes an energy-depleting futile cycle. Each reaction of the cycle could be beneficial. Together, a cystine-mediated vulnerability emerges during the transition from a sulfur-restricted to a sulfur-replete environment, perhaps because of complexities of sulfur metabolism.

scholarly journals Characterization of a Signaling System inStreptococcus mitisThat Mediates Interspecies Communication withStreptococcus pneumoniae

2018 ◽  
Vol 85 (2) ◽  
Author(s):  
R. Junges ◽  
K. Sturød ◽  
G. Salvadori ◽  
H. A. Åmdal ◽  
T. Chen ◽  
...  
Keyword(s):  
Oral Cavity ◽  
Gene Cluster ◽  
Communication System ◽  
Target Genes ◽  
Genetic Mutation ◽  
Signal Molecules ◽  
Streptococcus Mitis ◽  
Futile Cycle ◽  
Content Type ◽  
Surface Polysaccharide

ABSTRACTStreptococcus mitisis found in the oral cavity and nasopharynx and forms a significant portion of the human microbiome. In this study,in silicoanalyses indicated the presence of an Rgg regulator and short hydrophobic peptide (Rgg/SHP) cell-to-cell communication system inS. mitis. Although Rgg presented greater similarity to a repressor inStreptococcus pyogenes, autoinducing assays and genetic mutation analysis revealed that inS. mitisRgg acts as an activator. Transcriptome analysis showed that in addition toshp, the system regulates two other downstream genes, comprising a segment of a putative lantibiotic gene cluster that is in a conjugative element locus in different members of the mitis group. Close comparison to a similar lantibiotic gene cluster inStreptococcus pneumoniaeindicated thatS. mitislacked the full set of genes. Despite the potential of SHP to trigger a futile cycle of autoinduction, growth was not significantly affected for therggmutant under normal or antibiotic stress conditions. TheS. mitisSHP was, however, fully functional in promoting cross-species communication and increasingS. pneumoniaesurface polysaccharide production, which in this species is regulated by Rgg/SHP. The activity of SHPs produced by both species was detected in cocultures using aS. mitisreporter strain. In competitive assays, a slight advantage was observed for therggmutants. We conclude that the Rgg/SHP system inS. mitisregulates the expression of its ownshpand activates an Rgg/SHP system inS. pneumoniaethat regulates surface polysaccharide synthesis. Fundamentally, cross-communication of such systems may have a role during multispecies interactions.IMPORTANCEBacteria secrete signal molecules into the environment which are sensed by other cells when the density reaches a certain threshold. In this study, we describe a communication system inStreptococcus mitis, a commensal species from the oral cavity, which we also found in several species and strains of streptococci from the mitis group. Further, we show that this system can promote cross-communication withS. pneumoniae, a closely related major human pathogen. Importantly, we show that this cross-communication can take place during coculture. While the genes regulated inS. mitisare likely part of a futile cycle of activation, the target genes inS. pneumoniaeare potentially involved in virulence. The understanding of such complex communication networks can provide important insights into the dynamics of bacterial communities.

scholarly journals Quantitation of adenosine-5'-triphosphate used for phosphoinositide metabolism in human erythrocytes

Blood ◽  
1985 ◽  
Vol 66 (5) ◽  
pp. 1133-1137 ◽  
Author(s):  
GL Dale
Keyword(s):  
Steady State ◽  
Human Erythrocyte ◽  
Human Erythrocytes ◽  
Phosphoinositide Metabolism ◽  
Quasi Steady State ◽  
Futile Cycle ◽  
Independent Measure

Abstract The human erythrocyte actively phosphorylates and dephosphorylates phosphatidylinositol present in the membrane in an apparent “futile cycle.” Recent reports have proposed that this phosphorylation/dephosphorylation cycle is a significant consumer of adenosine-5′-triphosphate (ATP) in the erythrocyte. This study details two independent techniques for quantitating the ATP consumed by this phosphoinositide futile cycle. With the first technique a quasi-steady- state labeling of erythrocyte ATP with 32P-phosphate was obtained, and the rate of synthesis of 32P-phosphoinositides was then monitored. The second technique used a novel labeling strategy that allowed only ATP to be labeled with 32P; the transfer of 32P from ATP to phosphoinositides was then an independent measure of the ATP consumed for phosphoinositide synthesis. These two techniques documented that 0.5% to 1.0% of net ATP produced by the erythrocyte is used for phosphoinositide synthesis.

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