scholarly journals Self-engineering capabilities of bacteria

2005 ◽  
Vol 3 (6) ◽  
pp. 197-214 ◽  
Author(s):  
Eshel Ben-Jacob ◽  
Herbert Levine
Keyword(s):  
Quorum Sensing ◽  
Environmental Conditions ◽  
Genetic Information ◽  
Autonomous System ◽  
Growth Conditions ◽  
Self Organization ◽  
Natural Growth ◽  
Intracellular Level ◽  
Cell Plasticity ◽  
Additional Information

Under natural growth conditions, bacteria can utilize intricate communication capabilities (e.g. quorum-sensing, chemotactic signalling and plasmid exchange) to cooperatively form (self-organize) complex colonies with elevated adaptability—the colonial pattern is collectively engineered according to the encountered environmental conditions. Bacteria do not genetically store all the information required for creating all possible patterns. Instead, additional information is cooperatively generated as required for the colonial self-organization to proceed. We describe how complex colonial forms (patterns) emerge through the communication-based singular interplay between individual bacteria and the colony. Each bacterium is, by itself, a biotic autonomous system with its own internal cellular informatics capabilities (storage, processing and assessment of information). These afford the cell plasticity to select its response to biochemical messages it receives, including self-alteration and the broadcasting of messages to initiate alterations in other bacteria. Hence, new features can collectively emerge during self-organization from the intracellular level to the whole colony. The cells thus assume newly co-generated traits and abilities that are not explicitly stored in the genetic information of the individuals.

scholarly journals Environmental Regulation of Pseudomonas aeruginosa PAO1 Las and Rhl Quorum-Sensing Systems

2007 ◽  
Vol 189 (13) ◽  
pp. 4827-4836 ◽  
Author(s):  
Kangmin Duan ◽  
Michael G. Surette
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Environmental Conditions ◽  
Transcriptional Regulator ◽  
Transcriptional Regulators ◽  
Growth Conditions ◽  
Fine Tuning ◽  
Relative Timing ◽  
Sensing Systems ◽  
Two Systems

ABSTRACT The lasI-lasR and the rhlI-rhlR quorum-sensing systems in Pseudomonas aeruginosa regulate the expression of numerous cellular and secreted virulence factor genes and play important roles in the development of biofilms. The las and rhl systems themselves are known to be directly or indirectly regulated by a number of transcriptional regulators, and consequently, their expression is sensitive to environmental conditions. In this report, the activities of these two quorum-sensing systems have been examined systematically under 46 growth conditions, and the regulation by environmental conditions has been investigated. The relative timing and strength of expression of these two systems varied significantly under different conditions, which contrasts with the notion of a preset hierarchy with these two systems in P. aeruginosa. Depending on the growth conditions, the correlation between each synthase and its cognate transcriptional regulator also varied, suggesting that the transcription of these genes independently allows for further fine tuning of each system. Finally, we observe that the activities of both the lasI-lasR and the rhlI-rhlR quorum-sensing systems were dramatically enhanced in the presence of extracts of sputum samples from cystic fibrosis patients.

scholarly journals Activity and Toxicity of Farnesol towards Candida albicans Are Dependent on Growth Conditions

2009 ◽  
Vol 54 (2) ◽  
pp. 940-942 ◽  
Author(s):  
Melanie L. Langford ◽  
Sahar Hasim ◽  
Kenneth W. Nickerson ◽  
Audrey L. Atkin
Keyword(s):  
Candida Albicans ◽  
Quorum Sensing ◽  
Environmental Conditions ◽  
Growth Conditions ◽  
Growth Media ◽  
Energy Availability ◽  
Toxic Agent ◽  
Temperature And Growth ◽  
New Variables ◽  
Quorum Sensing Molecule

ABSTRACT Farnesol interacts with Candida albicans as both a quorum-sensing molecule and toxic agent, but confusion abounds regarding which conditions promote these distinct responses. Farnesol sensitivity was measured when inoculum cell history and size, temperature, and growth media were altered. Parameters for farnesol tolerance/sensitivity were defined, validating previous studies and identifying new variables, such as energy availability. This study clearly defines what farnesol concentrations are lethal to C. albicans, based on environmental conditions.

Farnesol restores wild-type colony morphology to 96% of Candida albicans colony morphology variants recovered following treatment with mutagens

Genome ◽  
2006 ◽  
Vol 49 (4) ◽  
pp. 346-353 ◽  
Author(s):  
Ellen C Jensen ◽  
Jacob M Hornby ◽  
Nicole E Pagliaccetti ◽  
Chuleeon M Wolter ◽  
Kenneth W Nickerson ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Quorum Sensing ◽  
Environmental Conditions ◽  
Budding Yeast ◽  
Colony Morphology ◽  
Morphological Transition ◽  
Strongly Correlated ◽  
Wild Type ◽  
Hyphal Morphology

Candida albicans is a diploid fungus that undergoes a morphological transition between budding yeast, hyphal, and pseudohyphal forms. The morphological transition is strongly correlated with virulence and is regulated in part by quorum sensing. Candida albicans produces and secretes farnesol that regulates the yeast to mycelia morphological transition. Mutants that fail to synthesize or respond to farnesol could be locked in the filamentous mode. To test this hypothesis, a collection of C. albicans mutants were isolated that have altered colony morphologies indicative of the presence of hyphal cells under environmental conditions where C. albicans normally grows only as yeasts. All mutants were characterized for their ability to respond to farnesol. Of these, 95.9% fully or partially reverted to wild-type morphology on yeast malt (YM) agar plates supplemented with farnesol. All mutants that respond to farnesol regained their hyphal morphology when restreaked on YM plates without farnesol. The observation that farnesol remedial mutants are so common (95.9%) relative to mutants that fail to respond to farnesol (4.1%) suggests that farnesol activates and (or) induces a pathway that can override many of the morphogenesis defects in these mutants. Additionally, 9 mutants chosen at random were screened for farnesol production. Two mutants failed to produce detectable levels of farnesol.Key words: farnesol-remedial mutants, farnesol-sensing mutants, farnesol-synthesis mutants, quorum sensing, Candida albicans, morphological transition.

scholarly journals Abiotic Stresses Shift Belowground Populus-Associated Bacteria Toward a Core Stress Microbiome

mSystems ◽  
2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Collin M. Timm ◽  
Kelsey R. Carter ◽  
Alyssa A. Carrell ◽  
Se-Ran Jun ◽  
Sara S. Jawdy ◽  
...  
Keyword(s):  
Plant Growth ◽  
Environmental Conditions ◽  
Bacterial Communities ◽  
Abiotic Stresses ◽  
Growth Conditions ◽  
Plant Host ◽  
Associated Bacteria ◽  
Poplar Trees

The identification of a common “stress microbiome” indicates tightly controlled relationships between the plant host and bacterial associates and a conserved structure in bacterial communities associated with poplar trees under different growth conditions. The ability of the microbiome to buffer the plant from extreme environmental conditions coupled with the conserved stress microbiome observed in this study suggests an opportunity for future efforts aimed at predictably modulating the microbiome to optimize plant growth.

scholarly journals Self-organization of active particles by quorum sensing rules

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Bäuerle ◽  
Andreas Fischer ◽  
Thomas Speck ◽  
Clemens Bechinger
Keyword(s):  
Quorum Sensing ◽  
Self Organization ◽  
Active Particles

Putting the Cell in Order

2021 ◽  
pp. 35-50
Author(s):  
Franklin M. Harold
Keyword(s):  
Nucleic Acids ◽  
Genetic Information ◽  
Mother Cell ◽  
General Public ◽  
Chemical Structure ◽  
Interactive Systems ◽  
Self Organization ◽  
Next Generation ◽  
Biological Organization ◽  
Cell Organization

Organization is one of the most conspicuous features of cells. Not only are cells highly ordered (in the sense of regularity and predictability), but also they are organized: their order has purpose, or function. How does biological organization arise, and how is it transmitted from one generation to the next? A key element is genetic information encoded in DNA. Many scientists hold that DNA is the master molecule of life that prescribes all that cells are and do, and the general public has swallowed that doctrine whole. There is truth in this view of biological organization, inasmuch as genes do specify the chemical structure (and thereby the function) of proteins, nucleic acids, and (indirectly) many other biomolecules. But that is only part of an increasingly complex story. The higher levels of cell organization are not spelled out in the genes; they arise by self-organization, and are commonly transmitted to the next generation because the mother cell is architecturally continuous with its daughter. DNA provides an indispensable database, but does not direct the show. Organisms are better understood as complex interactive systems composed of genetically specified elements.

scholarly journals When Unity Is Strength: The Strategies Used by Chlamydomonas to Survive Environmental Stresses

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1307 ◽  
Author(s):  
Félix de Carpentier ◽  
Stéphane D. Lemaire ◽  
Antoine Danon
Keyword(s):  
Environmental Conditions ◽  
Wide Spectrum ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Mild Stress ◽  
Unicellular Alga ◽  
Unicellular Organism ◽  
Unicellular Green Alga ◽  
Scientific Fields ◽  
Do So

The unicellular green alga Chlamydomonas reinhardtii is a valuable model system to study a wide spectrum of scientific fields, including responses to environmental conditions. Most studies are performed under optimal growth conditions or under mild stress. However, when environmental conditions become harsher, the behavior of this unicellular alga is less well known. In this review we will show that despite being a unicellular organism, Chlamydomonas can survive very severe environmental conditions. To do so, and depending on the intensity of the stress, the strategies used by Chlamydomonas can range from acclimation to the formation of multicellular structures, or involve programmed cell death.

Modulation of quorum sensing in Pseudomonas aeruginosa through alteration of membrane properties

Microbiology ◽  
2005 ◽  
Vol 151 (8) ◽  
pp. 2529-2542 ◽  
Author(s):  
Christine Baysse ◽  
Méabh Cullinane ◽  
Valérie Dénervaud ◽  
Elizabeth Burrowes ◽  
J. Maxwell Dow ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Membrane Fluidity ◽  
Environmental Conditions ◽  
Adaptive Response ◽  
Environmental Changes ◽  
Membrane Lipids ◽  
Phospholipid Composition ◽  
Genetically Engineered ◽  
Membrane Properties

Changes in the cellular envelope are major physiological adaptations that occur when micro-organisms encounter extreme environmental conditions. An appropriate degree of membrane fluidity is crucial for survival, and alteration of membrane lipids is an essential adaptive response. Emerging data suggest that microbial cells may recognize alterations in their membrane viscosity resulting from certain environmental changes as a trigger for adaptive cellular responses. In Pseudomonas aeruginosa, the quorum-sensing (QS) system involves a complex regulatory circuitry that coordinates the expression of genes according to a critical population density. Interestingly, it has been shown that the QS system of P. aeruginosa can also be activated by nutritional stress, independently of the cell density, and therefore may be part of a more general adaptive response to stressful environmental conditions. In order to examine the proposed link between membrane properties and stress signalling, the effects of genetically engineered alterations of the membrane phospholipid composition of P. aeruginosa PAO1 on the activation of the stringent response and the QS system were examined. The lptA gene encoding a functional homologue of PlsC, an Escherichia coli enzyme that catalyses the second step of the phospholipid biosynthesis pathway, was identified and disrupted. Inactivation of lptA altered the fatty acid profile of phospholipids and the membrane properties, resulting in decreased membrane fluidity. This resulted in a premature production of the QS signals N-butanoyl- and N-hexanoyl-homoserine lactone (C4-HSL and C6-HSL) and a repression of 2-heptyl-3-hydroxy-4-quinolone (PQS) synthesis at later growth phases. The effects on C4- and C6-HSL depended upon the expression of relA, encoding the (p)ppGpp alarmone synthase, which was increased in the lptA mutant. Together, the findings support the concept that alterations in membrane properties can act as a trigger for stress-related gene expression.

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