Evolution under pH stress and high population densities leads to increased density-dependent fitness in the protist Tetrahymena thermophila

AbstractAbiotic stress is a major force of selection that organisms are constantly facing. While the evolutionary effects of various stressors have been broadly studied, it is only more recently that the relevance of interactions between evolution and underlying ecological conditions, that is, eco-evolutionary feedbacks, have been highlighted. Here, we experimentally investigated how populations adapt to pH-stress under high population densities. Using the protist species Tetrahymena thermophila, we studied how four different genotypes evolved in response to stressfully low pH conditions and high population densities. We found that genotypes underwent evolutionary changes, some shifting up and others shifting down their intrinsic rates of increase (r0). Overall, evolution at low pH led to the convergence of r0 and intraspecific competitive ability (α) across the four genotypes. Given the strong correlation between r0 and α, we argue that this convergence was a consequence of selection for increased density-dependent fitness at low pH under the experienced high density conditions. Increased density-dependent fitness was either attained through increase in r0, or decrease of α, depending on the genetic background. In conclusion, we show that demography can influence the direction of evolution under abiotic stress.

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Evolution under pH stress and high population densities leads to increased density‐dependent fitness in the protist Tetrahymena thermophila

Evolution ◽

10.1111/evo.13921 ◽

2020 ◽

Vol 74 (3) ◽

pp. 573-586 ◽

Cited By ~ 2

Author(s):

Felix Moerman ◽

Angelina Arquint ◽

Stefanie Merkli ◽

Andreas Wagner ◽

Florian Altermatt ◽

...

Keyword(s):

Tetrahymena Thermophila ◽

High Population ◽

Population Densities ◽

Density Dependent ◽

Ph Stress

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Transcriptional profiling reveals molecular basis and the role of arginine in response to low-pH stress in Pichia kudriavzevii

10.21203/rs.2.18639/v1 ◽

2019 ◽

Author(s):

Hao Ji ◽

Xiameng Dong ◽

Kailun Zhang ◽

Libo Jin ◽

Renyi Peng ◽

...

Keyword(s):

Organic Acids ◽

Molecular Basis ◽

Transcriptional Profiling ◽

Cell Aggregation ◽

Membrane Lipid ◽

Low Ph ◽

Pichia Kudriavzevii ◽

Ph Stress ◽

Ph Conditions

Abstract BackgroundThe non-conventional yeast Pichia kudriavzevii possesses a unique ability to tolerate various environmental stresses particularly low-pH stress. Thus, it is considered to be a promising biotechnological host for the production of various organic acids under low-pH conditions. However, little is known about the low-pH stress response in P. kudriavzevii, which significantly restricts its future development. ResultsIn this study, P. kudriavzevii JLY1107 showed great tolerance to low-pH stress, but its cell aggregation upon acidic conditions is unfavorable for the development of low-pH fermentation. To explore the molecular basis, we conducted RNA-Seq to compare global gene expression in response to low-pH. Among the 429 differentially expressed genes, the genes associated with regulation of membrane lipid composition, filamentous growth and arginine metabolism were selected for in-depth discussions. The up-regulation of genes associated with arginine uptake and degradation suggests a potential role of arginine in response to low-pH strsss. We therefore present data supporting the hypothesis that P. kudriavzevii maintains intracellular homeostasis by using the ammonia produced by arginine catabolism. Furthermore, external addition of arginine significantly enhances growth and reduces cell aggregation of P. kudriavzevii under low-pH conditions.ConclusionsArginine was demonstrated to be a promising molecule for improving cell growth and preventing cell aggregation under extremely low-pH conditions. Our study is a step towards developing the non-conventional yeast P. kudriavzevii as a platform host for the production of organic acids under low-pH conditions.

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A Two-Component Regulator Mediates Population-Density-Dependent Expression of the Bradyrhizobium japonicum Nodulation Genes

Journal of Bacteriology ◽

10.1128/jb.184.6.1759-1766.2002 ◽

2002 ◽

Vol 184 (6) ◽

pp. 1759-1766 ◽

Cited By ~ 42

Author(s):

John Loh ◽

Dasharath P. Lohar ◽

Brett Andersen ◽

Gary Stacey

Keyword(s):

Gene Expression ◽

Population Density ◽

Conditioned Medium ◽

Bradyrhizobium Japonicum ◽

Response Regulator ◽

High Population ◽

Wild Type ◽

Population Densities ◽

Density Dependent ◽

Culture Density

ABSTRACT Bradyrhizobium japonicum nod gene expression was previously shown to be population density dependent. Induction of the nod genes is highest at low culture density and repressed at high population densities. This repression involves both NolA and NodD2 and is mediated by an extracellular factor found in B. japonicum conditioned medium. NolA and NodD2 expression is maximal at high population densities. We demonstrate here that a response regulator, encoded by nwsB, is required for the full expression of the B. japonicum nodYABC operon. In addition, NwsB is also required for the population-density-dependent expression of both nolA and nodD2. Expression of nolA and nodD2 in the nwsB mutant remained at a basal level, even at high culture densities. The nwsB defect could be complemented by overexpression of a second response regulator, NodW. Consistent with the fact that NolA and NodD2 repress nod gene expression, the expression of a nodY-lacZ fusion in the nwsB mutant was unaffected by culture density. In plant assays with GUS fusions, nodules infected with the wild type showed no nodY-GUS expression. In contrast, nodY-GUS expression was not repressed in nodules infected with the nwsB mutant. Nodule competition assays between the wild type and the nwsB mutant revealed that the addition of conditioned medium resulted in a competitive advantage for the nwsB mutant.

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High environmental temperature and low pH stress alter the gill phenotypic plasticity of Hoven's carp Leptobarbus hoevenii

Journal of Fish Biology ◽

10.1111/jfb.14712 ◽

2021 ◽

Author(s):

Suhaini Mohamad ◽

Hon Jung Liew ◽

Rabiatul Adawiyyah Zainuddin ◽

Sharifah Rahmah ◽

Khor Waiho ◽

...

Keyword(s):

Phenotypic Plasticity ◽

Environmental Temperature ◽

Low Ph ◽

High Environmental Temperature ◽

Ph Stress

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Frequency-dependent interactions determine outcome of competition between two breast cancer cell lines

Scientific Reports ◽

10.1038/s41598-021-84406-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Audrey R. Freischel ◽

Mehdi Damaghi ◽

Jessica J. Cunningham ◽

Arig Ibrahim-Hashim ◽

Robert J. Gillies ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Cell ◽

Critical Density ◽

Low Ph ◽

Breast Cancer Cell Lines ◽

Frequency Dependent ◽

Density Dependent ◽

Low Glucose ◽

Competition Assays ◽

Mcf 7

AbstractTumors are highly dynamic ecosystems in which diverse cancer cell subpopulations compete for space and resources. These complex, often non-linear interactions govern continuous spatial and temporal changes in the size and phenotypic properties of these subpopulations. Because intra-tumoral blood flow is often chaotic, competition for resources may be a critical selection factor in progression and prognosis. Here, we quantify resource competition using 3D spheroid cultures with MDA-MB-231 and MCF-7 breast cancer cells. We hypothesized that MCF-7 cells, which primarily rely on efficient aerobic glucose metabolism, would dominate the population under normal pH and low glucose conditions; and MDA-MB-231 cells, which exhibit high levels of glycolytic metabolism, would dominate under low pH and high glucose conditions. In spheroids with single populations, MCF-7 cells exhibited equal or superior intrinsic growth rates (density-independent measure of success) and carrying capacities (density-dependent measure of success) when compared to MDA-MB-231 cells under all pH and nutrient conditions. Despite these advantages, when grown together, MCF-7 cells do not always outcompete MDA-MB-231 cells. MDA-MB-231 cells outcompete MCF-7 cells in low glucose conditions and coexistence is achieved in low pH conditions. Under all conditions, MDA-MB-231 has a stronger competitive effect (frequency-dependent interaction) on MCF-7 cells than vice-versa. This, and the inability of growth rate or carrying capacity when grown individually to predict the outcome of competition, suggests a reliance on frequency-dependent interactions and the need for competition assays. We frame these results in a game-theoretic (frequency-dependent) model of cancer cell interactions and conclude that competition assays can demonstrate critical density-independent, density-dependent and frequency-dependent interactions that likely contribute to in vivo outcomes.

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Expression patterns of two carbonic anhydrase genes, Na+/K+-ATPase and V-type H+-ATPase, in the freshwater crayfish, Cherax quadricarinatus, exposed to low pH and high pH

Australian Journal of Zoology ◽

10.1071/zo16048 ◽

2017 ◽

Vol 65 (1) ◽

pp. 50 ◽

Cited By ~ 3

Author(s):

Muhammad Yousuf Ali ◽

Ana Pavasovic ◽

Peter B. Mather ◽

Peter J. Prentis

Keyword(s):

Carbonic Anhydrase ◽

Expression Patterns ◽

Maximum Level ◽

Low Ph ◽

Freshwater Crayfish ◽

Α Subunit ◽

Cherax Quadricarinatus ◽

High Ph ◽

Internal Ph ◽

Ph Conditions

Carbonic anhydrase (CA), Na+/K+-ATPase (NKA) and Vacuolar-type H+-ATPase (HAT) play vital roles in osmoregulation and pH balance in decapod crustaceans. As variable pH levels have a significant impact on the physiology of crustaceans, it is crucial to understand the mechanisms by which an animal maintains its internal pH. We examined expression patterns of cytoplasmic (CAc) and membrane-associated form (CAg) of CA, NKA α subunit and HAT subunit a in gills of freshwater crayfish, Cherax quadricarinatus, at three pH levels – 6.2, 7.2 (control) and 8.2 – over 24 h. Expression levels of CAc were significantly increased at low pH and decreased at high pH conditions 24 h after transfer. Expression increased at low pH after 12 h, and reached its maximum level by 24 h. CAg showed a significant increase in expression at 6 h after transfer at low pH. Expression of NKA significantly increased at 6 h after transfer to pH 6.2 and remained elevated for up to 24 h. Expression for HAT and NKA showed similar patterns, where expression significantly increased 6 h after transfer to low pH and remained significantly elevated throughout the experiment. Overall, CAc, CAg, NKA and HAT gene expression is induced at low pH conditions in freshwater crayfish.

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