scholarly journals Seven Years at High Salinity—Experimental Evolution of the Extremely Halotolerant Black Yeast Hortaea werneckii

2021 ◽  
Vol 7 (9) ◽  
pp. 723
Author(s):  
Cene Gostinčar ◽  
Jason E. Stajich ◽  
Anja Kejžar ◽  
Sunita Sinha ◽  
Corey Nislow ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Pentose Phosphate ◽  
Black Yeast ◽  
Phenotypic Traits ◽  
Extreme Conditions ◽  
Hortaea Werneckii ◽  
Extreme Salinity ◽  
Cellular Machinery ◽  
High Concentrations ◽  
The Cost

The experimental evolution of microorganisms exposed to extreme conditions can provide insight into cellular adaptation to stress. Typically, stress-sensitive species are exposed to stress over many generations and then examined for improvements in their stress tolerance. In contrast, when starting with an already stress-tolerant progenitor there may be less room for further improvement, it may still be able to tweak its cellular machinery to increase extremotolerance, perhaps at the cost of poorer performance under non-extreme conditions. To investigate these possibilities, a strain of extremely halotolerant black yeast Hortaea werneckii was grown for over seven years through at least 800 generations in a medium containing 4.3 M NaCl. Although this salinity is well above the optimum (0.8–1.7 M) for the species, the growth rate of the evolved H. werneckii did not change in the absence of salt or at high concentrations of NaCl, KCl, sorbitol, or glycerol. Other phenotypic traits did change during the course of the experimental evolution, including fewer multicellular chains in the evolved strains, significantly narrower cells, increased resistance to caspofungin, and altered melanisation. Whole-genome sequencing revealed the occurrence of multiple aneuploidies during the experimental evolution of the otherwise diploid H. werneckii. A significant overrepresentation of several gene groups was observed in aneuploid regions. Taken together, these changes suggest that long-term growth at extreme salinity led to alterations in cell wall and morphology, signalling pathways, and the pentose phosphate cycle. Although there is currently limited evidence for the adaptive value of these changes, they offer promising starting points for future studies of fungal halotolerance.

Sorption and desorption of phosphorus by shale: batch and column studies

2010 ◽  
Vol 61 (3) ◽  
pp. 599-606 ◽  
Author(s):  
Johnsely S. Cyrus ◽  
G. B. Reddy
Keyword(s):  
Residence Time ◽  
Flow Rate ◽  
Nutrient Release ◽  
Phosphorus Sorption ◽  
Column Studies ◽  
Desorption Process ◽  
Low Concentrations ◽  
Sorbent Materials ◽  
High Concentrations ◽  
The Cost

Constructed wetland systems have gained attention as attractive solutions for wastewater treatment. Wetlands are not efficient to treat wastewater with high concentrations of phosphorus (P). In order to remove high soluble P loads by wetland, sorbent beds can be added prior to the discharge of wastewater into wetlands. Sorption by sorbent materials is identified as a method for trapping excess P in wastewaters. In the present investigation, shale has been identified as a sorbent material for removal of phosphate (PO4-P) due to the cost effectiveness, stability and possibility of regeneration. The study focuses on the removal of PO4-P from wastewater using shale and the feasibility of using the P-sorbed material as slow-release fertilizer. Phosphorus sorption experiments were conducted by using shale (2 mm and 2–4.7 mm). Results indicate that Shale I (particle size = 2 mm) showed the highest sorption of PO4-P (500 ± 44 mg kg−1). Breakthrough point was reached within 10 h in columns with flow rates of 2 and 3 ml min−1. Lower flow rate of 1 ml min−1 showed an average residence time of about 2 h while columns with a higher flow rate of 3 ml min−1 showed a residence time of about 40 minutes. Variation in flow rate did not influence the desorption process. Since very low concentrations of PO4-P are released, Shale saturated with PO4-P may be used as a slow nutrient release source of P or as a soil amendment. The sorbent can also be regenerated by removing the sorbed PO4-P by using 0.1 N HCl.

scholarly journals Upper Cretaceous Benthic Foraminifera Thriving in Intertidal Areas of the Apennine Carbonate Platform

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Consorti L
Keyword(s):  
Benthic Foraminifera ◽  
Upper Cretaceous ◽  
Carbonate Platform ◽  
Ecological Networks ◽  
Extreme Conditions ◽  
Intertidal Area ◽  
Extreme Salinity

The intertidal area of carbonate platform hosts a complex array of ecological networks in which microbials, algae, cyanobacteria and benthic foraminifera coexist. Being influenced by the amplitude of tides, intertidal areas frequently experience episodes of extreme conditions, including hypersaline waters and elevate daily temperatures. An interesting record of Upper Cretaceous fossil benthic foraminifera found within the intertidal facies of Apennine Carbonate Platform is presented and discussed. Two local gatherings of juvenile Scandonea and adult Rotalispira maxima suggest that the intertidal area was frequently colonized by benthic foraminifera. The results show that these populations of foraminifera were able to tolerate periods of extreme salinity and temperature for reproduction or feeding purposes.

scholarly journals Transport and Catabolism of Pentitols by Listeria monocytogenes

2016 ◽  
Vol 26 (6) ◽  
pp. 369-380 ◽  
Author(s):  
Takfarinas Kentache ◽  
Eliane Milohanic ◽  
Thanh Nguyen Cao ◽  
Abdelhamid Mokhtari ◽  
Francine Moussan Aké ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Pentose Phosphate ◽  
Phosphotransferase System ◽  
Virulence Gene Expression ◽  
Transposon Insertion ◽  
Encoding Gene ◽  
High Concentrations ◽  
Transcription Activators

Transposon insertion into <i>Listeria monocytogenes lmo2665</i>, which encodes an EIIC of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS), was found to prevent <smlcap>D</smlcap>-arabitol utilization. We confirm this result with a deletion mutant and show that Lmo2665 is also required for <smlcap>D</smlcap>-xylitol utilization. We therefore called this protein EIIC<sup>Axl</sup>. Both pentitols are probably catabolized via the pentose phosphate pathway (PPP) because <i>lmo2665</i> belongs to an operon, which encodes the three PTS<sup>Axl</sup> components, two sugar-P dehydrogenases, and most PPP enzymes. The two dehydrogenases oxidize the pentitol-phosphates produced during PTS-catalyzed transport to the PPP intermediate xylulose-5-P. <i>L. monocytogenes</i> contains another PTS, which exhibits significant sequence identity to PTS<sup>Axl</sup>. Its genes are also part of an operon encoding PPP enzymes. Deletion of the EIIC-encoding gene <i>(lmo0508)</i> affected neither <smlcap>D</smlcap>-arabitol nor <smlcap>D</smlcap>-xylitol utilization, although <smlcap>D</smlcap>-arabitol induces the expression of this operon. Both operons are controlled by MtlR/LicR-type transcription activators (Lmo2668 and Lmo0501, respectively). Phosphorylation of Lmo0501 by the soluble PTS<sup>Axl</sup> components probably explains why <smlcap>D</smlcap>-arabitol also induces the second pentitol operon. Listerial virulence genes are submitted to strong repression by PTS sugars, such as glucose. However, <smlcap>D</smlcap>-arabitol inhibited virulence gene expression only at high concentrations, probably owing to its less efficient utilization compared to glucose.

The Effect of Salt Stress on the Catabolism of Sugars in Leaves and Roots of a Mangrove Plant, Avicennia marina

1997 ◽  
Vol 52 (3-4) ◽  
pp. 187-192 ◽  
Author(s):  
Yuko Fukushima ◽  
Hamako Sasamoto ◽  
Shigeyuki Baba ◽  
Hiroshi Ashihara
Keyword(s):  
Malic Acid ◽  
Sea Water ◽  
Tca Cycle ◽  
Avicennia Marina ◽  
Salt Resistance ◽  
Pentose Phosphate ◽  
Neutral Fraction ◽  
Mangrove Plant ◽  
High Concentrations ◽  
Old Trees

Abstract Respiration and related aspects of metabolism were investigated in the roots and leaves of 2-year-old trees of the mangrove plant, Avicennia marina in the presence of 100, 250 and 500 mᴍ NaCl. The rate of respiration of leaves increased with increasing concentrations of NaCl in the incubation medium, but respiration of roots was not similarly affected. In order to examine the relative rates of catabolism of glucose by the glycolysis-tricarboxylic acid (TCA) cycle and the oxidative pentose phosphate pathway (PP pathway), we determined the rates of release of 14CO2 from [1-14C]glucose and from [ 6 -14C]glucose in segments of roots and leaves. The ratios of rates (C6/C1) in roots varied from 0.30 to 0.44, while ratios of 0.85 to 0.99 were obtained when leaves were incubated in the presence of various concentrations of NaCl. It appeared that the PP pathway was more involved in sugar catabolism in the roots than in the leaves of A. marina. Uniformaly 14C-labelled sucrose, incubated with segments of roots and leaves for 18 h, was converted to CO2, amino acids (mainly glutamine), organic acids (mainly malic acid), sugars and ethanol-insoluble macromolecules. The incorporation of radioactivity into most of these components was not significantly affected by NaCl. However, in leaves (but not in roots) the release of 14CO2 from [ U -14C]sucrose was en­ hanced by NaCl at 250 mᴍ and 500 mᴍ, while the rate of incorporation of radioactivity into macromolecules was reduced by high concentrations of NaCl. Incorporation of radioactivity from [ U -14C]sucrose into malic acid was enhanced in both roots and leaves by an increase in the concentration of NaCl from 100 mᴍ to 500 mᴍ (this concentrations is similar to that in sea water). Independent of the concentration of NaCl, more than half of the radioactivity in the neutral fraction from leaves was incorporated into an unidentified sugar, while in the same fraction from roots, the radioactivity was associated with glucose, fructose and sucrose. On the basis of these results, a discussion is presented of the characteristics of catabolism of sugars in A. marina in relation to salt resistance.

scholarly journals Resistance/fitness trade-off is a barrier to the evolution of MarR inactivation mutants in Escherichia coli

2020 ◽  
Vol 76 (1) ◽  
pp. 77-83 ◽  
Author(s):  
Lisa Praski Alzrigat ◽  
Douglas L Huseby ◽  
Gerrit Brandis ◽  
Diarmaid Hughes
Keyword(s):  
Escherichia Coli ◽  
Experimental Evolution ◽  
Efflux Pump ◽  
Drug Susceptibility ◽  
Fitness Cost ◽  
Competitive Growth ◽  
Contributing Factors ◽  
Trade Off ◽  
Compensatory Evolution ◽  
The Cost

Abstract Background Mutations that inactivate MarR reduce susceptibility to ciprofloxacin and competitive growth fitness in Escherichia coli. Both phenotypes are caused by overexpression of the MarA regulon, which includes the AcrAB-TolC drug efflux pump. Objectives We asked whether compensatory evolution could reduce the fitness cost of MarR-inactivating mutations without affecting resistance to ciprofloxacin. Methods The cost of overexpressing the AcrAB-TolC efflux pump was measured independently of MarA overexpression. Experimental evolution of MarR-inactive strains was used to select mutants with increased fitness. The acquired mutations were identified and their effects on drug susceptibility were measured. Results Overexpression of the AcrAB-TolC efflux pump was found not to contribute to the fitness cost of MarA regulon overexpression. Fitness-compensatory mutations were selected in marA and lon. The mutations reduced the level of MarA protein thus reducing expression of the MarA regulon. They restored growth fitness but also reduced resistance to ciprofloxacin. Conclusions The fitness cost caused by overexpression of the MarA regulon has multiple contributing factors. Experimental evolution did not identify any single pump-independent cost factor. Instead, efficient fitness compensation occurred only by mechanisms that reduce MarA concentration, which simultaneously reduce the drug resistance phenotype. This resistance/fitness trade-off is a barrier to the successful spread of MarR inactivation mutations in clinical isolates where growth fitness is essential.

scholarly journals Naso-pharyngeal carriage of Haemophilus influenzae type B

1963 ◽  
Vol 61 (2) ◽  
pp. 247-256 ◽  
Author(s):  
D.C. Turk
Keyword(s):  
Haemophilus Influenzae Type ◽  
High Concentration ◽  
Senior Lecturer ◽  
Parents And Children ◽  
High Concentrations ◽  
Cost Of Materials ◽  
The Cost ◽  
Day Nursery ◽  
The University ◽  
Normal Health

H.influenzae type b, the sero-type which causes meningitis, was isolated from 3 (2·4 %) of 127 naso-pharyngeal swabs from white non-Jamaican children resident in Jamaica, and from 14 (2·9 %) of 473 such swabs from a mixed group of Jamaican children. Much higher frequencies were found in households in which cases of haemophilus meningitis had recently occurred (41 %), in the nursery of an orphan home (up to 70%) and in a day-nursery. In the orphan home nursery the high frequency persisted over a number of months, but no case of meningitis or other relevant disease occurred. A high concentration of this organism is therefore compatible with normal health, and the significance of high concentrations in the homes of meningitis patients is not certain.I am indebted to the Standing Advisory Committee for Medical Research in the British Caribbean for a grant towards the cost of materials; to a number of colleagues at the University College of the West Indies, notably Dr E. H. Back, Senior Lecturer in Paediatrics, and the staff of the Department of Social and Preventive Medicine; to those in charge of the orphan home, the day-nursery, the play-school and the other institutions visited; to many cooperative parents and children and to my wife for help in the collection of specimens.

scholarly journals Exiguobacterium pavilionensis str. N139, a halotolerant, UV-B and metal resistant bacteria from a high-altitude Andean lake

2016 ◽  
Author(s):  
Ana Gutiérrez-Preciado ◽  
Carlos Vargas-Chávez ◽  
Mariana Reyes-Prieto ◽  
Omar F Ordoñez ◽  
Diego Santos-García ◽  
...  
Keyword(s):  
Microbial Community ◽  
High Altitude ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Ultraviolet B ◽  
Resistant Bacteria ◽  
Extreme Conditions ◽  
Tryptophan Biosynthesis ◽  
Ultraviolet B Radiation ◽  
High Concentrations

We report the genome sequence of Exiguobacterium pavilionensis str. N139, isolated from a high-altitude Andean lake. The 2,952,588-bp genome contains one chromosome and three megaplasmids. The genome analysis suggests the presence of enzymes that confer E. pavilionensis str. N139 the ability to grow under multiple environmental extreme conditions, including high concentrations of different metals and high ultraviolet B radiation. Moreover, the regulation of its tryptophan biosynthesis suggests that novel pathways remain to be discovered, and that these pathways might be fundamental in the amino acid metabolism of the microbial community from Laguna Negra, Argentina .

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