scholarly journals Initiation of Biofilm Formation byPseudomonas aeruginosa 57RP Correlates with Emergence of Hyperpiliated and Highly Adherent Phenotypic Variants Deficient in Swimming, Swarming, and Twitching Motilities

2001 ◽  
Vol 183 (4) ◽  
pp. 1195-1204 ◽  
Author(s):  
Eric Déziel ◽  
Yves Comeau ◽  
Richard Villemur
Keyword(s):  
Environmental Conditions ◽  
Phase Variation ◽  
Growth Conditions ◽  
Phenotypic Traits ◽  
Liquid Cultures ◽  
Environmental Bacterium ◽  
Type Iv ◽  
Large Colony ◽  
Small Colony

ABSTRACT Pseudomonas aeruginosa is a ubiquitous environmental bacterium capable of forming biofilms on surfaces as a survival strategy. It exhibits a large variety of competition/virulence factors, such as three types of motilities: flagellum-mediated swimming, flagellum-mediated swarming, and type IV pilus-mediated twitching. A strategy frequently used by bacteria to survive changing environmental conditions is to create a phenotypically heterogeneous population by a mechanism called phase variation. In this report, we describe the characterization of phenotypic variants forming small, rough colonies that spontaneously emerged when P. aeruginosa 57RP was cultivated as a biofilm or in static liquid cultures. These small-colony (S) variants produced abundant type IV fimbriae, displayed defective swimming, swarming, and twitching motilities, and were impaired in chemotaxis. They also autoaggregated in liquid cultures and rapidly initiated the formation of strongly adherent biofilms. In contrast, the large-colony variant (parent form) was poorly adherent, homogeneously dispersed in liquid cultures, and produced scant polar fimbriae. Further analysis of the S variants demonstrated differences in a variety of other phenotypic traits, including increased production of pyocyanin and pyoverdine and reduced elastase activity. Under appropriate growth conditions, cells of each phenotype switched to the other phenotype at a fairly high frequency. We conclude that these S variants resulted from phase variation and were selectively enriched when P. aeruginosa 57RP was grown as a biofilm or in static liquid cultures. We propose that phase variation ensures the prior presence of phenotypic forms well adapted to initiate the formation of a biofilm as soon as environmental conditions are favorable.

scholarly journals Selection of Unusual Actinomycetal Primary σ70 Factors by Plant-Colonizing Frankia Strains

2004 ◽  
Vol 70 (2) ◽  
pp. 991-998 ◽  
Author(s):  
Céline Lavire ◽  
Didier Blaha ◽  
Benoit Cournoyer
Keyword(s):  
Growth Conditions ◽  
Infection Process ◽  
The Other ◽  
Gene Library ◽  
Pcr Screening ◽  
Liquid Cultures ◽  
Total Dna ◽  
Root Hair Infection ◽  
Selection Of

ABSTRACT Functional adaptations of σ70 transcriptional factors led to the emergence of several paralogous lineages, each one being specialized for gene transcription under particular growth conditions. Screening of a Frankia strain EaI-12 gene library by σ70 DNA probing allowed the detection and characterization of a novel actinomycetal primary (housekeeping) σ70 factor. Phylogenetic analysis positioned this factor in the RpoD cluster of proteobacterial and low-G+C-content gram-positive factors, a cluster previously free of any actinobacterial sequences. σ70 DNA probing of Frankia total DNA blots and PCR screening detected one or two rpoD-like DNA regions per species. rpoD matched the conserved region in all of the species tested. The other region was found to contain sigA, an alternative primary factor. sigA appeared to be strictly distributed among Frankia species infecting plants by the root hair infection process. Both genes were transcribed by Frankia strain ACN14a grown in liquid cultures. The molecular phylogeny of the σ70 family determined with Frankia sequences showed that the alternative actinomycetal factors and the essential ones belonged to the same radiation. At least seven distinct paralogous lineages were observed among this radiation, and gene transfers were detected in the HrdB actinomycetal lineage.

scholarly journals Highly adherent small-colony variants of Pseudomonas aeruginosa in cystic fibrosis lung infection

2003 ◽  
Vol 52 (4) ◽  
pp. 295-301 ◽  
Author(s):  
Susanne Häußler ◽  
Isabell Ziegler ◽  
Alexandra Löttel ◽  
Franz v. Götz ◽  
Manfred Rohde ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Lung Infection ◽  
Growth Conditions ◽  
Twitching Motility ◽  
Small Colony Variants ◽  
Environmental Bacterium ◽  
Small Colony ◽  
Opportunistic Human Pathogen

Pseudomonas aeruginosa, an opportunistic human pathogen and ubiquitous environmental bacterium, is capable of forming specialized bacterial communities, referred to as biofilm. The results of this study demonstrate that the unique environment of the cystic fibrosis (CF) lung seems to select for a subgroup of autoaggregative and hyperpiliated P. aeruginosa small-colony variants (SCVs). These morphotypes showed increased fitness under stationary growth conditions in comparison with clonal wild-types and fast-growing revertants isolated from the SCV population in vitro. In accordance with the SCVs being hyperpiliated, they exhibited increased twitching motility and capacity for biofilm formation. In addition, the SCVs attached strongly to the pneumocytic cell line A549. The emergence of these highly adherent SCVs within the CF lung might play a key role in the pathogenesis of P. aeruginosa lung infection, where a biofilm mode of growth is thought to be responsible for persistent infection.

Colonial variation in Xanthomonas campestris NRRL B-1459 and characterization of the polysaccharide from a variant strain

1976 ◽  
Vol 22 (7) ◽  
pp. 942-948 ◽  
Author(s):  
M. C. Cadmus ◽  
S. P. Rogovin ◽  
K. A. Burton ◽  
J. E. Pittsley ◽  
C. A. Knutson ◽  
...  
Keyword(s):  
Xanthomonas Campestris ◽  
Extracellular Polysaccharide ◽  
Variant Form ◽  
Glucose Content ◽  
Colony Type ◽  
Molar Ratios ◽  
Large Colony ◽  
Predominant Variant ◽  
Small Colony

Stock cultures of Xanthomonas campestris NRRL B-1459 require special attention to maintenance and propagation to assure consistent production in good yields of the extracellular polysaccharide xanthan. Under customary conditions of propagative maintenance on agar slants, variant colony types develop that are smaller in size than the normal type. The rate of regression of the normal to the variant forms was diminished when the D-glucose content of the stock medium was sufficient to avoid depletion during storage and when transfer to fresh medium was reduced to 14-day intervals. Under conditions for polysaccharide production, the normal large-colony type gives crude culture liquors after 48 h of 7000 centipoise (cp) viscosity; the predominant variant form gives only 4000 cp. On the basis of 2.1% initial D-glucose, biopolymer yields for the normal and variant strains were 62 and 43%, respectively. Polysaccharide produced by the variant (small-colony type) differs adversely in solution properties from that of the parent strain (large-colony type); it differs also in its lower content of pyruvic acid and O-acetyl substituents. The molar ratios of constituent sugars (D-glucose, D-mannose, and D-glucuronic acid), however, were identical in polysaccharides with the normal and variant strains. Exclusion of colonial variants from fermentations is prerequisite to production of xanthan optimum in properties and yield.

scholarly journals Predictive analytics of environmental adaptability in multi-omic network models

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Claudio Angione ◽  
Pietro Lió
Keyword(s):  
Codon Usage ◽  
Environmental Conditions ◽  
Metabolic Response ◽  
Predictive Analytics ◽  
Network Models ◽  
Growth Conditions ◽  
Phenotypic Traits ◽  
Bacterial Strains ◽  
Experimental Conditions ◽  
Metabolic Markers

Abstract Bacterial phenotypic traits and lifestyles in response to diverse environmental conditions depend on changes in the internal molecular environment. However, predicting bacterial adaptability is still difficult outside of laboratory controlled conditions. Many molecular levels can contribute to the adaptation to a changing environment: pathway structure, codon usage, metabolism. To measure adaptability to changing environmental conditions and over time, we develop a multi-omic model of Escherichia coli that accounts for metabolism, gene expression and codon usage at both transcription and translation levels. After the integration of multiple omics into the model, we propose a multiobjective optimization algorithm to find the allowable and optimal metabolic phenotypes through concurrent maximization or minimization of multiple metabolic markers. In the condition space, we propose Pareto hypervolume and spectral analysis as estimators of short term multi-omic (transcriptomic and metabolic) evolution, thus enabling comparative analysis of metabolic conditions. We therefore compare, evaluate and cluster different experimental conditions, models and bacterial strains according to their metabolic response in a multidimensional objective space, rather than in the original space of microarray data. We finally validate our methods on a phenomics dataset of growth conditions. Our framework, named METRADE, is freely available as a MATLAB toolbox.

scholarly journals Morphophysiological and molecular characterization of millet (Panicum miliaceum L.) varieties for crop improvement in Western Europe

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Massimo Vischi ◽  
Nicola Zorzin ◽  
Maria Bernhart ◽  
Johanna Winkler ◽  
Dipak Santra ◽  
...  
Keyword(s):  
Western Europe ◽  
Crop Improvement ◽  
Genetic Distances ◽  
Phenotypic Traits ◽  
Panicum Miliaceum ◽  
Novel Foods ◽  
Proso Millet ◽  
Ne Italy ◽  
The Usa

Abstract Background Global warming and issues in favour of a more sustainable agriculture suggest a reconsideration of minor cereals in European agrosystems. Compared to other summer crops, proso millet has a remarkable drought resistance and could be used to improve crop rotation and biodiversity. Proso millet is also increasingly sought by industry to produce novel foods such as those designed for coeliac patients. In this study, a thorough characterization of 11, commercially available, proso millet (Panicum miliaceum L.) varieties was carried out as a preliminary step for crop reintroduction and breeding in Western Europe. Methods The cultivars under evaluation were introduced from Austria, Poland, Russia, and the USA (University of Nebraska–Lincoln). Plants were grown at Udine (NE Italy) and Gleisdorf (Styria, Austria), under greenhouse and field conditions, respectively. Yield components and a range of morphophysiological characters were recorded in both locations. In parallel, 85 SSR markers were tested on DNA samples extracted from randomly chosen plants of each variety and the 12 responsive markers used to genotype the whole variety set. Results Morphometric analyses showed that varieties have several diverging phenotypic traits and architectures. In all instances, yields recorded at field level were much lower than potential yields. In this respect, US selections were comparable to earlier developed European varieties, suggesting that breeding for an increased adaptation is the keystone for a stable reintroduction of millet in Western Europe. Molecular analyses uncovered remarkably low genetic differences and heterozygosity levels within cultivars, confirming millet as an essentially autogamous species; in contrast, large genetic distances were noted among cultivars selected in different environments. Results of SSR genotyping combined with those originating from phenotypic analyses indicated possible crosses to source the genetic variability necessary for selection. Conclusions This study enabled the identification of cultivars that could be used to revitalize the crop in Western Europe and to produce genetically variable hybrid progenies exploitable by breeding.

scholarly journals Cryo-ET Characterization of Novel Cellular Extrusions in Escherichia coli Induced by the Major Subunit Protein of Type IV Pili, PilA, from Pseudomonas aeruginosa

2021 ◽  
Vol 27 (S1) ◽  
pp. 280-282
Author(s):  
Juan Sanchez ◽  
Daniel Parrell ◽  
Alba Gonzalez-Rivera ◽  
Nicoleta Ploscariu ◽  
Katrina Forest ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Type Iv Pili ◽  
Subunit Protein ◽  
Type Iv

Growth of GaN without Yellow Luminescence

1995 ◽  
Vol 395 ◽  
Author(s):  
X. Zhang ◽  
P. Kung ◽  
D. Walker ◽  
A. Saxler ◽  
M. Razeghi
Keyword(s):  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Deep Level ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Native Defect ◽  
Yellow Luminescence ◽  
Gallium Vacancy ◽  
Rich Condition

ABSTRACTWe report the growth and photoluminescence characterization of GaN grown on different substrates and under different growth conditions using metalorganic chemical vapor deposition. The deep-level yellow luminescence centered at around 2.2eV is attributed to native defect, most possibly the gallium vacancy. The yellow luminescence can be substantially reduced By growing GaN under Ga-rich condition or doping GaN with Ge or Mg.

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