scholarly journals Manganese Is Essential for PlcP Metallophosphoesterase Activity Involved in Lipid Remodeling in Abundant Marine Heterotrophic Bacteria

2018 ◽  
Vol 84 (15) ◽  
Author(s):  
Tao Wei ◽  
Mussa Quareshy ◽  
Yu-zhong Zhang ◽  
David J. Scanlan ◽  
Yin Chen
Keyword(s):  
Marine Bacteria ◽  
Metal Ion ◽  
Cellular Response ◽  
Heterotrophic Bacteria ◽  
Membrane Lipids ◽  
Structural Basis ◽  
P Deficiency ◽  
Content Type ◽  
P Limitation ◽  
Marine Heterotrophic Bacteria

ABSTRACT In vast areas of the ocean, microbes must adapt to the availability of scarce nutrients, and a key strategy for reducing the cellular phosphorus (P) quota is to remodel membranes by replacing phospholipids with non-P surrogate lipids. A metallophosphoesterase, PlcP, is essential for lipid remodeling in cosmopolitan marine bacteria of the Roseobacter (e.g., Phaeobacter sp. strain MED193) and SAR11 (e.g., Pelagibacter sp. strain HTCC7211) clades, and transcription of plcP is known to be induced by P limitation. In order to better understand PlcP-mediated lipid remodeling, we sought to characterize PlcP for its metal ion requirement and to determine its selectivity for native bacterial phospholipids. Here, we report the occurrence of a highly conserved binuclear ion center in PlcPs from MED193 and HTCC7211 and show that manganese is the preferred metal for metallophosphoesterase activity. PlcP displayed high activity towards the major bacterial phospholipids, e.g., phosphatidylglycerol but also phosphatidic acid, a key intermediate in phospholipid biosynthesis. In contrast, phosphatidylserine and phosphatidylinositol, both of which are rare lipids in bacteria, are not preferred substrates. These data suggest that PlcP undertakes a generic lipid remodeling role during the cellular response of marine bacteria to P deficiency and that manganese availability may play a key role in regulating the lipid remodeling process. IMPORTANCE Membrane lipids form the structural basis of all cells. In the marine environment, it is well established that phosphorus availability significantly affects lipid composition in cosmopolitan marine bacteria, whereby non-phosphorus-containing lipids are used to replace phospholipids in response to phosphorus stress. Central to this lipid remodeling pathway is a newly identified phospholipase C-type metallophosphoesterase (PlcP). However, little is known about how PlcP activity is regulated. Here, we determined the role of metal ions in regulating PlcP activity and compared PlcP substrate specificities in PlcP enzymes from two model marine bacteria from the marine Roseobacter clade and the SAR11 clade. Our data provide new insights into the regulation of lipid remodeling in these marine bacteria.

scholarly journals The Mannitol Utilization System of the Marine Bacterium Zobellia galactanivorans

2014 ◽  
Vol 81 (5) ◽  
pp. 1799-1812 ◽  
Author(s):  
Agnès Groisillier ◽  
Aurore Labourel ◽  
Gurvan Michel ◽  
Thierry Tonon
Keyword(s):  
Abc Transporter ◽  
Biochemical Characterization ◽  
Heterotrophic Bacteria ◽  
Dry Weight ◽  
Sole Source ◽  
Content Type ◽  
Wide Range ◽  
Marine Heterotrophic Bacteria ◽  
Operon Gene ◽  
Living Organisms

ABSTRACTMannitol is a polyol that occurs in a wide range of living organisms, where it fulfills different physiological roles. In particular, mannitol can account for as much as 20 to 30% of the dry weight of brown algae and is likely to be an important source of carbon for marine heterotrophic bacteria.Zobellia galactanivorans(Flavobacteriia) is a model for the study of pathways involved in the degradation of seaweed carbohydrates. Annotation of its genome revealed the presence of genes potentially involved in mannitol catabolism, and we describe here the biochemical characterization of a recombinant mannitol-2-dehydrogenase (M2DH) and a fructokinase (FK). Among the observations, the M2DH ofZ. galactanivoranswas active as a monomer, did not require metal ions for catalysis, and featured a narrow substrate specificity. The FK characterized was active on fructose and mannose in the presence of a monocation, preferentially K+. Furthermore, the genes coding for these two proteins were adjacent in the genome and were located directly downstream of three loci likely to encode an ATP binding cassette (ABC) transporter complex, suggesting organization into an operon. Gene expression analysis supported this hypothesis and showed the induction of these five genes after culture ofZ. galactanivoransin the presence of mannitol as the sole source of carbon. This operon for mannitol catabolism was identified in only 6 genomes ofFlavobacteriaceaeamong the 76 publicly available at the time of the analysis. It is not conserved in allBacteroidetes; some species contain a predicted mannitol permease instead of a putative ABC transporter complex upstream of M2DH and FK ortholog genes.

scholarly journals Transcriptional Control in Marine Copiotrophic and Oligotrophic Bacteria with Streamlined Genomes

2016 ◽  
Vol 82 (19) ◽  
pp. 6010-6018 ◽  
Author(s):  
Matthew T. Cottrell ◽  
David L. Kirchman
Keyword(s):  
Marine Bacteria ◽  
Environmental Conditions ◽  
Transcriptional Control ◽  
Heterotrophic Bacteria ◽  
Content Type ◽  
Oligotrophic Bacteria ◽  
Protein Encoding ◽  
Culture Growth ◽  
Ruegeria Pomeroyi ◽  
And Shifts

ABSTRACTBacteria often respond to environmental stimuli using transcriptional control, but this may not be the case for marine bacteria such as “CandidatusPelagibacter ubique,” a cultivated representative of the SAR11 clade, the most abundant organism in the ocean. This bacterium has a small, streamlined genome and an unusually low number of transcriptional regulators, suggesting that transcriptional control is low inPelagibacterand limits its response to environmental conditions. Transcriptome sequencing during batch culture growth revealed that only 0.1% of protein-encoding genes appear to be under transcriptional control inPelagibacterand in another oligotroph (SAR92) whereas >10% of genes were under transcriptional control in the copiotrophsPolaribactersp. strain MED152 andRuegeria pomeroyi. When growth levels changed, transcript levels remained steady inPelagibacterand SAR92 but shifted in MED152 andR. pomeroyi. Transcript abundances per cell, determined using an internal RNA sequencing standard, were low (<1 transcript per cell) for all but a few of the most highly transcribed genes in all four taxa, and there was no correlation between transcript abundances per cell and shifts in the levels of transcription. These results suggest that low transcriptional control contributes to the success ofPelagibacterand possibly other oligotrophic microbes that dominate microbial communities in the oceans.IMPORTANCEDiverse heterotrophic bacteria drive biogeochemical cycling in the ocean. The most abundant types of marine bacteria are oligotrophs with small, streamlined genomes. The metabolic controls that regulate the response of oligotrophic bacteria to environmental conditions remain unclear. Our results reveal that transcriptional control is lower in marine oligotrophic bacteria than in marine copiotrophic bacteria. Although responses of bacteria to environmental conditions are commonly regulated at the level of transcription, metabolism in the most abundant bacteria in the ocean appears to be regulated by other mechanisms.

scholarly journals Antibiofilm activity in the culture supernatant of a marine Pseudomonas sp. bacterium

Microbiology ◽  
2020 ◽  
Vol 166 (3) ◽  
pp. 239-252 ◽  
Author(s):  
Ibtissem Doghri ◽  
Florence Brian-Jaisson ◽  
Marianne Graber ◽  
Alexis Bazire ◽  
Alain Dufour ◽  
...  
Keyword(s):  
Marine Bacteria ◽  
Type Species ◽  
Culture Supernatant ◽  
Heterotrophic Bacteria ◽  
Bioactive Metabolites ◽  
Antibiofilm Activity ◽  
Human Pathogens ◽  
Content Type ◽  
Link Type ◽  
Wide Range

In the marine environment, most solid surfaces are covered by microbial biofilms, mainly composed of bacteria and diatoms. The negative effects of biofilms on materials and equipment are numerous and pose a major problem for industry and human activities. Since marine micro-organisms are an important source of bioactive metabolites, it is possible that they synthesize natural ecofriendly molecules that inhibit the adhesion of organisms. In this work, the antibiofilm potential of marine bacteria was investigated using Flavobacterium sp. II2003 as a target. This strain is potentially a pioneer strain of bacteria that was previously selected from marine biofilms for its strong biofilm-forming ability. The culture supernatants of 86 marine heterotrophic bacteria were tested for their ability to inhibit Flavobacterium sp. II2003 biofilm formation and the Pseudomonas sp. IV2006 strain was identified as producing a strong antibiofilm activity. The Pseudomonas sp. IV2006 culture supernatant (SNIV2006) inhibited Flavobacterium sp. II2003 adhesion without killing the bacteria or inhibiting its growth. Moreover, SNIV2006 had no effect on the Flavobacterium sp. II2003 cell surface hydrophilic/hydrophobic and general Lewis acid–base characteristics, but modified the surface properties of glass, making it on the whole more hydrophilic and more alkaline and significantly reducing bacterial cell adhesion. The glass-coating molecules produced by Pseudomonas sp. IV2006 were found to probably be polysaccharides, whereas the antibiofilm molecules contained in SNIV2006 and acting during the 2 h adhesion step on glass and polystyrene surfaces would be proteinaceous. Finally, SNIV2006 exhibited a broad spectrum of antibiofilm activity on other marine bacteria such as Flavobacterium species that are pathogenic for fish, and human pathogens in both the medical environment, such as Staphylococcus aureus and Pseudomonas aeruginosa , and in the food industry, such as Yersinia enterocolitica . Thus, a wide range of applications could be envisaged for the SNIV2006 compounds, both in aquaculture and human health.

scholarly journals Lipidomics ofThalassiosira pseudonanaunder Phosphorus Stress Reveal Underlying Phospholipid Substitution Dynamics and Novel Diglycosylceramide Substitutes

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
Jonathan E. Hunter ◽  
Joost Brandsma ◽  
Marcus K. Dymond ◽  
Grielof Koster ◽  
C. Mark Moore ◽  
...  
Keyword(s):  
Membrane Lipids ◽  
Thalassiosira Pseudonana ◽  
Content Type ◽  
Biochemical Processes ◽  
Chemical Structures ◽  
P Limitation ◽  
New Type ◽  
Unicellular Organisms ◽  
The Individual ◽  
Successive Generations

ABSTRACTPhytoplankton replace phosphorus-containing lipids (P-lipids) with non-P analogues, boosting growth in P-limited oceans. In the model diatomThalassiosira pseudonana, the substitution dynamics of lipid headgroups are well described, but those of the individual lipids, differing in fatty acid composition, are unknown. Moreover, the behavior of lipids outside the common headgroup classes and the relationship between lipid substitution and cellular particulate organic P (POP) have yet to be reported. We investigated these through the mass spectrometric lipidomics of P-replete (P+) and P-depleted (P−)T. pseudonanacultures. Nonlipidic POP was depleted rapidly by the initiation of P stress, followed by the cessation of P-lipid biosynthesis and per-cell reductions in the P-lipid levels of successive generations. Minor P-lipid degradative breakdown was observed, releasing P for other processes, but most P-lipids remained intact. This may confer an advantage on efficient heterotrophic lipid consumers in P-limited oceans. Glycerophosphatidylcholine (PC), the predominant P-lipid, was similar in composition to its betaine substitute lipid. During substitution, PC was less abundant per cell and was more highly unsaturated in composition. This may reflect underlying biosynthetic processes or the regulation of membrane biophysical properties subject to lipid substitution. Finally, levels of several diglycosylceramide lipids increased as much as 10-fold under P stress. These represent novel substitute lipids and potential biomarkers for the study of P limitationin situ, contributing to growing evidence highlighting the importance of sphingolipids in phycology. These findings contribute much to our understanding of P-lipid substitution, a powerful and widespread adaptation to P limitation in the oligotrophic ocean.IMPORTANCEUnicellular organisms replace phosphorus (P)-containing membrane lipids with non-P substitutes when P is scarce, allowing greater growth of populations. Previous research with the model diatom speciesThalassiosira pseudonanagrouped lipids by polar headgroups in their chemical structures. The significance of the research reported here is threefold. (i) We described the individual lipids within the headgroups during P-lipid substitution, revealing the relationships between lipid headgroups and hinting at the underlying biochemical processes. (ii) We measured total cellular P, placing P-lipid substitution in the context of the broader response to P stress and yielding insight into the implications of substitution in the marine environment. (iii) We identified lipids previously unknown in this system, revealing a new type of non-P substitute lipid, which is potentially useful as a biomarker for the investigation of P limitation in the ocean.

Structures of c-di-GMP/cGAMP degrading phosphodiesterase VcEAL: identification of a novel conformational switch and its implication

2019 ◽  
Vol 476 (21) ◽  
pp. 3333-3353 ◽  
Author(s):  
Malti Yadav ◽  
Kamalendu Pal ◽  
Udayaditya Sen
Keyword(s):  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Triosephosphate Isomerase ◽  
Catalytic Mechanism ◽  
Degradation Mechanism ◽  
Structural Basis ◽  
Conserved Residues ◽  
Phosphodiester Bond ◽  
Cyclic Dinucleotides

Cyclic dinucleotides (CDNs) have emerged as the central molecules that aid bacteria to adapt and thrive in changing environmental conditions. Therefore, tight regulation of intracellular CDN concentration by counteracting the action of dinucleotide cyclases and phosphodiesterases (PDEs) is critical. Here, we demonstrate that a putative stand-alone EAL domain PDE from Vibrio cholerae (VcEAL) is capable to degrade both the second messenger c-di-GMP and hybrid 3′3′-cyclic GMP–AMP (cGAMP). To unveil their degradation mechanism, we have determined high-resolution crystal structures of VcEAL with Ca2+, c-di-GMP-Ca2+, 5′-pGpG-Ca2+ and cGAMP-Ca2+, the latter provides the first structural basis of cGAMP hydrolysis. Structural studies reveal a typical triosephosphate isomerase barrel-fold with substrate c-di-GMP/cGAMP bound in an extended conformation. Highly conserved residues specifically bind the guanine base of c-di-GMP/cGAMP in the G2 site while the semi-conserved nature of residues at the G1 site could act as a specificity determinant. Two metal ions, co-ordinated with six stubbornly conserved residues and two non-bridging scissile phosphate oxygens of c-di-GMP/cGAMP, activate a water molecule for an in-line attack on the phosphodiester bond, supporting two-metal ion-based catalytic mechanism. PDE activity and biofilm assays of several prudently designed mutants collectively demonstrate that VcEAL active site is charge and size optimized. Intriguingly, in VcEAL-5′-pGpG-Ca2+ structure, β5–α5 loop adopts a novel conformation that along with conserved E131 creates a new metal-binding site. This novel conformation along with several subtle changes in the active site designate VcEAL-5′-pGpG-Ca2+ structure quite different from other 5′-pGpG bound structures reported earlier.

New dosimetric approach for multidimensional dose evaluation in gamma knife radiosurgery

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 239-242 ◽  
Author(s):  
R. Foroni ◽  
G. Gambraini ◽  
U. Danesi ◽  
M. Mauri ◽  
E. Pompilio ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Metal Ion ◽  
Light Transmission ◽  
Xylenol Orange ◽  
Ferrous Sulphate ◽  
Gamma Knife Radiosurgery ◽  
Absorbed Dose ◽  
Content Type ◽  
3D Representation ◽  
Fine Print

✓ During the past two decades, the progress in computerized treatment planning systems has led to more accurate imaging and therapy by using the gamma knife, especially with the smallest collimators (4 mm). However, the ionization chambers that have been used to calibrate the gamma knife are not useful with the smallest collimators because the chambers are too big compared with the irradiated volume. Therefore, it is important to develop more suitable dosimeters. This study proposes a new dosimeter method. The FriXyGel method proposed here is based on a phantom dosimeter, an acquisition chain, and dedicated software. This dosimeter uses an agarose gel into which a ferrous sulphate solution (Fricke solution) and a metal ion indicator (xylenol orange) are incorporated. The absorbed dose is detected through measurements of visible light transmission, imaged by means of a charge-coupled device camera provided with a suitable optical filter. Gel layers are imaged before and after irradiation, and the differences in light absorption are related to the absorbed dose. By choosing convenient thickness of gel layers and by building up a phantom with different gel slices, it is possible to obtain a three-dimensional (3D) representation of the absorbed dose. The final 3D representation is reached after several mathematical processes have been applied to the images. The first step identifies and reduces all factors that could alter the original data, such as nonuniformity in illumination. Then, after calibration procedures, it is possible to obtain absorbed dose values and to discover their 3D representation. This goal has been reached by developing appropriate software that performs all the calculations necessary for spatial representation routines and prompt comparison with theoretical calculations.

scholarly journals Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance

2016 ◽  
Vol 198 (7) ◽  
pp. 1087-1100 ◽  
Author(s):  
Gursonika Binepal ◽  
Kamal Gill ◽  
Paula Crowley ◽  
Martha Cordova ◽  
L. Jeannine Brady ◽  
...  
Keyword(s):  
Stress Tolerance ◽  
Streptococcus Mutans ◽  
Transport System ◽  
Biofilm Formation ◽  
Cellular Response ◽  
Pathogenic Bacteria ◽  
Transport Systems ◽  
Content Type ◽  
Growth And Survival ◽  
Dental Biofilm

ABSTRACTPotassium (K+) is the most abundant cation in the fluids of dental biofilm. The biochemical and biophysical functions of K+and a variety of K+transport systems have been studied for most pathogenic bacteria but not for oral pathogens. In this study, we establish the modes of K+acquisition inStreptococcus mutansand the importance of K+homeostasis for its virulence attributes. TheS. mutansgenome harbors four putative K+transport systems that included two Trk-like transporters (designated Trk1 and Trk2), one glutamate/K+cotransporter (GlnQHMP), and a channel-like K+transport system (Kch). Mutants lacking Trk2 had significantly impaired growth, acidogenicity, aciduricity, and biofilm formation. [K+] less than 5 mM eliminated biofilm formation inS. mutans. The functionality of the Trk2 system was confirmed by complementing anEscherichia coliTK2420 mutant strain, which resulted in significant K+accumulation, improved growth, and survival under stress. Taken together, these results suggest that Trk2 is the main facet of the K+-dependent cellular response ofS. mutansto environment stresses.IMPORTANCEBiofilm formation and stress tolerance are important virulence properties of caries-causingStreptococcus mutans. To limit these properties of this bacterium, it is imperative to understand its survival mechanisms. Potassium is the most abundant cation in dental plaque, the natural environment ofS. mutans. K+is known to function in stress tolerance, and bacteria have specialized mechanisms for its uptake. However, there are no reports to identify or characterize specific K+transporters inS. mutans. We identified the most important system for K+homeostasis and its role in the biofilm formation, stress tolerance, and growth. We also show the requirement of environmental K+for the activity of biofilm-forming enzymes, which explains why such high levels of K+would favor biofilm formation.

Sterile shunt malfunction

1984 ◽  
Vol 61 (6) ◽  
pp. 1079-1084 ◽  
Author(s):  
David J. Gower ◽  
Jon C. Lewis ◽  
David L. Kelly
Keyword(s):  
Electron Microscopy ◽  
Cellular Response ◽  
Internal Surface ◽  
Giant Cells ◽  
Shunt Malfunction ◽  
Delayed Hypersensitivity ◽  
Silicone Implants ◽  
Content Type ◽  
Joint Implants ◽  
Delayed Hypersensitivity Reaction

✓ Recently, a delayed hypersensitivity reaction to silicone plastics has been demonstrated in some patients with breast and joint implants and subcutaneously injected silicone. In this study, the authors examined the internal surface of shunting systems to evaluate the cellular response to implanted silicone plastic. The distal peritoneal tubing from 20 patients with ventriculoperitoneal shunts was examined with a scanning electron microscope. Twelve tubes were removed because of documented distal shunt malfunction and eight for an elective lengthening procedure. Cultures of all tubing were negative. The catheters removed for malfunction contained a variety of cells: sometimes in clumps, sometimes associated with platelets and densely adherent to the silicone tubing wall. In several shunts, giant cells were seen with multiple foot processes adherent to the internal silicone surface. The internal surface of the tubing of two malfunctioning shunts was embedded in electron microscopy plastic and studied with transmission electron microscopy. The cells proved to be neutrophils with no evidence of silicone granules inside the cell bodies. The shunts removed for elective revision showed only a few cells, and those were never associated with platelets. There was proteinaceous material scattered on the internal surface of the tubing, but the cellular response was markedly different from that in malfunctioning shunts. The authors postulate that the findings in malfunctioning shunt tubing represent a delayed hypersensitivity to silicone similar to that seen with other types of silicone implants.

scholarly journals Structural Insight into African Swine Fever Virus A179L-Mediated Inhibition of Apoptosis

2017 ◽  
Vol 91 (6) ◽  
Author(s):  
Suresh Banjara ◽  
Sofia Caria ◽  
Linda K. Dixon ◽  
Mark G. Hinds ◽  
Marc Kvansakul
Keyword(s):  
Crystal Structures ◽  
African Swine Fever Virus ◽  
Three Dimensional ◽  
African Swine Fever ◽  
Fever Virus ◽  
Structural Basis ◽  
Dna Virus ◽  
Content Type ◽  
Antiapoptotic Proteins ◽  
Apoptosis Inhibition

ABSTRACT Programmed cell death is a tightly controlled process critical for the removal of damaged or infected cells. Pro- and antiapoptotic proteins of the Bcl-2 family are pivotal mediators of this process. African swine fever virus (ASFV) is a large DNA virus, the only member of the Asfarviridae family, and harbors A179L, a putative Bcl-2 like protein. A179L has been shown to bind to several proapoptotic Bcl-2 proteins; however, the hierarchy of binding and the structural basis for apoptosis inhibition are currently not understood. We systematically evaluated the ability of A179L to bind proapoptotic Bcl-2 family members and show that A179L is the first antiapoptotic Bcl-2 protein to bind to all major death-inducing mammalian Bcl-2 proteins. We then defined the structural basis for apoptosis inhibition of A179L by determining the crystal structures of A179L bound to both Bid and Bax BH3 motifs. Our findings provide a mechanistic understanding for the potent antiapoptotic activity of A179L by identifying it as the first panprodeath Bcl-2 binder and serve as a platform for more-detailed investigations into the role of A179L during ASFV infection. IMPORTANCE Numerous viruses have acquired strategies to subvert apoptosis by encoding proteins capable of sequestering proapoptotic host proteins. African swine fever virus (ASFV), a large DNA virus and the only member of the Asfarviridae family, encodes the protein A179L, which functions to prevent apoptosis. We show that A179L is unusual among antiapoptotic Bcl-2 proteins in being able to physically bind to all core death-inducing mammalian Bcl-2 proteins. Currently, little is known regarding the molecular interactions between A179L and the proapoptotic Bcl-2 members. Using the crystal structures of A179L bound to two of the identified proapoptotic Bcl-2 proteins, Bid and Bax, we now provide a three-dimensional (3D) view of how A179L sequesters host proapoptotic proteins, which is crucial for subverting premature host cell apoptosis.

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