A phage-like bacteriocin of Rhizobium trifolii

1973 ◽  
Vol 19 (3) ◽  
pp. 359-368 ◽  
Author(s):  
E. A. Schwinghamer ◽  
C. E. Pankhurst ◽  
P. R. Whitfeld
Keyword(s):  
Phage Type ◽  
Buoyant Density ◽  
Cesium Chloride ◽  
Close Correlation ◽  
Ultraviolet Absorption Spectrum ◽  
Bacterial Cells ◽  
Rhizobium Trifolii ◽  
Bacteriocin Activity ◽  
Double Stranded Dna ◽  
Defective Phage

An inducible bacteriocin produced by a strain of Rhizobium trifolii was partially purified by ammonium sulfate precipitation and differential centrifugation. Examination of fractions of this material banded in sucrose gradients showed a close correlation between bacteriocin activity and presence of phage-like particles observed by electron microscopy. The particles have a head diameter of about 50 nm and have short tails. Buoyant density of intact particles in cesium chloride was 1.46 g/cm3, as compared with 1.49 g/cm3 for a reference rhizobiophage. The apparent nucleoprotein nature of the bacteriocin was confirmed by the ultraviolet absorption spectrum of CsCl-banded material. Double-stranded DNA of density 1.720 g/cm3 (compared with 1.716 g/cm3 for DNA of the phage) was identified in bacteriocin fractions obtained from CsCl density equilibrium gradients. This density was identical with that of DNA from both induced and noninduced bacterial cells of the producing strain. These characteristics and the inability to reproduce in sensitive bacteria identify the bactericidal agent as a large bacteriocin of the defective phage type. Some apparent differences between this bacteriocin and other, partly characterized bacteriocins of R. trifolii are discussed.

Isolation of the Bromouracil-Substituted Light Strand of Mouse Satellite DNA

1973 ◽  
Vol 51 (1) ◽  
pp. 7-10 ◽  
Author(s):  
I. G. Walker ◽  
D. F. Ewart ◽  
A. Chan
Keyword(s):  
Satellite Dna ◽  
Buoyant Density ◽  
Cesium Chloride ◽  
Nucleotide Composition ◽  
Published Data ◽  
Base Pairing ◽  
Distinct Peak ◽  
Double Stranded Dna ◽  
Mouse Satellite Dna ◽  
Light Strand

Mouse L-cells were grown in medium containing bromodeoxyuridine and fluorodeoxyuridine, and the DNA from these cells was centrifuged to equilibrium in alkaline cesium chloride. The bulk of the bromouracil-substituted DNA had a buoyant density lying between 1.82 and 1.85 g/cc. About 4–5% of bromouracil-substituted DNA was observed as a distinct peak with a buoyant density of 1.79 g/cc. After this DNA was purified by recentrifuging, nucleotide analysis revealed an asymmetric composition in which the base-pairing rules for double-stranded DNA were not obeyed. Comparison of the nucleotide composition with published data indicated that the bromouracil-substituted light strand of mouse satellite DNA had been isolated.

scholarly journals A systematic review on improving the biocompatibility of titanium implants using nanoparticles

2020 ◽  
Vol 7 ◽  
pp. 31
Author(s):  
Nthabiseng Nhlapo ◽  
Thywill Cephas Dzogbewu ◽  
Olga de Smidt
Keyword(s):  
Systematic Review ◽  
Antibacterial Properties ◽  
Close Correlation ◽  
Titanium Implants ◽  
Bacterial Cells ◽  
Eligibility Criteria ◽  
Current Systematic Review ◽  
Prisma Statement ◽  
Meta Analyses ◽  
Bio Compatibility

An ideal biomaterial should be biointegratable with minimum adverse immune response. Titanium (Ti) and its alloys are widely used biomaterials for manufacturing clinical implants because of their innate biocompatibility. However, the bioinert property of Ti may hinder tissue–implant integration and its bio compatibility nature allows for attachment of bacterial cells on implant surfaces. Nanoparticles (NPs) have been proposed as a possible intervention to overcome these biological shortcomings of Ti-based implants. The aim of the current systematic review was to identify literature that demonstrates enhanced biocompatibility of Ti-based implants by incorporating NPs. Electronic searches were conducted through the PubMed/MEDLINE, ScienceDirect, Web of Science and EBSCOhost databases. Studies published in English were extracted, without restrictions on the year of publication, using the following keywords: ‘biocompatibility’, ‘nanoparticles’, ‘titanium’ and ‘implant’. The guidelines stipulated in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement were followed. A total of 630 articles were identified in the initial search and upon reviewing, 21 articles were selected according to the eligibility criteria. The selected literature showed robust evidence to support the hypothesis that the inclusion of NPs improves biocompatibility of Ti implants. The studies further indicated a close correlation between biocompatibility and antibacterial properties, of which NPs have been proven to characteristically achieve both.

scholarly journals Mechanism for nuclease regulation in RecBCD

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Martin Wilkinson ◽  
Yuriy Chaban ◽  
Dale B Wigley
Keyword(s):  
Nuclease Activity ◽  
Binding Mode ◽  
Sh3 Domain ◽  
Bacterial Cells ◽  
Dna Breaks ◽  
Nuclease Domain ◽  
Double Stranded Dna ◽  
Large Conformational Change ◽  
Enzyme Complexes ◽  
Dna Substrate

In bacterial cells, processing of double-stranded DNA breaks for repair by homologous recombination is catalysed by AddAB, AdnAB or RecBCD-type helicase-nucleases. These enzyme complexes are highly processive, duplex unwinding and degrading machines that require tight regulation. Here, we report the structure of E.coli RecBCD, determined by cryoEM at 3.8 Å resolution, with a DNA substrate that reveals how the nuclease activity of the complex is activated once unwinding progresses. Extension of the 5’-tail of the unwound duplex induces a large conformational change in the RecD subunit, that is transferred through the RecC subunit to activate the nuclease domain of the RecB subunit. The process involves a SH3 domain that binds to a region of the RecB subunit in a binding mode that is distinct from others observed previously in SH3 domains and, to our knowledge, this is the first example of peptide-binding of an SH3 domain in a bacterial system.

A NON-NUCLEOTIDE POLYMER FOUND IN THE DNA OF THE SAND DOLLAR, ECHINARACHNIUS PARMA: II. PRELIMINARY CHARACTERIZATION

1967 ◽  
Vol 45 (2) ◽  
pp. 281-287 ◽  
Author(s):  
Herbert S. Rosenkranz
Keyword(s):  
Buoyant Density ◽  
Sedimentation Coefficient ◽  
Negative Electrode ◽  
Cesium Chloride ◽  
Amino Sugar ◽  
Electrophoretic Analysis ◽  
Positive Test ◽  
Preliminary Characterization ◽  
Acid Hydrolysate

A preliminary characterization of the non-nucleotidic component present in the DNA of Echinarachnius parma was undertaken. This material has an extremely high sedimentation coefficient (907 S). It contains no deoxyribose and presumably no ribose. After acid hydrolysis it was strongly ninhydrin-positive and also gave positive tests for reducing sugars as well as a slightly positive test for amino sugars. Upon electrophoretic analysis of an acid hydrolysate, three ninhydrinpositive spots were detected. One of these migrated to the negative electrode with a mobility identical with that of galactosamine, the other migrated to the positive electrode, and the third was neutral at pH 6.3. The spot with a mobility identical with that of galactosamine also gave a positive test for amino sugar. The material was not attacked by α-amylase. However, digestion with a crude trypsin preparation resulted in loss of the banding property in gradients of cesium chloride. Exposure to purified trypsin did not completely digest it, but caused an increase in buoyant density.

scholarly journals The quantitation of platelet-associated IgG on cohorts of platelets separated from healthy individuals by buoyant density centrifugation

Blood ◽  
1982 ◽  
Vol 60 (1) ◽  
pp. 136-139 ◽  
Author(s):  
JG Kelton ◽  
G Denomme
Keyword(s):  
Total Protein ◽  
Immune Thrombocytopenia ◽  
Buoyant Density ◽  
Close Correlation ◽  
Progressive Increase ◽  
Current Evidence ◽  
Total Protein Content ◽  
Healthy Individuals ◽  
Platelet Size ◽  
The Mean

Abstract Evidence suggests that as platelets age in the circulation they become progressively smaller and less dense through the loss of protein. The smallest, least dense platelets have a significantly shortened survival, but the mechanism of clearance of these platelets is not known. To evaluate whether the binding of IgG could play a role in the clearance of senescent platelets, we measured platelet size, total protein, and platelet-associated IgG on subpopulations of platelets isolated from 6 healthy individuals using a discontinuous iso-osmotic arabinogalactan (stractan) gradient. There was a close correlation between density, size, and total protein content (r greater than 0.9) for all platelet fractions. There was also a relationship between the amount of platelet-associated IgG (PAIgG), total protein, and platelet size (r greater than 0.9) for the first 3 progressively less dense platelet factions. However, the fourth platelet fraction containing the smallest, least dense, and on current evidence, oldest platelets had very elevated amounts of IgG. This amount was approximately 10 times higher than the mean platelet IgG for the same individual and was similar to the amount of PAIgG found on platelets from patients with immune thrombocytopenia. A progressive increase in the ratio of PAIgG measured after platelet solubilization to PAIgG measured on intact platelets was also noted for the first three populations, indirectly suggesting that platelets clear IgG from their surface during aging. Increased binding of IgG to senescent platelets may mediate their destruction.

Competition between effective and ineffective strains of Rhizobium trifolii in the nodulation of Trifolium subterraneum

1969 ◽  
Vol 20 (5) ◽  
pp. 827 ◽  
Author(s):  
AC Robinson
Keyword(s):  
Competitive Ability ◽  
Root Nodule ◽  
Effective Strain ◽  
Substantial Reduction ◽  
Trifolium Subterraneum ◽  
Bacterial Cells ◽  
Rhizobium Trifolii ◽  
Parallel Study ◽  
Nodule Bacteria ◽  
Tube Culture

The competitive ability of effective and ineffective strains of Rhizobium trifolii to form nodules on two cultivars of Trifolium subterraneum was examined under bacteriologically controlled conditions in tube culture. Seedlings were inoculated with mixtures of known numbers each of effective and of ineffective strains and the strains forming the nodules subsequently determined. In all instances, the effective strains formed a much greater proportion of nodules than would be expected from the relative numbers of each strain in the inoculum. Moreover, a reduction in the numbers of an effective strain relative to the numbers of an ineffective strain failed to result in a corresponding increase in the proportion of nodules formed by an ineffective strain. Instead, the ratio of ineffective to effective strains had to be of the order of 108/104 or wider (c. 10,000/1) before there was a substantial reduction in the number of nodules formed by the effective strains. Even when this ratio was of the order of 108/102, the effective strains still produced some of the nodules. A parallel study of the rates of nodulation of seedlings inoculated with mixtures of strains showed that these rates were characteristic of the proportions of nodules being formed by each strain. Subsequently seedlings were inoculated with mixtures of effective and ineffective strains, and after 66, 90, and 114 hr the roots were surface-sterilized and their contents isolated and identified. Independently of the mixture of strains used, most of the bacterial cells were identified as the effective strains. Because the strains of effective and ineffective bacteria used produce nodules freely when inoculated separately onto these hosts, it is postulated that the hosts distinguished between effective and ineffective strains, and that this recognition is related to compatibility in association with the host. The significance of the results in relation to studies of the root-nodule bacteria is discussed.

scholarly journals A Role for Single-Stranded Exonucleases in the Use of DNA as a Nutrient

2009 ◽  
Vol 191 (11) ◽  
pp. 3712-3716 ◽  
Author(s):  
Vyacheslav Palchevskiy ◽  
Steven E. Finkel
Keyword(s):  
Escherichia Coli ◽  
Bacterial Cells ◽  
Wild Type ◽  
Nutrient Source ◽  
Term Survival ◽  
Natural Competence ◽  
E Coli ◽  
Double Stranded Dna ◽  
Better Than

ABSTRACT Nutritional competence is the ability of bacterial cells to utilize exogenous double-stranded DNA molecules as a nutrient source. We previously identified several genes in Escherichia coli that are important for this process and proposed a model, based on models of natural competence and transformation in bacteria, where it is assumed that single-stranded DNA (ssDNA) is degraded following entry into the cytoplasm. Since E. coli has several exonucleases, we determined whether they play a role in the long-term survival and the catabolism of DNA as a nutrient. We show here that mutants lacking either ExoI, ExoVII, ExoX, or RecJ are viable during all phases of the bacterial life cycle yet cannot compete with wild-type cells during long-term stationary-phase incubation. We also show that nuclease mutants, alone or in combination, are defective in DNA catabolism, with the exception of the ExoX− single mutant. The ExoX− mutant consumes double-stranded DNA better than wild-type cells, possibly implying the presence of two pathways in E. coli for the processing of ssDNA as it enters the cytoplasm.

Sensitivity of some Erwinia carotovora serogroups to macromolecular bacteriocins

1980 ◽  
Vol 26 (9) ◽  
pp. 1023-1028 ◽  
Author(s):  
C. F. Crowley ◽  
S. H. de Boer
Keyword(s):  
Electron Microscopy ◽  
Ammonium Sulfate ◽  
High Speed ◽  
Erwinia Carotovora ◽  
Bacterial Cells ◽  
Bacteriocin Activity ◽  
Specific Absorption ◽  
Ammonium Sulfate Fractionation ◽  
Sulfate Fractionation

Representative strains from each of 18 Erwinia carotovora serogroups were tested for bacteriocin activity. Eight bacteriocin producing strains were found and the bacteriocins partially purified by ammonium sulfate fractionation and high-speed centrifugation. Bacteriocins from all eight strains were morphologically similar to bacteriophage tails. Specific absorption of bacteriocins from one of the antagonistic strains to sensitive bacterial cells was demonstrated with electron microscopy. In four of the serogroups tested each strain was sensitive to only one or two of the bacteriocins while in other serogroups sensitivity varied. Strains of both E. carotovora var. atroseptica and E. carotovora var. carotovora were sensitive to the same bacteriocins, but the two serogroups of var. atroseptica could be differentiated from each other on the basis of sensitivity to one bacteriocin.

scholarly journals A Novel Mite-Transmitted Virus with a Divided RNA Genome Closely Associated with Pigeonpea Sterility Mosaic Disease

2003 ◽  
Vol 93 (1) ◽  
pp. 71-81 ◽  
Author(s):  
P. Lava Kumar ◽  
A. Teifion Jones ◽  
D. V. R. Reddy
Keyword(s):  
Polyclonal Antibodies ◽  
Indian Subcontinent ◽  
Buoyant Density ◽  
Experimental Studies ◽  
Cesium Chloride ◽  
Plant Viruses ◽  
Mosaic Disease ◽  
High Plains ◽  
Virus Species ◽  
Eriophyid Mite

The agent of sterility mosaic, a disease that is a major constraint on pigeonpea (Cajanus cajan) production in the Indian subcontinent, is transmitted by the eriophyid mite, Aceria cajani. This agent has remained elusive for decades despite intensive efforts but we report the isolation of highly flexuous filamentous virus-like particles (VLPs) of 3 to 10 nm in width and of undefined lengths from sterility mosaic disease (SMD)-affected pigeonpea plants. Purified VLP preparations from virus-infected pigeonpea and Nicotiana benthamiana had a buoyant density in cesium chloride of 1.22 to 1.23 g cm-3 and contained a major virus-specific protein species of ≈32 kDa and 5 to 7 RNA species of ≈6.8 to 1.1 kb. The sequence of some complementary DNA clones to RNA from purified VLP preparations had no significant matches in database searches. Two oligonucleotide primers derived from one such sequence, when used in reverse transcriptase-polymerase chain reaction assays, amplified a product of 321 bp specifically from SMD-affected pigeonpea plants. Purified VLP preparations were used to produce polyclonal antibodies that, in infected plants, detected the virus using enzyme-linked immuno-sorbent assay (ELISA) and the virus-specific 32-kDa protein in western immunoblotting (WIB). In such assays, the virus was detected consistently in all SMD-affected pigeonpea plant samples from several different locations in India, but not in samples from symptom-free pigeonpea plants from the same locations. In experimental studies, all pigeonpea plants inoculated with viruliferous A. cajani and those plants graft-inoculated with SMD-affected tissue were infected with the virus as assessed by ELISA and WIB, but not any uninfected pigeonpea plants. This virus, tentatively named Pigeonpea sterility mosaic virus (PPSMV), has some properties similar to virus species in the genera Tospovirus and Tenuivirus and with the eriophyid mite-transmitted High plains virus (HPV) but is distinct from these and from all other characterized viruses. The combination of novel properties shown by PPSMV and HPV suggest that they may constitute species in a new genus of plant viruses.

Buoyant density in cesium chloride of the human reoviruslike agent of infantile gastroenteritis by ultracentrifugation, electron microscopy, and complement fixation

Virology ◽  
1976 ◽  
Vol 70 (2) ◽  
pp. 564-569 ◽  
Author(s):  
Albert Z. Kapikian ◽  
Anthony R. Kalica ◽  
J.Wai-Kuo Shih ◽  
W.Lee Cline ◽  
Thomas S. Thornhill ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Complement Fixation ◽  
Buoyant Density ◽  
Cesium Chloride
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