scholarly journals The bar-properties, in particular glucosylation of deoxy-ribonucleic acid, in crosses of bacteriophages T2 and T4

1967 ◽  
Vol 9 (2) ◽  
pp. 149-158 ◽  
Author(s):  
B. de Groot
Keyword(s):  
Protective Effect ◽  
Host Range ◽  
Ribonucleic Acid ◽  
Bacteriophage T4 ◽  
The Other ◽  
New Host ◽  
E Coli ◽  
Marker Rescue ◽  
Single Burst

Analysis of the inheritance of the three bar-properties of bacteriophage T4: exclusion of T2 from the progeny of crosses, glucosylation of the hydroxymethylcytosine (HMC)moiety of the DNA according to T4, and plating with large plaques on E. coli K strains, was carried out by means of marker rescue from T4 by T2 on E. coli K (λh) as a selective indicator. Five of the strains isolated plated with large plaques on K (λh), but did not exclude T2 and showed T2 glucosylation; plating on E. coli K (λh) was found to segregate from the other two bar-properties. The sixth isolate showed, in addition to plating with large plaques on K, partial non-excludability by the parental T4 and T4 glucosylation of HMC. If partial non-excludability is the result of T4 glucosylation, the role of the additional glucose substitutions might be a protective effect on the DNA against the exclusion factor of T4. This proposal is supported by the analysis of the progeny from a single burst from a cross of T4 and T2. The following T2 genes were partially excluded: host-range, no exclusion of parental T2, sensitivity to ultraviolet, and limited plating efficiency on E. coli K (λh). The exclusion factor of T4 is not transmitted to all progeny and does not behave like a bar-property. Only resistance to exclusion and T4 glucosylation were transmitted to all twenty-seven progeny of the single burst. The elimination of sensitivity to exclusion and T2 glucosylation is explained by assuming that the recombinant class with the exclusion factor of T4 and T2 α-glucosylation will exclude itself and be suicidal upon infection of a new host. Exclusion and differential glucosylation are discussed with regard to restriction and modification, respectively.

scholarly journals Hypothesis: A plastically-produced phenotype predicts host specialization and can precede subsequent mutations in bacteriophage

2018 ◽  
Author(s):  
Colin S. Maxwell
Keyword(s):  
Phenotypic Plasticity ◽  
Host Range ◽  
Direct Evidence ◽  
Methylation Pattern ◽  
Host Specialization ◽  
Causal Role ◽  
Direct Test ◽  
New Host ◽  
Restriction Modification

AbstractThe role of phenotypic plasticity in the evolution of new traits is controversial due to a lack of direct evidence. Phage host-range becomes plastic in the presence of restriction-modification (R-M) systems in their hosts. I modeled the evolution of phage host-range in the presence of R-M systems. The model makes two main predictions. First, that offspring of the first phage to gain a new methylation pattern by infecting a new host make up a disproportionate fraction of the subsequent specialist population, indicating that the plastically-produced phenotype is highly predictive of evolutionary outcome. Second, that the first phage gain this pattern is not always genetically distinct from other phages in the population. Taken together, these results suggest that plasticity could play a causal role on par with mutation during the evolution of phage host range. This uniquely tractable system could enable the first direct test of ‘plasticity first’ evolution.

scholarly journals The role of Biofilm for Pseudomonas aeruginosa to resistance ultraviolet and MIC concentration for antibiotics

2012 ◽  
Vol 36 (0A) ◽  
pp. 13-19
Author(s):  
احمد محمد تركي
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
High Resistance ◽  
The Other ◽  
Bacterial Isolates ◽  
Staph Aureus ◽  
E Coli ◽  
The Impact ◽  
And Staphylococcus Aureus

The present study is conducted to in restigate the bacteria Pseudomonas aeruginosa, the impact of ultraviolet on the bacterial isolates under study and the resistance of these isolates to ultraviolet are studied in comparison to two standard isolates ( E . coli and Staphylococcus aureus ) which are considered sensitive to ultraviolet . The natures of the resistance of the isolates, under study, are also being investigated against the different antibiotics. The isolates are subjected to a test to examine their sensitivity to (12) types of antibiotics used routinely in the treatment of various infection of these bacteria. They are (streptomycin , cephalothin ,Gentamycin , cefotaxime ,nitrofurantion ,ampicillin, amoxicillin, rifampin, lincomycin, tetracycline, erythromycin and ciprofloxacin ).The lowest concentration installer ( MIC ) is also testified in accordance with six types of antibiotics (streptomycin, cefotaxime , rifampin , nitrofurantion , Gentamycin , amoxicillin ).The biologic effectiveness of the overlap between the bacterial isolates , under study, is examined against four bacteria (klebseilla pneumonia , Staphylococcus aureus , Enterobacter , Proteus ) The result of using the ultraviolet with different wavelength show the ability of the five local isolates used to resistance of ultraviolet reaching (180 s.) in comparison to the isolates E.coli and staph. aureus in which the ratio of killing is %100 at a time of exposing 40 , 60 sec. respectively. The results indicated that the five local bacterial isolates have high resistance to the most tested antibiotics, It is shouted that all of them have resistance to (erythromycin , tetracycline , lincomycin , Gentamycin ) but they are sensitive towards antibiotic streptomycin . as for the other antibiotics , over can find that the isolates are varied of them for being resisting or sensitive towards them .The results of testing the inhabited effectiveness of the five bacterial isolates towards some other bacterial isolates show the efficiency of the five local isolates in the inhabitation of growth of the five studied bacterial isolates.

scholarly journals BACTERIOPHAGE T4 ENDONUCLEASES II AND IV, OPPOSITELY AFFECTED BY dCMP HYDROXYMETHYLASE ACTIVITY, HAVE DIFFERENT ROLES IN THE DEGRADATION AND IN THE RNA POLYMERASE-DEPENDENT REPLICATION OF T4 CYTOSINE-CONTAINING DNA

Genetics ◽  
1986 ◽  
Vol 114 (3) ◽  
pp. 669-685
Author(s):  
Karin Carlson ◽  
Aud Ȗvervatin
Keyword(s):  
Rna Polymerase ◽  
Dna Synthesis ◽  
Bacteriophage T4 ◽  
The Other ◽  
Wild Type ◽  
E Coli ◽  
Phage Dna ◽  
Dna Template ◽  
Do So

ABSTRACT Bacteriophage T4 mutants defective in gene 56 (dCTPase) synthesize DNA where cytosine (Cyt) partially or completely replaces hydroxymethylcytosine (HmCyt). This Cyt-DNA is degraded in vivo by T4 endonucleases II and IV, and by the exonuclease coded or controlled by genes 46 and 47.—Our results demonstrate that T4 endonuclease II is the principal enzyme initiating degradation of T4 Cyt-DNA. The activity of endonuclease IV, but not that of endonuclease II, was stimulated in the presence of a wild-type dCMP hydroxymethylase, also when no HmCyt was incorporated into phage DNA, suggesting the possibility of direct endonuclease IV-dCMP hydroxymethylase interactions. Endonuclease II activity, on the other hand, was almost completely inhibited in the presence of very small amounts of HmCyt (3-9% of total Cyt + HmCyt) in the DNA. Possible mechanisms for this inhibition are discussed.—The E. coli RNA polymerase modified by the products of T4 genes 33 and 55 was capable of initiating DNA synthesis on a Cyt-DNA template, although it probably cannot do so on an HmCyt template. In the presence of an active endonuclease IV, Cyt-DNA synthesis was arrested 10-30 min after infection, probably due to damage to the template. Cyt-DNA synthesis dependent on the unmodified (33  -  55  -) RNA polymerase was less sensitive to endonuclease IV action.

scholarly journals A broad-host-range event detector: expanding and quantifying performance between Escherichia coli and Pseudomonas species

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Nymul Khan ◽  
Enoch Yeung ◽  
Yuliya Farris ◽  
Sarah J Fansler ◽  
Hans C Bernstein
Keyword(s):  
Escherichia Coli ◽  
Host Range ◽  
Memory Device ◽  
Broad Host Range ◽  
Complex Environments ◽  
New Host ◽  
E Coli ◽  
Pseudomonas Fluorescens Sbw25 ◽  
The Common ◽  
New Applications

Abstract Modern microbial biodesign relies on the principle that well-characterized genetic parts can be reused and reconfigured for different functions. However, this paradigm has only been successful in a limited set of hosts, mostly comprised from common lab strains of Escherichia coli. It is clear that new applications such as chemical sensing and event logging in complex environments will benefit from new host chassis. This study quantitatively compared how the same chemical event logger performed across four strains and three different microbial species. An integrase-based sensor and memory device was operated by two representative soil Pseudomonads—Pseudomonas fluorescens SBW25 and Pseudomonas putida DSM 291. Quantitative comparisons were made between these two non-traditional hosts and two benchmark E. coli chassis including the probiotic Nissle 1917 and common cloning strain DH5α. The performance of sensor and memory components changed according to each host, such that a clear chassis effect was observed and quantified. These results were obtained via fluorescence from reporter proteins that were transcriptionally fused to the integrase and downstream recombinant region and via data-driven kinetic models. The Pseudomonads proved to be acceptable chassis for the operation of this event logger, which outperformed the common E. coli DH5α in many ways. This study advances an emerging frontier in synthetic biology that aims to build broad-host-range devices and understand the context by which different species can execute programmable genetic operations.

scholarly journals Role of the parCBA Operon of the Broad-Host-Range Plasmid RK2 in Stable Plasmid Maintenance

1998 ◽  
Vol 180 (22) ◽  
pp. 6023-6030 ◽  
Author(s):  
Carla L. Easter ◽  
Helmut Schwab ◽  
Donald R. Helinski
Keyword(s):  
Host Range ◽  
Plasmid Stability ◽  
Broad Host Range ◽  
E Coli ◽  
Broad Host Range Plasmid ◽  
Resolution System ◽  
Stable Maintenance ◽  
Plasmid Stabilization ◽  
Plasmid Rk2

ABSTRACT The par region of the stably maintained broad-host-range plasmid RK2 is organized as two divergent operons,parCBA and parDE, and a cis-acting site. parDE encodes a postsegregational killing system, andparCBA encodes a resolvase (ParA), a nuclease (ParB), and a protein of unknown function (ParC). The present study was undertaken to further delineate the role of the parCBA region in the stable maintenance of RK2 by first introducing precise deletions in the three genes and then assessing the abilities of the different constructs to stabilize RK2 in three strains of Escherichia coli and two strains of Pseudomonas aeruginosa. The intact parCBA operon was effective in stabilizing a conjugation-defective RK2 derivative in E. coli MC1061K and RR1 but was relatively ineffective in E. coli MV10Δlac. In the two strains in which the parCBA operon was effective, deletions in parB, parC, or bothparB and parC caused an approximately twofold reduction in the stabilizing ability of the operon, while a deletion in the parA gene resulted in a much greater loss ofparCBA activity. For P. aeruginosaPAO1161Rifr, the parCBA operon provided little if any plasmid stability, but for P. aeruginosaPAC452Rifr, the RK2 plasmid was stabilized to a substantial extent by parCBA. With this latter strain, parAand res alone were sufficient for stabilization. Thecer resolvase system of plasmid ColE1 and theloxP/Cre system of plasmid P1 were tested in comparison with the parCBA operon. We found that, not unlike what was previously observed with MC1061K, cer failed to stabilize the RK2 plasmid with par deletions in strain MV10Δlac, but this multimer resolution system was effective in stabilizing the plasmid in strain RR1. The loxP/Cre system, on the other hand, was very effective in stabilizing the plasmid in all threeE. coli strains. These observations indicate that theparA gene, along with its res site, exhibits a significant level of plasmid stabilization in the absence of theparC and parB genes but that in at least oneE. coli strain, all three genes are required for maximum stabilization. It cannot be determined from these results whether or not the stabilization effects seen with parCBA or thecer and loxP/Cre systems are strictly due to a reduction in the level of RK2 dimers and an increase in the number of plasmid monomer units or if these systems play a role in a more complex process of plasmid stabilization that requires as an essential step the resolution of plasmid dimers.

Witches' Broom disease of Lucerne. I. The occurrence of two strtains of the disease and their relation to big bud of tomato

1957 ◽  
Vol 8 (2) ◽  
pp. 135 ◽  
Author(s):  
K Helms
Keyword(s):  
Host Range ◽  
Host Species ◽  
Virus Disease ◽  
The Other ◽  
Virus Diseases ◽  
New Host ◽  
Broom Disease ◽  
Transmission Studies ◽  
New Host Species

Graft and dodder transmission studies of the witches' broom virus disease of lucerne extended the known host range of the disease to eight new host species. Two selected lucerne plants obtained in the field were found to be infected with distinct strains of the virus. On 14 host species (including tomato and lucerne), one of the two strains (B) produced symptoms that were indistinguishable from those of big bud of tomato. The other strain (A) caused less severe proliferation and did not cause greening of floral parts. The diseases resulting from infection with the strain B witches' broom of lucerne and the big bud virus of tomato are considered to be identical. Symptoms of witches' broom of lucerne in Australia are compared with symptoms of witches' broom of lucerne in America, and with those of some other yellows virus diseases.

scholarly journals Hypothesis: a Plastically Produced Phenotype Predicts Host Specialization and Can Precede Subsequent Mutations in Bacteriophage

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Colin S. Maxwell
Keyword(s):  
Phenotypic Plasticity ◽  
Host Range ◽  
Direct Evidence ◽  
Methylation Pattern ◽  
Host Specialization ◽  
Causal Role ◽  
Direct Test ◽  
New Host ◽  
Restriction Modification

ABSTRACTThe role of phenotypic plasticity in the evolution of new traits is controversial due to a lack of direct evidence. Phage host range becomes plastic in the presence of restriction-modification (R-M) systems in their hosts. I modeled the evolution of phage host range in the presence of R-M systems. The model makes two main predictions. The first prediction is that the offspring of the first phage to gain a new methylation pattern by infecting a new host make up a disproportionate fraction of the subsequent specialist population, indicating that the plastically produced phenotype is highly predictive of evolutionary outcome. The second prediction is that the first phage to gain this pattern is not always genetically distinct from other phages in the population. Taken together, these results suggest that plasticity could play a causal role on par with mutation during the evolution of phage host range. This uniquely tractable system could enable the first direct test of “plasticity first” evolution.

scholarly journals The Escherichia coli Inner Membrane Protein YhiM is Necessary for Efficient Attachment of Bacteriophage T4

Fine Focus ◽  
2018 ◽  
Vol 4 (1) ◽  
pp. 103-114
Author(s):  
M.A. Evans ◽  
P.T. Spieth ◽  
R.L. Sparks-Thissen
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Bacteriophage T4 ◽  
Inner Membrane ◽  
E Coli ◽  
Obligate Intracellular ◽  
Intracellular Parasites ◽  
Acid Shock ◽  
Inner Membrane Protein

Bacteriophages are obligate intracellular parasites, but many of the cellular proteins involved in replication have not been identified. We have tested the role of the inner membrane protein YhiM in bacteriophage replication. YhiM is a conserved (21) membrane protein in Escherichia coli (E. coli) thought to be localized to the cytoplasmic membrane that is necessary for cell survival under conditions of cell stress, including acid shock, low osmolarity and high temperature. We show here that YhiM is necessary for replication of the bacteriophage T4. It also plays a modest role in the replication of T1, T3, and T5 but it does not play a role in the replication of ΦX174. Our data indicated that no replication of T4 occurs in cells missing YhiM. This block in infection is due to a block in attachment of the virus to the cell surface.

scholarly journals A broad-host-range event detector: expanding and quantifying performance across bacterial species

2018 ◽  
Author(s):  
Nymul Khan ◽  
Enoch Yeung ◽  
Yuliya Farris ◽  
Sarah J. Fansler ◽  
Hans C. Bernstein
Keyword(s):  
Escherichia Coli ◽  
Host Range ◽  
Bacterial Species ◽  
Memory Device ◽  
Bench Mark ◽  
Broad Host Range ◽  
Complex Environments ◽  
New Host ◽  
E Coli ◽  
New Applications

ABSTRACTModern microbial biodesign relies on the principle that well-characterized genetic parts can be reused and reconfigured for different functions. However, this paradigm has only been successful in a limited set of hosts, mostly comprised from common lab strains ofEscherichia coli. It is clear that new applications – such as chemical sensing and event logging in complex environments – will benefit from new host chassis. This study quantitatively compared how a chemical event logger performed across multiple microbial species. An integrase-based sensor and memory device was operated by two representative soil Pseudomonads –Pseudomonas fluorescensSBW25 andPseudomonas putidaDSM 291. Quantitative comparisons were made between these two non-traditional hosts and two bench-markEscherichia colichassis including the probiotic Nissle 1917 and common cloning strain DH5α. The performance of sensor and memory components changed according to each host, such that a clear chassis effect was observed and quantified. These results were obtained via fluorescence from reporter proteins that were transcriptionally fused to the integrase and down-stream recombinant region and via data-driven kinetic models. ThePseudomonadsproved to be acceptable chassis for the operation of this event logger, which outperformed the commonE. coliDH5α in many ways. This study advances an emerging frontier in synthetic biology that aims to build broad-host-range devices and understand the context by which different species can execute programmable genetic operations.

scholarly journals Protective Effect of Insulin against Hypoglycemia-Associated Counterregulatory Failure

1999 ◽  
Vol 84 (5) ◽  
pp. 1551-1557 ◽  
Author(s):  
Bernd Fruehwald-Schultes ◽  
Werner Kern ◽  
Eva Deininger ◽  
Peter Wellhoener ◽  
Wolfgang Kerner ◽  
...  
Keyword(s):  
Protective Effect ◽  
Insulin Infusion ◽  
The Other ◽  
Control Group ◽  
Single Episode ◽  
Healthy Men ◽  
Neuroendocrine Response ◽  
Insulin Infusion Rate ◽  
High Insulin

Antecedent hypoglycemic episodes reduce the counterregulatory neuroendocrine response to hypoglycemia. The role of insulin in the mechanism responsible for the antecedent hypoglycemia causing subsequent counterregulatory failure has not been elucidated. We performed antecedent hypoglycemic clamps (56 mg/dL) lasting 2 h with differing degrees of hyperinsulinemia, which were followed by 6-h stepwise hypoglycemic clamps (76–66–56–46 mg/dL) on the next day. Experiments were carried out in 30 young, healthy men. Fifteen of these subjects were tested on 2 occasions. On 1 occasion the antecedent hypoglycemia was induced by insulin infusion at a rate of 1.5 mU/min·kg (low insulin-ante-hypo); on the other occasion the insulin infusion rate was 15.0 mU/min·kg (high insulin-ante-hypo). Both sessions were separated by at least 4 weeks, and their order was balanced across subjects. The remaining 15 subjects (control group) received the same stepwise hypoglycemic clamp as the other subjects, but without antecedent hypoglycemia. During the stepwise hypoglycemic clamp, the counterregulatory increases in ACTH, cortisol, and norepinephrine were significantly blunted after the low insulin-ante-hypo (P < 0.01, P< 0.05, and P < 0.05, respectively) but not after the high insulin-ante-hypo (P = 0.12, P = 0.92, and P = 0.19, respectively) compared to that in the control group. The cortisol, norepinephrine, and glucagon responses were greater after the high than after the low insulin-ante-hypo (all P < 0.05). In conclusion, the present study clearly demonstrates that even a single episode of mild hypoglycemia reduces neuroendocrine counterregulation 18–24 h later. Insulin has a moderate protective effect on subsequent counterregulation.

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