Effect of cadmium on particle clearence by the Sydney rock oyster, Saccostrea commercialis (I. & R.)

1982 ◽  
Vol 33 (4) ◽  
pp. 711 ◽  
Author(s):  
TJ Ward
Keyword(s):  
Escherichia Coli ◽  
Small Proportion ◽  
Natural Populations ◽  
Sublethal Effect ◽  
E Coli ◽  
Rock Oyster ◽  
Particle Clearance ◽  
Growth And Reproduction

Sydney rock oysters, S. commercialis (I. & R.); were exposed to a control and 10. 50 and 100 �g 1-1 cadmium in a flowing seawater system in the laboratory for 45 days. After this period the rates of particle clearance, assessed by using killed 14C-labelled Escherichia coli in suspension, were determined for each group of oysters. A small proportion of 14C-label from the E. coli was recovered from the non-gut tissues of the oyster, suggesting that the oyster digested, and may have derived some energy from, the bacteria. All cadmium- treated oysters displayed reduced efficiency of clearance compared to controls. If this sublethal effect of cadmium occurs in natural populations, oysters could suffer impaired feeding efficiencies with subsequent effects on growth and reproduction.

scholarly journals IS103, a new insertion element in Escherichia coli: characterization and distribution in natural populations.

Genetics ◽  
1989 ◽  
Vol 121 (3) ◽  
pp. 423-431 ◽  
Author(s):  
B G Hall ◽  
L L Parker ◽  
P W Betts ◽  
R F DuBose ◽  
S A Sawyer ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Copy Number ◽  
Insertion Sequence ◽  
Natural Populations ◽  
Single Copy ◽  
Target Sequence ◽  
Wild Type ◽  
Insertion Element ◽  
E Coli ◽  
Natural Isolates

Abstract IS103 is a previously unknown insertion sequence found in Escherichia coli K12. We have sequenced IS103 and find that it is a 1441-bp element that consists of a 1395-bp core flanked by imperfect 23-bp inverted repeats. IS103 causes a 6-bp duplication of the target sequence into which it inserts. There is a single copy of IS103 present in wild-type E. coli K12 strain HfrC. In strain X342 and its descendents there are two additional copies, one of which is located within the bglF gene. IS103 is capable of excising from within bglF and restoring function of that gene. IS103 exhibits 44% sequence identity with IS3, suggesting that the two insertion sequences are probably derived from a common ancestor. We have examined the distribution of IS103 in the chromosomes and plasmids of the ECOR collection of natural isolates of E. coli. IS103 is found in 36 of the 71 strains examined, and it strongly tends to inhabit plasmids rather than chromosomes. Comparison of the observed distribution of IS103 with distributions predicted by nine different models for the regulation of transposition according to copy number and of the effects of copy number on fitness suggest that transposition of IS103 is strongly regulated and that it has only minor effects on fitness. The strong clustering of IS103 within one phylogenetic subgroup of the E. coli population despite its presence on plasmids suggests that plasmids tend to remain within closely related strains and that transfer to distantly related strains is inhibited.

scholarly journals Frequency and Distribution of Tetracycline Resistance Genes in Genetically Diverse, Nonselected, and Nonclinical Escherichia coli Strains Isolated from Diverse Human and Animal Sources

2004 ◽  
Vol 70 (4) ◽  
pp. 2503-2507 ◽  
Author(s):  
Andrew Bryan ◽  
Nir Shapir ◽  
Michael J. Sadowsky
Keyword(s):  
Escherichia Coli ◽  
Resistance Genes ◽  
Natural Populations ◽  
Tetracycline Resistance ◽  
First Report ◽  
E Coli ◽  
Tetracycline Resistance Genes ◽  
Resistance Determinants

ABSTRACT Nonselected and natural populations of Escherichia coli from 12 animal sources and humans were examined for the presence and types of 14 tetracycline resistance determinants. Of 1,263 unique E. coli isolates from humans, pigs, chickens, turkeys, sheep, cows, goats, cats, dogs, horses, geese, ducks, and deer, 31% were highly resistant to tetracycline. More than 78, 47, and 41% of the E. coli isolates from pigs, chickens, and turkeys were resistant or highly resistant to tetracycline, respectively. Tetracycline MICs for 61, 29, and 29% of E. coli isolates from pig, chickens, and turkeys, respectively, were ≥233 μg/ml. Muliplex PCR analyses indicated that 97% of these strains contained at least 1 of 14 tetracycline resistance genes [tetA, tetB, tetC, tetD, tetE, tetG, tetK, tetL, tetM, tetO, tetS, tetA(P), tetQ, and tetX] examined. While the most common genes found in these isolates were tetB (63%) and tetA (35%), tetC, tetD, and tetM were also found. E. coli isolates from pigs and chickens were the only strains to have tetM. To our knowledge, this represents the first report of tetM in E. coli.

Antimicrobial peptide bsn-37 inhibits the growth of Escherichia coli by targeting its cell wall and membrane

2020 ◽  
Vol 10 (8) ◽  
pp. 1260-1264
Author(s):  
Jingyu Fu ◽  
Hao Yang ◽  
Hongliang Wang ◽  
Jun Ke ◽  
Debao Kong
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Antimicrobial Peptides ◽  
Nucleic Acids ◽  
Antimicrobial Peptide ◽  
Mechanism Of Action ◽  
E Coli ◽  
Colony Counting ◽  
Kinetics Of ◽  
Growth And Reproduction

To understand the mechanism of action of the antimicrobial peptide bsn-37 on Escherichia coli (E. coli), we investigated its effects on leakage of ultraviolet-absorbing substances, proteins, and nucleic acids from E. coli CVCC1568. The bacteriostatic kinetics of antimicrobial peptides was determined by colony counting. Our study showed that bsn-37 could effectively inhibit the growth and reproduction of E. coli by disrupting its cell wall and membrane.

scholarly journals Fate of Escherichia coli O157:H7 on Fresh-Cut Apple Tissue and Its Potential for Transmission by Fruit Flies

1999 ◽  
Vol 65 (1) ◽  
pp. 1-5 ◽  
Author(s):  
W. J. Janisiewicz ◽  
W. S. Conway ◽  
M. W. Brown ◽  
G. M. Sapers ◽  
P. Fratamico ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Natural Populations ◽  
Apple Fruit ◽  
Fruit Flies ◽  
Escherichia Coli O157 ◽  
Initial Inoculum ◽  
E Coli ◽  
Time Period ◽  
High Incidence ◽  
Apple Tissue

ABSTRACT Pathogenic Escherichia coli O157:H7, as well as nonpathogenic strains ATCC 11775 and ATCC 23716, grew exponentially in wounds on Golden Delicious apple fruit. The exponential growth occurred over a longer time period on fruit inoculated with a lower concentration of the bacterium than on fruit inoculated with a higher concentration. The bacterium reached the maximum population supported in the wounds regardless of the initial inoculum concentrations. Populations of E. coli O157:H7 in various concentrations of sterilized apple juice and unsterilized cider declined over time and declined more quickly in diluted juice and cider. The decline was greater in the unsterilized cider than in juice, which may have resulted from the interaction of E. coli O157:H7 with natural populations of yeasts that increased with time. Experiments on the transmission of E. coli by fruit flies, collected from a compost pile of decaying apples and peaches, were conducted with strain F-11775, a fluorescent transformant of nonpathogenic E. coli ATCC 11775. Fruit flies were easily contaminated externally and internally with E. coli F-11775 after contact with the bacterium source. The flies transmitted this bacterium to uncontaminated apple wounds, resulting in a high incidence of contaminated wounds. Populations of the bacterium in apple wounds increased significantly during the first 48 h after transmission. Further studies under commercial conditions are necessary to confirm these findings.

scholarly journals Characterization of Enterohemorrhagic Escherichia coli Strains Based on Acid Resistance Phenotypes

2005 ◽  
Vol 73 (8) ◽  
pp. 4993-5003 ◽  
Author(s):  
Arvind A. Bhagwat ◽  
Lynn Chan ◽  
Rachel Han ◽  
Jasmine Tan ◽  
Mahendra Kothary ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Natural Populations ◽  
Acid Resistance ◽  
The United States ◽  
Growth Conditions ◽  
Enterohemorrhagic Escherichia Coli ◽  
Aerobic Growth ◽  
E Coli ◽  
Low Copy Number ◽  
Fermentative Growth

ABSTRACT Acid resistance is perceived to be an important property of enterohemorrhagic Escherichia coli strains, enabling the organisms to survive passage through the acidic environment of the stomach so that they may colonize the mammalian gastrointestinal tract and cause disease. Accordingly, the organism has developed at least three genetically and physiologically distinct acid resistance systems which provide different levels of protection. The glutamate-dependent acid resistance (GDAR) system utilizes extracellular glutamate to protect cells during extreme acid challenges and is believed to provide the highest protection from stomach acidity. In this study, the GDAR system of 82 pathogenic E. coli isolates from 34 countries and 23 states within the United States was examined. Twenty-nine isolates were found to be defective in inducing GDAR under aerobic growth conditions, while five other isolates were defective in GDAR under aerobic, as well as fermentative, growth conditions. We introduced rpoS on a low-copy-number plasmid into 26 isolates and were able to restore GDAR in 20 acid-sensitive isolates under aerobic growth conditions. Four isolates were found to be defective in the newly discovered LuxR-like regulator GadE (formerly YhiE). Defects in other isolates could be due to a mutation(s) in a gene(s) with an as yet undefined role in acid resistance since GadE and/or RpoS could not restore acid resistance. These results show that in addition to mutant alleles of rpoS, mutations in gadE exist in natural populations of pathogenic E. coli. Such mutations most likely alter the infectivity of individual isolates and may play a significant role in determining the infective dose of enterohemorrhagic E. coli.

scholarly journals Differential Spectrum of Mutations That Activate the Escherichia coli bgl Operon in an rpoS Genetic Background

2002 ◽  
Vol 184 (14) ◽  
pp. 4033-4038 ◽  
Author(s):  
Sudha Moorthy ◽  
S. Mahadevan
Keyword(s):  
Escherichia Coli ◽  
Natural Populations ◽  
Structural Elements ◽  
Wild Type ◽  
Genetic Changes ◽  
E Coli ◽  
Activating Mutations ◽  
Major Class ◽  
Insertion Elements ◽  
Dna Insertion

ABSTRACT The bgl promoter is silent in wild-type Escherichia coli under standard laboratory conditions, and as a result, cells exhibit a β-glucoside-negative (Bgl−) phenotype. Silencing is brought about by negative elements that flank the promoter and include DNA structural elements and sequences that interact with the nucleoid-associated protein H-NS. Mutations that confer a Bgl+ phenotype arise spontaneously at a detectable frequency. Transposition of DNA insertion elements within the regulatory locus, bglR, constitutes the major class of activating mutations identified in laboratory cultures. The rpoS-encoded σS, the stationary-phase sigma factor, is involved in both physiological as well as genetic changes that occur in the cell under stationary-state conditions. In an attempt to see if the rpoS status of the cell influences the nature of the mutations that activate the bgl promoter, we analyzed spontaneously arising Bgl+ mutants in rpoS+ and rpoS genetic backgrounds. We show that the spectrum of activating mutations in rpoS cells is different from that in rpoS+ cells. Unlike rpoS+ cells, where insertions in bglR are the predominant activating mutations, mutations in hns make up the majority in rpoS cells. The physiological significance of these differences is discussed in the context of survival of natural populations of E. coli.

scholarly journals The diversity of alleles at the hsd locus in natural populations of Escherichia coli.

Genetics ◽  
1995 ◽  
Vol 140 (4) ◽  
pp. 1187-1197
Author(s):  
V A Barcus ◽  
A J Titheradge ◽  
N E Murray
Keyword(s):  
Escherichia Coli ◽  
Natural Populations ◽  
Enteric Bacteria ◽  
Type I ◽  
Bacterial Strains ◽  
E Coli ◽  
Alternative Families ◽  
Type Ia ◽  
Natural Isolates ◽  
Id Genes

Abstract In enteric bacteria three discrete families of type I restriction and modification systems (IA, IB and ID) are encoded by alleles of the serB-linked hsd locus. Probes specific for each of the three families were used to monitor the distribution of related systems in 37 of the 72 wild-type Escherichia coli strains comprising the ECOR collection. All 25 members of group A in this collection were screened; 12 were probe-positive, nine have hsd genes in the IA family, two in the IB and one in the ID. Twelve strains, representing all groups other than A, were screened; five were probe-positive, one has hsd genes in the IA family, one in the IB and three in the ID. The type ID genes are the first representatives of this family in E. coli, the probe-negative strains could have alternative families of hsd genes. The type IA and IB systems added at least five new specificities to the five already identified in natural isolates of E. coli. The distribution of alleles is inconsistent with the dendrogram of the bacterial strains derived from other criteria. This discrepancy and the dissimilar coding sequences of allelic hsd genes both imply lateral transfer of hsd genes.

scholarly journals Natural populations of Escherichia coli and Salmonella typhimurium harbor the same classes of insertion sequences.

Genetics ◽  
1993 ◽  
Vol 133 (3) ◽  
pp. 449-454 ◽  
Author(s):  
M Bisercić ◽  
H Ochman
Keyword(s):  
Escherichia Coli ◽  
Salmonella Typhimurium ◽  
Natural Populations ◽  
Sequence Divergence ◽  
Insertion Sequences ◽  
Related Factors ◽  
Specific Element ◽  
E Coli ◽  
Close Phylogenetic Relationship ◽  
Polymerase Chain

Abstract Despite their close phylogenetic relationship, Escherichia coli and Salmonella typhimurium were long considered as having distinct classes of transposable elements maintained by either host-related factors or very restricted gene exchange. In this study, genetically diverse collections of E. coli and S. typhimurium (subgroup I) were surveyed for the presence of several classes of insertion sequences by Southern blot analysis and the polymerase chain reaction. A majority of salmonellae contained IS1 or IS3, elements originally recovered from E. coli, while IS200, a Salmonella-specific element, was present in about 20% of the tested strains of E. coli. Based on restriction mapping, the extent of sequence divergence between copies of IS200 from E. coli and S. typhimurium is on the order of that observed in comparisons of chromosomally encoded genes from these taxa. This suggests that copies of IS200 have not been recently transferred between E. coli and S. typhimurium and that the element was present in the common ancestor to both species. IS200 is polymorphic within E. coli but homogeneous among isolates of S. typhimurium, providing evidence that these species might differ in their rates of transfer and turnover of insertion sequences.

scholarly journals Niche and local geography shape the pangenome of wastewater- and livestock-associated Enterobacteriaceae

2020 ◽  
Author(s):  
Liam P. Shaw ◽  
Kevin K. Chau ◽  
James Kavanagh ◽  
Manal AbuOun ◽  
Emma Stubberfield ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Selective Pressure ◽  
Natural Populations ◽  
Insertion Sequences ◽  
E Coli ◽  
The United Kingdom ◽  
Diverse Species ◽  
Complete Genomes ◽  
Show Evidence

Escherichia coli and other Enterobacteriaceae are highly diverse species with ‘open’ pangenomes1,2, where genes move intra- and inter-species via horizontal gene transfer3. These species can cause clinical infections4,5 as well as persist environmentally6,7. Environmental populations have been suggested as important reservoirs of antimicrobial resistance (AMR) genes. However, as most analyses focus on clinical isolates8,9, the pangenome dynamics of natural populations remain understudied, particularly the role of plasmids. Here, we reconstructed near-complete genomes for 828 Enterobacteriaceae, including 553 Escherichia spp. and 275 non-Escherichia species with 2,293 circularised plasmids in total, collected from nineteen locations (livestock farms and wastewater treatment works in the United Kingdom) within a 30km radius at three timepoints over the course of a year. We find different dynamics for the chromosomal and plasmid-borne components of the pangenome, showing that plasmids have a higher burden of both AMR genes and insertion sequences, and AMR plasmids show evidence of being under stronger selective pressure. Focusing on E. coli, we observe that plasmid dynamics are more strongly dominated by niche and local geography, rather than phylogeny or season. Our results highlight the diversity of the AMR reservoir in these species and niches, and the importance of local strategies for controlling the emergence and spread of AMR.

Sites of Adsorption of the Bacteriophages T3 and T5 on the Wall of Escherichia Coli B.

1967 ◽  
Vol 25 ◽  
pp. 96-97
Author(s):  
Manfred E. Bayer
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Electron Microscope ◽  
Uranyl Acetate ◽  
E Coli ◽  
Receptor Sites ◽  
Rigid Cell Wall ◽  
Host Cell Surface ◽  
Bacterial Viruses ◽  
Escherichia Coli B

Bacterial viruses adsorb specifically to receptors on the host cell surface. Although the chemical composition of some of the cell wall receptors for bacteriophages of the T-series has been described and the number of receptor sites has been estimated to be 150 to 300 per E. coli cell, the localization of the sites on the bacterial wall has been unknown.When logarithmically growing cells of E. coli are transferred into a medium containing 20% sucrose, the cells plasmolize: the protoplast shrinks and becomes separated from the somewhat rigid cell wall. When these cells are fixed in 8% Formaldehyde, post-fixed in OsO4/uranyl acetate, embedded in Vestopal W, then cut in an ultramicrotome and observed with the electron microscope, the separation of protoplast and wall becomes clearly visible, (Fig. 1, 2). At a number of locations however, the protoplasmic membrane adheres to the wall even under the considerable pull of the shrinking protoplast. Thus numerous connecting bridges are maintained between protoplast and cell wall. Estimations of the total number of such wall/membrane associations yield a number of about 300 per cell.

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