Mechanism of broccoli-mediated verticillium wilt reduction in cauliflower.

ABSTRACT Broccoli is resistant to Verticillium dahliae infection and does not express wilt symptoms. Incorporation of broccoli residues reduces soil populations of V. dahliae.

Density of alcohol outlets and teenage drinking: living in an alcogenic environment is associated with higher consumption in a metropolitan setting.

Aim: This study examines the relationship between physical, socio-economic and social environments and alcohol consumption and drunkenness among a general population sample of drinkers aged 12-17 years. DESIGN, SETTING, PARTICIPANTS AND MEASURES: The study was conducted in Auckland, New Zealand. The design comprised two components: (i) environmental measures including alcohol outlet density, locality-based measure of willingness to sell alcohol (derived from purchase surveys of outlets) and a locality-based neighbourhood deprivation measure calculated routinely in New Zealand (known as NZDEP); and (ii) the second component was a random telephone survey to collect individual-level information from respondents aged 12-17 years including ethnicity, frequency of alcohol supplied socially (by parents, friends and others), young person's income; frequency of exposure to alcohol advertising; recall of brands of alcohol and self-reported purchase from alcohol outlets.

Interlaboratory comparison of methods To quantify microsclerotia of verticillium dahliae in soil.

In a comparison of different methods for estimating Verticillium dahliae in soil, 14 soil samples were analyzed in a blinded fashion by 13 research groups in seven countries, using their preferred methods. One group analyzed only four samples. Twelve soil samples were naturally infested, and two had known numbers of microsclerotia of V.

Proteolysis and modulation of the activity of the cell division inhibitor SulA in Escherichia coli lon mutants.

Intracellular accumulation of the inducible cell division inhibitor SulA is modulated by proteases that ensure its degradation, namely, the Lon protease and another ATP-dependent protease(s). Lon- cells are UV sensitive because SulA is stable. We asked whether these ATP-dependent proteases are more active when lon cells are grown at high temperature or in synthetic medium since these conditions decrease the UV sensitivity of lon cells.

Saturation and specificity of the Lon protease of Escherichia coli.

Lon is an ATP-dependent protease of Escherichia coli. The lon mutation has a pleiotropic phenotype: UV sensitivity, mucoidy, deficiency for lysogenization by bacteriophage lambda and P1, and lower efficiency in the degradation of abnormal proteins. All of these phenotypes are correlated with the loss of protease activity.

Mutational analysis of IS10's outside end.

We present the genetic analysis of a large number of mutations in the outside end of insertion sequence IS10. (i) The terminal inverted repeat sequence is probably the primary site of transposase binding. Mutations in this region fall into phenotypic classes which correspond to their map locations, suggesting that this region may consist of several distinct functional segments.

Multiple defects in Escherichia coli mutants lacking HU protein.

The HU protein isolated from Escherichia coli, composed of two partially homologous subunits, alpha and beta, shares some of the properties of eucaryotic histones and is a major constituent of the bacterial nucleoid. We report here the construction of double mutants totally lacking both subunits of HU protein. These mutants exhibited poor growth and a perturbation of cell division, resulting in the formation of anucleate cells.

Isolation of a formamidopyrimidine-DNA glycosylase (fpg) mutant of Escherichia coli K12.

The fpg+ gene of Escherichia coli coding for formamidopyrimidine-DNA glycosylase was previously cloned on a multicopy plasmid. The plasmid copy of the fpg+ gene was inactivated by cloning a kanamycin resistance gene into the open reading frame, yielding the fpg-1::Knr mutation. This mutation was transferred to the chromosome in the following steps: (i) linearization of the plasmid bearing the fpg-1::Knr mutation and transformation of competent bacteria (recB recC sbcB); (ii) selection for chromosomal integration of the fpg-1::Knr mutation; (iii) phage P1 mediated transduction of the fpg-1::Knr mutation in the AB1157 background.

A Tn10-lacZ-kanR-URA3 gene fusion transposon for insertion mutagenesis and fusion analysis of yeast and bacterial genes.

We describe here a new variant of transposon Tn10 especially adapted for transposon analysis of cloned yeast genes; it can equally well be used for analysis of prokaryotic genes. We have applied this element to analysis of the LEU2, RAD50, and CDC48 genes of Saccharomyces cerevisiae. This transposon, nicknamed mini-Tn10-LUK, contains a lacZ gene without efficient transcription or translation start signals, an intact URA3 gene, and a kanR determinant.

A new generalizable test for detection of mutations affecting Tn10 transposition.

We describe here a new rapid screen that allows easy detection of transposon or host mutations that affect Tn10 transposition in Escherichia coli. This test involves a new Tn10 derivative called the "mini-lacZ-kanR fusion hopper" or mini-Tn10-LK for short. This element does not direct expression of beta-galactosidase when present at its original starting location on a suitably engineered plasmid or phage genome because it lacks appropriate transcription and translation start signals.

A genetic analysis of primary products of bacteriophage lambda recombination.

Primary products of bacteriophage lambda recombination that display heterozygosity as a consequence of the presence of regions of heteroduplex DNA are rare in standard lambda crosses. Phage manifesting heterozygosity at a given allele are evident when recombinants, emerging from a cross, are selected for an exchange in a neighboring interval. We show that the abundance of such heterozygotes can be increased 10- to 20-fold by selection on an E.

3-Methyladenine residues in DNA induce the SOS function sfiA in Escherichia coli.

The induction by methylating agents of the SOS function sfiA was measured by means of a sfiA::lac operon fusion in Escherichia coli mutants defective in alkylation repair. The sfiA operon was turned on at a 10-fold lower concentration of methylmethane sulfonate or dimethyl sulfate in tagA strains, lacking specific 3-methyladenine-DNA glycosylase, than in wild-type strains. In contrast, the induction of sfiA by u.

Cell-division control in Escherichia coli: specific induction of the SOS function SfiA protein is sufficient to block septation.

Blocks in DNA replication cause a rapid arrest of cell division in Escherichia coli. We have previously established that the function SfiA (SulA), induced under these conditions as part of the SOS response, is involved in this inhibition of division. To separate the effects of SfiA from those of other SOS functions, we have constructed a plac-sfiA operon fusion, permitting specific induction of SfiA protein by addition of the lac operon inducer isopropyl beta-D-thiogalactopyranoside (IPTG).

Use of DNA hybridization values to construct three-dimensional models of fluorescent pseudomonad relationships.

Three-dimensional models of the relationships among fluorescent pseudomonads were prepared from appropriately transformed percent DNA homology values. The transformation selected was f(x) = ( (1 - HOM/HOM)200, where HOM = fractional DNA homology and 200 is a scaling factor. Model accuracy was quite good as a plot of transformed DNA homology values versus model distances was essentially linear for homology values greater than 30%.

Novel mechanism of cell division inhibition associated with the SOS response in Escherichia coli.

Certain Escherichia coli strains were shown to possess a novel system of cell division inhibition, called the SfiC+ phenotype. SfiC+ filamentation had a number of properties similar to those of sfiA-dependent division inhibition previously described: (i) both are associated with the SOS response induced by expression of the recA(Tif) mutation, (ii) both are associated with cell death, (iii) both are amplified in mutants lacking the Lon protease, and (iv) both are suppressed by sfiB mutations. SfiC+ filamentation and sfiA-dependent division inhibition differed in (i) the physiological conditions under which loss of viability is observed, (ii) the extent of amplification in lon mutants, (iii) their genetic regulation (SfiC+ filamentation is not under direct negative control of the LexA repressor), and (iv) their genetic determinants (SfiC+ filamentation depends on a locus, sfiC+, near 28 min on the E.

Role of the sfiA-dependent cell division regulation system in Escherichia coli.

Several authors have suggested that the SOS-associated (sfiA-dependent) system of division inhibition, normally induced by perturbations of DNA replication, also regulates steady-state (unperturbed) cell division. The present work shows that mean cell mass is identical in sfiA+ and sfiA mutant cultures during steady-state growth, that mass adjustment is identical after shift up, that sfiA expression is not induced by shift up, and that a sfiA mutation does not cause aberrant chromosome segregation.

Effect of suppressors of SOS-mediated filamentation on sfiA operon expression in Escherichia coli.

In Escherichia coli, the cell division block observed during the SOS response requires the product of the sfiA gene, whose expression is regulated negatively by the LexA repressor and positively by the RecA protease. We have studied the effect on sfiA expression of sfiA, sfiB, infA, and infB mutations, which are known to affect SOS-associated filamentation. To measure sfiA expression in the different strains, we first constructed a lambda transducing phage carrying an sfiA::lac operon fusion.

SOS chromotest, a direct assay of induction of an SOS function in Escherichia coli K-12 to measure genotoxicity.

We present and evaluate the SOS chromotest, a bacterial test for detecting DNA-damaging agents. It is a colorimetric assay based on the induction by these agents of the SOS function sfiA, whose level of expression is monitored by means of a sfiA::lacZ operon fusion. The response is rapid (a few hours), and does not require survival of the tester strain.

The SOS chromotest: direct assay of the expression of gene sfiA as a measure of genotoxicity of chemicals.

We used a gene fusion, placing the lacZ gene encoding beta-galactosidase under the control of the sfiA promoter, to construct a new tester strain for genotoxic agents. The assay is performed in a few hours and involves simple enzymatic assays. The dose response curves contain a linear portion which enables to define the SOS Inducing Potency (SOSIP) of compounds.

How Escherichia coli sets different basal levels in SOS operons.

The recA and sfiA genes of Escherichia coli are SOS operons regulated negatively by the LexA repressor. The steady state level of expression of recA is 10-fold higher than that of sfiA, as measured by means of recA::lac and sfiA::lac operon fusions. To study the molecular basis of this difference, we have compared the expression of these two operons in strains in which the concentration of LexA repressor was normal (lexA+), zero (spr amber mutation) or higher than normal (plasmid pJL45, carrying the lexA gene linked to the lac promoter).

DNA replication and indirect induction of the SOS response in Escherichia coli.

The SOS response can be induced indirectly in Escherichia coli by infection with UV irradiated bacteriophage P1, lambda or M13. Induction, monitored quantitatively by means of a sfiA::lac operon fusion, was stronger with the plasmid phage P1 than with lambda, but the kinetics were similar, showing that plasmid and non-plasmid phages are not fundamentally different in their ability to produce indirect induction. In the absence of lambda DNA replication the level of induction was strongly reduced, indicating that the attempt to replicate damaged DNA results in induction of the SOS response.

Role of DNA replication in the induction and turn-off of the SOS response in Escherichia coli.

We have studied the role of DNA replication in turn-on and turn-off of the SOS response in Escherichia coli using a recA::lac fusion to measure levels of recA expression. An active replication fork does not seem to be necessary for mitomycin C induced recA expression: a dnaA43 initiation defective mutant, which does not induce the SOS response at non-permissive temperature, remains mitomycin C inducible after the period of residual DNA synthesis. This induction seems to be dnaC dependent since in a dnaC325 mutant recA expression not only is not induced at 42 degrees C but becomes mitomycin C non-inducible after the period of residual synthesis.

Quantitative evaluation of recA gene expression in Escherichia coli.

A recA::lac operon fusion was constructed using the phage Mu d(Ap, lac) in Escherichia coli to obtain precise measurements of the level of recA gene expression in various genetic backgrounds. The RecA protein normally represents 0.02% of total protein.