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L Daneo-Moore

Publications and source records attributed to L Daneo-Moore.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effect of cell cycle stages on the central density of Enterococcus faecium ATCC 9790.

Cultures of Enterococcus faecium growing at various rates were examined for timing of cell division cycle events by using the method of residual divisions and a morphological analysis. Both methods gave essentially the same timing for the onset of D1 (completion of chromosome replication) and of D2 (completion of septation). Frequencies of cells exhibiting a phase-reversed center in bovine serum albumin at various growth rates were determined. The data fit a model in which rapidly growing cells increase in refractive index (which is assumed to represent central density) at completion of the chromosome replication cycle involved in the ongoing division, whereas slowly growing cultures increase in central density at the time of completion of septation. There was no correlation between the timing of increase in central density and the timing of initiation of new sites of surface growth.

Cell Cycle↗
PubMed1989

The second peptidoglycan hydrolase of Streptococcus faecium ATCC 9790 covalently binds penicillin.

A second peptidoglycan hydrolase (muramidase-2) of Streptococcus faecium ATCC 9790 (Enterococcus hirae) has been purified to apparent homogeneity. The enzyme has been shown to be a beta-1,4-N-acetylmuramoylhydrolase (muramidase; EC 3.2.1.17) and to differ in substrate specificity from a previously isolated muramidase. Purified enzyme appears as two protein staining bands with molecular masses of 125 and 75 kilodaltons (kDa) on polyacrylamide gels after sodium dodecyl sulfate electrophoresis. Elution and renaturation of protein bands from sodium dodecyl sulfate-polyacrylamide gels showed that both proteins have muramidase-2 activity. Both proteins have been shown to bind radioactive benzylpenicillin and have the same electrophoretic mobilities as penicillin-binding proteins 1 and 5 present in membrane preparations of this organism, respectively. Incubation of a [14C]penicillin G-labeled 125-kDa form of the enzyme with crude alkaline extracts from S. faecium (which did not contain added proteinase inhibitors) showed the endogenous conversion of the radiolabeled 125-kDa form to the radiolabeled 75-kDa form of the enzyme.

Chromatography, Affinity↗
PubMed1988

Transformation of Streptococcus sanguis to intrinsic penicillin resistance.

A series of step-level penicillin-resistant derivatives of Streptococcus sanguis V288 (Challis) were obtained through successive genetic transformations. The DNA donor used was a laboratory-derived, penicillin-resistant multistep mutant of the recipient strain. Detection of the penicillin-binding proteins (PBPs) of wild-type and transformants revealed five major PBPs. While it was found that S. sanguis can acquire intrinsic resistance in a stepwise manner and the mechanism was similar to those of some other organisms (changes in penicillin-binding protein affinity and/or in extent of penicillin binding), multiple-PBP changes accompanied a single step-level of resistance. All of the PBPs showed varying degrees of decreased affinity for [3H]benzylpenicillin with increasing penicillin resistance. Of these, the consistent, dramatic and progressive decrease of PBP 4 binding was most notable. After an initial decrease at the first step-level of resistance, PBP 5 was restored to wild-type levels, indicating a possible important role in survival. Genetic linkage of the first two step-levels of resistance was demonstrated by examination of transformation frequencies and by hit-kinetics experiments. A convenient method is described for the quantitative comparison of fluorographs containing PBPs with a wide range of affinities for penicillin.

Bacterial Proteins↗
PubMed1988

Tn916 insertional inactivation of multiple genes on the chromosome of Streptococcus mutans GS-5.

Streptococcus mutans GS-5 was transformed with the Escherichia coli plasmid pAM150 containing the cloned streptococcal transposon Tn916. Southern blot analyses with the tetracycline-resistant determinant of Tn916 showed that Tn916 was inserted into the chromosome of S. mutans at a variety of different sites. Tn916 insertions resulted in the inactivation of genes that code for various steps in the biosynthesis of several different amino acids. Two auxotrophs which contained a single copy of Tn916 were shown to revert to prototrophy at frequencies of about 10(-8). All of the revertant prototrophs were susceptible to tetracycline, indicating regeneration of the functional gene by excision of Tn916.

DNA Transposable Elements↗
PubMed1987

Penicillin tolerance in Streptococcus faecium ATCC 9790.

Tolerant strains of Streptococcus faecium had higher levels of muramidase 2 and lower levels of trypsinactivable muramidase 1 than did susceptible strains. Susceptible strains lysed faster than did tolerant strains in buffer and at some antibiotic concentrations. The addition of Triton X-100 produced equal lysis rates for susceptible and tolerant cultures.

Bacteriolysis↗
PubMed1986

Inhibition of beta-lactam antibiotics at two different times in the cell cycle of Streptococcus faecium ATCC 9790.

Treatment of Streptococcus faecium ATCC 9790 with sublytic concentrations of beta-lactam antibiotics revealed two different division blocks in the cell division cycle. One block, induced by N-formimidoyl thienamycin and methicillin, occurred before the completion of chromosome replication, whereas the other, induced by cefoxitin and cephalothin, took place later in the cycle. In addition, these antibiotics gave rise to distinct morphological forms; the antibiotics acting at the earlier block point produced mainly "dumbbells," whereas those affecting the later time formed "lemons." When used in combination N-formimidoyl thienamycin and cefoxitin exerted synergistic killing on this strain. These data suggest that beta-lactam antibiotics have at least two sites of action in S. faecium.

Anti-Bacterial Agents↗
PubMed1986

Relationship of shape to initiation of new sites of envelope growth in Streptococcus faecium cells treated with beta-lactam antibiotics.

Exponential-phase cells of Streptococcus faecium were treated with concentrations of ampicillin and cephalothin which, over 60 min, had little effect on increase in culture mass but resulted in about a 65% inhibition of increase in cell numbers. The resulting drug-treated cells underwent about a doubling in cell mass and volume above that of the untreated cells. The newly divided cells produced in the presence of drugs were shown to be due to the division of central or primary sites of envelope growth present at the time of treatment. Sites that were newly initiated (secondary sites) at the time of treatment or sites initiated after treatment did not divide but enlarged in length and girth to give abnormally large cells. Although the increase in average total volume was the same after each interval of treatment with ampicillin and cephalothin, the primary growth sites of the cephalothin-treated cells grew somewhat more slowly, and their secondary sites grew somewhat more quickly, than did those of the ampicillin-treated cells. Cephalothin-treated cells initiated secondary sites at a rate similar to that of the untreated cells, whereas the ampicillin-treated cells exhibited reduced rates of secondary site initiation. Two models are presented that account for these results.

Ampicillin↗
PubMed1986

Autoradiographic studies of the synthesis of RNA and protein as a function of cell volume in Streptococcus faecium.

Mid-exponential-phase cultures were either labeled continuously with tritiated leucine and uracil or pulse-labeled with tritiated leucine. The amount of leucine and uracil incorporated into protein or RNA per cell was determined by grain counts of autoradiographs of cells seen in electron micrographs; the volume of each cell was determined by three-dimensional reconstruction. The average number of autoradiographic grains around cells continuously labeled with uracil and leucine increased linearly with cell volume. In contrast, while the average grain count around cells pulse-labeled with leucine increased in a near-linear fashion over most of the volume classes, less than the expected number of grains were seen around cells in large- and small-size classes. The distribution of grains around cells from both the continuously and pulse-labeled populations could be fit at the 5% confidence level with a Poisson distribution modified to take into consideration the volume distribution of each population of cells analyzed. These findings suggested that large changes in the density of RNA and protein do not occur in most cells as they increase in size; however, there may be decreases in the rate of protein synthesis in some large and small cells. The decrease in the rate of protein synthesis appears consistent with the hypothesis that new sites of envelope growth must be introduced into cells that are close to the division event to restore rapid growth.

Autoradiography↗
PubMed1986

Autoradiographic studies of chromosome replication during the cell cycle of Streptococcus faecium.

Analysis of the distribution of autoradiographic grains around cells of Streptococcus faecium which had been either continuously or pulse-labeled with tritiated thymidine (mass doubling time, 90 min) showed a non-Poisson distribution even when the distribution of cell sizes in the populations studied was taken into account. These non-Poisson distributions of grains were assumed to reflect the discontinuous nature of chromosome replication. To study this discontinuous process further, we fitted an equation to the grain distribution observed for the pulse-labeled cells that assumed that in any population of cells there were subpopulations in which there were zero, one, or two replicating chromosomes. This analysis predicted an average time for chromosome replication and for the period between completion of rounds of chromosome replication and division of 55 and 43 min, respectively, which were in excellent agreement with estimates made by other techniques. The present investigation extended past studies in indicating that the initiation and completion of rounds of chromosome replication are poorly phased with increases in cell volume and that the amount of chromosome replication may be different in different cell halves.

Autoradiography↗
PubMed1985

Recombination-deficient Streptococcus sanguis.

A UV-sensitive derivative was obtained from Streptococcus sanguis Challis. The organism could be transformed with a number of small streptococcal plasmids at frequencies equal to, or 1 logarithm below, the transformation frequencies for the parent organism. However, transformation with chromosomal DNA was greatly impaired in the UV-sensitive derivative.

Methyl Methanesulfonate↗
PubMed1984

Detergent-resistant Streptococcus faecium derivatives that display conditional penicillin lysis.

Three spontaneous derivatives of Streptococcus faecium ATCC 9790, originally isolated as conditionally Triton X-100 detergent-resistant at 25 degrees C, displayed normal penicillin-induced rates of lysis at 37 degrees C but substantially reduced rates of lysis and killing at 25 degrees C. The addition of exogenous unsaturated fatty acids at 25 degrees C restored wild-type penicillin lysis rates.

Detergents↗
PubMed1984

Division of temperature-sensitive Streptococcus faecium mutants after return to the permissive temperature.

The regrowth of 27 temperature-sensitive division mutants of Streptococcus faecium ATCC 9790 was examined after various periods of incubation at the nonpermissive temperature. Several of the mutants blocked at various stages of septum formation or of daughter-cell separation divided in a partially or completely synchronous way after a short incubation at the nonpermissive temperature. All four lytic mutants blocked early in the cell division cycle divided at a normal rate after a brief lag.

Cell Division↗
PubMed1984

Analysis of initiation of sites of cell wall growth in Streptococcus faecium during a nutritional shift.

Three-dimensional reconstruction methods were applied to electron micrographs of Streptococcus faecium to study the initiation of cell wall growth sites during a nutritional shift experiment. Upon lowering the mass doubling time from 76 to 33 min by the addition of excess glutamate, the formation of new cell wall growth sites accelerated above the old steady-state rate at about the same time (10 to 15 min) as did mass, RNA, protein, cell numbers, and autolytic capacity but considerably before DNA (30 min) and peptidoglycan (20 min) synthesis did. During the shift, the average range of cell volumes over which new wall growth sites were introduced did not change significantly. However, upon the shift there was an increase in the frequency of cells having new sites, which was due to the faster-growing cells initiating more new sites in peripheral locations before division. After a transition period, the number of new sites per milliliter of culture increased at a rate that paralleled that of the culture mass. These findings support a model in which new sites are introduced when cells grow to a relatively constant, growth rate-independent size, while the rate at which sites form and grow increases with the growth rate. In this model, chromosome synthesis does not regulate the formation of new sites of cell wall growth, but existing sites cannot be completed until rounds of chromosome synthesis are completed.

Bacterial Proteins↗
PubMed1983

Effects of culture density on the kinetics of germ tube formation in Candida albicans.

The relationship between culture density or phase of growth at 24.5 degrees C and the ability of Candida albicans to form germ tubes when shifted to 37 degrees C was investigated. Evidence is presented demonstrating germ tube production from liquid synthetic medium cultures at all phases of growth. Previous studies reported that only cells from stationary phase cultures were competent to form germ tubes. Comparisons between exponential and stationary phase cultures indicate more rapid and more synchronous germ tube production from cells growing in the exponential phase.

Candida albicans↗
PubMed1983

Differential protein synthesis in Candida albicans during blastospore formation at 24.5 degrees C and during germ tube formation at 37 degrees C.

To identify proteins synthesized during blastospore to germ tube transformation in Candida albicans, membrane and cytoplasmic protein fractions labelled with 14C were analysed by SDS-PAGE and autoradiography. Four cytoplasmic proteins were detected in pulse-labelled lysates prepared from cells forming blastospores and germ tubes at 37 degrees C, but not in pulse-labelled lysates prepared from cells forming blastospores at 24.5 degrees C. Three proteins detectable in 24.5 degrees C lysates were diminished in 37 degrees C lysates.

Autoradiography↗
PubMed1983

Effects of cell wall inhibitors on cell division in Streptococcus mutans.

The addition of inhibitors of cell wall biosynthesis to exponential-phase cultures of Streptococcus mutans may do one of three things, depending on the concentrations used: (i) prevent cell division at a time coincident with the onset of chromosome replication, (ii) prevent cell division later in the cell cycle coincident with or near completion of septation, or (iii) lead to limited cell lysis. The relative tolerance of S. mutans to inhibitors of cell wall biosynthesis may be due to the fact that S. mutans cultures treated with low levels of cell wall antibiotics seem to be blocked at a stage before initiation of autolytic activity, whereas cultures treated with high levels of these antibiotics seem to be blocked after termination of the autolytic phase. Thus, the cells escape the lytic death that is seen in other streptococci exposed to inhibitors of cell wall biosynthesis.

Anti-Bacterial Agents↗
PubMed1983

Initiation of wall assembly sites in Streptococcus faecium.

In electron micrographs of replicas of Streptococcus faecium, sites of wall growth are located between pairs of raised equatorial bands. Analysis of cells taken from cultures with mass doubling times between 30 and 125 min indicates that rounds of wall synthesis are initiated at a time close to division, which is temporally unrelated to the initiation or termination of chromosome replication. Growth sites are initiated at a relatively constant volume independent of growth rate when the volume contained within the two segments of wall adjoining an equatorial band marker approaches ca. 0.26 micrometer 3.

Cell Division↗