Lipofection: a highly efficient, lipid-mediated DNA-transfection procedure

A DNA-transfection protocol has been developed that makes use of a synthetic cationic lipid, N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA). Small unilamellar liposomes containing DOTMA interact spontaneously with DNA to form lipid-DNA complexes with 100% entrapment of the DNA, DOTMA facilitates fusion of the complex with the plasma membrane of tissue culture cells, resulting in both uptake and expression of the DNA. The technique is simple, highly reproducible, and effective for both transient and stable expression of transfected DNA. Depending upon the cell line, lipofection is from 5- to greater than 100-fold more effective than either the calcium phosphate or the DEAE-dextran transfection technique.

Two amino acids within the knuckle of the first zinc finger specify DNA response element activation by the glucocorticoid receptor

The specificity of target gene activation by steroid receptors is encoded within a small, cysteine-rich domain that is believed to form two zinc-coordinated fingers. Here we show that the ability of glucocorticoid and estrogen receptors to discriminate between their closely related response elements resides in the two amino acids located between the two cysteines in the C-terminal half of the first finger. Unexpectedly, chimeric glucocorticoid receptors harboring portions of the interfinger and/or second finger of the estrogen receptor have the ability to activate transcription from either a GRE- or ERE-containing promoter. We surmise that whereas the "knuckle" region of the first finger may be the primary determinant of sequence recognition, the remainder of the DNA binding domain normally confers structural information required for preventing promiscuous HRE recognition.

The mouse glucocorticoid receptor: mapping of functional domains by cloning, sequencing and expression of wild-type and mutant receptor proteins

We have isolated mouse glucocorticoid receptor (GR) cDNAs which, when expressed in transfected mammalian cells, produce a fully functional GR protein. Sequence analysis reveals an open reading frame of 2349 bp which could encode a protein of approximately 86,000 daltons. We have also isolated two receptor cDNAs from mouse S49 nuclear transfer-deficient (nt-) cells which encode mutant forms of the receptor protein. One cDNA encodes a protein that is unable to bind hormone and represents the endogenous hormone binding deficient receptor recently discovered in S49 cells. The lesion in this receptor is due to a single amino acid substitution (Glu-546 to Gly). The second cDNA from nt- cells produces a receptor protein that is able to bind hormone but has reduced nuclear binding. This cDNA, therefore, encodes for the S49 nt- receptor which has been shown to have reduced affinity for DNA. The lesion maps to a single amino acid substitution (Arg-484 to His) located in a highly Cys, Lys, Arg-rich region of the protein previously implicated in DNA binding. Our studies provide unambiguous identification of receptor domains and specific amino acids critical for the hormone and DNA binding properties of this transcriptional regulatory protein. Contained within the first 106 amino acids of the mouse GR is a stretch of nine glutamines with two prolines which are related to the family of transcribed repetitive elements, opa, found in Drosophila melanogaster. A truncated receptor lacking these 106 amino acids is functionally indistinguishable from the wild-type receptor.

Domains of the glucocorticoid receptor involved in specific and nonspecific deoxyribonucleic acid binding, hormone activation, and transcriptional enhancement

We have analyzed the domain structure of the mouse glucocorticoid receptor by expression of in vitro mutated receptor in COS-7 cells. The receptor consists of a core domain rich in Cys, Lys, and Arg amino acids which can bind specific DNA sequences (glucocorticoid response elements) and activate transcription. The activity of this centrally located domain is modulated by the activity of the other two domains. The N-terminal domain of the receptor plays a role in decreasing nonspecific DNA binding and may therefore improve the ability of the protein to discriminate between specific and nonspecific DNA binding sites. This activity maps to a small, highly acidic region of the N-terminal domain. The C-terminal domain of the receptor contains the glucocorticoid binding site and in addition represses the transcriptional activity of the receptor in the absence of hormone. Hormone binding relieves the repression allowing transcription activation. The C-terminal domain contains a short sequence conserved among steroid receptors; its deletion yields a receptor that activates transcription in the absence of hormone.

Androgen-specific gene activation via a consensus glucocorticoid response element is determined by interaction with nonreceptor factors

A fundamental issue in steroid hormone regulation is the question of how specific transcription is attained in vivo when several receptors can bind the same DNA sequence in vitro. We report an enhancer of the mouse sex-limited protein (Slp) gene that, unlike previously characterized enhancers, is activated by androgens but not by glucocorticoids or progestins. Potent androgen induction requires both a consensus glucocorticoid (hormone) response element and auxiliary elements also present within a 120-base-pair DNA fragment. Cotransfection assays with wild-type and mutant receptors reveal that glucocorticoid receptor can bind, but not transactivate from, the hormone response element within the enhancer. The positive effect of androgen and the null effect of glucocorticoid appear to require the amino-terminal domains of the respective receptors. Thus, exclusive transcriptional response to androgens, and lack of response to glucocorticoids, derives from factor interactions that are determined by the context of the receptor binding site rather than by its distinct sequence.

The frequency of mutators in populations of Escherichia coli

Owing to occasional spontaneous mutations in genes encoding DNA repair, any population of a reasonable size is expected to harbor a sub-population of genetic mutators. Using a genetically modified strain of Escherichia coli K-12, we have estimated the frequency of mutators to be about 3x10(-5). By and large, this corresponds to a mutation rate from non-mutators to mutators of 5x10(-6) per bacterium per generation. Using a mutS∷Tn10 derivative as representative for mutators, we estimated the increase in mutation rates in mutators to be 19- to 82-fold, depending on the test-mutation under consideration. The load associated with this increase in mutation rate resulted in a growth inhibition of 1%. From these data, we estimated that the rate of detrimental mutations in the non-mutators to be 2x10(-4)-8x10(-4). The situations where adaptive mutations may result in an increase in the frequency of mutators are discussed.

Differential regulation of androgen and glucocorticoid receptors by retinoblastoma protein

The androgen receptor (AR) plays a major role in the development and maintenance of male primary and secondary sexual characteristics. The growth promoting effects of androgens are clearly seen in prostate cancer where treatment by androgen ablation usually leads to tumor regression, followed sometime later, by growth of tumor cells that are resistant to endocrine therapy. We have found that the level of pRB in cells controls AR activity. Overexpression of pRB leads to increased transcriptional activity of the AR. This is similar to the previously reported potentiation of glucocorticoid receptor activity by pRB. In contrast, loss of pRB activity inhibits AR but not glucocorticoid receptor activity. This inhibition correlates with the unique ability of the AR to form a protein-protein complex with pRB in vitro. The site of interaction with pRB lies within the N-terminal domain of the AR and co-localizes with the region of the AR that specifies a requirement for pRB. Thus, the AR has a novel requirement for pRB raising the possibility that the growth promoting activity of AR is due to its direct interaction with pRB. Furthermore, loss of pRB activity during progression of prostate cancer may directly result in a decreased response to androgens.

Susceptibility of Pediococcus spp. to antimicrobial agents

AIM

To investigate the susceptibility of Pediococcus species to antimicrobial agents.

METHODS AND RESULTS

The susceptibility to 14 antimicrobial agents of 31 genotypically distinct strains of six Pediococcus species was assessed by using Etests on ISO-sensitest agar supplemented with horse blood. The species included were Pediococcus acidilactici, Pediococcus damnosus, Pediococcus dextrinicus, Pediococcus inopinatus, Pediococcus parvulus and Pediococcus pentosaceus. For several antimicrobial agents, some species were more susceptible than others. The two industrially important species, P. acidilactici and P. pentosaceus, differed with respect to erythromycin and trovafloxacin susceptibility, and in general both species had higher minimum inhibitory concentrations than the other species. In an erythromycin-resistant P. acidilactici, an erythromycin resistance methylase B [erm(B)] gene was identified by PCR. Using a plasmid preparation from strain P. acidilactici 6990, a previously erythromycin-sensitive Lactococcus lactis strain was made resistant. Transformants harboured a single plasmid, sized at 11.6 kb through sequence analysis. In addition, the erm(B) gene was identified within the plasmid sequence.

CONCLUSIONS

The phenotypic test indicated the absence of acquired antimicrobial resistance genes in 30 of the strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results will help in selection of the best Pediococcus strains for use as starter cultures.

High level expression of wild type and variant mouse glucocorticoid receptors in Chinese hamster ovary cells

We have isolated Chinese hamster ovary (CHO) cell lines expressing elevated levels of wild-type (W) and mutant forms of the glucocorticoid receptor (GR) using the technique of coamplification with a selectable dihydrofolate reductase (dhfr) cDNA. A prominent doublet at 90/92 kilodaltons was observed by Western blotting or labeling with [3H]-dexamethasone mesylate in extracts from cells transfected with W, the hormone binding mutant (NA), and the DNA binding mutant (NB). Quantification of receptor number by [3H]dexamethasone binding revealed the presence of approximately 10(6) receptors per cell in the W and NB-producing lines. This represents a 25- to 50-fold increase in receptor density over control CHO cells which were not transfected with GR. Comparative quantitation by Western blotting of extracts from cells expressing GR showed that cells producing NA contain a level approximately 500-fold over control CHO cells. Function of the amptified receptors was examined by transient transfection with the glucocorticoid-responsive reporter plasmid pMMTV-chloramphenicol acetyl transferase (CAT). Our results indicate that inducible CAT activity increases with the abundance of W receptor and no evidence of saturability was observed even at the highest levels of receptor. This supports previous suggestions that the concentration of the hormone-regulated transcription factor is definitely limiting with regard to maximal transcription efficiency. Interestingly, cells expressing even highly amplified levels of NA-GR or NB-GR showed no inducible response above that seen with control CHO cells. Thus these mutations are exceedingly nonleaky and are not dominant over the low endogenous activity of the CHO GR.(ABSTRACT TRUNCATED AT 250 WORDS)

Olive oil quality classification and measurement of its organoleptic attributes by untargeted GC-MS and multivariate statistical-based approach

The capabilities of dynamic headspace entrainment followed by thermal desorption in combination with gas chromatography (GC) coupled to single quadrupole mass spectrometry (MS) have been tested for the determination of volatile components of olive oil. This technique has shown a great potential for olive oil quality classification by using an untargeted approach. The data processing strategy consisted of three different steps: component detection from GC-MS data using novel data treatment software PARADISe, a multivariate analysis using EZ-Info, and the creation of the statistical models. The great number of compounds determined enabled not only the development of a quality classification method as a complementary tool to the official established method "PANEL TEST" but also a correlation between these compounds and different types of defect. Classification method was finally validated using blind samples. An accuracy of 85% in oil classification was obtained, with 100% of extra virgin samples correctly classified.

Limits of adaptation to a diet low in protein in normal man: urea kinetics

1. Urea kinetics were measured using prime/intermittent oral doses of [15N15N]urea in six healthy men taking diets adequate in energy and containing either 74 or 30 g of protein/day. 2. On 74 g of protein/day, urea production (199 mg of N day-1 kg-1) was 121% of intake, with 60% of the urea produced being excreted in the urine and 40% being salvaged in the colon; 69% of the salvaged nitrogen was retained in the metabolic nitrogen pool. 3. Nitrogen balance was not maintained on 30 g of protein/day. There was a significant decrease in the urea production rate (123 mg of N day-1 kg-1) and 54% of production was excreted in urine, with 46% being salvaged. 4. The pattern of urea production and salvaging on 30 g of protein/day was different to that seen in an earlier study on 35 g of protein/day, with a significant decrease in both production (71%) and salvaging (50%). 5. These data reinforce the conclusions drawn from an earlier study, that the salvaging of urea nitrogen by the colon is an integral part of the process of adaptation to low protein diets. The salvage system appears to fail on an intake of 30 g of protein/day and nitrogen is no longer conserved in sufficient amounts for balance to be maintained. 6. The changes seen in urea kinetics reinforce the conclusion based upon nitrogen balance that the minimum physiological requirement for protein in normal adult man lies between 30 and 35 g of protein/day.

Modeling ventricular contraction with heart rate changes

Recently, a mathematical model of the pumping heart has been proposed describing the heart as a pressure source depending on time, volume and flow. The underlying concept is based on a new two-step paradigm that allows separation between isovolumic (non-ejecting) and ejecting heart properties. The first step describes the ventricular pressure in the isovolumic ventricle. In the following step, the isovolumic description is extended with the ejection effect in order to embrace the pumping heart during actual blood ejection. The description of the isovolumic heart properties plays a crucial role in this paradigm. However, only a single isovolumic model has previously been used restricting the heart rate to 1 Hz. In this paper, a family of models describing the isovolumic contracting ventricle are critically examined. A characterization of what constitutes an optimal model is given and used as a criteria for choosing the optimal model in this family. Moreover, and this is indeed a point, the proposed model in this study is valid for arbitrary heart rates and based on experimental data. The model exhibits all major features of the ejecting heart, including how ventricular pressure and flow vary in time for various heart rates and how stroke volume and cardiac output vary with heart rate. The modeling strategy presented embraces the same steps and demarcations as those suitable for clinical examination whereby new experiments are suggested.

Describing the pumping heart as a pressure source

The pumping heart is described by a new mathematical approach which considers the heart as a pressure source depending on time, volume and flow. This new approach allows a separation between isovolumic (non-ejecting) and ejecting heart properties. The computed results cover most of the features of the human ventricle during normal and altered vascular conditions. It is shown that the time-varying elastance concept is disqualified as an independent description of the heart, it follows from isovolumic heart properties and an ejection effect which consists of positive and negative effects of ventricular blood ejection.

The glucocorticoid receptor gene as a candidate for gene therapy in asthma

Glucocorticoids (GC) are commonly used as anti-inflammatory drugs in asthma, but can produce serious secondary effects and, moreover, be inefficient in corticoresistant asthmatics. After binding to the glucocorticoid receptor (GR), they repress the synthesis of proinflammatory cytokines via inhibition of the transcription factors AP-1 and NF-kappa B. Since qualitative and quantitative defects of the GR have been reported in corticoresistant patients, the transfer of the GR gene in the lung epithelium, the primary site of inflammation in asthma, may restore sensitivity to GC in these patients. As a prerequisite to in vivo studies, we have transfected A549 human lung epithelial cells with a GR expression vector. Using AP-1 and NF-kappa B-dependent reporter gene assays and an immunoassay for the pro-inflammatory cytokine RANTES, we show that the over-expressed GR significantly repressed AP-1 and NF-kappa B activities in the absence of hormone and that the GC dexamethasone produced an additive inhibitory effect. The GC-independent repression of AP-1 and NF-kappa B activities was further demonstrated by overexpressing a ligand-binding deficient GR mutant. Our data suggest that delivery of the GR gene in vivo may reduce inflammation without recourse to GC and may constitute an alternative therapeutic approach for corticoresistant asthma.

Effects of 12-O-tetradecanoylphorbol-13-acetate on estrogen receptor activity in MCF-7 cells

The effects of long term treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) on estrogen receptor (ER) expression in the human breast cancer cell line, MCF-7, were studied. This study demonstrates that treatment of cells with the phorbol ester blocked estrogen receptor activity. Treatment of cells with 100 nM TPA resulted in an 80% decrease in the level of ER protein and a parallel decrease in ER mRNA and binding capacity. Following removal of TPA from the medium, the level of ER protein and mRNA returned to control values; however, the receptor failed to bind estradiol. These cells also failed to induce progesterone receptor in response to estradiol. In addition, TPA treatment blocked transcription from an estrogen response element in transient transfection assays and inhibited ER binding to its response element in a DNA mobility shift assay. The estrogen receptor in treated cells was recognized by two monoclonal anti-ER antibodies and was not quantitatively different from ER in control cells. RNase protection analysis failed to detect any qualitative changes in the ER mRNA transcript. Mixing experiments suggest that TPA induces/activates a factor which interacts with the ER to block binding of estradiol. The effects of TPA on ER levels and binding capacity were concentration-dependent. Low concentrations of TPA inhibited estradiol binding without a decrease in the level of protein, whereas higher concentrations were required to decrease the level of ER protein. The effects of TPA appear to be mediated by activation of protein kinase C since the protein kinase C inhibitors, H-7 and bryostatin, block the effects of TPA on estradiol induction of progesterone receptor. TPA treatment had no effect on the level or binding capacity of the glucocorticoid receptor, indicating that the effects are not universal for steroid receptors. These data demonstrate that activation of the protein kinase C signal transduction pathway modulates the estrogen receptor pathway. The long term effect of protein kinase C activation is to inhibit estrogen receptor function through induction/activation of a factor which interacts with the receptor.

Two point mutations in the hormone-binding domain of the mouse glucocorticoid receptor that dramatically reduce its function

Mouse lymphoma cell line W7M320b, a mutant WEH17 line, requires higher than normal concentrations of glucocorticoid to elicit the hormone responses that are characteristic of this lineage. Complementary DNA clones representing the glucocorticoid receptor (GR) mRNA were derived from the mutant cells, and the sequences coding for the hormone-binding domain were substituted for the analogous wild-type sequences in a GR cDNA expression vector. The function of the resulting GR proteins was tested by transient expression in COS-7 cells along with a glucocorticoid-inducible reporter gene in the presence of varying concentrations of glucocorticoid. From these assays and DNA sequence analyses, two independent functionally significant point mutations in the GR hormone-binding domain were identified. A mutant GR protein containing the single amino acid substitution, Pro547 to Ala, was still functional as a transcriptional activator, but only at hormone concentrations 100 times higher than those required by the wild-type receptor. A second mutant GR protein with a Cys742 to Gly substitution was unstable and almost completely nonfunctional.

Inhibition of histone deacetylation augments dihydrotestosterone induction of androgen receptor levels: an explanation for trichostatin A effects on androgen-induced chromatin remodeling and transcription of the mouse mammary tumor virus promoter

The integrated mouse mammary tumor virus (MMTV) promoter has provided an excellent model system with which to study the impact of steroid hormones on transcriptional activation in the context of a defined chromatin structure. The hormone response element (HRE) of this promoter is positioned on a phased nucleosome which becomes remodeled in response to steroids. One possible mechanism of chromatin remodeling by steroid receptors could involve recruitment of coactivators which alter the histone acetylation status of the HRE nucleosome. To examine how the androgen receptor (AR) influences transcription and chromatin remodeling and to assess whether changes in histone acetylation are involved in these effects, we determined whether the specific histone deacetylase inhibitor trichostatin A (TSA) influenced basal- and androgen-mediated transcriptional activation of the integrated MMTV promoter in the mouse L-cell fibroblast cell line 29+. These cells harbor the MMTV promoter integrated in the genome and express only one steroid hormone receptor subtype, i.e., the AR. Surprisingly, we found that treatment of the cells with TSA alone had virtually no effect on transcription and chromatin remodeling of the MMTV promoter nor on AR levels. However, pretreatment with TSA augmented the DHT effects on all three parameters. These results suggest that histone acetylation changes at the MMTV B nucleosome per se are not alone sufficient to induce chromatin remodeling and subsequent induction of MMTV transcription. Rather, the histone deacetylase inhibitor TSA exerts a portion of its effect on MMTV chromatin remodeling and transcriptional activation indirectly through increases in AR levels.

Use of folic acid casei medium reveals trimethoprim susceptibility of Lactobacillus species

AIM

Lactobacilli have been reported to have intrinsic resistance to trimethoprim. The susceptibility of lactobacilli to trimethoprim on different media was investigated in order to search for a phenotypic test method that could indicate the presence of acquired resistance genes.

METHODS AND RESULTS

Strains of Lactobacillus acidophilus, Lact. paracasei, Lact. rhamnosus and Lact. plantarum were susceptibility tested with E-tests on folic acid casei medium (FACM), MRS and defined medium 1. The effects of addition or removal of nucleosides and thymidine phosphorylase were investigated. E-tests on FACM yielded reproducible minimal inhibitory concentrations (MICs) for trimethoprim but addition of nucleosides was necessary for growth of Lact. acidophilus. MICs for the tested strains were 0.125-0.19, 0.25-3 and 0.064-0.19 microg ml(-1) for Lact. paracasei, Lact. rhamnosus and Lact. plantarum, respectively. With the addition of deoxyuridine and deoxyadenosine to FACM the MICs of Lact. acidophilus were 0.064-1 microg ml(-1).

CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY

Lactobacilli do not have intrinsic resistance to trimethoprim. The results show that trimethoprim susceptibility testing of the tested Lactobacillus species is possible and indicate that transferable resistance genes are absent in all the tested strains.

Comparison of chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter by the androgen and glucocorticoid receptor

We examined the interaction between the androgen (AR) and glucocorticoid receptor (GR) at the transcriptional level using mouse fibroblast cell lines harboring an integrated mouse mammary tumor virus (MMTV) promoter. We found that the AR, after induction with dihydrotestosterone (DHT), caused a progressive increase in MMTV-CAT reporter activity over 72 h which was correlated to an increase in chromatin remodeling of the MMTV promoter in the vicinity of the hormone response element (HRE). In contrast, stimulation of the GR by the synthetic glucocorticoid dexamethasone (Dex) caused a transient increase in MMTV transcriptional activity which returned to basal levels after 72 h. These changes were correlated to a transient increase in chromatin remodeling in the region of the HRE. Neither cotreatment nor pretreatment with Dex affected the DHT response. In fact, there was a more than additive effect of the two hormones on transcription at early time points. This suggests that the inability of GR to remodel chromatin, after 24 h of hormone treatment, is most likely related to changes in the GR itself and not the chromatin remodeling process. Consistent with this, nuclear GR levels dropped by greater than 50% after Dex treatment whereas the AR was induced fourfold after 24 h of DHT treatment. We conclude that a promoter with an ordered chromatin structure can still respond to androgens even after its glucocorticoid responsiveness is lost. This may be one mechanism cells utilize to establish target gene specificity for nuclear receptors that recognize identical DNA sequences.

Down-regulation of glucocorticoid receptors in mouse lymphoma cell variants

The mouse thymoma-derived cell line W7 is sensitive to the cytolytic action of glucocorticoids. We have isolated a novel class of cell variant that apparently overcomes its inherent sensitivity to glucocorticoids by reversibly down-regulating the level of glucocorticoid receptors. This phenotype is stable during subcloning in the presence and in the absence of glucocorticoids and is dominant in somatic cell hybrids with wild-type cells. Fusion of this variant with wild-type cells produces hybrids that down-regulate and are less sensitive to glucocorticoids than hybrids of receptor-negative and wild-type cells. This is the first demonstration of a phenotypic change which correlates with down-regulation of the glucocorticoid receptor.

The Nuclear Receptor Resource: a growing family

Last year, the original Glucocorticoid Receptor Resource was expanded into a comprehensive project: the Nuclear Receptor Resource (NRR, http:// nrr.georgetown.edu/nrr/nrr.html ). The NRR has since been offering comprehensive information on nuclear receptor structure and function, as well as general facts of interest to the scientific community on meetings, funding and employment opportunities. The project now includes individual resources as part of a network which integrates information on glucocorticoid, androgen, mineralocorticoid, thyroid hormone, Vitamin D and peroxisome-proliferator activated receptors. Many investigators have joined the NRR network by filling the Who is who? form available in the NRR home page. This has facilitated communication among scientists in the field and dissemination of data nor otherwise published. Because several investigators have contacted NRR authors over the past few months asking for advice and materials for educational purposes, we have recently decided to include in our project an educational resource on nuclear receptors termed the 'Graphics Library'. The input and suggestions of NRR users do shape the future direction of the project, so we encourage user to give us feedback.

pEOC01: A plasmid from Pediococcus acidilactici which encodes an identical streptomycin resistance (aadE) gene to that found in Campylobacter jejuni

The complete nucleotide sequence of pEOC01, a plasmid (11,661 bp) from Pediococcus acidilactici NCIMB 6990 encoding resistance to clindamycin, erythromycin, and streptomycin was determined. The plasmid, which also replicates in Lactococcus and Lactobacillus species contains 16 putative open reading frames (ORFs), including regions annotated to encode replication, plasmid maintenance and multidrug resistance functions. Based on an analysis the plasmid replicates via a theta replicating mechanism closely related to those of many larger Streptococcus and Enterococcus plasmids. Interestingly, genes homologous to a toxin/antitoxin plasmid maintenance system are present and are highly similar to the omega-epsilon-zeta operon of Streptococcus plasmids. The plasmid contains two putative antibiotic resistance homologs, an ermB gene encoding erythromycin and clindamycin resistance, and a streptomycin resistance gene, aadE. Of particular note is the aadE gene which holds 100% identity to an aadE gene found in Campylobacter jejuni plasmid but which probably originated from a Gram-positive source. This observation is significant in that it provides evidence for recent horizontal transfer of streptomycin resistance from a lactic acid bacterium to a Gram-negative intestinal pathogen and as such infers a role for such plasmids for dissemination of antibiotic resistance genes possibly in the human gut.