Modulation of GT-1 DNA-binding activity by calcium-dependent phosphorylation

The analysis of pea rbcS-3A promoter sequence showed that BoxII was necessary for the control of rbcS-3A gene expression by light. GT-1, a DNA-binding protein that interacts with BoxII in vitro, is a good candidate for being a light-modulated molecular switch controlling gene expression. However, the relationship between GT-1 activity and light-responsive gene activation still remains hypothetical. Because no marked de novo synthesis was detected after light treatment, light may induce post-translational modifications of GT-1 such as phosphorylation or dephosphorylation. Here, we show that recombinant GT-1 (hGT-1) of Arabidopsis can be phosphorylated by various mammalian kinase activities in vitro. Whereas phosphorylation by casein kinase II had no apparent effect on hGT-1 DNA binding, phosphorylation by calcium/calmodulin kinase II (CaMKII) increased the binding activity 10-20-fold. Mass spectrometry analyses of the phosphorylated hGT-1 showed that amongst the 6 potential phosphorylatable residues (T86, T133, S175, T179, S198 and T278), only T133 and S198 are heavily modified. Analyses of mutants altered at T86, T133, S175, T179, S198 and T278 demonstrated that phosphorylation of T133 can account for most of the stimulation of DNA-binding activity by CaMKII, indicating that this residue plays an important role in hGT-1/BoxII interaction. We further showed that nuclear GT-1 DNA-binding activity to BoxII was reduced by treatment with calf intestine phosphatase in extracts prepared from light-grown plants but not from etiolated plants. Taken together, our results suggest that GT-1 may act as a molecular switch modulated by calcium-dependent phosphorylation and dephosphorylation in response to light signals.

A novel glycine-rich protein is associated with starch grain accumulation during anther development

LIM14, originally identified as a lily gene associated with microsporogenesis, encodes a protein which has two distinct domains, one with glycine-serine repeats and the other with a hydrophobic signal peptide at the N-terminus. The putative LIM14 protein, however, is distinct from the glycine-rich cell wall proteins which have been described before. RNA analyses indicated that the LIM14 transcript is specifically detected in the anther from zygotene to young pollen stage. By using antibodies raised against recombinant LIM14 protein, we detected anther-specific 15 kDa protein. Immunofluorescence microscopy demonstrated that the LIM14 protein is associated with starch grains in the anther wall cells just prior to microspore mitosis and then accumulates at a higher level with the starch grains of immature pollen. We tagged LIM14 with the GUS and GFP reporter genes and introduced them into tobacco BY-2 cells. Analysis of the transformed cells revealed that the chimeric proteins are functional and specifically targeted to plastids. These results indicate that LIM14 is an anther-specific protein that may play a role in starch accumulation and amyloplast differentiation during anther development and pollen formation.

Bactericidal effect of electrolyzed neutral water on bacteria isolated from infected root canals

OBJECTIVE

The purposes of this study were to examine the time-related changes in pH, oxidation-reduction potential, and concentration of chlorine of electrolyzed neutral water and to evaluate the bactericidal effect of electrolyzed neutral water against bacteria from infected root canals.

STUDY DESIGN

Various properties of electrolyzed neutral water--pH value, oxidation-reduction potential, and concentration of chlorine--were measured at different times after storage of the water in the open state, the closed state, or the closed-and-dark state. The bactericidal effect of the various electrolyzed neutral water samples was then tested against 17 strains of bacteria, including 15 strains isolated from infected canals, as well as against 1 strain of fungus. Each bacterial or fungal suspension was mixed with electrolyzed neutral water, and the 2 substances were reacted together for 1 minute. After incubation for 1 to 7 days, the bactericidal effect of the electrolyzed neutral water was determined.

RESULTS

The pH value and oxidation-reduction potential of electrolyzed neutral water remained almost unchanged when the water was stored in a dark, closed container. However, the concentration of chlorine decreased from 18.4 ppm to 10.6 ppm. Electrolyzed neutral water showed a bactericidal or growth-inhibitory effect against the bacteria.

CONCLUSIONS

The results indicate that electrolyzed neutral water maintains a constant pH and oxidation-reduction potential when kept in a closed container without light and that it exhibits a bacteriostatic/bactericidal action against isolates obtained from infected root canals.

Regulation of sucrose-6-phosphate hydrolase activity in Streptococcus mutans: characterization of the scrR gene

Previous results have implicated an important role for the enzyme IIScr, the sucrose-specific permease, in the transport of sucrose by cariogenic Streptococcus mutans. The product of the scrB gene, sucrose-6-phosphate hydrolase (Suc-6PH), is required for the metabolism of phosphorylated sucrose. The results from the utilization of scrB::lacZ fusions in S. mutans GS-5 have suggested that sucrose-grown cells have higher levels of scrB gene expression than do cells grown with glucose or fructose. Northern blot analysis of scrB transcripts has also confirmed the relative strengths of expression as sucrose>glucose>fructose. Immediately downstream from the scrB gene, an open reading frame with homology to regulatory proteins of the GalR-LacI family as well as to ScrR proteins from several other bacteria has been identified. In addition, this gene appears to be transcribed in the same operon as scrB. Inactivation of this gene, scrR, did not alter the relative expression of the scrB gene in the presence of sucrose or fructose but did increase SUC-6PH levels in the presence of glucose to that observed with sucrose. Furthermore, the S. mutans ScrR homolog appears to bind to the scrB promoter region as determined from the results of gel shift assays. These results suggest that the scrR gene is involved in the regulation of scrB, and likely scrA, expression. However, it is not clear whether sucrose acts as an inducer of expression of these genes or, alternatively, whether glucose and fructose act as repressors.

Cloning and sequence analysis of two copies of a 23S rRNA gene from Helicobacter pylori and association of clarithromycin resistance with 23S rRNA mutations

In this study, two identical copies of a 23S-5S gene cluster, which are separately situated within the Helicobacter pylori UA802 chromosome, were cloned and sequenced. Comparison of the DNA sequence of the H. pylori 23S rRNA gene with known sequences of other bacterial 23S rRNA genes indicated that the H. pylori UA802 23S rRNA genes are closely related to those of Campylobacter spp. and therefore belong in the proposed Proteobacteria subdivision. The 5'-terminal nucleotide T or A of the 23S rRNA is close to a Pribnow box which could be a -10 region of the transcription promoter for the 23S rRNA gene, suggesting that a posttranscriptional process is likely not involved in the maturation of the H. pylori 23S rRNA. Clinical isolates of H. pylori resistant to clarithromycin were examined by using natural transformation and pulsed-field gel electrophoresis. Cross-resistance to clarithromycin and erythromycin, which was transferred by natural transformation from the Cla(r) Ery(r) donor strain H. pylori E to the Cla(s) Ery(s) recipient strain H. pylori UA802, was associated with an single A-to-G transition mutation at position 2142 of both copies of the 23S rRNA in UA802 Cla(r) Ery(r) mutants. The transformation frequency for Cla(r) and Ery(r) was found to be approximately 2 x 10(-6) transformants per viable cell, and the MICs of both clarithromycin and erythromycin for the Cla(r) Ery(r) mutants were equal to those for the donor isolate. Our results confirmed the previous findings that mutations at positions 2142 and 2143 of the H. pylori 23S rRNA gene are responsible for clarithromycin resistance and suggest that acquisition of clarithromycin resistance in H. pylori could also result from horizontal transfer.

Specific detection and confirmation of Campylobacter jejuni by DNA hybridization and PCR

Conventional detection and confirmation methods for Campylobacter jejuni are lengthy and tedious. A rapid hybridization protocol in which a 1,475-bp chromogen-labelled DNA probe (pDT1720) and Campylobacter strains filtered and grown on 0.22-micron-pore-size hydrophobic grid membrane filters (HGMFs) are used was developed. Among the environmental and clinical isolates of C. jejuni, Campylobacter coli, Campylobacter jejuni subsp. doylei, Campylobacter lari, and Arcobacter nitrofigilis and a panel of 310 unrelated bacterial strains tested, only C. jejuni and C. jejuni subsp. doylei isolates hybridized with the probe under stringent conditions. The specificity of the probe was confirmed when the protocol was applied to spiked skim milk and chicken rinse samples. Based on the nucleotide sequence of pDT1720, a pair of oligonucleotide primers was designed for PCR amplification of DNA from Campylobacter spp. and other food pathogens grown overnight in selective Mueller-Hinton broth with cefoperazone and growth supplements. All C. jejuni strains tested, including DNase-producing strains and C. jejuni subsp. doylei, produced a specific 402-bp amplicon, as confirmed by restriction and Southern blot analysis. The detection range of the assay was as low as 3 CFU per PCR to as high as 10(5) CFU per PCR for pure cultures. Overnight enrichment of chicken rinse samples spiked initially with as little as approximately 10 CFU/ml produced amplicons after the PCR. No amplicon was detected with any of the other bacterial strains tested or from the chicken background microflora. Since C. jejuni is responsible for 99% of Campylobacter contamination in poultry, PCR and HGMF hybridization were performed on naturally contaminated chicken rinse samples, and the results were compared with the results of conventional cultural isolation on Preston agar. All samples confirmed to be culture positive for C. jejuni were also identified by DNA hybridization and PCR amplification, thus confirming that these DNA-based technologies are suitable alternatives to time-consuming conventional detection methods. DNA hybridization, besides being sensitive, also has the potential to be used in direct enumeration of C. jejuni organisms in chicken samples.

Phytochrome-regulated repression of gene expression requires calcium and cGMP

The plant photoreceptor phytochrome A utilizes three signal transduction pathways, dependent upon calcium and/or cGMP, to activate genes in the light. In this report, we have studied the phytochrome A regulation of a gene that is down-regulated by light, asparagine synthetase (AS1). We show that AS1 is expressed in the dark and repressed in the light. Repression of AS1 in the light is likely controlled by the same calcium/cGMP-dependent pathway that is used to activate other light responses. The use of the same signal transduction pathway for both activating and repressing different responses provides an interesting mechanism for phytochrome action. Using complementary loss- and gain-of-function experiments we have identified a 17 bp cis-element within the AS1 promoter that is both necessary and sufficient for this regulation. This sequence is likely to be the target for a highly conserved phytochrome-generated repressor whose activity is regulated by both calcium and cGMP.

Inhibition of a Porphyromonas gingivalis colonizing factor between Actinomyces viscosus ATCC 19246 by monoclonal antibodies against recombinant 40-kDa outer-membrane protein

1. Porphyromonas gingivalis, an important pathogen in human periodontal disease, aggregates with Actinomyces viscosus ATCC 19246. 2. Monoclonal antibodies (mAbs) against purified recombinant 40-kDa outer-membrane protein (r40-kDa, OMP) of P. gingivalis 381 inhibited its coaggregation with A. viscosus ATCC 19246 in a dose-dependent manner. 3. Five mAb clones against r40-kDa OMP were selected. The isotype of the five was IgG1. 4. Pg-ompA2 inhibited the coaggregation of several strains of P. gingivalis with A. viscosus ATCC 19246 cells.

Light regulated transcription in higher plants

Studies on the function of plant promoters have demonstrated the presence of regulatorycis-acting elements that mediate developmental or environmental signals. Analysis of many light-responsive genes showed thatcis-acting elements responsible for light regulated transcription are located within the 5' upstream region. Numerous light responsivecis-acting elements andtrans-acting factors have been identified and characterized. The present article reviews the recent advances in studies of light regulated transcriptional regulation and signal transduction.

Calcium and cGMP target distinct phytochrome-responsive elements

Previous work using microinjection into single cells of the tomato aurea mutant demonstrated that phytochrome A-dependent activation of rbcS and chs genes was mediated by calcium and cGMP, respectively. This work sought to identify promoter cis-elements that respond to these two small molecules. Box II and Unit I, derived from rbcS-3A and chs promoters, respectively, were previously shown to function as light-responsive cis-elements. Eleven copies of Box II and four copies of Unit I were linked 5' to the -90 and -46 35 S promoters, respectively, and, both constructs were fused to the beta-glucuronidase (GUS) reporter gene. GUS activities were obtained upon coinjection of either Box II/-90GUS or Unit I/-46GUS with oat phytochrome A (phyA) and GTP gamma S, an activator of heterotrimeric G proteins. The activation of Box II/-90GUS by phyA was insensitive to the cGMP antagonist, Rp-cGMPS, although anthocyanin accumulation, but not chloroplast development, was totally blocked in the injected cells. Consistent with this result, calcium, but not cGMP, induced Box II/-90GUS activity. In contrast to Box II/-90GUS, phyA-dependent activation of Unit I/-46GUS activity was blocked by Rp-cGMPS. Moreover, cGMP, not calcium, induced Unit I/-46GUS activity. Control experiments showed that -90 GUS and -46 GUS were inactive in the presence of calcium and cGMP, respectively. These results provide evidence that Box II and Unit I are targets of the calcium and cGMP pathways, respectively. Interestingly, calcium activation of Box II/-90GUS was repressed by a high concentration of cGMP and cGMP induction of Unit I/-46GUS was blocked by a high concentration of calcium/CaM. Thus, these two small cis-elements can also serve as targets of the reciprocal control mechanisms that operate to regulate the activities of the two phyA signaling branches.

Simple in situ hypothermia reduced ischaemic injury to human liver during hepatectomy

OBJECTIVE

To assess the preventive effect of simple in situ cooling on ischaemic injury in human livers.

DESIGN

Randomised study.

SETTING

University department of surgery, Japan.

SUBJECTS

20 patients who were to undergo liver resection (right lobectomy, n = 6, left lobectomy, n = 3, and posterior segmentectomy, n = 1, in each group); all but 2 who had normal remnant livers and were randomised to undergo either warm ischaemia or in situ cooling (n = 10 in each group).

INTERVENTIONS

Hypothermia was induced by rapid infusion of roughly 450 ml of cold Ringer's lactate into the portal vein during occlusion of the portal triad before resection.

MAIN OUTCOME MEASURES

Occlusion time, ATP concentrations, biochemical indicators of liver damage, and coagulation profile.

RESULTS

The mean (SD) occlusion time was 55 (6) minutes for the warm ischaemia group and 53 (3) for the in situ cooling group. After in situ cooling the state of the liver as indicated by serum alanine aminotransferase activity (ALT) and prothrombin time had improved substantially. Mean (SD) ALT activity was 516 (168) U/I in the warm ischaemia group compared with 305 (154) in the in situ cooling group (p < 0.02) on the first postoperative day. The respective figures for prothrombin time (%) were 56 (23) compared with 77 (14), (p < 0.05).

CONCLUSION

In situ cooling lessened the amount of ischaemic damage done to the liver during hepatectomy compared with treatment with warm ischaemia.

Complement-mediated killing of porphyromonas gingivalis 381 by the immunoglobulin G induced by recombinant 40-kDa outer membrane protein

Porphyromonas gingivalis has been implicated as an important pathogen in severe adult periodontitis. We have previously cloned a 40-kDa outer membrane protein from P. gingivalis 381 and succeeded in producing sufficient quantities of the recombinant protein (r40-kDa OMP). r40-kDa OMP has been the subject of considerable interest to us as a possible vaccine candidate. To understand the role of anti-r40-kDa OMP antibody in the host defense mechanisms against P. gingivalis, we examined the involvement of a rabbit antibody against r40-kDa OMP (r40-kDa OMP Ab) to an in vitro complement-mediated bactericidal assay for P. gingivalis 381. By measuring the absorbance values in order to assay the surviving bacteria, we found significant anti-P. gingivalis activity of r40-kDa OMP Ab when guinea pig complement was present. Using affinity-purified immunoglobulin G of r40-kDa OMP Ab (IgG-r40-kDa OMP), we demonstrated that the IgG contributed to anti-P. gingivalis activity in the antibody-complement system. This was effected by measuring the incorporation of tritiated thymidine into newly synthesized nucleic acids. Finally, we confirmed the cell lysis of P. gingivalis 381 exposed to IgG-r40-kDa OMP in the presence of complement sources in a radioactive bactericidal assay using bacteria labeled with [14C]sodium acetate. Assembling the data from experiments using component-deficient complements, we concluded that IgG-r40-kDa OMP was related to the killing of P. gingivalis 381 by mediation in the complement activated through both the classical and the alternative pathways.

Detection of Actinomyces species using nonradioactive riboprobes coupled with polymerase chain reaction

We have been focusing our attention on the detection and identification of oral bacteria which are frequently associated with periodontal disease. In previous studies, Actinomyces species-specific riboprobes were generated and used to identify this microorganism. However, problems lie in the low sensitivity of this method. We have developed a novel system for the detection of Actinomyces species using nonradioactive riboprobes coupled with polymerase chain reaction (PCR) in this study. This system employs two procedures; initially, DNA fragments specific for the target microorganism are amplified by PCR, and these specific fragments are further hybridized with nonradioactive riboprobes. PCR analysis using chromosomal DNA isolated from Actinomyces species including laboratory strains, clinical isolates, and Actinomyces naeslundii (ATCC 12104) indicated the presence of the predicted common 756-bp fragment, a portion of the sialidase gene. These amplified DNA fragments were effectively visualized by hybridization with the digoxigenin-labeled riboprobes corresponding to the internal region of the amplified sialidase gene. With this system, approximately three orders of magnitude less chromosomal DNA was sufficient for the detection of specific microorganisms compared to the conventional riboprobe systems.

Variability of gene order in different Helicobacter pylori strains contributes to genome diversity

Considerable genomic microdiversity has been reported previously among Helicobacter pylori isolates. We have constructed genome maps of four unrelated H. pylori strains (NCTC11637, NCTC11639, UA802 and UA861) using pulsed-field gel electrophoresis (PFGE) with NotI and NruI, hybridization with extracted PFGE DNA fragments and probing with 17 gene probes. These strains of H. pylori were compared with a fifth unrelated H. pylori strain NCTC11638 mapped previously. Considerable diversity in gene arrangement was evident among the five H. pylori maps, and no consistent gene clustering was found. The association of only four genes, katA (catalase gene), vacA (vacuolating cytotoxin gene), hpaA (a putative adhesin gene), and pfr (bacterial ferritin gene) were generally conserved within approximately the same 25% of the genome; however, the order of these genes also varied. Our study demonstrates that macrodiversity, i.e. variability in gene order, in addition to microdiversity, is a characteristic of the H. pylori genome.

Polymerase chain reaction and an outer membrane protein gene probe for the detection of Porphyromonas gingivalis

A sensitivity assay for Porphyromonas gingivalis based upon the polymerase chain reaction (PCR) was developed. A 426-bp sequence, including a DraI-HincII DNA fragment (278 bp) encoding the 40-kDa outer membrane protein of the P. gingivalis gene was amplified. PCR products were obtained from chromosomal DNAs of the P. gingivalis strains tested but not from those of other oral microorganisms. The lower limit of template DNA detection was 10 pg with 30 cycles and 100 fg with 40 cycles of PCR by agarose gel electrophoresis. The PCR products were hybridized with DraI-HincII DNA fragment internal to the PCR primers regions used. The lower limit of hybridization detection was 10 pg and 10 fg of template DNA with 30 and 40 cycles of PCR, respectively. These results demonstrated the simplicity, rapidity and specificity of the procedure, as well as the use of the DraI-HincII DNA fragment in the identification of P. gingivalis.

Nucleotide sequence and mutational analysis indicate that two Helicobacter pylori genes encode a P-type ATPase and a cation-binding protein associated with copper transport

A 2.7 kb fragment of Helicobacter pylori UA802 chromosomal DNA was cloned and sequenced. Three open reading frames (designated ORF1, ORF2 and ORF3, respectively) were predicted from the DNA sequence, of which ORF1 and ORF2 appeared to be located within the same operon. The deduced 611-amino-acid sequence of ORF1, a P-type ATPase (designated hpCopA), had striking homology (29-38%) with several bacterial P-type ATPase and contained the potential functional domains conserved in P-type ATPases from various sources ranging from bacterial to human. A protein of 66 amino acids (designated hpCopP) encoded by ORF2 shared extensive sequence similarity with MerP, a periplasmic mercuric ion-transporting protein, and contains the heavy metal-binding motif. Disruption of ORF1 with a chloramphenicol-resistance cassette (CAT) rendered the H. pylori mutants more susceptible to cupric ion than their parental strains, whereas there is no significant alteration of susceptibility to Ni2+, Cd2d+ and Hg2+ between the mutants and the parental strains. The results obtained indicate that ORF1 and ORF2 comprise a cation-transporting system which is associated with copper export out of the H. pylori cells.

Molecular dissection of GT-1 from Arabidopsis

We isolated and characterized an Arabidopsis cDNA encoding the DNA binding protein GT-1. This protein factor, which contains 406 amino acids, is highly homologous to the previously described tobacco DNA binding protein GT-1a/B2F but is 26 amino acids longer. Recombinant Arabidopsis GT-1, which was obtained from in vitro translation, bound to probes consisting of four copies of pea small subunit of ribulose bisphosphate carboxylase rbcS-3A box II and required the same GGTTAA core binding site as the binding activity of an Arabidopsis nuclear protein preparation. However, unlike the truncated tobacco GT-1a prepared from Escherichia coli extracts, the full-length Arabidopsis GT-1 bound to pea rbcS-3A box III and Arabidopsis chlorophyll a/b binding protein CAB2 light-responsive elements, both of which contain GATA motifs. Deletion and mutational analyses suggested that the predicted trihelix region of GT-1 is essential for DNA binding. Moreover, GT-1 binds to target DNA as a dimer, and its C-terminal region contains a putative dimerization domain that enhances the binding activity. Transient expression of the GT-1::beta-glucuronidase fusion protein in onion cells revealed the presence of a nuclear localization signal(s) within the first 215 amino acids of GT-1.

Transcription factors in plant growth and development

The target DNA sequences of several classes of plant transcription factors, including basic leucine zipper (bZIP) proteins and Myb-related factors, have been characterized in vivo as well as in vitro. The bZIP proteins, for example, act at ACGT elements, the flanking nucleotides determining their binding specificities. Overexpression, co-suppression, and antisense technology studies of factor genes in transgenic plants have uncovered the roles of bZIP, homeodomain, and MADS box factors in plant growth and development; for example, ectopic expression of pMADS1 alone in early Petunia development is sufficient for homeotic conversion of sepals into petaloid organs.

Sacral chordoma developing two years after low anterior resection for rectal cancer

A 43-year-old male with sacral chordoma associated with rectal cancer is herein reported. A presacral tumor with extensive destruction of S4 and S5 was found 2.5 years after a low anterior resection for advanced rectal mucinous carcinoma. Under the preoperative diagnosis of a solitary sacral metastasis of rectal cancer, the lower sacral segments together with the tumor were removed by amputation at S3. Histologically, the tumor was a chordoma composed of polyhedral cells with an abundant eosinophilic cytoplasm mixed with typical vacuolated physaliferous cells within a myxoid matrix. Colorectal cancer associated with an extracolic primary malignant neoplasm is not uncommon; however, this is only the second case of colorectal cancer associated with chordoma to the best of our knowledge.

Role of Porphyromonas gingivalis 40-kDa outer membrane protein in the aggregation of P. gingivalis vesicles and Actinomyces viscosus

Porphyromonas gingivalis, an important pathogen in periodontitis, produces extracellular vesicles that aggregate with Actinomyces viscosus cells. A 40-kDa outer membrane protein (OMP)-coding gene from P. gingivalis was cloned and the protein was found to be localized in these vesicles. The recombinant 40-kDa OMP did not show aggregation activity. However, affinity-purified antibody against the recombinant protein significantly inhibited aggregation of P. gingivalis vesicles with A. viscosus cells. The antibody also inhibited cellular coaggregation of several strains of P. gingivalis with A. viscosus cells, but not with other periodontal pathogens. Moreover, aggregation of A. viscosus cells with P. gingivalis vesicles was inhibited in a dose-dependent manner by pre-treatment of the A. viscosus cells with the recombinant protein. These findings suggest that the 40-kDa OMP may be an important aggregation factor of P. gingivalis.

Characterization of a gene encoding a DNA binding protein with specificity for a light-responsive element

The sequence element of box II (GTGTGGTTAATATG) is a regulatory component of a light-responsive element present within the upstream region of pea rbcS-3A. The nuclear protein GT-1 was defined previously as a DNA binding activity that interacts with box II. Here, we describe the isolation and characterization of cDNA sequences that encode a DNA binding protein with specificity for this element. The recombinant protein, tobacco GT-1a, shows similar sequence requirements for DNA binding to nuclear GT-1, as assayed by its ability to interact with previously defined 2-bp scanning mutations of box II, and is shown to be immunologically related to nuclear GT-1. The predicted structure of the 43-kD protein derived from the cDNA sequence suggests the presence of a novel helix-helix-turn-helix (HHTH) motif. Comparison between the predicted protein sequence encoded by the tobacco GT-1a cDNA and that of another GT binding protein, rice GT-2, reveals strong amino acid conservation over the HHTH region; this motif appears to be involved in the interaction between the recombinant protein and box II. Genomic DNA gel blot analysis indicated the presence of a small gene family of related sequences within the tobacco nuclear genome. RNA gel blot analysis of tobacco mRNA using the isolated cDNA as a probe showed that transcripts are present in several tissues, including both light-grown and dark-adapted leaves.

Use of non-radioactive DNA probes for detection of Campylobacter jejuni and Campylobacter coli in stool specimens

DNA probes specific for C. jejuni (pDT1720 containing a 1475 base pair fragment) and for C. jejuni and C. coli (pDT1719 containing a 1845 base pair fragment) were isolated from a bacteriophage lambda gt11 genomic library of C. jejuni, using antiserum prepared against a 46 kDa major outer membrane protein of C. jejuni. The two probe-fragments had different restriction maps and were only moderately related by DNA hybridization analysis. A non-radioactive labelling kit which consisted of alkaline phosphatase conjugated anti-digoxigenin antiserum and 5-bromo-4-chloro-3-indoyl phosphate with nitroblue tetrazolium as the colour substrate, which gives a purple colour for positive hybridization, was used to test 140 stool specimens, 70 of which were culture positive and 70 of which wer culture negative for Campylobacter spp. The pDT1720 fragment (C. jejuni probe) could detect a minimum of 1 x 10(5) C. jejuni cells on filters, whereas the pDT1719 fragment (C. coli probe) was 100-fold less sensitive. The C. jejuni probe demonstrated a sensitivity of 93% with culture positive stool samples, however, 15% of culture negative samples were also recorded as positive using this non-radioactive DNA probe.