Comparison of specificity and sensitivity of immunochemical and molecular techniques for reliable detection of<Emphasis Type="Italic">Erwinia amylovora</Emphasis>

Erwinia amylovora [(BURRILL) WINSLOW et al.] (Ea), the causal agent of fire blight, was detected in plant samples and pure bacterial cultures by means of PCR, IFAS and ELISA. Polyclonal antibodies of Neogen Europe Ltd. were used for IFAS and PTA-ELISA and laboratory-generated primers EaF72 and EaR560 for PCR. Using the BIOLOG system and an immature pear fruit assay, identities of all Ea strains were confirmed as the fire blight bacterium. In assays of pure Ea cultures, PTA-ELISA, and both IFAS and PCR were sensitive to concentrations 10(6)-10(5) and 10(5)-10(4) CFU/mL, respectively. When saprophytic bacteria associated with Ea in plant samples were tested as potentially cross-reacting bacteria, PTA-ELISA and IFAS gave 20 and 14 % cross-reactions, respectively. In plant samples, the presence of Ea was more reliably detected by IFAS (at a dilution of 1 : 1000) than by PTA-ELISA (to dilution 1 : 100). The capacity to detect Ea might be increased using an optimized PCR, but for PCR prepared from infected plant samples it was necessary to use the bacterial DNA isolated with a DNeasy Plant Mini Kit (Qiagen). In this case the PCR was sensitive to a concentration of 10(5) CFU/mL. PCR was much more specific than either immunochemical technique, because no false positives were observed when primers EaF72 and EaR560 were used.     

Inhibitory Activity of Probiotic <Emphasis Type="Italic">Bacillus subtilis</Emphasis> UTM 126 Against <Emphasis Type="Italic">Vibrio</Emphasis> Species Confers Protection Against Vibriosis in Juvenile Shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>)

The bacterial strain Bacillus subtilis UTM 126 produced antimicrobial activity against pathogenic Vibrio species, including V. alginolyticus, V. parahaemolyticus, and V. harveyi. The probiotic effect of B. subtilis was tested by feeding juvenile shrimp (Litopenaeus vannamei) food supplemented with B. subtilis (10⁵ CFU/g) for 28 days before an immersion challenge with V. harveyi at 10⁵ CFU/mL for 24 h. The treatment with B. subtilis UTM 126 decreased final mortality to 18.25%, compared with 51.75% in the control group. Bacillus subtilis UTM 126 has potential applications for controlling pathogenic V. harveyi in shrimp aquaculture.     

Screening for fluorescent pseudomonades,isolated from the rhizosphere of tomato,for antagonistic activity toward <Emphasis Type="Italic">Clavibacter michiganensis</Emphasis> subsp<Emphasis Type="Italic">. michiganensis</Emphasis>

Bacterial canker of tomato, caused by Clavibacter michiganensis subsp. michiganensis, continues to be a problem for tomato growers in the Souss-Massa Draa valley, South of Morocco. Assuming that biological control is an alternative for the management of this disease, a total of 303 fluorescent pseudomonads strains isolated from roots and rhizospheric soil of tomato plants were in vitro tested against C. michiganensis subsp. michiganensis. Fluorescent pseudomonads strains which showed the highest antagonistic properties were thereafter investigated for their ability to colonize tomato roots. Our results showed that fluorescent pseudomonads are more represented in rhizospheric soils. However, the most efficient fluorescent pseudomonads isolates were found in the rhizoplane soil and the endorhizosphere. Among 42 spontaneous antibiotic resistant mutants obtained by treatment of the wild-type isolates with five antibiotics (rifampicine, nalidixic acid, ampicilline and chloramphenicol), 28 completely colonized the roots of all tomatoes seedlings used in this investigation. The 42 wild type isolates were then used for in vivo screening with the cotyledon test. Using this test, eight isolates from 42 tested induced a significant decrease of disease incidence and disease symptoms. The eight efficient isolates were then tested for their effectiveness in the protection of tomato plants in pots under greenhouse conditions. Results obtained showed that all tested isolates applied as seed and root treatments reduced significantly (P ≤ 0.001) the incidence of bacterial canker.     

Immunological responses induced by <Emphasis Type="Italic">asd</Emphasis> and <Emphasis Type="Italic">wzy/asd</Emphasis> mutant strains of <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Typhimurium in BALB/c mice

Attenuated bacteria have long been developed as vaccine candidates but can have some disadvantages, such as the potential for damage to immune organs due to insufficient clearance. To minimize these disadvantages, we generated Salmonella enterica serovar Typhimurium mutants SHJ2104 (asd::cm) and HTSaYA (wzy::km, asd::cm). The wzy gene codes for the O-antigen polymerase, which is involved in lipopolysaccharide (LPS) biosynthesis, and asd codes for aspartate β-semialdehyde dehydrogenase, which participates in cell wall formation. The strains synthesized LPS with a short-chain length, and showed lower cytotoxicity and reduced intracellular proliferation in animal cells compared to wild-type bacteria. After oral infection, the mutants were cleared in immune tissues, including the Peyer’s patch, mesenteric lymph node, and spleen, within 5 days. The LD50 of the mutants in Balb/c mice was estimated to be 10⁶ higher than wild-type bacteria when administered either via an oral or i.p. route, indicating that the two strains are highly attenuated. To compare the immune response to and protective effects of the mutants against wild-type bacterial infection, we inoculated the mutants into mice via an oral (1×10¹⁰CFU) or i.p. (1×10⁷ CFU) route once or twice at a two week interval. All immune responses, such as serum IgG and secretory IgA levels, cytokine production, and delayed hypersensitivity, were highly induced by two rounds of immunization. HTSaYA and SHJ2104 induced similar immune responses, and mice immunized with HTSaYA or SHJ2104 via an i.p. route were protected against wild-type Salmonella infection even at 100-fold of the LD₅₀ (5×10⁶ CFU). Taken together, these data indicate that HTSaYA and SHJ2104 could be developed as live attenuated Salmonella vaccine candidates.     

Development of a new loop-mediated isothermal amplification assay for <Emphasis Type="Italic">prt</Emphasis> (<Emphasis Type="Italic">rfbS</Emphasis>) gene to improve the identification of <Emphasis Type="Italic">Salmonella</Emphasis> serogroup D

Loop-mediated isothermal amplification (LAMP) is a promising nucleic acid assay for rapid and cost-effective detection of pathogen-specific sequences within a sample. Development of an appropriate taxonomic group-specific LAMP assay highly relies on the design of proper primers to cover all major members of the taxon. Regarding this fact, we designed and evaluated a new LAMP primer set specific to prt (rfbS) gene for rapid identification of Salmonella serogroup D serotypes. Unlike the previously reported LAMP assay for serogroup D which detects solely the non-typhoidal serotypes; the new LAMP primers set detects both typhoidal and non-typhoidal serotypes of this serogroup with a detection limit of 10 CFU/rection. Furthermore, the technique was successfully applied to artificially contaminated meat samples with an inoculation level of 1–5 CFU/250 ml of Salmonella Enteritidis, following a 5-h pre-enrichment step in tryptic soy broth. Overall, the new LAMP assay and its optimized setup would be useful for fast diagnosis of food poisoning incidents caused by these bacteria.     

Detection of <Emphasis Type="Italic">Yersinia enterocolitica</Emphasis> in Alfalfa,Mung Bean,Cilantro, and Mamey Sapote (<Emphasis Type="Italic">Pouteria sapota</Emphasis>) Food Matrices Using DNA Microarray Chip Hybridization

Four different food matrices (alfalfa, cilantro, mamey sapote, and mung bean) were contaminated with three different dilutions 10⁶, 10⁴, and 10³ cfu/g of Yersinia enterocolitica. DNA was isolated from each food mix and used in chromosomal amplifications. The amplified DNA was used as templates in single PCR reactions of the four genes (virF, ail, yst, and blaA) followed by mixing the four reactions for one PCR primer extension reaction. The presence and the limit of detection of four genes in four food matrices were established by microarray hybridization. Data revealed the diversity of signal intensities. Neither the microarray chip hybridization nor the single PCR amplification could detect virF’s presence located on a plasmid. Ail was detected in 10³ cfu/g, whereas blaA and yst were detected from 10⁵ to 10⁶ cfu/g in all food matrices. Therefore, the ail gene could be the gene of choice in identifying Y. enterocolitica in alfalfa, cilantro, mamey, and mung bean. Other genes—blaA, yst, virF—exhibited wide variability in hybridization signals, highlighting the need of a better DNA purification step prior to DNA microarray hybridization.     

<Emphasis Type="Italic">cry1</Emphasis> genes from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>: specificity determination and implications for primer design

Some pest management programs employ PCR to identify cry1 genes from Bacillus thuringiensis to predict bacterial toxicity towards different insect pests. However, due to changes on the mode of action of the Cry proteins, new primers had to be designed to detect the new genes. Therefore, an ‘in-silico’ study of genetic sequences from five cry1 subclasses was carried out and characterized by molecular tools. The design of new primers allows for more precise selection of B. thuringiensis isolates, helping to better direct the programs employing biological control.     

A Species-Specific Polymerase Chain Reaction Assay for Rapid and Sensitive Detection of <Emphasis Type="Italic">Colletotrichum</Emphasis><Emphasis Type="Italic">capsici</Emphasis>

Colletotrichum capsici is an important fungal species that causes anthracnose in many genera of plants causing severe economic losses worldwide. A primer set was designed based on the sequences of the ribosomal internal transcribed spacer (ITS1 and ITS2) regions for use in a conventional PCR assay. The primer set (CcapF/CcapR) amplified a single product of 394 bp with DNA extracted from 20 Mexican isolates of C. capsici. The specificity of primers was confirmed by the absence of amplified product with DNA of four other Colletotrichum species and eleven different fungal genera. This primer set is capable of amplifying only C. capsici from different contaminated tissues or fungal structures, thereby facilitating rapid diagnoses as there is no need to isolate and cultivate the fungus in order to identify it. The sensitivity of detection with this PCR method was 10 pg of genomic DNA from the pathogen. This is the first report of a C. capsici-specific primer set. It allows rapid pathogen detection and provides growers with a powerful tool for a rational selection of fungicides to control anthracnose in different crops and in the post-harvest stage.     

Improving Toxicity of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Strain Contains the <Emphasis Type="Italic">cry8Ca</Emphasis> Gene Specific to <Emphasis Type="Italic">Anomala corpulenta</Emphasis> Larvae

The cry8C-type gene designated cry8Ca2, which was cloned and sequenced from a Bacillus thuringiensis isolate HBF-1 in China, consisted of an open reading frame of 3483 bp encoding a protein of 1160 amino-acid residues. Sequence analysis showed that the Cry8Ca2 protoxin of 130.5 kDa had 99.9% sequence homology with the previously reported Cry8Ca1 protein, with one mismatch between the two amino-acid sequences. When the Cry8Ca2 toxin was expressed in a crystal-negative strain of B. thuringiensis (HD-73⁻), elliptical crystals were produced. Cell extracts from this recombinant strain showed insecticidal activity against Anomala corpulenta larva. Mutant cry8Ca2 genes, produced by polymerase chain reaction amplification with Taq DNA polymerase, were used to develop recombinant B. thuringiensis strains. Mutants producing higher levels of insecticidal activity were identified by bioassay. Thirty-five mutants forming crystals were characterized, and two of them showed significantly increased insecticidal activity against A. corpulenta larva. The 50% lethality concentrations (LC₅₀) of the two mutants were 0.2334 × 10⁸ and 0.2591 × 10⁸ colony-forming units g⁻¹, considerably lower than the LC₅₀ of the wild-type strain HBF-1 (0.9583 × 10⁸ CFU g⁻¹) and that of B. thuringiensis serovar japonensis strain Buibui (1.0752 × 10⁸ CFU g⁻¹).     

Transfer of the chromosomally encoded tetracycline resistance gene <Emphasis Type="Italic">tet</Emphasis>(M) from marine bacteria to <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Enterococcus faecalis</Emphasis>

The transferability of the tetracycline (TC) resistance gene tet(M) from marine bacteria to human enteric bacteria was examined by a filter-mating method. Vibrio spp., Lactococcus garvieae, Bacillus spp., Lactobacillus sp., and Paenibacillus sp. were used as donors, and Escherichia coli JM109 and Enterococcus faecalis JH2-2 were used as recipients. The combination of Vibrio spp. and E. coli resulted in 5/68 positive transconjugants with a transfer rate of 10⁻⁷ to 10⁻³; however, no transfer was observed with E. faecalis. In case of L. garvieae and E. faecalis, 6/6 positive transconjugants were obtained with a transfer rate of 10⁻⁶ to 10⁻⁵; however, no transfer was observed with E. coli. The tet(M) gene of Bacillus, Lactobacillus, and Paenibacillus were not transferred to either E. coli or E. faecalis. tet(M) transfer was confirmed in positive E. coli and E. faecalis transconjugants by polymerase chain reaction (PCR) and Southern hybridization. All the donor strains did not harbor plasmids, while they all harbored transposon Tn916. In the transconjugants, the transposon was not detected by PCR, suggesting the possible transfer of tet(M) from the marine bacterial chromosome to the recipient chromosome. This is the first report to show that tet(M) can be transferred from marine bacteria to human enteric bacteria in a species-specific manner.     

Rapid Detection Device for <Emphasis Type="Italic">Salmonella typhi</Emphasis> in Milk,Juice, Water and Calf Serum

A limit of detection of 200 CFU/mL of Salmonella typhi spiked in various sample matrices were achieved in 30 min. The sample matrices were raw/unprocessed milk, commercially available milk, juice from packed bottles, fresh juice from carts, potable water, turbid water and calf serum. The complete protocol comprised of three steps: (a) cell lysis (b) nucleic acid amplification and (c) an in situ optical detection. The cell lysis was carried out using a simple heating based protocol, while the loop-mediated isothermal amplification of DNA was carried out by an in-house designed and fabricated system. The developed system consists of an aluminum block fitted with two cartridge heaters along with a thermocouple. The system was coupled to a light source and spectrometer for a simultaneous in situ detection. Primers specific for STY2879 gene were used to amplify the nucleic acid sequence, isolated from S. typhi cells. The protocol involves 15 min of cell lysis and DNA isolation followed by 15 min for isothermal amplification and simultaneous detection. No cross-reactivity of the primers were observed at 10⁶ CFU/mL of Escherichia coli, Vibrio cholerae, Salmonella typhimurium, Salmonella paratyphi A, Pseudomonas aeruginosa, Bacillus cereus, Lysteria monocytogenes, Clostridium botulinum, Staphylococcus aureus and Salmonella havana. In addition, the system was able to detect S. typhi of 200 CFU/mL in a concoction of 10⁶ CFU/mL of E. coli, 10⁶ CFU/mL of V. cholerae, and 10⁶ CFU/mL of hepatocyte-derived cellular carcinoma HUH7 cells. The proposed rapid diagnostic system shows a promising future in the field of food and medical diagnostics.     

Development of expressed sequence tag-derived microsatellite markers for <Emphasis Type="Italic">Saccharina</Emphasis> (<Emphasis Type="Italic">Laminaria</Emphasis>) <Emphasis Type="Italic">japonica</Emphasis>

Expressed sequence tag-derived microsatellite markers (EST-SSR) were generated and characterized in Laminaria japonica using data mining from updated public EST databases and polymorphism testing. Fifty-eight of 578 ESTs (10.0%) containing various repeat motifs were used to design polymerase chain reaction (PCR) amplification primers. A total of 12 pairs of primer were generated and used in the PCR amplification. Alleles per locus ranged from two to ten (average of 5.7). The observed heterozygosities and expected heterozygosities were from 0.045 to 0.543 and from 0.056 to 0.814, respectively. All loci were in Hardy–Weinberg equilibrium and no linkage disequilibrium was detected. These robust, informative, and potentially transferable polymorphic markers appear suitable for population, genetic, parentage, and mapping studies of L. japonica.     

An eight-hour PCR-based technique for detection of <Emphasis Type="Italic">Salmonella</Emphasis> serovars in seafood

A rapid and sensitive 8-h PCR assay has been developed for detection of Salmonella serovars in seafood. A total of 110 fresh and raw seafood samples were analysed for the presence of Salmonella using different enrichment periods prior to PCR assay. Seafood samples included in this study were fish, shrimps, mussels, crabs, edible oysters, and clams, collected from local fish markets in Cochin (India). The assay was performed with a Salmonella-specific 284 bp invA gene amplicon. Specificity and sensitivity of the assay were ascertained with seafoods spiked with viable Salmonella cells to a level of 10⁶ to 2 CFU per 25 g. Detection efficiency of the assay increased with increasing enrichment period for seafood, and 33.6% of seafood samples were found positive for Salmonella by 8-h PCR assay. Detection limit for the 8-h PCR assay showed visible 284 bp amplicon from seafood homogenates spiked with 2 CFU per 25 g. Seafood samples spiked with different Salmonella serovars, namely Salmonella typhi, Salmonella typhimurium, Salmonella enteritidis, Salmonella mbandka, Salmonella bareilly, and Salmonella weltevreden, were detected, confirming this technique would be ideal for detection of the Salmonella serovars prevalent in seafood. This study also covered inhibition by the seafood matrix and the detection limit for dead Salmonella cells during the PCR assay. There was no visible inhibition of this Salmonella PCR assay by seafood matrices. The detection limit for dead Salmonella cells by 8-h PCR assay was 2 × 10³ CFU per 25 g seafood. The data indicated that dead cells of Salmonella in naturally contaminated seafood samples do not interfere with the assay resulting in false positives.     

Rhizosphere competent <Emphasis Type="Italic">Pantoea agglomerans</Emphasis> enhances maize (<Emphasis Type="Italic">Zea mays</Emphasis>) and chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.) growth,without altering the rhizosphere functional diversity

Plant growth promoting Pantoea agglomerans NBRISRM (NBRISRM) was able to produce 60.4 μg/ml indole acetic acid and solubilize 77.5 μg/ml tri-calcium phosphate under in vitro conditions. Addition of 2% NaCl (w/v) in the media induced the IAA production and phosphate solubilization by 11% and 7%, respectively. For evaluating the plant growth promotory effect of NBRISRM inoculation a micro plot trial was conducted using maize and chickpea as host plants. The results revealed significant increase in all growth parameters tested in NBRISRM inoculated maize and chickpea plants, which were further confirmed by higher macronutrients (N, P and K) accumulation as compared to un-inoculated controls. Throughout the growing season of maize and chickpea, rhizosphere population of NBRISRM were in the range 10⁷–10⁸ CFU/g soil and competing with 10⁷–10⁹ CFU/g soil with heterogeneous bacterial population. Functional richness, diversity, and evenness were found significantly higher in maize rhizosphere as compared to chickpea, whereas NBRISRM inoculation were not able to change it, in both crops as compared to their un-inoculated control. To the best of our knowledge this is first report where we demonstrated the effect of P. agglomerans strain for improving maize and chickpea growth without altering the functional diversity.     

Sulfolipid accumulation in <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> disrupted in the <Emphasis Type="Italic">mce2</Emphasis> operon

Mycobacterium tuberculosis, the causative agent of tuberculosis, has a lipid-rich cell wall that serves as an effective barrier against drugs and toxic host cell products, which may contribute to the organism’s persistence in a host. M. tuberculosis contains four homologous operons called nice (mce1–4) that encode putative ABC transporters involved in lipid importation across the cell wall. Here, we analyzed the lipid composition of M. tuberculosis disrupted in the mce2 operon. High resolution mass spectrometric and thin layer chromatographic analyses of the mutant’s cell wall lipid extracts showed accumulation of SL-1 and SL₁₂₇₈ molecules. Radiographic quantitative analysis and densitometry revealed 2.9, 3.9 and 9.8-fold greater amount of [³⁵S] SL-1 in the mce2 operon mutant compared to the wild type M. tuberculosis during the early/mid logarithmic, late logarithmic and stationary phase of growth in liquid broth, respectively. The amount of [³⁵S] SL₁₂₇₈ in the mutant also increased progressively over the same growth phases. The expression of the mce2 operon genes in the wild type strain progressively increased from the logarithmic to the stationary phase of bacterial growth in vitro, which inversely correlated with the proportion of radiolabel incorporation into SL-1 and SL₁₂₇₈ at these phases. Since the mce2 operon is regulated in wild type M. tuberculosis, its cell wall may undergo changes in SL-1 and SL₁₂₇₈ contents during a natural course of infection and this may serve as an important adaptive strategy for M. tuberculosis to maintain persistence in a host.     

Identification of SNPs and development of functional markers for LMW-GS genes at <Emphasis Type="Italic">Glu-D3</Emphasis> and <Emphasis Type="Italic">Glu-B3</Emphasis> loci in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Low-molecular-weight glutenin subunits (LMW-GS) have great effect on wheat processing quality, but were numerous and difficult to dissect by SDS-PAGE. The development of functional markers may be the most effective way for a clear discrimination of different LMW-GS genes. In the present study, three different approaches were used to identify SNPs of different genes at Glu-D3 and Glu-B3 loci in bread wheat for the development of six STS markers (3 for Glu-D3 and 3 for Glu-B3 genes) that were validated with distinguished wheat cultivars. Firstly, seven LMW-GS gene sequences ( AY585350, AY585354, AY585355, AY585356, AY585349, AY585351 and AY585353 ) from Aegilops tauschii, the diploid donor of the D-genome of bread wheat, were chosen to design seven pairs of AS-PCR primers for Glu-D3 genes. By amplifying the corresponding genes from five bread wheat cultivars with different Glu-D3 alleles (a, b, c, d and e) and Ae. tauschii, a primer set, S13F2/S13R1, specific to the gene AY585356, was found to be positive to cultivars with alleles Glu-D3c and d. Nevertheless, the other five pairs of primers designed from AY585350, AY585349, AY585353, AY585354 and AY585355, respectively, did not produce specific PCR products to the cultivars tested. Secondly, all the PCR products from the five primer sets without specific characteristics were sequenced and an SNP from the gene AY585350 was detected in the cultivar Hartog, which resulted in the second STS marker S1F1/S1R3 specific to the allelic variant of AY585350. Thirdly, three Glu-D3 sequences (AB062851, AB062865 and AB062872) and three Glu-B3 sequences (AB062852, AB062853 and AB062860) defined by Ikeda et al. (2002) were chosen to query wheat EST and NR databases, and DNA markers were developed based on the putative SNPs among the sequences. Using this approach, four STS markers were developed and validated with 16-19 bread wheat cultivars. The primer set T1F4/T1R1 was also a Glu-D3 gene-specific marker for AB062872, while T2F2/T2R2, T5F3/T5R1 and T13F4/T13R3 were all Glu-B3 gene specific markers for AB062852, BF293671 and AY831800, respectively. The chromosomal locations of the six markers were verified by amplifying the genomic DNA of Ae. tauschii (DD), T. monococcum (AA) and T. turgidum (AABB) entries, as well as Chinese Spring and its group 1 chromosome nulli-tetrasomic lines. The results are useful to discriminate the corresponding Glu-D3 and Glu-B3 genes in wheat breeding programs.     

Benefits of <Emphasis Type="Italic">Helicobacter pylori</Emphasis><Emphasis Type="Italic">cagE</Emphasis> genotyping in addition to <Emphasis Type="Italic">cagA</Emphasis> genotyping: a Bulgarian study

Associations of Helicobacter pylori cagE status with complex patient characteristics remain to be elucidated in Eastern Europe. The aim of this study was to assess the frequencies of cagE gene and cagA/cagE combinations in H. pylori strains from symptomatic Bulgarian patients and to improve cagA detection. cagA and cagE genotypes were evaluated in 219 patients with single-strain infections. In total, 84.9% of strains were cagA ⁺, while 68.5% were cagE ⁺. cagA ⁺, cagE ⁺, and cagA ⁺/cagE ⁺ strains were more prevalent in peptic ulcer (93.8%, 84.4%, and 84.4%) compared with nonulcer patients (81.3%, 61.9%, and 61.3%, respectively). In elderly patients, cagE ⁺ and cagA ⁺/cagE ⁺ strains were 1.9-fold more common than in the 12 children evaluated. Only 10% of the elderly subjects harbored low-virulence cagA ⁺/cagE ⁻ strains compared with 16.8% of adults and 41.7% of children. Intriguingly, prevalence of the cagA ⁺/cagE ⁻ genotype was 2.1-fold lower in men than in women, suggesting a higher frequency of more virulent strains in men. The presence of both cag genes and combinations was not linked to strain susceptibility to clarithromycin or metronidazole, place of residence, or prior therapy. Use of an extra primer pair increased cagA detection in 14.7% of 31 cagA ⁻ strains. In conclusion, use of a second primer pair for the cagA gene can be recommended in countries with common cagA ⁺ strains. Although both cag genes were linked to severe diseases in Bulgarian patients, the best discrimination of virulent strains was obtained by the cagA/cagE combination or by the cagE gene alone. cagE prevalence increased gradually with patient age, while the cagA ⁺/cagE ⁻ genotype, implying a disrupted cag pathogenicity island, was associated with both younger age and female gender.     

Isolation and screening of <Emphasis Type="Italic">phlD</Emphasis><Superscript>+</Superscript> plant growth promoting rhizobacteria antagonistic to <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis>

Tomato (Lycopersicon esculentum) is important widely grown vegetable in India and its productivity is affected by bacterial wilt disease infection caused by Ralstonia solanacearum. To prevent this disease infection a study was conducted to isolate and screen effective plant growth promoting rhizobacteria (PGPR) antagonistic to R. solanacearum. A total 297 antagonistic bacteria were isolated through dual culture inoculation technique, out of which forty-two antagonistic bacteria were found positive for phlD gene by PCR amplification using two primer sets Phl2a:Phl2b and B2BF:BPR4. The genetic diversity of phlD ⁺ bacteria was studied by amplified 16S rDNA restriction analysis and demonstrated eleven groups at 65% similarity level. Out of these 42 phlD ⁺ antagonistic isolates, twenty exhibited significantly fair plant growth promoting activities like phosphate solubilization (0.92–5.33%), 25 produced indole acetic acid (1.63–7.78 μg ml⁻¹) and few strains show production of antifungal metabolites (HCN and siderophore). The screening of PGPR (phlD ⁺) for suppression of bacterial wilt disease in glass house conditions was showed ten isolated phlD ⁺ bacteria were able to suppress infection of bacterial wilt disease in tomato plant (var. Arka vikas) in the presence R. solanacearum. The PGPR (phlD ⁺) isolates s188, s215 and s288 was observed to be effective plant growth promoter as it shows highest dry weight per plant (3.86, 3.85 and 3.69 g plant⁻¹ respectively). The complete absence of wilt disease symptoms in tomato crop plants was observed by these treatments compared to negative control. Therefore inoculation of tomato plant with phlD ⁺ isolate s188 and other similar biocontrol agents may prove to be a positive strategy for checking wilt disease and thus improving plant vigor.     

Anti-amoebic properties of a Malaysian marine sponge <Emphasis Type="Italic">Aaptos</Emphasis> sp<Emphasis Type="Italic">.</Emphasis> on <Emphasis Type="Italic">Acanthamoeba castellanii</Emphasis>

Crude methanol extracts of a marine sponge, Aaptos aaptos, collected from three different localities namely Kapas, Perhentian and Redang Islands, Terengganu, Malaysia, were tested in vitro on a pathogenic Acanthamoeba castellanii (IMR isolate) to examine their anti-amoebic potential. The examination of anti-Acanthamoebic activity of the extracts was conducted in 24 well plates for 72 h at 30 °C. All extracts possessed anti-amoebic activity with their IC₅₀ values ranging from 0.615 to 0.876 mg/mL. The effect of the methanol extracts on the surface morphology of A. castellanii was analysed under scanning electron microscopy. The ability of the extracts to disrupt the amoeba cell membrane was indicated by extensive cell’s blebbing, changes in the surface morphology, reduced in cell size and with cystic appearance of extract-treated Acanthamoeba. Number of acanthapodia and food cup was also reduced in this Acanthamoeba. Morphological criteria of apoptosis in Acanthamoeba following treatment with the sponge’s extracts was determined by acridine orange-propidium iodide staining and observed by fluorescence microscopy. By this technique, apoptotic and necrotic cells can be visualized and quantified. The genotoxic potential of the methanol extracts was performed by the alkaline comet assay. All methanol extracts used were significantly induced DNA damage compared to untreated Acanthamoeba by having high percentage of scores 1, 2, and 3 of the DNA damage. Results from cytotoxicity and genotoxicity studies carried out in the present study suggest that all methanol extracts of A. aaptos have anti-amoebic properties against A. castellanii.     

Endophytic yeasts in <Emphasis Type="Italic">Malus domestica</Emphasis> and <Emphasis Type="Italic">Pyrus communis</Emphasis> fruits under anthropogenic impact

Yeast abundance and species diversity on the surface and in inner tissues of Malus domestica and Pyrus communis fruits under high anthropogenic impact in the city of Moscow (Russia) were studied. Results demonstrated that abundance of epiphytic yeasts on the fruits increased gradually, reaching the maximum of 3.2 × 10⁴ CFU/g on mature fruits. During summer, abundance of endophytes did not change significantly (variation near 2.5 × 10³ CFU/g) until complete maturation, while in September their numbers increased to 10⁴ CFU/g. Basidiomycetous yeasts (Filobasidium wieringae, F. magnum, Rhodotorula glutinis, and Rhodosporidiobolus colostri) predominated on the fruit surface. Ascomycetous species were the most diverse group inside the fruits, which quantitatively increased through maturation. It was found that the share of opportunistic species Candida parapsilosis in internal tissues was significant during the entire period of fruit formation and development under anthropogenic impact in the city. Specific properties of epiphytic and endophytic yeast communities developing in natural ecological niches under synanthropic conditions and anthropogenic impact are discussed.