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Evolutionary relationships among Aspergillus terreus isolates and their relatives.

Aspergillus terreus is a ubiquitous fungus in our environment. It is an opportunistic human pathogen and economically important as the main producer of lovastatin, a cholesterol lowering drug. Our aim was to examine the genetic variability of A. terreus and closely related species using molecular and analytical techniques. Lovastatin production was examined by HPLC. Lovastatin was produced by seven isolates belonging to the species A. terreus. RAPD analyses were carried out using 25 different random primers. Neighbor-joining analysis of RAPD data (120 characters) resulted in clustering of the A. terreus isolates into distinct groups. Some correlation was observed between lovastatin producing abilities of the isolates and their position on the dendrogram based on RAPD profiles. The internal transcribed spacer region and the 5.8S rRNA gene of A. terreus and related isolates was also sequenced. Phylogenetic analysis of sequence data let us classify the isolates into different clades which mostly correspond to the species Aspergillus terreus, Aspergillus flavipes, Aspergillus niveus, Aspergillus carneus and Aspergillus janus/A. janus var. brevis. Aspergillus allahabadii, A. terreus var. aureus and A. niveus var. indicus belonged to the A. niveus clade, while an Aspergillus isolate previously classified as A. niveus was most closely related to A. flavipes isolates. Aspergillus anthodesmis formed a distinct branch on the tree. Although it was previously suggested based on 28S rDNA sequence data that Aspergillus section Terrei should include A. carneus and A. niveus isolates, phylogenetic analysis of ITS sequences indicate that A. flavipes isolates are more closely related to A. terreus than A. carneus isolates. Our data suggest that sections Terrei and Flavipedes should be merged. However, further loci should be analysed to draw more definite conclusions.

Animals↗

Molecular diversity and relationship within Lactococcus lactis, as revealed by randomly amplified polymorphic DNA (RAPD).

Lactococcus lactis strains are widely used in industrial dairy fermentations. Conventional phenotypic tests have been used for years to classify members of this species into two subspecies, lactis and cremoris, and play a key role in the choice of strains to be used in particular cheese fermentations. DNA hybridisation techniques have also been used for strain classification, giving rise to two genome homology groups. However, results showed discrepancies between the two methods of classification. We applied the randomly amplified polymorphic DNA fingerprinting (RAPD) technique to resolve previous contradictions in lactococcal classifications. Unlike usual RAPD methods, we use three primers to classify 113 strains and integrate the resulting information by a digitised programme used for this purpose. Our analysis revealed three major RAPD groups, designated G1, G2 and G3. G1 and G3 contain strains of the lactis subspecies, and G2 contains strains of the cremoris subspecies, as previously defined by phenotypic characteristics. Moreover, group G1 corresponds to one genome homology group, and groups G2 and G3 correspond to the second one. The taxonomic structure within L. lactis is therefore unusual: two distinct genetic groups of strains show indistinguishable phenotypes, while conversely, two phenotypically distinct groups are genetically homologous. We hypothesize that a subfamily of the subsp. lactis group gave rise to the cremoris subspecies.

DNA Fingerprinting↗

Aeromonas hydrophila clinical and environmental ecotypes as revealed by genetic diversity and virulence genes.

Aeromonas hydrophila strains recovered from clinical samples and ambient sources were phenotypically and genetically identified. In addition, the distribution of putative virulence factors was assayed. To determine the genetic diversity of these strains, random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC)-PCR markers were used. The discriminatory ability of the techniques, using Simpson's index, was 0.96 for both methods. The most consistent dendrogram was obtained when RAPD and ERIC data were combined. The genetic diversity revealed a high intra-specific genetic diversity (h=0.364+/-0.024 and I=0.538+/-0.030). The strains showed a tendency to cluster according to their origin of isolation (best-cut test 0.80 and bootstrap values >50%). The present study demonstrates and quantifies the high intra-specific diversity within this species and reveals a clear differentiation of strains according to their ecological origin. The distribution of virulence-related genes confirm that A. hydrophila is a genetically heterogeneous species that harbour ecotypes which have different pathogenic potential to human and other animals.

Aeromonas hydrophila↗

[Molecular techniques applied in species identification of Toxocara].

Toxocarosis is still an important and actual problem in human medicine. It can manifest as visceral (VLM), ocular (OLM) or covert (CT) larva migrans syndroms. Complicated life cycle of Toxocara, lack of easy and practical methods of species differentiation of the adult nematode and embarrassing in recognition of the infection in definitive hosts create difficulties in fighting with the infection. Although studies on human toxocarosis have been continued for over 50 years there is no conclusive answer, which of species--T. canis or T. cati constitutes a greater risk of transmission of the nematode to man. Neither blood serological examinations nor microscopic observations of the morphological features of the nematode give the satisfied answer on the question. Since the 90-ths molecular methods were developed for species identification and became useful tools being widely applied in parasitological diagnosis. This paper cover the survey of methods of DNA analyses used for identification of Toxocara species. The review may be helpful for researchers focused on Toxocara and toxocarosis as well as on detection of new species. The following techniques are described: PCR (Polymerase Chain Reaction), RFLP (Restriction Fragment Length Polymorphism), RAPD (Random Amplified Polymorphic DNA) and SSCP (Single Strand Conformation Polymorphism).

Animals↗

Mycoplasmosis in captive crows and robins from Minnesota.

Mycoplasma sturni is a recently described organism previously associated with conjunctivitis in European starlings (Sturnus vulgaris), northern mockingbirds (Mimus polyglottos) and blue jays (Cyanocitta cristata). Herein we describe the isolation of M. sturni from an American crow (Corvus brachyrhynchos) presenting with conjunctivitis. A nested-PCR was designed for identification of M. sturni in clinical specimens and the sensitivity of the reaction was found to be 10 colony-changing units. The organism was found in asymptomatic American crows caged with a nestmate of the crow with conjunctivitis. Mycoplasma sturni also was found in asymptomatic American robins (Turdus migratorius) and in a European starling (Sturnus vulgaris) housed at the same facility as the crows. Heterogenity of M. sturni isolates from different host species was found by random amplified polymorphic DNA (RAPD) analyses. Heterogeneity also was found among M. sturni isolates recovered from American crows. We suggest that M. sturni can successfully infect American crows and American robins with or without the presence of clinical disease. Furthermore, we demonstrate that nested-PCR is an effective method for the detection of M. sturni and that substantial genetic heterogeneity exists among natural isolates of this bacterial pathogen.

Animals↗

Identification of Bacillus thuringiensis subsp. kurstaki strain HD1-Like bacteria from environmental and human samples after aerial spraying of Victoria, British Columbia, Canada, with Foray 48B.

Aerial applications of Foray 48B, which contains Bacillus thuringiensis strain HD1, were carried out on 9 to 10 May, 19 to 21 May, and 8 to 9 June 1999 to control European gypsy moth (Lymantria dispar) populations in Victoria, British Columbia, Canada. A major assessment of the health impact of B. thuringiensis subsp. kurstaki was conducted by the Office of the Medical Health Officer of the Capital Health Region during this period. Environmental (air and water) and human (nasal swab) samples, collected before and after aerial applications of Foray 48B, both in the spray zone and outside of the spray zone, were analyzed for the presence of strain HD1-like bacteria. Random amplified polymorphic DNA analysis, cry gene-specific PCR, and dot blot DNA hybridization techniques were used to screen over 11,000 isolates of bacteria. We identified bacteria with genetic patterns consistent with those of B. thuringiensis subsp. kurstaki HD1 in 9,102 of 10,659 (85.4%) isolates obtained from the air samples, 13 of 440 (2.9%) isolates obtained from the water samples, and 131 of 171 (76.6%) isolates from the nasal swab samples. These analyses suggest that B. thuringiensis subsp. kurstaki HD1-like bacteria were present both in the environment and in the human population of Victoria prior to aerial applications of Foray 48B. The presence of B. thuringiensis subsp. kurstaki HD1-like bacteria in human nasal passages increased significantly after the application of Foray 48B, both inside and outside the spray zone.

Adult↗

A first linkage map of pecan cultivars based on RAPD and AFLP markers.

We report here the first genetic linkage maps of pecan [Carya illinoinensis (Wangenh.) K. Koch], using random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers. Independent maps were constructed for the cultivars 'Pawnee' and 'Elliot' using the double pseudo-testcross mapping strategy and 120 F1 seedlings from a full-sib family. A total of 477 markers, including 217 RAPD, 258 AFLP, and two morphological markers were used in linkage analysis. The 'Pawnee' linkage map has 218 markers, comprising 176 testcross and 42 intercross markers placed in 16 major and 13 minor (doublets and triplets) linkage groups. The 'Pawnee' linkage map covered 2,227 cM with an average map distance of 12.7 cM between adjacent markers. The 'Elliot' linkage map has 174 markers comprising 150 testcross and 22 intercross markers placed in 17 major and nine minor linkage groups. The 'Elliot' map covered 1,698 cM with an average map distance of 11.2 cM between adjacent markers. Segregation ratios for dichogamy type and stigma color were not significantly different from 1:1, suggesting that both traits are controlled by single loci with protogyny and green stigmas dominant to protandry and red stigmas. These loci were tightly linked (1.9 cM) and were placed in 'Elliot' linkage group 16. These linkage maps are an important first step towards the detection of genes controlling horticulturally important traits such as nut size, nut maturity date, kernel quality, and disease resistance.

Carya↗

Strain typing of polish Leptosphaeria maculans isolates supports at the genomic level the multi-species concept of aggressive and non-aggressive strains.

47 Polish isolates of the blackleg fungus Leptosphaeria maculans (Phoma lingam) were compared with eight well-defined reference strains from Germany, France, Denmark, Australia and one Polish isolate of Phoma nigrificans. The isolates were tested (i) for growth characteristics, (ii) for their ability to form sirodesmins, (iii) for cellulolytic enzymes, and (iv) for pathotype-differentiating molecular markers generated by RAPD-PCR, PCR analysis with pathotype-specific primer pairs and PFGE. With two exceptions all Polish isolates do not form sirodesmins. grow rapidly without penetrating into the substrate and form in most cases yellow or brown pigments in Czapek-Dox liquid cultures. With respect to cellulase secretion and molecular fingerprinting Polish A strains (aggressive) fit into the general picture of the aggressive pathotype group, whereas the NA isolates (non-aggressive) display a higher degree of heterogeneity. This matches with inoculation tests on rape seedlings, which revealed a considerable number of isolates ranging in aggressivity between the conventional A and NA pathotype group. Molecular fingerprinting techniques unequivocally sorted intermediately aggressive isolates into the NA pathotype group. Isolate Ph Bial, which produces sirodesmin but groups within NA isolates according to molecular and physiological markers, may represent a novel third group besides A and NA strains with intermediate aggressivity (IA). We hybridized Southern blots of electrophoretically separated chromosomes with radioactively labelled PCR fragments used for differentiation between A and NA isolates. The specificity of diagnostic PCR amplicons is reflected at the genomic level. The A probe reveals a single hybridizing chromosome exclusively in A strains. The NA probe reveals several chromosomes and is specific for the NA pathotype group. Chromosomes from intermediately aggressive strains are equally well recognized by the NA probe as are Polish isolates with low aggressivity and give no signal with the A probe. Both diagnostic DNA sequences are highly specific for the pathotype group they were derived from. The lack of correspondence of both genetic elements between A and NA strains strongly supports the idea of ascribing the pathotype groups to different species. Whereas the A pathotype group is genetically homogeneous and congruent with the species Leptosphaeria maculans, the NA group needs to be revised taxonomically. NA isolates will presumably have to be split into several independent species.

Ascomycota↗

Development of specific PCR primers for the detection of Rhizoctonia solani AG 2-2 LP from the leaf sheaths exhibiting large-patch symptom on zoysia grass.

Detection of Rhizoctonia solani AG 2-2 LP isolates causing large-patch disease on zoysia grass was done using polymerase chain reaction (PCR). Specific primers were designed based on an amplified region using random amplified polymorphic DNA (RAPD)-PCR. Fifteen primers and three cultural types of R. solani AG 2-2 (types IIIB, IV and LP) were used for RAPD-PCR. The banding patterns by RAPD-PCR showed that the three cultural types were clearly distinguishable. A dendrogram constructed from the results of RAPD-PCR showed that the three cultural types of AG 2-2 clustered separately. The sequence of one PCR-amplified region which appeared only in LP isolates using primer A09 was selected for designing specific primers. Primer pair A091-F/R gave a single product from pure fungal DNA of LP isolates but not from those of the other two types (IIIB and IV), R. solani AG 1, 2-1, 2-3, 2-tulip, 3-10 and BI isolates and other turfgrass fungal pathogens. Primer pair A091-F/R also gave a single product from diseased leaf sheaths and this product was in accordance with those of pure fungal DNA of LP isolates. Primer pair A091-F/R did not yield PCR product from healthy leaf sheaths. The frequencies of detection of LP isolates from leaf sheaths of zoysia grass using PCR with primer pair A091-F/R were higher than those of the conventional isolation technique. These results showed that the PCR-based technique using specific primers A091-F/R is useful for the rapid detection of LP isolates from leaf sheaths of zoysia grass exhibiting large-patch symptoms.

Cluster Analysis↗

Molecular typing by random amplification of polymorphic DNA (RAPD) and detection of virulence genes of Salmonella enterica subspecies enterica serovar Gallinarum biovar gallinarum.

Salmonella enterica subspecies enterica serovar Gallinarum biovar Gallinarum is the causative agent of fowl typhoid in chickens, outbreaks of which have devastated poultry populations in Korea since 1992. In order to identify genetic differences among S. Gallinarum isolates, bacteria were examined using the random amplified polymorphic DNA (RAPD) method. Of 13 arbitrary primers screened initially, the primer designated as universal rice primer-6 (URP-6) was selected for subsequent typing assays because it produced a distinctive and reproducible DNA fingerprint for a S. Gallinarum reference strain. URP-6-based RAPD analysis assigned 30 S. Gallinarum isolates into 6 types, with 26 isolates (86.6%) belonging to 2 major RAPD types. The distribution of virulence genes in S. Gallinarum isolates was examined by Southern hybridization. All tested isolates had the invasion gene, invA, the virulence plasmid gene, spvB, and the S. Enteritidis fimbrial gene, sefC. The distribution of virulence genes among S. Gallinarum isolates did not correlate with any specific RAPD type.

Bacterial Typing Techniques↗

Lactobacillus paracasei A survives gastrointestinal passage and affects the fecal microbiota of healthy infants.

This study focuses on the potentiality of a putative probiotic strain, Lactobacillus paracasei A, to survive gastrointestinal (GI) passage and modulate the resident microbiota of healthy infants. In a placebo-controlled study, 26 children aged 12-24 months received 100 g/day of either fermented milk containing strain A or pasteurized yogurt for four weeks. Fecal samples were analyzed before starting the administration, after 1, 3 and 4 weeks of consumption and after washout. The fate of strain A was followed by means of a newly developed PCR targeting a strain-specific genomic marker. The composition and dynamics of fecal microbial communities during the study were analyzed by culturing on selective media and by the PCR-denaturing gradient gel electrophoresis (DGGE) technique using universal and group-specific (Lactobacillus and Bifidobacterium) primers. The variation in enzymatic activities in infant feces during probiotic consumption was also analyzed. Strain A survived in fecal samples in most (92%) of the infants examined after 1 week of consumption, and temporarily dominated the intestinal Lactobacillus community. The administration of L. paracasei A led to a significant increment in the Lactobacillus population, while a moderate effect upon the main bacterial groups in the GI ecosystem was observed. Strain A also affected the diversity of the Lactobacillus and Bifidobacterium populations. The fecal bacterial structure of 1 - 2-year-old infants seems to combine neonate and adult-like features. The microbiota of these subjects promptly responded to probiotic consumption, later restoring the endogenous equilibrium.

Cultured Milk Products↗

Evaluation of performance of four genotypic methods for studying the genetic epidemiology of Aspergillus fumigatus isolates.

In the present investigation, 49 Aspergillus fumigatus isolates obtained from four nosocomial outbreaks were typed by Afut1 restriction fragment length polymorphism (RFLP) analysis and three PCR-based molecular typing methods: random amplified polymorphic DNA (RAPD) analysis, sequence-specific DNA primer (SSDP) analysis, and polymorphic microsatellite markers (PMM) analysis. The typing methods were evaluated with respect to discriminatory power (D), reproducibility, typeability, ease of use, and ease of interpretation to determine their performance and utility for outbreak and surveillance investigations. Afut1 RFLP analysis detected 40 types. Thirty types were observed by RAPD analysis. PMM analysis detected 39 allelic types, but SSDP analysis detected only 14 types. All four methods demonstrated 100% typeability. PMM and RFLP analyses had comparable high degrees of discriminatory power (D = 0.989 and 0.988, respectively). The discriminatory power of RAPD analysis was slightly lower (D = 0.971), whereas SSDP analysis had the lowest discriminatory power (D = 0.889). Overall, SSDP analysis was the easiest method to interpret and perform. The profiles obtained by PMM analysis were easier to interpret than those obtained by RFLP or RAPD analysis. Bands that differed in staining intensity or that were of low intensity were observed by RAPD analysis, making interpretation more difficult. The reproducibilities with repeated runs of the same DNA preparation or with different DNA preparations of the same strain were high for all the methods. A high degree of genetic variation was observed in the test population, but isolates were not always similarly divided by each method. Interpretation of band profiles requires understanding of the molecular mechanisms responsible for genetic alternations. PMM analysis and Afut1 RFLP analysis, or their combination, appear to provide the best overall discriminatory power, reproducibility, ease of interpretation, and ease of use. This investigation will aid in planning epidemiologic and surveillance studies of A. fumigatus.

Aspergillosis↗

Characterization of Penicillium roqueforti strains used as cheese starter cultures by RAPD typing.

Seventy-six strains of Penicillium roqueforti used as starter cultures for mould ripened blue cheeses have been analysed for their RAPD genotype by using three different primers. A comparison of the RAPD patterns within each primer group revealed that the genetic constitution of the strains was similar, as most of the strains showed very similar overall patterns. Despite these similarities with each primer, distinct RAPD genotype groups could be identified. With one of the primers, it was possible to detect two heteropolymorphic DNA regions resulting in 13 different groups. With the other two primers, three or four groups could be identified. Between the groups of the different primers marked correspondence with respect to strain distribution could be observed, indicating that the polymorphisms detected by the primers were not independent. The RAPD patterns were compared to the production of secondary metabolites. A correlation was observed between the RAPD patterns of all primers and the production of mycophenolic acid. In addition, one of the primer (ari1) was able to distinguish between P. roqueforti strains producing larger or smaller numbers of metabolites.

Cheese↗

DNA probes specific for the yeast species Debaryomyces hansenii: useful tools for rapid identification.

We developed a rapid and sensitive identification method for the halotolerant yeast Debaryomyces hansenii, based on the hybridization of species-specific sequences. These sequences were first identified in a survey of D. hansenii strains by random amplification of polymorphic DNA (RAPD) as giving conserved bands in all isolates tested. Two such conserved RAPD products, termed F01pro and M18pro, were cloned from the type strain CBS 767. The specificity of these probes was assessed by hybridizing them to DNA from various species of yeasts commonly found in cheese. F01pro and M18pro hybridized to the DNA of all D. hansenii var. hansenii tested, but not to DNA of other yeast species including the closely related strain of D. hansenii var. fabryii CBS 789. Hybridization patterns of F01pro and M18pro on digested genomic DNA of D. hansenii indicated that the sequences were repeated in the genome of all D. hansenii var. hansenii tested, and gave distinct polymorphic patterns. The single F01pro probe generated 11 different profiles for 24 strains by restriction fragment length polymorphism, using one restriction enzyme. F01pro represents a new type of repeated element found in fungi, useful for both identification and typing of D. hansenii and, together with M18pro, simplifies the study of this species in complex flora.

Cheese↗

Changes in population structure of the soilborne fungus Gaeumannomyces graminis var. tritici during continuous wheat cropping.

A method was developed to assess the genetic structure of Gaeumannomyces graminis var. tritici (Ggt) populations and test the hypothesis of an association between disease level in the field with changes in pathogen populations. A long-term wheat monoculture experiment, established since 1994, generated different take-all epidemics with varying the number of wheat crop successions in the 1999-2000 cropping season. Genetic polymorphism in Ggt populations was investigated over natural, local epidemics. Four populations of 30 isolates were isolated from necrotic wheat roots in a first, third, fourth, and sixth wheat crop in the same year. Each Ggt isolate was characterized with RAPD (Random Amplification Polymorphism DNA) markers and AFLP (Amplified Fragment Length Polymorphism) fingerprinting. Seventeen multilocus genotypes based on the combination of RAPD and AFLP markers were identified among all these populations. The 120 isolates were divided into two main groups, G1 and G2, according to bootstrap values higher than 86%, except for an unique isolate from the third wheat crop. Within each group, populations ranged between 93 and 100% similarity. Both groups included isolates collected from the first, third, fourth or sixth wheat crop. However, G1 group profiles dominated amongst isolates sampled in the first and the sixth wheat crops, whereas G2 group profiles largely dominated amongst isolates collected from the third and fourth wheat crops. Aggressiveness of group G2 (38%) was significantly greater than that of G1 (29.5%). These results suggest that changes in Ggt population structure occur during continuous wheat cropping. The distinction of two Ggt groups provides a simple basis for further spatio-temporal analysis of Ggt population during polyetic take-all decline.

Ascomycota↗

Strain variation and geographic endemism in Streptococcus iniae.

Twenty-six Israeli isolates of Streptococcus iniae from both marine and fresh/brackish water sources were compared with each other and with 9 foreign isolates. All the isolates were tentatively identified according to their biochemical profile. Direct sequencing of approximately 600 bp PCR products of the 16S rDNA confirmed their identification as S. iniae at the molecular level and revealed a new (one-nucleotide) variant among Israeli isolates, in addition to 2 variants that had been previously reported. Strain variation was further examined by subjecting the isolates to randomly amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) analyses. The RAPD method allowed separation of the isolates into only 2 groups, one including 5 Israeli fresh/brackish water isolates and one including all the other isolates. The AFLP method grouped the Israeli marine isolates into one homogeneous cluster, although they had been obtained in different years (1995 to 2001) from different species of fish, and from wild (Red Sea) as well as cultured (both Mediterranean and Red Sea) sources. The Israeli fresh/brackish water isolates and foreign isolates separated into distinct entities that clustered at generally high degrees of similarity. The distance between the clusters of the Israeli marine and fresh/brackish water isolates indicates that the S. iniae streptococcosis that has been afflicting the aquaculture industries in the 2 environments in recent years was caused by distinct strains. AFLP showed superior discriminative properties over RAPD in detecting intraspecific variation and proved to be an important tool for the characterization of S. iniae. A correlation between strain variation and geographic endemism was established.

Base Sequence↗

Influence of a proton pump inhibitor-based therapy on Helicobacter pylori strain selection.

The influence of the proton pump inhibitor lansoprazole on strain diversity in Helicobacter pylori infected patients was investigated. Multiple isolates of Helicobacter pylori obtained pre- and post-therapy from gastric antral and body biopsies in 22 patients were compared using the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) for analysis. Post-therapy strains exhibiting novel RAPD-profiles were found in 5 of 22 patients (4 of 11 patients treated with lansoprazole alone and 1 of 11 patients treated with lansoprazole plus amoxicillin). Proton pump inhibition may affect the microecology of the stomach by influencing the colonisation patterns of specific strains.

2-Pyridinylmethylsulfinylbenzimidazoles↗

Identification of microorganisms using random primed PCR.

The polymerase chain reaction has facilitated the use of molecular approaches in microbiology including new strategies for the rapid identification of micro-organisms. Approaches based on the use of random primers and standard conditions, allows characteristic DNA fingerprints to be generated from any micro-organism even in the absence of information about its DNA sequence. Different primers can be used to produce genus-specific, species-specific, or even strain-specific DNA fingerprints. This article covers the background to this strategy, describes three different approaches to generating DNA fingerprints using random primers, and provides experimental detail for one method, RAPD.

Bacterial Typing Techniques↗