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Author

Neil S. Jensen

Other affiliations: Agricultural Research Service
Bio: Neil S. Jensen is an academic researcher from United States Department of Agriculture. The author has contributed to research in topics: Serpulina hyodysenteriae & Serpulina innocens. The author has an hindex of 17, co-authored 21 publications receiving 1270 citations. Previous affiliations of Neil S. Jensen include Agricultural Research Service.

Papers
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Journal ArticleDOI
TL;DR: DNA-DNA relative reassociation experiments in which the S1 nuclease method was used revealed that intestinal spirochete strain P43/6/78T was related to, but was genetically distinct from, both S. hyodysenteriae B78T and S. innocens B256T, and it is proposed that strain P 43/ 6/78 should be designated as the type strain of a new species, Serpulina pilosicoli.
Abstract: Phenotypic and genetic traits of porcine intestinal spirochete strain P43/6/78T (= ATCC 51139T) (T = type strain), which is pathogenic and weakly beta-hemolytic, were determined in order to confirm the taxonomic position of this organism and its relationships to previously described species of intestinal spirochetes. In BHIS broth, P43/6/78T cells had a doubling time of 1 to 2 h and grew to a maximum cell density of 2 x 109 cells per ml at 37 to 42°C. They hydrolyzed hippurate, utilized D-glucose, D-fructose, sucrose, D-trehalose, D-galactose, D-mannose, maltose, N-acetyl-D-glucosamine, D-glucosamine, pyruvate, L-fucose, D-cellobiose, and D-ribose as growth substrates, and produced acetate, butyrate, ethanol, H2, and CO2 as metabolic products. They consumed substrate amounts of oxygen and had a G+C content (24.6 mol%) similar to that of Serpulina hyodysenteriae B78T (25.9 mol%). Phenotypic traits that could be used to distinguish strain P43/6/78T from S. hyodysenteriae and Serpulina innocens included its ultrastructural appearance (each strain P43/6/78T cell had 8 or 10 periplasmic flagella, with 4 or 5 flagella inserted at each end, and the cells were thinner and shorter and had more pointed ends than S. hyodysenteriae and S. innocens cells), its faster growth rate in liquid media, its hydrolysis of hippurate, its lack of β-glucosidase activity, and its metabolism of D-ribose. DNA-DNA relative reassociation experiments in which the S1 nuclease method was used revealed that P43/6/78T was related to, but was genetically distinct from, both S. hyodysenteriae B78T (level of sequence homology, 25 to 32%) and S. innocens B256T (level of sequence homology, 24 to 25%). These and previous results indicate that intestinal spirochete strain P43/6/78T represents a distinct Serpulina species. Therefore, we propose that strain P43/6/78 should be designated as the type strain of a new species, Serpulina pilosicoli.

236 citations

Journal ArticleDOI
TL;DR: Findings indicate that induced VSH-1 virions package DNA of S. hyodysenteriae are capable of transferring host genes between cells of that spirochete and are incapable of lytic growth on any of five intestinal spiroChete strains.
Abstract: Serpulina hyodysenteriae B204 cells treated with mitomycin (20 microg of mitomycin/ml of culture broth) lysed and released bacteriophages. Bacteriophage particles, precipitated by using polyethylene glycol and purified by CsC1 density gradient ultracentrifugation, had a buoyant density of 1.375 g/cm3 and consisted of a head (45-nm diameter) and an ultrastructurally simple (noncontractile) tail (64 by 9 nm) composed of at least 13 proteins with molecular masses ranging between 13 and 101 kDa. The purified bacteriophage has been designated VSH-1 (VSH for virus of S. hyodysenteriae). VSH-1 was incapable of lytic growth on any of five intestinal spirochete strains, representing three Serpulina species. VSH-1 nucleic acid was determined to be approximately 7.5 kb in size and to be linear, double-stranded DNA based on differential staining with acridine orange, DNase I sensitivity, electrophoretic mobility, and contour length as measured by electron microscopy. Phage DNA digested by the restriction enzymes SspI, AseI, EcoRV, and AflII gave electrophoretic banding patterns nearly identical to those of digested chromosomal DNA from S. hyodysenteriae. Additionally, VSH-1 DNA fragments hybridized with probes complementary to S. hyodysenteriae chromosomal genes nox and flaA1. When purified bacteriophages induced from cultures of S. hyodysenteriae A203 (deltaflaA1 593-762::cat) were added to growing cells of strain A216 (deltanox 438-760::kan), transductants (Cmr Kmr) were obtained at a frequency of 1.5 x l0(-6) per phage particle (enumerated by electron microscopy). These findings indicate that induced VSH-1 virions package DNA of S. hyodysenteriae and are capable of transferring host genes between cells of that spirochete. To our knowledge, this is the first report of genetic transduction of a spirochete.

135 citations

Journal ArticleDOI
TL;DR: The intestinal anaerobic spirochetes Treponema hyodysenteriae B78T, B204, B169, and A-1, TrepOnema innocens B256T and 4/71, TrePonema succinifaciens 6091T, and Trep onema bryantii RUS-1T were compared by performing DNA-DNA reassociation experiments, sodium dodecyl sulfate-polyacrylamide
Abstract: The intestinal anaerobic spirochetes Treponema hyodysenteriae B78T (T = type strain), B204, B169, and A-1, Treponema innocens B256T and 4/71, Treponema succinifaciens 6091T, and Treponema bryantii RUS-1T were compared by performing DNA-DNA reassociation experiments, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cell proteins, restriction endonuclease analysis of DNA, and 16S rRNA sequence analysis. DNA-DNA relative reassociation experiments in which the S1 nuclease method was used showed that T. hyodysenteriae B78T and B204 had 93% sequence homology with each other and approximately 40% sequence homology with T. innocens B256T and 4/71. Both T. hyodysenteriae B78T and T. innocens B256T exhibited negligible levels of DNA homology ( 96%) in electrophoretic profiles among T. hyodysenteriae strains, moderate levels of similarity (43 to 49%) between T. hyodysenteriae and T. innocens, and no detectable similarity between the profiles of either T. hyodysenteriae or T. innocens and those of T. succinifaciens, T. bryantii, and Escherichia coli. Restriction endonuclease analysis of DNA was not useful in assessing genetic relationships since there was heterogeneity even between strains of T. hyodysenteriae. Partial 16S rRNA sequences of the intestinal spirochetes were determined by using a modified Sanger method and were compared in order to evaluate the phylogenetic relationships among these and other spirochetes. The 16S rRNA sequences of T. hyodysenteriae B78T, B204, and A-1 were nearly identical (99.8 to 99.9% base sequence similarity). T. innocens B256T and 4/71 were closely related to the T. hyodysenteriae strains (99.4 and 99.0% similarity). Strains of T. hyodysenteriae and T. innocens exhibited low levels of 16S rRNA similarity (average, 76.5%) with T. pallidum, Borrelia burgdorferi, and various other spirochetes. The results of our investigations indicate that T. hyodysenteriae and T. innocens are distinct but related species of spirochetes. T. hyodysenteriae and T. innocens are only distantly related to T. pallidum, the type species of the genus Treponema, and to other spirochetes. Consequently, we propose that the species T. hyodysenteriae and T. innocens be transferred to a new genus, Serpula, gen. nov.

122 citations

Journal ArticleDOI
TL;DR: The NADH oxidase genes of 18 strains of intestinal spirochaetes were partially sequenced and a phenogram produced based on sequence dissimilarities was in good agreement with the current classification of species in the genus Serpulina, although an atypical strongly beta-haemolytic porcine strain appeared distinct from other members of this species.

102 citations

Journal ArticleDOI
TL;DR: Results indicate that chicken spirochaete strain C1T has many phenotypic properties common to Serpulina species and, based on DNA hybridization analysis, represents a unique SerpULina species.
Abstract: Strain C1T is an anaerobic spirochaete that causes intestinal disease in chickens. Multilocus enzyme electrophoresis analysis and 16S rRNA sequence comparisons have indicated that this spirochaete is a Serpulina strain. In these investigations, various phenotypic and genomic properties useful for establishing a taxonomic identity for strain C1T were studied. As determined by electron microscopy, cells of the spirochaete measured 8-11 x 0.22-0.34 mum and had a typical spirochaete ultrastructure. Each cell had 22-30 flagella. C1T cells formed weakly beta-haemolytic colonies on trypticase soy agar plates containing 5% bovine blood. The spirochaete reached maximum population densities of 10(9) cells ml-1 with a 2-4 h population doubling time in brain heart infusion broth containing 10% calf serum (BHIS broth). C1T cultures in BHIS broth were positive in tests for hippurate hydrolysis and negative for indole production. Glucosamine, N-acetyglucosamine, glucose, fructose, maltose and mannose were growth substrates for the spirochaete in heart infusion broth containing 7% calf serum (HS broth). During growth in HS broth beneath an O2/N2 (1:99) atmosphere, cells of the spirochaete consumed O2 and glucose and produced H2, CO2, acetate, butyrate and ethanol. Strain C1T DNA had a G+C content of 24.6 mol%. Based on DNA-DNA hybridization analyses, the DNA of strain C1T exhibited 24-39% relative reassociation with DNA of Serpulina hyodysenteriae, Serpulina innocens, Serpulina pilosicoli, Serpulina murdochii and Serpulina intermedia. These results indicate that chicken spirochaete strain C1T has many phenotypic properties common to Serpulina species and, based on DNA hybridization analysis, represents a unique Serpulina species. For this new species the name Serpulina alvinipulli is proposed, for which the type strain is C1T (= ATCC 51933T).

98 citations


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Journal ArticleDOI
TL;DR: An analysis of aligned sequences of the four nuclear and two mitochondrial rRNA genes identified regions of these genes that are likely to be useful to address phylogenetic problems over a wide range of levels of divergence.
Abstract: Ribosomal DNA (rDNA) sequences have been aligned and compared in a number of living organisms, and this approach has provided a wealth of information about phylogenetic relationships. Studies of rDNA sequences have been used to infer phylogenetic history across a very broad spectrum, from studies among the basal lineages of life to relationships among closely related species and populations. The reasons for the systematic versatility of rDNA include the numerous rates of evolution among different regions of rDNA (both among and within genes), the presence of many copies of most rDNA sequences per genome, and the pattern of concerted evolution that occurs among repeated copies. These features facilitate the analysis of rDNA by direct RNA sequencing, DNA sequencing (either by cloning or amplification), and restriction enzyme methodologies. Constraints imposed by secondary structure of rRNA and concerted evolution need to be considered in phylogenetic analyses, but these constraints do not appear to impede seriously the usefulness of rDNA. An analysis of aligned sequences of the four nuclear and two mitochondrial rRNA genes identified regions of these genes that are likely to be useful to address phylogenetic problems over a wide range of levels of divergence. In general, the small subunit nuclear sequences appear to be best for elucidating Precambrian divergences, the large subunit nuclear sequences for Paleozoic and Mesozoic divergences, and the organellar sequences of both subunits for Cenozoic divergences. Primer sequences were designed for use in amplifying the entire nuclear rDNA array in 15 sections by use of the polymerase chain reaction; these "universal" primers complement previously described primers for the mitochondrial rRNA genes. Pairs of primers can be selected in conjunction with the analysis of divergence of the rRNA genes to address systematic problems throughout the hierarchy of life.

2,439 citations

Journal ArticleDOI
TL;DR: Although 16S rRNA sequences can be used routinely to distinguish and establish relationships between genera and well-resolved species, very recently diverged species may not be recognizable.
Abstract: 16S rRNA (genes coding for rRNA) sequence comparisons were conducted with the following three psychrophilic strains: Bacillus globisporus W25T (T = type strain) and Bacillus psychrophilus W16AT, and W5. These strains exhibited more than 99.5% sequence identity and within experimental uncertainty could be regarded as identical. Their close taxonomic relationship was further documented by phenotypic similarities. In contrast, previously published DNA-DNA hybridization results have convincingly established that these strains do not belong to the same species if current standards are used. These results emphasize the important point that effective identity of 16S rRNA sequences is not necessarily a sufficient criterion to guarantee species identity. Thus, although 16S rRNA sequences can be used routinely to distinguish and establish relationships between genera and well-resolved species, very recently diverged species may not be recognizable.

1,342 citations

Journal ArticleDOI
TL;DR: The concept of the resistome is discussed, examples of HGT of clinically relevant ARGs are provided and an overview of the current knowledge of the contributions the various HGT mechanisms make to the spread of antibiotic resistance is presented.
Abstract: The emergence and spread of antibiotic resistance among pathogenic bacteria has been a rising problem for public health in recent decades. It is becoming increasingly recognized that not only antibiotic resistance genes (ARGs) encountered in clinical pathogens are of relevance, but rather, all pathogenic, commensal as well as environmental bacteria-and also mobile genetic elements and bacteriophages-form a reservoir of ARGs (the resistome) from which pathogenic bacteria can acquire resistance via horizontal gene transfer (HGT). HGT has caused antibiotic resistance to spread from commensal and environmental species to pathogenic ones, as has been shown for some clinically important ARGs. Of the three canonical mechanisms of HGT, conjugation is thought to have the greatest influence on the dissemination of ARGs. While transformation and transduction are deemed less important, recent discoveries suggest their role may be larger than previously thought. Understanding the extent of the resistome and how its mobilization to pathogenic bacteria takes place is essential for efforts to control the dissemination of these genes. Here, we will discuss the concept of the resistome, provide examples of HGT of clinically relevant ARGs and present an overview of the current knowledge of the contributions the various HGT mechanisms make to the spread of antibiotic resistance.

996 citations

Journal ArticleDOI
TL;DR: In this paper, the evolution of integrated virus genomes (prophages) is analyzed using nucleotide sequence analysis, and it is shown that some prophages can lie in residence for very long times, perhaps millions of years, and that recombination events have occurred between related Prophages that reside at different locations in a bacterium's genome.
Abstract: Epigraph There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. Mark Twain 1883 Life on the Mississippi Summary Bacterial genome nucleotide sequences are being completed at a rapid and increasing rate. Integrated virus genomes (prophages) are common in such genomes. Fifty-one of the 82 such genomes published to date carry prophages, and these contain 230 recognizable putative prophages. Prophages can constitute as much as 10–20% of a bacterium's genome and are major contributors to differences between individuals within species. Many of these prophages appear to be defective and are in a state of mutational decay. Prophages, including defective ones, can contribute important biological properties to their bacterial hosts. Therefore, if we are to comprehend bacterial genomes fully, it is essential that we are able to recognize accurately and understand their prophages from nucleotide sequence analysis. Analysis of the evolution of prophages can shed light on the evolution of both bacteriophages and their hosts. Comparison of the Rac prophages in the sequenced genomes of three Escherichia coli strains and the Pnm prophages in two Neisseria meningitidis strains suggests that some prophages can lie in residence for very long times, perhaps millions of years, and that recombination events have occurred between related prophages that reside at different locations in a bacterium's genome. In addition, many genes in defective prophages remain functional, so a significant portion of the temperate bacteriophage gene pool resides in prophages.

822 citations

Journal ArticleDOI
TL;DR: The discussion in the present article centers on interactions among bacterial species and how these interactions contribute to the development of plaque and ultimately to the formation of periodontopathogenic communities.
Abstract: Studies from the 1960s indicated that increased microbial diversity and a succession in the predominant bacterial species in plaque correlate with the appearance of gingival inflammation and the development of periodontal disease. In the past few years, molecular characterization of the microflora found in various sites of the oral cavity of different subjects has detected around 700 bacterial species or phylotypes (1, 63, 93). Some of these species are considered commensal and a positive feature of our healthy microflora, while others are considered pathogenic. The colonization of pathogenic bacteria is probably dependent upon the interaction of pathogens and commensal organisms. The clinical relevance and periodontal microbial ecology of these bacteria have been presented in an outstanding, comprehensive review (101). The discussion in the present article centers on interactions among bacterial species and how these interactions contribute to the development of plaque and ultimately to the formation of periodontopathogenic communities. Interactions among human oral bacteria are integral to the development of plaque. From the early stages of colonization to the formation of mature supragingival and subgingival plaque, a diverse array of bacterial species colonizes into densely populated communities. Interactions among different bacterial cell types are proposed to drive the maturation of plaque. These interactions occur at several levels, including physical contact, metabolic exchange, small-signal-molecule-mediated communication and exchange of genetic material. A principal feature of human oral bacteria is their ability to interact by coaggregation with other oral bacteria (48). Coaggregation is defined as the specific cell-to-cell recognition that occurs between genetically distinct cell types. Each cell type bears on its surface one or more types of coaggregation mediator, which are called adhesins and receptors (described below). The adhesins and receptors confer a particular set of coaggregation properties. Coaggregation partnerships are central to the development of biodiversity in supragingival and subgingival plaque. Coaggregations effect changes in populations, from low diversity in initial communities of supragingival plaque to high diversity in subgingival plaque. This article will provide an overview of the physical and metabolic interactions that occur among the oral microflora in the context of plaque development.

657 citations