Biomedical subjects

Michael L Paustian

Publications and source records attributed to Michael L Paustian.

15 recordsLinked to original sources

PubMed2006

Comparative transcriptional analysis of human macrophages exposed to animal and human isolates of Mycobacterium avium subspecies paratuberculosis with diverse genotypes.

Mycobacterium avium subsp. paratuberculosis is the causative agent of Johne's disease in animals and has been hypothesized to be associated with Crohn's disease in humans. Recently, M. avium subsp. paratuberculosis isolates recovered from Crohn's disease patients were shown to have limited diversity, implying the existence of human disease-associated genotypes and strain sharing with animals (A. H. Ghadiali et al., J. Clin. Microbiol. 42:5345-5348, 2004). To explore whether these genotypic differences or similarities among human and animal isolates translated to functionally significant attributes such as variance in host preference and/or difference in magnitude of infections, we performed a global scale analysis of M. avium subsp. paratuberculosis isolates that were representative of different genotypes and host species using DNA microarrays. Genome-wide characterization of the transcriptional changes was carried out using a human monocytic cell line (THP-1 cells) in response to different genotypes of M. avium subsp. paratuberculosis isolates recovered from various hosts. We identified several differentially expressed genes during early intracellular infection, including those involved in common canonical pathways such as NF-kappaB, interleukin-6 (IL-6), mitogen-activated protein kinase/extracellular signal-regulated kinase, and Jun N-terminal protein kinase signaling, as well as genes involved in T helper type 1 (Th1) responses (such as CCL5 ligand) and those that encode several proinflammatory cytokines and chemokine receptors. The cattle and human isolates of M. avium subsp. paratuberculosis, regardless of their short sequence repeat (SSR) genotype, induced similar global gene expression patterns in THP-1 cells. They differentially regulated genes necessary for cell survival without causing major alterations in proinflammatory genes. In contrast, the sheep isolates representing diverse SSR genotypes closely resembled the global gene expression pattern of an M. avium subsp. avium isolate, and they significantly up-regulated proinflammatory genes related to IL-6, T-cell receptor, B-cell receptor, and death receptor signaling within THP-1 cells. Additionally, we demonstrated consistency among infecting genotypes of M. avium subsp. paratuberculosis isolated from diverse hosts [cattle (n=2), human (n=3), sheep (n=2), and bison (n=1)] in quantitative reverse transcription-PCR analysis of seven differentially expressed genes. While the levels of expression induced by the bison isolate were different compared with cattle or human isolates, they followed the common anti-inflammatory, antiapoptotic trend. Our data suggest that the macrophage responses to M. avium subsp. paratuberculosis isolates from cattle and human sources, regardless of genotype, follow a common theme of anti-inflammatory responses, an attribute likely associated with successful infection and persistence. However, these expression patterns differ significantly from those in THP-1 cells infected with sheep isolates of M. avium subsp. paratuberculosis or the M. avium subsp. avium isolate. These data provide a transcriptional basis for a variety of pathophysiological changes observed during early stages of infection by different strains of M. avium subsp. paratuberculosis, a first step in understanding trait-allele association in this economically important disease.

Animals↗

PubMed2006

Effects of temperature on gene expression patterns in Leptospira interrogans serovar Lai as assessed by whole-genome microarrays.

Leptospirosis is an important zoonosis of worldwide distribution. Humans become infected via exposure to pathogenic Leptospira spp. from infected animals or contaminated water or soil. The availability of genome sequences for Leptospira interrogans, serovars Lai and Copenhageni, has opened up opportunities to examine global transcription profiles using microarray technology. Temperature is a key environmental factor known to affect leptospiral protein expression. Leptospira spp. can grow in artificial media at a range of temperatures reflecting conditions found in the environment and the mammalian host. Therefore, transcriptional changes were compared between cultures grown at 20 degrees C, 30 degrees C, 37 degrees C, and 39 degrees C to represent ambient temperatures in the environment, growth under laboratory conditions, and temperatures in healthy and febrile hosts. Data from direct pairwise comparisons of the four temperatures were consolidated to examine transcriptional changes at two generalized biological conditions representing mammalian physiological temperatures (37 degrees C and 39 degrees C) versus environmental temperatures (20 degrees C and 30 degrees C). Additionally, cultures grown at 30 degrees C then shifted overnight to 37 degrees C were compared with those grown long-term at 30 degrees C and 37 degrees C to identify genes potentially expressed in the early stages of infection. Comparison of data sets from physiological versus environmental experiments with upshift experiments provided novel insights into possible transcriptional changes at different stages of infection. Changes included differential expression of chemotaxis and motility genes, signal transduction systems, and genes encoding proteins involved in alteration of the outer membrane. These findings indicate that temperature is an important factor regulating expression of proteins that facilitate invasion and establishment of disease.

Environment↗

PubMed2006

The ability of Mycobacterium avium subsp. paratuberculosis to enter bovine epithelial cells is influenced by preexposure to a hyperosmolar environment and intracellular passage in bovine mammary epithelial cells.

Mycobacterium avium subsp. paratuberculosis is the cause of Johne's disease in cattle and other ruminants. M. avium subsp. paratuberculosis infection of the bovine host is not well understood; however, it is assumed that crossing the bovine intestinal mucosa is important in order for M. avium subsp. paratuberculosis to establish infection. To examine the ability of M. avium subsp. paratuberculosis to infect bovine epithelial cells in vitro, Madin-Darby bovine kidney (MDBK) epithelial cells were exposed to M. avium subsp. paratuberculosis. It was observed that bacteria can establish infection and replicate within MDBK cells. M. avium subsp. paratuberculosis also has been reported to infect mammary tissue and milk, and we showed that M. avium subsp. paratuberculosis infects bovine mammary epithelial cells (MAC-T cell line). Using polarized MAC-T cell monolayers, it was also determined that M. avium subsp. paratuberculosis crosses apical and basolateral surfaces with approximately the same degree of efficiency. Because M. avium subsp. paratuberculosis can be delivered to the naïve host by milk, it was investigated whether incubation of M. avium subsp. paratuberculosis with milk has an effect on invasion of MDBK cells. M. avium subsp. paratuberculosis exposed to milk entered epithelial cells with greater efficiency than M. avium subsp. paratuberculosis exposed to broth medium or water (P < 0.01). Growth of M. avium subsp. paratuberculosis within MAC-T cells also resulted in augmented ability to subsequently infect bovine MDBK cells (P < 0.001). Microarray analysis of intracellular M. avium subsp. paratuberculosis RNA indicates the increased transcription of genes which might be associated with an invasive phenotype.

Animals↗

PubMed2006

Genomic comparison of Mycobacterium avium subsp. paratuberculosis sheep and cattle strains by microarray hybridization.

Microarray-based comparisons of three Mycobacterium avium subsp. paratuberculosis isolates, including one sheep strain and two cattle strains, identified three large genomic deletions in the sheep strain, totaling 29,208 bp and involving 24 open reading frames. These deletions may help explain some of the differences in pathogenicity and host specificity observed between the cattle and sheep strains of Mycobacterium avium subsp. paratuberculosis.

Animals↗

PubMed2006

Lateral gene transfer in Mycobacterium avium subspecies paratuberculosis.

Lateral gene transfer is an integral part of genome evolution in most bacteria. Bacteria can readily change the contents of their genomes to increase adaptability to ever-changing surroundings and to generate evolutionary novelty. Here, we report instances of lateral gene transfer in Mycobacterium avium subsp. paratuberculosis, a pathogenic bacteria that causes Johne's disease in cattle. A set of 275 genes are identified that are likely to have been recently acquired by lateral gene transfer. The analysis indicated that 53 of the 275 genes were acquired after the divergence of M. avium subsp. paratuberculosis from M. avium subsp. avium, whereas the remaining 222 genes were possibly acquired by a common ancestor of M. avium subsp. paratuberculosis and M. avium subsp. avium after its divergence from the ancestor of M. tuberculosis complex. Many of the acquired genes were from proteobacteria or soil dwelling actinobacteria. Prominent among the predicted laterally transferred genes is the gene rsbR, a possible regulator of sigma factor, and the genes designated MAP3614 and MAP3757, which are similar to genes in eukaryotes. The results of this study suggest that like most other bacteria, lateral gene transfers seem to be a common feature in M. avium subsp. paratuberculosis and that the proteobacteria contribute most of these genetic exchanges.

Gene Transfer, Horizontal↗

PubMed2006

Identification of diagnostic proteins in Mycobacterium avium subspecies paratuberculosis by a whole genome analysis approach.

Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is an economically significant veterinary pathogen that causes Johne's disease in cattle and sheep. There is a critical need for improved diagnostic tests to detect M. paratuberculosis infection in these animals. As with many other animal diseases, efforts need to be concentrated on the development of simple, rapid, noninvasive tests that can be performed by veterinarians or animal producers without expensive laboratory equipment. With the genome sequence of M. paratuberculosis now complete, we have taken a different strategy to identify novel proteins that are present uniquely in M. paratuberculosis and are antigenic in the context of infected cattle. Through a whole genome comparison of M. paratuberculosis with other sequenced mycobacterial genomes, we identified a collection of more than 90 genes that are present uniquely in M. paratuberculosis. This list has been further trimmed to 39 after amplification using polymerase chain reaction of unique genes using the genomic deoxyribonucleic acid template from several mycobacterial species and isolates. A selection of the remaining genes has been cloned and expressed in Escherichia coli and purified by affinity chromatography. Successfully purified proteins were analyzed using sera from rabbits immunized with M. paratuberculosis. Furthermore, to identify antigens in the context of disease, sera from cattle with Johne's disease as well as healthy control cattle are used in immunoassays. Using this methodology, we identified the first protein antigens specific to M. paratuberculosis.

Animals↗

PubMed2005

Characterization of the pheromone response of the Enterococcus faecalis conjugative plasmid pCF10: complete sequence and comparative analysis of the transcriptional and phenotypic responses of pCF10-containing cells to pheromone induction.

The sex pheromone plasmids in Enterococcus faecalis are one of the most efficient conjugative plasmid transfer systems known in bacteria. Plasmid transfer rates can reach or exceed 10(-1) transconjugants per donor in vivo and under laboratory conditions. We report the completion of the DNA sequence of plasmid pCF10 and the analysis of the transcription profile of plasmid genes, relative to conjugative transfer ability following pheromone induction. These experiments employed a mini-microarray containing all 57 open reading frames of pCF10 and a set of selected chromosomal genes. A clear peak of transcription activity was observed 30 to 60 min after pheromone addition, with transcription subsiding 2 h after pheromone induction. The transcript activity correlated with the ability of donor cells to transfer pCF10 to recipient cells. Remarkably, aggregation substance (Asc10, encoded by the prgB gene) was present on the cell surface for a long period of time after pheromone-induced transcription of prgB and plasmid transfer ability had ceased. This observation could have relevance for the virulence of E. faecalis.

Chromosome Mapping↗

PubMed2005

Comparative genomic hybridizations reveal genetic regions within the Mycobacterium avium complex that are divergent from Mycobacterium avium subsp. paratuberculosis isolates.

Mycobacterium avium subsp. paratuberculosis is genetically similar to other members of the Mycobacterium avium complex (MAC), some of which are nonpathogenic and widespread in the environment. We have utilized an M. avium subsp. paratuberculosis whole-genome microarray representing over 95% of the predicted coding sequences to examine the genetic conservation among 10 M. avium subsp. paratuberculosis isolates, two isolates each of Mycobacterium avium subsp. silvaticum and Mycobacterium avium subsp. avium, and a single isolate each of both Mycobacterium intracellulare and Mycobacterium smegmatis. Genomic DNA from each isolate was competitively hybridized with DNA from M. avium subsp. paratuberculosis K10, and open reading frames (ORFs) were classified as present, divergent, or intermediate. None of the M. avium subsp. paratuberculosis isolates had ORFs classified as divergent. The two M. avium subsp. avium isolates had 210 and 135 divergent ORFs, while the two M. avium subsp. silvaticum isolates examined had 77 and 103 divergent ORFs. Similarly, 130 divergent ORFs were identified in M. intracellulare. A set of 97 ORFs were classified as divergent or intermediate in all of the nonparatuberculosis MAC isolates tested. Many of these ORFs are clustered together on the genome in regions with relatively low average GC content compared with the entire genome and contain mobile genetic elements. One of these regions of sequence divergence contained genes homologous to a mammalian cell entry (mce) operon. Our results indicate that closely related MAC mycobacteria can be distinguished from M. avium subsp. paratuberculosis by multiple clusters of divergent ORFs.

Conserved Sequence↗

PubMed2004

Application of the genome sequence to address concerns that Mycobacterium avium subspecies paratuberculosis might be a foodborne pathogen.

Johne's disease, a chronic inflammatory disease caused by infection with Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis), is one of the most prevalent and costly diseases of dairy cattle worldwide. This ruminant pathogen is closely related to the ubiquitous animal and human pathogen Mycobacterium avium subspecies avium (M. avium), confounding the development of specific diagnostic reagents. Exacerbating this problem further is that most existing microbiological, serological, and immunologic assays for the identification of infected animals are inadequate. This is primarily because of the slow-growing nature of the organism, genetic intractability and the previous lack of information on M. paratuberculosis subspecies-specific genes or proteins that may enable the development of specific and sensitive assays. New detection tools are critically needed to definitively answer questions surrounding M. paratuberculosis as a foodborne pathogen as well as aid in determining if it is a contributing factor in Crohn's disease. Thus, the recent characterization of the complete genome sequence of M. paratuberculosis in our laboratories has been a major step forward in meeting this need. We have performed studies that utilize genomic information for the identification of specific DNA sequences and protein antigens in M. paratuberculosis. Based on a preliminary in silico comparison of the M. paratuberculosis genome sequence with that of M. avium, we have now identified at least 35 novel coding sequences that are unique to M. paratuberculosis. These in silico data were then confirmed and expanded by PCR amplification analysis with DNA from several species and isolates of mycobacteria. Finally, these unique sequences have been incorporated into an antigen discovery project that may allow reliable detection of the bacterium in antigen-based diagnostic tests. Application of these new tools in addressing foodborne related issues of M. paratuberculosis is discussed.

Animals↗

PubMed2004

Expression and immunogenicity of proteins encoded by sequences specific to Mycobacterium avium subsp. paratuberculosis.

The development of immunoassays specific for the diagnosis of Johne's disease in cattle requires antigens specific to Mycobacterium avium subsp. paratuberculosis. However, because of genetic similarity to other mycobacteria comprising the M. avium complex, no such antigens have been found. Through a comparative genomics approach, 21 potential coding sequences of M. avium subsp. paratuberculosis that are not represented in any other mycobacterial species tested (n = 9) were previously identified (J. P. Bannantine, E. Baechler, Q. Zhang, L. Li, and V. Kapur, J. Clin. Microbiol. 40:1303-1310, 2002). Here we describe the cloning, heterologous expression, and antigenic analysis of these M. avium subsp. paratuberculosis-specific sequences in Escherichia coli. Nucleotide sequences representing each unique predicted coding region were amplified and cloned into two different E. coli expression vectors encoding polyhistidine or maltose binding protein (MBP) affinity purification tags. All 21 of the MBP fusion proteins were successfully purified under denaturing conditions and were evaluated in immunoblotting studies with sera from rabbits and mice immunized with M. avium subsp. paratuberculosis. These studies showed that 5 of the 21 gene products are produced by M. avium subsp. paratuberculosis and are antigenic. Immunoblot analysis with a panel of sera from 9 healthy cattle and 10 cattle with clinical disease shows that the same five M. avium subsp. paratuberculosis proteins are also detected within the context of infection. Collectively, these studies have used a genomic approach to identify novel M. avium subsp. paratuberculosis antigens that are not present in any other mycobacteria. These findings may have a major impact on improved diagnostics for Johne's disease.

Animals↗

PubMed2004

Characterization of novel coding sequences specific to Mycobacterium avium subsp. paratuberculosis: implications for diagnosis of Johne's Disease.

Mycobacterium avium subsp. paratuberculosis is the causative agent of Johne's Disease, an economically important intestinal ailment of ruminants. Due to the considerable genetic and serologic cross-reactivity with closely related and ubiquitous members of the M. avium complex, a species-specific method for the serological diagnosis of Johne's disease is unavailable. Computational and PCR-based analysis of the complete genome sequence of M. avium subsp. paratuberculosis led to the identification of 13 open reading frames with no identifiable homologs. One of these sequences is a putative insertion element present in six copies on the M. avium subsp. paratuberculosis genome. These novel M. avium subsp. paratuberculosis genes were cloned into Escherichia coli expression vectors, and nine were successfully expressed as recombinant fusion proteins. Five of these proteins were purified in sufficient amounts to allow immunoblot analyses of their reactivity with sera from naturally infected cattle as well as mice and rabbits exposed to M. avium subsp. paratuberculosis. Fusion proteins representing MAP0862, MAP3732c, and MAP2963c were recognized by nearly all of the sera tested, including those from cattle in the clinical stages of disease. Notably, further analysis of the protein encoded by MAP0862 showed that it reacted with sera from additional infected cattle but not with sera from uninfected control animals. The fusion product of MAP0860c did not react with any of the sera tested, while the remaining four proteins were variably recognized by sera from M. avium subsp. paratuberculosis-infected cattle. Collectively, the results of this study demonstrate the utility of genomic data to identify potential diagnostic sequences.

Animals↗

PubMed2002

Characterization and expression analysis of Staphylococcus aureus pathogenicity island 3. Implications for the evolution of staphylococcal pathogenicity islands.

We describe the complete sequence of the 15.9-kb staphylococcal pathogenicity island 3 encoding staphylococcal enterotoxin serotypes B, K, and Q. The island, which meets the generally accepted definition of pathogenicity islands, contains 24 open reading frames potentially encoding proteins of more than 50 amino acids, including an apparently functional integrase. The element is bordered by two 17-bp direct repeats identical to those found flanking staphylococcal pathogenicity island 1. The island has extensive regions of homology to previously described pathogenicity islands, particularly staphylococcal pathogenicity islands 1 and bov. The expression of 22 of the 24 open reading frames contained on staphylococcal pathogenicity island 3 was detected either in vitro during growth in a laboratory medium or serum or in vivo in a rabbit model of toxic shock syndrome using DNA microarrays. The effect of oxygen tension on staphylococcal pathogenicity island 3 gene expression was also examined. By comparison with the known staphylococcal pathogenicity islands in the context of gene expression described here, we propose a model of pathogenicity island origin and evolution involving specialized transduction events and addition, deletion, or recombination of pathogenicity island "modules."

Animals↗

PubMed2002

Transcriptional response of Pasteurella multocida to nutrient limitation.

Bacteria often encounter environments where nutrient availability is limited, and they must adapt accordingly. To identify Pasteurella multocida genes that are differentially expressed during nutrient limitation, we utilized whole-genome microarrays to compare levels of gene expression during growth in rich and minimal media. Our analysis showed that the levels of expression of a total of 669 genes, representing approximately one-third of the genome, were detectably altered over the course of the experiment. A large number (n = 439) of genes, including those involved in energy metabolism, transport, protein synthesis, and binding, were expressed at higher levels in rich medium, suggesting that, upon exposure to a rich environment, P. multocida immediately begins to turn on many energy-intensive biosynthetic pathways or, conversely, turns these genes off when it is exposed to a nutrient-deficient environment. Genes with increased expression in minimal medium (n = 230) included those encoding amino acid biosynthesis and transport systems, outer membrane proteins, and heat shock proteins. Importantly, our analysis also identified a large number (n = 164) of genes with unknown functions whose expression was altered during nutrient limitation. Overall, the results of our study show that a wide repertoire of genes, many of which have yet to be functionally classified, undergo transcriptional regulation in P. multocida in response to growth in minimal medium and provide a strong foundation to investigate the transcriptional response of this multispecies pathogen to growth in a nutrient-limited environment.

Arginine↗

PubMed2002

Transcriptional response of Pasteurella multocida to defined iron sources.

Pasteurella multocida was grown in iron-free chemically defined medium supplemented with hemoglobin, transferrin, ferritin, and ferric citrate as iron sources. Whole-genome DNA microarrays were used to monitor global gene expression over seven time points after the addition of the defined iron source to the medium. This resulted in a set of data containing over 338,000 gene expression observations. On average, 12% of P. multocida genes were differentially expressed under any single condition. A majority of these genes encoded P. multocida proteins that were involved in either transport and binding or were annotated as hypothetical proteins. Several trends are evident when the data from different iron sources are compared. In general, only two genes (ptsN and sapD) were expressed at elevated levels under all of the conditions tested. The results also show that genes with increased expression in the presence of hemoglobin did not respond to transferrin or ferritin as an iron source. Correspondingly, genes with increased expression in the transferrin and ferritin experiments were expressed at reduced levels when hemoglobin was supplied as the sole iron source. Finally, the data show that genes that were most responsive to the presence of ferric citrate did not follow a trend similar to that of the other iron sources, suggesting that different pathways respond to inorganic or organic sources of iron in P. multocida. Taken together, our results demonstrate that unique subsets of P. multocida genes are expressed in response to different iron sources and that many of these genes have yet to be functionally characterized.

Bacterial Proteins↗

PubMed2002

Repression of the Staphylococcus aureus accessory gene regulator in serum and in vivo.

Subgenomic DNA microarrays were employed to evaluate the expression of the accessory gene regulator (agr locus) as well as multiple virulence-associated genes in Staphylococcus aureus. Gene expression was examined during growth of S. aureus in vitro in standard laboratory medium and rabbit serum and in vivo in subcutaneous chambers implanted in either nonimmune rabbits or rabbits immunized with staphylococcal enterotoxin B. Expression of RNAIII, the effector molecule of the agr locus, was dramatically repressed in serum and in vivo, despite the increased expression of secreted virulence factors sufficient to cause toxic shock syndrome (TSS) in the animals. Statistical analysis and clustering of virulence genes based on their expression profiles in the various experimental conditions demonstrated no positive correlation between the expression of agr and any staphylococcal virulence factors examined. Disruption of the agr locus had only a minimal effect on the expression in vivo of the virulence factors examined. An effect of immunization on the expression of agr and virulence factors was also observed. These results suggest that agr activation is not necessary for development of staphylococcal TSS and that regulatory circuits responding to the in vivo environment override agr activity.

Animals↗