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PubMed2001

Characterization of maize cytochrome P450 monooxygenases induced in response to safeners and bacterial pathogens.

Plants use a diverse array of cytochrome P450 monooxygenases in their biosynthetic and detoxification pathways. To determine the extent to which various maize P450s are induced in response to chemical inducers, such as naphthalic anhydride (NA), triasulfuron (T), phenobarbital, and bacterial pathogens (Erwinia stuartii, Acidovorax avenae), we have analyzed the response patterns of seven P450 transcripts after treatment of seedlings with these inducers. Each of these P450 transcripts has distinct developmental, tissue-specific, and chemical cues regulating their expression even when they encode P450s within the same biosynthetic pathway. Most notably, the CYP71C1 and CYP71C3 transcripts, encoding P450s in the DIMBOA biosynthetic pathway, are induced to the same level in response to wounding and NA treatment of younger seedlings and differentially in response to NA/T treatment of younger seedlings and NA and NA/T treatment of older seedlings. NA and T induce expression of both CYP92A1 and CYP72A5 transcripts in older seedling shoots, whereas phenobarbital induces CYP92A1 expression in older seedling shoots and highly induces CYP72A5 expression in young and older seedling roots. Expressed sequence tag (EST) 6c06b11 transcripts, encoding an undefined P450 activity, are highly induced in seedling shoots infected with bacterial pathogens.

Amino Acid Sequence↗

PubMed2004

Animal models in the analysis of Candida host-pathogen interactions.

An increasingly diverse array of clinically relevant animal models of candidiasis have been established that mimic both the immune perturbations of the host and tissue-specific features of candidiasis in humans. Cause-and-effect analysis of Candida host-pathogen interactions using these animal models has made a quantum leap forward in the genomic era, with the concurrent construction of C. albicans mutants with targeted mutations of putative virulence factors, the application of microarrays and other emerging technologies to comprehensively assess C. albicans gene expression in vivo, and construction of transgenic and knockout mice to simulate specific host immunodeficiencies. The opportunity to combine these powerful tools will yield an unprecedented wealth of new information on the molecular and cellular pathogenesis of candidiasis.

Animals↗

PubMed1992

Molecular economy and antibody function: the evolution of a Protecton.

The humoral immune response protects against a very large array of pathogens which attempt to escape immune recognition by changing the antigens they display. When looked at from the point of two competing sets of DNA (i.e., the pathogens vs. the host), there is a vastly larger pool of mutating pathogen DNA than in, say, a mouse. The stratagems that allow a tiny fraction of the mouse's genome to effectively compete with a hugely diverse array of pathogens is analyzed in terms of how antibody functions and how the immune system avoids such pitfalls as self-recognition and destruction. This review is a more general description of a lengthy series of papers which detailed the evolution of the Protecton. Starting from the obvious, that is the concentration-dependence of antibody function, it is apparent that the functional antibody repertoire must be relatively small if a sufficient concentration of specific antibody is to be produced in time to arrest the growth of pathogens and eventually eliminate them. Thus, commonly quoted estimates of antibody repertoires in the range from greater than 10(10) to "complete" (infinite?) must be seriously in error. Other well known "facts", such as D-diversity, and B cell signaling by receptor aggregation are also shown to be lacking in biological commonsense.

Animals↗

PubMed1995

Heterogeneity of rat encephalitogenic T cells elicited by variants of the myelin basic protein (68-86) peptide.

By immunizing Lewis rats with myelin basic protein (MBP) peptide variants derived from the major encephalitogenic epitope of guinea pig (MBP(68-88) and then isolating encephalitogenic T cells from these animals, we demonstrated that the variant peptides do not elicit the same encephalitogenic T cell subsets as those induced by the wild-type peptide or by intact MBP. Rather, the pathogenic T cells differed in clonal composition as reflected by their heterogeneous responses to a panel of variant peptides and by their T cell receptor usage. Thus, molecules mimicking the MBP(68-88) autoantigen can elicit pathogenic T cell subsets without necessarily cross-reacting with T cells specific for the original autoantigen. This suggests that a more clonally diverse group of pathogenic T cells might be involved in EAE than has been apparent from studies with intact MBP or its unaltered peptides.

Amino Acid Sequence↗

PubMed1987

The evolution of antibiotic production and public health problems.

Antibiotic evolution is closely paralleled by the evolution of bacterial resistance. Prior to wide usage of penicillin G, resistance to beta-lactam antibiotics as a consequence of beta-lactamase production had been recognized, and has been an increasing clinical problem ever since. Discovery of antibiotics other than beta-lactams, such as macrolides, tetracyclines and aminoglycosides, has also resulted in the eventual selection of bacteria resistant to these agents. Synthesis of novel beta-lactam derivatives from 6-APA, such as methicillin and isoxazolyl penicillins, resistant to staphylococcal beta-lactamase, overcame the clinical problem of penicillin-resistant S. aureus. Likewise, the isolation of cephamycins and monobactams, and further exploitation of the cephalosporin nucleus, led to the development of derivatives which display a high degree of stability to a wide range of gram-positive and gram-negative bacterial beta-lactamases, thus rendering organisms producing these enzymes susceptible to these agents. Analogous modification of the penicillin nucleus, to give 6 alpha-substituted penicillins, also resulted in derivatives with exceptional stability to beta-lactamases. An alternative approach to the problem of beta-lactamase was the isolation or synthesis of substances able to inhibit the activity of enzymes, thus protecting the unstable beta-lactams from inactivation by beta-lactamase. In this way the activity of beta-lactamase-labile agents was effectively restored against a wide range of beta-lactamase-producing bacterial pathogens. The wide diversity of new antibacterial agents, together with an increasing knowledge and understanding of mechanisms of resistance, indicates that further advances against resistant bacterial pathogens is ensured.

Anti-Bacterial Agents↗

PubMed2000

Epitope mimics and determinant spreading: pathways to autoimmunity.

Infectious microorganisms have evolved molecules which mimic the host in order to aid in their undetected propagation. In response, mammalian hosts have evolved a highly diverse immune repertoire designed to eradicate rapidly changing pathogens. The generation of diversity in the immune repertoire results in potentially damaging self cross-reactivities which require multiple regulatory controls to keep autoreactive lymphocytes in check. Here, we review how molecular mimicry at the T cell level might be important in the development of systemic autoimmunity.

Animals↗

PubMed2004

Iron gathering by zoopathogenic fungi.

Iron is a metal required by most microorganisms and is prominently used in the transfer of electrons during metabolism. The gathering of iron is, then, an essential process and its fulfillment becomes a crucial pathogenetic event for zoopathogenic fungi. Iron is rather unavailable because it occurs on the earth's surface in its insoluble ferric form in oxides and hydroxides. In the infected host iron is bound to proteins such as transferrin and ferritin. Solubilization of ferric iron is the major problem confronting microorganisms. This process is achieved by two major mechanisms: ferric reduction and siderophore utilization. Ferric reductase is frequently accompanied by a copper oxidase transport system. There is one example of direct ferric iron transport apparently without prior reduction. Ferric reduction may also be accomplished by low molecular mass compounds. Some fungi have evolved a process of iron acquisition involving the synthesis of iron-gathering compounds called siderophores. Even those fungi that do not synthesize siderophores have developed permeases for transport of such compounds formed by other organisms. Fungi can also reductively release iron from siderophores and transport the ferrous iron often by the copper oxidase transport system. There is a great diversity of iron-gathering mechanisms expressed by pathogenic fungi and such diversity may be found even in a single species.

Ferritins↗

PubMed2002

[Hospital-acquired respiratory infection].

Hospital-acquired respiratory infections are the most common and important complication in patients in hospital. Understanding the patients' conditions and backgrounds is the most important issue to predict or control the infections. There are so many pathogens not only bacteria but also mycobacteriums fungi, viruses, etc, which cause the hospital respiratory infection, therefore the diagnostic approach should be actively and diversity. Strong and pathogen targeted treatments are needed to control the infection. It's also important to complete the treatment as soon as possible with an appropriate evaluation, to prevent the increase of resistant pathogens or superinfections.

Anti-Bacterial Agents↗

PubMed2003

Molecular variability of sunflower downy mildew, Plasmopara halstedii, from different continents.

Downy mildew of sunflower (Helianthus annuus L.), caused by the pathogen Plasmopara halstedii, is a potentially devastating disease. Seventy-seven isolates of P. halstedii collected in twelve countries from four continents were investigated for RAPD polymorphism with 21 primers. The study led to a binary matrix, which was subjected to various complementary analyses. This is the first report on the international genetic diversity of the pathogen. Similarity indices ranged from 89% to 100%. Neither a consensus unweighted pair group method with arithmetic means (UPGMA) tree constructed after bootstrap resampling of markers nor a principal component analysis based on distance matrix revealed very consistent clusterings of the isolates, and groups did not fit race or geographical origins. Phylogenies were probably obscured by limited diversity. Analysis of molecular variance (AMOVA) and Nei's genetic diversity statistics gave similar conclusions. Most of the genetic diversity was attributable to individual differences. The most differentiated races also had the lowest within-diversity indices, which suggest that they appeared recently with strong bottleneck effects. Our analyses suggest that this pathogen is probably homothallic or has an asexual mode of reproduction and that gene flow among countries can occur through commercial exchanges. Knowledge of the downy mildew populations' structure at the international level will help to devise strategies for controlling this potentially devastating disease.

DNA↗

PubMed2004

Diversity and antagonistic potential of bacteria associated with bryophytes from nutrient-poor habitats of the Baltic Sea Coast.

Very little is known about the interaction of bryophytes with bacteria. Therefore, we analyzed bacteria associated with three bryophyte species, Tortula ruralis, Aulacomnium palustre, and Sphagnum rubellum, which represent typical moss species of three nutrient-poor plant communities at the southern Baltic Sea coast in Germany. By use of two cultivation-independent techniques, denaturing gradient gel electrophoresis and single-strand conformation polymorphism analysis of the 16S ribosomal DNA, a high degree of moss specificity was found for associated bacterial communities. This specificity could be further evidenced by a cultivation-dependent approach for the following parameters: (i) plate counts of bacteria on R2A medium, (ii) proportion of antagonistic isolates, (iii) antagonistic activity as well as spectrum against pathogens, and (iv) diversity and richness of antagonistic isolates. The proportion of isolates with antagonistic activity against the pathogenic model fungus Verticillium dahliae was highest for S. rubellum (31%), followed by A. palustre (17%) and T. ruralis (5%). A high percentage (99%) of moss-associated antagonistic bacteria produced antifungal compounds. The high recovery of antagonistic isolates strongly suggests that bryophytes represent an ecological niche which harbors a diverse and hitherto largely uncharacterized microbial population with yet unknown and untapped potential biotechnological applications, e.g., for biological control of plant pathogens.

Antibiosis↗

PubMed2004

Gene-for-gene disease resistance: bridging insect pest and pathogen defense.

Active plant defense, also known as gene-for-gene resistance, is triggered when a plant resistance (R) gene recognizes the intrusion of a specific insect pest or pathogen. Activation of plant defense includes an array of physiological and transcriptional reprogramming. During the past decade, a large number of plant R genes that confer resistance to diverse group of pathogens have been cloned from a number of plant species. Based on predicted protein structures, these genes are classified into a small number of groups, indicating that structurally related R genes recognize phylogenetically distinct pathogens. An extreme example is the tomato Mi-1 gene, which confers resistance to potato aphid (Macrosiphum euphorbiae), whitefly (Bemisia tabaci), and root-knot nematodes (Meloidogyne spp.). While Mi-1 remains the only cloned insect R gene, there is evidence that gene-for-gene type of plant defense against piercing-sucking insects exists in a number of plant species.

Animals↗

PubMed2006

[Molecular typing of Listeria monocytogenes isolated from clinical and food samples].

INTRODUCTION: Listeria monocytogenes is an emergent foodborne pathogen acquired by the ingestion of contaminated food. This bacterium causes a disease called listeriosis, whose mortality rate world wide is around 20% to 30%, reaching up to 80% in cases of neonatal infections. The random amplified polymorphic DNA technique allows different isolates to be distinguished and characterized at the molecular level, which can provide useful information about the diversity of this pathogen in Colombia. OBJECTIVE: To molecularly characterize different L. monocytogenes isolates from food and clinical samples using this technique to determine possible relationships among these two origins. MATERIALS AND METHODS: Thirty eight L. monocytogenes isolates were analyzed; 22 from human clinical samples and 16 from food processing plants and food using two 10bp primers (HLW74, Arbitrary). The data were analyzed using Quantity One and SYN-TAX software. RESULTS: A high percentage of polymorphism was detected with both primers (HLWL-74, 81.81%; Arbitrary, 85.71%). Two major lineages were found, which were divided into four major clusters (A, B C and D) and great genetic diversity was observed. Most of the clinical isolates were grouped within the same cluster, and were more distantly related to the food isolates. CONCLUSION: The results of this study demonstrate a high degree of genetic diversity of DNA polymorphisms among the L. monocytogenes isolates circulating in Colombia, which could reflect phenotypic and pathogenic differences in these isolates.

Bacterial Typing Techniques↗

PubMed1998

Intragenic recombination and diversifying selection contribute to the evolution of downy mildew resistance at the RPP8 locus of Arabidopsis.

Pathogen resistance (R) genes of the NBS-LRR class (for nucleotide binding site and leucine-rich repeat) are found in many plant species and confer resistance to a diverse spectrum of pathogens. Little is known about the mechanisms that drive NBS-LRR gene evolution in the host-pathogen arms race. We cloned the RPP8 gene (for resistance to Peronospora parasitica) and compared the structure of alleles at this locus in resistant Landsberg erecta (Ler-0) and susceptible Columbia (Col-0) accessions. RPP8-Ler encodes an NBS-LRR protein with a putative N-terminal leucine zipper and is more closely related to previously cloned R genes that confer resistance to bacterial pathogens than it is to other known RPP genes. The RPP8 haplotype in Ler-0 contains the functional RPP8-Ler gene and a nonfunctional homolog, RPH8A. In contrast, the rpp8 locus in Col-0 contains a single chimeric gene, which was likely derived from unequal crossing over between RPP8-Ler and RPH8A ancestors within a Ler-like haplotype. Sequence divergence among RPP8 family members has been accelerated by positive selection on the putative ligand binding region in the LRRs. These observations indicate that NBS-LRR molecular evolution is driven by the same mechanisms that promote rapid sequence diversification among other genes involved in non-self-recognition.

Alleles↗

PubMed2005

Chips and SNPs, bugs and thugs: a molecular sleuthing perspective.

Recent events both here and abroad have focused attention on the need for ensuring a safe and secure food supply. Although much has been written about the potential of particular select agents in bioterrorism, we must consider seriously the more mundane pathogens, especially those that have been implicated previously in foodborne outbreaks of human disease, as possible agents of bioterrorism. Given their evolutionary history, the enteric pathogens are more diverse than agents such as Bacillus anthracis, Francisella tularensis, or Yersinia pestis. This greater diversity, however, is a double-edged sword; although diversity affords the opportunity for unequivocal identification of an organism without the need for whole-genome sequencing, the same diversity can confound definitive forensic identification if boundaries are not well defined. Here, we discuss molecular approaches used for the identification of Salmonella enterica, Escherichia coli, and Shigella spp. and viral pathogens and discuss the utility of these approaches to the field of microbial molecular forensics.

Bacteria↗

PubMed2006

Early days: genomics and human responses to infection.

DNA microarray-based gene transcript-profiling of the responses of primates to infection has begun to yield new insights into host-pathogen interactions; this approach, however, remains plagued by challenges and complexities that have yet to be adequately addressed. The rapidly changing nature over time of acute infectious diseases in a host, and the genetic diversity of microbial pathogens present unique problems for the design and interpretation of functional-genomic studies in this field. In addition, there are the more common problems related to heterogeneity within clinical samples, the complex, non-standardized confounding variables associated with human subjects and the complexities posed by the analysis and validation of highly parallel data. Whereas various approaches have been developed to address each of these issues, there are significant limitations that remain to be overcome. The resolution of these problems should lead to a better understanding of the dialogue between the host and pathogen.

Animals↗

PubMed2002

Resistance and susceptibility of plants to fungal pathogens.

Plants are under continuous threat of infection by pathogens endowed with diverse strategies to colonize their host. Comprehensive biochemical and genetic approaches are now starting to reveal the complex signaling pathways that mediate plant disease resistance. Initiation of defense signaling often involves specific recognition of invading pathogens by the products of specialized host resistance (R) genes. Potential resistance signaling components have been identified by mutational analyses to be required for specific resistance in the model Arabidopsis and some crop species. Strikingly, many of the components share similarity to that of innate immune systems in animals. Evidence is also accumulating that plant pathogens have a number of ways to evade host defenses during the early stages of infection, similar to animal pathogens. These strategies are becoming much better understood in a number of plant-pathogen interactions. In this review, we focus on the current knowledge of host factors that control plant resistance and susceptibility to fungal pathogens. The knowledge accumulated in these studies will serve a fundamental basis for combating diseases in strategic molecular agriculture.

Fungal Proteins↗

PubMed2025

Genome-wide mapping of cAMP receptor protein binding in enteroaggregative Escherichia coli reveals targeting of virulence-associated genes.

Bacterial pathogens employ a diverse array of virulence factors to colonize and subsequently elicit disease in their host. These factors are often subject to extensive regulation at the transcriptional level to ensure that their expression is timely. Although many pathogens use bespoke transcription factors that primarily target virulence genes, global transcription factors also sometimes play a role in controlling these genes. Enteroaggregative Escherichia coli (EAEC) is a significant cause of watery and mucoid diarrhoea globally. The organism colonizes the small intestine before producing toxins that elicit disease, using a multitude of virulence factors that are encoded both chromosomally and on virulence plasmids. In this work, we have studied the cAMP receptor protein (CRP), a well-characterized bacterial global transcription factor, focusing on its role in the pathogenicity of the prototype EAEC strain 042. We show that, although most functional CRP binding sites on the chromosome are conserved between E. coli K-12 and 042, CRP has been co-opted to couple the expression of some virulence genes to the nutritional state of the cell. We report novel mechanisms for CRP-dependent regulation of genes whose products contribute to the maturation of a bacterial antibiotic, export of a polysaccharide capsule and production of a putative adhesin.

Escherichia coli↗

PubMed2004

Multipathogen oligonucleotide microarray for environmental and biodefense applications.

Food-borne pathogens are a major health problem. The large and diverse number of microbial pathogens and their virulence factors has fueled interest in technologies capable of detecting multiple pathogens and multiple virulence factors simultaneously. Some of these pathogens and their toxins have potential use as bioweapons. DNA microarray technology allows the simultaneous analysis of thousands of sequences of DNA in a relatively short time, making it appropriate for biodefense and for public health uses. This paper describes methods for using DNA microarrays to detect and analyze microbial pathogens. The FDA-1 microarray was developed for the simultaneous detection of several food-borne pathogens and their virulence factors including Listeria spp., Campylobacter spp., Staphylococcus aureus enterotoxin genes and Clostridium perfringens toxin genes. Three elements were incorporated to increase confidence in the microarray detection system: redundancy of genes, redundancy of oligonucleotide probes (oligoprobes) for a specific gene, and quality control oligoprobes to monitor array spotting and target DNA hybridization. These elements enhance the reliability of detection and reduce the chance of erroneous results due to the genetic variability of microbes or technical problems with the microarray. The results presented demonstrate the potential of oligonucleotide microarrays for detection of environmental and biodefense relevant microbial pathogens.

Bacteria↗