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PubMed2004

Bacterial probiotics induce an immune response in the honey bee (Hymenoptera: Apidae).

To explore immune system activation in the honey bee, Apis mellifera L., larvae of four ages were exposed through feeding to spores of a natural pathogen, Paenibacillus larvae larvae, to cells of a diverse set of related nonpathogenic bacteria, and to bacterial coat components. These larvae were then assayed for RNA levels of genes encoding two antibacterial peptides, abaecin and defensin. Larvae exposed to either P. l. larvae or a mix of nonpathogenic bacteria showed high RNA levels for the abaecin gene relative to controls. First instars responded significantly to the presence of the nonpathogenic mix within 12 h after exposure, a time when they remain highly susceptible to bacterial invasion. This response was sustained for two successive instars, eventually becoming 21-fold higher in larvae exposed to probiotic spores versus control larvae. The mixture of nonpathogenic bacteria is therefore presented as a potential surrogate for assaying the immune responses of different honey bee lineages. It also is proposed that nonpathogenic bacteria can be used as a probiotic to enhance honey bee immunity, helping bee larvae, and other life stages, survive attacks from pathogens in the field.

Animals↗

PubMed2006

Virus counterdefense: diverse strategies for evading the RNA-silencing immunity.

Viruses are obligate, intracellular pathogens that must manipulate and exploit host molecular mechanisms to prosper in the hostile cellular environment. Here we review the strategies used by viruses to evade the immunity controlled by 21- to 26-nt small RNAs. Viral suppressors of RNA silencing (VSRs) are encoded by genetically diverse viruses infecting plants, invertebrates, and vertebrates. VSRs target key steps in the small RNA pathways by inhibiting small RNA production, sequestering small RNAs, or preventing short- and long-distance spread of RNA silencing. However, although VSRs are required for infection, explicit data demonstrating a role of silencing suppression in virus infection are available only for a few VSRs. A subset of VSRs bind double-stranded RNA, but a distinct protein fold is revealed for each of the four VSRs examined. We propose that VSR families are evolved independently as a viral adaptation to immunity. Unresolved issues on the role of RNA silencing in virus-host interactions are highlighted.

Gene Amplification↗

PubMed1993

The sialidase superfamily and its spread by horizontal gene transfer.

Sialidases (neuraminidases, EC 3.2.1.18) belong to a class of glycosyl hydrolases that release terminal N-acylneuraminate (sialic acid) residues from glycoproteins, glycolipids, and polysaccharides. These enzymes are common in animals of the deuterostomate lineage (Echinodermata through Mammalia) and also in diverse microorganisms that mostly exist as animal commensals or pathogens. Sialidases, and their sialyl substrates, appear to be absent from plants and most other metazoans. Even among bacteria, sialidase is found irregularly so that related species or even strains of one species differ in this property. This unusual phylogenetic distribution makes sialidases interesting for evolutionary studies. The biochemical diversity among bacterial sialidases does not indicate close relationships. However, at the molecular level, homologies are detectable, supporting the hypothesis of a common sialidase origin and thus of a sialidase superfamily. Some findings indicate that sialidase genes were recently transferred via phages among bacteria. The proposal of a sialidase origin in higher animals is suggested by the presence of apparently homologous enzymes in this kingdom, supporting the idea that some microbes may have acquired the genetic information during association with their animal hosts.

Amino Acid Sequence↗

PubMed2003

Genome evolution in an insect cell: distinct features of an ant-bacterial partnership.

Bacteria that live exclusively within eukaryotic host cells include not only well-known pathogens, but also obligate mutualists, many of which occur in diverse insect groups such as aphids, psyllids, tsetse flies, and the ant genus Camponotus (Buchner, 1965; Douglas, 1998; Moran and Telang, 1998; Baumann et al., 2000; Moran and Baumann, 2000). In contrast to intracellular pathogens, these primary (P) endosymbionts of insects are required for the survival and reproduction of the host, exist within specialized host cells called bacteriocytes, and undergo stable maternal transmission through host lineages (Buchner, 1965; McLean and Houk, 1973). Due to their long-term host associations and close phylogenetic relationship with well-characterized enterobacteria (Fig. 1), P-endosymbionts of insects are ideal model systems to examine changes in genome content and architecture that occur in the context of beneficial, intracellular associations. Since these bacteria have not been cultured outside of the host cell, they are difficult to study with traditional genetic or physiological approaches. However, in recent years, molecular and computational approaches have provided important insights into their genetic diversity and ecological significance. This review describes some recent insights into the evolutionary genetics of obligate insect-bacteria symbioses, with a particular focus on an intriguing association between the bacterial endosymbiont Blochmannia and its ant hosts.

Animals↗

PubMed2004

Functional and structural diversity in the Als protein family of Candida albicans.

The human fungal pathogen Candida albicans colonizes and invades a wide range of host tissues. Adherence to host constituents plays an important role in this process. Two members of the C. albicans Als protein family (Als1p and Als5p) have been found to mediate adherence; however, the functions of other members of this family are unknown. In this study, members of the ALS gene family were cloned and expressed in Saccharomyces cerevisiae to characterize their individual functions. Distinct Als proteins conferred distinct adherence profiles to diverse host substrates. Using chimeric Als5p-Als6p constructs, the regions mediating substrate-specific adherence were localized to the N-terminal domains in Als proteins. Interestingly, a subset of Als proteins also mediated endothelial cell invasion, a previously unknown function of this family. Consistent with these results, homology modeling revealed that Als members contain anti-parallel beta-sheet motifs interposed by extended regions, homologous to adhesins or invasins of the immunoglobulin superfamily. This finding was confirmed using circular dichroism and Fourier transform infrared spectrometric analysis of the N-terminal domain of Als1p. Specific regions of amino acid hypervariability were found among the N-terminal domains of Als proteins, and energy-based models predicted similarities and differences in the N-terminal domains that probably govern the diverse function of Als family members. Collectively, these results indicate that the structural and functional diversity within the Als family provides C. albicans with an array of cell wall proteins capable of recognizing and interacting with a wide range of host constituents during infection.

Amino Acid Motifs↗

PubMed2004

Multilocus microsatellite typing system for Penicillium marneffei reveals spatially structured populations.

For eukaryotic pathogens that have low levels of genetic variation, multilocus microsatellite typing (MLMT) offers an accurate and reproducible method of characterizing genetic diversity. Here, we describe the application of an MLMT system to the emerging pathogenic fungus Penicillium marneffei. Isolates used for this study were those held in the culture collections of the Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands, and the Chiang Mai University Department of Microbiology, Chang Mai, Thailand. High genetic diversity and extensive spatial structure were observed among clinical isolates, with the geographical area of origin for each isolate strongly correlating with the occurrence of two deeply divided clades. Within each clade, multilocus linkage associations were highly significant and could be explained by genetically differentiated populations or by an exclusively clonal reproductive mode, or both. Our results show that southeast Asian penicilliosis is caused by a fungus with a complex population genetic structure. Furthermore, this MLMT system generates digital data that can be easily queried against a centrally held database via the internet (http://pmarneffei.multilocus.net/); this provides a powerful epidemiological tool for analyzing the underlying parameters that are responsible for the emergence of P. marneffei in human immunodeficiency virus-positive populations.

AIDS-Related Opportunistic Infections↗

PubMed2004

Multilocus sequence typing scheme for bacteria of the Bacillus cereus group.

In this study we developed a multilocus sequence typing (MLST) scheme for bacteria of the Bacillus cereus group. This group, which includes the species B. cereus, B. thuringiensis, B. weihenstephanensis, and B. anthracis, is known to be genetically very diverse. It is also very important because it comprises pathogenic organisms as well as bacteria with industrial applications. The MLST system was established by using 77 strains having various origins, including humans, animals, food, and soil. A total of 67 of these strains had been analyzed previously by multilocus enzyme electrophoresis, and they were selected to represent the genetic diversity of this group of bacteria. Primers were designed for conserved regions of housekeeping genes, and 330- to 504-bp internal fragments of seven such genes, adk, ccpA, ftsA, glpT, pyrE, recF, and sucC, were sequenced for all strains. The number of alleles at individual loci ranged from 25 to 40, and a total of 53 allelic profiles or sequence types (STs) were distinguished. Analysis of the sequence data showed that the population structure of the B. cereus group is weakly clonal. In particular, all five B. anthracis isolates analyzed had the same ST. The MLST scheme which we developed has a high level of resolution and should be an excellent tool for studying the population structure and epidemiology of the B. cereus group.

Alleles↗

PubMed1996

Phylogenetic analysis of Streptomyces spp. causing potato scab based on 16S rRNA sequences.

The complete 16S rRNA sequences of 12 strains of Streptomyces spp., including potato scab pathogens, were determined. Among the strains of Streptomyces scabies that were isolated from diverse geographical areas and differed in melanoid pigment production, either no difference or one difference in sequence was observed. The sequence of S. scabies was most similar to the sequences of Streptomyces diastatochromogenes, Streptomyces bottropensis, and Streptomyces neyagawaensis, which belong to the Diastatochromogenes group. The levels of similarity of the 16S rRNA sequences of Streptomyces acidiscabies and S. scabies were almost the same as the levels of similarity between S. acidiscabies and other Streptomyces strains. Streptomyces sp. strain 91-Sy-13, which was isolated in Japan from potato scab and belongs to a distinct species on the basis of phenotypic characteristics and DNA relatedness, exhibited lower levels of 16S rRNA sequence similarity with other potato scab pathogens, as well as other Streptomyces species. The phylogenetic tree constructed on the basis of 16S rRNA sequence data showed that the Streptomyces spp. that cause potato scab composed unique branches. The results of our phylogenetic analysis based on complete 16S rRNA sequences confirmed the lack of close relationships among Streptomyces spp. that cause potato scab. Our findings suggest that potato scab is caused by phylogenetically diverse Streptomyces species and that the pathogenicities of these organisms developed independently.

Base Sequence↗

PubMed1990

Localization of and immune response to the lipid-modified azurin of the pathogenic Neisseria.

The development of vaccines to prevent Neisseria infections has been impeded by antigenic diversity of most Neisseria surface components. The lipid-modified azurin (Laz), one of two distinct surface proteins recognized by the H.8 monoclonal antibody, is present in all pathogenic Neisseria. The mature protein has two domains; one contains an H.8 epitope and the other has extensive homology to azurins, a class of bacterial copper-binding proteins. The cellular location of Laz and the serum immune response to Lax were examined in patients with disseminated Neisseria infections. The data demonstrated that Laz is probably contained in the Neisseria outer membrane, although unlike most outer membrane proteins it is Sarkosyl soluble. By probing recombinant bacteriophages encoding the H.8 and azurin domains of Laz, results showed that whereas the H.8 epitope is immunogenic in patients with disseminated Neisseria infections, the azurin domain of Laz plays little role in eliciting an antibody response in these patients.

Antibodies, Bacterial↗

PubMed2026

Ribotyping for Accurate Identification of Infectious Bacteria in Animal-Derived Foods and Laboratory Samples: Implications for Human Health.

Ribotyping is a molecular typing approach based on ribosomal RNA (rRNA) gene sequences for the identification and characterization of bacterial strains. This review aims to evaluate the effectiveness of ribotyping in the identification of infectious bacteria in animal-derived foods and veterinary samples. A narrative literature review was conducted using major scientific databases, including PubMed, Scopus, Google Scholar, and Web of Science, covering studies published to 2025. Relevant articles were selected based on their focus on ribotyping methodologies (e.g., RFLP-, PCR-, and automated ribotyping) and their applications in food safety, veterinary microbiology, and zoonotic disease investigations. The findings indicate that ribotyping has been widely applied for epidemiological investigations, source tracking, and characterization of foodborne and zoonotic pathogens. These approaches have contributed to understanding bacterial diversity and monitoring antibiotic resistance patterns in animal populations and related food products. However, compared with high-resolution molecular techniques such as whole genome sequencing (WGS), ribotyping demonstrates lower discriminatory power and limited resolution for fine-scale epidemiological analysis. Despite these limitations, ribotyping remains a useful, accessible, and cost-effective tool in certain laboratory and surveillance settings, particularly where advanced genomic technologies are not readily available. Overall, integrating ribotyping with newer genomic approaches can enhance the monitoring and control of infectious bacteria, thereby supporting animal health, food safety, and public health outcomes.

animal-derived foods↗

PubMed1991

Molecular basis of Mycoplasma surface antigenic variation: a novel set of divergent genes undergo spontaneous mutation of periodic coding regions and 5' regulatory sequences.

Antigenic diversity is generated in the wall-less pathogen Mycoplasma hyorhinis by combinatorial expression and phase variation of multiple, size-variant membrane surface lipoproteins (Vlps). The unusual structural basis for Vlp variation was revealed in a cluster of related but divergent vlp genes, vlpA, vlpB and vlpC, which occur as single chromosomal copies. These encode conserved N-terminal domains for membrane insertion and lipoprotein processing, but divergent external domains undergoing size variation by loss or gain of repetitive intragenic coding sequences while retaining a motif with distinctive charge distribution. Genetic analysis of phenotypically switched isogenic lineages representing ON or OFF expression states of Vlp products ruled out chromosomal rearrangement or frameshift mutations as mechanisms for Vlp phase variation. However, highly conserved vlp promoter regions contain a tract of contiguous A residues immediately upstream of the -10 box which is subject to frequent mutations altering its length in exact correspondence with the ON and OFF phase states of specific genes. This suggests a mechanism of transcriptional control regulating high frequency phase variation and random combinatorial expression of Vlps. The multiple levels of diversity embodied in the vlp gene cluster represents a novel adaptive capability particularly suited for this class of wall-less microbe.

Amino Acid Sequence↗

PubMed2003

Molecular biology and immunology for clinicians 25: defense collagens.

The adaptive immune response specializes in reacting efficiently and rapidly with protein antigens. Many pathogens and host cells are coated with carbohydrates (more about lipid antigens and the response thereto in a future installment of this series). The carbohydrate arrays on pathogens are remarkable for their relative lack of diversity, remarkable conservation, and how different they are from the carbohydrates found on mammalian cells. Thus, they represent excellent targets for the innate immune response, which is characterized by limited effector molecule heterogeneity. Defense collagens are a class of innate immune response recognition proteins targeting these common carbohydrate motifs, a class you may not have encountered previously. These invariant germ-line encoded proteins are not produced as a specific response to a particular antigen. Nonetheless, they too have an antigen-binding site, called the carbohydrate recognition domain with the other end of the molecule (made up of collagen-like domains) devoted to the transmission of biologically relevant information, analogous with the antibody molecule's Fc component, but this is where the similarities end. Defense collagens have been broadly viewed as an "anti-antibody," broadly similar in structure and function. Despite the fact that they are germline-encoded and do not have individual antigen specificity, their phylogenetic longevity and durability prove the value of defense collagens in maintaining the host. On the basis of emerging studies, they may play important roles in the defense against many pathogens and in the pathogenesis of rheumatologic and other diseases. Thus, they are good targets for studies to better understand our diseases and to craft therapeutic manipulations in the future.

Journal Article↗

PubMed1994

A single TCR antagonist peptide inhibits experimental allergic encephalomyelitis mediated by a diverse T cell repertoire.

Previously, six T cell clones, which are specific for an encephalitogenic determinant of myelin proteolipid protein (PLP) peptide residues 139 to 151 (HSLGKWLGHPDKF), were derived from SJL mice and shown to use diverse TCR genes. To design TCR antagonist peptides that could interfere with the activation of these clones in vitro and inhibit experimental allergic encephalomyelitis (EAE) in vivo, we first determined the TCR and MHC contact residues of the encephalitogenic peptide. The analysis indicated that residues 144 (tryptophan) and 147 (histidine) were the TCR binding sites and that residues 145 (leucine) and 148 (proline) were important for MHC class II (IAs) binding. On the basis of this information, a peptide analogue (leucine 144/arginine 147), in which both of the major TCR contact residues were substituted, was synthesized. This analogue acts as a TCR antagonist for the panel of PLP 139-151-specific T cell clones, does not cause EAE by itself, blocks the induction of disease by the native 139-151 peptide, and prevents clinical disease progression if administered at the first signs of disease. Thus, although multiple TCR genes are used by PLP 139-151-specific clones, a single peptide analogue can interfere with the disease process. This approach should be feasible for designing peptide analogues that can be tested for therapeutic efficacy in human autoimmune diseases in which the pathogenic Ags are known and TCR use is diverse.

Amino Acid Sequence↗

PubMed2006

The role of immune-mediated apparent competition in genetically diverse malaria infections.

Competitive interactions between coinfecting genotypes of the same pathogen can impose selection on virulence, but the direction of this selection depends on the mechanisms behind the interactions. Here, we investigate how host immune responses contribute to competition between clones in mixed infections of the rodent malaria parasite Plasmodium chabaudi. We studied single and mixed infections of a virulent and an avirulent clone and compared the extent of competition in immunodeficient and immunocompetent mice (nude mice and T cell-reconstituted nude mice, respectively). In immunocompetent mice, the avirulent clone suffered more from competition than did the virulent clone. The competitive suppression of the avirulent clone was alleviated in immunodeficient mice. Moreover, the relative density of the avirulent clone in mixed infections was higher in immunodeficient than in immunocompetent mice. We conclude that immune-mediated interactions contributed to competitive suppression of the avirulent clone, although other mechanisms, presumably competition for resources such as red blood cells, must also be important. Because only the avirulent clone suffered from immune-mediated competition, this mechanism should contribute to selection for increased virulence in mixed infections in this host-parasite system. As far as we are aware, this is the first direct experimental evidence of immune-mediated apparent competition in any host-parasite system.

Animals↗

PubMed2002

Cas, Fak and Pyk2 function in diverse signaling cascades to promote Yersinia uptake.

The interplay between pathogen-encoded virulence factors and host cell signaling networks is critical for both the establishment and clearance of microbial infections. Yersinia uptake into host cells serves as an in vitro model for exploring how host cells respond to Yersinia adherence. In this study, we provide insight into the molecular nature and regulation of signaling networks that contribute to the uptake process. Using a reconstitution approach in Fak(-/-) fibroblasts, we have been able to specifically address the interplay between Fak, Cas and Pyk2 in this process. We show that both Fak and Cas play roles in the Yersinia uptake process and that Cas can function in a novel pathway that is independent of Fak. Fak-dependent Yersinia uptake does not appear to involve Cas-Crk signaling. By contrast, Cas-mediated uptake in the absence of Fak requires Crk as well as the protein tyrosine kinases Pyk2 and Src. In spite of these differences, the requirement for Rac1 activity is a common feature of both pathways. Furthermore, blocking the function of either Fak or Cas induces similar morphological defects in Yersinia internalization, which are manifested by incomplete membrane protrusive activity that is consistent with an inhibition of Rac1 activity. Pyk2 also functions in Yersinia uptake by macrophages, which are physiologically important for clearing Yersinia infections. Taken together, these data provide new insight into the host cellular signaling networks that are initiated upon infection with Y. pseudotuberculosis. Importantly, these findings also contribute to a better understanding of other cellular processes that involve actin remodeling, including the host response to other microbial pathogens, cell adhesion and migration.

Animals↗

PubMed2002

Comparison of the quantity and quality of the microbiological content of sludge in countries with low and high content of pathogens.

The parasites present in the residual sludge generate by the diverse treatment processes of residual water vary, depending on the socioeconomic and epidemiological conditions of different communities. And although data exist at the global level regarding the microbiological quality of sludge, these data are practically nonexistent in developing countries. Therefore, this project compares the content of the four principal groups of parasites in residual sludge from the United States and Mexico. The marked differences between the orders of magnitude found in the two countries (coliphages 10(3)-10(6) and 1.3 x 10(5) PFU/gTS, fecal coliforms 10(7)-10(10) and 10(7), Salmonella typhi 10(6)-10(8) and 10(3) MPN/gTS, Giardia lamblia 10(2)-10(4) and 10(2) cysts/gTS and helminth ova from 73-177 and <1 to 10 viable HO/gTS, respectively) will permit proposing real, effective and economical stabilization processes (undoubtedly different from those of industrialized countries), and will thus take advantage of the benefits represented by the reuse and disposal of sludge, in addition to developing regulations in agreement with the conditions of each region.

Animals↗

PubMed2006

Diversity of Calliphoridae (Diptera) in Brazil's Tinguá Biological Reserve.

The Calliphoridae are flies of great ecological, medical and sanitary importance because they are decomposers of organic matter, mechanical vectors of pathogenic agents, and causers of myiasis. This paper attempts to ascertain the diversity of Calliphoridae in the Tinguá Biological Reserve and correlate meteorological data (temperature, relative humidity of the air, and precipitation) with the occurrence of these flies. The study was conducted at a site in the Tinguá Biological Reserve, located in the municipality of Nova Iguaçu, state of Rio de Janeiro, Brazil. Four traps were set up using chicken viscera as bait. The experiment was conducted over the period of May 2001 to April 2002, with two monthly collections. The captured flies were killed with ether and conserved in 70% alcohol and identified in the Laboratory of Diptera Studies (UNIRIO) and the Laboratory of Vector Insect Biology and Control (FIOCRUZ), both headquartered in the city of Rio de Janeiro, RJ, Brazil. A total of 1,987 insects were captured, 37.5% belonging to the family Calliphoridae, 29.4% to Muscidae, 16.0% to Sarcophagidae, and 17.1% to other families. The most representative species found was Phaenicia eximia (47.0%), followed by Hemilucilia semidiaphana (23.6%), Mesembrinella bellardiana (13.7%), Hemilucilia segmentaria (7.5%), Chloroprocta idioidea (4.9%), Chrysomya albiceps (1.2%), Chrysomya megacephala (0.9%), Phaenicia sericata (0.6%), Eumesembrinella sp. (0.5%), and Chrysomya putoria (0.1%). Large numbers of Calliphoridae were noted in May, June, September and January, coinciding with low rainfall and an average temperature of 21.8 to 27.0 degrees C. A negative correlation was found between the number of Calliphoridae captured and meteorological factors.

Animals↗

PubMed2002

Photobacterium damselae subsp. piscicida: an integrated view of a bacterial fish pathogen.

Pasteurellosis, or pseudotuberculosis, is a bacterial septicaemia caused by the halophilic bacterium Photobacterium damselae subsp. piscicida (formerly Pasteurella piscicida). Although this disease was first described in wild populations of white perch and striped bass, currently the natural hosts of the pathogen are a wide variety of marine fish. The disease has great economic impact both in Japan, where it affects mainly yellowtail cultures, and in the Mediterranean area, due to the losses it causes in seabream and seabass farms. This microorganism serves as a perfect model to study a bacterial fish pathogen, either at an applied level, to resolve or to mitigate the high economic losses of fish farmers, or at a basic level, for a better understanding of P. damselae subsp. piscicida biology. This article discusses the methods employed in our laboratory to study the causative agent of pasteurellosis. It reviews important aspects, from the diverse procedures for the detection and isolation of the pathogen to the latest molecular studies that have allowed its correct taxonomic allocation. Characterization of some virulence mechanisms and the available methods to prevent the disease are also presented.

Animals↗