Host Responses to the Pathogen Mycobacterium avium subsp. paratuberculosis and Beneficial Microbes Exhibit Host Sex Specificity

Differences between microbial pathogenesis in male and female hosts are well characterized in disease conditions connected to sexual transmission. However, limited biological insight is available on variances attributed to sex specificity in host-microbe interactions, and it is most often a minimized variable outside these transmission events. In this work, we studied two gut microbes—a pathogen, Mycobacterium avium subsp. paratuberculosis, and a probiotic, Lactobacillus animalis NP-51—and the interaction between each agent and the male and female gastrointestinal systems. This trial was conducted in BALB/c mice (n = 5 per experimental group and per sex at a given time point), with analysis at four time points over 180 days. Host responses to M. avium subsp. paratuberculosis and L. animalis were sensitive to sex. Cytokines that were significantly different (P ≤ 0.05) between the sexes included interleukin-1α/β (IL-1α/β), IL-17, IL-6, IL-10, IL-12, and gamma interferon (IFN-γ) and were dependent on experimental conditions. However, granulocyte-macrophage colony-stimulating factor (GM-CSF), vascular endothelial growth factor (VEGF), and IL-13/23 showed no sex specificity. A metabolomics study indicated a 0.5- to 2.0-fold (log₂ scale) increase in short-chain fatty acids (butyrate and acetate) in males and greater increases in o-phosphocholine or histidine from female colon tissues; variances distinct to each sex were observed with age or long-term probiotic consumption. Two genera, Staphylococcus and Roseburia, were consistently overrepresented in females compared to males; other species were specific to one sex but fluctuated depending on experimental conditions. The differences observed suggest that male and female gut tissues and microbiota respond to newly introduced microorganisms differently and that gut-associated microorganisms with host immune system responses and metabolic activity are supported by biology distinct to the host sex.     

Reef Endemism,Host Specificity and Temporal Stability in Populations of Symbiotic Dinoflagellates from Two Ecologically Dominant Caribbean Corals

Background

The dinoflagellate genus Symbiodinium forms symbioses with numerous protistan and invertebrate metazoan hosts. However, few data on symbiont genetic structure are available, hindering predictions of how these populations and their host associations will fair in the face of global climate change.

Methodology/Principal Findings

Here, Symbiodinium population structure from two of the Caribbean''s ecologically dominant scleractinian corals, Montastraea faveolata and M. annularis, was examined. Tagged colonies on Florida Keys and Bahamian (i.e., Exuma Cays) reefs were sampled from 2003–2005 and their Symbiodinium diversity assessed via internal transcribed spacer 2 (ITS2) rDNA and three Symbiodinium Clade B-specific microsatellite loci. Generally, the majority of host individuals at a site harbored an identical Symbiodinium ITS2 “type” B1 microsatellite genotype. Notably, symbiont genotypes were largely reef endemic, suggesting a near absence of dispersal between populations. Relative to the Bahamas, sympatric M. faveolata and M. annularis in the Florida Keys harbored unique Symbiodinium populations, implying regional host specificity in these relationships. Furthermore, within-colony Symbiodinium population structure remained stable through time and environmental perturbation, including a prolonged bleaching event in 2005.

Conclusions/Significance

Taken together, the population-level endemism, specificity and stability exhibited by Symbiodinium raises concerns about the long-term adaptive capacity and persistence of these symbioses in an uncertain future of climate change.     

Conservation of a Symbiotic DNA Region in Soybean Root Nodule Bacteria

Bradyrhizobium japonicum USDA 3I1b110 contains a DNA region in which symbiotic genes and many repeated sequences are closely linked. Hybridization analysis revealed that this region was highly conserved in some B. japonicum strains (USDA 24, USDA 122, USDA 123, ATCC 10324, 61A24) but not in others (USDA 76, 61A76, 61A101). The genomic presence of multiple copies of one of the repeated sequences (RSα) appeared to be specifically characteristic for soybean root nodule bacteria, including the fast-growing Rhizobium fredii, which carries most of these RSα copies on the symbiotic plasmid.     

Anaerobiosis and Symbiosis with Bacteria in Free-living Ciliates

SYNOPSIS. Marine, sediment-dwelling ciliates were examined for cytochrome oxidase activity by a cytochemical method and for fine structural details. Species of Plagiopylidae (Trichostomatida), i.e. Plagiopyla frontata, Sonderia vorax and Sonderia sp., and of Heterotrichida, i.e., Parablepharisma pellitum, Parablepharisma sp., Metopus contortus, Metopus vestitus and Caenomorpha capucina ; previously considered to be obligate anaerobes because of their sulfide-containing habitat, do not have cytochrome oxidase activity or mitochondria with cristae or tubuli. The evolutionary origin and significance of anaerobic ciliates is discussed. Most of the anaerobic ciliates harbor a flora of ecto- and endosymbiotic bacteria as demonstrated by transmission and scanning electron micrographs. It is speculated that the bacteria may utilize the metabolic end products of the protozoa for growth and energy yielding processes. These associations are also compared with other, previously described cases of symbiosis involving prokaryotes and protozoa.     

Zamilon,a Novel Virophage with Mimiviridae Host Specificity

Virophages, which are potentially important ecological regulators, have been discovered in association with members of the order Megavirales. Sputnik virophages target the Mimiviridae, Mavirus was identified with the Cafeteria roenbergensis virus, and virophage genomes reconstructed by metagenomic analyses may be associated with the Phycodnaviridae. Despite the fact that the Sputnik virophages were isolated with viruses belonging to group A of the Mimiviridae, they can grow in amoebae infected by Mimiviridae from groups A, B or C. In this study we describe Zamilon, the first virophage isolated with a member of group C of the Mimiviridae family. By co-culturing amoebae with purified Zamilon, we found that the virophage is able to multiply with members of groups B and C of the Mimiviridae family but not with viruses from group A. Zamilon has a 17,276 bp DNA genome that potentially encodes 20 genes. Most of these genes are closely related to genes from the Sputnik virophage, yet two are more related to Megavirus chiliensis genes, a group B Mimiviridae, and one to Moumouvirus monve transpoviron.     

Tri-Party Underground Symbiosis between a Weevil,Bacteria and a Desert Plant

Inhabitants of arid ecosystems face severe nitrogen and water limitations. Inventive adaptations by organisms occupying such habitats are essential for survival. This study describes a tri-party symbiotic interaction between a plant (Salsola inermis), a beetle (Conorhynchus pistor), and a bacterium (Klebsiella pneumonia). The weevil survives by living within a mud structure affixed to the plant roots, thus benefiting from increased carbon and water, and refuge from predators and parasites. Active nitrogen-fixing bacteria harbored within the weevil''s gut mediate this interaction, by supplying nitrogen to the system, which eventually promotes seed development. We studied the correlation between the weevil''s existence and (i) root carbon and nitrogen content, (ii) soil water content and (iii) seed weight. Roots hosting weevils contained more nitrogen, heavier seeds and less carbon. In addition, water content was higher around the roots than in open spaces a short distance from the plant stem. Bacterial studies and nitrogen-fixation analyses, including molecular and chemical assays, indicated atmospheric nitrogen fixation in the larval stage and identified the bacterium. The coexistence of weevil and bacterial behavior coinciding with the plant''s life cycle was revealed here by a long period of field observations. Out of over 60,000 known weevils, this is the only report of a weevil living most of its life underground without harming plants. The unique tri-party interaction described herein shows the important ecological role of desert plant roots and provides an example of a sustainable consortium of living organisms coping with the challenging desert environment.     

Host and Site Specificity in the Coccidia: a Perspective1

Some generalizations of a decade ago are reexamined in light of modern advances in coccidiology. Perhaps surprisingly, not many modifications need or can yet be made. Future successes of significance will be in areas of immunology and chemical genetics.     

Molecular Mechanism by Which Surface Antigen HP0197 Mediates Host Cell Attachment in the Pathogenic Bacteria Streptococcus suis

Streptococcus suis, one of the most important and prevalent pathogens inswine, presents a major challenge to global public health. HP0197 is an S.suis surface antigen that was previously identified by immunoproteomics and canbind to the host cell surface. Here, we investigated the interaction between HP0197 andthe host cell surface glycosaminoglycans (GAGs) using indirect immunofluorescence and celladhesion inhibition assays. In addition, we determined that a novel 18-kDa domain in theN-terminal region of HP0197 functions as the GAG-binding domain. We then solved thethree-dimensional structures of the N-terminal 18-kDa and C-terminal G5 domains usingx-ray crystallography. Based on this structural information, the GAG-binding sites inHP0197 were predicted and subsequently verified using site-directed mutagenesis andindirect immunofluorescence. The results indicate that the positively charged residues onthe exposed surface of the 18-kDa domain, which are primarily lysines, likely play acritical role in the HP0197-heparin interaction that mediates bacterium-host celladhesion. Understanding this molecular mechanism may provide a basis for the developmentof effective drugs and therapeutic strategies for treating streptococcal infections.     

Eimeria tenella: Host Specificity in Gallinaceous Birds

SYNOPSIS. Eight species representing 8 genera of gallinaceous birds were used: Alectoris graeca; Colinus virginianus; Coturnix coturnix; Gallus gallus; Meleagris gallopavo; Numidia meleagris; Pavo cristatus; Phasianus colchicus. Three-week-old birds were dosed with sporulated oocysts of Eimeria tenella Beltsville strain. At 4, 24, 48, 72, 96, 120, 144, and 168 hr after inoculation, 1-3 infected birds and uninoculated controls of each species were killed by cardiac exsanguination. Pieces of intestines were fixed and examined for stages of E. tenella as stained paraffin sections or indirect fluorescent antibody preparations. Oocyst counts were made in droppings collected for the first 6 days of the patent period. Sporozoites were found in the lamina propria of some birds of 5 species at 4 hr postinoculation, but no stages were found thereafter except in the breeds of G. gallus and A. graeca. At 144 and 168 hr postinoculation, a few macrogametes were found in the ceca of 2 A. graeca , but no oocysts were found in the feces. No statistical difference was found between the number of oocysts produced/bird in the breeds of G. gallus examined. It is evident from these observations that E. tenella did not complete its life cycle in several close phylogenetic relatives of G. gallus , even though in other studies this parasite was found to complete its life cycle in cell cultures derived from the same birds.     

Species Richness and Host Specificity among Caterpillar Ensembles on Shrubs in the Andes of Southern Ecuador

Caterpillar ensembles were sampled on 16 species of shrubs from the family Asteraceae and the genus Piper (Piperaceae) in open and forest habitats in the Andean montane forest zone of southern Ecuador between August 2007 and May 2009. Trophic affiliations of caterpillars to the host plants were confirmed in feeding trials. Overall, species richness of herbivorous caterpillars was high (191 species across all plants), but varied strongly between ensembles associated with different plant species (2?C96 lepidopteran species per shrub species). Ensembles on Piper species were characterized by low effective species numbers and high dominance of one or two species of the Geometridae genus Eois Hübner. Low species number and high dominance were also found on latex-bearing Erato polymnioides, whereas ensembles on two other Asteraceae species were far more diverse and less strongly shaped by a few dominant species. The observed diversity patterns fit well to the concept that anti-herbivore defenses of plants are the major factors regulating associated insect ensembles. Local abundance and geographic range of host plants appear to have less influence. Lepidopteran species feeding on Asteraceae were found to be more generalistic than those feeding on Piper species. We conclude that caterpillar ensembles on most, but not all, studied plant species are defined by a small number of dominant species, which usually are narrow host specialists. This pattern was more distinct on Piper shrubs in forest understory, whereas Asteraceae in disturbed habitats had more open caterpillar ensembles.