Interleukin-15 promotes intestinal dysbiosis with butyrate deficiency associated with increased susceptibility to colitis.

Dysbiosis resulting in gut-microbiome alterations with reduced butyrate production are thought to disrupt intestinal immune homeostasis and promote complex immune disorders. However, whether and how dysbiosis develops before the onset of overt pathology remains poorly defined. Interleukin-15 (IL-15) is upregulated in distressed tissue and its overexpression is thought to predispose susceptible individuals to and have a role in the pathogenesis of celiac disease and inflammatory bowel disease (IBD). Although the immunological roles of IL-15 have been largely studied, its potential impact on the microbiota remains unexplored. Analysis of 16S ribosomal RNA-based inventories of bacterial communities in mice overexpressing IL-15 in the intestinal epithelium (villin-IL-15 transgenic (v-IL-15tg) mice) shows distinct changes in the composition of the intestinal bacteria. Although some alterations are specific to individual intestinal compartments, others are found across the ileum, cecum and feces. In particular, IL-15 overexpression restructures the composition of the microbiota with a decrease in butyrate-producing bacteria that is associated with a reduction in luminal butyrate levels across all intestinal compartments. Fecal microbiota transplant experiments of wild-type and v-IL-15tg microbiota into germ-free mice further indicate that diminishing butyrate concentration observed in the intestinal lumen of v-IL-15tg mice is the result of intrinsic alterations in the microbiota induced by IL-15. This reconfiguration of the microbiota is associated with increased susceptibility to dextran sodium sulfate-induced colitis. Altogether, this study reveals that IL-15 impacts butyrate-producing bacteria and lowers butyrate levels in the absence of overt pathology, which represent events that precede and promote intestinal inflammatory diseases.

Spatial scale drives patterns in soil bacterial diversity.

Soil microbial communities are essential for ecosystem function, but linking community composition to biogeochemical processes is challenging because of high microbial diversity and large spatial variability of most soil characteristics. We investigated soil bacterial community structure in a switchgrass stand planted on soil with a history of grassland vegetation at high spatial resolution to determine whether biogeographic trends occurred at the centimeter scale. Moreover, we tested whether such heterogeneity, if present, influenced community structure within or among ecosystems. Pronounced heterogeneity was observed at centimeter scales, with abrupt changes in relative abundance of phyla from sample to sample. At the ecosystem scale (> 10 m), however, bacterial community composition and structure were subtly, but significantly, altered by fertilization, with higher alpha diversity in fertilized plots. Moreover, by comparing these data with data from 1772 soils from the Earth Microbiome Project, it was found that 20% of bacterial taxa were shared between their site and diverse globally sourced soil samples, while grassland soils shared approximately 40% of their operational taxonomic units with the current study. By spanning several orders of magnitude, the analysis suggested that extreme patchiness characterized community structure at smaller scales but that coherent patterns emerged at larger length scales.

Novel Haemoproteus species (Haemosporida: Haemoproteidae) from the swallow-tailed gull (Lariidae), with remarks on the host range of hippoboscid-transmitted avian hemoproteids.

Haemoproteus (Haemoproteus) jenniae n. sp. (Haemosporida: Haemoproteidae) is described from a Galapagos bird, the swallow-tailed gull Creagrus furcatus (Charadriiformes, Laridae), based on the morphology of its blood stages and segments of the mitochondrial cytochrome b (cyt b) gene. The most distinctive features of H. jenniae development are the circumnuclear gametocytes occupying all cytoplasmic space in infected erythrocytes and the presence of advanced, growing gametocytes in which the pellicle is closely appressed to the erythrocyte envelope but does not extend to the erythrocyte nucleus. This parasite is distinguishable from Haemoproteus larae, which produces similar gametocytes and parasitizes closely related species of Laridae. Haemoproteus jenniae can be distinguished from H. larae primarily due to (1) the predominantly amoeboid outline of young gametocytes, (2) diffuse macrogametocyte nuclei which do not possess distinguishable nucleoli, (3) the consistent size and shape of pigment granules, and (4) the absence of rod-like pigment granules from gametocytes. Additionally, fully-grown gametocytes of H. jenniae cause both the marked hypertrophy of infected erythrocytes in width and the rounding up of the host cells, which is not the case in H. larae. Phylogenetic analyses identified the DNA lineages that are associated with H. jenniae and showed that this parasite is more closely related to the hippoboscid-transmitted (Hippoboscidae) species than to the Culicoides spp.-transmitted (Ceratopogonidae) species of avian hemoproteids. Genetic divergence between morphologically well-differentiated H. jenniae and the hippoboscid-transmitted Haemoproteus iwa, the closely related parasite of frigatebirds (Fregatidae, Pelecaniformes), is only 0.6%; cyt b sequences of these parasites differ only by 1 base pair. This is the first example of such a small genetic difference in the cyt b gene between species of the subgenus Haemoproteus. In a segment of caseinolytic protease C gene (ClpC), genetic divergence is 4% between H. jenniae and H. iwa. This study corroborates the conclusion that hippoboscid-transmitted Haemoproteus parasites infect not only Columbiformes birds but also infect marine birds belonging to Pelecaniformes and Charadriiformes. We conclude that the vertebrate host range should be used cautiously in identification of subgenera of avian Haemoproteus species and that the phylogenies based on the cyt b gene provide evidence for determining the subgeneric position of avian hemoproteids.

Meeting report: the 2 annual argonne soils workshop, argonne national laboratory, chicago illinois, USA, october 6-8, 2010.

This report summarizes the proceedings of the 2(nd) Annual Argonne Soils Workshop held at Argonne National Laboratory October 6-8, 2010. The workshop assembled a diverse group of soil ecologists, microbiologists, molecular biologists, and computational scientists to discuss the challenges and opportunities related to implementation of metagenomics approaches in soil microbial ecology. The overarching theme of the workshop was "designing ecologically meaningful soil metagenomics research", which encouraged presentations on both ecological and computational topics. The workshop fostered valuable cross-discipline communication and delivered the message that soil metagenomics research must be based on an iterative process between biological inquiry and bioinformatics tools.

Hippoboscid-transmitted Haemoproteus parasites (Haemosporida) infect Galapagos Pelecaniform birds: evidence from molecular and morphological studies, with a description of Haemoproteus iwa.

Haemosporidian parasites are widely distributed and common parasites of birds, and the application of molecular techniques has revealed remarkable diversity among their lineages. Four haemosporidian genera infect avian hosts (Plasmodium, Haemoproteus, Leucocytozoon and Fallisia), and Haemoproteus is split into two sub-genera based on morphological evidence and phylogenetic support for two divergent sister clades. One clade (Haemoproteus (Parahaemoproteus)) contains parasites developing in birds belonging to several different orders, except pigeons and doves (Columbiformes), while the other (Haemoproteus (Haemoproteus)) has previously been shown to only infect dove hosts. Here we provide molecular and morphological identification of Haemoproteus parasites from several seabird species that are closely related to those found in dove hosts. We also document a deeply divergent clade with two haemosporidian lineages recovered primarily from frigatebirds (Fregatidae, Pelecaniformes) that is sister to the hippoboscid-(Hippoboscidae) transmitted dove parasites. One of the lineages in this new clade of parasites belongs to Haemoproteus iwa and is distributed in two species of frigatebird (Fregata) hosts from Hawaii, the Galapagos Islands, the eastern Pacific and throughout the Caribbean Basin. Haemosporidian parasites are often considered rare in seabirds due in part to the lack or low activity of some dipteran vectors (e.g., mosquitos, biting midges) in marine and coastal environments; however, we show that H. iwa is prevalent and is very likely vectored among frigatebirds by hippoboscid flies which are abundant on frigatebirds and other seabirds. This study supports the existence of two sister clades of avian Haemoproteus in accord with the subgeneric classification of avian hemoproteids. Description of H. iwa from Galapagos Fregata minor is given based on morphology of blood stages and segments of the mitochondrial cytochrome b gene, which can be used for identification. This study shows that hippoboscid flies warrant more attention as vectors of avian Haemoproteus spp., particularly in marine and coastal environments.