SummaryNine strains of a novel Fusobacterium sp. were isolated from the stomach of 6-8 months old and adult pigs. The isolates were obligately anaerobic, although they endured 2 hours exposure to air. Phylogenetic analysis based on 16S rRNA and gyrase B genes demonstrated that the isolates showed high sequence similarity with Fusobacterium mortiferum, Fusobacterium ulcerans, Fusobacterium varium, Fusobacterium russii and Fusobacterium necrogenes, but formed a distinct lineage in the genus Fusobacterium. Comparative analysis of the genome of the type strain of this novel Fusobacterium sp. confirmed that it is different from other recognized Fusobacterium spp. DNA-DNA hybridization, fingerprinting and genomic %GC determination further supported the conclusion that the isolates belong to a new, distinct species. The isolates were also distinguishable from these and other Fusobacterium spp. by phenotypical characterization. The strains produced indole and exhibited proline arylamidase and glutamic acid decarboxylase activity. They did not hydrolyse esculin, did not exhibit pyroglutamic acid arylamidase, valine arylamidase, α-galactosidase, β-galactosidase, β-galactosidase-6-phosphate or α-glucosidase activity nor produced acid from cellobiose, glucose, lactose, mannitol, mannose, maltose, raffinose, saccharose, salicin or trehalose. The major fatty acids were C16 : 0 and C18 : 1ω9c. The name Fusobacterium gastrosuis sp. nov. is proposed for the novel isolates with the type strain CDW1(T) (= DSM 101753(T) = LMG 29236(T)). We also demonstrated that Clostridium rectum and Fusobacterium mortiferum represent the same species, with nomenclatural priority for the latter.
Helicobacter (H.) suis can colonize the stomach of pigs as well as humans, causing chronic gastritis and other gastric pathological changes including gastric ulceration and mucosa-associated lymphoid tissue (MALT) lymphoma. Recently, a virulence factor of H. suis, γ-glutamyl transpeptidase (GGT), has been demonstrated to play an important role in the induction of human gastric epithelial cell death and modulation of lymphocyte proliferation depending on glutamine and glutathione catabolism. In the present study, the relevance of GGT in the pathogenesis of H. suis infection was studied in mouse and Mongolian gerbil models. In addition, the relative importance of H. suis GGT was compared with that of the H. pylori GGT. A significant and different contribution of the GGT of H. suis and H. pylori was seen in terms of bacterial colonization, inflammation and the evoked immune response. In contrast to H. pyloriΔggt strains, H. suisΔggt strains were capable of colonizing the stomach at levels comparable to WT strains, although they induced significantly less overall gastric inflammation in mice. This was characterized by lower numbers of T and B cells, and a lower level of epithelial cell proliferation. In general, compared to WT strain infection, ggt mutant strains of H. suis triggered lower levels of Th1 and Th17 signature cytokine expression. A pronounced upregulation of B-lymphocyte chemoattractant CXCL13 was observed, both in animals infected with WT and ggt mutant strains of H. suis. Interestingly, H. suis GGT was shown to affect the glutamine metabolism of gastric epithelium through downregulation of the glutamine transporter ASCT2.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0163-6) contains supplementary material, which is available to authorized users.
In this study, we investigated how eye movements are influenced by different text reading goals in participants' first and second language (L1, L2). Participants had to read or study the contents of texts while their eye movements were recorded. One group was asked to read texts in L1 and L2 as they would read any expository text (informative reading). Another group was asked to study L1 and L2 texts for subsequent tests involving true/false questions (study condition). After reading, all participants (including those in the informative reading condition) completed the true/false tests without being able to further consult the texts. This allowed us to investigate to what extent reading goal and text language affect recognition memory for texts. In general, more reading time was spent on studying than on informative reading, which also resulted in higher test scores in the study condition. The L2 processing cost was larger in the study condition than in the informative reading condition: participants needed about 20% more time to study L2 texts. The results of various eye movement measures suggest that this is caused by slower word recognition processes and a smaller amount of information that can be processed simultaneously in L2. This was true not only for the first reading of the text, but also for the rereadings in the study condition. Interestingly, the additional time for L2 studying seemed to compensate for the less efficient processing, as the recognition test scores were the same in L2 as in L1.
Apart from the cynomolgus monkey-associated strain which was unable of colonizing the stomach of Mongolian gerbils, no substantial differences in virulence were found in rodent models between in vitro-cultured pig-associated, cynomolgus monkey-associated and rhesus monkey-associated H. suis strains. The experimental host determines the outcome of the immune response against H. suis infection, rather than the original host.
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