Publications

4880

Abstract Marine pelagic redoxclines are areas of enhanced biogeochemical cycling inhabited by distinct functional groups of prokaryotes. In this study, the diversity and abundance of archaeal and bacterial nitrifying populations throughout a pelagic redoxcline in the central Baltic Sea were examined using a suite of molecular methods. 16S rRNA/rRNA gene as well as bacterial and archaeal amoA mRNA/amoA gene fingerprints and clone libraries revealed that the putative nitrifying assemblages consisted solely of one crenarchaeotal subcluster, named GD2, which was closely related to Candidatus Nitrosopumilus maritimus. Neither distinct differences between transcript- and gene-based fingerprints nor pronounced differences in the crenarchaeotal composition throughout the whole redoxcline were detected. The abundance of this GD2 subgroup, as determined by the oligonucleotide probe Cren537 and the newly developed and more specific probe Cren679 showed that GD2 and total crenarchaeotal cell numbers were nearly identical throughout the redoxcline. The highest GD2 abundance (2.3 × 105 cells ml−1) occurred in the suboxic zone, accounting for around 26% of total prokaryotic cells. Below the chemocline, GD2 abundance was relatively stable (1.5–1.9 × 105 cells ml−1). Archaeal amoA expression was detected only in the putative nitrification zone and formed a narrow band in the suboxic layer, where ammonium, oxygen, nitrate, nitrite and phosphate concentrations were below 5 μmol l−1. To our knowledge this is the first study to show the dominance of only one crenarchaeotal nitrifying key cluster in a natural habitat. The metabolic properties and survival mechanisms present in this cluster inside and outside the nitrification zone remain to be determined.

AbstractBackground:  “Candidatus Helicobacter heilmannii” induce chronic gastritis, which eventually leads to gastric B‐cell type mucosa‐associated lymphoid tissue (MALT) lymphoma. This study was performed using an animal model of infection with “Candidatus Helicobacter heilmannii” to elucidate how this chronic inflammation is induced or maintained.Materials and Methods:  BALB/c mice were infected with the “Candidatus Helicobacter heilmannii” isolate SH4. The animals were examined at 8, 26, 54, and 83 weeks after the infection. The stomach of the animals was resected and immunostained for peripheral lymph node addressin (PNAd) and mucosal addressin cell adhesion molecule 1 (MAdCAM‐1), “Candidatus Helicobacter heilmannii,” and CD45R/B220. An in vitro binding assay with L‐ and E‐selectin·IgM chimeric proteins was performed. Real‐time polymerase chain reaction was used to evaluate transcripts of N‐acetylglucosamine‐6‐O‐sulfotransferases (GlcNAc6STs), which direct the expression of the PNAd and MAdCAM‐1.Results:  Chronic gastritis developed in the infected animals, and its severity increased with the duration of the infection. B‐cell type MALT lymphoma developed in some animals at 54 and 83 weeks after infection. PNAd‐ and MAdCAM‐1‐expressing high endothelial venule (HEV)‐like vessels were induced in infected animals which developed chronic gastritis and MALT lymphoma. The number of HEV‐like vessels increased as chronic inflammation progressed. The induced HEV‐like vessels were bound by L‐ and E‐selectin·IgM chimeric protein. mRNA expressions of GlcNAc6ST‐1 and MAdCAM‐1 increased in the infected animals.Conclusions:  HEV‐like vessels expressing GlcNAc6ST‐1‐mediated L‐selectin ligand carbohydrate and MAdCAM‐1 may play a crucial role in the pathogenesis of “Candidatus Helicobacter heilmannii”‐induced chronic gastritis and MALT lymphoma.

A novel aerobic, heterotrophic bacterium, designated BiosLi39T, was isolated from the South East Pacific Ocean. Cells were Gram-negative gliding rods forming yellow colonies on marine agar. The isolate was oxidase-, catalase- and alkaline phosphatase-positive andβ-galactosidase-negative. Strain BiosLi39Tgrew at 20-37 °C (optimum 30 °C), at pH 7.0–9.0 (optimum pH 8.0) and with 20–60 g NaCl l−1(optimum 30–50 g NaCl l−1). The fatty acids (>1 %) comprised iso-C14 : 0, iso-C15 : 1G, iso-C15 : 0, anteiso-C15 : 0, C15 : 1G, C15 : 0, iso-C15 : 02-OH, iso-C16 : 1G, iso-C16 : 0, iso-C16 : 03-OH, iso-C16 : 02-OH, iso-C17 : 03-OH, C17 : 02-OH and three unidentified components with equivalent chain lengths of 17.87, 18.10 and 18.71. A significant proportion of the hydroxylated fatty acids are amide-linked. The lipid pattern indicated the presence of phosphatidylethanolamine, two unidentified aminolipids and three unidentified polar lipids. The strain contained menaquinone 7 as the sole respiratory lipoquinone and did not produce flexirubin-type pigments. The G+C content of the genomic DNA was 37.2 mol%. Comparative 16S rRNA gene sequence analysis indicated that strain BiosLi39Twas distantly related to all of the representatives of the phylumBacteroidetes. Its closest relative wasMarinoscillum furvescensIFO 15994T, with which it shared 92.5 % 16S rRNA gene sequence similarity. On the basis of genotypic, phenotypic and chemotaxonomic characteristics, we propose a novel genus and species,Ekhidnagen. nov., sp. nov., with type strain BiosLi39T(=DSM 19307T=CIP 109600T=OOB 398T).

ABSTRACT Mealybugs (Coccoidea: Pseudococcidae) are sap-sucking plant parasites that harbor bacterial endosymbionts within specialized organs. Previous studies have identified two subfamilies, Pseudococcinae and Phenacoccinae, within mealybugs and determined the primary endosymbionts (P-endosymbionts) of the Pseudococcinae to be Betaproteobacteria (“ Candidatus Tremblaya princeps”) containing Gammaproteobacteria secondary symbionts. Here, the P-endosymbionts of phenacoccine mealybugs are characterized based on 16S rRNA from the bacteria of 20 species of phenacoccine mealybugs and four outgroup Puto species (Coccoidea: Putoidae) and aligned to more than 100 published 16S rRNA sequences from symbiotic and free-living bacteria. Phylogenetic analyses recovered three separate lineages of bacteria from the Phenacoccinae, and these are considered to be the P-endosymbionts of their respective mealybug hosts, with those from (i) the mealybug genus Rastrococcus belonging to the Bacteroidetes , (ii) the subterranean mealybugs, tribe Rhizoecini, also within Bacteroidetes , in a clade sister to cockroach endosymbionts ( Blattabacterium ), and (iii) the remaining Phenacoccinae within the Betaproteobacteria , forming a well-supported sister group to “ Candidatus Tremblaya princeps.” Names are proposed for two strongly supported lineages: “ Candidatus Brownia rhizoecola” for P-endosymbionts of Rhizoecini and “ Candidatus Tremblaya phenacola” for P-endosymbionts of Phenacoccinae excluding Rastrococcus and Rhizoecini. Rates of nucleotide substitution among lineages of Tremblaya were inferred to be significantly faster than those of free-living Betaproteobacteria . Analyses also recovered a clade of Gammaproteobacteria , sister to the P-endosymbiont lineage of aphids (“ Candidatus Buchnera aphidicola”), containing the endosymbionts of Putoidae, the secondary endosymbionts of pseudococcine mealybugs, and the endosymbionts of several other insect groups.