Cell-surface Fcγ receptors mediate innate and adaptive immune responses. Human Fcγ receptor I (hFcγRI) binds IgGs with high affinity and is the only Fcγ receptor that can effectively capture monomeric IgGs. However, the molecular basis of hFcγRI’s interaction with Fc has not been determined, limiting our understanding of this major immune receptor. Here we report the crystal structure of a complex between hFcγRI and human Fc, at 1.80 Å resolution, revealing an unique hydrophobic pocket at the surface of hFcγRI perfectly suited for residue Leu235 of Fc, which explains the high affinity of this complex. Structural, kinetic and thermodynamic data demonstrate that the binding mechanism is governed by a combination of non-covalent interactions, bridging water molecules and the dynamic features of Fc. In addition, the hinge region of hFcγRI-bound Fc adopts a straight conformation, potentially orienting the Fab moiety. These findings will stimulate the development of novel therapeutic strategies involving hFcγRI.

Two thermophilic strains, designated 607^T and 606b, were isolated from a compost pile in Japan. The novel strains were Gram-positive, aerobic, spore-forming rods. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strains 607^T and 606b were closely related to Bacillus naganoensis (94.0–94.1 % similarity) and separated from clusters of the related genera Bacillus (<91.9 %) and Sporolactobacillus (91.0–92.5 %). In addition, some chemotaxonomic and physiological characteristics of strains 607^T and 606b differed from those of B. naganoensis and the two related genera. Several differences in physiological characteristics and 16S–23S rRNA gene internal transcribed spacer region nucleotide sequences were observed between strains 607^T and 606b; however, DNA–DNA hybridization indicated that these two strains belonged to the same species. From these results, it is proposed that strains 607^T and 606b represent the type species of a new genus, Tuberibacillus calidus gen. nov., sp. nov., with strain 607^T (=JCM 13397^T=DSM 17572^T) as the type strain. In addition, the results of phylogenetic analyses, as well as chemotaxonomic and physiological characterization, indicated that B. naganoensis and Bacillus laevolacticus did not belong to the genus Bacillus. Based on these results, it is proposed that B. naganoensis and B. laevolacticus should be transferred to Pullulanibacillus naganoensis gen. nov., comb. nov. and Sporolactobacillus laevolacticus comb. nov., respectively.

Four thermophilic, Gram-positive strains, designated H0165^T, 500275^T, C0170 and 700375, were isolated from a composting process in Japan. The isolates grew aerobically at about 65 °C on a solid medium with formation of substrate mycelia; spores were produced singly along the mycelia. These morphological characters resembled those of some type strains of species belonging to the family ‘Thermoactinomycetaceae’, except that aerial mycelia were not formed. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the closest related species to the isolates were members of the family ‘Thermoactinomycetaceae’, but that the isolates formed an independent phylogenetic lineage. Some chemotaxonomic characters of the isolates, such as DNA G+C contents of 58·7–60·3 mol%, MK-7 as the major menaquinone and cellular fatty acid profiles, differed from those of members of the family ‘Thermoactinomycetaceae’. DNA–DNA hybridization showed that the isolates could be divided into two genomic groups, strain H0165^T and the other three strains. These results indicated that the four isolates should be classified into two species of a novel genus in the family ‘Thermoactinomycetaceae’, for which the names Planifilum fimeticola gen. nov., sp. nov. (type strain H0165^T=ATCC BAA-969^T=JCM 12507^T) and Planifilum fulgidum sp. nov. (type strain 500275^T=ATCC BAA-970^T=JCM 12508^T) are proposed.

A nitrogen-fixing bacterium, designated strain 6H33b^T, was isolated from a compost pile in Japan. The nitrogenase activity of this strain was detected based on its acetylene-reducing activity under low oxygen concentrations (2–4 %). An analysis of the genes responsible for nitrogen fixation in this strain,nifHandnifD, indicated a close relationship to those ofPseudomonas stutzeriA15 (A1501). Sequence similarity searches based on the 16S rRNA gene sequences showed that strain 6H33b^Tbelongs within the genusPseudomonas sensu stricto; closest similarity was withPseudomonas indica(97·3 %). A comparison of several taxonomic characteristics of 6H33b^Twith those ofP. indicaand some type strains of the genusPseudomonas sensu strictoindicated that 6H33b^Tcould be distinguished fromP. indicabased on the presence of nitrogen fixation ability, the absence of nitrate reduction and denitrification abilities and the utilization of some sugars and organic acids. Phylogenetic analyses and the results of DNA–DNA hybridization experiments also indicated that strain 6H33b^Trepresents a species distinct fromP. indica. From these results, it is proposed that strain 6H33b^T(=ATCC BAA-1049^T=JCM 12708^T) is classified as the type strain of a novel species of the genusPseudomonas sensu strictounder the namePseudomonas azotifigenssp. nov.

A bacterial strain, designated MSd3^T, was isolated from a freshwater sample collected from the Hosoda River in Japan. The cells of strain MSd3^Twere Gram-stain-negative, non-spore-forming, aerobic, non-motile, curved rods forming rings, coils and undulating filaments. The 16S rRNA gene sequence of strain MSd3^Tshowed closest similarity to that ofSpirosoma lingualeDSM 74^T(97.6 % similarity) and similarity to other members of the genusSpirosomaranged from 90.3 to 95.9 %. Strain MSd3^Tcontained menaquinone 7 as the sole respiratory quinone. The major cellular fatty acids were summed feature 3 (C_16 : 1ω6cand/or C_16 : 1ω7c) and C_16 : 1ω5c. The polar lipids were phosphatidylethanolamine, three unidentified aminophospholipids and three unidentified polar lipids. The DNA G+C content was 53.3 mol%. The DNA–DNA relatedness between strain MSd3^TandS. lingualeDSM 74^Twas 19 % or 25 % (reciprocal value). From the chemotaxonomic and physiological data and the levels of DNA–DNA relatedness, strain MSd3^Tshould be classified as the representative of a novel species of the genusSpirosoma, for which the nameSpirosoma fluvialesp. nov. (type strain MSd3^T = JCM 30659^T = DSM 29961^T) is proposed.