Thermococcus coalescens sp. nov., a cell-fusing hyperthermophilic archaeon from Suiyo Seamount.

A cell-fusing hyperthermophilic archaeon was isolated from hydrothermal fluid obtained from Suiyo Seamount of the Izu-Bonin Arc. The isolate, TS1(T), is an irregular coccus, usually 0.5-2 microm in diameter and motile with a polar tuft of flagella. Cells in the exponential phase of growth fused at room temperature in the presence of DNA-intercalating dye to become as large as 5 microm in diameter. Fused cells showed dark spots that moved along in the cytoplasm. Large cells with a similar appearance were also observed upon culture at 87 degrees C, suggesting the occurrence of similar cell fusions during growth. Transmission electron microscopy revealed that cells in the exponential phase possessed a thin and electron-lucent cell envelope that could be lost subsequently during culture. The fragile cell envelope must be related to cell fusion. The cells grew at 57-90 degrees C, pH 5.2-8.7 and at NaCl concentrations of 1.5-4.5 %, with the optima being 87 degrees C, pH 6.5 and 2.5 % NaCl. The isolate was an anaerobic chemo-organotroph that grew on either yeast extract or tryptone as the sole growth substrate. The genomic DNA G+C content was 53.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that the isolate was closely related to Thermococcus species. However, no significant DNA-DNA hybridization was observed between genomic DNA of strain TS1(T) and phylogenetically related Thermococcus species. We propose that isolate TS1(T) represents a novel species, Thermococcus coalescens sp. nov., with the name reflecting the cell fusion activity observed in the strain. The type strain is TS1(T) (=JCM 12540T=DSM 16538T).

Organics in chimneys and water samples from deep-sea hydrothermal systems: implications for sub-vent biosphere.

Searching for life in extreme terrestrial environments can be a model of that for extraterrestrial life. Submarine hydrothermal system is one of promising sites for the frontier of life on the earth. Here seawater and vent chimnies were collected from deep-sea hydrothermal vents at Suiyo Seamount, Izu-bonin arc, Pacific Ocean as a part of Archaean Park Project. Pure seawater sample of 300 degrees C (purity>97%) could be collected. Dissolved and total hydrolyzable amino acids were determined by ion-exchange HPLC, and their enantiomeric ratio was measured by reversed-phase HPLC for the first time. Glycine and serine were two most abundant amino acids, followed by other proteinous amino acids such as alanine, glutamic acid and aspartic acid. Non-proteinous amino acids were detected as minor constituents. Most of the amino acids detected were of the L-form. Thus amino acids of abiotic origin were quite minor, and most of the amino acids detected were formed biologically. These results, together with analytical results of the vent chimney samples, suggest that there is active microbial activities near the hydrothermal systems.

Portal vein invasion and intrahepatic micrometastasis in small hepatocellular carcinoma by gross type.

Background/AIMS: Recurrence due to clinically undetectable intrahepatic metastasis and portal vein invasion of HCC cells is not 'uncommon' even in small HCCs. The present study investigated the relationship between these factors and macroscopic types of HCC. METHODS: Surgically resected 209 cases of small HCC less than 3 cm in diameter were examined. Macroscopically, 209 cases were divided into 'vaguely nodular type', 'single nodular type', 'single nodular type with extranodular growth' and 'confluent multinodular type'. RESULTS: None of the vaguely nodular type had intrahepatic metastasis or portal vein invasion, and their diameter was significantly smaller than the other three types. 'Single nodular type with extranodular growth' and 'confluent multinodular type' show higher frequency of portal vein invasion and intrahepatic metastases than 'single nodular type'. Among 149 metastatic lesions, the distance was 10 mm or shorter in 118 (79.2%). CONCLUSIONS: It is important to precisely determine the gross type of small HCC by diagnostic imaging in order to predict portal vein invasion and micrometastasis. It is also important to ablate the tumor with enough surrounding tissue 1 cm in width at least to prevent the recurrence from those micrometastasis.