Yoko Katayama

A re-evaluation of the taxonomy of Paracoccus denitrificans and a proposal for the combination Paracoccus pantotrophus comb. nov.

Comparison of both 16S rRNA coding sequences and DNA-DNA hybridization of ten strains of alpha-subclass of Proteobacteria currently classified as strains of Paracoccus denitrificans has shown that they fall into two groups which are distinct from each other at the species level. Comparison with published data on the cytochrome c profiles and other 16S rRNA coding sequences in the literature has confirmed these observations and enabled several other strains also to be assigned to these two groups. Group A comprises strains ATCC 17741T (the type strain of P. denitrificans), LMD 22.21T, DSM 413T, ATCC 19367, ATCC 13543, DSM 1404, DSM 1405, Pd 1222 (a genetic modification of DSM 413T) and NCIMB 8944. Group B comprises ATCC 35512T (the original type strain of Thiosphaera pantotropha), LMD 82.5T, LMD 92.63, DSM 65, LMG 4218, IAM 12479, JCM 6892, DSM 11072, DSM 11073 and DSM 11104. In light of these findings, it is proposed that: (1) strains of group A are retained as P. denitrificans, with ATCC 17741T as the type strain of the type species; and (2) all strains of group B are assigned to the new species combination Paracoccus pantotrophus comb. nov., with strain ATCC 35512T as the type strain. Comparative 16S rRNA sequence analysis and DNA-DNA hybridization of strains of Paracoccus versutus confirm that this species is distinct from both P. denitrificans and P. pantotrophus, but that its nearest phylogenetic neighbour is P. pantotrophus.

Paracoccus thiocyanatus sp. nov., a new species of thiocyanate-utilizing facultative chemolithotroph, and transfer of Thiobacillus versutus to the genus Paracoccus as Paracoccus versutus comb. nov. with emendation of the genus.

A facultatively chemolithotrophic thiocyanate-degrading bacterium, strain THI 011T, which was previously isolated from activated sludge and tentatively named Thiobacillus sp., was studied taxonomically and phylogenetically. This bacterium utilizes thiocyanate as sole energy source and the specific growth rate for chemolithoautotrophic growth with thiocyanate was 0.059 h-1. Molecular phylogenetic relationships of strain THI 011T to Thiobacillus versutus and members of the genus Paracoccus were elucidated by comparing 16S rRNA gene sequences. Binary sequence comparisons showed that strain THI 011T was most related to Paracoccus aminophilus, at a similarity level of 97.0%, and T. versutus was most similar to Paracoccus denitrificans, at a level of 99.1%. A neighbour-joining phylogenetic tree showed that strain THI 011T formed a cluster together with T. versutus and known species of the genus Paracoccus within the alpha-3 subclass of the Proteobacteria. DNA-DNA hybridization assays and phenotypic studies indicated that strain THI 011T differed from T. versutus and known species of the genus Paracoccus. On the basis of these results, we propose to classify strain THI 011T into a new species of the genus Paracoccus with the name Paracoccus thiocyanatus sp. nov. We also propose to transfer T. versutus to the genus Paracoccus and present an emended description of the genus.

Rhodothermus obamensis sp. nov., a Modern Lineage of Extremely Thermophilic Marine Bacteria

A novel extremely thermophilic bacterium was isolated from a shallow marine hydrothermal vent environment (depth, 22 m) in Tachibana Bay, Nagasaki Prefecture, Japan. The cells of this organism were gram-negative rods. Growth occurred at temperatures between 50 and 85 degrees C (optimum temperature, 80 degrees C; doubling time at optimum temperature, 90 min), at pH 5.5 and 9.0 (optimum pH, 7.0), and in the presence of 1 and 5% NaCl (optimum NaCl concentration, 3%). The new isolate was an aerobic heterotroph which utilized the following compounds as sole energy and carbon sources: yeast extract, peptone, starch, casein, Casamino Acids, a variety of sugars, some carboxylic acids, and amino acids. As determined by a sequence analysis of the 16S rRNA, the new isolate belongs to the genus Rhodothermus and represents a modern lineage of extreme thermophiles within the domain Bacteria. On the basis of the physiological and molecular properties of the new isolate, we describe a new species, Rhodothermus obamensis. The type strain of R. obamensis is strain OKD7 (= JCM 9785).

Phylogeny and photosynthetic features of Thiobacillus acidophilus and related acidophilic bacteria : its transfer to the genus Acidiphilium as Acidiphilium acidophilum comb. nov

Phylogenetic analyses based on 16S rDNA sequences and genomic DNA-DNA relatedness showed that the sulphur-oxidizing facultative chemolithotroph Thiobacillus acidophilus was closely related to members of the genus Acidiphilium, which is a group of strictly aerobic, heterotrophic acidophiles now categorized into aerobic photosynthetic bacteria. Lipophilic pigment analyses revealed that zinc-chelated bacteriochlorophyll a and carotenoids occurred in appreciable amounts in T. acidophilus and all established species of the genus Acidiphilium. PCR experiments showed that T. acidophilus as well as Acidiphilium species contained puf genes, encoding the photosynthetic reaction centre proteins and the core light-harvesting complex of the purple bacteria. There were high similarities between T. acidophilus and Acidiphilium species in the primary structure of their reaction centre proteins deduced from the nucleotide sequence data. The phylogenetic tree of the reaction centre proteins was in agreement with the 16S rDNA sequence-based phylogenetic tree in the relationship between T. acidophilus and Acidiphilium species and between the Acidiphilium cluster and other purple photosynthetic bacteria. Based on these results, together with previous phylogenetic and phenotypic information, it is proposed to reclassify T. acidophilus (Guay and Silver) Harrison 1983 as Acidiphilium acidophilum comb. nov. The type strain is ATCC 27807T (= DSM 700T).

Isoprenoid quinone composition of some marine Alteromonas, Marinomonas, Deleya, Pseudomonas and Shewanella species

The isoprenoid quinone composition of 51 Gram-negative, aerobic, marine bacteria representing the genera Alteromonas, Marinomonas, Deleya, Pseudomonas and Shewanella was examined using high-performance liquid chromatography. Alteromonas and Marinomonas strains contained ubiquinone with eight isoprene units as their most abundant component, whilst ubiquinones with nine isoprene units predominated in Deleya and marine Pseudomonas strains. Members of the genus Shewanella contained both ubiquinones and menaquinones. The presence of two types of isoprenoid quinones in Shewanella is thought to be unique amongst Gram-negative, aerobic bacteria. In addition, methylmenaquinones were also found in Shewanella putrefaciens strains. The results demonstrate that the analysis of isoprenoid quinones offers a rapid and effective method of differentiating between some marine bacteria.

Carbonyl Sulfide Hydrolase from Thiobacillus thioparus Strain THI115 Is One of the β-Carbonic Anhydrase Family Enzymes

Carbonyl sulfide (COS) is an atmospheric trace gas leading to sulfate aerosol formation, thereby participating in the global radiation balance and ozone chemistry, but its biological sinks are not well understood. Thiobacillus thioparus strain THI115 can grow on thiocyanate (SCN(-)) as its sole energy source. Previously, we showed that SCN(-) is first converted to COS by thiocyanate hydrolase in T. thioparus strain THI115. In the present work, we purified, characterized, and determined the crystal structure of carbonyl sulfide hydrolase (COSase), which is responsible for the degradation of COS to H2S and CO2, the second step of SCN(-) assimilation. COSase is a homotetramer composed of a 23.4 kDa subunit containing a zinc ion in its catalytic site. The amino acid sequence of COSase is homologous to the β-class carbonic anhydrases (β-CAs). Although the crystal structure including the catalytic site resembles those of the β-CAs, CO2 hydration activity of COSase is negligible compared to those of the β-CAs. The α5 helix and the extra loop (Gly150-Pro158) near the N-terminus of the α6 helix narrow the substrate pathway, which could be responsible for the substrate specificity. The k(cat)/K(m) value, 9.6 × 10(5) s(-1) M(-1), is comparable to those of the β-CAs. COSase hydrolyzes COS over a wide concentration range, including the ambient level, in vitro and in vivo. COSase and its structurally related enzymes are distributed in the clade D in the phylogenetic tree of β-CAs, suggesting that COSase and its related enzymes are one of the catalysts responsible for the global sink of COS.

Paracoccus kocurii sp. nov. a Tetramethylammonium- Assimilating Bacterium

A new species of tetramethylammonium-assimilating bacteria was isolated from an activated sludge which was used for the treatment of tetramethylammonium hydroxide contained in the wastewater from semiconductor manufacturing processes. Cells of the bacteria were gram-negative, nonmotile, short rods (0.5 to 0.8 micron by 0.7 to 1.1 microns). The major respiratory quinone component of the bacteria was Q-10. The G + C content was 71 mol%. Isolates are mesophilic and assimilate methylated amines such as tetramethylammonium, trimethylamine, dimethylamine, and methylamine under neutral conditions. The isolates resemble Paracoccus species with respect to morphology but were distinguishable from the known species of the genus. We propose Paracoccus kocurii sp. nov. The type strain is strain B (= JCM 7684).

Microbial Community Analysis of Fresh and Old Microbial Biofilms on Bayon Temple Sandstone of Angkor Thom, Cambodia

The temples of Angkor monuments including Angkor Thom and Bayon in Cambodia and surrounding countries were exclusively constructed using sandstone. They are severely threatened by biodeterioration caused by active growth of different microorganisms on the sandstone surfaces, but knowledge on the microbial community and composition of the biofilms on the sandstone is not available from this region. This study investigated the microbial community diversity by examining the fresh and old biofilms of the biodeteriorated bas-relief wall surfaces of the Bayon Temple by analysis of 16S and 18S rRNA gene sequences. The results showed that the retrieved sequences were clustered in 11 bacterial, 11 eukaryotic and two archaeal divisions with disparate communities (Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Proteobacteria; Alveolata, Fungi, Metazoa, Viridiplantae; Crenarchaeote, and Euyarchaeota). A comparison of the microbial communities between the fresh and old biofilms revealed that the bacterial community of old biofilm was very similar to the newly formed fresh biofilm in terms of bacterial composition, but the eukaryotic communities were distinctly different between these two. This information has important implications for understanding the formation process and development of the microbial diversity on the sandstone surfaces, and furthermore to the relationship between the extent of biodeterioration and succession of microbial communities on sandstone in tropic region.

EFFECT OF GROWTH CONDITIONS ON THIOCYANATE DEGRADATION AND EMISSION OF CARBONYL SULFIDE BY THIOBACILLUS THIOPARUS THI115

Thiobacillus thioparus THI115 utilizes thiocyanate as its sole source of energy for growth. Carbonyl sulfide (COS) was found as an intermediate in the headspace of a sealed flask during the degradation of thiocyanate, and ammonia and sulfate were produced as the final products which slightly decreased the medium pH. In a pH-controlled TC medium, the highest degradation activity for thiocyanate was obtained at pH 6.2 and the activity was inhibited at pH 6.0. When whole gases in both liquid medium and headspace were removed from the culture vessel by forced aeration, neither growth of T. thioparus THI115 nor the degradation of thiocyanate could be observed. On the other hand, thiocyanate was degraded after a lag period of about 150 h when only the gases in the headspace were removed. These results suggest that the entire COS produced was easy to diffuse outside the cells and that the evolved COS was re-incorporated to be metabolized by cells. Despite the fact that COS is toxic to organisms, thiocyanate degradation by T. thioparus THI115 was tolerated when a total of 500 μmol of COS, which is about 17 times higher than the lethal dose of 50 for 90 min in rats, was added to the culture. T. thioparus THI115 degraded up to 60 mM thiocyanate in 130 h when supplied with sufficient oxygen and keeping the medium pH over 6.2.

Distribution of ubiquinones in Penicillium and related genera

Using high-performance liquid chromatography, the ubiquinone (Coenzyme Q) systems were determined for 335 isolates assigned to 118 species of Penicillium, and related teleomorph and anamorph genera. In the genus Eupenicillium, Q-9 occurred in all 21 species tested. In the genus Penicillium, isolates belonging to subgenera Aspergilloides, Furcatum, and Penicillium were of Q-9 except for the two species P. megasporum (Q-10) and P. asperosporum (Q-10(H2)) placed in series Megaspora. In subgenus Biverticillium, species in section Coremigena had Q-9, but Q-10(H2) was found in section Simplicia, and also in the genus Geosmithia, except for G. argillacea (Q-10). Almost all isolates in Talaromyces had Q-10(H2), but sometimes Q-10(H4), except for T. thermophilus, T. leycettanus, T. avellaneus and T. striatus, all of which had Q-10. Eladia, Penicilliopsis and Dendrosphaera had Q-9, but Q-10(H2) combined with Q-10(H4) was observed in all isolates of Trichocoma. The ubiquinone system is considered to be useful as a chemotaxonomic criterion in solving taxonomic problems in Penicillium and related fungi, and should be taken into consideration in future taxonomic treatments.