Possible association of CUX1 gene polymorphisms with antidepressant response in major depressive disorder.

Association between response to antidepressant treatment and genetic polymorphisms was examined in two independent Japanese samples of patients with major depressive disorder (MDD). Genome-wide approach using the Illumina Human CNV370-quad Bead Chip was utilized in the analysis of the 92 MDD patients in the first sample. In all, 11 non-intergenic single-nucleotide polymorphisms with uncorrected allelic P-value <0.0001 were selected for the subsequent association analyses in the second sample of 136 MDD patients. Difference in allele distribution between responders and nonresponders were found in the second-stage sample for rs365836 and rs201522 of the CUX1 gene (P=0.005 and 0.004, respectively). The allelic P-values for rs365836 and rs201522 in both samples combined were 0.0000023 and 0.0000040, respectively. Our results provide the first evidence that polymorphisms of the CUX1 gene may be associated with response to antidepressant treatment in Japanese patients with MDD.

Microbial population dynamics during fed-batch operation of commercially available garbage composters.

Microbial populations in terms of quantity, quality, and activity were monitored during 2 months of start-up operation of commercially available composters for fed-batch treatment of household biowaste. All the reactors, operated at a waste-loading rate of 0.7 kg day(-1) (wet wt), showed a mass reduction efficiency of 88-93%. The core temperature in the reactors fluctuated between 31 degrees C and 58 degrees C due to self-heating. The pH declined during the early stage of operation and steadied at pH 7.4-9.3 during the fully acclimated stage. The moisture content was 48-63% early in the process and 30-40% at the steady state. Both direct total counts and plate counts of bacteria increased via two phases (designated phases I, II) and reached an order of magnitude of 10(11) cells g(-1) (dry wt) at the steady state. Microbial community changes during the start-up period were studied by culture-independent quinone profiling and denatured gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA. In all the reactors, ubiquinones predominated during phase I, whereas partially saturated menaquinones became predominant during phase II. This suggested that there was a drastic population shift from ubiquinone-containing Proteobacteria to Actinobacteria during the start-up period. The DGGE analysis of the bacterial community in one of the reactors also demonstrated a drastic population shift during phase I and the predominance of members of the phyla Proteobacteria and Bacteroidetes during the overall period. But this molecular analysis failed to detect actinobacterial clones from the reactor at any stage.

Application of polyhydroxyalkanoates for denitrification in water and wastewater treatment.

Application of polyhydroxyalkanoates (PHAs) and related biodegradable polymers has gained momentum in various areas of biotechnology. A promising application that started appearing in the past decade is the use of PHAs as the solid substrate for denitrification of water and wastewater. This type of denitrification, termed here "solid-phase denitrification", has several advantages over the conventional system supplemented with liquid organic substrate. PHAs serve not only as constant sources of reducing power for denitrification but also as solid matrices favorable for development of microbial films. In addition, in contrast to conventional processes, the use of PHAs has no potential risk of release of dissolved organic carbon with the resultant deterioration of effluent water quality. If the production cost of PHAs can be brought down, its application to the denitrification process will become economically more promising. A number of PHA-degrading denitrifying bacteria have been isolated and characterized from activated sludge and continuous flow-bed reactors for denitrification with PHAs. Most of these isolates have been assigned phylogenetically to members of beta-Proteobacteria, especially those of the family Comamonadaceae. The metabolic and regulatory relationships between PHA degradation and denitrification, and the interactive relationship between PHA-degrading cells and the solid surface structure are important subjects awaiting future studies, which would provide a new insight into our comprehensive understanding of the solid-phase denitrification process.

Functional and structural analyses of trichloroethylene-degrading bacterial communities under different phenol-feeding conditions: laboratory experiments.

The effects of different phenol-feeding conditions on trichloroethylene (TCE) biodegradation and bacterial population structure in an aquifer soil community were studied. The soil sample, minerals, phenol, and TCE were mixed in glass bottles, which were then incubated under three different phenol-feeding conditions. First, phenol was supplied only once at 0.2 mM (condition 0.2P); second, it was added at 2.0 mM (condition 2.0P); and third, it was periodically supplied ten times at 0.2 mM (condition 0.2PS). TCE concentrations remained stable under conditions 0.2P and 2.0P. In contrast, TCE was completely degraded under condition 0.2PS. TCE/phenol-degrading bacteria were enumerated indirectly and functionally by quantitative PCR. The low- K(s) (half saturation constant) group of phenol-degrading bacteria, exhibiting high TCE-degrading activity, yielded a 50-fold higher population under condition 0.2PS than under condition 2.0P. The bacterial community structure under condition 0.2PS was studied by denaturing gradient gel electrophoresis targeting the genes encoding 16S rRNA and the largest subunit of multicomponent phenol hydroxylase. Sequence analysis of the major bands detected indicated the predominance of the low- K(s) group of TCE/phenol-degrading bacteria belonging to beta-Proteobacteria. These results suggest that continuous supplementation with phenol at a low concentration increases the population of the low- K(s) group of TCE/phenol-degrading bacteria.

Dynamics of microcystin-degrading bacteria in mucilage of Microcystis.

To reveal the process of degradation of hepatotoxic microcystin produced in Microcystis cells during the Microcystis bloom period, we used fluorescence in situ hybridization (FISH) to analyze the population dynamics of microcystin-degrading bacteria in Microcystis mucilage. We designed and applied an oligonucleotide probe targeted to the 16S rRNA sequence of strain Y2 of a microcystin-degrading bacterium (MCD-bacterium), which was isolated from Lake Suwa, Japan. In both the 1998 and 1999 tests, FISH clearly showed that MCD-bacteria existed in the mucilage and that, when a high concentration of cell-bound microcystin was detected, MCD-bacteria exceeded 10% of the sum of bacteria hybridized with group-specific probes. The concentration of MCD-bacteria was highest in summer 1998, when a toxic species, M. viridis, was dominant. There was a high correlation between the number of MCD-bacteria in the mucilage and the concentration of cell-bound microcystin in the lake. Our results suggest that MCD-bacteria responded to changes in the concentration of microcystin and degraded the microcystin when it was released from Microcystis cells. We also analyzed changes in the bacterial community structure associated with the Microcystis colonies by using domain- and group-specific oligonucleotide probes. Changes in the concentrations of the Cytophaga/Flavobacterium group and delta-Proteobacteria, which can degrade macromolecules derived from Microcystis cells, were synchronized with changes in the concentration of Microcystis. The results not only suggest the significant role of MCD-bacteria in detoxification, but also demonstrate a possible sequence of degradation from Microcystis cells to microcystin maintained in the cell, which is then carried out by bacterial consortia in the mucilage.

Isolation and characterization of a new poly(3-hydroxybutyrate)-degrading, denitrifying bacterium from activated sludge.

A new denitrifying chemoorganotrophic bacterium capable of aerobic and anaerobic degradation of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) was isolated from activated sludge. A phylogenetic analysis based on 16S rDNA sequences indicated that the new isolate is a member of the beta subclass of the Proteobacteria and represents a distinct line of descent within the family Comamonadaceae. During denitrifying growth with 3-hydroxybutyrate, PHB, or PHBV as the sole carbon source, the isolate reduced nitrate to N2 without appreciable accumulation of nitrite and nitrous oxide as intermediate products. Kinetic analyses of the denitrification with different grades of PHBV indicated that approximately 0.7 g of PHBV was required to reduce 1 g of NO3-. A high denitrification rate (19 mg N-NO3- removed h(-1) x g(-1) dry wt of cells) was found with PHBV as the electron donor.

Toward the bioremediation of dioxin-polluted soil: structural and functional analyses of in situ microbial populations by quinone profiling and culture-dependent methods.

In order to obtain basic information toward the bioremediation of dioxin-polluted soil, microbial communities in farmland soils polluted with high concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were studied by quinone profiling as well as conventional microbiological methods. The concentration of PCDD/Fs in the polluted soils ranged from 36 to 4,980 pg toxicity equivalent quality (TEQ) g(-1) dry weight of soil. There was an inverse relationship between the levels of PCDD/Fs and microbial biomass as measured by direct cell counting and quinone profiling. The most abundant quinone type detected was either MK-6 or Q-10. In addition, MK-8, MK-8(H2), and MK-9(H8) were detected in significant amounts. Numerical analysis of quinone profiles showed that the heavily polluted soils (> or = 1,430 pg TEQ g(-1)) contained different community structures from lightly polluted soils (< or = 56 pg TEQ g(-1)). Cultivation of the microbial populations in the heavily polluted soils with dibenzofuran or 2-chlorodibenzofuran resulted in enrichment of Q-10-containing bacteria. When the heavily polluted soil was incubated in static bottles with autoclaved compost as an organic nutrient additive, the concentrations of PCDD/Fs in the soil were decreased by 22% after 3 months of incubation. These results indicate that dioxin pollution exerted a significant effect on microbial populations in soil in terms of quantity, quality, and activity. The in situ microbial populations in the dioxin-polluted soil were suggested to have a potential for the transformation of PCDD/Fs and oxidative degradation of the lower chlorinated ones thus produced.

Proposal of the genus Sphingomonas sensu stricto and three new genera, Sphingobium, Novosphingobium and Sphingopyxis, on the basis of phylogenetic and chemotaxonomic analyses.

Phylogenetic analyses of 16S rRNA gene sequences by distance matrix and parsimony methods indicated that the currently known species of the genus Sphingomonas can be divided into four clusters. Some chemotaxonomic and phenotypic differences were noted among these clusters. Three new genera, Sphingobium, Novosphingobium and Sphingopyxis, are proposed in addition to the genus Sphingomonas sensu stricto. The genus Sphingobium is proposed to accommodate Sphingomonas chlorophenolica, Sphingomonas herbicidovorans and Sphingomonas yanoikuyae. The genus Novosphingobium is proposed for Sphingomonas aromaticivorans, Sphingomonas capsulata, Sphingomonas rosa, Sphingomonas stygia, Sphingomonas subarctica and Sphingomonas subterranea. Sphingomonas macrogoltabidus and Sphingomonas terrae are reclassified in the genus Sphingopyxis. The type species of Sphingobium, Novosphingobium and Sphingopyxis are Sphingobium yanoikuyae, Novosphingobium capsulatum and Sphingopyxis macrogoltabida, respectively.

Degradation of the cyanobacterial hepatotoxin microcystin by a new bacterium isolated from a hypertrophic lake.

A bacterium capable of degrading microcystins-RR, -YR, and -LR was isolated from a hypertrophic lake. The bacterium, designated Y2 and classified phenotypically as a member of the genus Sphingomonas, was shown to be distinct phylogenetically from any established species of Sphingomonas on the basis of 16S rDNA sequencing. The bacterium was tentatively identified as Sphingomonas by manual chemotaxonomy, but 16S rRNA sequencing analysis suggests that it is in fact a new species or even a new genus. When the Y2 bacterium was added to microcystins present in culture medium, the microcystins were degraded thoroughly in 4 days. The highest degradation rates of microcystins-RR and -LR were 13 and 5.4 mg L-1 day-1, respectively. The degradation rates were strongly dependent on temperature and the maximum rate was at 30 degrees C.

Proposal of Sphingomonas wittichii sp. nov. for strain RW1T, known as a dibenzo-p-dioxin metabolizer.

A polyphasic taxonomic study was performed on Sphingomonas sp. strain RW1T. The organism was isolated from water of the River Elbe and has been known as a potent metabolizer of dibenzo-p-dioxin and its relatives. TLC of a mild alkaline hydrolysate of extractable cellular lipids of strain RW1T and type strains of 21 Sphingomonas species gave a spot of sphingoglycolipid (SGL)-1 (glucuronosyl ceramide), which is characteristic of sphingomonads. In addition, strain RW1T and type strains of three Sphingomonas species (Sphingomonas yanoikuyae, Sphingomonas terrae and Sphingomonas macrogoltabidus) showed a second spot of SGL (SGL-1') identified as galacturonosyl ceramide. The presence of SGL-1 in cellular lipids suggested that strain RW1T is a member of the genus Sphingomonas. DNA-DNA reassociation rates between strain RW1T and each type strain of 14 Sphingomonas species including Sphingomonas paucimobilis, type species for the genus, revealed that strain RW1T is independent from these species. Results of phylogenetic analysis of 16S rDNA sequences of strain RW1T and type strains of 21 named Sphingomonas species verified that strain RW1T belongs to the genus Sphingomonas. Strain RW1T could be differentiated from named species of the genus by phenotypic characteristics and has been assigned to a new species, Sphingomonas wittichii sp. nov. The type strain is DSM 6014T (= JCM 10273T = EY 4224T). DNA G+C content is 67 mol %.

Altered quinone biosynthesis in the long-lived clk-1 mutants of Caenorhabditis elegans.

Mutations in the clk-1 gene of Caenorhabditis elegans result in an extended life span and an average slowing down of developmental and behavioral rates. However, it has not been possible to identify biochemical changes that might underlie the extension of life span observed in clk-1 mutants, and therefore the function of CLK-1 in C. elegans remains unknown. In this report, we analyzed the effect of clk-1 mutation on ubiquinone (UQ(9)) biosynthesis and show that clk-1 mutants mitochondria do not contain detectable levels of UQ(9). Instead, the UQ(9) biosynthesis intermediate, demethoxyubiquinone (DMQ(9)), is present at high levels. This result demonstrates that CLK-1 is absolutely required for the biosynthesis of UQ(9) in C. elegans. Interestingly, the activity levels of NADH-cytochrome c reductase and succinate-cytochrome c reductase in mutant mitochondria are very similar to those in the wild-type, suggesting that DMQ(9) can function as an electron carrier in the respiratory chain. To test this possibility, the short side chain derivative DMQ(2) was chemically synthesized. We find that DMQ(2) can act as an electron acceptor for both complex I and complex II in clk-1 mutant mitochondria, while another ubiquinone biosynthesis precursor, 3-hydroxy-UQ(2), cannot. The accumulation of DMQ(9) and its use in mutant mitochondria indicate, for the first time in any organism, a link between the alteration in the quinone species used in respiration and life span.

Acidisphaera rubrifaciens gen. nov., sp. nov., an aerobic bacteriochlorophyll-containing bacterium isolated from acidic environments.

Four strains of aerobic, mesophilic, acidophilic bacteria that produced bacteriochlorophyll (BChl) a were isolated from acidic hot springs and mine drainage. The characteristics of the four isolates were almost identical. The isolates were strictly aerobic and chemo-organotrophic. They were gram-negative, non-motile cocci and coccobacilli, formed salmon-pink colonies on solidified media and produced BChl a and carotenoids only under aerobic growth conditions. The cells also produced small amounts of zinc-substituted BChl a when grown in the presence of 1 mM zinc sulfate. Anaerobic growth in the light was not found, but aerobic growth was stimulated by continuous incandescent illumination. The isolates grew in a pH range of 3.5-6.0, with pH optima of 4.5-5.0. A phylogenetic analysis based on 16S rDNA sequences showed that the isolates clustered in the major acidophilic group of the class Proteobacteria, which includes species of the genera Acidiphilium and Rhodopila. The anaerobic phototrophic bacterium Rhodopila globiformis was the closest relative to the new isolates (95% level of sequence similarity). The G+C content of the genomic DNA of the isolates was 69.1-69.8 mol%. On the basis of these results, it was concluded that the four isolates should be classified into a new genus and a new species, for which the name Acidisphaera rubrifaciens is proposed. The type strain is strain HS-AP3T (= JCM 10600T).

Emendation of the description of Blastomonas natatoria (Sly 1985) Sly and Cahill 1997 as an aerobic photosynthetic bacterium and reclassification of Erythromonas ursincola Yurkov et al. 1997 as Blastomonas ursincola comb. nov.

Photosynthetic properties of Blastomonas natatoria (Sly 1985) Sly and Cahill 1997, which had been recognized as being non-photosynthetic, were examined and compared with those of its close relative, the aerobic photosynthetic bacterium, Erythromonas ursincola Yurkov et al. 1997. HPLC experiments demonstrated that bacteriochlorophyll a was present in a detectable amount in the lipid extract from B. natatoria DSM 3183T as well as that from E. ursincola DSM 9006T. The puf genes, encoding the proteins of the photosynthetic reaction centre and core light-harvesting complexes, were detected by PCR from both the organisms. 16S rDNA sequence comparisons and DNA-DNA hybridization studies confirmed that B. natatoria and E. ursincola were closely related genetically in a single genus. On the basis of phenotypic, chemotaxonomic and phylogenetic data, it is proposed that the description of B. natatoria is emended as a species of aerobic photosynthetic bacteria and that E. ursincola is reclassified as Blastomonas ursincola comb. nov.

Ultrastructure of the acidophilic aerobic photosynthetic bacterium Acidiphilium rubrum.

The ultrastructure of cells of Acidiphilium rubrum, which is an acidophilic aerobic photosynthetic bacterium containing zinc-complexed bacteriochlorophyll a, was studied by electron microscopy with the rapid substitution technique. Thin-section electron microscopy indicated that any type of internal photosynthetic membranes was not present in this organism despite a relatively high content of the photopigment. The majority of cells had poly-beta-hydroxybutyrate granules and electron-dense spherical bodies identified as being polyphosphate granules. When the organism was grown chemotrophically with 0.1% FeSO(4), it produced another group of electron-dense granules that were associated with the inner part of the cytoplasmic membrane. An energy-dispersive X-ray analysis showed that these membrane-bound, electron-dense granules contained iron.

Isolation and characterization of a new denitrifying spirillum capable of anaerobic degradation of phenol.

Two kinds of phenol-degrading denitrifying bacteria, Azoarcus sp. strain CC-11 and spiral bacterial strain CC-26, were isolated from the same enrichment culture after 1 and 3 years of incubation, respectively. Both strains required ferrous ions for growth, but strain CC-26 grew better than strain CC-11 grew under iron-limited conditions, which may have resulted in the observed change in the phenol-degrading bacteria during the enrichment process. Strain CC-26 grew on phenol, benzoate, and other aromatic compounds under denitrifying conditions. Phylogenetic analysis of 16S ribosomal DNA sequences revealed that this strain is most closely related to a Magnetospirillum sp., a member of the alpha subclass of the class Proteobacteria, and is the first strain of a denitrifying aromatic compound-degrading bacterium belonging to this group. Unlike previously described Magnetospirillum strains, however, this strain did not exhibit magnetotaxis. It grew on phenol only under denitrifying conditions. Other substrates, such as acetate, supported aerobic growth, and the strain exhibited microaerophilic features.

Terminal restriction pattern analysis of 16S rRNA genes for the characterization of bacterial communities of activated sludge.

A culture-independent molecular technique using terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes was applied to the characterization of bacterial communities of activated sludge taken from different municipal sewage treatment plants. 16S rDNA fragments from the bulk DNA of sludge were amplified by PCR with a Cy5-labeled forward primer corresponding to nucleotide positions 8 to 27 and a reverse primer complementary to positions 907 to 926 in the Escherichia coli numbering system. The 16S rDNAs thus obtained were digested with tetrameric restriction enzymes and analyzed using a Pharmacia automated DNA sequencer. A preliminary study on a model DNA mixture prepared from different bacterial species showed that the fluorescence intensity of terminal fragments (T-RFs) of 16S rDNAs amplified and detected was directly proportional to the 16S rRNA gene copy number rather than the amount of genomic DNA of each species present. 16S rDNA fragments amplified from the sludges and digested with HhaI usually generated at least 60 T-RFs, among which T-RFs of around 208 bp were the most abundant regardless of the time or area sampled. Southern blot hybridization with oligonucleotide probes specific to the 5' terminal regions of the 16S rDNA of different phylogenetic groups indicated that the T-RFs of around 208 bp were derived from members of the beta subclass of the class Proteobacteria. Hybridization with a probe specific to the class Actinobacteria failed to detect any appreciable signal. These results did not agree fully with those obtained by quinone profiling. The usefulness and limitations of the T-RFLP method for monitoring bacterial population dynamics in activated sludge were discussed.

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.

Changes in quinone profiles of hot spring microbial mats with a thermal gradient

The respiratory and photosynthetic quinones of microbial mats which occurred in Japanese sulfide-containing neutral-pH hot springs at different temperatures were analyzed by spectrochromatography and mass spectrometry. All of the microbial mats that developed at high temperatures (temperatures above 68 degreesC) were so-called sulfur-turf bacterial mats and produced methionaquinones (MTKs) as the major quinones. A 78 degreesC hot spring sediment had a similar quinone profile. Chloroflexus-mixed mats occurred at temperatures of 61 to 65 degreesC and contained menaquinone 10 (MK-10) as the major component together with significant amounts of either MTKs or plastoquinone 9 (PQ-9). The sunlight-exposed biomats growing at temperatures of 45 to 56 degreesC were all cyanobacterial mats, in which the photosynthetic quinones (PQ-9 and phylloquinone) predominated and MK-10 was the next most abundant component in most cases. Ubiquinones (UQs) were not found or were detected in only small amounts in the biomats growing at temperatures of 50 degreesC and above, whereas the majority of the quinones of a purple photosynthetic mat growing at 34 degreesC were UQs. A numerical analysis of the quinone profiles was performed by using the following three parameters: dissimilarity index (D), microbial divergence index (MDq), and bioenergetic divergence index (BDq). A D matrix tree analysis showed that the hot spring mats consisting of the sulfur-turf bacteria, Chloroflexus spp., cyanobacteria, and purple phototrophic bacteria formed distinct clusters. Analyses of MDq and BDq values indicated that the microbial diversity of hot spring mats decreased as the temperature of the environment increased. The changes in quinone profiles and physiological types of microbial mats in hot springs with thermal gradients are discussed from evolutionary viewpoints.

Isoprenoid quinones as biomarkers of microbial populations in the environment.

Isoprenoid quinones are lipid molecules present in all species of respiratory and photosynthetic microorganisms and exhibit marked structural variations depending upon the microbial taxon. Taking advantage of this, quinones have been used not only as chemotaxonomic markers in microbial systematics but also as good measures of microbial populations in the environment in terms of quantity, quality, and activity. Basically, this biomarker approach, called the quinone profile method, is applicable to all environmental samples from which an absolute amount of microbial biomass > or =10(9) cells can be collected. The quinone profile method allows good measurement of both fundamental and applied aspects of ecological and environmental microbiology. In particular, numerical cluster analyses of quinone profiles are useful for monitoring microbial population shifts in an ecosystem which is not amenable to conventional culture methods and molecular techniques. The combined use of molecular techniques and the quinone profile method in this research area should provide more accurate and reliable data regarding population dynamics and community structures.

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).