PCR-mediated detection of the chemolithotrophic bacterium Thiobacillus cuprinus using 23S rDNA- and 16S/23S intergenic spacer region-targeted oligonucleotide primers

Proposal that the arsenite-oxidizing organisms Thiomonas cuprina and ‘Thiomonas arsenivorans’ be reclassified as strains of Thiomonas delicata, and emended description of Thiomonas delicata

The three As(III)-oxidizing members of the class Betaproteobacteria Thiomonas delicata, Thiomonas cuprina and ‘Thiomonas arsenivorans’ were isolated from mining sites in geographically distinct areas, namely Japan, Germany and France, respectively. They are all able to oxidize As(III) but only ‘T. arsenivorans’ and T. cuprina show efficient autotrophic growth with As(III) and are able to grow on a sole carbon source. These two organisms are also motile, whereas T. delicata is not. Only T. cuprina can grow autotrophically on chalcopyrite. The three strains share >99 % gene sequence similarity with each other based on their 16S rRNA genes and 16S–23S ITS regions. DNA–DNA hybridization results are above, or close to, the threshold value of 70 % recommended for the definition of bacterial species. The three taxa show very similar fatty acid profiles with differences only in five minor fatty acid components. They possess phylogenetic and chemotaxonomic similarities supporting the reclassification of these taxa as a single species. We propose that ‘T. arsenivorans’ and T. cuprina be reassigned as strains of T. delicata (type strain DSM 17897T).

Reassessment of the phylogenetic relationships of Thiomonas cuprina

The published sequence of the 16S rRNA gene of Thiomonas cuprina strain Hö5 (=DSM 5495T) (GenBank accession no. U67162) was found to be erroneous. The 16S rRNA genes from the type strain held by the DSMZ since 1990 (DSM 5495T =NBRC 102145T) and strain Hö5 maintained frozen in the Universität Regensburg for 23 years (=NBRC 102094) were sequenced and found to be identical, but to show no significant similarity to the U67162 sequence. This also casts some doubt on the previously published 5S and 23S rRNA gene sequences (GenBank accession nos U67171 and X75567). The correct 16S rRNA gene sequence showed 99.8 % identity to those from Thiomonas delicata NBRC 14566T and ‘Thiomonas arsenivorans’ DSM 16361. The properties of these three species are re-evaluated, and emended descriptions are provided for the genus Thiomonas and the species Thiomonas cuprina.

Confirmation of Thiomonas delicata (formerly Thiobacillus delicatus) as a distinct species of the genus Thiomonas Moreira and Amils 1997 with comments on some species currently assigned to the genus

The transfer of Thiobacillus delicatus to the genus Thiomonas as a distinct species, Thiomonas delicata (type strain NBRC 14566T), is confirmed by its morphological and physiological properties, DNA–DNA hybridization and the grouping of its 16S rRNA gene sequence with those of other species of the genus. An emended formal description of Thiomonas delicata is given. The status of Thiomonas cuprina DSM 5495T as a member of the genus is reconsidered.

Design and Performance of rRNA Targeted Oligonucleotide Probes for in Situ Detection and Phylogenetic Identification of Microorganisms Inhabiting Acid Mine Drainage Environments

At Iron Mountain, CA, there is an extreme occurrence of acid mine drainage (AMD). This is a result of past mining activity that has exposed a sulfide ore body to weathering and microbial activity. This study presents seven new oligonucleotide probes for the detection of microorganisms at this AMD site by fluorescent in situ hybridization. In the design of these probes we have accounted for a large body of 16S rRNA sequence data recently compiled by us. This was obtained by PCR and cloning directly from environmental DNA and was mostly represented by novel sequences. The probes were developed to include detection of novel and uncultivated organisms. This includes detection for the Thermoplasmales group, a new group of Leptospirillum, the genus Sulfobacillus, the Acidiphilium genus, Acidimicrobium and relatives, and for organisms within the delta Proteobacteria. These probes have been used to examine the abundance and distribution of organisms, including novel and uncultivated taxa, and to clarify their potential contributions to AMD production at the site. We anticipate that these probes will be useful tools for exploration of the microbiology of other natural acidic environments and bioleaching systems.

Analysis of 16S-23S rRNA intergenic spacer regions of Vibrio cholerae and Vibrio mimicus

Vibrio cholerae identification based on molecular sequence data has been hampered by a lack of sequence variation from the closely related Vibrio mimicus. The two species share many genes coding for proteins, such as ctxAB, and show almost identical 16S DNA coding for rRNA (rDNA) sequences. Primers targeting conserved sequences flanking the 3' end of the 16S and the 5' end of the 23S rDNAs were used to amplify the 16S-23S rRNA intergenic spacer regions of V. cholerae and V. mimicus. Two major (ca. 580 and 500 bp) and one minor (ca. 750 bp) amplicons were consistently generated for both species, and their sequences were determined. The largest fragment contains three tRNA genes (tDNAs) coding for tRNAGlu, tRNALys, and tRNAVal, which has not previously been found in bacteria examined to date. The 580-bp amplicon contained tDNAIle and tDNAAla, whereas the 500-bp fragment had single tDNA coding either tRNAGlu or tRNAAla. Little variation, i.e., 0 to 0.4%, was found among V. cholerae O1 classical, O1 El Tor, and O139 epidemic strains. Slightly more variation was found against the non-O1/non-O139 serotypes (ca. 1% difference) and V. mimicus (2 to 3% difference). A pair of oligonucleotide primers were designed, based on the region differentiating all of V. cholerae strains from V. mimicus. The PCR system developed was subsequently evaluated by using representatives of V. cholerae from environmental and clinical sources, and of other taxa, including V. mimicus. This study provides the first molecular tool for identifying the species V. cholerae.

Rapid species identification within two groups of closely related lactobacilli using PCR primers that target the 16S/23S rRNA spacer region

A rapid and reliable PCR-based method for distinguishing closely related species within two groups of lactobacilli is described. Primers complementary to species-specific sequences in the 16S/23S rDNA spacer regions were designed after sequencing and sequence comparison of the spacer regions of 32 strains. The strains belong to two groups of closely related Lactobacillus species; one composed of Lactobacillus curvatus, Lactobacillus graminis and Lactobacillus sake, the other of Lactobacillus paraplantarum, Lactobacillus pentosus and Lactobacillus plantarum. PCR assays with the designed primers and subsequent agarose gel analysis of the amplified fragments allowed the same species identification as the DNA/DNA hybridization procedure.

PCR-mediated detection of acidophilic, bioleaching-associated bacteria

The detection of acidophilic microorganisms from mining environments by culture methods is time consuming and unreliable. Several PCR approaches were developed to amplify small-subunit rRNA sequences from the DNA of six bacterial phylotypes associated with acidic mining environments, permitting the detection of the target DNA at concentrations as low as 10 fg.