Wolfgang Ludwig

Bio: Wolfgang Ludwig is an academic researcher from Ludwig Maximilian University of Munich. The author has contributed to research in topics: Phylogenetic tree & Molecular probe. The author has an hindex of 22, co-authored 36 publications receiving 2361 citations. Previous affiliations of Wolfgang Ludwig include Henkel.

Bacterial phylogeny based on 16S and 23S rRNA sequence analysis

Abstract: Molecular phylogeny increasingly supports the understanding of organismal relationships and provides the basis for the classification of microorganisms according to their natural affiliations. Comparative sequence analysis of ribosomal RNAs or the corresponding genes currently is the most widely used approach for the reconstruction of microbial phylogeny. The highly and less conserved primary and higher order structure elements of rRNAs document the history of microbial evolution and are informative for definite phylogenetic levels. An optimal alignment of the primary structures and a careful data selection are prerequisites for reliable phylogenetic conclusions. rRNA based phylogenetic trees can be reconstructed and the significance of their topologies evaluated by applying distance, maximum parsimony and maximum likelihood methods of phylogeny inference in comparison, and by fortuitous or directed resampling of the data set. Phylogenetic trees based on almost equivalent data sets of bacterial 23S and 16S rRNAs are in good agreement and their overall topologies are supported by alternative phylogenetic markers such as elongation factors and ATPase subunits. Besides their phylogenetic information content, the differently conserved primary structure regions of rRNAs provide target sites for specific hybridization probes which have been proven to be powerful tools for the identification of microbes on the basis of their phylogenetic relationships.

Dominating role of an unusual magnetotactic bacterium in the microaerobic zone of a freshwater sediment.

Abstract: A combination of polymerase chain reaction-assisted rRNA sequence retrieval and fluorescent oligonucleotide probing was used to identify in situ a hitherto unculturable, big, magnetotactic, rod-shaped organism in freshwater sediment samples collected from Lake Chiemsee. Tentatively named "Magnetobacterium bavaricum," this bacterium is evolutionarily distant from all other phylogenetically characterized magnetotactic bacteria and contains unusually high numbers of magnetosomes (up to 1,000 magnetosomes per cell). The spatial distribution in the sediment was studied, and up to 7 x 10 active cells per cm were found in the microaerobic zone. Considering its average volume (25.8 +/- 4.1 mum) and relative abundance (0.64 +/- 0.17%), "M. bavaricum" may account for approximately 30% of the microbial biovolume and may therefore be a dominant fraction of the microbial community in this layer. Its microhabitat and its high content of sulfur globules and magnetosomes suggest that this organism has an iron-dependent way of energy conservation which depends on balanced gradients of oxygen and sulfide.

Halobacillus gen. nov., with Descriptions of Halobacillus litoralis sp. nov. and Halobacillus trueperi sp. nov., and Transfer of Sporosarcina halophila to Halobacillus halophilus comb. nov.

Abstract: Two moderately halophilic, gram-positive, heterotrophic bacterial strains were isolated from hypersaline sediments of the Great Salt Lake in Utah. These two strains, designated SL-4T (T = type strain) and SL-5T, were motile, spore-forming, strictly aerobic rods which contained peptidoglycan of the Orn-D-Asp type in their vegetative cell walls. The guanine-plus-cytosine contents of the DNAs of strains SL-4T and SL-5T were 42 and 43 mol%, respectively. A detailed investigation of the phenotypic and phylogenetic characteristics of these organisms revealed that each isolate represents a new species that is closely related to Sporosarcina halophila, a moderately halophilic, spore-forming coccus. Phylogenetic data indicate that there is only a distant relationship between Sporosarcina halophila and Sporosarcina ureae, the type species of the genus Sporosarcina. The sequences of the 16S rRNA genes of strain SL-4T and Salinicoccus roseus DSM 5351 were determined. We propose that a new genus, Halobacillus, should be created; this genus includes Halobacillus halophilus (formerly Sporosarcina halophila) as the type species, as well as Halobacillus litoralis DSM 10405T (= SL-4T) and Halobacillus trueperi DSM 10404T (= SL-5T).

Transfer of Brevibacterium divaricatum DSM 20297T, “Brevibacterium flavum” DSM 20411, “Brevibacterium lactofermentum” DSM 20412 and DSM 1412, and Corynebacterium lilium DSM 20137T to Corynebacterium glutamicum and Their Distinction by rRNA Gene Restriction Patterns

Abstract: The results of DNA-DNA hybridization and chemotaxonomic studies indicated that the glutamic acid producers Brevibacterium divaricatum DSM 20297T (T=type strain), "Brevibacterium flavum" DSM 20411, "Brevibacterium lactofermentum" DSM 1412 and DSM 20412, Corynebacterium lilium DSM 20137T, and Corynebacterium glutamicum DSM 20300T and DSM 20163 are members of the same species. It is proposed that all of these strains should be classified in the species Corynebacterium glutamicum. Another glutamic acid-producing strain, Corynebacterium callunae DSM 20147T, was not related at the species level to C. glutamicum and should retain its separate species status. A restriction fragment length polymorphism analysis in which oligonucleotides targeted against conserved regions of 16S and 23S rRNA genes were used as hybridizing probes distinguished the individual strains. This method may be a helpful tool for strain identification.

The GTPase superfamily: conserved structure and molecular mechanism

Abstract: GTPases are conserved molecular switches, built according to a common structural design. Rapidly accruing knowledge of individual GTPases--crystal structures, biochemical properties, or results of molecular genetic experiments--support and generate hypotheses relating structure to function in other members of the diverse family of GTPases.

Uniting the classification of cultured and uncultured bacteria and archaea using 16S rRNA gene sequences

Abstract: Publicly available sequence databases of the small subunit ribosomal RNA gene, also known as 16S rRNA in bacteria and archaea, are growing rapidly, and the number of entries currently exceeds 4 million. However, a unified classification and nomenclature framework for all bacteria and archaea does not yet exist. In this Analysis article, we propose rational taxonomic boundaries for high taxa of bacteria and archaea on the basis of 16S rRNA gene sequence identities and suggest a rationale for the circumscription of uncultured taxa that is compatible with the taxonomy of cultured bacteria and archaea. Our analyses show that only nearly complete 16S rRNA sequences give accurate measures of taxonomic diversity. In addition, our analyses suggest that most of the 16S rRNA sequences of the high taxa will be discovered in environmental surveys by the end of the current decade.

Energetics of syntrophic cooperation in methanogenic degradation.

Abstract: Fatty acids and alcohols are key intermediates in the methanogenic degradation of organic matter, e.g., in anaerobic sewage sludge digestors or freshwater lake sediments. They are produced by classical fermenting bacteria for disposal of electrons derived in simultaneous substrate oxidations. Methanogenic bacteria can degrade primarily only one-carbon compounds. Therefore, acetate, propionate, ethanol, and their higher homologs have to be fermented further to one-carbon compounds. These fermentations are called secondary or syntrophic fermentations. They are endergonic processes under standard conditions and depend on intimate coupling with methanogenesis. The energetic situation of the prokaryotes cooperating in these processes is problematic: the free energy available in the reactions for total conversion of substrate to methane attributes to each partner amounts of energy in the range of the minimum biochemically convertible energy, i.e., 20 to 25 kJ per mol per reaction. This amount corresponds to one-third of an ATP unit and is equivalent to the energy required for a monovalent ion to cross the charged cytoplasmic membrane. Recent studies have revealed that syntrophically fermenting bacteria synthesize ATP by substrate-level phosphorylation and reinvest part of the ATP-bound energy into reversed electron transport processes, to release the electrons at a redox level accessible by the partner bacteria and to balance their energy budget. These findings allow us to understand the energy economy of these bacteria on the basis of concepts derived from the bioenergetics of other microorganisms.