Jürgen Wiegel

Thermoanaerobacter ethanolicus gen. nov., spec. nov., a new, extreme thermophilic, anaerobic bacterium

Two strains, JW 200 and JW 201, of an extreme thermophilic, non-spore-forming anaerobic bacterium were isolated from alkaline and slightly acidic hot springs located in Yellowstone National Park. Both strains were peritrichously flagellated rods. Cell size varied from 0.5–0.8 by 4–100 μm; coccoid-shaped cells of about 1 μm in diameter frequently occurred. Division was often unequal. Spheroplast-like forms were visible at the late logarithmic growth phase. The Gram reaction was variable. The DNA base composition of the two strains was between 37 and 39 mol% guanine plus cytosine as determined by buoyant density measurements and approximately 32% by the thermal denaturation method. The main fermentation products from hexoses were ethanol and CO2. Growth occurred between 37 and 78°C and from pH 4.4 to 9.8. The name Thermoanaerobacter ethanolicus gen. nov., spec. nov. was proposed for the two, new isolates. Strain JW 200 was designated as the type strain.

Transfer of the Nitrogen-Fixing Hydrogen Bacterium Corynebacterium autotrophicum Baumgarten et al. to Xanthobacter gen. nov.

Thirty-five nitrogen-fixing, hydrogen-oxidizing bacteria, all members of Cory-nebacterium autotrophicum Baumgarten, Reh, and Schlegel 1974, and including the type strain of this species, were compared with 28 strains of coryneform bacteria by numerical taxonomy methods. The nitrogen-fixing hydrogen bacteria formed a well defined cluster; their similarity to the other strains tested was low, however. Furthermore, the chemotaxonomic characters of these strains excluded them from the coryneform bacteria. Therefore C. autotrophicum was reclassified, following the keys of Bergeys Manual of Determinative Bacteriology (8th ed.) as a species of the family Azotobacteraceae. Although taxonomically close to Beijerinckia and Derxia, the nitrogen-fixing, hydrogen-oxidizing bacteria are regarded as representing a new genus, for which we propose the name Xanthobacter. C. autotrophicum Baumgarten, Reh, and Schlegel is transferred to the new genus as Xanthobacter autotrophicus (Baumgarten et al.) comb. nov.

Distinction Between the Gram Reaction and the Gram Type of Bacteria

The elimination of the terms “gram positive, negative, and variable” and their replacement by the terms “Gram reaction positive, negative, and variable” and “Gram type positive, negative, and zero” are proposed. This action would permit a distinction between the reporting of the results of the Gram staining reaction and the placing of the bacteria into general taxonomic groups.

Clostridium thermocellum: Adhesion and sporulation while adhered to cellulose and hemicellulose

SummaryDuring growth in the presence of fibers composed of cellulose or hemicellulose, various strains of the thermophilic soil bacterium Clostridium thermocellum and several newly isolated thermophilic anaerobic soil bacteria adhered to the fibers. Attachment occurred via a fibrous ruthenium red-staining material. C. thermocellum sporulated while attached to the fibers when the pH dropped below 6.4. It is postulated that the attachment is involved in cellulose breakdown and that C. thermocellum gaines an advantage by remaining attached to its insoluble substrates when the environment is not suitable for rapid growth. The tendency to adhere to cellulose fibers was used in the purification of thermophilic cellulolytic anaerobes.

Distribution of polyamines in representative species of archaebacteria

Summary Polyamine concentrations in about 50 archaebacteria and in about 20 eubacteria were determined. No specific polyamine composition was found to be typical of all archaebacteria investigated. However, polyamine patterns were shown to be useful for their taxonomic evaluation.

A yellow affinity substance involved in the cellulolytic system ofClostridium thermocellum

Clostridium thermocellum produces a yellow substance when fermenting cellulose. This substance is attached to the cellulose particles. Cellulose with the yellow substance, obtained from cultures ofC. thermocellum, binds effectively endo-1,4-β-glucanase produced by the bacterium and was used in an affinity column for purification of the enzyme. At the beginning of fermentation of cellulose, most of the endoglucanase was bound to the yellow cellulose. As the fermentation proceeded, the enzyme appeared free in the culture fluid. The endoglucanase bound to the yellow cellulose could be extracted by distilled water from the cellulose, but not by solutions with 5 mM or higher concentrations of salts or buffers. It is proposed that the yellow substance is involved in the cellulolytic system ofC. thermocellum.

Comparative Analysis of 16S Ribosomal RNA Sequences of Thermophilic Fermentative Bacteria Isolated from Hot Spring Cyanobacterial Mats

Summary Partial 16S rRNA sequences for eight thermophilic fermentative bacteria, seven of which were isolated from cyanobacterial mats in hot springs at Yellowstone National Park, are reported. All appear to be members of the “Gram-positive low G+C subdivision”, including the Gram-negative staining Thermobacteroides acetoethylicus. T. acetoethylicus clusters tightly with two other asporogenous isolates, Thermoanaerobium brockii and Thermoanaerobacter ethanolicus, and Clostridium thermohydrosulfuricum. Three acetogenic clostridia, including two strains of Clostridium thermoautotrophicum, and Clostridium thermoaceticum, form another tight cluster. Clostridium thermosulfurogenes forms a distinct branch between these two clusters.

Butanol formation byClostridium thermosaccharolyticum at neutral pH

SummaryClostridium thermosaccharolyticum can produce up to 40 mM butanol. The formation of ethanol and butanol from starch and glucose by strain DSM 571 and by the new isolate 021 was compared. The ratios for ethanol/acetate and butanol/butyrate were higher during growth at neutral pH than at acidic pH. Butanol formation was greatly stimulated by the addition of butyrate.

16s Ribosomal DNA Sequence Analysis Confirms the Close Relationship between the Genera Xanthobacter, Azorhizobium, and Aquabacter and Reveals a Lack of Phylogenetic Coherence among Xanthobacter Species

A comparative 16S ribosomal DNA (rDNA) sequence analysis was used to investigate the phylogenetic position of members of the genus Xanthobacter. We determined 16S rDNA sequence data for the type strains of the three Xanthobacter species and five additional Xanthobacter strains. The close relationship between the genera Xanthobacter, Azorhizobium, and Aquabacter previously demonstrated by DNA-rRNA hybridization studies was confirmed. The results of our phylogenetic analysis indicate that members of the genera Xanthobacter, Azorhizobium, and Aquabacter are intermixed and that there is no clear generic cluster consisting of the Xanthobacter species. A comparison of the Xanthobacter sequences with the 16S rDNA sequences available from environmental clone studies indicated that members of this genus have not been detected by nonculturing approaches.

Numerical analysis and DNA−DNA hybridization studies on Xanthobacter and emendation of Xanthobacter flavus

Summary The taxonomic relationships among strains described as or previously tentatively assigned to the genus Xanthobacter were investigated using numerical classification, DNA base composition and DNA-DNA hybridization. Both numerical analysis and DNA-DNA hybridization studies gave similar groupings. Three main clusters were identified: the first can be equated with Xanthobacter autotrophicus , the type species of the genus. The second cluster contains the type strain of Xanthobacter flavus and several other biotin-requiring strains, leading to an emendation of the original description of X. flavus . The third cluster comprises motile strains which probably represent another species of the genus Xanthobacter .