Physiology and evolution of spirochetes

Diversity and plant growth promoting ability of rice root-associated bacteria in Burkina-Faso and cross-comparison with metabarcoding data

Plant-associated bacteria are essential partners in plant health and development. In addition to taking advantage of the rapid advances recently achieved in high-throughput sequencing approaches, studies on plant-microbiome interactions require experiments with culturable bacteria. A study on the rice root microbiome was recently initiated in Burkina Faso. As a follow up, the aim of the present study was to develop a collection of corresponding rice root-associated bacteria covering maximum diversity, to assess the diversity of the obtained isolates based on the culture medium used, and to describe the taxonomy, phenotype and abundance of selected isolates in the rice microbiome. More than 3,000 isolates were obtained using five culture media (TSA, NGN, NFb, PCAT, Baz). The 16S rRNA fragment sequencing of 1,013 selected isolates showed that our working collection covered four bacterial phyla (Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes) and represented 33% of the previously described diversity of the rice root microbiome at the order level. Phenotypic in vitro analysis of the plant growth promoting capacity of the isolates revealed an overall ammonium production and auxin biosynthesis capacity, while siderophore production and phosphate solubilisation were enriched in Burkholderia, Ralstonia, Acinetobacter and Pseudomonas species. Of 45 representative isolates screened for growth promotion on seedlings of two rice cultivars, five showed an ability to improve the growth of both cultivars, while five others were effective on only one cultivar. The best results were obtained with Pseudomonas taiwanensis ABIP 2315 and Azorhizobium caulinodans ABIP 1219, which increased seedling growth by 158% and 47%, respectively. Among the 14 best performing isolates, eight appeared to be abundant in the rice root microbiome dataset from previous study. The findings of this research contribute to the in vitro and in planta PGP capacities description of rice root-associated bacteria and their potential importance for plants by providing, for the first time, insight into their prevalence in the rice root microbiome.

Comparative Analysis of Brucepastera parasyntrophica gen. nov., sp. nov. and Teretinema zuelzerae gen. nov., comb. nov. (Treponemataceae) Reveals the Importance of Interspecies Hydrogen Transfer in the Energy Metabolism of Spirochetes

Most members of the family Treponemataceae (Spirochaetales) are associated with vertebrate hosts. However, a diverse clade of uncultured, putatively free-living treponemes comprising several genus-level lineages is present in other anoxic environments. The only cultivated representative to date is Treponema zuelzerae, isolated from freshwater mud. Here, we describe the isolation of strain RmG11 from the intestinal tract of cockroaches. The strain represents a novel genus-level lineage of Treponemataceae and is metabolically distinct from T. zuelzerae. While T. zuelzerae grows well on various sugars, forming acetate and H₂ as major fermentation products, strain RmG11 grew poorly on glucose, maltose, and starch, forming mainly ethanol and only small amounts of acetate and H₂. In contrast to the growth of T. zuelzerae, that of strain RmG11 was strongly inhibited at high H₂ partial pressures but improved considerably when H₂ was removed from the headspace. Cocultures of strain RmG11 with the H₂-consuming Methanospirillum hungatei produced acetate and methane but no ethanol. Comparative genomic analysis revealed that strain RmG11 possesses only a single, electron-confurcating hydrogenase that forms H₂ from NADH and reduced ferredoxin, whereas T. zuelzerae also possesses a second, ferredoxin-dependent hydrogenase that allows the thermodynamically more favorable formation of H₂ from ferredoxin via the Rnf complex. In addition, we found that T. zuelzerae utilizes xylan and possesses the genomic potential to degrade other plant polysaccharides. Based on phenotypic and phylogenomic evidence, we describe strain RmG11 as Brucepastera parasyntrophica gen. nov., sp. nov. and Treponema zuelzerae as Teretinema zuelzerae gen. nov., comb. nov. IMPORTANCE Spirochetes are widely distributed in various anoxic environments and commonly form molecular hydrogen as a major fermentation product. Here, we show that two closely related members of the family Treponemataceae differ strongly in their sensitivity to high hydrogen partial pressure, and we explain the metabolic mechanisms that cause these differences by comparative genome analysis. We demonstrate a strong boost in the growth of the hydrogen-sensitive strain and a shift in its fermentation products to acetate during cocultivation with a H₂-utilizing methanogen. Our results add a hitherto unrecognized facet to the fermentative metabolism of spirochetes and also underscore the importance of interspecies hydrogen transfer in not-obligately-syntrophic interactions among fermentative and hydrogenotrophic guilds in anoxic environments.

The influence of electrokinetic bioremediation on subsurface microbial communities at a perchloroethylene contaminated site

There is an increased interest in finding remedies for contamination in low permeability and advection-limited aquifers. A technology applicable at these sites, electrokinetic-enhanced bioremediation (EK-BIO), combines traditional bioremediation and electrokinetic technologies by applying direct current to transport bioremediation amendments and microbes in situ. The effect of this technology on the native soil microbial community has only been previously investigated at the bench scale. This research explored the influence of EK-BIO on subsurface microbial communities at a field-scale demonstration site. The results showed that, similar to the findings in laboratory studies, alpha diversity decreased and beta diversity differed temporally, based on treatment phase. Enrichments in specific taxa were linked to the bioaugmentation culture and electron donor. Overall, findings from our study, one of the first field-scale investigations of the influence of electrokinetic bioremediation on subsurface microbial communities, are very similar to bench-scale studies on the topic, suggesting good correlation between laboratory and field experiments on EK-BIO and showing that lessons learned at the benchtop are important and relevant to field-scale implementation. KEY POINTS: • Microbial community analysis of field samples validates laboratory study results • Bioaugmentation cultures and electron donors have largest effect on microbial community.

Spirochetal uveitis: Spectrum of clinical manifestations, diagnostic and therapeutic approach, final outcome and epidemiological data

PURPOSE

Analysis of cases with spirochetal uveitis related to spirochetes in a tertiary referral academic center.

METHODS

Retrospective study of patients diagnosed with uveitis attributed to Treponema pallidum, Leptospira spp. and Borrelia burgdorferi from June 1991 until December 2019.

RESULTS

A total of 57 cases of spirochetal uveitis (22 patients with T. pallidum, 26 with Leptospira spp., and 9 with B. burgdorferi) that consisted 1% of the overall number of uveitics were recorded. All these cases presented with a wide spectrum of clinical presentations (anterior uveitis, posterior uveitis, panuveitis, vasculitis, papillitis, and in some rare cases concomitant posterior scleritis). The treatment included mainly penicillin or doxycycline, while corticosteroids were administered systematically in some cases with Borrelia or Leptospira infection. The final visual outcome was favorable (> 6/10 in Snellen visual acuity) in approximately 76% of our patients.

CONCLUSION

Despite being rare, spirochetal uveitis can be detrimental for the vision and must always be included in the differential diagnosis.

Evaluating the effects of Lactobacillus animalis and Propionibacterium freudenreichii on performance and rumen and fecal measures in lactating dairy cows

Two experiments evaluated the effect of supplementation with a bacterial direct-fed microbial on performance and apparent total-tract nutrient digestion of dairy cows. In experiment 1, 30 multiparous cows (75 ± 32 d in milk) were randomly assigned to 1 of 2 treatments fed for 10 wk. All cows were fed a diet containing 23.8% starch. Treatments were top dressed to rations twice daily and consisted of a combination of Lactobacillus animalis (1 × 10⁹ cfu/d) and Propionibacterium freudenreichii (2 × 10⁹ cfu/d; LAPF) or carrier alone (CON). In experiment 2, 6 ruminally cannulated cows (123 ± 129 d in milk) were randomly assigned to a crossover design with two 6-wk periods. Cows received the same CON or LAPF treatment as in experiment 1. Cows were fed the same 23.8% starch diet as experiment 1 during wk 1 through 5 of each period, and then cows were abruptly switched to a 31.1% starch diet for wk 6. For both experiments, intake and milk yield were measured daily, and milk samples were collected weekly. In experiment 1, fecal grab samples were collected every 6 h on d 7 of experimental wk 1, 2, 4, 6, 8, and 10. Fecal consistency was scored, and fecal starch was measured in daily composite samples. Fecal composites from a subset of 7 cows per treatment were used to measure apparent total-tract nutrient digestion. In experiment 2, rumen pH was continuously recorded during wk 5 and 6. On d 7 of wk 5 (the final day of feeding the 23.8% starch ration), d 1 of wk 6 (the day of diet transition), and d 7 of wk 6 (the final day of feeding the 31.1% starch ration), rumen in situ digestion was determined. Samples of rumen fluid and feces were collected every 6 h on those days for measurement of fecal starch (composited by cow within day), rumen volatile fatty acids, and fecal pH. Rumen and fecal samples were collected at one time point on those days for microbiota assessment. In experiment 1, treatment did not affect intake, milk yield, milk composition, or fecal score. The LAPF treatment decreased fecal starch percentage and tended to increase starch digestion compared with CON, but the differences were very small (0.59 vs. 0.78% and 98.74 vs. 98.46%, respectively). Digestion of other nutrients was unaffected. In experiment 2, LAPF increased rumen pH following the abrupt switch to the high-starch diet, but milk yield was lower for LAPF compared with CON (35.7 vs. 33.2 kg/d). Contrary to the decrease in fecal starch with LAPF observed in experiment 1, fecal starch tended to be increased by LAPF following the abrupt ration change in experiment 2 (2.97 vs. 2.15%). Few effects of treatment on rumen and fecal microbial populations were detectable. Under the conditions used in our experiments, addition of the bacterial direct-fed microbials did not have a marked effect on animal performance, ruminal measures, or total-tract nutrient digestion.

Effects of different culture media on growth of Treponema spp. isolated from digital dermatitis

Digital dermatitis (DD) lesions in cattle are characterized by the presence of multiple Treponema species. Current culture media for isolating treponemes generally uses serum supplementation from different animals to target particular Treponema sp.; however, their suitability for DD Treponema isolation has not been fully determined. We studied the effect of culture media (OTEB, NOS and TYGV) and serum supplementation on mixed Treponema spp. dynamics. Bacterial growth was evaluated by direct microscopic count, optical density, wet weight and a species-specific qPCR and the correlations between these independent methods were calculated. Wet weight, optical density and bacterial count correlated best with each other. Different Treponema species performed differently under the tested culture media. T. phagedenis growth was enhanced in OTEB media supplemented with bovine fetal serum (BFS) or horse serum (HS). T. medium had lower generation time when culture media were supplemented with rabbit serum (RS). Lowest generation time for T. pedis and T. denticola were obtained in NOS media supplemented with HS and OTEB media supplemented with BFS, respectively. Detection of cystic forms observed after 5 days of culture did not differ among the culture media. Correlation between different Treponema spp. growth quantification techniques indicated that alternative quantification methods such as qPCR and wet weight could be used depending on the purpose. We conclude that effects of culture media and serum supplementation on mixed Treponema spp. communities should be taken into account when isolating a specific Treponema species.

The starlet sea anemone, Nematostella vectensis, possesses body region-specific bacterial associations with spirochetes dominating the capitulum

Sampling of different body regions can reveal highly specialized bacterial associations within the holobiont and facilitate identification of core microbial symbionts that would otherwise be overlooked by bulk sampling methods. Here, we characterized compartment-specific associations present within the model cnidarian Nematostella vectensis by dividing its morphology into three distinct microhabitats. This sampling design allowed us to uncover a capitulum-specific dominance of spirochetes within N. vectensis. Bacteria from the family Spirochaetaceae made up 66% of the community in the capitulum, while only representing 1.2% and 0.1% of the communities in the mesenteries and physa, respectively. A phylogenetic analysis of the predominant spirochete sequence recovered from N. vectensis showed a close relation to spirochetes previously recovered from wild N. vectensis. These sequences clustered closer to the recently described genus Oceanispirochaeta, rather than Spirochaeta perfilievii, supporting them as members of this clade. This suggests a prevalent and yet uncharacterized association between N. vectensis and spirochetes from the order Spirochaetales.

Exploration of deep terrestrial subsurface microbiome in Late Cretaceous Deccan traps and underlying Archean basement, India

Scientific deep drilling at Koyna, western India provides a unique opportunity to explore microbial life within deep biosphere hosted by ~65 Myr old Deccan basalt and Archaean granitic basement. Characteristic low organic carbon content, mafic/felsic nature but distinct trend in sulfate and nitrate concentrations demarcates the basaltic and granitic zones as distinct ecological habitats. Quantitative PCR indicates a depth independent distribution of microorganisms predominated by bacteria. Abundance of dsrB and mcrA genes are relatively higher (at least one order of magnitude) in basalt compared to granite. Bacterial communities are dominated by Alpha-, Beta-, Gammaproteobacteria, Actinobacteria and Firmicutes, whereas Euryarchaeota is the major archaeal group. Strong correlation among the abundance of autotrophic and heterotrophic taxa is noted. Bacteria known for nitrite, sulfur and hydrogen oxidation represent the autotrophs. Fermentative, nitrate/sulfate reducing and methane metabolising microorganisms represent the heterotrophs. Lack of shared operational taxonomic units and distinct clustering of major taxa indicate possible community isolation. Shotgun metagenomics corroborate that chemolithoautotrophic assimilation of carbon coupled with fermentation and anaerobic respiration drive this deep biosphere. This first report on the geomicrobiology of the subsurface of Deccan traps provides an unprecedented opportunity to understand microbial composition and function in the terrestrial, igneous rock-hosted, deep biosphere.

Complete genome sequence and description of Salinispira pacifica gen. nov., sp. nov., a novel spirochaete isolated form a hypersaline microbial mat

During a study of the anaerobic microbial community of a lithifying hypersaline microbial mat of Lake 21 on the Kiritimati atoll (Kiribati Republic, Central Pacific) strain L21-RPul-D2^T was isolated. The closest phylogenetic neighbor was Spirochaeta africana Z-7692^T that shared a 16S rRNA gene sequence identity value of 90% with the novel strain and thus was only distantly related. A comprehensive polyphasic study including determination of the complete genome sequence was initiated to characterize the novel isolate.

Cells of strain L21-RPul-D2^T had a size of 0.2 – 0.25 × 8–9 μm, were helical, motile, stained Gram-negative and produced an orange carotenoid-like pigment. Optimal conditions for growth were 35°C, a salinity of 50 g/l NaCl and a pH around 7.0. Preferred substrates for growth were carbohydrates and a few carboxylic acids. The novel strain had an obligate fermentative metabolism and produced ethanol, acetate, lactate, hydrogen and carbon dioxide during growth on glucose. Strain L21-RPul-D2^T was aerotolerant, but oxygen did not stimulate growth. Major cellular fatty acids were C_14:0, iso-C_15:0, C_16:0 and C_18:0. The major polar lipids were an unidentified aminolipid, phosphatidylglycerol, an unidentified phospholipid and two unidentified glycolipids. Whole-cell hydrolysates contained L-ornithine as diagnostic diamino acid of the cell wall peptidoglycan. The complete genome sequence was determined and annotated. The genome comprised one circular chromosome with a size of 3.78 Mbp that contained 3450 protein-coding genes and 50 RNA genes, including 2 operons of ribosomal RNA genes. The DNA G + C content was determined from the genome sequence as 51.9 mol%. There were no predicted genes encoding cytochromes or enzymes responsible for the biosynthesis of respiratory lipoquinones.

Based on significant differences to the uncultured type species of the genus Spirochaeta, S. plicatilis, as well as to any other phylogenetically related cultured species it is suggested to place strain L21-RPul-D2^T (=DSM 27196^T = JCM 18663^T) in a novel species and genus, for which the name Salinispira pacifica gen. nov., sp. nov. is proposed.

Genetics of motility and chemotaxis of a fascinating group of bacteria: the spirochetes

Spirochetes are a medically important and ecologically significant group of motile bacteria with a distinct morphology. Outermost is a membrane sheath, and within this sheath is the protoplasmic cell cylinder and subterminally attached periplasmic flagella. Here we address specific and unique aspects of their motility and chemotaxis. For spirochetes, translational motility requires asymmetrical rotation of the two internally located flagellar bundles. Consequently, they have swimming modalities that are more complex than the well-studied paradigms. In addition, coordinated flagellar rotation likely involves an efficient and novel signaling mechanism. This signal would be transmitted over the length of the cell, which in some cases is over 100-fold greater than the cell diameter. Finally, many spirochetes, including Treponema, Borrelia, and Leptospira, are highly invasive pathogens. Motility is likely to play a major role in the disease process. This review summarizes the progress in the genetics of motility and chemotaxis of spirochetes, and points to new directions for future experimentation.

Competitive and interactions affecting a fermentative spirochete in anaerobic chemostats

Terminal restriction fragment length polymorphism and fluorescent in situ hybridization revealed that spirochete-related populations dominated two glucose-fed methanogenic bioreactor communities at dilution rates of 0.06, 0.13, and 0.17 day(-1). At dilution rates of 0.25 and 0.50 day(-1), spirochete-related populations decreased while Clostridium-related populations increased. Isolates representing both dominant populations were obtained (Treponema R8 and Clostridium S9) and competed against each other in continuous culture. Treponema R8 out-competed Clostridium S9 at all dilution rates applied (0.17 to 1.0 day(-1)) when sufficient pantothenate was supplied in the medium. Without sufficient pantothenate, the population size of Treponema R8 was limited to 40% of the total cells. Coculture of Treponema R8 with Methanobacterium bryantii increased the cell yield of Treponema R8 and relieved the pantothenate requirement. Triculture of Treponema R8, Clostridium S9, and M. bryantii in pantothenate-deficient medium allowed Treponema R8 to outcompete Clostridium S9 in continuous culture upto a dilution rate of 0.50 day(-1). These experiments demonstrate that cofactor and vitamin requirements can affect the competitive success of a microbial species.

Widespread N-acetyl-D-glucosamine uptake among pelagic marine bacteria and its ecological implications

Dissolved free and combined N-acetyl-D-glucosamine (NAG) is among the largest pools of amino sugars in the ocean. NAG is a main structural component in chitin and a substantial constituent of bacterial peptidoglycan and lipopolysaccharides. We studied the distribution and kinetics of NAG uptake by the phosphoenolpyruvate:NAG phosphotransferase systems (PTS) in marine bacterial isolates and natural bacterial assemblages in near-shore waters. Of 78 bacterial isolates examined, 60 took up 3H-NAG, while 18 showed no uptake. No systematic pattern in NAG uptake capability relative to phylogenetic affiliation was found, except that all isolates within Vibrionaceae took up NAG. Among 12 isolates, some showed large differences in the relationship between polymer hydrolysis (measured as chitobiase activity) and uptake of the NAG, the hydrolysis product. Pool turnover time and estimated maximum ambient concentration of dissolved NAG in samples off Scripps Pier (La Jolla, Calif.) were 5.9 +/- 3.0 days (n = 10) and 5.2 +/- 0.9 nM (n = 3), respectively. Carbohydrate competition experiments indicated that glucose, glucosamine, mannose, and fructose were taken up by the same system as NAG. Sensitivity to the antibiotic and NAG structural analog streptozotocin (STZ) was developed into a culture-independent approach, which demonstrated that approximately one-third of bacteria in natural marine assemblages that were synthesizing DNA took up NAG. Isolates possessing a NAG PTS system were found to be predominantly facultative anaerobes. These results suggest the hypothesis that a substantial fraction of bacteria in natural pelagic assemblages are facultative anaerobes. The adaptive value of fermentative metabolism in the pelagic environment is potentially significant, e.g., to bacteria colonizing microenvironments such as marine snow that may experience periodic O2-limitation.

Role of Treponema denticola in periodontal diseases

Among periodontal anaerobic pathogens, the oral spirochetes, and especially Treponema denticola, have been associated with periodontal diseases such as early-onset periodontitis, necrotizing ulcerative gingivitis, and acute pericoronitis. Basic research as well as clinical evidence suggest that the prevalence of T denticola, together with other proteolytic gram-negative bacteria in high numbers in periodontal pockets, may play an important role in the progression of periodontal disease. The accumulation of these bacteria and their products in the pocket may render the surface lining periodontal cells highly susceptible to lysis and damage. T. denticola has been shown to adhere to fibroblasts and epithelial cells, as well as to extracellular matrix components present in periodontal tissues, and to produce several deleterious factors that may contribute to the virulence of the bacteria. These bacterial components include outer-sheath-associated peptidases, chymotrypsin-like and trypsin-like proteinases, hemolytic and hemagglutinating activities, adhesins that bind to matrix proteins and cells, and an outer-sheath protein with pore-forming properties. The effects of T. denticola whole cells and their products on a variety of host mucosal and immunological cells has been studied extensively (Fig. 1). The clinical data regarding the presence of T. denticola in periodontal health and disease, together with the basic research results involving the role of T. denticola factors and products in relation to periodontal diseases, are reviewed and discussed in this article.

Spirochaeta bajacaliforniensis sp. n. from a microbial mat community at Laguna Figueroa, Baja California Norte, Mexico

A new anaerobic spirochete was isolated from anaerobic muds beneath the laminated sediment in the evaporite flat at Laguna Figueroa, Baja California Norte, Mexico. The organism is a member of the stratified microbial community involved in the deposition of the laminated sediments in the lagoon. The size of the spirochete is 0.3 by 30 micrometers, with a wave amplitude of 0.5 micrometer and a wavelength of 1.25 micrometers. The periplasmic flagella have a 1-2-1 arrangement. The outer membrane of the modified Gram-negative cell wall (the sheath) is irregularly crenulated and has a sillon. The growth medium contained yeast extract, trypticase, cellobiose, sodium thioglycolate and at least 20% natural seawater. Chemically defined artificial seawater media did not support growth. Optimal growth occurred with a seawater concentration of 80% at 36 degrees C and a pH of 7.5. Glucose was fermented to acetate, ethanol, carbon dioxide and hydrogen. The guanine + cytosine content of the DNA was 50 mol %. The spirochete body reacts positively to antibodies raised against eukaryotic brain tubulin protein. On the basis of its free-living anaerobic habitat, its unique morphological and physiological characteristics and G+C ratio, it is proposed that this isolated be considered a new species and names Spirochaeta bajacaliforniensis.

Flexible community structure correlates with stable community function in methanogenic bioreactor communities perturbed by glucose

Methanogenic bioreactor communities were used as model ecosystems to evaluate the relationship between functional stability and community structure. Replicated methanogenic bioreactor communities with two different community structures were established. The effect of a substrate loading shock on population dynamics in each microbial community was examined by using morphological analysis, small-subunit (SSU) rRNA oligonucleotide probes, amplified ribosomal DNA (rDNA) restriction analysis (ARDRA), and partial sequencing of SSU rDNA clones. One set of replicated communities, designated the high-spirochete (HS) set, was characterized by good replicability, a high proportion of spiral and short thin rod morphotypes, a dominance of spirochete-related SSU rDNA genes, and a high percentage of Methanosarcina-related SSU rRNA. The second set of communities, designated the low-spirochete (LS) set, was characterized by incomplete replicability, higher morphotype diversity dominated by cocci, a predominance of Streptococcus-related and deeply branching Spirochaetales-related SSU rDNA genes, and a high percentage of Methanosaeta-related SSU rRNA. In the HS communities, glucose perturbation caused a dramatic shift in the relative abundance of fermentative bacteria, with temporary displacement of spirochete-related ribotypes by Eubacterium-related ribotypes, followed by a return to the preperturbation community structure. The LS communities were less perturbed, with Streptococcus-related organisms remaining prevalent after the glucose shock, although changes in the relative abundance of minor members were detected by morphotype analysis. A companion paper demonstrates that the more stable LS communities were less functionally stable than the HS communities (S. A. Hashsham, A. S. Fernandez, S. L. Dollhopf, F. B. Dazzo, R. F. Hickey, J. M. Tiedje, and C. S. Criddle, Appl. Environ. Microbiol. 66:4050-4057, 2000).

Characterization of fibrinolytic activities of Treponema denticola

Several fibrinolytic activities of Treponema denticola, an oral spirochete associated with gingivitis and periodontal disease, were identified and characterized following phase partitioning with the nonionic detergent Triton X-114. The apparent molecular masses of the proteases ranged from 91 to 228 kDa when analyzed in sodium dodecyl sulfate-polyacrylamide gels containing fibrinogen as the protease substrate. A qualitative analysis of zymograms showed that the proteases were highly enriched in the detergent phase, although the 91-, 173-, and 228-kDa proteases were also found in the aqueous phase. Zymograms of crude outer sheaths prepared by repeated freezing-thawing revealed that the proteases may be associated with this subcellular compartment. The proteases displayed substrate specificity towards fibrinogen, were susceptible to sulfhydryl group reagents, and had a pH optimum between 7 and 8. The similarities in their sensitivity to inhibitors, temperature stability, pH optimum, and laddered protein profiles suggest that these hydrolytic enzymes may be part of a family of oligomeric proteases that may play an important role in the invasiveness of and tissue damage caused by the spirochete.

Spirochete chemotaxis, motility, and the structure of the spirochetal periplasmic flagella

Spirochetes have a unique motility system that is characterized by flagellar filaments contained within the outer membrane sheath. Direct evidence using video microscopy has recently been obtained which indicates that these periplasmic flagella (PF) rotate in several spirochetal species. This rotation generates thrust. As shown for one spirochete, Spirochaeta aurantia, motility is driven by a proton motive force. Spirochete chemotaxis has been most thoroughly studied in S. aurantia. This spirochete exhibits three distinct behaviours, runs of smooth swimming, reversals and flexing. These behaviours are modulated by addition of attractants such that S. aurantia swims towards higher concentrations of attractants in a spatial gradient. Unlike the prototypical bacterium, Escherichia coli, chemotaxis in S. aurantia involves fluctuations in membrane potential. The PF of a number of spirochetes have been examined in considerable detail. For most species, the PF filaments are complex, consisting of an assembly of several different polypeptides. There are several antigenically related core polypeptides surrounded by an outer layer consisting of a different polypeptide. Borrelia burgdorferi and Spirochaeta zuelzerae represent exceptions where the filaments are composed of a single major polypeptide species. The genes encoding the filament polypeptides from several spirochete species have been cloned and analysed. Apparently, the outer layer polypeptides of S. aurantia, Treponema pallidum and Serpulina hyodysenteriae are transcribed from sigma-70-like promoters, whereas the core polypeptide genes are transcribed from sigma-28-like promoters. A gene encoding the hook polypeptide in Treponema phagedenis has been cloned and analysed. The product of this gene shows significant similarity to the E. coli hook protein, FlgE, and homologs have been identified in T. pallidum and B. burgdorferi.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose catabolism by Spirochaeta thermophila RI 19.B1

Spirochaeta thermophila RI 19.B1 (DSM 6192) fermented glucose to lactate, acetate, CO2, and H2 with concomitant formation of cell material. The cell dry mass yield was 20.0 g/mol of glucose. From the fermentation balance data and knowledge of the fermentation pathway, a YATP of 9.22 g of dry mass per mol of ATP was calculated for pH-uncontrolled batch-culture growth on glucose in a mineral medium. Measurement of enzyme activities in glucose-grown cells revealed that glucose was taken up by a permease and then subjected to ATP-dependent phosphorylation by a hexokinase. Glucose-6-phosphate was further metabolized to pyruvate through the Embden-Meyerhof-Parnas pathway. The phosphoryl donor for phosphofructokinase activity was PPi rather than ATP. This was also found for the type strain of S. thermophila, Z-1203 (DSM 6578). PPi was probably formed by pyrophosphoroclastic cleavage of ATP, with recovery of the resultant AMP by the activity of adenylate kinase. All other measured kinase activities utilized ATP as the phosphoryl donor. Pyruvate was further metabolized to acetyl coenzyme A with concomitant production of H2 and CO2 by pyruvate synthase. Lactate was also produced from pyruvate by a fructose-1,6-diphosphate-insensitive lactate dehydrogenase. Evidence was obtained for the transfer of reducing equivalents from the glycolytic pathway to hydrogenase to produce H2. No formate dehydrogenase or significant ethanol-producing enzyme activities were detected.

Phylogenetic analysis of the spirochetes

The 16S rRNA sequences were determined for species of Spirochaeta, Treponema, Borrelia, Leptospira, Leptonema, and Serpula, using a modified Sanger method of direct RNA sequencing. Analysis of aligned 16S rRNA sequences indicated that the spirochetes form a coherent taxon composed of six major clusters or groups. The first group, termed the treponemes, was divided into two subgroups. The first treponeme subgroup consisted of Treponema pallidum, Treponema phagedenis, Treponema denticola, a thermophilic spirochete strain, and two species of Spirochaeta, Spirochaeta zuelzerae and Spirochaeta stenostrepta, with an average interspecies similarity of 89.9%. The second treponeme subgroup contained Treponema bryantii, Treponema pectinovorum, Treponema saccharophilum, Treponema succinifaciens, and rumen strain CA, with an average interspecies similarity of 86.2%. The average interspecies similarity between the two treponeme subgroups was 84.2%. The division of the treponemes into two subgroups was verified by single-base signature analysis. The second spirochete group contained Spirochaeta aurantia, Spirochaeta halophila, Spirochaeta bajacaliforniensis, Spirochaeta litoralis, and Spirochaeta isovalerica, with an average similarity of 87.4%. The Spirochaeta group was related to the treponeme group, with an average similarity of 81.9%. The third spirochete group contained borrelias, including Borrelia burgdorferi, Borrelia anserina, Borrelia hermsii, and a rabbit tick strain. The borrelias formed a tight phylogenetic cluster, with average similarity of 97%. THe borrelia group shared a common branch with the Spirochaeta group and was closer to this group than to the treponemes. A single spirochete strain isolated fromt the shew constituted the fourth group. The fifth group was composed of strains of Serpula (Treponema) hyodysenteriae and Serpula (Treponema) innocens. The two species of this group were closely related, with a similarity of greater than 99%. Leptonema illini, Leptospira biflexa, and Leptospira interrogans formed the sixth and most deeply branching group. The average similarity within this group was 83.2%. This study represents the first demonstration that pathogenic and saprophytic Leptospira species are phylogenetically related. The division of the spirochetes into six major phylogenetic clusters was defined also by sequence signature elements. These signature analyses supported the conclusion that the spirochetes represent a monophylectic bacterial phylum.

Biochemical properties of the outer membrane of Treponema denticola

The outer membranes (OMs) from serovars a, b, and c of Treponema denticola, originally isolated from periodontal patients, were prepared. Dialysis of the OMs against 20 mM MgCl2 yielded the aggregable (A) and the nonaggregable (NA) moieties of the OMs. The absence of muramic acid, adenosine triphosphatase, hexokinase, and nucleic acid as well as electron microscopy indicated that the OM preparations were homogeneous. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the A and NA moieties of the OMs showed approximately 25 Coomassie brilliant blue R-250 stain-positive bands or 47 silver-stained polypeptides. The relative molecular masses ranged between 14 and 97 kDa. The electrophoretic polypeptide profiles of the A and NA moieties shared many similarities among serovars a, b, and c. However, they exhibited variation in the overall pattern, intensity, or location of the polypeptide stained zones. This was especially true for serovar b. Two-dimensional electrophoretic studies showed an excess of 100 silver-stained spots with isoelectric points of 4.6 to 7.0 and relative molecular masses in the 14- to 97-kDa range. The OMs contained simple proteins, glycoproteins, and lipoproteins. The NA moieties of the OMs contained 4 to 6, 10 to 12, and 4 to 6 glycopeptides as well as two, seven, and two lipoprotein bands for serovars a, b, and c, respectively. The A moieties of the OMs showed 7 to 9, 11 to 13 and 5 to 6 glycopeptides as well as four, five, and three lipoprotein bands for serovars a, b, and c, respectively. Lipopolysaccharide was detected in the OMs of the three serovars following removal of proteins with proteinase K, pronase and silver staining of sodium dodecyl sulfate-polyacrylamide gels, or removal of lipopolysaccharide from the OMs by hot phenol extraction. The 66- and 53-kDa bands were present in serovars b and c, while a band with a relative molecular mass of 45 kDa was present only in serovar c. Endotoxin-like activity was also shown in the OMs of the three serovars by the Limulus amebocyte clotting assay and the chick embryo lethality test. This is the first report on selected biochemical properties of the OM macromolecules of three known serovars of T. denticola.

Chemotaxis mutants of Spirochaeta aurantia

Five Spirochaeta aurantia chemotaxis mutants were isolated. One mutant (the che-101 mutant) never reversed, one (the che-200 mutant) flexed predominantly, two (the che-300 and che-400-1 mutants) exhibited elevated reversal frequencies, and one (the che-400 mutant) exhibited chemotactically unstimulated behavior similar to that of the wild-type strain. The che-101 and che-400 mutants were essentially nonchemotactic, whereas the che-200, che-300, and che-400-1 mutants showed impaired chemotactic responses. Protein methylation in response to attractant addition appeared normal in all of the mutants. Compared with the wild type, all of the mutants exhibited significantly altered membrane potential responses to the attractant xylose.

The role of spirochetes in periodontal disease

The spirochetal accumulation in subgingival plaque appears to be a function of the clinical severity of periodontal disease. It is not known how many different spirochetal species colonize the plaque, but based upon size alone, there are small, intermediate-sized, and large spirochetes. Four species of small spirochetes are cultivable, and of these, T. denticola has been shown to possess proteolytic and keratinolytic enzymes as well as factors or mechanisms which suppress lymphocyte blastogenesis and inhibit fibroblast and polymorphonuclear leukocyte (PMNL) function. All of these attributes could contribute to periodontal tissue insult. Yet independent of these potential virulence mechanisms, the overgrowth of spirochetes can be clinically useful if simply interpreted as indicating the result of tissue damage. In this case, the spirochetes would be indicators of disease and could be easily monitored by microscopic examination of plaque, or possibly by the measurement of benzoyl-DL-arginine-2-naphthylamide (BANA) hydrolytic activity in the plaque.

Motility and chemotaxis of Spirochaeta aurantia: computer-assisted motion analysis

A computer program has been designed to study behavior in populations of Spirochaeta aurantia cells, and this program has been used to analyze changes in behavior in response to chemoattractants. Three kinds of behavior were distinguished: smooth swimming, flexing, and reversals in direction of swimming after a short pause (120 ms). Cell populations exposed to chemoattractants spent, on average, 66, 33, and 1% of the time in these modes, respectively. After the addition of a chemoattractant, behavior was modified transiently--smooth swimming increased, flexing decreased, and reversals were suppressed. After addition of D-xylose (final concentration, 10 mM), the adaptation time (the time required for the populations to return to the unmodified behavior) for S. aurantia was 1.5 to 2.0 min. A model to explain the behavior of S. aurantia and the response of cells to chemoattractants is described. This model includes a coordinating mechanism for flagellar motor operation and a motor switch synchronizing device.

Inhibition of superoxide production in human polymorphonuclear leukocytes by oral treponemal factors

The inhibition of superoxide (O2-) production by human peripheral blood polymorphonuclear leukocytes (PMNs) in the presence of oral treponemes, their cellular components, and their culture supernatants was investigated. Superoxide production was inhibited 56% by a 25-microgram/ml phenol extract of a human clinical isolate. Inhibition by culture supernatants of both the clinical isolate and a reference strain was related to the bacterial phase of growth and viability, though inhibition also persisted in the decline phase. Inhibition of superoxide production was not evident when either opsonized or nonopsonized whole spirochetes were reacted with PMNs. The suppressive activity depended, therefore, on the treponemes either being disrupted or growing and releasing the inhibitory factor into the culture medium. These results suggest that oral treponemes possess factors which interfere with the activity of PMNs and thereby alter the inflammatory process in the diseased periodontal pocket.

Role ofCristispira sp. and other bacteria in the chitinase and chitobiase activities of the crystalline style ofCrassostrea virginica (Gmelin)

Activity was found for chitinase and chitobiase in the crystalline styles of American oysters (Crassostrea virginica Gmelin) collected from the Chesapeake Bay (Maryland, USA). The oysters were maintained in tanks on natural food from a constant flow of unfiltered estuarine water. Chitinase and chitobiase specific activities were compared with total, viable, and chitinoclastic bacterial counts andCristispira counts. Regression analyses revealed that one correlation, chitobiase vsCristispira, was significant (P < 0.05). Several oysters were fed chitin in the presence or absence of chloramphenicol. Although no chitinoclasts were present in the antibiotic-treated oysters, the treatment means did not differ significantly (P > 0.05) for either chitinase or chitobiase activity. In several cases with both chitin-fed and naturally fed oysters, enzyme activity was found when noCristispira were present. The results of the investigations suggest that the oyster produces chitinase and chitobiase endogenously.

Isolation of the outer membrane and characterization of the major outer membrane protein from Spirochaeta aurantia

The outer membrane of Spirochaeta aurantia was isolated after cells were extracted with sodium lauryl sarcosinate and was subsequently purified by differential centrifugation and KBr isopycnic gradient centrifugation. The purified outer membrane was obtained in the form of carotenoid-containing vesicles. Four protein species with apparent molecular weights of 26,000 (26K), 36.5K, 41K, and 48.5K were readily observed as components of the vesicles. The 36.5K protein was the major polypeptide and constituted approximately 90% of the outer membrane protein observed on sodium dodecyl sulfate-polyacrylamide gels. Under mild denaturing conditions the 36.5K major protein exhibited an apparent molecular weight of approximately 90,000. This, together with the results of protein cross-linking studies, indicates that the 36.5K polypeptide has an oligomeric conformation in the native state. Reconstitution of solubilized S. aurantia outer membrane into lipid bilayer membranes revealed the presence of a porin, presumably the 36.5K protein, with an estimated channel diameter of 2.3 nm based on the measured single channel conductance of 7.7 nS in 1 M KCl.

Properties of lactate dehydrogenase in a psychrophilic marine bacterium

Lactate dehydrogenase (EC 1.1.1.27) from Vibrio marinus MP-1 was purified 15-fold and ammonium activated. The optimum pH for pyruvate reduction was 7.4. Maximum lactate dehydrogenase activity occurred at 10 to 15 degrees C, and none occurred at 40 degrees C. The crude-extract enzyme was stable between 15 and 20 degrees C and lost 50% of its activity after 60 min at 45 degrees C. The partially purified enzyme was stable between 8 and 15 degrees C and lost 50% of its activity after 60 min at 30 degrees C. The thermal stability of lactate dehydrogenase was increased by mercaptoethanol, with 50% remaining activity at 42 degrees C.

Enzymatic activities for interconversion of purines in spirochetes

Enzymatic activities that catalyze the interconversion of purines and purine derivatives were detected in cell extracts of Spirochaeta aurantia, Spirochaeta stenostrepta, Treponema succinifaciens, and Treponema denticola. Phosphoribosyltransferase activities present in cell extracts of each of the four spirochete species functioned in the conversion of adenine, hypoxanthine, and guanine to AMP, IMP, and GMP, respectively. Nucleotidase activities in the extracts mediated the formation of nucleosides from nucleotides. The conversion of adenosine, inosine, and guanosine to the respective purine bases was catalyzed by nucleoside phosphorylase and, in some instances, by nucleoside hydrolase activities. Guanine deaminase activity was found in both S. aurantia and S. stenostrepta, whereas adenosine deaminase activity was detected only in S. aurantia. Adenine deaminase activity in T. succinifaciens extracts was sensitive to O2 and was relatively resistant to heating. Our results indicate that the four species of spirochetes studied possess a broad spectrum of purine interconversion enzymes. It is suggested that these enzymes may function in metabolic processes important for the survival of spirochetes in nutrient-poor natural environments.

Properties of acetate kinase isozymes and a branched-chain fatty acid kinase from a spirochete

Spirochete MA-2, which is anaerobic, ferments glucose, forming acetate as a major product. The spirochete also ferments (but does not utilize as growth substrates) small amounts of l-leucine, l-isoleucine, and l-valine, forming the branched-chain fatty acids isovalerate, 2-methylbutyrate, and isobutyrate, respectively, as end products. Energy generated through the fermentation of these amino acids is utilized to prolong cell survival under conditions of growth substrate starvation. A branched-chain fatty acid kinase and two acetate kinase isozymes were resolved from spirochete MA-2 cell extracts. Kinase activity was followed by measuring the formation of acyl phosphate from fatty acid and ATP. The branched-chain fatty acid kinase was active with isobutyrate, 2-methylbutyrate, isovalerate, butyrate, valerate, or propionate as a substrate but not with acetate as a substrate. The acetate kinase isozymes were active with acetate and propionate as substrates but not with longer-chain fatty acids as substrates. The acetate kinase isozymes and the branched-chain fatty acid kinase differed in nucleoside triphosphate and cation specificities. Each acetate kinase isozyme had an apparent molecular weight of approximately 125,000, whereas the branched-chain fatty acid kinase had a molecular weight of approximately 76,000. These results show that spirochete MA-2 synthesizes a branched-chain fatty acid kinase specific for leucine, isoleucine, and valine fermentation. It is likely that a phosphate branched-chain amino acids is also synthesized by spirochete MA-2. Thus, in spirochete MA-2, physiological mechanisms have evolved which serve specifically to generate maintenance energy from branched-chain amino acids.

API ZYM system for identification of Bacteroides spp., Capnocytophaga spp., and spirochetes of oral origin

A total of 80 oral strains of Bacteroides gingivalis, B. asaccharolyticus, B. melaninogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, Capnocytophaga, Treponema denticola, and T. vincentii were characterized with the API ZYM system for 19 enzyme activities. Comparison of anaerobic and aerobic incubation with nine reference strains of these organisms showed no important differences. The key differential tests for black-pigmented Bacteroides strains and treponemes of oral origin were trypsin, alpha-glucosidase, and N-acetyl-beta-glucosaminidase. All Capnocytophaga strains produced distinctive aminopeptidase activities but varied in their glycosidic capabilities. The presence of a trypsin-like activity in B. gingivalis, T. denticola, and a group of Capnocytophaga strains may contribute to tissue destruction in periodontal disease.

Chemotaxis of Spirochaeta aurantia: involvement of membrane potential in chemosensory signal transduction

The effects of valinomycin and nigericin on sugar chemotaxis in Spirochaeta aurantia were investigated by using a quantitative capillary assay, and the fluorescent cation, 3,3'-dipropyl-2,2'-thiodicarbocyanine iodide was used as a probe to study effects of chemoattractants on membrane potential. Addition of a chemoattractant, D-xylose, to cells in either potassium or sodium phosphate buffer resulted in a transient membrane depolarization. In the presence of valinomycin, the membrane potential of cells in potassium phosphate buffer was reduced, and the transient membrane depolarization that resulted from the addition of D-xylose was eliminated. Although there was no detectable effect of valinomycin on motility, D-xylose taxis of cells in potassium phosphate buffer was completely inhibited by valinomycin. In sodium phosphate buffer, valinomycin had little effect on membrane potential or D-xylose taxis. Nigericin is known to dissipate the transmembrane pH gradient of S. aurantia in potassium phosphate buffer. This compound did not dissipate the membrane potential or the transient membrane depolarization observed upon addition of D-xylose to cells in either potassium or sodium phosphate buffer. Nigericin did not inhibit D-xylose taxis in either potassium or sodium phosphate buffer. This study indicates that the membrane potential but not the transmembrane pH gradient of S. aurantia is somehow involved in chemosensory signal transduction.

Branched-chain amino acid fermentation by a marine spirochete: strategy for starvation survival

An anaerobic marine spirochete (strain MA-2) fermented glucose and formed ethanol, acetic acid, CO(2), and H(2) as end products. The organism required carbohydrates as growth substrates. Amino acids did not support the growth of strain MA-2. However, when the spirochete was grown in media containing branched-chain amino acids and glucose, significant quantities of 4- and 5-carbon branched-chain volatile fatty acids were formed in addition to products of glucose fermentation. Smaller quantities of branched-chain alcohols were also formed under these conditions. The spirochete converted l-valine, l-isoleucine, and l-leucine to isobutyric, 2-methylbutyric, and isovaleric acids, respectively. CO(2) formation accompanied each of these conversions. Spirochete MA-2 did not require branched-chain amino acids for growth, but these compounds could serve as sole sources of nitrogen for the organism. In addition, the survival of starving cells (no growth substrate available) of spirochete MA-2 was prolonged significantly when l-valine, l-isoleucine, and l-leucine were present in starvation media. Starving cells fermented these amino acids, forming adenosine 5'-triphosphate and branched-chain fatty acids. Our findings indicate that energy derived from amino acid fermentation allows the spirochete to survive periods of growth substrate starvation. Apparently, dissimilation of branched-chain amino acids can provide this bacterium with maintenance energy for cell functions not related to growth. In its natural environment spirochete MA-2 may catabolize branched-chain amino acids as a strategy for survival when growth substrates are not available.

Distribution of superoxide dismutase, catalase, and peroxidase activities among Treponema pallidum and other spirochetes

Representative members of Spirochaetales were surveyed for their content of superoxide dismutase (SOD), catalase, and peroxidase activities. Only Leptospira exhibited peroxidase activity. Obligately anaerobic cultivable Treponema and Spirochaeta possessed no SOD or peroxidative capabilities. Upon polyacrylamide gel electrophoresis, Spirochaeta aurantia, Borrelia hermsi, and five Leptospira biflexa serovars showed SOD activity associated with one electrophoretic band which was inhibited by H2O2, suggesting that they were iron-containing dismutases. These spirochetes could be distinguished by differences in relative mobilities of their SODs. SOD activity, but not catalase activity, was induced aerobically in S. aurantia. All Leptospira interrogans serovars and two L. biflexa serovars lacked significant SOD activity. These SOD-deficient strains of Leptospira, with one exception, possessed high levels of catalase activity. The Nichols strain of virulent Treponema pallidum possessed SOD and catalase activities, but lacked peroxidase activity. The SOD in T. pallidum exhibited two electrophoretic bands containing copper and zinc, and its relative mobility was identical to that of purified rabbit SOD. Immunization of sheep with purified rabbit SOD resulted in antiserum which inhibited both rabbit SOD and T. pallidum SOD assayed by spectrophotometric analysis or activity staining following polyacrylamide gel electrophoresis. In agarose gel diffusion, precipitin lines of identity were observed between purified rabbit SOD and cell extracts of T. pallidum. These data indicated that the SOD activity detected in T. pallidum was host derived.

Relationship between proton motive force and motility in Spirochaeta aurantia

The effects of various metabolic inhibitors on the motility of Spirochaeta aurantia were investigated. After 15 min in sodium arsenate buffer, 90% of cells remained motile even though adenosine triphosphate levels dropped from 5.6 to 0.1 nmol/mg (dry weight) of cells. After 70 min in sodium arsenate, 5% of cells were motile. Addition of phenazine methosulfate plus ascorbate at this time resulted in motility of 95% of cells, but adenosine triphosphate levels remained at 0.1 nmol/mg of cell dry weight. Carbonyl cyanide-m-chlorophenyl hydrazone rapidly (within 1 min) and completely inhibited motility of metabolizing cells in potassium phosphate buffer. However, after 15 min in the presence of carbonyl cyanide m-chlorophenyl hydrazone the cellular adenosine triphosphate level was 3.4 nmol/mg (dry weight) of cells, and the rate of oxygen uptake was 44% of the rate measured in the absence of carbonyl cyanide m-chlorophenyl hydrazone. Cells remained motile under conditions where either the electrical potential or the pH gradient across the membrane of S. aurantia was dissipated. However, if both gradients were simultaneously dissipated, motility was rapidly inhibited. This study indicates that a proton motive force, in the form of either a transmembrane electrical potential or a transmembrane pH gradient, is required for motility in S. aurantia. Adenosine triphosphate does not appear to directly activate the motility system in this spirochete.

Treponema bryantii sp. nov., a rumen spirochete that interacts with cellulolytic bacteria

A saccharolytic spirochete that associated and interacted with cellulolytic bacteria was isolated from bovine rumen fluid. Isolation was accomplished by means of a procedure involving serial dilution of a sample of rumen fluid into a cellulose-containing agar medium. Clear zones appeared within the medium as a result of cellulose hydrolysis by rumen bacteria. The saccharolytic spirochete and a cellulolytic bacterium later identified as a strain of Bacteroides succinogenes were isolated from the clear zones. The spirochete did not utilize cellulose, but grew in coculture with the cellulotytic bacterium in cellulose-containing media. When cocultured in these media the spirochete used, as fermentable substrates, soluble sugars released from cellulose by the cellulolytic bacterium. In cellulose-containing agar medium the spirochete enhanced cellulose breakdown by the B. succinogenes strain. Electron microscopy showed that the helical spirochete cells possessed an outer sheath, a protoplasmic cylinder, and two periplasmic fibrils. Under a CO2 atmosphere, in a reduced medium containing inorganic salts, rumen fluid, glucose, and NaHCO3, the spirochete grew to a final density of 1.9 X 10(9) cells/ml. Succinate, acetate, and formate were products of the fermentation of glucose by growing cells. CO2 (HCO3-), branched short-chain fatty acids, folic acid, biotin, niacinamide, thiamine, pyridoxal, and a carbohydrate were required for growth of the spirochete. The results of this study indicated that the rumen spirochete represents a new species of Treponema. It is proposed that the new species be named Treponema bryantii.

Optimum concentration of dissolved oxygen for the survival of virulent Treponema pallidum under conditions of low oxidation-reduction potential

A maintenance medium with a low oxidation-reduction (redox) potential, when gently bubbled with 5% oxygen in nitrogen or with air for various periods of time, gave a range of dissolved oxygen concentrations between 1.6 and 5.8 micrograms/l. Virulent Treponema pallidum (Nichols strain) inoculated into these media were assayed 24 and 48 hours later for motility and virulence and were compared with samples taken at zero time. Virulent T. pallidum survived best in the presence of 2.4 micrograms/l dissolved oxygen over a 48-hour period, which corresponded to a gaseous mixture of 3% oxygen in nitrogen. Higher concentrations of oxygen did not give significantly different results from anaerobic conditions over this period. Thus, until it can be grown in vitro, T. pallidum would appear to be a microaerophilic bacterium.

Phospholipid composition of gliding bacteria: oral isolates of Capnocytophaga compared with Sporocytophaga

The distribution of acetone-soluble (neutral glycolipid) and acetone-insoluble (phospholipid isoprenoids) lipids in oral isolates of gram-negative gliding bacteria of the genus Capnocytophaga was compared with those in a non-host-related gliding bacterium, Sporocytophaga myxococcoides. The acetone-soluble material accounted for 34 to 55% of the extracted lipids; the remainder was acetone-insoluble material. The major phospholipid was phosphatidylethanolamine (67%), with lesser amounts of lysophosphatidylethanolamine and several unidentified phosphate-containing compounds. Capnocytophaga also contained significant amounts of an ornithine-amino lipid.

Treponema succinifaciens sp. nov., an anaerobic spirochete from the swine intestine

The morphology, the general physiological characteristics, and the energy-yielding metabolism of an obligately anaerobic spirochete isolated from the colon of a swine were studied. Electron microscopy showed that the helical spirochetal cells possessed an outer sheath, a protoplasmic cylinder, and 4 periplasmic fibrils in a 2-4-2 arrangement. The spirochete grew in an atmosphere of N2 in prereduced media containing a carbohydrate, NaHCO3, rumen fluid, yeast extract, peptone, L-cysteine, and inorganic salts. The spirochete fermented carbohydrates and required substrate amounts of CO2 (HCO3-) for growth. Amino acids were not fermented. Major fermentation products of cells growing with glucose as the substrate and in the presence of CO2 were acetate, formate, succinate, and lactate. Small amounts of 2,3-butanediol, pyruvate, and acetoin were also formed. Determinations of enzymatic activities in cell extracts, and of radioactivity in products formed by growing cells from [1-14C]glucose, indicated that this sugar was dissimilated to pyruvate via the Embden-Meyerhof pathway. The spirochetes used a coliform-type clastic reaction to metabolize pyruvate. Determinations of radioactivity in products formed from [14C]NaHCO3 indicated that CO2 was assimilated and used in succinate production. The guainine + cytosine content of the DNA was 36 mol %. This study indicates that this intestinal spirochete represents a new species of Treponema. It is proposed that the new species be named Treponema succinifaciens.

Mucopolysaccharidase of Treponema pallidum

Treponema pallidum (Nichols strain) exhibited mucopolysaccharidase activity. Acidic mucopolysaccharides were broken down more rapidly by viable treponemes than by heat-inactivated treponemes or membrane filtrates of treponemal suspensions. Ouchterlony immunodiffusion demonstrated the occurrence of antibodies to the hyaluronidase-like enzyme within syphilitic sera. After intratesticular inoculation of 2 x 10(7) to 6 x 10(7) treponemes, these anti-mucopolysaccharidase antibodies were detected between 9 and 35 days postinoculation. In addition, acidic mucopolysaccharides were present in the serum of infected animals 9 and 16 days postinoculation. Immune serum that contained antibodies to the mucopolysaccharidase restricted treponemal breakdown of acidic mucopolysaccharides. It has been previously demonstrated that immune rabbit serum contains a factor that blocks attachment of T. pallidum (Nichols strain) to cultured mammalian cells. This factor was effectively absorbed by prior incubation with bovine hyaluronidase. It is postulated that T. pallidum attaches to acidic mucopolysaccharides on the surface of cultured cells through the mucopolysaccharidase enzyme at the surface of the organisms. These findings are discussed in terms of the histopathogenesis of T. pallidum with applications to the healing immune response.

Helix handedness of Leptospira interrogans as determined by scanning electron microscopy

Representative serovars and strains of the seven genetic groups of Leptospira interrogans, and two previously studied serovars, were all found to form exclusively right-handed helices as determined by scanning electron microscopy. No change in handedness occurred in cells grown in a minimal medium (Tween-80 albumin) compared to cells grown in a rich medium (rabbit serum). The right-handedness of the organisms was related to the evolution, cell wall structure, and the mechanism of motility of L. interrogans.

Axial filament involvement in the motility of Leptospira interrogans

Motility mutants of Leptospira interrogans serovar illini were isolated and analyzed by dark-field and electron microscopy. Mutants were obtained by screening for small colonies after nitrosoguanidine treatment. One class of mutants did not have hook- or spiral-shaped ends. In addition, the axial filaments from these mutants were not coiled. An analysis of revertants of two of the mutants in this class indicated that the mutations were pleiotropic with respect to motility, hook- and spiral-shaped ends, and axial filament coiling. We conclude that the axial filaments and the hook- and spiral-shaped ends are involved in L. interrogans motility.

Purification and properties of acetate kinase from Acholeplasma laidlawii

Acetate kinase (EC 2.7.2.1) was purified from Acholeplasma laidlawii cytoplasm by a combination of ammonium sulfate fractionation, gel filtration, diethylaminoethyl-cellulose chromatography, and affinity chromatography on 8-(6-aminohexylamino)-adenosine 5'-triphosphate conjugated to Sepharose 4B. The enzyme was composed of polypeptide chains of about 50,000 molecular weight as estimated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Under nondenaturating conditions, apparent molecular weights between 64,000 and 130,000 were obtained, depending upon mainly the ionic strength of the test solution. The enzyme had a narrow specificity for phosphate acceptor acids, whereas both purine and pyrimidine nucleoside triphosphates were suitable phosphate donors. Na(+) and K(+) inhibited both acetyl phosphate and adenosine 5'-triphosphate synthesis, and the latter was also inhibited by high concentrations of adenosine 5'-diphosphate and acetyl phosphate. This substrate inhibition was partially abolished by 0.5 M NaCl. The enzyme catalyzed the independent adenosine 5'-diphosphate<-->adenosine 5'-triphosphate and acetate<-->acetyl phosphate exchanges. The rate of the latter was enhanced by the addition of cosubstrate Mg(2+)-adenosine 5'-triphosphate. The high affinity for substrates, except for acetate, indicated that under physiological conditions the direction of the enzymic reaction favors adenosine 5'-triphosphate synthesis. Thus, a mechanism for adenosine 5'-triphosphate generation in mycoplasmas is suggested.

Enzymatic degradation of H2O2 by Leptospira

The enzymes responsible for reducing H2O2 were surveyed in 49 strains of Leptospira by using semiquantitative assays for catalase and peroxidase. The survey revealed a differential distribution of catalase and peroxidase activities between the two leptospiral complexes. The pathogenic Leptospira interrogans strains gave strong catalase and weak or negative peroxidase reactions. Conversely, the nonpathogenic Leptospira biflexa strains gave strong peroxidase and negative or weak catalase reactions. An intermediate group of four L. biflexa strains, which were isolated from mammals, fell into the high peroxidase, low or negative catalase group. One water isolate, H-23, gave strong reactions for both enzymes and was examined for virulence and in vitro growth parameters. Results indicate metabolic differences between pathogens and water forms in their abilities to reduce H2O2.

Microtubules in prokaryotes

Longitudinally aligned microtubules, about 220 A in diameter, have been seen in the protoplasmic cylinders of the following spirochetes (symbiotic in the hindguts of dry-wood and subterranean termites): Pillotina sp., Diplocalyx sp., Hollandina sp. They are also present in a gliding bacterium from Pterotermes occidentis. These microtubules are probably composed of tubulin, as determined by staining with fluorescent antibodies to tubulin and comigration with authentic tubulin on acrylamide gels. Treponema reiteri lack tubulin by these same criteria. These observations support the hypothesis of the symbiotic origin of cilia and flagella from certain spirochetes.