Human dendritic cells infected by Listeria monocytogenes: induction of maturation, requirements for phagolysosomal escape and antigen presentation capacity

An important feature of microbial infections is the ability of the microorganisms to interfere with and modulate the induction of host immune reactions. However, little is known about the effects of broad host range pathogens such as Listeria monocytogenes on similar cell types in different hosts. Here we examine the effects of the human and animal pathogen L. monocytogenes on human dendritic cells (DC) since this type of cells is essential for the initiation of immune responses. Listeria are phagocytosed efficiently by immature human DC and the bacteria escape from the phagolysosome quickly. Lack of the pore-forming activity of listeriolysin, which was found to be essential for the vacuolar escape of this bacterium in other cell types, retarded but did not prevent egress from the vacuole. Treatment of cultures of immature DC with L. monocytogenes resulted in rapid changes in morphology and cellular constitution followed by maturation of the DC. This could be judged by the appearance of maturation-specific cell surface markers. Antigen presentation to CD4 T cells was apparently not impaired by the infection. These results are in clear contrast to results obtained previously in the mouse system (Guzman et al., Mol. Microbiol. 1996. 20: 119 - 126; Darji et al., Eur. J. Immunol. 1997. 27: 1696 - 1703.).

Pharyngeal carriage of group C and group G streptococci and acute rheumatic fever in an Aboriginal population

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) represent an autoimmune response to group A streptococcal pharyngitis. In the Aboriginal population of the Northern Territory of Australia, some of the highest rates of ARF in the world have been reported, although throat carriage rates of group A streptococcus in this population are extremely low and symptomatic group A streptococcal pharyngitis is uncommon; by contrast, carriage rates of group C and G streptococci are high. Therefore, we questioned the involvement of these groups in ARF and showed that they have the potential to elicit an autoimmune response that may trigger ARF.

Selective depletion of heat shock protein 70 (Hsp70) activates a tumor-specific death program that is independent of caspases and bypasses Bcl-2

Heat shock protein 70 is an antiapoptotic chaperone protein highly expressed in human breast tumors and tumor cell lines. Here, we demonstrate that the mere inhibition of its synthesis by adenoviral transfer or classical transfection of antisense Hsp70 cDNA (asHsp70) results in massive death of human breast cancer cells (MDA-MB-468, MCF-7, BT-549, and SK-BR-3), whereas the survival of nontumorigenic breast epithelial cells (HBL-100) or fibroblasts (WI-38) is not affected. Despite the apoptotic morphology as judged by electron microscopy, the asHsp70-induced death was independent of known caspases and the p53 tumor suppressor protein. Furthermore, Bcl-2 and Bcl-X(L), which protect tumor cells from most forms of apoptosis, failed to rescue breast cancer cells from asHsp70-induced death. These results show that tumorigenic breast cancer cells depend on the constitutive high expression of Hsp70 to suppress a transformation-associated death program. Neutralization of Hsp70 may open new possibilities for treatment of cancers that have acquired resistance to therapies activating the classical apoptosis pathway.

ABRF-98SEQ: Evaluation of peptide sequencing at high sensitivity

The ABRF-98SEQ sample was the 11th in a series of amino acid sequencing studies performed by the Protein Sequence Research Group of the Association of Biomolecular Resource Facilities. This study was designed to aid participants' laboratories in determining their abilities to analyze the amino acid sequence of a peptide at high sensitivity using Edman degradation, mass spectrometry (MS), or both. ABRF-98SEQ is a 17-amino acid synthetic peptide (IFDDEIEEVQALYPTER) that resembles a typical tryptic peptide. It was distributed at the 2.8-pmol level. The sample was sent dried in a microfuge tube accompanied by instructions on solubilizing the sample and by a survey form. Including tentative calls, the correct sequence was obtained by 16% of the responding participants, compared with only 6% in the 1997 study when the low-level peptide was a minor component of a mixture. This increase probably reflects the purity of ABRF-98SEQ. A secondary factor in the increase in correct calls may be the larger number of respondents this year reporting that they perform sequence analysis at the 1- to 10-pmol level. Most respondents who obtained the correct sequence used a combination of Edman sequencing and molecular weight determination by MS. Overall, the accuracy and sensitivity of peptide sequencing by Edman degradation continue to improve and are clearly aided by the use of MS for molecular weight determination. Although peptide sequencing by MS is not yet routinely practiced by the participating laboratories, results of this study indicate that MS-derived sequence data, when properly interpreted, are valuable for correcting, completing, or corroborating sequence assignments derived by Edman.

Identification of SopE2 from Salmonella typhimurium, a conserved guanine nucleotide exchange factor for Cdc42 of the host cell

Salmonella typhimurium translocates effector proteins into host cells via the SPI1 type III secretion system to induce responses such as membrane ruffling and internalization by non-phagocytic cells. Activation of the host cellular RhoGTPase Cdc42 is thought to be a key event during internalization. The translocated Salmonella protein SopE is an activator for Cdc42. Because SopE is absent from most S. typhimurium strains it remains unclear whether all S. typhimurium strains rely on activation of Cdc42 to invade host cells. We have identified SopE2, a translocated effector protein common to all S. typhimurium strains. SopE2 is a guanine nucleotide exchange factor for Cdc42 and shows 69% sequence similarity to SopE. Analysis of S. typhimurium mutants demonstrated that SopE2 plays a role in recruitment of the actin-nucleating Arp2/3 complex to the membrane ruffles and in efficient host cell invasion. Transfection experiments showed that SopE2 is sufficient to activate host cellular Cdc42, to recruit the actin-nucleating Arp2/3 complex and to induce actin cytoskeletal rearrangements and internalization. In conclusion, as a result of SopE2 all S. typhimurium strains tested have the capacity to activate Cdc42 signalling inside host cells which is important to ensure efficient entry.

Interaction of Salmonella enterica serotype Typhimurium with dendritic cells is defined by targeting to compartments lacking lysosomal membrane glycoproteins

Dendritic cells (DCs) play a central role in the generation of acquired immunity to infections by pathogenic microorganisms. Salmonella enterica serotype Typhimurium is known to survive and proliferate intracellularly within macrophages and nonphagocytic cells, but no data exist on how this pathogen interacts with DCs. In this report, we show the capacity of serotype Typhimurium to survive within the established mouse DC line CB1. In contrast to the case for the macrophage model, the compartments of DCs containing serotype Typhimurium are devoid of lysosomal membrane glycoproteins and the PhoPQ two-component regulatory system is not essential for pathogen intracellular survival.

AgfD, the checkpoint of multicellular and aggregative behaviour in Salmonella typhimurium regulates at least two independent pathways

The regulatory programme of multicellular behaviour in Salmonella typhimurium is determined by mutations in the agfD promoter. AgfD has already been identified to regulate the extracellular matrix associated with the multicellular morphotype composed of thin aggregative fimbriae (agf). To detect additional components contributing to the multicellular morphotype in S. typhimurium, we constructed a mutant in agfD, the positive transcriptional regulator of the agfBA(C) operon encoding for fimbrial subunit proteins. The agfD mutant lacked any form of multicellular behaviour as shown by analysis at the macroscopic and microscopic level. In contrast, the agfBA mutant unable to form thin aggregative fimbriae still maintained long-range intercellular adhesion. Promoter and expression analysis revealed that the genes downstream of agfD agfEFG most likely did not contribute to the remaining aggregative behaviour. Screening of transcriptional fusions for agfD dependency uncovered adrA, a homologue of yaiC in Escherichia coli. Environmental factors regulating adrA correspond to the regulation of thin aggregative fimbriae. AdrA is a putative transmembrane protein with a C-terminal GGDEF domain of unknown function although it is present in over 50 bacterial proteins. AdrA mutant cells, which still formed thin aggregative fimbriae with all binding characteristics, exhibited community behaviour but, unlike the wild type, lacked long-range intercellular adhesion. An agfBA adrA double mutant behaved like the agfD mutant. Therefore, it was concluded that agfD regulates at least two independent pathways contributing to the multicellular morphotype in S. typhimurium.

Two distinct pathways for the invasion of Streptococcus pyogenes in non-phagocytic cells

Adherence to and invasion of epithelial cells represent important pathogenic mechanisms of Streptococcus pyogenes. A fibronectin-binding surface protein of S. pyogenes, Sfbl protein, has been implicated in both adherence and invasion processes. Invasion of Sfbl-containing strains has been suspected to be responsible for the failure of antibiotics treatment to eradicate S. pyogenes. In this study, we tested the adherence and invasion properties of two well-characterized clinical isolates: A40, which expresses Sfbl; and A8, which is Sfbl negative and is unable to bind fibronectin. In strain A40, Sfbl was the main factor required for attachment and invasion by using fibronectin as a bridging molecule and the alpha5beta1 integrin as cellular receptor. The uptake process was characterized by the generation of large membrane invaginations at the bacteria-cell interface without evidence of actin recruitment or cellular injury. A40 cells were located in phagosomes and, only 24 h after infection, a consistent part of the bacterial population reached the cytoplasm. In contrast, uptake of strain A8 required major rearrangements of cytoskeletal proteins underneath attached bacteria. In A8, a proteinaceous moiety was involved, which does not interact with alpha5beta1 or need any known bridging molecule. Bacterial attachment stimulated elongation and massive recruitment of neighbouring microvilli, which fused to surround streptococcal chains. They led to the generation of large pseudopod-like structures, which engulfed bacteria that were rapidly released and replicated in the cytoplasm. The identification of two completely different uptake pathways reported here provided further evidence regarding the diversity of S. pyogenes isolates and might contribute towards understanding the pathogenesis and persistence of S. pyogenes.

Modulation of host immune responses stimulated by Salmonella vaccine carrier strains by using different promoters to drive the expression of the recombinant antigen

We evaluated whether immune responses stimulated by Salmonella vaccine carriers can be modulated by using different promoters to drive antigen expression. Mice were orally immunized with strains transfected with plasmids carrying beta-galactosidase (beta-gal) under the control of either a constitutive or an in vivo-activated promoter. While alpha-gal-reactive IgG1, IgG2a, IgG2b and IgG3 were detected in sera of mice immunized with Salmonella expressing constitutively beta-gal, higher titers dominated by IgG2a and IgG2b were detected in sera when the in vivo-activated promoter was used. beta-gal-specific proliferative responses of spleen-derived CD4+ T lymphocytes were similar in both groups. However, CD4+ T lymphocytes from mice immunized with the constitutive promoter secreted IL-4, IL-5, IL-6, IL-10 and IFN-gamma (Th1/Th2 pattern), whereas CD4+ cells mainly secreted IFN-gamma (Th1 pattern) when the second construct was used. The spleens of all immunized mice contained beta-gal-reactive CD8+ CTL precursors. The vaccine prototypes were tested for their capacity to control seeding and/or development within the lung of an intravenously delivered aggressive fibrosarcoma transfected with beta-gal. Reduced metastasis and significantly increased mean survival times were observed in all vaccinated mice. However, protection was improved when the carrier expressed beta-gal upon infection (80 % versus 50% survival, p < 0.05).

Vectors to achieve selective expression of vaccine antigens within eukaryotic cells using Salmonella spp. as carrier strains

A set of expression vectors was constructed which allows the expression of recombinant antigens under the control of Salmonella typhi promoters that are selectively activated after infection of eukaryotic cells. The pUC18Not derivatives contain a promoter downstream of the early transcriptional terminator from phage T7 and followed by a multiple cloning site, whereas the pBluescript II S/K derivatives contain the ribosomal RNA T(1) transcriptional terminator and also the strong translation signals of the Escherichia coli atpE gene. The expression cassettes are flanked by NotI or PacI sites to simplify their subcloning where required. The resulting vectors were validated using the S1 subunit of pertussis toxin as a model antigen and Salmonella typhimurium aroA SL7207 as a carrier. The S1 subunit was efficiently expressed by recombinant Salmonella within Henle 407 cells.

Flagella modulate the multicellular behavior of Salmonella typhimurium on the community level

Salmonella typhimurium strains MAE52 and MAE32 display a constitutive multicellular morphotype mediated by the expression of the agfD operon. In those strains, the role of flagella in the formation of various modes of multicellular behavior was investigated. Flagella were not required for the formation of the multicellular morphotype (rdar) on plates. However, visual examination showed that the global behavior of the bacterial community on air-liquid, surface-liquid or cell-cell-liquid interfaces changed in the absence of flagella. No differences in the local cell-cell interactions were observed at the microscopic level. Using Western blot analysis, no co-regulation of flagella and thin aggregative fimbriae, an extracellular component of the multicellular morphotype, was observed either on plates or in standing culture. In a mutant lacking flagella and thin aggregative fimbriae, the contribution of the latter to the multicellular morphotype was dominant. We concluded that independently regulated genes can act in an additive fashion to confer a pronounced multicellular behavior.

Highly resistant Burkholderia pseudomallei small colony variants isolated in vitro and in experimental melioidosis

Burkhloderia pseudomallei is the causative agent of melioidosis, a disease in which treatment failures and relapses are common. This study reports on slow growing B. pseudomallei 'small colony variants' (SCVs), isolated either in vitro after exposure to ceftazidime, ciprofloxacin or gentamicin or from the spleen and liver in a mouse model of melioidosis after treatment with ceftazidime. Interestingly, SCVs isolated by either method or antimicrobial agent showed a significant increase in the minimal inhibitory concentrations of various unrelated classes of antimicrobial agents. B. pseudomallei SCVs did not differ from their parental strains in standard biochemical profiles, nor by pulsed field gel electrophoresis or electron microscopy. Although the SCV phenotype was stable throughout numerous passages on antibiotic-free solid media, revertants with the parental colony morphology and, most importantly, with the parental susceptibility pattern occurred. These revertants led to rapid overgrowth of SCVs in liquid media without added antibiotics. Future studies will have to determine the clinical relevance of B. pseudomallei SCVs especially in treatment failure and relapse of infection.

Fc-mediated nonspecific binding between fibronectin-binding protein I of Streptococcus pyogenes and human immunoglobulins

Fibronectin-binding protein I (SfbI) from Streptococcus pyogenes plays a key role in bacterial adhesion to, and invasion of, eukaryotic cells. In addition, SfbI exhibits a considerable potential as mucosal adjuvant and can trigger polyclonal activation of B cells. Here, we report that SfbI is also capable of binding human IgG in a nonimmune fashion. SfbI was reactive with IgG1, IgG2, IgG3, and IgG4 isotypes (type IIo IgG-binding profile). The affinity constant (Kd) of the SfbI-IgG interaction was in the range of 1-2 x 10(-5) M. Further studies demonstrated that the SfbI binding was mediated by the Fc component of the IgG molecule. Experiments performed using purified recombinant proteins spanning different domains of SfbI showed that the IgG-binding activity was restricted to the fibronectin-binding domains, and in particular to the fibronectin-binding repeats. Finally, the presence of recombinant SfbI resulted in an impairment of both phagocytosis of IgG-coated RBCs and Ab-dependent cell cytotoxicity by macrophages. These results demonstrated for the first time that, in addition to its major role during the colonization process, SfbI may also favor bacterial immune evasion after the onset of the infection by interfering with host clearance mechanisms.

Small-colony variants of Pseudomonas aeruginosa in cystic fibrosis

In the context of chronic lung infection due to Pseudomonas aeruginosa in cystic fibrosis (CF), attention has been focused on the presence of the most common mucoid phenotype. In this study, the presence of small-colony variants (SCVs) of P. aeruginosa in respiratory tract specimens from patients with CF was investigated, and the clinical conditions predisposing to SCVs were analyzed. P. aeruginosa SCVs were isolated from 33 of 86 P. aeruginosa-positive CF patients over a 2-year period. Fast-growing revertants with larger surface colonies could be isolated from SCV populations. Electron microscopy revealed no significant difference in cell size or morphology. MICs of a broad range of antipseudomonas agents for SCVs were two- to eightfold higher than values for revertants. Recovery of SCVs was correlated with parameters revealing poor lung function and was significantly associated with daily inhalation of tobramycin or colistin.

The EspD protein of enterohemorrhagic Escherichia coli is required for the formation of bacterial surface appendages and is incorporated in the cytoplasmic membranes of target cells

The formation of EspA-containing surface appendages in pathogenic Escherichia coli strains, both enteropathogenic E. coli (EPEC) and Shiga toxin-producing E. coli strains, is essential for critical events in the infective process, e.g., localized bacterial adherence to host cells with formation of microcolonies and induction of attaching and effacing lesions. It has been reported that EPEC mutants deficient in the production of EspD, which is encoded by the esp operon, are unable to accumulate actin underneath adherent bacteria but exhibit an attachment similar to that of the wild type. Here, we report the construction and characterization of an in-frame espD deletion mutant of the enterohemorrhagic E. coli (EHEC) strain EDL933. In contrast to what was observed in EPEC mutants, the EDL933 espD mutant not only lacked the capacity to accumulate actin but also exhibited an impaired attachment to HeLa cells. The synthesis of the EspD protein was also essential for the formation of EspA-containing filaments. Finally, localization studies demonstrated that the EspD protein is transferred to the cytoplasm and integrated into the cytoplasmic membranes of infected cells. These results help to elucidate the underlying molecular events in infections caused by EHEC.

Isolation of a temperate bacteriophage encoding the type III effector protein SopE from an epidemic Salmonella typhimurium strain

Salmonella typhimurium employs the specialized type III secretion system encoded in pathogenicity island 1 (SPI1) to translocate effector proteins into host cells and to modulate host cell signal transduction. The SPI1 type III system and the effector proteins are conserved among all salmonellae and are thought to be acquired by horizontal gene transfer. The genetic mechanisms mediating this horizontal transfer are unknown. Here, we describe that SopE, a SPI1-dependent translocated effector protein, is present in relatively few S. typhimurium isolates. We have isolated a temperate phage that encodes SopE. Phage morphology and DNA hybridization, as well as partial sequence information, suggest that this phage (SopEPhi) is a new member of the P2 family of bacteriophages. By lysogenic conversion this phage can horizontally transfer genes between different S. typhimurium strains. Strikingly, most of the isolates harboring SopEPhi belong to the small group of epidemic strains of S. typhimurium that have been responsible for a large percentage of human and animal salmonellosis and have persisted for a long period of time. Our data suggest that horizontal transfer of type III dependent effector proteins by lysogenic infection with bacteriophages (lysogenic conversion) may provide an efficient mechanism for fine-tuning the interaction of Salmonella spp. with their hosts.

Heat-inactivation of plasmid-encoded CI857 repressor induces gene expression from Ind- lambda prophage in recombinant Escherichia coli

We have observed significant cell lysis upon temperature up-shift of recombinant Escherichia coli cultures harboring CI857-repressed lambda-based expression vectors. This event, that becomes evident about 30-40 min after the heat shock, takes place when using the lambda promoter system in Ind- lysogenic strains, but not in others commonly employed for recombinant gene expression. These results strongly suggest that the thermosensitive CI857 repressor, encoded by the expression vector, competes with CI Ind- molecules for binding to the prophage operator region, allowing for expression of lytic genes from the integrated Ind- viral genome upon temperature up-shift. Transcription of viral lytic genes does not include unspecific expression of a reporter sulA::lacZ gene fusion carried in the prophage genome. These results prompt, however, to carefully evaluate the limitations of expression systems based on pL/pR-CI857 in bacterial strains modified through lambda Ind- gene transfer vehicles.

The actin-based motility of intracellular Listeria monocytogenes is not controlled by small GTP-binding proteins of the Rho- and Ras-subfamilies

In this study, we analyzed whether the actin-based motility of intracellular Listeria monocytogenes is controlled by the small GTP-binding proteins of the Rho- and Ras-subfamilies. These signalling proteins are key regulatory elements in the control of actin dynamics and their activity is essential for the maintenance of most cellular microfilament structures. We used the Clostridium difficile toxins TcdB-10463 and TcdB-1470 to specifically inactivate these GTP-binding proteins. Treatment of eukaryotic cells with either of these toxins led to a dramatic breakdown of the normal actin cytoskeleton, but did not abrogate the invasion of epithelial cells by L. monocytogenes and had no effect on the actin-based motility of this bacterial parasite. Our data indicate that intracellular Listeria reorganize the actin cytoskeleton in a way that circumvents the control mechanisms mediated by the members of the Rho- and Ras-subfamilies that can be inactivated by the TcdB-10463 and TcdB-1470 toxins.

Characterization of a murine model of melioidosis: comparison of different strains of mice

Melioidosis is an infectious disease caused by the saprophytic gram-negative rod Burkholderia pseudomallei. The aim of this study was to establish and characterize a murine model of melioidosis to provide a basis for further investigations on the pathogenesis of the disease. After intravenous infection with B. pseudomallei, C57BL/6 mice were found to be significantly more resistant than BALB/c mice. There was a marked organotropism of B. pseudomallei for the spleen and liver in both strains of mice, with the highest bacterial load in the spleen. Electron microscopic investigations of the spleen clearly demonstrated intracellular replication within membrane-bound phagosomes. Electron micrographs of the liver provided evidence that B. pseudomallei-containing phagosomes in hepatocytes fuse with lysosomes, leading to degradation of bacteria. In both strains of mice, the course of infection was highly dependent on the infective dose and the bacterial strain used, ranging from death within a few days to death after several weeks. In comparison with BALB/c mice, the bacterial counts in C57BL/6 mice were decreased 12 h after infection, which is suggestive of an innate immune mechanism against B. pseudomallei in this early phase of infection contributing to the lower susceptibility of C57BL/6 mice. BALB/c mice developed a more pronounced lymphopenia, granulocytosis, and splenomegaly at a lower infective dose compared to C57BL/6 mice. Analysis of the antibody response against B. pseudomallei 11 days after infection revealed a significantly higher immunoglobulin G2A (IgG2a)/IgG1 ratio in C57BL/6 mice than in BALB/c mice, indicating that a T helper type 1 immune response is associated with resistance to infection with B. pseudomallei.

Induction of cellular immunity to a mycobacterial antigen adsorbed on lamellar particles of lactide polymers

Microspheres prepared from synthetic, biodegradable poly (L-lactide) [PLA] and copolymers of lactide and glycolide such as poly (DL lactide co-glycolide) [PLG] have been widely investigated for controlled delivery of encapsulated vaccine antigens. In this study we describe novel lamellar microparticles produced from PLA to which protein antigens can be adsorbed. These particles when administered to mice, induced strong Th1-type T cell responses to the adsorbed 38 kDa protein antigen from M. tuberculosis characterised by high levels of Interferon-gamma. In addition to proteins, we were also able to adsorb synthetic peptides resulting in specific T cell proliferation. Induction of strong cellular immunity together with the versatility of antigen adsorption to these particles should make such lamellae a useful tool to deliver protective antigens from intracellular pathogens.

Sulfitobacter mediterraneus sp. nov., a new sulfite-oxidizing member of the alpha-Proteobacteria

Analysis of PCR products of 16S rDNA of 680 isolates from Mediterranean Sea mesocosm experiments with taxon-specific 16S rDNA oligonucleotides revealed that 262 isolates belonged to the alpha subclass of the class Proteobacteria. Partial 16S rDNA sequence analysis of selected isolates and oligonucleotide probing with a Sulfitobacter-specific 16S rDNA probe affiliated 33 strains to the genus Sulfitobacter. Analysis of the HaeIII digest pattern of 16S rDNA revealed the presence of two groups; while 30 strains showed a pattern identical with that obtained for Sulfitobacter pontiacus DSM 10014T, a second group of three strains had a unique pattern that was different from that of the type strain. Five isolates of group 1 and one isolates of group 2, strain CH-B427T, were selected for detailed taxonomic analysis. All six isolates closely resembled the type strain Sulfitobacter pontiacus DSM 10014T in physiological reactions. However, strain CH-B427T differed quantitatively in the composition of fatty acids from Sulfitobacter pontiacus DSM 10014T and showed only 98.2% 16S rDNA sequence similarity with strain DSM 10014T. DNA-DNA reassociation value obtained for strains DSM 10014T and CH-B427T revealed 46% similarity. Based on the results of DNA-DNA reassociation and discrete differences in the nucleotide composition of 16S rDNA, a new species of the genus Sulfitobacter is proposed, designated Sulfitobacter mediterraneus sp. nov., the type strain being strain CH-B427T (= DSM 12244T).

Bacillus silvestris sp. nov., a new member of the genus Bacillus that contains lysine in its cell wall

A Gram-positive, aerobic, rod-shaped, peritrichously flagellated, round-endospore-forming bacterium was isolated from a forest soil near Braunschweig, Lower Saxony, Germany, and designated strain HR3-23T (T = type strain). Morphologically, strain HR3-23T shows the characteristics of a member of the genus Bacillus. The spore position is terminal in a swollen sporangium. Comparative analysis of the 16S rDNA sequence shows strain HR3-23T to be most closely related to Caryophanon tenue (95.8% 16S rRNA similarity) and to Bacillus sphaericus (95.4% 16S rRNA similarity). Phylogenetically, the isolate clusters among species of Bacillus RNA group 2. The DNA G + C content of isolate HR3-23T is 39.3 mol%, the peptidoglycan type is A4 alpha (L-Lys-D-Glu), the major respiratory lipoquinone is menaquinone MK-7 and the predominant fatty acid is of the iso-C15:0 type. Based on the morphological, chemotaxonomic, physiological and phylogenetic properties, a new species, Bacillus silvestris, is proposed; strain HR3-23T is the type strain (= DSM 12223T).

Cytoplasmic localization of the trypanothione peroxidase system in Crithidia fasciculata

Tryparedoxin I (TXNI) and tryparedoxin peroxidase (TXNPx), novel proteins isolated from Crithidia fasciculata, have been reported to reconstitute a trypanothione peroxidase activity in vitro (Nogoceke, E.; Gommel, D. U.; Kiess, M.; Kalisz, H. M.; Flohé, L. Biol. Chem. 378:827-836; 1997). Combined with trypanothione reductase, they may form an NADPH-fueled trypanothione-mediated defense system against hydroperoxides in the trypanosomatids. In situ confocal microscopy of antibody-stained TXNI and TXNPx and electron microscopy of the immunogold labeled proteins revealed their colocalization in the cytosol. Insignificant amounts of the enzymes were detected in the nucleus and vesicular structures, whereas the kinetoplast and the mitochondrion are virtually free of any label. Comparison of the PCR product sequences obtained with genomic and cDNA templates rules out any editing typical of kinetoplast mRNA. Sequence similarities with any of the established maxicircle genes of trypanosomatids were not detectable. It is concluded that both, TXNI as well as TXNPx are encoded by nuclear DNA and predominantly, if not exclusively localized in the cytosol. Working in concert with trypanothione reductase, they can function as an enzymatic system that reduces hydroperoxides at the expense of NADPH without any impairment of the flux of reduction equivalents by cellular compartmentation.

No effect of antioxidant supplementation in triathletes on maximal oxygen uptake, 31P-NMRS detected muscle energy metabolism and muscle fatigue

A double-blind placebo-controlled cross-over trial was undertaken to evaluate the effect of antioxidant supplementation on maximal oxygen uptake during bicycling, 31-phosphorus nuclear magnetic response spectroscopy (31P-NMRS) detected muscle energy metabolism during plantar flexion and muscle fatigue evaluated by 1-s electrical stimulation at low (10 Hz) and high (50 Hz) frequency. Seven male triathletes received daily oral antioxidant supplementation in capsule form including 100 mg coenzyme Q10 (CoQ10), 600 mg ascorbic acid and 270 mg alpha-tocopherol or placebo over a 6-week interval. Serum concentration of CoQ10 was significantly higher in the antioxidant phase (1.80+/-1 microg x ml(-1), mean +/- SD) than control (0.9+/-0.21 microg ml(-1)) or placebo phase (0.9+/-0.3 microg x ml(-1)) (P<0.01). Maximal oxygen uptake was 63.8+/-3.0 ml x min(-1) x kg(-1) in the control phase, and did not change significantly in the antioxidant (67.6+/-10.8 ml x min(-1) x kg(-1)) or the placebo phase (61.9+/-4.5 ml x min(-1) x kg(-1)). The combined 31P-NMRS/low frequency fatigue test (plantar flexion of the foot) did not show differences in the gastrocnemius muscle pH (6.77+/-0.14), phosphocreatine reduction at the end of exercise (23+/-14% of rest) and half-time for recovery of phosphocreatine (33+/-12 sec) between the placebo and the antioxidant trial. No difference in muscle fatigue at 10 Hz electrical stimulation was found between the three phases. In conclusion, the results demonstrate no effect of antioxidative vitamin supplementation on maximal oxygen uptake, muscle energy metabolism or muscle fatigue in triathletes.