Synergistic activation of JNK/SAPK by interleukin-1 and platelet-derived growth factor is independent of Rac and Cdc42. (1/2206)

The c-Jun N-terminal kinases (JNKs) are activated strongly by inflammatory cytokines and environmental stresses, but only weakly by growth factors. Here we show that platelet-derived growth factor (PDGF) strongly potentiates activation of JNK by interleukin 1 (IL-1) in human fibroblasts and a pig aortic endothelial (PAE) cell line. This synergistic activation of JNK by IL-1 and PDGF was unaffected by bacterial toxins that inactivate Rho proteins and Ras. Since Rho proteins have been implicated in JNK activation, their possible involvement was investigated further using stably expressed, inducible N17 or V12 mutants in PAE cell lines. N17 Rac non-selectively reduced JNK activity by 30% in resting or stimulated cells (IL-1 alone, or with PDGF). N17 Cdc42 had no effect. V12 Rac weakly activated JNK and synergized with IL-1, but not with PDGF. V12 Cdc42 weakly activated JNK, but synergized with PDGF and not IL-1. Our results imply that Rho GTPases are not directly involved in mediating IL-1-induced JNK activation, or in the potentiation of this activation by PDGF.  (+info)

Rejection of Clostridium putrificum and conservation of Clostridium botulinum and Clostridium sporogenes-Opinion 69. Judicial Commission of the International Committee on Systematic Bacteriology. (2/2206)

The Judicial Commission rejected the name Clostridium putrificum while conserving Clostridium botulinum for toxigenic strains and conserving Clostridium sporogenes for non-toxigenic strains.  (+info)

Characteristics of a strain of Clostridium carnis causing septicaemia in a young infant. (3/2206)

Clostridium carnis is a species which is only rarely isolated from man or animals and is occasionally found in the soil. This paper is an account of a single isolate found in blood cultures obtained from an 8-week-old boy who was suffering from gastroenteritis.  (+info)

The influence of a diet rich in wheat fibre on the human faecal flora. (4/2206)

The effect on the faecal flora of adding wheat fibre to a controlled diet in four healthy volunteers for a 3-week period has been observed. No change in the concentration of the bacteria in the bacterial groups counted was found, although there was a slight increase in total output associated with increased faecal weight. The predominant organisms in all subjects were non-sporing anaerobes, but the dominant species in each subject was different and was unaffected by changing the diet. Similarly, the concentration of faecal beta-glucuronidase detected in two subjects was unaltered and the concentration of clostridia able to dehydrogenate the steroid nucleus found in one subject was unaltered. It is suggested that the faecal microflora is not primarily controlled by the presence of undigested food residues in the large bowel.  (+info)

Nitrate-dependent regulation of acetate biosynthesis and nitrate respiration by Clostridium thermoaceticum. (5/2206)

Nitrate has been shown to shunt the electron flow in Clostridium thermoaceticum from CO2 to nitrate, but it did not influence the levels of enzymes involved in the Wood-Ljungdahl pathway (J. M. Frostl, C. Seifritz, and H. L. Drake, J. Bacteriol. 178:4597-4603, 1996). Here we show that under some growth conditions, nitrate does in fact repress proteins involved in the Wood-Ljungdahl pathway. The CO oxidation activity in crude extracts of nitrate (30 mM)-supplemented cultures was fivefold less than that of nitrate-free cultures, while the H2 oxidation activity was six- to sevenfold lower. The decrease in CO oxidation activity paralleled a decrease in CO dehydrogenase (CODH) protein level, as confirmed by Western blot analysis. Protein levels of CODH in nitrate-supplemented cultures were 50% lower than those in nitrate-free cultures. Western blots analyses showed that nitrate also decreased the levels of the corrinoid iron-sulfur protein (60%) and methyltransferase (70%). Surprisingly, the decrease in activity and protein levels upon nitrate supplementation was observed only when cultures were continuously sparged. Northern blot analysis indicates that the regulation of the proteins involved in the Wood-Ljungdahl pathway by nitrate is at the transcriptional level. At least a 10-fold decrease in levels of cytochrome b was observed with nitrate supplementation whether the cultures were sparged or stoppered. We also detected nitrate-inducible nitrate reductase activity (2 to 39 nmol min-1 mg-1) in crude extracts of C. thermoaceticum. Our results indicate that nitrate coordinately represses genes encoding enzymes and electron transport proteins in the Wood-Ljungdahl pathway and activates transcription of nitrate respiratory proteins. CO2 also appears to induce expression of the Wood-Ljungdahl pathway genes and repress nitrate reductase activity.  (+info)

Antisense RNA strategies for metabolic engineering of Clostridium acetobutylicum. (6/2206)

We examined the effectiveness of antisense RNA (as RNA) strategies for metabolic engineering of Clostridium acetobutylicum. Strain ATCC 824(pRD4) was developed to produce a 102-nucleotide asRNA with 87% complementarity to the butyrate kinase (BK) gene. Strain ATCC 824(pRD4) exhibited 85 to 90% lower BK and acetate kinase specific activities than the control strain. Strain ATCC 824(pRD4) also exhibited 45 to 50% lower phosphotransbutyrylase (PTB) and phosphotransacetylase specific activities than the control strain. This strain exhibited earlier induction of solventogenesis, which resulted in 50 and 35% higher final concentrations of acetone and butanol, respectively, than the concentrations in the control. Strain ATCC 824(pRD1) was developed to putatively produce a 698-nucleotide asRNA with 96% complementarity to the PTB gene. Strain ATCC 824(pRD1) exhibited 70 and 80% lower PTB and BK activities, respectively, than the control exhibited. It also exhibited 300% higher levels of a lactate dehydrogenase activity than the control exhibited. The growth yields of ATCC 824(pRD1) were 28% less than the growth yields of the control. While the levels of acids were not affected in ATCC 824(pRD1) fermentations, the acetone and butanol concentrations were 96 and 75% lower, respectively, than the concentrations in the control fermentations. The lower level of solvent production by ATCC 824(pRD1) was compensated for by approximately 100-fold higher levels of lactate production. The lack of any significant impact on butyrate formation fluxes by the lower PTB and BK levels suggests that butyrate formation fluxes are not controlled by the levels of the butyrate formation enzymes.  (+info)

Sequence analysis of scaffolding protein CipC and ORFXp, a new cohesin-containing protein in Clostridium cellulolyticum: comparison of various cohesin domains and subcellular localization of ORFXp. (7/2206)

The gene encoding the scaffolding protein of the cellulosome from Clostridium cellulolyticum, whose partial sequence was published earlier (S. Pages, A. Belaich, C. Tardif, C. Reverbel-Leroy, C. Gaudin, and J.-P. Belaich, J. Bacteriol. 178:2279-2286, 1996; C. Reverbel-Leroy, A. Belaich, A. Bernadac, C. Gaudin, J. P. Belaich, and C. Tardif, Microbiology 142:1013-1023, 1996), was completely sequenced. The corresponding protein, CipC, is composed of a cellulose binding domain at the N terminus followed by one hydrophilic domain (HD1), seven highly homologous cohesin domains (cohesin domains 1 to 7), a second hydrophilic domain, and a final cohesin domain (cohesin domain 8) which is only 57 to 60% identical to the seven other cohesin domains. In addition, a second gene located 8.89 kb downstream of cipC was found to encode a three-domain protein, called ORFXp, which includes a cohesin domain. By using antiserum raised against the latter, it was observed that ORFXp is associated with the membrane of C. cellulolyticum and is not detected in the cellulosome fraction. Western blot and BIAcore experiments indicate that cohesin domains 1 and 8 from CipC recognize the same dockerins and have similar affinity for CelA (Ka = 4.8 x 10(9) M-1) whereas the cohesin from ORFXp, although it is also able to bind all cellulosome components containing a dockerin, has a 19-fold lower Ka for CelA (2.6 x 10(8) M-1). Taken together, these data suggest that ORFXp may play a role in cellulosome assembly.  (+info)

Segmented filamentous bacteria are potent stimuli of a physiologically normal state of the murine gut mucosal immune system. (8/2206)

Segmented filamentous bacteria (SFB) are autochthonous bacteria inhabiting the intestinal tracts of many species, including humans. We studied the effect of SFB on the mucosal immune system by monoassociating formerly germfree C3H/HeN mice with SFB. At various time points during 190 days of colonization, fragment cultures of small intestine and Peyer's patches (PP) were analyzed for total immunoglobulin A (IgA) and SFB-specific IgA production. Also, phenotypic changes indicating germinal center reactions (GCRs) and the activation of CD4(+) T cells in PP were determined by using fluorescence-activated cell sorter analyses. A second group of SFB-monoassociated mice was colonized with a gram-negative commensal, Morganella morganii, to determine if the mucosal immune system was again stimulated and to evaluate the effect of prior colonization with SFB on the ability of M. morganii to translocate to the spleen and mesenteric lymph nodes. We found that SFB stimulated GCRs in PP from day 6 after monoassociation, that GCRs only gradually waned over the entire length of colonization, that natural IgA production was increased to levels 24 to 63% of that of conventionally reared mice, and that SFB-specific IgA was produced but accounted for less than 1.4% of total IgA. Also, the proportion of CD4(+), CD45RBlow T cells, indicative of activated cells, gradually increased in the PP to the level found in conventionally reared mice. Secondary colonization with M. morganii was able to stimulate GCRs anew, leading to a specific IgA antibody response. Previous stimulation of mucosal immunity by SFB did not prevent the translocation of M. morganii in the double-colonized mice. Our findings generally indicate that SFB are one of the single most potent microbial stimuli of the gut mucosal immune system.  (+info)