艰难梭菌荚膜多糖单糖组成的气相色谱分析

本文对两株艰难梭菌（ＣｄＡ３１８和ＣｄＣＤＣ２７９）荚膜多糖进一步分析,结果证实纯化的艰难梭菌荚膜多糖为单一均匀的物质;经气相色谱分析表明,其单糖组分主要由Ｄ－葡萄糖、Ｄ－甘露糖和Ｄ－半乳糖组成,不同菌株的荚膜多糖可能有微小差异。     

Yeast, beef and pork extracts counteract Clostridium difficile toxin A enterotoxicity

Clostridium difficile is responsible for a large proportion of nosocomial cases of antibiotic-associated diarrhoea and pseudomembranous colitis. The present study provides evidence that yeast, beef and pork extracts, ingredients commonly used to grow bacteria, can counteract C. difficile toxin A enterotoxicity in vitro and in vivo . In model intestinal epithelial cells the individual extracts could prevent the toxin A-induced decrease in epithelial barrier function and partially prevented actin disaggregation and cell rounding. Mice with ad libitum access to individual extracts for 1 week had almost complete reduction in toxin A-induced fluid secretion in intestinal loops. Concomitantly, the toxin A-induced expression of the essential proinflammatory mediator Cox-2 was normalized. Moreover this protective effect was also seen when mice received only two doses of extract by intragastric gavage within 1 week. These results show that yeast, beef and pork extracts have the potential to counteract the intestinal pathogenesis triggered by C. difficile toxin A.     

Molecular dynamics study of the proposed proton transport pathways in [FeFe]-hydrogenase

Possible proton transport pathways in Clostridium pasteurianum (CpI) [FeFe]-hydrogenase were investigated with molecular dynamics simulations. This study was undertaken to evaluate the functional pathway and provide insight into the hydrogen bonding features defining an active proton transport pathway. Three pathways were evaluated, two of which consist of water wires and one of predominantly amino acid residues. Our simulations suggest that protons are not transported through water wires. Instead, the five-residue motif (Glu282, Ser319, Glu279, H₂O, Cys299) was found to be the likely pathway, consistent with previously made experimental observations. The pathway was found to have a persistent hydrogen bonded core (residues Cys299 to Ser319), with less persistent hydrogen bonds at the ends of the pathway for both H₂ release and H₂ uptake. Single site mutations of the four residues have been shown experimentally to deactivate the enzyme. The theoretical evaluation of these mutations demonstrates redistribution of the hydrogen bonds in the pathway, resulting in enzyme deactivation. Finally, coupling between the protein dynamics near the proton transport pathway and the redox partner binding regions was also found as a function of H₂ uptake and H₂ release states, which may be indicative of a correlation between proton and electron movement within the enzyme.     

Clostridium perfringens alpha toxin is produced in the intestines of broiler chicks inoculated with an alpha toxin mutant

Poultry necrotic enteritis (NE) is caused by specific strains of Clostridium perfringens, most of which are type A. The role of alpha toxin (CPA) in NE has been called into question by the finding that an engineered cpa mutant retains full virulence in vivo[9]. This is in contrast to the finding that immunization with CPA toxoids protects against NE. We confirmed the earlier findings, in that 14-day-old Cornish × Rock broiler chicks challenged with a cpa mutant developed lesions compatible with NE in >90% of birds inoculated with the mutant. However, CPA was detected in amounts ranging from 10 to >100 ng per g of gut contents and mucosa in birds inoculated with the cpa mutant, the wildtype strain from which the mutant was constructed, and our positive control strain. There was a direct relationship between lesion severity and amount of CPA detected (R = 0.89-0.99). These findings suggest that the role of CPA in pathogenesis of NE requires further investigation.     

Infection Status of Hospitalized Diarrheal Patients with Gastrointestinal Protozoa, Bacteria, and Viruses in the Republic of Korea

To understand protozoan, viral, and bacterial infections in diarrheal patients, we analyzed positivity and mixed-infection status with 3 protozoans, 4 viruses, and 10 bacteria in hospitalized diarrheal patients during 2004-2006 in the Republic of Korea. A total of 76,652 stool samples were collected from 96 hospitals across the nation. The positivity for protozoa, viruses, and bacteria was 129, 1,759, and 1,797 per 10,000 persons, respectively. Especially, Cryptosporidium parvum was highly mixed-infected with rotavirus among pediatric diarrheal patients (29.5 per 100 C. parvum positive cases), and Entamoeba histolytica was mixed-infected with Clostridium perfringens (10.3 per 100 E. histolytica positive cases) in protozoan-diarrheal patients. Those infected with rotavirus and C. perfringens constituted relatively high proportions among mixed infection cases from January to April. The positivity for rotavirus among viral infection for those aged ≤ 5 years was significantly higher, while C. perfringens among bacterial infection was higher for ≥ 50 years. The information for association of viral and bacterial infections with enteropathogenic protozoa in diarrheal patients may contribute to improvement of care for diarrhea as well as development of control strategies for diarrheal diseases in Korea.     

A Clostridium perfringens hem gene cluster contains a cysG(B) homologue that is involved in cobalamin biosynthesis

The hem gene cluster, which consists of hemA, cysG(B), hemC, hemD, hemB, and hemL genes, and encodes enzymes involved in the biosynthetic pathway from glutamyl-tRNA to uroporphyrinogen III, has been identified by the cloning and sequencing of two overlapping DNA fragments from Clostridium perfringens NCTC8237. The deduced amino acid sequence of the N-terminal region of C. perfringens HemD is homologous to those reported for the C-terminal region of Salmonella typhimurium CysG and Clostridium josui HemD. C. perfringens CysG(B) is a predicted 220-residue protein which shows homology to the N-terminal region of S. typhimurium CysG. Disruption of the cysG(B) gene in C. perfringens strain 13 by homologous recombination reduced cobalamin (vitamin B12) levels by a factor of 200. When grown in vitamin B12-deficient medium, the mutant strain showed a four-fold increase in its doubling time compared with that of the wild-type strain, and this effect was counteracted by supplementing the medium with vitamin B12. These results suggest that C. perfringens CysG(B) is involved in the chelation of cobalt to precorrin II as suggested for the CysG(B) domain of S. typhimurium CysG, enabling the synthesis of cobalamin.     

Breakdown of crystalline cellulose by synergistic action between cellulase components from Clostridium thermocellum and Trichoderma koningii

Abstract Certain isolated components of fungal cellulases, which cannot effect the breakdown of highly ordered cellulose individually, interact together synergistically to do so when recombined. Suprisingly, not all fungal cellulase components exhibit this property, and no such synergism has been observed so far between fungal and bacterial cellulases.
The cellulase complex of Clostridium thermocellum cannot effect the extensive breakdown of highly ordered cellulose unless Ca²⁺ and dithiothreitol (DTT) are present. However, we now report that isolated cellobiohydrolase from Trichoderma koningii can combine with C. thermocellum cellulase to effect the breakdown of cellulose in the absence of Ca²⁺ and DTT. enhanced activity is observed if Ca²⁺ and DTT are present.
This finding may have important applications in industry: it certainly has important implications for those interested in the basic mechanism of cellulase action in C. thermocellum .     

Regeneration of cells from protoplasts ofClostridium acetobutylicum B643

Summary Conditions that allow regeneration of cells fromClostridium acetobutylicum strain B643 protoplasts were studied. Protoplast formation and stabilization in minimal media with 50 mM CaCl₂, 50 mM MgCl₂ and 0.3 M sucrose were crucial to subsequent regeneration on soft yeast extract agar containing 25 mM CaCl₂ and 25 mM MgCl₂. A regeneration frequency of 8–25% was consistently obtained.