口源性口臭患者主要厌氧菌的分布

目的分析口臭患者龈下菌斑和舌苔上主要相关厌氧菌的分布情况。方法选择口腔门诊中口臭患者29例,鼻闻法来确定产臭部位和非产臭部位;分别采集龈下菌斑和舌苔标本接种在非选择性培养基和核梭杆菌选择性培养基,厌氧培养5d后记录非选择性培养基上生长的细菌总数、产黑色素细菌总数及核梭杆菌选择性培养基上生长的目的菌总数。结果29例患者中,15例患者的口臭主要来源于龈缘菌斑,10例主要来源于舌苔,4例患者的口臭由龈缘菌斑和舌苔共同产生;产臭部位和非产臭部位相比,细菌总数、产黑色素菌和具核梭杆菌数都明显上升（P〈0．01）。结论口源性口臭患者口气变化与产黑色素细菌、核梭杆菌相关。     

Corrinoids in anaerobic bacteria

Abstract C₁-metabolizing bacteria were analyzed for their corrinoids. The autotrophic phototrophe Chloroflexus aurantiacus contains predominantly the light-sensitive coenzyme B₁₂. The corrinoid could be teh prostethic group of a methylmalonyl-CoA mutase, which is involved in the CO₂ fixing reaction sequence from proplonyl-CoA to succinyl CoA. Methanobacterium thermoautotrophicum and Sporomusa ovata contain only traces of light-sensitive corrinoids, indicating that the demethylation reaction is favored, if these corrinoids are involved in methyl transfer reactions. The chemical structure of the unique p -cresolyl cobamide is specific for the acetogenic bacterium S. ovata , rather than the corrinoid 'factor III' for methanogenic bacteria.     

Citrate metabolism in anaerobic bacteria

Abstract The regulation of anaerobic citrate metabolism is very diverse among different groups of bacteria. In organisms like Streptococcus lactis and Clostridium sporosphaeroides which lack citrate synthase, the activity of its antagonistic enzyme, citrate lyase, need not be regulated. Many anaerobes like Rhodocyclus gelatinosus and Clostridium sphenoides are able to synthesize their own l -glutamate and contain citrate synthase. In these bacteria the activity of citrate metabolizing enzymes which are involved in a cascade system are under strict control. In Rc. gelatinosus activation/inactivation of citrate lyase is controlled by acetylation/deacetylation which is catalyzed by its corresponding regulatory enzymes, citrate lyase ligase and citrate lyase deacetylase. In C. sphenoides inactivation of citrate lyase is accomplished by deacetylation as well as by changing in the enzyme conformation. Activation of citrate lyase is catalyzed by citrate lyase ligase whose activity in addition is modulated by phosphorylation/dephosphorylation. Further, electron transport process also seems to play a role in the inactivation of citrate metabolizing enzymes in enteric bacteria.     

Unusual dehydrations in anaerobic bacteria

Abstract In amino acid fermenting anaerobic bacteria a set of unusual dehydratases is found which use 2-hydroxyacyl-CoA, 4-hydroxybutyryl-CoA or 5-hydroxyvaleryl-CoA as substrates. The extremely oxygen-sensitive 2-hydroxyacyl-CoA dehydratases catalysing the elimination of water from ( R )-lactyl-CoA to acryloyl-CoA or from ( R )-2-hydroxyglutaryl-CoA to glutaconyl-CoA contain iron-sulfur clusters as well as riboflavin and require additional activation by ATP. The dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA is catalysed by a moderately oxygen-sensitive enzyme also containing an iron-sulfur cluster and FAD. In all these reactions a non-activated C-H-bond at C₃ has to be cleaved by mechanisms not yet elucidated. The dehydration of 5-hydroxyvaleryl-CoA to 4-pentenoyl-CoA, however, has been characterised as a redox process mediated by enzyme-bound FAD. Finally, an iron-sulfur cluster-containing but pyridoxal-phosphate-independent l -serine dehydratase is described.     

Interactions between amino-acid-degrading bacteria and methanogenic bacteria in anaerobic digestion

The degradation of amino acids in anaerobic digestion was examined in terms of the interactions between amino-acid-degrading bacteria and methanogenic bacteria. Certain amino acids were degraded oxidatively by dehydrogenation, with methanogenic bacteria acting as H(2) acceptors. The inhibition of methanogenesis by chloroform also inhibited the degradation of these amino acids and/or caused variations in the composition of volatile acids produced from them. The presence of glycine reduced the inhibitory effect caused by chloroform, probably because glycine acted as an H(2) acceptor in place of methanogenic bacteria. This fact suggested that the coupled oxidation-reduction reactions between two amino acids-one acting as the H(2) donor and the other acting as the H(2) acceptor-may occur in the anaerobic digestion of proteins or amino-acid mixtures. The conversion of some proteins to volatile acids was not affected when methanogenesis was inhibited by chloroform. This suggested that the component amino acids of proteins may be degraded by the coupled oxidation-reduction reactions and that the degradation of proteins may not be dependent on the activity of methanogenic bacteria as H(2) acceptors.     

Growth of Thiocapsa roseopersicina purple sulfur bacteria in darkness under anaerobic conditions]

The phototrophic sulphur bacterium. Thiocapsa roseopersicina, strain BBS, was grown under anaerobic conditions in the darkness on the medium containing glucose and thiosulphate or molecular sulphur. The assimilation of glucose is accompanied by the accumulation of small amounts of pyruvate in the medium, and the uptake of thiosulphate or molecular sulphur leads to the formation of sulphates and hydrogen sulphide.     

High prevalence and resistance rates to antibiotics in anaerobic bacteria in specimens from patients with chronic balanitis

Aim of the study was to assess both prevalence and antibiotic resistance in anaerobic bacteria from glans penis skin of 70 adults. Strain susceptibility was determined by breakpoint susceptibility test or E test. In 9 asymptomatic, 48 untreated and 13 treated symptomatic patients, anaerobes were found in 22.2%, 70.8% and 53.3%, respectively. Gram-positive strains (GPAs) were 2.2-fold more common than Gram-negative ones. Prevalent Gram-negative (GNAs) and GPAs were Prevotella spp. and anaerobic cocci, respectively. Clostridium difficile strain was found in an untreated patient. In GNAs, resistance rates to amoxicillin, metronidazole, clindamycin, tetracycline, levofloxacin, and amoxicillin/clavulanate were 42.1, 0, 52.6, 53.3, 86.7 and 5.2%, respectively. In GPAs, the resistance rates to metronidazole, clindamycin, tetracycline, levofloxacin and amoxicillin/clavulanate were 18.2, 34.1, 52.6, 36.8 and 0%, respectively. In conclusion, anaerobes were 1.6-fold more frequent in untreated symptomatic patients compared with other patients, suggesting their participation in development of chronic balanitis. GPAs were more common than GNAs. The resistance rates to amoxicillin, clindamycin, tetracycline, and levofloxacin were high. Most active agents were metronidazole and amoxicillin/clavulanate. Resistance in anaerobes varies according to sites of specimens and years of study.     

Correlation of the DNA nucleotide makeup with the physiological and cytological characteristics of spore-forming anaerobic bacteria]

The nucleotide composition of DNA from 12 studied species of anaerobic bacteria belongs to AT type, with G+C varying from 28.4 to 36.8 mole%. In the anaerobic group of Clostridium bifermentans, a correlation has been established between the nucleotide composition of DNA, the type of appendages on spores, and some physiologo-biochemical characteristics. The nucleotide composition of DNA in the spores of four anaerobic species is shifted toward GC type as compared to DNA in the vegetative cells. Data on the content of GC pairs in DNA of the spores may sometimes be of a higher taxonomic value than the corresponding evidence on DNA of the vegetative cells.     

The association of anaerobic bacteria with infectious mononucleosis

This review summarizes the information that supports the potential importance of anaerobic bacteria in the pharyngo-tonsillitis (PT) associated with infectious mononucleosis (IM). Evidence supportive of the potential of involvement of bacteria in IM was provided by several studies that showed increased recovery of bacteria on the tonsillar surfaces in IM. Several studies demonstrated that metronidazole therapy alleviated the clinical symptoms of tonsillar hypertrophy and shortened the duration of fever in IM. Metronidazole has no antimicrobial activity against aerobic bacteria and is only effective against anaerobic bacteria. A possible mechanism of its action is the suppression of the oral anaerobic flora that might contribute to the inflammatory process induced by the Epstein-Barr virus. This explanation is supported by the increased recovery of Prevotella intermedia and Fusobacterium nucleatum from the tonsillar surfaces during the acute phases of IM and an immune response against these organisms by patients with IM. Although more studies are needed, these findings support the possible pathogenicity of Gram-negative anaerobic bacteria in the PT associated with IM.     

Radical-mediated dehydration reactions in anaerobic bacteria

Most dehydratases catalyse the elimination of water from beta-hydroxy ketones, beta-hydroxy carboxylic acids or beta-hydroxyacyl-CoA. The electron-withdrawing carbonyl functionalities acidify the alpha-hydrogens to enable their removal by basic amino acid side chains. Anaerobic bacteria, however, ferment amino acids via alpha- or gamma-hydroxyacyl-CoA, dehydrations of which involve the abstraction of a beta-hydrogen, which is ostensibly non-acidic (pK ca. 40). Evidence is accumulating that beta-hydrogens are acidified via transient conversion of the CoA derivatives to enoxy radicals by one-electron transfers, which decrease the pK to 14. The dehydrations of (R)-2-hydroxyacyl-CoA to (E)-2-enoyl-CoA are catalysed by heterodimeric [4Fe-4S]-containing dehydratases, which require reductive activation by an ATP-dependent one-electron transfer mediated by a homodimeric protein with a [4Fe-4S] cluster between the two subunits. The electron is further transferred to the substrate, yielding a ketyl radical anion, which expels the hydroxyl group and forms an enoxy radical. The dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA involves a similar mechanism, in which the ketyl radical anion is generated by one-electron oxidation. The structure of the FAD- and [4Fe-4S]-containing homotetrameric dehydratase is related to that of acyl-CoA dehydrogenases, suggesting a radical-based mechanism for both flavoproteins.     

Oxygen tolerance in anaerobic pathogenic bacteria

A prerequisite for successful identification of anaerobic pathogenic bacteria from samples of clinical material is the method of cultivation. Currently, several methods of cultivation in anaerobic environment are used: cultivation in anaerobic box, anaerobic jar, and in nonrecurring cultivation system. Here, we determined the suitability of the above methods of cultivation using the estimation of the growth (diameters of colony size) of commonly isolated anaerobic pathogens (Bacteroides fragilis, Clostridium difficile, and Clostridium perfringens). The tested bacterial strains were exposed to atmospheric oxygen for various time periods and then they were cultivated using different anaerobic cultivation systems. Maximum growth differed, depending on the type of cultivation and the strain used. Thus, largest zone diameters, in the majority of measurements, were achieved in the anaerobic box. However, nonrecurring cultivation system seemed better in several cases; this applied to the cultivation of C. perfringens after 15, 30, and 60 min exposure to atmospheric oxygen as well as the cultivation of B. fragilis after 30 and 60 min of oxygen exposure. The cultivation in anaerobic box was the most convenient method for growth of C. difficile. In almost all cases, higher growth was observed in nonrecurring cultivation system than in the system of anaerobic jar. On the other hand, no significant differences were observed among these anaerobic cultivation systems which confirmed their applicability (taking into account some individual features concerning the optimization of cultivations) for identification of pathogenic anaerobes.     

Energy conservation in chemotrophic anaerobic bacteria

[This corrects the article on p. 100 in vol. 41.].     

Volatile organic metabolites identify patients with gastric carcinoma,gastric ulcer,or gastritis and control patients

Background

Gastric cancer ranks 4th among the most common cancers worldwide, and the mortality caused by gastric cancer is 2nd only to lung cancer. Gastric cancer shows a lack of specific symptoms in its early stages. In addition, its clinical symptoms often do not match the corresponding stage. Upper gastrointestinal endoscopy with biopsy is the gold standard for the diagnosis of gastric cancer because of its high accuracy. However, this operation is invasive, patient compliance is poor, and high demands for medical staff and equipment are typical of this procedure. Recent studies have demonstrated a connection between specific breath volatile organic compounds (VOCs) and various forms of cancers.

Methods

We collected expired air from patients with gastric cancer, chronic atrophic gastritis or gastric ulcers as well as from healthy individuals. Solid-phase microextraction, gas chromatography–mass spectrometry and principal component analysis statistics were applied to identify potential biomarkers of gastric cancer among VOCs.

Results

Fourteen differential metabolites were annotated using the NIST 11 database, with a similarity threshold of 70%. Currently, the metabolic origin of VOCs remains unclear; however, several pathways might explain the decreasing or increasing trends that were observed.

Conclusions

The results of this study demonstrate the existence of specific VOC profiles associated with patients with carcinoma. In addition, these metabolites may contribute to the diagnosis and screening of patients with carcinoma.