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PubMedDate not supplied

Anaerobic infections in childhood.

Anaerobic bacteria are part of the normal flora of mucous membranes and outnumber aerobic bacteria in the oral cavity and gastrointestinal tract. Anaerobes can be isolated from pediatric patients with various infections when appropriate techniques for transportation and cultivation of samples are employed. Frequently anaerobes are isolated in combination with other facultative or aerobic bacteria. The genera or groups of anaerobes most frequently isolated from pyogenic infections in children are (in order of decreasing frequency) OFFteroides, Clostridium, gram-positive cocci, Fusobacterium, gram-positive rods (Eubacterium, Lactobacillus, Propionibacterium, Actinomyces, and Bifidobacterium), and gram-negative cocci (Veillonella and Acidaminococcus). Clostridium perfringens causes bacteremia and wound infections. Clostridium botulinum can produce a paralytic toxin that causes a lethal illness in adults and a paralytic syndrome in infants. Clostridium difficile can cause antibiotic-associated colitis or diarrhea. Bacteroides fragilis is most frequently involved in intraabdominal infections, infections of the female genital tract, subcutaneous abscesses, and bacteremia. Bacteroides melaninogenicus and Bacteroides oralis are the predominent anaerobes in orofacial infections and aspiration pneumonia. Fusobacterium species are pathogens in aspiration pneumonia, brain abscesses, and orofacial infections. Anaerobic gram-positive cocci can be recovered from all types of infections but predominate in respiratory tract and intra-abdominal infections. Recognition of the pathogenic qualities of the various anaerobic organisms can assist in their prompt identification and in the initiation of appropriate therapy.

Actinomyces↗

PubMed2003

Crystal structure of the carboxyltransferase subunit of the bacterial sodium ion pump glutaconyl-coenzyme A decarboxylase.

Glutaconyl-CoA decarboxylase is a biotin-dependent ion pump whereby the free energy of the glutaconyl-CoA decarboxylation to crotonyl-CoA drives the electrogenic transport of sodium ions from the cytoplasm into the periplasm. Here we present the crystal structure of the decarboxylase subunit (Gcdalpha) from Acidaminococcus fermentans and its complex with glutaconyl-CoA. The active sites of the dimeric Gcdalpha lie at the two interfaces between the mono mers, whereas the N-terminal domain provides the glutaconyl-CoA-binding site and the C-terminal domain binds the biotinyllysine moiety. The Gcdalpha catalyses the transfer of carbon dioxide from glutaconyl-CoA to a biotin carrier (Gcdgamma) that subsequently is decarboxylated by the carboxybiotin decarboxylation site within the actual Na(+) pump (Gcdbeta). The analysis of the active site lead to a novel mechanism for the biotin-dependent carboxy transfer whereby biotin acts as general acid. Furthermore, we propose a holoenzyme assembly in which the water-filled central channel of the Gcdalpha dimer lies co-axial with the ion channel (Gcdbeta). The central channel is blocked by arginines against passage of sodium ions which might enter the central channel through two side channels.

Binding Sites↗

PubMed1975

Susceptibility of anaerobic bacteria to metronidazole: relative resistance of non-spore-forming gram-positive baccilli.

Susceptibility of 358 clinical isolates of obligate anaerobes to metronidazole was determined by an agar-dilution technique. Only 66% of all isolates were inhibited by 6.25 mug/ml, whereas 30% required larger than or equal to 50 mug/ml. Considerable variation in susceptibility was observed among different genera and species of bacteria. Fusobacterium was most senstitive, followed by Clostridium, Bacteroides and Peptococcus, Peptostreptococcus, Veillonella and Acidaminococcus, and non-spore-forming gram-positive bacilli. Bacteroides fragilis was more sensitive than other species of Bacteroides. Similarly, Clostridium perfringens was more susceptible than other species of Clostriduim. While metronidazole appears to be a promising antimicrobial agent for infections caused by Fusobacterium, Clostrididium, and B.fragilis, therapy for infections with other anaerobic bacteria should be guided by in vitro tests of sensitiivity.

Anaerobiosis↗

PubMed1995

Succiniclasticum ruminis gen. nov., sp. nov., a ruminal bacterium converting succinate to propionate as the sole energy-yielding mechanism.

A gram-negative, anaerobic, nonmotile, non-spore-forming, rod-shaped bacterium that fermented succinate quantitatively to propionate was isolated from a high dilution of rumen ingesta obtained from a dairy cow fed a production diet containing grass silage as the main roughage source. This organism did not grow on any of the following energy sources: 12 carbohydrates, pyruvate, lactate, 7 dicarboxylic acids, aspartate, citrate, and trans-aconitate. Both rumen fluid and yeast extract were necessary for good growth on succinate. The organism was negative for the following characteristics: production of propionate from threonine, protein digestion, sulfide production, nitrate reduction, catalase activity, and urease activity. There was no growth at 22 degrees C and reduced growth at 45 degrees C compared with growth at 39 degrees C. The DNA base composition was 52 mol% G + C. The complete 16S rRNA sequence (EMBL accession number, X81137) was obtained, and the phylogenetic relationships of the organism were determined. The most closely related genera were the genera Acidaminococcus and Phascolarctobacterium. The name proposed for this bacterium is Succiniclasticum ruminis gen. nov., sp. nov.; the type strain is strain SE10 (= DSM 9236). Additional isolation attempts revealed that S. ruminis is a common inhabitant of the rumina of cows that are fed production diets and of cows on pasture.

Animals↗

PubMed1995

Phylogenetic placement of Dialister pneumosintes (formerly Bacteroides pneumosintes) within the Sporomusa subbranch of the Clostridium subphylum of the gram-positive bacteria.

The nucleotide sequence of the 16S rRNA gene of the type strain of Dialister pneumosintes was determined. Phylogenetic analysis revealed that this species belongs to the Sporomusa branch of the Clostridium subphylum of the gram-positive bacteria and should therefore be excluded from the family Bacteroidaceae. Within this branch, which encompasses several other gram-negative taxa, such as Acidaminococcus, Pectinatus, Phascolarcobacterium, Quinella, Selenomonas, and Zymophilus, Dialister showed a specific, albeit distant, affinity with the genera Megasphaera and Veillonella.

Bacteroidaceae↗

PubMed2003

Diet influences the ecology of lactic acid bacteria and Escherichia coli along the digestive tract of cattle: neural networks and 16S rDNA.

In this manuscript, the authors have sought to gain a better understanding of the interactions between Escherichia coli and lactic acid bacteria (LAB) isolated from Rogossa MRS agar along the digestive tract of grain- and forage-fed cattle. E. coli from cattle receiving a high-grain diet were more numerous (P<0.05) than from the high-forage diet and the highest numbers were in the faeces. Isolates on Rogossa MRS agar were always greater in the high-grain diet (P<0.05) and contained a significant number of LAB. A random set of Rogossa MRS agar colonies was selected and artificial neural networks were used to develop a relationship between colony description and species which was validated using sequence analysis (16S rDNA). The neural networks correctly predicted species in more than 80 % of cases and was composed, primarily, of Lactobacillus vitulinus, Lactobacillus ruminis, Selenomonas ruminantium, Streptococcus bovis, Acidaminococcus fermentans and Megasphaera elsdenii. In conjunction with statistical diversity indices, it was demonstrated that diversity in the high-fibre diet was always lower and was a consequence of the dominance of Str. bovis. In contrast, the diversity in the high-grain diet was greater (P<0.05) and was a consequence of the decline in Str. bovis. These data demonstrate that there is a positive relationship between coliform and LAB isolates throughout the digestive tract of cattle, and diet is the major factor regulating bacterial composition.

Animal Feed↗

PubMed1980

The reversible dehydration of (R)-2-hydroxyglutarate to (E)-glutaconate.

1. During fermentation with whole cells of Acidaminococcus fermentans or Clostridium microsporum the pro-3S hydrogen of (R)-2-hydroxyglutarate or of its precursor (S)-glutamate is eliminated stereospecifically. Since (E)-glutaconate but not its Z isomer is fermented by whole cells or cell-free extracts of A. fermentans, the overall dehydration of (R)-2-hydroxyglutarate to (E)-glutaconate can be described as syn. 2. The fermentation of (E)-glutaconate required acetyl phophate, CoA and NAD, that of (S)-glutamate or (R)-2-hydroxyglutarate additionally MgCl2, FeSO4 and dithioerythritol. The fermentations of all three substrates were inhibited by avidin and stimulated by biotin. 3. The hydration of (E)-glutaconate was measured enzymically by the formation of (R)-2-hydroxyglutarate. The dehydration of the hydroxy acid was assayed by the release of 3HOH from (2R)-2-hydroxy[3-3H]glutarate. Optimum conditions were found by activation of the cell-free extract with MgCl2, FeSO4, dithioerythritol, acetyl phosphate anmd NADH followed by the reaction which only required acetyl phosphate and CoA as cofactors. Activation and reaction had to be performed anaerobically. 4. The dehydration was inhibited by 2 mM azide, 1 mM arsenate, 1 mM hydroxylamine, 20 micro M dinitrophenol or 10 micro M carbonylcyanide p-trifluoromethoxyphenylhydrazone. 5. It is concluded that the actual substrates of the dehydration are the corresponding thiol esters. The data indicate a catalytical phosphorylation during the reaction.

Bacteria↗

PubMed1983

Purification, characterisation and reconstitution of glutaconyl-CoA decarboxylase, a biotin-dependent sodium pump from anaerobic bacteria.

Glutaconyl-CoA decarboxylase from Acidaminococcus fermentans is a biotin enzyme, which is integrated into membranes. It is activated by Triton X-100 and inhibited by avidin. The results obtained by a combination of both agents indicate that biotin and the substrate-binding site are located on the same side of the membrane. The decarboxylase was solubilized with Triton X-100 and purified by affinity chromatography on monomeric avidin-Sepharose. The enzyme is composed of three types of polypeptides: the group of alpha chains (Mr 120000-140000) containing the biotin, the beta chain (60000) and an apparently hydrophobic gamma chain (35000). Sodium ions specifically protected the latter chain from tryptic digestion. It was supposed, therefore, that this chain might function as the Na+ channel. The beta and gamma chains but not the alpha chain could be labelled by N-ethyl-[14C]maleimide. Similar decarboxylases but with much smaller biotin peptides (Mr 15000-20000) were isolated from Peptococcus aerogenes and Clostridium symbiosum. The decarboxylases from all three organisms could be reconstituted to active sodium pumps by incubation with phospholipid vesicles and octylglucoside followed by dilution. The Na+ uptake catalysed by the enzyme from A. fermentans was completely inhibited by monensin and activated twofold by valinomycin/K+ indicating an electrogenic Na+ pump. The coupling between Na+ transport and decarboxylation was not tight. During the reaction the ratio decreased from initially 1 to 0.2. The three organisms mentioned above and Clostridium tetanomorphum without glutaconyl-CoA decarboxylase are able to ferment glutamate and require 10 mM Na+ for rapid growth. There is no correlation between the concentration of monensin necessary to inhibit growth and the presence of decarboxylase in these organisms.

Bacteria, Anaerobic↗

PubMed1987

Equilibrium constants of several reactions involved in the fermentation of glutamate.

The equilibrium constants of the reactions catalysed by (S)-citramalate lyase and (R)-2-hydroxyglutarate dehydrogenase were determined using the purified enzymes from Clostridium tetanomorphum and Acidaminococcus fermentans, respectively. The former constant had to be determined at high ionic strength (I). Therefore it was corrected to I = 0.1 M by applying single-ion activity coefficients estimated from literature data. The result (Kapp = 4.31 +/- 0.07 M-1; direction of citramalate formation) agreed very well with the constant of the (2R,3S)-2,3-dimethylmalate lyase equilibrium when all optical isomers were taken into account. From these and other data values for the free energies of formation (delta Gzerof) of (2S,3S)-3-methylaspartate, mesaconate and (S)-citramalate were calculated. The constant of the (R)-2-hydroxyglutarate dehydrogenase equilibrium [Kapp = (1.47 +/- 0.12)10(-12) M, direction of 2-oxoglutarate formation, I = 0.1 M] was shown to lie between those for malate and lactate dehydrogenases as expected.

Alcohol Oxidoreductases↗

PubMed1992

Susceptibilities of anaerobic bacteria isolated from animals with ovine foot rot to 28 antimicrobial agents.

The agar dilution method was used to determine the inhibitory activities of 28 antimicrobial agents against 35 strains of the genus Peptostreptococcus, 4 strains of the species Peptococcus niger, 20 strains of the species Megasphaera elsdenii, 7 strains from the species Acidaminococcus fermentans, 8 strains of the genus Clostridium, 11 strains of the genus Eubacterium, and 1 strain of the species Propionibacterium acidipropionici, all of which were isolated from 125 clinical cases of ovine foot rot between January 1987 and December 1988. The three unreidopenicillins studied proved to be the most active antimicrobial agents, with a high percentage of strains being susceptible at a concentration of 64 micrograms/ml. Penicillin G, ampicillin, and the three cephalosporins studied also had good activity. Fosfomycin showed a high degree of activity among the 116 anaerobic bacteria tested.

Animals↗

PubMed2000

Comparative In vitro activities of ertapenem (MK-0826) against 1,001 anaerobes isolated from human intra-abdominal infections.

By using an agar dilution method, the comparative in vitro activities of ertapenem (MK-0826) were studied against 1,001 anaerobes isolated from human intra-abdominal infections in 17 countries worldwide. MK-0826 was uniformly active against all isolates, including all Bacteroides fragilis group species isolates, with the exception of 12 of 61 (20%) strains of Bilophila wadsworthia, 3 strains of lactobacilli, and 1 isolate of Acidaminococcus fermentans. Geographical variation in activity was not observed.

Abdominal Abscess↗

PubMed2000

Culture-dependent and culture-independent characterization of microbial assemblages associated with high-temperature petroleum reservoirs.

Recent investigations of oil reservoirs in a variety of locales have indicated that these habitats may harbor active thermophilic prokaryotic assemblages. In this study, we used both molecular and culture-based methods to characterize prokaryotic consortia associated with high-temperature, sulfur-rich oil reservoirs in California. Enrichment cultures designed for anaerobic thermophiles, both autotrophic and heterotrophic, were successful at temperatures ranging from 60 to 90 degrees C. Heterotrophic enrichments from all sites yielded sheathed rods (Thermotogales), pleomorphic rods resembling Thermoanaerobacter, and Thermococcus-like isolates. The predominant autotrophic microorganisms recovered from inorganic enrichments using H(2), acetate, and CO(2) as energy and carbon sources were methanogens, including isolates closely related to Methanobacterium, Methanococcus, and Methanoculleus species. Two 16S rRNA gene (rDNA) libraries were generated from total community DNA collected from production wellheads, using either archaeal or universal oligonucleotide primer sets. Sequence analysis of the universal library indicated that a large percentage of clones were highly similar to known bacterial and archaeal isolates recovered from similar habitats. Represented genera in rDNA clone libraries included Thermoanaerobacter, Thermococcus, Desulfothiovibrio, Aminobacterium, Acidaminococcus, Pseudomonas, Halomonas, Acinetobacter, Sphingomonas, Methylobacterium, and Desulfomicrobium. The archaeal library was dominated by methanogen-like rDNAs, with a lower percentage of clones belonging to the Thermococcales. Our results strongly support the hypothesis that sulfur-utilizing and methane-producing thermophilic microorganisms have a widespread distribution in oil reservoirs and the potential to actively participate in the biogeochemical transformation of carbon, hydrogen, and sulfur in situ.

Archaea↗

PubMed2002

Ammonia production by ruminal microorganisms and enumeration, isolation, and characterization of bacteria capable of growth on peptides and amino acids from the sheep rumen.

Excessive NH(3) production in the rumen is a major nutritional inefficiency in ruminant animals. Experiments were undertaken to compare the rates of NH(3) production from different substrates in ruminal fluid in vitro and to assess the role of asaccharolytic bacteria in NH(3) production. Ruminal fluid was taken from four rumen-fistulated sheep receiving a mixed hay-concentrate diet. The calculated rate of NH(3) production from Trypticase varied from 1.8 to 19.7 nmol mg of protein(-1) min(-1) depending on the substrate, its concentration, and the method used. Monensin (5 micro M) inhibited NH(3) production from proteins, peptides, and amino acids by an average of 28% with substrate at 2 mg/ml, compared to 48% with substrate at 20 mg/ml (P = 0.011). Of the total bacterial population, 1.4% grew on Trypticase alone, of which 93% was eliminated by 5 micro M monensin. Many fewer bacteria (0.002% of the total) grew on amino acids alone. Nineteen isolates capable of growth on Trypticase were obtained from four sheep. 16S ribosomal DNA and traditional identification methods indicated the bacteria fell into six groups. All were sensitive to monensin, and all except one group (group III, similar to Atopobium minutum), produced NH(3) at >250 nmol min(-1) mg of protein(-1), depending on the medium, as determined by a batch culture method. All isolates had exopeptidase activity, but only group III had an apparent dipeptidyl peptidase I activity. Groups I, II, and IV were most closely related to asaccharolytic ruminal and oral Clostridium and Eubacterium spp. Group V comprised one isolate, similar to Desulfomonas piger (formerly Desulfovibrio pigra). Group VI was 95% similar to Acidaminococcus fermentans. Growth of the Atopobium- and Desulfomonas-like isolates was enhanced by sugars, while growth of groups I, II, and V was significantly depressed by sugars. This study therefore demonstrates that different methodologies and different substrate concentrations provide an explanation for different apparent rates of ruminal NH(3) production reported in different studies and identifies a diverse range of hyper-ammonia-producing bacteria in the rumen of sheep.

Animals↗

PubMed1974

Two pathways of glutamate fermentation by anaerobic bacteria.

Two pathways are involved in the fermentation of glutamate to acetate, butyrate, carbon dioxide, and ammonia-the methylaspartate and the hydroxyglutarate pathways which are used by Clostridium tetanomorphum and Peptococcus aerogenes, respectively. Although these pathways give rise to the same products, they are easily distinguished by different labeling patterns of the butyrate when [4-(14)C]glutamate is used as substrate. Schmidt degradation of the radioactive butyrate from C. tetanomorphum yielded equally labeled propionate and carbon dioxide, whereas nearly all the radioactivity of the butyrate from P. aerogenes was recovered in the corresponding propionate. This procedure was used as a test for the pathway of glutamate fermentation by 15 strains (9 species) of anaerobic bacteria. The labeling patterns of the butyrate indicate that glutamate is fermented via the methylaspartate pathway by C. tetani, C. cochlearium, and C. saccarobutyricum, and via the hydroxyglutarate pathway by Acidaminococcus fermentans, C. microsporum, Fusobacterium nucleatum, and F. fusiformis. Enzymes specific for each pathway were assayed in crude extracts of the above organisms. 3-Methylaspartase was found only in clostridia which use the methylaspartate pathway, including Clostridium SB4 and C. sticklandii, which probably degrade glutamate to acetate and carbon dioxide by using a second amino acid as hydrogen acceptor. High levels of 2-hydroxyglutarate dehydrogenase were found exclusively in organisms that use the hydroxyglutarate pathway. The data indicate that only two pathways are involved in the fermentation of glutamate by the bacteria analyzed. The methylaspartate pathway appears to be used only by species of Clostridium, whereas the hydroxyglutarate pathway is used by representatives of several genera.

Acetates↗

PubMed1975

Rapid screening of Veillonella by ultraviolet fluorescence.

Among 51 strains of anaerobic gram-negative cocci belonging to the family Veillonellaceae, all strains of Veillonella (V. parvula and V. alcalescens) displayed red fluorescence under long-wave (366 nm) ultraviolet light, whereas no Acidaminococcus or Megasphaera demonstrated fluorescence. In contrast to Bacteroides melaninogenicus, growth of Veillonella does not require hemin and menadione, and flourescence is rapidly lost upon exposure to air. The fluorescent component of a strain of V. parvula examined could not be extracted in solution with water, ether, methanol, or chloroform, but was readily extracted with 0.4 N NaOH. Spectrophotofluorometrically, the fluorescence maximum of this extract was 660 nm with an excitation maximum of 300 nm, when measured at pH 7.2 and 25 C. Coupled with the Gram stain, ultraviolet fluorescence may be a useful tool for rapid screening of Veillonella and is particularly helpful for detection and, isolation of this organism from mixed culture.

Air↗

PubMed2005

Sodium ion pumps and hydrogen production in glutamate fermenting anaerobic bacteria.

Anaerobic bacteria ferment glutamate via two different pathways to ammonia, carbon dioxide, acetate, butyrate and molecular hydrogen. The coenzyme B12-dependent pathway in Clostridium tetanomorphum via 3-methylaspartate involves pyruvate:ferredoxin oxidoreductase and a novel enzyme, a membrane-bound NADH:ferredoxin oxidoreductase. The flavin- and iron-sulfur-containing enzyme probably uses the energy difference between reduced ferredoxin and NADH to generate an electrochemical Na+ gradient, which drives transport processes. The other pathway via 2-hydroxyglutarate in Acidaminococcus fermentans and Fusobacterium nucleatum involves glutaconyl-CoA decarboxylase, which uses the free energy of decarboxylation to generate also an electrochemical Na+ gradient. In the latter two organisms, similar membrane-bound NADH:ferredoxin oxidoreductases have been characterized. We propose that in the hydroxyglutarate pathway these oxidoreductases work in the reverse direction, whereby the reduction of ferredoxin by NADH is driven by the Na+ gradient. The reduced ferredoxin is required for hydrogen production and the activation of radical enzymes. Further examples show that reduced ferredoxin is an agent, whose reducing energy is about 1 ATP 'richer' than that of NADH.

Amino Acid Sequence↗

PubMed1991

Synthesis and properties of (R)-2-hydroxyglutaryl-1-CoA. (R)-2-hydroxyglutaryl-5-CoA, an erroneous product of glutaconate CoA-transferase.

1) (R)-2-Hydroxyglutaryl-1-CoA was synthesised starting from (R)-5-oxotetrahydrofuran-2-carboxylic acid (gamma-lactone of (R)-2-hydroxyglutarate) which was converted to the acylchloride and condensed with N-capryloylcysteamine. The lactone ring of the resulting thiolester was opened by acid hydrolysis and the CoA derivative was obtained by transesterification. 2) Pure glutaconate CoA-transferase from Acidaminococcus fermentans catalysed the formation of the 1- and the 5-isomer of (R)-2-hydroxyglutaryl-CoA from acetyl-CoA and (R)-2-hydroxyglutarate. The isomers were separated by HPLC and characterised by their reaction with acetate under the catalysis of the CoA-transferase. V/Km for the 1-isomer was 80 times higher than that for the 5-isomer. 3) Studies with cell-free extracts from A. fermentans showed that only (R)-2-hydroxyglutaryl-1-CoA but not its 5-isomer was dehydrated to glutaconyl-1-CoA. The data indicate that (R)-2-hydroxyglutaryl-5-CoA is an erroneous product of glutaconate CoA-transferase which only occurs in vitro.

Acyl Coenzyme A↗

PubMed2002

[Trans-gram gene transfer: the case of beta-lactamases].

Lateral or horizontal gene transfer is a phenomenon that has influenced the evolution of microorganisms. Despite the evolutionary trend toward genetic isolation, lateral transfer seems to take place relatively frequently, bridging the gap between very separate species. The acquisition of foreign genes may have accelerated in recent years because of the increase in the adaptive needs of bacteria, particularly through the use of antibiotics. Transfer of genes encoding beta-lactamases from Gram-positive to Gram-negative bacteria (trans-gram transfer) may be suggested on the basis of sequence analysis. We found that the sequences of the beta-lactamases BRO-1 and ACl-1, from the Gram-negative bacterial organisms Moraxella and Acidaminococcus, respectively are abnormally placed among sequences from Gram-positive beta-lactamases in phylogenetic trees. In both cases, the topology of the enzyme (attached to the cellular membrane), the structure of the signal peptide, and the Shine-Dalgarno region suggest that these enzymes originated from Gram-positive organisms. Results remain inconclusive for Haemophilus ROB-1 beta-lactamase.

Gene Transfer, Horizontal↗