Anaerobic fecal bacteria of the baboon.

The predominant bacterial genera of baboon feces were enumerated and identified by established procedures. The predominant genera isolated were Lactobacillus, Eubacterium, Streptococcus, and Bacteroides.     

Anaerobic bacteria from hypersaline environments.

Strictly anaerobic halophiles, namely fermentative, sulfate-reducing, homoacetogenic, phototrophic, and methanogenic bacteria are involved in the oxidation of organic carbon in hypersaline environments. To date, six anaerobic fermentative genera, containing nine species, have been described. Two of them are homoacetogens. Six species belong to the family Haloanaerobiaceae, as indicated by their unique 16S rRNA oligonucleotide sequences. Desulfohalobium retbaense and Desulfovibrio halophilus represent the only two moderately halophilic sulfate reducers so far reported. Among anoxygenic phototrophic anaerobes, a few purple bacteria with optimal growth at salinities between 6 and 11% NaCl have been isolated from hypersaline habitats. They belong to the genera Rhodospirillum, Chromatium, Thiocapsa, and Ectothiorhodospira. The commonest organisms isolated so far are Chromatium salexigens, Thiocapsa halophila, and Rhodospirillum salinarum. Extremely halophilic purple bacteria have most commonly been isolated from alkaline brines and require about 20 to 25% NaCl for optimal growth. They belong to the family Ectothiorodhospiraceae. Their osmoregulation involves synthesis or uptake of compatible solutes such as glycine-betaine that accumulate in their cytoplasm. The existence of methanogens in hypersaline environments is related to the presence of noncompetitive substrates such as methylamines, which originate mainly from the breakdown of osmoregulatory amines. Methanogenesis probably does not contribute to the mineralization of carbohydrates at NaCl concentrations higher than 15%. Above this concentration, sulfate reduction is probably the main way to oxidize H2 (although at rates too low to use up all the H2 formed) and occupies a terminal function kn the degradation of carbohydrates. Three genera and five species of halophilic methylotrophic methanogens have been reported. A bloom of phototrophic bacteria in the marine salterns of Salins-de-Giraud, located on the Mediterranean French coast in the Rhone Delta, is also described.     

Mortality of fecal bacteria in seawater.

We propose a method for determining the mortality rate for allochthonous bacteria released in aquatic environments without interference due to the loss of culturability in specific culture media. This method consists of following the disappearance of radioactivity from the trichloroacetic acid-insoluble fraction in water samples to which [3H]thymidine-prelabeled allochthonous bacteria have been added. In coastal seawater, we found that the actual rate of disappearance of fecal bacteria was 1 order of magnitude lower than the rate of loss of culturability on specific media. Minor adaptation of the procedure may facilitate assessment of the effect of protozoan grazing and bacteriophage lysis on the overall bacterial mortality rate.     

Anaerobic bacteria that dechlorinate perchloroethene.

In this study, we identified specific cultures of anaerobic bacteria that dechlorinate perchlorethene (PCE). The bacteria that significantly dechlorinated PCE were strain DCB-1, an obligate anaerobe previously shown to dechlorinate chlorobenzoate, and two strains of Methanosarcina. The rate of PCE dechlorination by DCB-1 compared favorably with reported rates of trichloroethene bio-oxidation by methanotrophs. Even higher PCE dechlorination rates were achieved when DCB-1 was grown in a methanogenic consortium.     

Anaerobic bacteria from the large intestine of mice.

Anaerobic bacteria from the colon of laboratory mice were enumerated and isolated using strict anaerobic techniques. Direct microscopic counts revealed 4.4 X 10(10) organisms in each gram (wet weight) of colon contents. Actual cultural counts averaged 3.2 X 10(10) organisms, which was 73% of the direct microscopic count. The tentatively identified genera were Bacteroides, Eubacterium, Fusobacterium, Lactobacillus, Peptostreptococcus, and Propionibacterium. Strains of Fusobacterium, Lactobacillus, Peptostreptococcus, and Propionibacterium were biochemically homogeneous. Strains of Bacteroides and Eubacterium, on the other hand, were biochemically heterogeneous and were subdivided into several distinct groups. The data indicate that many of the isolates are different from previously described species of the respective genera and may belong to new species.     

Isolation and identification of fecal bacteria from adult swine.

An examination of the fecal microflora of adult swine was made with regard to the efficiency of several roll tube media in enumeration and recovery of anaerobes, the effects of medium constituents on recovery, and the isolation and identification of the predominant kinds of bacteria. Total number of organisms by microscopic bacterial counts varied among fecal samples from 4.48 X 10(10) to 7.40 X 10(10) bacteria/g (wet weight). Comparison of different nonselective roll tube media indicated that about 30% of the fecal bacteria could be recovered with a rumen fluid (40%, vol/vol) medium (M98-5). Recoveries of 21 and 15%, respectively, were obtained with M10 and rumen fluid-glucose-cellobiose agar (RGCA) media. Rumen fluid, Trypticase, sugars, and CO2 gas phase were important components required for maximum recovery with this medium. Similar high recoveries of anaerobes were also obtained with M98-5 containing swine cecal extract of place in rumen fluid or M10 plus swine cecal extract. Significantly lower recoveries were observed with RCGA, media supplemented with swine fecal extracts, reinforced clostridial medium, brain heart infusion agar, and prereduced blood agar. Ninety percent of the bacteria isolated from roll tube media were gram positive and consisted of facultatively anaerobic streptococci, Eubacterium sp., Clostridium sp., and Propionibacterium acnes. The remainder of the flora (8%) included several other species of anaerobes and Escherichia coli. Rumen fluid (or volatile fatty acids), Trypticase, and yeast extract additions to basal media stimulated the growth of anaerobic strains. Variation in the relative proportions of the predominant fecal microflora was observed. This work indicates that satisfactory enumeration, isolation and cultivation of the predominant microflora in swine feces can be obtained when strict anaerobic culture methods and a rumen fluid medium are used.     

Anaerobic benzene degradation by bacteria

Benzene is a widespread and toxic contaminant. The fate of benzene in contaminated aquifers seems to be primarily controlled by the abundance of oxygen: benzene is aerobically degraded at high rates by ubiquitous microorganisms, and the oxygen‐dependent pathways for its breakdown were elucidated more than 50 years ago. In contrast, benzene was thought to be persistent under anoxic conditions until 25 years ago. Nevertheless, within the last 15 years, several benzene‐degrading cultures have been enriched under varying electron acceptor conditions in laboratories around the world, and organisms involved in anaerobic benzene degradation have been identified, indicating that anaerobic benzene degradation is a relevant environmental process. However, only a few benzene degraders have been isolated in pure culture so far, and they all use nitrate as an electron acceptor. In some highly enriched strictly anaerobic cultures, benzene has been described to be mineralized cooperatively by two or more different organisms. Despite great efforts, the biochemical mechanism by which the aromatic ring of benzene is activated in the absence of oxygen is still not fully elucidated; methylation, hydroxylation and carboxylation are discussed as likely reactions. This review summarizes the current knowledge about the ‘key players’ of anaerobic benzene degradation under different electron acceptor conditions and the possible pathway(s) of anaerobic benzene degradation.     

Mortality of fecal bacteria in seawater

We propose a method for determining the mortality rate for allochthonous bacteria released in aquatic environments without interference due to the loss of culturability in specific culture media. This method consists of following the disappearance of radioactivity from the trichloroacetic acid-insoluble fraction in water samples to which [3H]thymidine-prelabeled allochthonous bacteria have been added. In coastal seawater, we found that the actual rate of disappearance of fecal bacteria was 1 order of magnitude lower than the rate of loss of culturability on specific media. Minor adaptation of the procedure may facilitate assessment of the effect of protozoan grazing and bacteriophage lysis on the overall bacterial mortality rate.     

Anaerobic bacteria in clinical infections

The findings of 275 cultures from routine clinical specimens obtained from lesions in different sites of body, during a period of 11 months, are presented. The clinical specimens were obtained from surgical wounds, abdominal infections, orthopaedic operations, biliary tract infections and pleuropulmonary infections. The total number of positive cultures including both aerobes and anaerobes was 203 out of 275 (73.8%). Of the 38 cultures positive for anaerobes, 29 (76.3%) grew both aerobic and anaerobic bacteria, while in nine (23.7%) cultures only anaerobes were found. A total of 42 strains of anaerobic bacteria were isolated. The majority of them were found in clinical specimens obtained from abdominal infections (62%), while a low percentage (3.6%) was found in specimens from orthopaedic operations. Strains belonging to the genus Bacteroides were the most frequently isolated anaerobes, accounting for 35.7% of the total, followed by Clostridia 28.5%, Peptostreptococci 23.8% and Prevotella 12%.     

Anaerobic bacteria that dechlorinate perchloroethene

In this study, we identified specific cultures of anaerobic bacteria that dechlorinate perchlorethene (PCE). The bacteria that significantly dechlorinated PCE were strain DCB-1, an obligate anaerobe previously shown to dechlorinate chlorobenzoate, and two strains of Methanosarcina. The rate of PCE dechlorination by DCB-1 compared favorably with reported rates of trichloroethene bio-oxidation by methanotrophs. Even higher PCE dechlorination rates were achieved when DCB-1 was grown in a methanogenic consortium.     

Anaerobic bacteria as producers of antibiotics

Anaerobic bacteria are the oldest terrestrial creatures. They occur ubiquitously in soil and in the intestine of higher organisms and play a major role in human health, ecology, and industry. However, until lately no antibiotic or any other secondary metabolite has been known from anaerobes. Mining the genome sequences of Clostridium spp. has revealed a high prevalence of putative biosynthesis genes (PKS and NRPS), and only recently the first antibiotic from the anaerobic world, closthioamide, has been isolated from the cellulose degrading bacterium Clostridium cellulolyticum. The successful genetic induction of antibiotic biosynthesis in an anaerobe encourages further investigations of obligate anaerobes to tap their hidden biosynthetic potential.     

Sunlight inactivation of fecal bacteriophages and bacteria in sewage-polluted seawater.

Sunlight inactivation rates of somatic coliphages, F-specific RNA bacteriophages (F-RNA phages), and fecal coliforms were compared in seven summer and three winter survival experiments. Experiments were conducted outdoors, using 300-liter 2% (vol/vol) sewage-seawater mixtures held in open-top chambers. Dark inactivation rates (k(D)s), measured from exponential survival curves in enclosed (control) chambers, were higher in summer (temperature range: 14 to 20 degrees C) than in winter (temperature range: 8 to 10 degrees C). Winter k(D)s were highest for fecal coliforms and lowest for F-RNA phages but were the same or similar for all three indicators in summer. Sunlight inactivation rates (k(S)), as a function of cumulative global solar radiation (insolation), were all higher than the k(D)s with a consistent k(S) ranking (from greatest to least) as follows: fecal coliforms, F-RNA phages, and somatic coliphages. Phage inactivation was exponential, but bacterial curves typically exhibited a shoulder. Phages from raw sewage exhibited k(S)s similar to those from waste stabilization pond effluent, but raw sewage fecal coliforms were inactivated faster than pond effluent fecal coliforms. In an experiment which included F-DNA phages and Bacteroides fragilis phages, the k(S) ranking (from greatest to least) was as follows: fecal coliforms, F-RNA phages, B. fragilis phages, F-DNA phages, and somatic coliphages. In a 2-day experiment which included enterococci, the initial concentration ranking (from greatest to least: fecal coliforms, enterococci, F-RNA phages, and somatic coliphages) was reversed during sunlight exposure, with only the phages remaining detectable by the end of day 2. Inactivation rates under different optical filters decreased with the increase in spectral cutoff wavelength (50% light transmission) and indicated that F-RNA phages and fecal coliforms are more susceptible than somatic coliphages to longer solar wavelengths, which predominate in seawater. The consistently superior survival of somatic coliphages in our experiments suggests that they warrant further consideration as fecal, and possibly viral, indicators in marine waters.     

Tauroconjugation of cholic acid stimulates 7 alpha-dehydroxylation by fecal bacteria.

We examined the effect of the type of cholic acid conjugation (taurine-conjugated, glycine-conjugated, or unconjugated cholic acid) on cholic acid 7 alpha-dehydroxylation by intestinal flora. Cholic acid 7 alpha-dehydroxylation in fecal cultures, in cultures of a defined limited flora consisting of a mixture of seven bacterial species isolated from the intestinal tract, and in a binary culture of a 7 alpha-dehydroxylating Clostridium species plus a cholic acid-deconjugating Bacteroides species was studied. We found that tauroconjugation of cholic acid significantly (P < 0.05) increased bacterial 7 alpha-dehydroxylation of cholic acid into deoxycholic acid from 34 to 55% in fecal cultures, from 45 to 60% in defined limited fecal cultures, and from 75 to 100% in binary cultures. Equimolar concentrations of free taurine did not stimulate 7 alpha-dehydroxylation in fecal cultures or in the defined limited flora, but free taurine did stimulate 7 alpha-dehydroxylation in the binary culture. In the binary culture of Clostridium species strain 9/1 plus Bacteroides species strain R1, the minimal flora capable of increased 7 alpha-dehydroxylation of taurocholic acid, strain R1 deconjugated taurine and rapidly reduced it to H2S. Bacteroides species strain R1 did not grow unless taurine or another appropriate reducible sulfur source was present. Clostridium species strain 9/1 did not grow or 7 alpha-dehydroxylate unless H2S or another source of reduced sulfur was present. We conclude that the increased 7 alpha-dehydroxylation of tauroconjugated cholic acid depends on the reduction of taurine to H2S, which is a necessary growth factor for the 7 alpha-dehydroxylating bacteria.     

Inactivation of fecal bacteria in drinking water by solar heating.

We report simulations of the thermal effect of strong equatorial sunshine on water samples contaminated with high populations of fecal coliforms. Water samples, heavily contaminated with a wild-type strain of Escherichia coli (starting population = 20 x 10(5) CFU/ml), are heated to those temperatures recorded for 2-liter samples stored in transparent plastic bottles and exposed to full Kenyan sunshine (maximum water temperature, 55 degrees C). The samples are completely disinfected within 7 h, and no viable E. coli organisms are detected at either the end of the experiment or a further 12 h later, showing that no bacterial recovery has occurred. The feasibility of employing solar disinfection for highly turbid, fecally contaminated water is discussed.     

粪菌移植途径的临床应用现状

人体肠道内寄居着数量庞大、种类繁多的微生物,形成肠道微生态稳态,而肠道微生态失衡与多种肠内、肠外疾病相关。随着人们对肠道菌群在宿主健康及疾病中作用的深入认识,粪菌移植(faecal microbiota transplantation, FMT)被给予厚望,其作为重建肠道菌群的有效手段,已成功应用于艰难梭菌感染(Clostridioides difficile infection, CDI)等疾病的治疗和探索性研究,并被认为是近年的突破性医学进展。随着近几年FMT研究的深入,人们发现FMT对各系统疾病皆有潜在的治疗作用。在1990年之前,菌群移植都是经灌肠实施,近几年随着粪菌移植研究的深入,粪菌移植途径也呈多样化发展。本文对粪菌移植途径、临床应用和存在的问题等作一综述。     

Anaerobic degradation of 2-fluorobenzoate by benzoate-degrading, denitrifying bacteria.

Three strains of anaerobically benzoate-degrading, denitrifying bacteria of the genus Pseudomonas were able to grow on 2-fluorobenzoate as the sole carbon and energy source. Fluoride ion release was stoichiometric, and the reduction of dissolved organic carbon indicated total degradation. Cells grown anaerobically with benzoate were adapted for immediate growth with 2-fluorobenzoate, and both compounds were substrates for an inducible benzoyl-coenzyme A synthetase, the initial enzyme of anaerobic degradation. It is proposed that fluoride is eliminated gratuitously by a regioselective reaction in a sequence common to both carbon sources. Benzoate, but not 2-fluorobenzoate, was oxidized by aerobically grown cells.     

Anaerobic degradation of cresols by denitrifying bacteria

The initial reactions in anaerobic metablism of methylphenols (cresols) and dimethylphenols were studied with denitrifying bacteria. A newly isolated strain, possibly a Paracoccus sp., was able to grow on o-or p-cresol as sole organic substrate with a generation time of 11 h; o-or p-cresol was completely oxidized to CO₂ with nitrate being reduced to N₂. A denitrifying Pseudomonas-like strain oxidized m-or p-cresol as the sole organic growth substrate completely to CO₂ with a generation time of 14 h. Demonstration of intermediates and/or in vitro measurement of enzyme activities suggest the following enzymatic steps:(1) p-Cresol was metabolized by both strains via benzoyl-CoA as central intermediate as follows: p-cresol 4-OH-benzaldehyde 4-OH-benzoate 4-OH-benzoly-CoA benzoyl-CoA. Oxidation of the methyl group to 4-OH-benzaldehyde was catalyzed by p-cresol methylhydroxylase. After oxidation of the aldehyde to 4-OH-benzoate, 4-OH-benzoyl-CoA is formed by 4-OH-benzoyl-CoA synthetase; subsequent reductive dehydroxylation of 4-OH-benzoyl-CoA to benzoyl-CoA is catalyzed by 4-OH-benzoyl-CoA reductase (dehydroxylating).(2) o-Cresol was metabolized in the Paracoccus-like strain via 3-CH₃-benzoyl-CoA as central intermediate as follows: o-cresol 4-OH-3-CH₃-benzoate 4-OH-3-CH₃-benzoyl-CoA 3-CH₃-benzoyl-CoA. The following enzymes were demonstrated: (a) An enzyme catalyzing an isototope exchange reaction between ¹⁴CO₂ and the carboxyl of 4-OH-3-CH₃-benzoate; this activity is thought to be a partial reaction catalyzed by an o-cresol carboxylase. (b) 4-OH-3-CH₃-benzoyl-CoA synthetase (AMP-forming) activating the carboxylation product 4-OH-3-CH₃-benzoate to its coenzyme A thioester. (c) 4-OH-3-CH₃-benzoyl-CoA reductase (dehydroxylating) catalyzing the reductive dehydroxylation of the 4-hydroxyl group with reduced benzyl viologen as electron donor to yield 3-CH₃-benzoyl-CoA. This thioester may also be formed by action of a coenzyme A ligase when 3-CH₃-benzoate is metabolized. 2,4-Dimethylphenol was metabolized via 4-OH-3-CH₃-benzoate and further to 3-CH₃-benzoyl-CoA.(3) The initial reactions of anaerobic metabolism of m-cresol in the Pseudomonas-like strain were not resolved. No indication for the oxidation of the methyl group nor for the carboxylation of m-cresol was found. In contrast, 2,4-and 3,4-dimethylphenol were oxidized to 4-OH-3-CH₃-and 4-OH-2-CH₃-benzoate, respectively, probably initiated by p-cresol methylhydroxylase; however, these compounds were not metabolized further.The hydroxyl and methyl groups are abbreviated as OH-and CH₃-, respectively     

Investigation of the survival characteristics of Rhodococcus coprophilus and certain fecal indicator bacteria.

Rhodococcus coprophilus and Clostridium perfringens survived in fresh water samples held at 5, 20, and 30 degrees C for over 17 weeks, whereas Escherichia coli and fecal streptococci disappeared after 5 weeks at all three temperatures. R. coprophilus survived for more than 8 months in sterilized sewage and deionized water at all three temperatures, whereas in normal sewage held at 20 degrees C, the survival time was 12 to 26 weeks. In samples held at 30 degrees C, survival times were shorter, probably because of interbacterial competition or protozoal predation. The results indicate that R. coprophilus may be a useful indicator of the presence of remote fecal pollution of farm animal origin, but not of recent pollution, when enumerated alone in polluted waters or wastewaters.