DNA-methyltransferase activities in Streptomyces antibioticus

Abstract To quantitate ammonia production by the intestinal flora, ammonia levels in arterial blood and the venous effluent of the small and large bowel of conventional, selectively decontaminated, germ-free and gnotobiotic rats were measured.
When the anaerobic flora was removed by decontamination a significant decrease in ammonia levels was observed in the effluent of both the small and large intestine. Decontamination of aerobic flora did not result in depression of ammonia production. Gnotobiotic rats colonised with an anaerobic flora or with a mixed aerobic and anaerobic flora, showed a slight increase in ammonia levels. No increase in ammonia production was observed when rats were colonised with aerobic flora. These results indicate that the Enterobacteriaceae were not responsible for ammonia generation.
The increase in ammonia levels after colonisation with anaerobic or mixed anaerobic/aerobic flora did not completely restore ammonia levels, despite reaching bacterial counts which were comparable to those in conventional rats. This may be explained by the limited number of species with which the rats were colonized. The finding that aerobic flora does not significantly contribute to ammonia production suggests that neomycin, known to be exclusively effective against aerobic flora, must have other effects to explain improvement of hepatic encephalopathy.     

Some aspects of the gastrointestinal microflora of germfree mice associated with cultured microfloras

Attempts are described to 'normalize' germfree mice by association with 3, 21 and 71 different intestinal bacterial cultures isolated from mice with an SPF flora. Germfree mice associated naturally with an SPF flora served as controls. Vital bacterial counts were determined by aerobic and anaerobic culture. Stomach and small intestine contained fewer bacteria per gram than caecum and large intestine. Aerobic vital counts from caecum and large intestine were higher in the experimental groups than in control mice. The aerobic and anaerobic flora in stomach and small intestine comprised mainly Gram-positive non-fusiform shaped rods. In the caecum and colon Gram-positive cocci predominated in the aerobic culture while in the anaerobic culture fusiform-shaped rods were prominent. Scanning electron microscopy of oesophagus, ileum, caecum and faeces demonstrated colonization of the oesophageal epithelium only after association with 71 bacterial strains; the filamentous bacteria present in the ileum of SPF mice were not found in the experimental groups and caecum and faeces contained mainly fusiform-shaped bacteria. Non-bacterial matter decreased in the caecum and faeces with increase in the complexity of the flora.     

Dietary Effects on the Composition of Fecal Flora of Rats

A long-term animal feeding experiment was conducted to compare the effect of meat and Wayne laboratory chow diets on the composition of rat fecal flora. Fecal bacteria were enumerated on selective media under both aerobic and anaerobic conditions. Intrarectal administration of N-methyl-N′ -nitro-N-nitro-soguanidine (MNNG) affected the count only on the phenylethylalcohol and veillonella-neomycin agars, whereas a slightly higher number of anaerobes appeared in the feces of rats that were treated with MNNG as compared with those obtained in the feces of untreated rats on the meat diet. In the absence of MNNG, feces of meat-fed rats yielded higher bacterial counts on aerobically incubated MacConkey agar, deoxycholate agar, and Pfizer selective enterococcus agar as well as higher numbers of clostridia on anaerobic egg yolk agar than did feces of rats on the Wayne diet. Feces of the group fed the Wayne diet produced more colonies on aerobic mitis-salivarius agar and lactobacillus agar as well as on anaerobically incubated phenylethylalcohol agar, veillonellaneomycin agar, bifidobacteria agar, fusobacterium (Nissui) agar, and kanamycin-vancomycin blood agar. These differences were consistent throughout the 1-year feeding period.     

The effect of diet on aerobic bacterial flora associated with intestine of Arctic charr (Salvelinus alpinus L.)

In order to extend the knowledge on the possible effect of diet on the gastrointestinal microbial community of fish, Arctic charr (Salvelinus alpinus L.) were fed diets containing high (23.7%) and low (6.4%) levels of carbohydrate. The number of viable aerobic and facultative aerobic bacteria associated with the digestive tract were not influenced by dietary regimen. A wide range of bacterial species was isolated, and the predominant bacterial species of both rearing groups were identified as Staphylococcus. There were, however, some differences in bacterial composition between the rearing groups, as well as inter-individual variations. For example, atypical Aeromonas salmonicida were isolated from the small and large intestine of two fish fed low dietary carbohydrate, while Aer. caviae-like isolates were found in the small intestine of four fish fed high carbohydrate. Non-motile Aeromonas spp. were found in the rearing group fed high dietary carbohydrate, but at low frequencies. Dietary manipulation seemed to influence the species composition of carnobacteria, Gram-positive rods, oxidase and catalase-negative and fermentative metabolism. Carnobacterium piscicola-like bacteria were only found in the small intestine, while C. mobile-like and Carnobacterium spp. were isolated from the large intestine of fish fed high carbohydrate. On the contrary, C. divergens-like isolates were found associated with the small and large intestine of fish fed low dietary carbohydrate.     

肠道菌群变化对实验小鼠肠黏膜免疫的影响

目的探讨肠道菌群变化对肠黏膜相关淋巴组织的影响。方法通过变性梯度凝胶电泳（Denatu-ring gradient gel electrophoresis,DGGE）法研究了三种不同级别实验小鼠即清洁级小鼠、SPF小鼠和普通小鼠肠道菌群的组成,并用免疫组织化学（immunohistochemistry,IHC）方法研究了此三种不同级别的实验小鼠肠黏膜相关淋巴组织sIgA阳性细胞分布情况。结果普通小鼠肠道细菌种类最多,其sIgA阳性细胞分布最多,肠道不同部位之间sIgA分布情况差异有显著性（P〈0.05）,小肠和大肠之间的阳性细胞分布差异极显著（P〈0.01）;其次是清洁级小鼠,其肠道不同部位之间菌种组成差异无显著性,小肠和大肠之间的阳性细胞分布差异有显著性（P〈0.05）;SPF小鼠肠道细菌种类最少,故其sIgA阳性细胞分布最少,且其肠道不同部位之间菌种组成差异无显著性,小肠和大肠之间的阳性细胞分布差异无显著性（P〉0.05）。结论随着动物微生物控制级别的增高,肠道微生物多样性递减;sIgA阳性细胞与肠道细菌种类正相关。     

Alteration in the endogenous intestinal flora of Swiss Webster mice by experimental Angiostrongylus costaricensis infection

The association between worm infections and bacterial diseases has only recently been emphasized. This study examined the effect of experimental Angiostrongylus costaricensis infection on endogenous intestinal flora of Swiss Webster mice. Eight mice aging six weeks were selected for this experiment. Four were infected with A. costaricensis and the other four were used as controls. Twenty eight days after the worm infection, all mice in both groups were sacrificed and samples of the contents of the ileum and colon were obtained and cultured for aerobic and anaerobic bacteria. In the mice infected with A. costaricensis there was a significant increase in the number of bacteria of the endogenous intestinal flora, accompanied by a decrease in the number of Peptostreptococcus spp. This alteration in the intestinal flora of mice infected by the nematode may help to understand some bacterial infections described in humans.     

Bacterial flora of newly caught Antarctic fish Notothenia neglecta

Summary The heterotrophic bacterial flora of Antarctic fish Notothenia neglecta was studied in Potter Cove (King George Island, South Shetland Islands). Quantitative and qualitative analysis of aerobic bacteria from sea water, skin, stomach and intestine were carried out. In addition, anaerobic flora of stomach and intestine was studied and compared. Pseudomonas was dominant in sea water samples but, neither skin nor digestive tract samples showed to be rich in this genus. Stomach flora showed variable results between samples. The gut flora was composed almost exclusively of Vibrio. Despite extreme environmental conditions this Antarctic fish show an intestinal indigenous microflora very similar to warmer waters fish. Several factors, that we discussed, could be determining the Vibrio dominance in the gut of marine teleosts.     

Effects of Systemic Demethylchlortetracycline on Human Cutaneous Microflora

The aerobic flora of the axilla and forehead of 20 normal human subjects was studied through a 3-week course of 600 mg of demethylchlortetracycline daily and a 3-week follow-up. In general in the axilla, an initial fall in bacterial density was followed by recovery in numbers due to the proliferation of resistant coagulase-negative cocci and diminution of the lipophilic diphtheroid group of bacteria within 1 week of treatment. During the remainder of the treatment period, the flora was essentially stable in both density and composition. In the follow-up phase, the initial flora was slowly re-established but resistant cocci persisted for more than 3 weeks. On the forehead the fall in density was slower and recovery during treatment was incomplete. Resistant coagulase-negative cocci became dominant and persisted through the follow-up phase. In two individuals, temporary colonization of the axilla by Staphylococcus aureus was seen.     

Microbial changes during oil decomposition in soil

An examination has been made of the changes in bacterial and fungal populations during the decomposition of oil in contaminated soil. The number of aerobic and anaerobic bacteria and the length of mycelium increased in the oily soil whereas the number of CFU (= colony forming units) of fungi was highest in a control soil. The percentage of oil-utilizing fungi increased from 60% to 82%, while the bacterial utilization figure increased from 3% to 50%. The important oil-utilizing fungus Scolecobasidium appeared only in the oily soil, but otherwise the composition of the fungal flora changed only little after addition of oil. In laboratory experiments the chemical Pajab FI was shown to increase microbial activity.     

An anaerobic continuous-flow culture model of interactions between intestinal microflora and Candida albicans

Summary The finding by earlier workers that Escherichia coli suppressed the growth of Candida albicans in vitro or in gnotobiotic mice has led to numerous, erroneous conclusions regarding the identity of the organisms and mechanisms responsible for the suppression of Candida in the gut. This is due, in part, to the fact that nearly all studies to date have not reflected interactions as they occur in the intestinal tract. This paper describes a series of experiments that establish that an anaerobic continuous-flow (CF) culture model, of the ecology of the large intestinal flora reproduces interactions between bacteria and Candida as they occur in the large intestine. This was determined in the following ways. (i) Bacterial counts in CF cultures of conventional mouse cecal flora or human fecal flora closely resembled that found in the mouse intestine and human feces. (ii) Dense layers of bacterial growth that formed on the glass walls of the CF culture vessels resembled bacterial populations that colonize intestinal mucosa. (iii) Total and individual levels of certain metabolic end-products of the predominant anaerobic bacterial flora present in CF cultures coincided with those found in the large intestine of conventional mice or human feces used to establish the CF cultures. (iv) C. albicans was eliminated from CF cultures of mouse cecal flora at a rate similar to that of untreated experimental animals. (v) Contents of CF cultures fed to antibiotic-treated mice redressed several cecal abnormalities, and suppressed Candida populations to levels found in conventional animals. Thus, a number of complex ecological mechanisms were maintained in CF cultures which normally control Candida populations in the large intestine. It is suggested, therefore, that the CF culture model should help to further define the mechanisms which control C. albicans and other fungi in the intestinal tract, as well as define which components of the indigenous microflora are responsible for suppression of Candida in the gut.     

Aerobic bacterial flora from the digestive tract of the common vampire bat, Desmodus rotundus (Chiroptera: Phyllostomidae)

This study addresses the composition of microbial flora in the vampire bat (Desmodus rotundus) primarily because all available data are outdated, and because of the economical significance of this bat species. Twenty-one bats were collected and their aerobic bacteria documented separately for stomach and intestine. Bacteria were identified through the Analytical Profile Index (API), and results analyzed with the APILAB software. A total of thirty bacterial species were isolated from sixteen females and five males. The most common species were Escherichia coli and Staphylococcus aureus, although other bacteria, such as Acinetobacterjohnsonii, Enterobacter sakazakii, Staphylococcus chromogenes, S. hyicus and S. xylosus were also common. The number of species found in the stomach and intestine was significantly different, and the intestine presented a higher diversity compared to the stomach. This has previously been found in other mammals and it is attributed to a reduction of acidity. Most of the species found in this study are considered normal components of the digestive tract of mammals, although other bacteria common in the skin of mammals and from aquatic environments were found. Bacteria from the skin may invade the vampire's stomach and/or intestine when the bat has contact with its prey, and may suggest that the vampire's feeding habit facilitates the invasion of other microbes not common in its digestive tract. The fact that bacteria from aquatic environments were also found suggests that D. rotundus, as previously found by other researchers, drinks free water when available, and water may be another source of microbial invasion.     

Response of intestinal flora of laboratory-reared leopard frogs (Rana pipiens) to cold and fasting.

The bacterial flora of the large intestine was examined in 35 laboratory-reared leopard frogs (Rana pipiens) subjected to one of the following four treatments: (i) normal feeding at 21 degrees C (10 frogs); (ii) fasting for 2 weeks at 21 degrees C (8 frogs); (iii) chilling for 1 week at 4 degrees C (9 frogs); and (iv) simulated hibernation for 3 weeks at 4 degrees C (8 frogs). Bacteria from the intestinal contents and mucosa were counted microscopically and by colony counting after strictly anaerobic culturing. The predominant bacteria were isolated and partially characterized. Fasting for 2 weeks produced no significant changes in total counts or in the types of bacteria cultured. Chilling, whether rapid or in the course of simulated hibernation, was associated with a decrease in the numbers and variety of bacteria. Thus it appears that the lowering of temperature rather than the absence of food is the important factor in the reduction of bacterial flora seen in hibernating frogs. However, the bacteria showed some adaptation to the low temperature, as the longer the host had been at 4 degrees C, the higher the proportion of bacteria which could grow when cultured at that temperature.     

Characteristic faecal flora of NC mice

The composition of faecal flora of NC mice was compared with that of CF #1 mice. NC- and CF #1-germfree (GF) mice were cage-mated with NC- or CF #1-conventional (CV) mice in an isolator. The faecal flora of these ex-GF mice was dependent on the recipient mouse strain modifying colonization by the donor mouse bacteria. Although NC- and CF #1-pups removed by hysterectomy were fostered to different strains, almost all these mice at 8 weeks old had a strain characteristic pattern of faecal flora regardless of the foster strains. In GF mice mono-associated with a Lactobacillus strain or a Bifidobacterium strain isolated from faeces of CV mice, the numbers of these bacteria in the stomach and small intestine of NC mice were lower than those of CF #1 mice. In GF mice associated with chloroform-treated faeces of CV mice, and a Lactobacillus strain or a Bifidobacterium strain, the numbers of these bacteria in the stomach and all parts of the intestine of NC mice were considerably lower than those of CF #1 mice. These results suggested that the composition of faecal flora of NC mice were characteristic, i.e. the fact that the numbers of lactobacilli were low compared with CF #1 mice with ordinary faecal flora and the colonization of bifidobacteria, peptococcaceae and eubacteria on ES agar in NC mice intestine differed, was due to genetic factors.     

The presence of bacteria and yeast like fungi in specimens from surgical patients

The aim of this study was to determine the incidence of Candida spp. strains in specimens obtained from surgically treated patients as well as to analyze the accompanying bacterial flora, both aerobic and anaerobic. The material came from two groups of patients. In the first group consisting of patients operated for colon and rectum carcinoma, the samples included peritoneal fluid, colon or rectum bioptates, pus, blood, and wound swabs. In the other group, biopsy material and smears from post operation wounds were taken from patients who underwent a surgical treatment of larynx carcinoma. Altogether, 282 various clinical specimens from 165 patients were analysed, and 41 Candida spp. strains were isolated: 39 strains of C. albicans and 2 strains of C. tropicalis. In 20 out of 41 specimens infected with Candida spp. (48.8%) the co-infection with bacterial aerobic flora was found. In 10 cases (24.4%), the fungi were isolated together with aerobic and anaerobic bacterial flora, whereas in 2 specimens (4.9%) the anaerobes and Candida albicans were diagnosed. The remaining 9 samples showed only the presence of Candida spp. (21.9%). From among aerobic bacterial flora Enterococcus spp. strains (n = 17) and Gram negative rods from Enterobacteriaceae family (n = 13) were the most frequently isolated. The bacterial strains of Streptococcus spp. (n = 5), Pseudomonas spp. (n = 3), Staphylococcus spp. and Corynebacterium spp. (2 strains, both) were identified more rarely. Bacteroides spp. were the most frequent members of bacterial anaerobic flora (n = 10). Other isolated anaerobic bacteria were classified as Fusobacterium spp. or Peptostreptococcus spp. (1 strain each). E. coli and Enterococcus spp. strains of aerobic bacterial flora were more frequently isolated together with Candida spp. CONCLUSIONS: (i) Mixed bacterial flora was found to predominate in the clinical material from the patients after surgery. (ii) Candida spp. were most frequently found together with aerobic bacterial flora.     

Microbiological quality changes in the intestine of hybrid tilapia (Oreochromis niloticus x Oreochromis aureus) in fresh and frozen storage condition

AIMS: The goal of this study was to monitor the quantitative and qualitative bacterial flora in the intestine of hybrid tilapia in fresh fish and fish kept in frozen storage conditions for 1 year. METHODS AND RESULTS: Quantitative and qualitative analyses of the bacterial flora associated with the intestine of hybrid tilapia (Oreochromis niloticus x Oreochromis aureus) in fresh fish and fish kept in frozen storage conditions for 1 year were carried out. In fresh and frozen fish, aerobic plate count (APC) ranged from 1.6 +/- 1.2 x 10(8) to 1.5 +/- 0.9 x 10(5) CFU g(-1) in the intestine of tilapia collected from pond 1, 8.7 +/- 2.3 x 10(7) to 6.5 +/- 3.8 x 10(4) CFU g(-1) in the intestine of tilapia from pond 2, and 1.9 +/- 2.9 x 10(8) to 6.2 +/- 2.8 x 10(4) CFU g(-1) in the intestine of tilapia from pond 3. APC for all the groups of fish decreased c. 2-log cycles after 1 months frozen storage; thereafter, counts slowly declined during frozen storage for 1 year. Altogether, 16 bacterial genera were identified: Gram-negative rods (67%) dominated. Both in fresh and frozen conditions, four bacterial species viz. Shewanella putrefaciens, Corynebacterium urealyticum, Aeromonas hydrophila and Flavobacterium sp. were always present, with a prevalence of 10% in most cases. Shewanella putrefaciens was the most dominant organism (15% of the total isolates) throughout the studied period. During frozen storage some of the bacteria were not recovered, but most of the bacteria survived after prolonged freezing. CONCLUSIONS: This study describes the aerobic heterotrophic microflora found in the intestine of fresh and frozen tilapia. The unique aspect of this study concerns the data revealing the micro-organisms, which are viable after prolonged freezing. Contamination of edible portions of fish could originate from gastrointestinal sources. SIGNIFICANCE AND IMPACT OF THE STUDY: The present results may enhance knowledge in controlling the storage life of fish, and fish product quality. Bacterial activity is by far the most important factor influencing fish quality, so bacterial numbers can be used as an index of quality. Storage of frozen tilapia without evisceration could be avoided.     

Bacterial community in the intestine of the sea urchin Strongylocentrotus intermedius during digestion of Macrocystis pyrifera

Denaturing gradient gel electrophoresis (DGGE) was used to study the bacterial community changes in the intestine of the sea urchin Strongylocentrotus intermedius during the digestion of Macrocystis pyrifera. The distinct bands in DGGE gels were sequenced, and the results indicated that the bacterial community in the large and small intestine varied at different periods of digestion. Samples from the large intestine included six specific bands belonging to the genus Psychromonas, whereas samples from the small intestine included eight specific bands representing Psychromonas, Shewanella, Saccharophagus degradans, and Nitrosomonas eutropha. The bacterial flora differed at different periods of digestion. The increase in the microbial community species in the large intestine was not obvious compared with that in the small intestinal microbial community. Several microbes involved in degradation of M. pyrifera were found in the intestine of sea urchin.     

Characterization of the bacterial population structure in an anaerobic-aerobic activated sludge system on the basis of respiratory quinone profiles

Bacterial respiratory quinones were used as biomarkers for studying the bacterial population structure, especially the content of Acinetobacter species, in a laboratory-scale anaerobic-aerobic activated sludge system and in the standard aerobic system. All tested sludges contained both ubiquinone and menaquinone, with a molar ratio of about 1:0.5. High-performance liquid chromatography showed that ubiquinone with eight isoprene units (Q-8) was present as the predominant ubiquinone, Q-10 was the second most common type, and Q-9 and other homologs were minor components in the anaerobic-aerobic sludge and the standard aerobic sludge. Bacteriological examination indicated that, in both sludge systems, Q-8-containing bacteria constituted a large proportion of the aerobic heterotrophic bacterial flora, but only a few strains with Q-9 were found. These findings demonstrate that the population of Acinetobacter species, which contain Q-9 as the major quinone, is negligible in those environments. The present results suggest that the introduction of anaerobic conditions into the aerobic batch process has little influence on the bacterial community structure.     

Characterization of the bacterial population structure in an anaerobic-aerobic activated sludge system on the basis of respiratory quinone profiles.

Bacterial respiratory quinones were used as biomarkers for studying the bacterial population structure, especially the content of Acinetobacter species, in a laboratory-scale anaerobic-aerobic activated sludge system and in the standard aerobic system. All tested sludges contained both ubiquinone and menaquinone, with a molar ratio of about 1:0.5. High-performance liquid chromatography showed that ubiquinone with eight isoprene units (Q-8) was present as the predominant ubiquinone, Q-10 was the second most common type, and Q-9 and other homologs were minor components in the anaerobic-aerobic sludge and the standard aerobic sludge. Bacteriological examination indicated that, in both sludge systems, Q-8-containing bacteria constituted a large proportion of the aerobic heterotrophic bacterial flora, but only a few strains with Q-9 were found. These findings demonstrate that the population of Acinetobacter species, which contain Q-9 as the major quinone, is negligible in those environments. The present results suggest that the introduction of anaerobic conditions into the aerobic batch process has little influence on the bacterial community structure.     

ERIC-PCR指纹图谱技术分析糖尿病小鼠肠道细菌群落变化

目的通过比较1型糖尿病模型组和空白对照组雄性小鼠肠道菌群结构的变化,探索糖尿病造模与肠道菌群的关系。方法收集造模2周后空白对照组(n=5)、STZ造模成功组(n=5)和造模不成功组(n=3)ICR小鼠的新鲜粪便样品,提取粪便样品的总DNA,ERIC-PCR扩增形成DNA指纹图谱,借助多变量统计分析方法研究各组样品肠道菌群结构上的异同。结果ERIC-PCR指纹图谱结合偏最小二乘法(PLS-DA)分析表明造模成功组和造模不成功组小鼠的肠道菌群结构显著区别于空白对照组,而造模不成功组小鼠的肠道菌群结构与造模成功组仍有一定的区别。结论STZ诱导的1型糖尿病会造成小鼠的肠道菌群结构的变化,而部分小鼠造模失败可能与这些小鼠的肠道菌群结构有关。     

The predominant anaerobe from the spiral intestine of hatchery-raised sturgeon (Acipenser transmontanus), a new Bacteroides species

The anaerobic and aerobic bacterial flora from the spiral intestine of hatchery-raised sturgeon were enumerated. Among the obligate anaerobes, a new bacteroidelike organism was isolated and found to be the predominant strict anaerobe. The organism is Gram-negative, produces the fermentation products acetate, succinate, propionate and H₂. The mol % G+C of DNA from various strains ranged from 33.17–33.65. The optimum sodium concentration for this organism was found to be 137 mM; the sodium level in the sturgeon spiral intestine ranged from 94.5–110.0mM. Based on these and other physiological characteristics, the organism appears to be a new species of the genus Bacteroides.Non-common abbreviations GI Gastrointestinal - VFA Volatile fatty acid - SI Spiral intestine - GLC Gas-liquid chromatography