Molecular Changes in Entamoeba histolytica in Response to Bacteria1

Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme-linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture.     

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。     

Molecular monitoring of the intestinal flora by denaturing high performance liquid chromatography

Gut flora analysis is hampered by the complexity of the intestinal microbiota and by inherent limitations of culture-based approaches. Therefore, culture-independent molecular methods based upon 16S rRNA gene analysis were applied successfully for the analysis of complex microbial communities. However, generally accepted and validated profiling methods such as denaturing and temperature gradient gel electrophoresis (DGGE/TGGE) are still laborious and time consuming. Thus, we adapted the separation of amplified bacterial 16S rRNA gene fragments by denaturing high performance liquid chromatography (DHPLC) using the WAVE Microbial Analysis System as a rapid and convenient means to display complex intestinal bacterial communities and to monitor changes in the gut flora. The separation of 16S rRNA gene fragments amplified from reference strains representing main gut bacterial populations and from human stool samples revealed that DHPLC analysis effectively detects bacterial groups predominant in the human gut flora. The investigation of faecal samples from hospitalized patients before, during and after antibiotic therapy showed that PCR-based DHPLC can be used to monitor gut flora changes. Results from DHPLC analysis were comparable with DGGE profiles generated from the same samples, demonstrating that the adapted DHPLC protocol is well suited for the analysis of complex microbial communities.     

Comparison of the gut bacterial flora of start-feeding larval turbot reared under different conditions

P.D. MUNRO, A. BARBOUR AND T.H. BIRKBECK. 1994. Bacterial colonization of the gut of turbot larvae coincided with the start of feeding and the gut microflora was then dominated by Vibrio and Aeromonas species. The detection of similar bacterial isolates over several days indicated the presence of a stable microflora during the rotifer feeding stage, probably reflecting a stable flora in the rotifer culture. There was no correlation between the number of bacteria in the gut and larval survival rates; incidences of high mortalities were not associated with high numbers of recognized fish pathogens, although an Aeromonas species was implicated as an opportunistic pathogen. Potential pathogens were isolated, albeit in low numbers, from batches of apparently healthy larvae with high survival rates. It is probable that the bacterial flora plays an important role in determining the survival of larval fish and that the establishment of a beneficial flora is possible, although the criteria for such a flora have still to be elucidated.     

人工辅助投食对滇金丝猴肠道微生物群落的影响

【背景】肠道菌群与宿主的消化吸收、免疫抵抗和行为等息息相关,并受宿主的饮食、生活环境等因素影响。【目的】人工辅助投食能增加野生动物的营养摄入,但对其肠道菌群影响的研究较少。【方法】以云南白马雪山国家级自然保护区内的野生和人工辅助投食滇金丝猴群的新鲜粪便为材料,通过高通量测序探究人工辅助投食对猴群肠道菌群的影响。【结果】人工辅助投食的猴群肠道菌群丰富度、均匀度及谱系多样性更高,并且个体间群落组成差异更小。通过多级物种差异判别分析(linear discriminant analysis effect size, LEfSe)分析发现,人工辅助投食对20种不同分类水平的细菌相对丰度有影响,包括提升了厚壁菌门(Firmicutes)等8种类群的相对丰度,降低了变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)等12种类群的相对丰度。通过构建微生物相关网络发现,野生猴群肠道菌群网络结构更加复杂,鲁棒性更高。京都基因与基因组百科全书(Kyoto encyclopedia of genes and genomes, KEGG)功能预测结果表明,人工辅助投食降低了猴群肠...     

Gut flora enhance bacterial clearance in lung through toll-like receptors 4

Background  

The influence of the gut flora on lung inflammatory reaction against bacterial challenge remains undefined. This study was designed to investigate whether gut flora enhances lung defense against E.coli pneumonia through TLR4 signaling.     

Midgut Microbiota of the Malaria Mosquito Vector Anopheles gambiae and Interactions with Plasmodium falciparum Infection

The susceptibility of Anopheles mosquitoes to Plasmodium infections relies on complex interactions between the insect vector and the malaria parasite. A number of studies have shown that the mosquito innate immune responses play an important role in controlling the malaria infection and that the strength of parasite clearance is under genetic control, but little is known about the influence of environmental factors on the transmission success. We present here evidence that the composition of the vector gut microbiota is one of the major components that determine the outcome of mosquito infections. A. gambiae mosquitoes collected in natural breeding sites from Cameroon were experimentally challenged with a wild P. falciparum isolate, and their gut bacterial content was submitted for pyrosequencing analysis. The meta-taxogenomic approach revealed a broader richness of the midgut bacterial flora than previously described. Unexpectedly, the majority of bacterial species were found in only a small proportion of mosquitoes, and only 20 genera were shared by 80% of individuals. We show that observed differences in gut bacterial flora of adult mosquitoes is a result of breeding in distinct sites, suggesting that the native aquatic source where larvae were grown determines the composition of the midgut microbiota. Importantly, the abundance of Enterobacteriaceae in the mosquito midgut correlates significantly with the Plasmodium infection status. This striking relationship highlights the role of natural gut environment in parasite transmission. Deciphering microbe-pathogen interactions offers new perspectives to control disease transmission.     

The Bacterial Flora of the Gut Contents and Environment of Larval Lampreys

Rogers, P. A., Glenn, A. R., Potter, I. C. 1980. The bacterial flora of the gut contents and environment of larval lampreys. (School of Environmental and Life Sciences, Murdoch University, Australia.) — Acta zool. (Stockh.) 61(1): 23–27. The microbial flora of the contents of the intestine of larval lampreys, as well as of the water and substrate in the ammocoetes' habitat, have been cultured on Trypticase Soy Agar. The bacteria have been separated into taxonomic groups, using the scheme of Cowan and Steele (1974) and the API 20E system. The microbial flora of the gut contents of larval lampreys closely parallels that found in the environment in which the ammocoetes live. Bacillus, Aeromonas and Aeromonas-like organisms were by far the most abundant bacteria identified, followed by Pseudomonas and members of the Enterobacteriaceae. The only anaerobic components of the bacterial flora in the gut contents and the environment were Clostridium and a relatively uncommon and unidentified Gram-negative organism. Estimates of abundance of the microflora indicated that the concentration of bacteria was much greater in both the gut contents and the substrate than in the water overlying the animals' burrow.     

Barophilic Bacteria Associated with Digestive Tracts of Abyssal Holothurians

Abyssal holothurians and sediment samples were collected at depths of 4,430 to 4,850 m in the Demerara abyssal plain. Bacterial concentrations in progressive sections of the holothurian digestive tract, as well as in surrounding surface sediments, were determined by epifluorescence microscopy. Total bacterial counts in sediments recently ingested by the animals were 1.5- to 3-fold higher than in surrounding sediments at the deepest station. Lowest counts were observed consistently in the foregut, where the digestive processes of the holothurian are believed to occur. In most animals, counts increased 3- to 10-fold in the hindgut. Microbial activity at 3°C and in situ and atmospheric pressure were determined for gut and sediment samples by measuring the utilization of [¹⁴C]glutamic acid, the doubling time of the mixed-population of culturable bacteria, and the percentage of the total bacterial count responsive to yeast extract in the presence of nalidixic acid, using epifluorescence microscopy. A barophilic microbial population, showing elevated activity under deep-sea pressure, was detected by all three methods in sediments removed from the hindgut. Transmission electron micrographs revealed intact bacteria directly associated with the intestinal lining only in the hindgut. The bacteria are believed to be carried as an actively metabolizing, commensal gut flora that transforms organic matter present in abyssal sediments ingested by the holothurian. Using data obtained in this study, it was calculated that sediment containing organic matter altered by microbial activity cleared the holothurian gut every 16 h, suggesting that abyssal holothurians and their associated gut flora are important participants in nutrient cycles of the abyssal benthic ocean.     

Inhibition of Metarhizium anisopliae by the gut bacterial flora of the desert locust,Schistocerca gregaria: Evidence for an antifungal toxin

A study has been made on the effects of the gut of the desert locust, Schistocerca gregaria, on germination and viability of conidia of the entomopathogenic fungus Metarhizium anisopliae. Germination in the gut of conventional insects in vivo and in conventional gut fluid in vitro was poor. In addition gut-passage through conventional insects reduced viability by over 50%. Adverse pH or osmotic pressure, dietary chemicals, oxygen or nutrient deficiency, fungal cell-wall degrading enzymes, and competition for nutrients with the microflora could not account for the inhibitory properties of the locust gut. Fungitoxicity was, however, dependent on the presence of the gut bacterial flora. Since there was no apparent difference in gut or whole animal physiology between axenic and conventional (nonparasitized) locusts, the hypothesis was made that an antifungal toxin, produced by the gut bacterial flora, was responsible for the above observations. The results are discussed in the light of this possibility.     

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.     

Species Composition and Barotolerance of Gut Microflora of Deep-Sea Benthic Macrofauna Collected at Various Depths in the Atlantic Ocean

The bacterial flora of marine animals collected at depths of 570 to 2,446 m was examined for population size and generic composition, and the barotolerant characteristics of selected bacterial isolates were determined. Total numbers of culturable, aerobic, heterotrophic bacteria were found to be low in animals collected at the greatest ocean depths sampled in this study. Vibrio spp. were predominant in 10 of 15 samples examined, and Photobacterium spp. and yeasts were the major components of the remainder. Pseudomonas, Achromobacter, and Flavobacterium spp. comprised minor components of the gut flora of deep-sea fish. Forty-six pure cultures isolated from samples of seven animals were tested for growth or viability after incubation for 1 week under pressures ranging from 100 to 750 atm. Strains of bacteria isolated from samples of fish intestine were more barotolerant than those from the stomach (P<0.01). When incubated at a pressure of 600 atm, viability of bacterial cultures originally isolated from fish caught at a depth of 570 m was significantly decreased in comparison with viability of cultures from animals caught at depths of 1,393 and 2,446 m (P<0.01). From results of this study, it is concluded that the gut microflora of animals that dwell in the deeper regions of the ocean are adapted to an increased hydrostatic pressure environment, that is, the gut microflora is less inhibited by elevated hydrostatic pressure with increasing depth from which the host animal was collected.     

Transport of bacterial end products from the colon of Periplaneta americana

The possible contribution of fermentation products produced by the anaerobic bacterial hindgut flora of Periplaneta americana was examined with respect to the physiology of the host. The microbial flora of the ileum and colon produced readily detectable quantities of short chain acids in vivo. Experiments where [¹⁴C] acids were injected into the hindgut indicated these products were transported out through the gut wall in vitro and in vivo. Other data underscore the importance of considering the metabolic capabilities of the gut microflora when using dyes as controls in studies on insect gut function.     

Gram-negative bacteria aggravate murine small intestinal Th1-type immunopathology following oral infection with Toxoplasma gondii

Oral infection of susceptible mice with Toxoplasma gondii results in Th1-type immunopathology in the ileum. We investigated gut flora changes during ileitis and determined contributions of gut bacteria to intestinal inflammation. Analysis of the intestinal microflora revealed that ileitis was accompanied by increasing bacterial load, decreasing species diversity, and bacterial translocation. Gram-negative bacteria identified as Escherichia coli and Bacteroides/Prevotella spp. accumulated in inflamed ileum at high concentrations. Prophylactic or therapeutic administration of ciprofloxacin and/or metronidazole ameliorated ileal immunopathology and reduced intestinal NO and IFN-gamma levels. Most strikingly, gnotobiotic mice in which cultivable gut bacteria were removed by quintuple antibiotic treatment did not develop ileitis after Toxoplasma gondii infection. A reduction in total numbers of lymphocytes was observed in the lamina propria of specific pathogen-free (SPF), but not gnotobiotic, mice upon development of ileitis. Relative numbers of CD4(+) T cells did not differ in naive vs infected gnotobiotic or SPF mice, but infected SPF mice showed a significant increase in the frequencies of activated CD4(+) T cells compared with gnotobiotic mice. Furthermore, recolonization with total gut flora, E. coli, or Bacteroides/Prevotella spp., but not Lactobacillus johnsonii, induced immunopathology in gnotobiotic mice. Animals recolonized with E. coli and/or total gut flora, but not L. johnsonii, showed elevated ileal NO and/or IFN-gamma levels. In conclusion, Gram-negative bacteria, i.e., E. coli, aggravate pathogen-induced intestinal Th1-type immunopathology. Thus, pathogen-induced acute ileitis may prove useful to study bacteria-host interactions in small intestinal inflammation and to test novel therapies based on modulation of gut flora.     

Bacterial metabolism of natural and synthetic sex hormones undergoing enterohepatic circulation

Steroids undergoing enterohepatic circulation are exposed to bacterial metabolism particularly by obligate anaerobes which account for 99.99% of the fecal flora. The most common transformation is hydrolysis of conjugated steroids. The glucuronidases are synthesized by Escherichia coli and Bacteroides species. The bacterial catabolism of unconjugated steroids may be considered under several headings: 1. Reduction of ring-A due to clostridia species synthesizing specific enzymes; C. paraputrificum, 3 alpha,5 beta-reductase; C. innocuum, 3 beta,5 beta-reductase; and a new species C.J-1, 3 beta,5 alpha-reductase. 2. Reduction of the delta 5 bond by human fecal flora. The specific strain(s) synthesizing the enzyme have not yet been identified. 3. Reduction of 17-keto estrogens by the above mentioned ring-A reducing clostridia and by Eubacterium lentum. 4. Reduction of 17-keto androstenes by Bacteroides fragilis. 5. Desmolase mediated side chain cleavage at C17-C20 position of 17 alpha-hydroxysteroids by two new species Clostridium scindens and Eubacterium desmolans isolated from human and cat fecal flora respectively and by Clostridium cadavaris isolated from New York City sewage. 6. And 16 alpha- and 21-dehydroxylase by E. lentum a normal inhabitant of the human gut; it is the only organism known to synthesize 16 alpha- or 21-dehydroxylases. Due to the high specificity of the enzymes and the simplicity of extracting the metabolites, biosynthesis of reference compounds and radioimmunoassay reagents is practical and inexpensive. The enzymes can also be used for titration of specific bacterial strains in fecal flora and as markers for bacterial identification in particular for the strains difficult to be defined by regular biochemical reactions.     

Microbial Gut Diversity of Africanized and European Honey Bee Larval Instars

The first step in understanding gut microbial ecology is determining the presence and potential niche breadth of associated microbes. While the core gut bacteria of adult honey bees is becoming increasingly apparent, there is very little and inconsistent information concerning symbiotic bacterial communities in honey bee larvae. The larval gut is the target of highly pathogenic bacteria and fungi, highlighting the need to understand interactions between typical larval gut flora, nutrition and disease progression. Here we show that the larval gut is colonized by a handful of bacterial groups previously described from guts of adult honey bees or other pollinators. First and second larval instars contained almost exclusively Alpha 2.2, a core Acetobacteraceae, while later instars were dominated by one of two very different Lactobacillus spp., depending on the sampled site. Royal jelly inhibition assays revealed that of seven bacteria occurring in larvae, only one Neisseriaceae and one Lactobacillus sp. were inhibited. We found both core and environmentally vectored bacteria with putatively beneficial functions. Our results suggest that early inoculation by Acetobacteraceae may be important for microbial succession in larvae. This assay is a starting point for more sophisticated in vitro models of nutrition and disease resistance in honey bee larvae.     

The role of gut microbiota in pathogenesis of Alzheimer's disease

This paper describes the effects of the gut microbiota on the pathogenesis of Alzheimer's pathology by evaluating the current original key findings and identifying gaps in the knowledge required for validation. The diversity of the gut microbiota declines in the elderly and in patients with Alzheimer's disease (AD). Restoring the diversity with probiotic treatment alleviates the psychiatric and histopathological findings. This presents a problem: How does gut microbiota interact with the pathogenesis of AD? The starting point of this comprehensive review is addressing the role of bacterial metabolites and neurotransmitters in the brain under various conditions, ranging from a healthy state to ageing and disease. In the light of current literature, we describe three different linkages between the present gut microbiome hypothesis and the other major theories for the pathogenesis of AD as follows: bacterial metabolites and amyloids can trigger central nervous system inflammation and cerebrovascular degeneration; impaired gut microbiome flora inhibits the autophagy-mediated protein clearance process; and gut microbiomes can change the neurotransmitter levels in the brain through the vagal afferent fibres.     

微生态学与中医“心与小肠相表里”新论

本文阐述了中医“心与小肠相表里”的理论内涵。中医“心与小肠相表里”与现代医学提出的“脑—肠轴”理论是相通的,具体可理解为中枢神经系统与肠道菌群的密切关系。脑与肠道菌群是相关的,二者在生理上相互配合、在病理上互相影响。同时探讨了微生态学与中医“心与小肠相表里”的相关性,阐述了脑对肠道菌群的调控和肠道菌群对中枢神经系统疾病的发生、发展的影响。依据中医“心与小肠相表里”理论和微生态学的临床应用,提出了用改善肠道菌群的微生态方法治疗和预防一些神经系统疾病的新理念。     

No evidence that gut microbiota impose a net cost on their butterfly host

Gut microbes are believed to play a critical role in most animal life, yet fitness effects and cost–benefit trade‐offs incurred by the host are poorly understood. Unlike most hosts studied to date, butterflies largely acquire their nutrients from larval feeding, leaving relatively little opportunity for nutritive contributions by the adult's microbiota. This provides an opportunity to measure whether hosting gut microbiota comes at a net nutritional price. Because host and bacteria may compete for sugars, we hypothesized that gut flora would be nutritionally neutral to adult butterflies with plentiful food, but detrimental to semistarved hosts, especially when at high density. We held field‐caught adult Speyeria mormonia under abundant or restricted food conditions. Because antibiotic treatments did not generate consistent variation in their gut microbiota, we used interindividual variability in bacterial loads and operational taxonomic unit abundances to examine correlations between host fitness and the abdominal microbiota present upon natural death. We detected strikingly few relationships between microbial flora and host fitness. Neither total bacterial load nor the abundances of dominant bacterial taxa were related to butterfly fecundity, egg mass or egg chemical content. Increased abundance of a Commensalibacter species did correlate with longer host life span, while increased abundance of a Rhodococcus species correlated with shorter life span. Contrary to our expectations, these relationships were unchanged by food availability to the host and were unrelated to reproductive output. Our results suggest the butterfly microbiota comprises parasitic, commensal and beneficial taxa that together do not impose a net reproductive cost, even under caloric stress.     

Bacterial conjugation in the digestive tracts of gnotoxenic chickens.

Escherichia coli K-12 Hfr and F- strains were successively implanted in axenic chicks. Conjugation with exchanges of chromosomal genes occurred with high frequencies in the gut of the chicks and could continue as long as fertile strains coexisted in this environment. Almost all of the expected recombinant types were recovered in the feces under these experimental conditions. Furthermore, these recombinants were analogous to those obtained after conjugations in vitro. Recombinants formed in the gut were more numerous when the F- strain was seeded before the Hfr strain. The recombinants showed no apparent selective advantage over the parental strains in the intestinal medium. They were maintained throughout the experimental period and represented more than 10% of the total intestinal flora. The chick gut is usually rapidly colonized by other bacterial types under natural conditions. The possible effects of other components of the bacterial flora on conjugation of E. coli in holoxenic animals will require subsequent work with more complex microbiological conditions.