Effects of bacterial colonization on the porcine intestinal proteome

The gastrointestinal tract harbors a complex community of bacteria, of which many may be beneficial. Studies of germ-free animal models have shown that the gastrointestinal microbiota not only assists in making nutrients available for the host but also contributes to intestinal health and development. We studied small intestinal protein expression patterns in gnotobiotic pigs maintained germ-free, or monoassociated with either Lactobacillus fermentum or non-pathogenic Escherichia coli. A common reference design in combination with labeling with stable isobaric tags allowed the individual comparison of 12 animals. Our results showed that bacterial colonization differentially affected mechanisms such as proteolysis, epithelial proliferation, and lipid metabolism, which is in good agreement with previous studies of other germ-free animal models. We have also found that E. coli has a profound effect on actin remodeling and intestinal proliferation, which may be related to stimulated migration and turnover of enterocytes. Regulations related to L. fermentum colonization involved individual markers for immunoregulatory mechanisms.     

Activity of 3-oxo acid CoA-transferase, D-3-hydroxybutyrate dehydrogenase, hexokinase and carnitine palmitoyltransferase in the stomach and small and large intestine of the rat.

1. Activities of 3-oxo acid CoA-transferase, D-3-hydroxybutyrate dehydrogenase, hexokinase and carnitine palmitoyltransferase have been measured in the gastrointestinal tract. 2. Activity of 3-oxo acid CoA-transferase in the glandular mucosa of the stomach was as high as that in heart and kidney, and was 2--4 times greater than that in other regions of the gastrointestinal tract. It is suggested that metabolism of acetoacetate might support acid secretion on re-feeding after a period without food. 3. All regions of the gastrointestinal tract have the capacity to use ketone bodies, and it is likely that both muscle and mucosa will contribute to their utilization. 4. Activity of hexokinase was twice the rate of glucose utilization by the jejunum under anaerobic conditions. The maximal rate of glucose metabolism in the jejunum may not be substantially different from that in other regions of the gastrointestinal tract. 5. Starvation decreased the capacity for metabolism of glucose in several regions of the intestine. 6. Activities of carnitine palmitolytransferase in the stomach, jejunum and colon were similar, and about one-third of that in the liver. Activity in the jejunum was much higher than the apparent rate of oxidation of exogenous fatty acid. 7. The results do not suggest any large variation between tissues of the gastrointestinal tract in metabolism of glucose or fatty acids, whereas metabolism of ketone bodies may be more prominent in the stomach.     

大肠菌群与氮营养素互作及其对机体健康的影响

蛋白质不仅是构建机体组织的主要原料,而且对动物新陈代谢活动至关重要。数目庞大的肠道细菌在机体营养素,尤其是氮营养素的代谢过程中发挥重要作用。小肠细菌能代谢部分氨基酸,进而影响宿主整体氨基酸的代谢。与小肠相比,大肠拥有更为丰富的菌群和更长的蠕动时间。一方面,进入大肠的氮营养素会影响大肠菌群的代谢和群落结构;另一方面,大肠菌群也能广泛参与氮营养素的代谢与利用,生成许多代谢产物,进而影响机体健康。本文主要综述了日粮蛋白质对大肠菌群的影响、大肠菌群代谢氨基酸的产物及其对肠道生理和机体健康的影响。     

Mechanisms of genetic instability of mollicutes (mycoplasma)

Mollicutes are unique microorganisms characterized by a great extent for the reduction in genetic material, which retained the capability of independent division on acellular nutrient media. Phenotypically mycoplasmas differed from other bacteria by their small size and lack of a cell wall (mollis, soft; cutis, skin). High dependence on metabolism components utilized in the cultivation medium and high metabolic plasticity due to the absence of many genome regulatory elements make mycoplasmas perfect parasites for cells of the eukaryotic origin. The ability of these microorganisms to pass through host cells and their assumed participation in AIDS activation facilitate the study of mycoplasma pathogenesis. Another important feature of mycoplasmas, which is expressed during their interaction with a macroorganism, is their ability to escape from the immune response of a host due to surface antigen variation. These adaptation capacities of mycoplasmas ensuring their life in various biological niches, given a limited genome and the direct metabolic dependence on an environment, cannot be adequately explained at present. In this review, we attempted to collect and systematize data that contribute to our understanding of the important feature of mycoplasmas, genetic instability, which may underlie many of their adaptive responses.     

Genomic signatures of obligate host dependence in the luminous bacterial symbiont of a vertebrate

The majority of bacteria engaged in bioluminescent symbiosis are environmentally acquired and facultatively symbiotic. A few enigmatic bioluminescent symbionts have not been successfully cultured, which has led to speculation that they may be obligately dependent on their hosts. Here, we report the draft genome of the uncultured luminous symbiont of an anomalopid flashlight fish, ‘Candidatus Photodesmus katoptron’. The genome of the anomalopid symbiont is reduced by 80% compared with close relatives and lacks almost all genes necessary for amino acid synthesis and for metabolism of energy sources other than glucose, supporting obligate dependence on the host for growth. ‘Candidatus Photodesmus katoptron’ is the first described obligate mutualistic symbiont of a vertebrate. Unlike most other obligate mutualists, the anomalopid symbiont genome has retained complete pathways for chemotaxis and motility as well as most genes involved in cell wall production, consistent with the hypothesis that these bacteria may be transmitted environmentally during an extra‐host phase.     

Animal models of mucosal Candida infection

Rodent models of oral, vaginal and gastrointestinal Candida infection are described and discussed in terms of their scientific merits. The common feature of all experimental mucosal Candida infections is the need for some level of host immunocompromise or exogenous treatment to ensure quantitatively reproducible disease. A growing literature describes the contributions of such candidiasis models to our understanding of certain aspects of fungal virulence and host response to mucosal Candida albicans challenge. Evidence to date shows that T-lymphocyte responses dominate host immune defences to oral and gastrointestinal challenge, while other, highly compartmentalized responses defend vaginal surfaces. By contrast the study of C. albicans virulence factors in mucosal infection models has only begun to unravel the complex of attributes required to define the difference between strongly and weakly muco-invasive strains.     

The interactions of intracellular Protista and their host cells, with special reference to heterotrophic organisms.

Intracellular genera are found in all the major groups of Protista, but are particularly common among the dinoflagellates, trypanosomatid zooflagellates and suctorian ciliates; the Sporozoa are nearly all intracellular at some stage of their life, and the Microspora entirely so. Intracellular forms can dwell in the nucleus, within phagosomal or other vacuoles or may lie free in the hyaloplasm of their host cells. Organisms tend to select their hosts from a restricted taxonomic range although there are some notable exceptions. There is also great variation in the types of host cell inhabited. There are various reasons for both host and cell selectivity including recognition phenomena at the cell surfaces. Invasion of host cells is usually preceded by surface interactions with the invader. Some organisms depend upon phagocytosis for entry, but others induce host cells to engulf them by non-phagocytic means or invade by microinjection through the host plasma membrane. Protista avoid lysosomal destruction by their resistance to enzyme attack, by surrounding themselves with lysosome-inhibiting vacuoles, by escaping from the phagosomal system into the hyaloplasm and by choosing host cells which lack lysosomes. Nutrition of intracellular heterotrophic organisms involves some degree of competition with the host cell's metabolism as well as erosion of host cell cytoplasm. In Plasmodium infections, red cells are made more permeable to required nutrients by the action of the parasite on the host cell membrane. The parasite is often dependent upon the host cell for complex nutrients which it cannot synthesize for itself. Intracellular forms often profoundly modify the structure and metabolism of the host cell or interfere with its growth and multiplication. This may result in the final lysis of the host cell at the end of the intracellular phase or before the infection of other cells. Certain types of intracellular organisms may have arisen initially as forms attached to the cell surface of digestive or other organs, but the intracellular habit appears to have arisen independently in several groups of Protista.     

Mechanisms of Genetic Instability in Mollicutes (Mycoplasmas)

Mollicutes are unique microorganisms characterized by a great extent for the reduction in genetic material, which retained the capability of independent division on acellular nutrient media. Phenotypically mycoplasmas differed from other bacteria by their small size and lack of a cell wall (mollis, soft; cutis, skin). High dependence on metabolism components utilized in the cultivation medium and high metabolic plasticity due to the absence of many genome regulatory elements make mycoplasmas perfect parasites for cells of the eukaryotic origin. The ability of these microorganisms to pass through host cells and their assumed participation in AIDS activation facilitate the study of mycoplasma pathogenesis. Another important feature of mycoplasmas, which is expressed during their interaction with a macroorganism, is their ability to escape from the immune response of a host due to surface antigen variation. These adaptation capacities of mycoplasmas ensuring their life in various biological niches, given a limited genome and the direct metabolic dependence on an environment, cannot be adequately explained at present. In this review, we attempted to collect and systematize data that contribute to our understanding of the important feature of mycoplasmas, genetic instability, which may underlie many of their adaptive responses.     

Exploration of the link between gut microbiota and purinergic signalling

Growing evidence reveals that microorganisms in the gut are linked to metabolic health and disease risk in human beings to a considerable extent. The focus of research at this stage must tend to focus on cause-and-effect studies. In addition to being a component of DNA and RNA, purine metabolites can be involved in purine signalling in the body as chemical messengers. Abnormalities in purinergic signalling may lead to neuropathy, rheumatic immune diseases, inflammation, tumors, and a wide range of other diseases. It has proved that gut microbes are involved in purinergic signalling. The relationship between these gut-derived purinergic signalling molecules and host metabolism may be one of the important clues to our understanding of the mechanisms by which the microbiota affects host metabolism.     

The impact on production and mechanisms of pathogenesis of trematode infections in cattle and sheep

Trematodes can have marked effects on several components of individual animal productivity—particularly growth and wool production, but there is a need for better definition of their effects upon overall flock and herd productivity and of the economic benefits to be derived from their control by chemical, immunological and/or genetic approaches. The reasons for reduced productivity are complex and include reduced appetite coupled with a protein/energy drain arising from increased protein turnover, and in some cases derangements in gastrointestinal function and mineral metabolism are to be anticipated. Knowledge of the effects of trematodes on animal productivity and metabolism lags far behind that of gastrointestinal nematodes and while there is certainly a need for more study of the effects of trematodes per se, there is perhaps an even more pressing need for experimental and field work on mixed infections.     

Lipids ‒ A key for hepatitis C virus entry and a potential target for antiviral strategies

Viruses have evolved to complex relationship with their host cells. Many viruses modulate the lipid composition, lipid synthesis and signaling of their host cell. Lipids are also an essential part of the life cycle of the hepatitis C virus (HCV). HCV is a major human pathogen, persistently infecting 170 million people worldwide, with no currently effective treatment available for all patients. HCV appears to make use of the host lipid metabolism and one common feature of chronic hepatitis C is the steatosis, characterized by excessive accumulation of triglycerides and lipid content in the liver. Thus, HCV lifecycle appears to be closely connected to host cell lipid metabolism, from cell entry, through viral RNA replication to viral particle production and formation/assembly.     

Symbiotic origin of a novel actin gene in the cryptophyte Pyrenomonas helgolandii

Cryptophytes are photosynthetic protists that have acquired their plastids through the secondary symbiotic uptake of a red alga. A remarkable feature of cryptophytes is that they maintain a reduced form of the red algal nucleus, the nucleomorph, between the second and third plastid membranes (periplastidial compartment; PC). The nucleomorph is thought to be a transition state in the evolution of secondary plastids, with this genome ultimately being lost when photosynthesis comes under full control of the "host" nucleus (e.g., as in heterokonts, haptophytes, and euglenophytes). Genes presently found in the nucleomorph seem to be restricted to those involved in its own maintenance and to that of the plastid; other genes were lost as the endosymbiont was progressively reduced to its present state. Surprisingly, we found that the cryptophyte Pyrenomonas helgolandii possesses a novel type of actin gene that originated from the nucleomorph genome of the symbiont. Our results demonstrate for the first time that secondary symbionts can contribute genes to the host lineage which are unrelated to plastid function. These genes are akin to the products of gene duplication or lateral transfer and provide a source of evolutionary novelty that can significantly increase the genetic diversity of the host lineage. We postulate that this may be a common phenomenon in algae containing secondary plastids that has yet to be fully appreciated due to a dearth of evolutionary studies of nuclear genes in these taxa.     

Host population density and body mass as determinants of species richness in parasite communities: comparative analyses of directly transmitted nematodes of mammals

Epidemiological theory predicts positive correlations between host population density or body mass and species richness among parasite communities. Here I test these predictions by a comparative study of communities of directly transmitted mammalian parasites, gastrointestinal strongylid nematodes. I use data from 45 species of mammals, representing examination of 17 200 individual hosts. The variable studied was the average number of gastrointestinal strongylid nematode species per host population, and three different methods were used to obtain estimates of parasite species richness that are unbiased by number of host individuals examined. Analyses were done using the phylogenetically independent contrast method. Host population density and parasite species richness were strongly positively correlated when the effects of host body weight had been controlled for. Controlling for other variables did not change this, and the relationship was found regardless of method used to correct for uneven sampling effort among host species. A positive relationship between parasite species richness and host body weight was also found, but the effect of host densities had to be controlled for to see this. These relationships between host traits and species richness of directly transmitted parasites are stronger than patterns found using data on indirectly transmitted mammalian parasites, and suggests that links between host traits and parasite species richness are stronger than previously suggested. The results are consistent with parasite species richness being positively linked to pathogen transmission rates and reductions in transmission rates possibly increasing extinction probabilities in parasite populations. The results also suggest that parasites may exert a cost of increases in rate of population energy usage, and thus show that pathogens may be important in generating independence between body mass and rate of population energy usage among host species.     

A commentary on methodological aspects of hydrolysable tannins metabolism in ruminant: a perspective view

Although, the application of tannic acid (TA), gallic acid (GA), natural hydrolysable tannins (HT)-rich ingredients, and HT-rich feeds in ruminant feeding have been explored in order to modify or manipulate microbial activities of digestive tract of animals, the interaction between HT and gastrointestinal microbiota and the fate of HT metabolites (GA, ellagic acid, pyrogallol, resorcinol, phloroglucinol, catechol and urolithin) derived from gastrointestinal microbial HT metabolism in the animal as a whole and animal products are missing. Incomplete biotransformation of HT and TA to GA, pyrogallol, resorcinol, phloroglucinol and other phenolic metabolites is a prevalent phenomenon discovered by researchers who examine the fate of HT metabolites in ruminant. While the rest of fellow researchers do not even examine the fate of HT metabolites and assume the complete biotransformation and fermentation of HT metabolites to volatile fatty acids (VFA). Only three studies have successfully identified the complete biotransformation and fermentation of HT metabolites to VFA in ruminant. The HT metabolites, mostly pyrogallol, produced through incomplete biotransformation of HT have adverse effects on gastrointestinal microbiota and host animal. Lack of awareness regarding the metabolism of HT metabolites and its consequences would compromise ruminant gastrointestinal microbiota, animal welfare, our environment and the power of research papers’ findings. In this perspective paper, I will bring to attention a new angle on the biotransformation and fermentation of HT metabolites in gastrointestinal tract, the role of gastrointestinal microbiota and deficiency of current approach in isolating tannin-degrading bacteria from rumen. Also, suggestions for better monitoring and understanding HT metabolisms in ruminant are presented.     

基于高通量测序的宏基因组学技术在动物胃肠道微生物方面的研究进展

微生物在自然界普遍存在,且具有降解植物细胞壁的特殊功能。动物胃肠道寄生的微生物与宿主生长发育和机体代谢密切相关,可以帮助动物将植物源性物质转化为机体所需要的营养物质。基于高通量测序的宏基因组学技术和分析方法的改进,使人们对复杂环境中微生物的研究更加方便、透彻。而宏基因组学技术应用于动物胃肠道微生物的研究,则有助于挖掘胃肠道微生物基因库并筛选其中的功能基因。这不仅对动物生长发育调控、疾病预防等基础研究具有重要意义,而且在工业生产及食品安全等领域也发挥着重要作用。就基于高通量测序技术的宏基因组技术在动物胃肠道微生物分类、功能应用等方面的研究进行了梳理和综述,旨在为动物科学生产及微生物发酵等相关领域的研究工作提供科学指导。     

苯丙氨酸在宿主和肠道微生物中的代谢研究进展

肠道微生物是宿主生理活动的重要参与者,与宿主的健康和疾病密切相关。研究表明,肠道微生物代谢产物是饮食诱导宿主－微生物相互作用的关键介质,这些代谢产物由微生物直接产生或由环境和宿主中相关分子的代谢转化产生。宿主和肠道微生物之间的化学对话是影响宿主生理的重要环节,对这些代谢途径和信号通路的研究可以进一步揭示微生物代谢与宿主的相互作用机制。芳香族氨基酸包括苯丙氨酸、酪氨酸和色氨酸,是宿主－微生物相互作用的重要信号分子,在胃肠道和远隔器官中发挥着重要的调节作用。本文就苯丙氨酸与肠道微生物的最新研究进展进行综述,重点阐述苯丙氨酸在宿主和肠道微生物中的代谢情况。

     

Human intestinal sulphation of lithocholate: A new site for bile acid metabolism

The liver and intestinal lumen are both important sites in the entero-hepatic circulation of bile salts. Lithocholate, a secondary bile acid and a potent hepatotoxin is probably detoxified in man predominantly by hepatic sulphation. Other sites may also be important. Because steroid sulphating enzymes exist throughout the gastrointestinal tract we have examined the invitro lithocholate sulphation capacity of healthy and diseased ileal and colonic mucosal samples using radio-isotope tracer techniques. Lithocholate sulphation was demonstrated in healthy and diseased ileal mucosa but not in the colonic mucosal samples studied. This new site for lithocholate metabolism acts as a further protective mechanism to prevent toxic unsulphated lithocholate reaching the liver. These findings suggest that the intestinal mucosa may have an important role in the metabolism of other bile acids.     

Environmental Parasitism Risk and Host Infection Status Affect Patch Use in Foraging Wild Mice

Foraging host individuals can defend against fecal–orally transmitted parasites by avoiding feces‐contaminated patches, which has been widely documented among ungulates. However, it remains unclear whether smaller‐sized hosts (e.g., mice), with their high metabolism and constant needs for energy acquisition, can afford the same behavioral strategy. In this study, we used laboratory and field experiments to test whether feces‐contaminated patches are avoided by the Taiwan field mice Apodemus semotus. In the laboratory experiment, wild‐caught mice whose parasitic infection was not manipulated were given two options to forage from feces‐contaminated and uncontaminated patches. These naturally infected mice spent less time in feces‐contaminated than uncontaminated patches. In the field experiment, we reduced gastrointestinal parasite load of randomly chosen mice via anthelmintic treatment. Whereas the untreated mice did not discriminate among food patches with different levels of parasitism risk (i.e., high‐ or low‐risk patches containing conspecific feces of high or low parasite egg counts, no‐feces patches containing no feces), the treated mice spent less time in feces‐contaminated patches than in no‐feces patches. Similar to the larger‐sized ungulates, we demonstrated here that small mammals can also exhibit fecal‐avoidance foraging. Furthermore, such behavior may be influenced by both environmental parasitism risk and host infection status, which has implications in host–parasite transmission dynamics, namely the selective use of uncontaminated patches by the less‐infected (treated) mice may drive parasites to aggregate within the infected portion of a host population.     

Cardinium infection alters cotton defense and detoxification metabolism of its whitefly host

Field monitoring revealed that the infection ratio of the bacterial symbiont Cardinium in the whitefly (Bemisia tabaci MED) was relatively low in northern China. However, the role of this symbiont and the symbiont–whitefly–host plant interaction mechanism are poorly understood. We investigated the influence of Cardinium on the competitiveness of the host whitefly and the physiological interaction between the host plants and host whiteflies. Cardinium-infected whiteflies were displaced by uninfected whiteflies after 5 generations, which showed that Cardinium infection reduced whitefly competitiveness. The defense response genes of cotton significantly decreased under infestation by infected whiteflies compared to uninfected whiteflies. The expression of detoxification metabolism genes, especially the uridine 5ʹ-diphospho-glucuronyltransferase and P450 genes, in infected whiteflies significantly decreased. These results demonstrated that Cardinium could inhibit the defense response of the host plant and decrease the detoxification metabolism ability of the host whitefly. The reduced competitiveness of infected whiteflies may be associated with the inhibition of the whitefly detoxification metabolism by Cardinium, resulting in the reduced performance of infected whiteflies. However, Cardinium infection can suppress plant defenses, which may benefit both infected and uninfected whiteflies when they coexist. This research illustrates the symbiont–whitefly–host plant interaction mechanism and the population dynamics of the whitefly.