Specialized Gut Research Articles

Vermikomposztálás, mint a szennyvíziszap-komposztálás alternatív megoldása ─ Szemle ─

Agricultural utilisation is one of the most promising uses of sewage sludge in Hungary. Sewage sludge can be applied to agricultural fields in two ways: the injection of dewatered sewage sludge and the application of sewage sludge after composting. Vermicomposting is a special type of composting, where the organic residues are broken down by earthworms. The worms facilitate the decomposition process both by mixing the sludge and by physically degrading it. Earthworm species have various morphotypes requiring different habitats. Compost worms have great adaptability to extreme conditions and are capable of exploiting organic matter in a state of decomposition. Eisenia sp., Eudrilus eugeniae and Perionyx excavatus are important species for vermicomposting. When examining the role and possibilities of vermicomposting, it is important to compare it with traditional composting methods. The most important aspect of producing vermicompost is to ensure optimum environmental conditions for the earthworms, especially in terms of temperature, humidity and aeration, which requires constant attention. An important feature of traditional composting is the thermophilic phase, during which the pathogenic organisms in sewage sludge are destroyed. The thermophilic phase is omitted during vermicomposting due to the thermal sensitivity of the earthworms, but the presence and activity of the earthworms results in similar sterility. Regarding its nutrient content, vermicompost contains larger quantities of total and plant-available macroelements than conventional composts. A further advantage is the presence of the plant hormone agents excreted by earthworms. From the environmental point of view, the ability of earthworms to accumulate heavy metals and the role of their special gut flora in the decomposition of organic pollutants could contribute to the wider use of vermicomposting to dispose of sewage sludge. While vermicompost has many advantages, a number of obstacles need to be overcome before it can be routinely used in Hungary. Many landowners regard sewage sludge compost as hazardous waste that could contaminate their soil and crops rather than as a nutrient and soil amendment. Although numerous studies have been published on sewage sludge, the assessment of long-term effects, including the issues currently of most concern in Hungary, is still lacking. Vermicomposting is therefore a promising, innovative technology for sewage sludge recycling. Sewage sludge and sewage sludge composts with pollutant contents greater than the limits laid down in Government Regulation 50/2001. (IV.3.) can be made suitable for agricultural use by vermicomposting.

Screening and characterizing of xylanolytic and xylose-fermenting yeasts isolated from the wood-feeding termite, Reticulitermes chinensis.

The effective fermentation of xylose remains an intractable challenge in bioethanol industry. The relevant xylanase enzyme is also in a high demand from industry for several biotechnological applications that inevitably in recent times led to many efforts for screening some novel microorganisms for better xylanase production and fermentation performance. Recently, it seems that wood-feeding termites can truly be considered as highly efficient natural bioreactors. The highly specialized gut systems of such insects are not yet fully realized, particularly, in xylose fermentation and xylanase production to advance industrial bioethanol technology as well as industrial applications of xylanases. A total of 92 strains from 18 yeast species were successfully isolated and identified from the gut of wood-feeding termite, Reticulitermes chinensis. Of these yeasts and strains, seven were identified for new species: Candida gotoi, Candida pseudorhagii, Hamamotoa lignophila, Meyerozyma guilliermondii, Sugiyamaella sp.1, Sugiyamaella sp. 2, and Sugiyamaella sp.3. Based on the phylogenetic and phenotypic characterization, the type strain of C. pseudorhagii sp. nov., which was originally designated strain SSA-1542T, was the most frequently occurred yeast from termite gut samples, showed the highly xylanolytic activity as well as D-xylose fermentation. The highest xylanase activity was recorded as 1.73 and 0.98 U/mL with xylan or D-xylose substrate, respectively, from SSA-1542T. Among xylanase-producing yeasts, four novel species were identified as D-xylose-fermenting yeasts, where the yeast, C. pseudorhagii SSA-1542T, showed the highest ethanol yield (0.31 g/g), ethanol productivity (0.31 g/L·h), and its fermentation efficiency (60.7%) in 48 h. Clearly, the symbiotic yeasts isolated from termite guts have demonstrated a competitive capability to produce xylanase and ferment xylose, suggesting that the wood-feeding termite gut is a promising reservoir for novel xylanases-producing and xylose-fermenting yeasts that are potentially valued for biorefinery industry.

Evolution of host specialization in gut microbes: the bee gut as a model

Bacterial symbionts of eukaryotes often give up generalist lifestyles to specialize to particular hosts. The eusocial honey bees and bumble bees harbor two such specialized gut symbionts, Snodgrassella alvi and Gilliamella apicola. Not only are these microorganisms specific to bees, but different strains of these bacteria tend to assort according to host species. By using in-vivo microbial transplant experiments, we show that the observed specificity is, at least in part, due to evolved physiological barriers that limit compatibility between a host and a potential gut colonizer. How and why such specialization occurs is largely unstudied for gut microbes, despite strong evidence that it is a general feature in many gut communities. Here, we discuss the potential factors that favor the evolution of host specialization, and the parallels that can be drawn with parasites and other symbiont systems. We also address the potential of the bee gut as a model for exploring gut community evolution.

Specific Midgut Region Controlling the Symbiont Population in an Insect-Microbe Gut Symbiotic Association

Many insects possess symbiotic bacteria that affect the biology of the host. The level of the symbiont population in the host is a pivotal factor that modulates the biological outcome of the symbiotic association. Hence, the symbiont population should be maintained at a proper level by the host's control mechanisms. Several mechanisms for controlling intracellular symbionts of insects have been reported, while mechanisms for controlling extracellular gut symbionts of insects are poorly understood. The bean bug Riptortus pedestris harbors a betaproteobacterial extracellular symbiont of the genus Burkholderia in the midgut symbiotic organ designated the M4 region. We found that the M4B region, which is directly connected to the M4 region, also harbors Burkholderia symbiont cells, but the symbionts therein are mostly dead. A series of experiments demonstrated that the M4B region exhibits antimicrobial activity, and the antimicrobial activity is specifically potent against the Burkholderia symbiont but not the cultured Burkholderia and other bacteria. The antimicrobial activity of the M4B region was detected in symbiotic host insects, reaching its highest point at the fifth instar, but not in aposymbiotic host insects, which suggests the possibility of symbiont-mediated induction of the antimicrobial activity. This antimicrobial activity was not associated with upregulation of antimicrobial peptides of the host. Based on these results, we propose that the M4B region is a specialized gut region of R. pedestris that plays a critical role in controlling the population of the Burkholderia gut symbiont. The molecular basis of the antimicrobial activity is of great interest and deserves future study.

Environmental and ecological factors that shape the gut bacterial communities of fish: a meta-analysis.

Symbiotic bacteria often help their hosts acquire nutrients from their diet, showing trends of co-evolution and independent acquisition by hosts from the same trophic levels. While these trends hint at important roles for biotic factors, the effects of the abiotic environment on symbiotic community composition remain comparably understudied. In this investigation, we examined the influence of abiotic and biotic factors on the gut bacterial communities of fish from different taxa, trophic levels and habitats. Phylogenetic and statistical analyses of 25 16S rRNA libraries revealed that salinity, trophic level and possibly host phylogeny shape the composition of fish gut bacteria. When analysed alongside bacterial communities from other environments, fish gut communities typically clustered with gut communities from mammals and insects. Similar consideration of individual phylotypes (vs. communities) revealed evolutionary ties between fish gut microbes and symbionts of animals, as many of the bacteria from the guts of herbivorous fish were closely related to those from mammals. Our results indicate that fish harbour more specialized gut communities than previously recognized. They also highlight a trend of convergent acquisition of similar bacterial communities by fish and mammals, raising the possibility that fish were the first to evolve symbioses resembling those found among extant gut fermenting mammals.

Exploring and integrating cellulolytic systems of insects to advance biofuel technology

In line with the requirements for sustainable economies and clean environments, cellulose-based biofuels have recently received tremendous attention both in industry and academic communities worldwide. Alternative and renewable fuels derived from lignocellulosic biomass offer the potential to reduce our dependence on fossil fuels and mitigate global climate change. The world, therefore, is on the verge of an unprecedented increase in the production and use of biofuels. However, in industry, breakthrough technologies to overcome barriers to developing cost-effective processes for converting biomass to fuels and chemicals are not yet fully realized. It is worthy to note that, over the past two decades, industrial bioethanol technology has mainly been based on biocatalysis and fermentation technologies from bacterial and fungal cellulolytic systems, in combination with breakthroughs in molecular genetics, enzyme engineering and metabolic engineering. In practice, the current state of technology with respect to biomass conversion is still far away from being mature for large scale application due to its efficiency and processing economics. To improve upon our current technology, it seems that we need to review our ongoing strategy and explore/learn from other sound cellulolytic systems in nature, such as wood-feeding termites or other insects. Such insects can process lignocellulosic biomass much more efficiently with their highly specialized gut systems, which can truly be considered as highly efficient natural bioreactors. With some of the most intractable issues facing the world regarding efficient and economic conversion of cellulosic biomass, this special publication comes at a critical and timely moment. Most insects are unable to use lignocellulosic substrates as their main food sources, but some insects subsist on lignocellulosic biomass as their only foods. The types of biomass fed upon by cellulolytic insects range from agricultural crops to forest woody substrates, such as in the case of termites (all seven families), wood-feeding roaches (Blattidae, Cryptoceridae), beetles (Anobiidae, Buprestidae, Cerambycidae, Scarabaeidae), wood wasps (Siricidae), leaf-shredding aquatic insects (Pteronarcidae, Limnephilidae, Tipulidae), silverfish (Lepismatidae), leaf-cutting ants (Formicidae), and so on. Cellulose digestion has been demonstrated in more than 20 insect families representing ten distinct insect orders, for example, Thysanura, Plecoptera, Dictyoptera, Orthoptera, Isoptera, Coleoptera, Trichoptera, Hymenoptera, Phasmida and Diptera. The ability of these insects to feed on wood, foliage and detritus has recently stimulated extensive investigation into the mechanisms of how these insects digest the structural and recalcitrant lignocellulose in their foods, as well as their potential to advance current biofuel technologies and processing. Recent studies using advanced molecular biotechnologies, such as metagenomics, proteomics, transcriptomics, and so on, have brought new insights into the mechanisms of biomass deconstruction within these small, but complicated insect gut systems. It has been reported that the digestion efficiency of wood-feeding termites is 74%–99% for cellulose and 65%–87% for hemicellulose, which mainly function via a collaboration between two catalyst systems: (i) termite endogenous catalyst systems, and (ii) catalysts from a variety of gut symbiotic microorganisms, including cellulolytic protozoa and bacteria. The number of the novel cellulases and hemicellulases, as well as the associated encoding genes from a variety of cellulose-feeding insects has been continuously updated in recent years. Descriptions of lignase enzymes and the genes that code them have been lacking; however, recent findings have suggested several viable candidates in both

SCALARIFORM JUNCTIONS: A REVISED MODEL

The structure of scalariform junctions has been analysed in a number of different animal groups by a variety of techniques. These junctions generally display a highly regular intercellular cleft straddled by indistinct cross-striations. They are often in intimate spatial association with mitochondria which lie in parallel to the leaflets of their junctional membranes. Both intercellular and intramembranous features of these junctions have been studied in this report and certain common characteristics are revealed in all species examined. The intercellular cross-striations seen in this junctional type are found to be actually hollow columns or pillars, of hour-glass shape, regularly spaced in rhomboidal, or hexagonal arrays which may be anchored in place by certain of the intramembranous particles (IMPs) that occur in abundance on the membrane Pface. The density of the pillars is less than that of the IMPs. The other particles in the junctional area on both P and E faces may therefore be involved in ion transport, since the particular tissues in which these junctions are found are always involved in fluid flow. Those organisms which exhibit scalariform junctions have no closed circulatory system and thus may require some specialized osmoregulatory control in their excretory tissues. Those tissues which exhibit these junctions include organs such as rectal pads, rectal papillae, gills and nephridia, all of which share a similar physiological function even though they are found in organisms which occupy very different habitats. Such organisms include arthropods of different classes, as well as tunicates, where the presence of the scalariform junctions is restricted to a very specialized gut region. A revised model of scalariform junctions is presented here, which encompasses our new observations of their features. These include intercellular columns which are hollow and ‘hour-glass’, rather than straight sided, in side view, together with their spacing and orderly hexagonal or rhomboidal pattern of distribution; their possible tethering by only a certain percentage of the IMPs in the junctional area is also incorporated in this model.

How to improve histopathological results in the biopsy diagnosis of gut dysganglionosis

In a methodological survey, the technical prerequisites for optimal histopathological diagnosis of gut dysganglionosis are presented. To make a proper diagnosis, the pediatric surgeon or gastroenterologist and the pathologist must consider certain preconditions. The most important steps for the optimal biopsy diagnosis of an aganglionosis, an ultrashort Hirschsprung segment, a intestinal neuronal dysganglionosis (IND), a ganglioneuromatosis, a hypogenesis, or immaturity of the vegetative gut innervation are: (1) taking 3–4 biopsies the size of a peppercorn (3–5 mm3) with submucosa; (2) the best instruments for taking rectal mucosal biopsies are forceps and scissors or a conventional large biopsy forceps; and (3) biopsies may be taken 1 cm, 3–4 cm, 6–9 cm, and 9–12 cm (or from a preternatural anus) above the pectinate line. A biopsy containing mucosa, muscularis mucosae, and submucosa guarantees a satisfying histopathological diagnosis. The native biopsies can be transported on water-ice if the distance to the pathologist takes no longer than 4–6 h. For long distances, biopsies have to be frozen on dry ice (CO2 –80 °C) and transported in a sufficient amount of dry ice (adapted to the time of transportation). For biopsy processing, the following points are important: a total of 122 to 160 15-μm-thick native cryostat serial sections have to be cut per biopsy and distributed on four microscope slides. Forty sections are used for lactic dehydrogenase reactions, 32 for succinic dehydrogenase reactions, and the rest for an acetylcholinesterase (AChE) reaction. An AChE reaction alone is sufficient for the diagnosis of Hirschsprung's disease (HD), but never for IND or other developmental malformations of the submucous and myenteric plexuses. Enzymehistotopochemical reactions allow the assessment of functional parameters. These reactions, in contrast to immunohistochemical staining, offer information about the functional activity of special gut structures, e. g., increased AChE activity in nerve fibers of the rectal wall in HD or a lack of dehydrogenase activity in immature ganglia.

Differential passage time of mistletoe fruits through the gut of honeyeaters and flowerpeckers: effects on seedling establishment.

McKey's (1975) hypothesis that avian dispersers with a specialized gut provide higher quality seed dispersal than unspecialized frugivores was tested using grey mistletoe (Amyema quandang) fruits, and captive mistletoebirds (Dicaeum hirundinaceum) and spinycheeked honeyeaters (Acanthagenys refogularis) in arid South Australia. Mistletoebirds have a specialized gut, unlike spiny-cheeked honeyeaters. The gut passage time of A. quandang fruits through mistletoebirds was 820±29 s (mean±SE, n=188), compared to 2434±36 s (n=436) for honeyeaters. The seeds defecated by both bird species were deployed on twigs of host trees. Despite the longer retention time of fruit in the gut of honeyeaters, the germination percentage of seeds defecated by mistletoebirds (85% of 485 seeds) and honeyeaters (81% of 485 seeds) did not differ significantly 1 week after deployment. However, after 5 months, a significantly greater proportion of seedlings had established from seeds passed by mistletoebirds (42.7%) than from seeds defecated by honeyeaters (31.1%). The data support the notion that the more gentle treatment of seeds in the gut of specialized dispersers translates into higher seedling establishment.

Experimental studies on the life-cycle ofRaillietiella gigliolii(Pentastomida: Cephalobaenida) in the South American worm-lizardAmphisbaena alba: a unique interaction involving two insects

SUMMARYRaillietiella giglioliiis a cephalobaenid pentastomid which inhabits the lungs of the South American worm-lizardAmphisbaena alba. The host is a facultative inquiline of nests of the leaf-cutting antAtta cephaloteswhere it feeds occasionally (and possibly by accident) on ants but more often on beetles and their larvae which are themselves inquilines of ant nests. Ants store exhausted leaf-substrate in special underground chambers which serve as refuse dumps and it is here that larvae of the three-horned rhinoceros beetleCoetosis bilobafeed: these larvae are also known to be prey items ofA. alba. From observations of captive colonies ofAtta, we have demonstrated that pentastomid-egg contaminated faeces ofA. alba, introduced into the colony, are rapidly cut up and thrown onto the refuse dump, where, under natural circumstances they will be eaten byCoelosis. These larvae have an unusual and highly specialized gut physiology and parasite eggs will develop to an infective stage within the haemocoel in 70–96 days. Cockroaches are refractory to infection. Ants are the vital link in transmission since they literally deliver eggs to theCoelosislarvae. The strong trophic links which exist between the various components of the life-cycle offset a low fecundity of 100 eggs/female parasite/day but nonetheless maintain a high prevalence (86%) of infection.

A bacteriological investigation to elucidate the feeding biology of Nais variabilis (Oligochaeta: Naididae)

SUMMARY. The estimated average number of bacteria in the gut of laboratory‐cultured Nais variabilis was 100.4 × 104. This compares with values of 6.7 × 104 and 32.8 × 104, respectively, for N. variabilis and N. barbata obtained from a river.Comparison of the viability of heterotrophic bacteria in the food and gut of N. variabilis indicated a decline in viability of up to 99.6% during the passage of bacteria through the gut. The estimated gut retention time was 39 ± 8 min at 18°C and therefore loss of viability is unlikely to be due to long retention in the gut. Loss of viability is, however, a prerequisite of bacterial digestion by the worm and provides circumstantial evidence that ingested bacteria are used as food.No conclusive evidence was obtained indicating (a) preferential ingestion of certain kinds of bacteria, (b) that the gut environment was selectively hostile to the particular kinds of bacteria studied or (c) that worms had a specialized gut micro‐flora.