Gastrointestinal Tract Of Vertebrates Research Articles

Motility-activating mutations upstream of flhDC reduce acid shock survival of Escherichia coli.

Many neutralophilic bacterial species try to evade acid stress with an escape strategy, which is reflected in the increased expression of genes coding for flagellar components. Extremely acid-tolerant bacteria, such as Escherichia coli, survive the strong acid stress, e.g., in the stomach of vertebrates. Recently, we were able to show that the induction of motility genes in E. coli is strictly dependent on the degree of acid stress, i.e., they are induced under mild acid stress but not under severe acid stress. However, it was not known to what extent fine-tuned expression of motility genes is related to fitness and the ability to survive periods of acid shock. In this study, we demonstrate that the expression of FlhDC, the master regulator of flagellation, is inversely correlated with the acid shock survival of E. coli. We encountered this phenomenon when analyzing mutants from the Keio collection, in which the expression of flhDC was altered by an insertion sequence element. These results suggest a fitness trade-off between acid tolerance and motility.IMPORTANCEEscherichia coli is extremely acid-resistant, which is crucial for survival in the gastrointestinal tract of vertebrates. Recently, we systematically studied the response of E. coli to mild and severe acidic conditions using Ribo-Seq and RNA-Seq. We found that motility genes are induced at pH 5.8 but not at pH 4.4, indicating stress-dependent synthesis of flagellar components. In this study, we demonstrate that motility-activating mutations upstream of flhDC, encoding the master regulator of flagella genes, reduce the ability of E. coli to survive periods of acid shock. Furthermore, we show an inverse correlation between motility and acid survival using a chromosomal isopropyl β-D-thio-galactopyranoside (IPTG)-inducible flhDC promoter and by sampling differentially motile subpopulations from swim agar plates. These results reveal a previously undiscovered trade-off between motility and acid tolerance and suggest a differentiation of E. coli into motile and acid-tolerant subpopulations, driven by the integration of insertion sequence elements.

APPLICATION OF METAGENOMICS IN ECOLOGY: A BRIEF OVERVIEW

Starting from the fact that in a microbial community even the concept of species is poorly defined and often debated, but closely related organisms tend to share a substantial amount of genomic sequences, together with a large number of physiological and biochemical properties, it was developed metagenomics. The discipline of metagenomics, defined as the genomic analysis of all microorganisms in a given niche environment, has evolved as an effort to find out more about the microbial diversity of natural environments, such as soil, seawater and the gastrointestinal tract of vertebrates and invertebrates. The purpose of this paper was to bring in front the discipline of metagenomics which will be used in many scientific areas in the future. Our paper represents a brief review of the literature available on the internet regarding the definition, description of metagenomics but also its possibilities of its application in ecology. Moreover, this paper contains the description of MG-RAST software as bioinformatics method that is suitable for usage of metagenomics in ecological studies.

Limosilactobacillus balticus sp. nov., Limosilactobacillus agrestis sp. nov., Limosilactobacillus albertensis sp. nov., Limosilactobacillus rudii sp. nov. and Limosilactobacillus fastidiosus sp. nov., five novel Limosilactobacillus species isolated from the vertebrate gastrointestinal tract, and proposal of six subspecies of Limosilactobacillus reuteri adapted to the gastrointestinal tract of specific vertebrate hosts.

Ten strains, BG-AF3-AT, pH52_RY, WF-MT5-AT, BG-MG3-A, Lr3000T, RRLNB_1_1, STM3_1T, STM2_1, WF-MO7-1T and WF-MA3-C, were isolated from intestinal or faecal samples of rodents, pheasant and primate. 16S rRNA gene analysis identified them as Limosilactobacillus reuteri . However, average nucleotide identity and digital DNA–DNA hybridization values based on whole genomes were below 95 and 70 %, respectively, and thus below the threshold levels for bacterial species delineation. Based on genomic, chemotaxonomic and morphological analyses, we propose five novel species with the names Limosilactobacillus balticus sp. nov. (type strain BG-AF3-AT=DSM 110574T=LMG 31633T), Limosilactobacillus agrestis sp. nov. (type strain WF-MT5-AT=DSM 110569T=LMG 31629T), Limosilactobacillus albertensis sp. nov. (type strain Lr3000T=DSM 110573T=LMG 31632T), Limosilactobacillus rudii sp. nov. (type strain STM3_1T=DSM 110572T=LMG 31631T) and Limosilactobacillus fastidiosus sp. nov. (type strain WF-MO7-1T=DSM 110576T=LMG 31630T). Core genome phylogeny and experimental evidence of host adaptation of strains of L. reuteri further provide a strong rationale to consider a number of distinct lineages within this species as subspecies. Here we propose six subspecies of L. reuteri : L. reuteri subsp. kinnaridis subsp. nov. (type strain AP3T=DSM 110703T=LMG 31724T), L. reuteri subsp. porcinus subsp. nov. (type strain 3c6T=DSM 110571T=LMG 31635T), L. reuteri subsp. murium subsp. nov. (type strain lpuph1T=DSM 110570T=LMG 31634T), L. reuteri subsp. reuteri subsp. nov. (type strain F 275T=DSM 20016T=ATCC 23272T), L. reuteri subsp. suis subsp. nov. (type strain 1063T=ATCC 53608T=LMG 31752T) and L. reuteri subsp. rodentium subsp. nov. (type strain 100-23T=DSM 17509T=CIP 109821T).

Response of gut microbiota to feed-borne bacteria depends on fish growth rate: a snapshot survey of farmed juvenile Takifugu obscurus.

Environmental bacteria have a great impact on fish gut microbiota, yet little is known as to where fish acquire their gut symbionts, and how gut microbiota response to the disturbance from environmental bacteria. Through the integrative analysis by community profiling and source tracking, we show that feed-associated bacteria can impose a strong disturbance upon the hindgut microbiota of cultured fugu. Consequently, marked alterations in the composition and function of gut microbiota in slow growth fugu were observed, implying a reduced stability upon bacterial disturbance from feed. Moreover, quantitative ecological analyses indicated that homogeneous selection and dispersal limitation largely contribute to the community stability and partial variations among hosts in the context of lower degree of disturbance. While the disturbance peaked, variable selection leads to an augmented interaction within gut microbiota, entailing community unstability and shift. Our findings emphasized the intricate linkage between feed and gut microbiota and highlighted the importance of resolving the feed source signal before the conclusion of comparative analysis of microbiota can be drawn. Our results provide a deeper insight into aquaculture of fugu and other economically important fishes and have further implications for an improved understanding of host-microbe interactions in the vertebrate gastrointestinal tract.

How being synanthropic affects the gut bacteriome and mycobiome: comparison of two mouse species with contrasting ecologies

BackgroundThe vertebrate gastrointestinal tract is colonised by microbiota that have a major effect on the host’s health, physiology and phenotype. Once introduced into captivity, however, the gut microbial composition of free-living individuals can change dramatically. At present, little is known about gut microbial changes associated with adaptation to a synanthropic lifestyle in commensal species, compared with their non-commensal counterparts. Here, we compare the taxonomic composition and diversity of bacterial and fungal communities across three gut sections in synanthropic house mouse (Mus musculus) and a closely related non-synanthropic mound-building mouse (Mus spicilegus).ResultsUsing Illumina sequencing of bacterial 16S rRNA amplicons, we found higher bacterial diversity in M. spicilegus and detected 11 bacterial operational taxonomic units with significantly different proportions. Notably, abundance of Oscillospira, which is typically higher in lean or outdoor pasturing animals, was more abundant in non-commensal M. spicilegus. ITS2-based barcoding revealed low diversity and high uniformity of gut fungi in both species, with the genus Kazachstania clearly dominant.ConclusionsThough differences in gut bacteria observed in the two species can be associated with their close association with humans, changes due to a move from commensalism to captivity would appear to have caused larger shifts in microbiota.

The fecal microbiota of wild and captive raptors

BackgroundThe microorganisms populating the gastro-intestinal tract of vertebrates, collectively known as “microbiota”, play an essential role in digestion and are important in regulating the immune response. Whereas the intestinal microbiota in humans and model organisms has been studied for many years, much less is known about the microbiota populating the intestinal tract of wild animals.ResultsThe relatively large number of raptors admitted to the Tufts Wildlife Clinic on the Cummings School of Veterinary Medicine at Tufts University campus provided a unique opportunity to investigate the bacterial microbiota in these birds. Opportunistic collection of fecal samples from raptors of 7 different species in the orders Strigiformes, Accipitriformes, and Falconiformes with different medical histories generated a collection of 46 microbiota samples. Based on 16S amplicon sequencing of fecal DNA, large β-diversity values were observed. Many comparisons exceeded weighted UniFrac distances of 0.9. Microbiota diversity did not segregate with the taxonomy of the host; no significant difference between microbiota from Strigiformes and from Accipitriformes/Falconiformes were observed. In contrast, in a sample of 22 birds admitted for rehabilitation, a significant effect of captivity was found. The change in microbiota profile was driven by an expansion of the proportion of Actinobacteria. Based on a small number of raptors treated with anti-microbials, no significant effect of these treatments on microbiota α-diversity was observed.ConclusionsThe concept of “meta-organism conservation”, i.e., conservation efforts focused on the host and its intestinal microbiome has recently been proposed. The observed effect of captivity on the fecal microbiota is relevant to understanding the response of wildlife to captivity and optimizing wildlife rehabilitation and conservation efforts.

Fecal microbiota associated with phytohaemagglutinin-induced immune response in nestlings of a passerine bird.

The vertebrate gastrointestinal tract is inhabited by a diverse community of bacteria, the so‐called gut microbiota (GM). Research on captive mammalian models has revealed tight mutual interactions between immune functions and GM. However, our knowledge of GM versus immune system interactions in wild populations and nonmammalian species remains poor. Here, we focus on the association between GM community structure and immune response measured via the phytohaemagglutinin (PHA) skin swelling test in 12‐day‐old nestlings of a passerine bird, the barn swallow (Hirundo rustica). The PHA test, a widely used method in field ecoimmunology, assesses cell‐mediated immunity. GM structure was inferred based on high‐throughput 16S rRNA sequencing of microbial communities in fecal samples. We did not find any association between PHA response and GM diversity; however, our data revealed that the intensity of PHA response was correlated with differences in GM composition at the whole‐community level. Ten bacterial operational taxonomic units corresponding to both putative commensal and pathogens were identified as drivers of the compositional variation. In conclusion, our study suggests existence of GM versus immune system interactions in a free‐living nonmammalian species, which corresponds with previous research on captive vertebrates.

Evolutionary Associations of Endosymbiotic Ciliates Shed Light on the Timing of the Marsupial-Placental Split.

Trichostome ciliates are among the most conspicuous protists in the gastrointestinal tract of a large variety of vertebrates. However, little is still known about phylogeny of the trichostome/vertebrate symbiotic systems, evolutionary correlations between trichostome extrinsic traits, and character-dependent diversification of trichostomes. These issues were investigated here, using the relaxed molecular clock technique along with stochastic mapping of character evolution, and binary-state speciation and extinction models. Clock analyses revealed that trichostomes colonized the vertebrate gastrointestinal tract ∼135 Ma, that is, near the paleontological minimum for the split of therian mammals into marsupials and placentals. According to stochastic mapping, the last common ancestor of trichostomes most likely invaded the hindgut of a mammal. Although multiple shifts to fish/amphibian or avian hosts and to the foregut compartments took place during the trichostome phylogeny, only transition to the foregut was recognized as a key innovation responsible for the explosive radiation of ophryoscolecid trichostomes after the Cretaceous/Tertiary boundary, when ungulates began their diversification. Since crown radiations of main trichostome lineages follow those of their mammalian hosts and are in agreement with their historic dispersal routes, the present time-calibrated phylogeny might help to elucidate controversies in the geological and molecular timing of the split between marsupials and placental mammals.

Molecular and Probiotic Characterizations of <i>Lactobacillus reuteri</i> DSM 12246 and Impact of pH on Biomass and Metabolic Profile in Batch-Culture

Lactobacillus reuteri is a powerful probiotic and adjunct functional culture candidate received a lot of scientific attention as it is one of the few endogenous “Lactobacillus” species found in the gastrointestinal tract of vertebrates, including humans, rats, pigs and chicken. The organism has been widely utilized as a probiotic in humans and animals for many years. In the present work L. reuteri DSM 12243; a high reuteri producer strain was molecularly characterized by 16SrRNA and RAPD analyses further, the probiotic properties including acid resistance, bile tolerance, adhesion to epithelial gastric cells, and antibiotic susceptibility were also assessed. Furthermore, the effect of pH on biomass production and metabolic profile of L. reuteri DSM 12246 in batch-culture was studied. The L. reuteri DSM 12246 showed a high similarity with L. reuteri strain I49 KR 36477 (100%) and type strain ATCC 55730 (99% of identity). The strain adhered well to CaCO2 cells and showed to be a highly resistance to acid juice (pH 3.0), with 0.7 log10 cfu/ml reduction in count after 60 min exposition. There is no significant change in the cell count after exposure to bile salts. In batch-cultures, at low pH values both glucose consumption and metabolites were low while the production of lactic acid was noticeable. Maximum biomass was reached at pH 5.5, with growth rate of μ = 0.641/h. The switch in pH values from 3.7 to 6.7 resulted in raising of glucose depletion as well as in the yield of acetate and ethanol. It is concluded that L. reuteri DSM 12246 was deemed as a successful candidate to be used as potential probiotic.

Variation between the oral and faecal microbiota in a free-living passerine bird, the great tit (Parus major).

The gastrointestinal tract of vertebrates is inhabited by diverse bacterial communities that induce marked effects on the host physiology and health status. The composition of the gastrointestinal microbiota is characterized by pronounced taxonomic and functional variability among different regions of the vertebrate gastrointestinal tract. Despite the relatively solid knowledge on the among-region variations of the gastrointestinal microbiota in model mammalian species, there are only a few studies concerning among-region variations of the gastrointestinal microbiota in free-living non-mammalian vertebrate taxa. We used Illumina MiSeq sequencing of bacterial 16S rRNA amplicons to compare the diversity as well as taxonomic composition of bacterial communities in proximal vs. distal parts of the gastrointestinal tract (represented by oral swabs and faecal samples, respectively) in a wild passerine bird, the great tit (Parus major). The diversity of the oral microbiota was significantly higher compared to the faecal microbiota, whereas interindividual variation was higher in faecal than in oral samples. We also observed a pronounced difference in taxonomic content between the oral and faecal microbiota. Bacteria belonging to the phyla Proteobacteria, Firmicutes and Actinobacteria typically dominated in both oral and faecal samples. A high abundance of bacteria belonging to Tenericutes was observed only in faecal samples. Surprisingly, we found only a slight correlation between the faecal and oral microbiota at the within-individual level, suggesting that the microbial composition in these body sites is shaped by independent regulatory processes. Given the independence of these two communities at the individual level, we propose that simultaneous sampling of the faecal and oral microbiota will extend our understanding of host vs. microbiota interactions in wild populations.

Characterization of dominant and cellulolytic bacterial communities along the gut of silver carp Hypophthalmichthys molitrix during cyanobacterial blooms

Silver carp is one of the most important planktivorous fish in Chinese aquaculture and plays a significant role controlling cyanobacterial blooms. A balanced gut microbiota is crucial for growth and health of the host because of its important roles in immune defense, digestion of complex carbohydrates, and production of enterocytes. In our study, the dominant bacterial and cellulolytic bacterial (Clostridium I, Clostridium III, Clostridium XIVab, and Fibrobacter) communities in the contents and mucus of the silver carp gut (foregut, midgut, and hindgut) were analyzed by denaturing gradient gel electrophoresis and quantitative polymerase chain reaction (qPCR) analyses. The results revealed that the dominant and cellulolytic bacterial communities were significantly different among gut regions as well as in contents and mucus. Bacterial diversity and richness in contents and mucus increased along the gut and were higher in contents than those in local mucus. A sequence analysis of gut samples exhibited the conservative phylotypes of Proteobacteria, Actinobacteria, and Firmicutes. The gut of silver carp harbored an abundance of cellulolytic bacteria, particularly Clostridium XIV ab. The foregut segment had the highest proportions of the four cellulolytic bacteria, followed by the midgut and hindgut. However, the proportions of cellulolytic species in the silver carp gut was much lower than those in the terrestrial vertebrate gastrointestinal tract. We conclude that gut bacteria could help silver carp obtain energy from cyanobacteria, which may be why silver carp can maintain high growth rates during cyanobacterial blooms.

The Integration of Gastrointestinal and Renal Function in Nectar‐Feeding Birds

Nectar‐feeding birds face a constant challenge in terms of water balance, experiencing water loading when feeding and potential dehydration when fasting. A growing collection of studies is revealing how species across different orders deal with this osmoregulatory challenge. To meet their high mass‐specific energy demands these birds must often deal with exceptionally high proportionate water fluxes. Birds that ingest large volumes of water may either eliminate excess water in the kidney or regulate the volume of water absorbed in the gastrointestinal tract. Across species, renal filtration during feeding periods generally does not exceed allometric predictions and is not highly responsive to water loading, but renal fractional water reabsorption varies with water load as expected. Hummingbirds (Apodiformes) absorb a constant, high proportion of ingested water across the gastrointestinal tract, while sunbirds and honeyeaters (Passeriformes) modulate intestinal water absorption, potentially avoiding significant water loads when feeding on dilute diets. Data suggest that these passerine nectarivores regulate transepithelial water flux independently of sugar absorption, opening the door to intriguing questions about how water transport is regulated in the vertebrate gastrointestinal tract. Despite reducing their intestinal water absorption, these birds show linear increases in water flux and fractional body water turnover as water intake increases, suggesting that the modulation of fractional water absorption is not sufficient to completely offset dietary water loads. Species in both orders exhibit significant diel variation in renal filtration, essentially shutting down renal filtration during overnight fasts and thus avoiding dehydration. Convergence in diet has led to the evolution of many similar traits in hummingbirds and sunbirds, but the physiological traits of these two groups that allow the processing of a watery and sugary diet may be very different.

Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes.

Current knowledge about the evolutionary morphology of the vertebrate gastrointestinal tract (GIT) is hindered by the low preservation potential of soft tissues in fossils. Exceptionally preserved cololites of individual †Saurichthys from the Middle Triassic of Switzerland provide unique insights into the evolutionary morphology of the GIT. The GIT of †Saurichthys differed from that of other early actinopterygians, and was convergent to that of some living sharks and rays, in exhibiting up to 30 turns of the spiral valve. Dissections and literature review demonstrate the phylogenetic diversity of GIT features and signs of biological factors that influence its morphology. A phylogenetically informed analysis of a dataset containing 134 taxa suggests that body size and phylogeny are important factors affecting the spiral valve turn counts. The high number of turns in the spiral valve of †Saurichthys and some recent sharks and rays reflect both energetically demanding lifestyles and the evolutionary histories of the groups.

Microbiota is an essential element for mice to initiate a protective immunity against Vaccinia virus.

The gastrointestinal tract of vertebrates harbors one of the most complex ecosystems known in microbial ecology and this indigenous microbiota almost always has a profound influence on host-parasite relationships, which can enhance or reduce the pathology of the infection. In this context, the impact of the microbiota during the infection of several viral groups remains poorly studied, including the family Poxviridae. Vaccinia virus (VACV) is a member of this family and is the causative agent of bovine vaccinia, responsible for outbreaks that affect bovines and humans. To determine the influence of the microbiota in the development of the disease caused by VACV, a comparative study using a murine model was performed. Germ-free and conventional, 6- to 7-week-old Swiss NIH mice were infected by tail scarification and intranasally with VACV. Moreover, immunosuppression and microbiota reposition were performed, to establish the interactions among the host's immune system, microbiota and VACV. The data demonstrate that the microbiota is essential for the effective immune response of mice against VACV in intranasal inoculation and to control the virus at the primary site of infection. Furthermore, this study is the first to show that Swiss conventional mice are refractory to the intranasal infection of VACV.

Study and use of the probiotic Lactobacillus reuteri in pigs: a review.

Probiotics are living microorganisms that provide a wide variety of health benefits to the host when ingested in adequate amounts. The bacterial strains most frequently used as probiotic agents are lactic acid bacteria, such as Lactobacillus reuteri, which is one of the few endogenous Lactobacillus species found in the gastrointestinal tract of vertebrates, including humans, rats, pigs and chickens. L. reuteri is one of the most well documented probiotic species and has been widely utilized as a probiotic in humans and animals for many years. Initially, L. reuteri was used in humans to reduce the incidence and the severity of diarrhea, prevent colic and necrotic enterocolitis, and maintain a functional mucosal barrier. As interest in alternatives to in-feed antibiotics has grown in recent years, some evidence has emerged that probiotics may promote growth, improve the efficiency of feed utilization, prevent diarrhea, and regulate the immune system in pigs. In this review, the characteristics of L. reuteri are described, in order to update the evidence on the efficacy of using L. reuteri in pigs.

The Importance of Microbes in Animal Development: Lessons from the Squid-Vibrio Symbiosis

Developmental biology is among the many subdisciplines of the life sciences being transformed by our increasing awareness of the role of coevolved microbial symbionts in health and disease. Most symbioses are horizontally acquired, i.e., they begin anew each generation. In such associations, the embryonic period prepares the animal to engage with the coevolved partner(s) with fidelity following birth or hatching. Once interactions are underway, the microbial partners drive maturation of tissues that are either directly associated with or distant from the symbiont populations. Animal alliances often involve complex microbial communities, such as those in the vertebrate gastrointestinal tract. A series of simpler-model systems is providing insight into the basic rules and principles that govern the establishment and maintenance of stable animal-microbe partnerships. This review focuses on what biologists have learned about the developmental trajectory of horizontally acquired symbioses through the study of the binary squid-vibrio model.

Expression pattern of the homeotic gene Bapx1 during early chick gastrointestinal tract development

Regulation of the Bone Morphogenetic Protein (BMP) signaling pathway is essential for the normal development of vertebrate gastrointestinal (GI) tract, but also for the differentiation of the digestive mesenchymal layer into smooth muscles and submucosal layer. Different studies demonstrated that Bapx1 (for bagpipe homeobox homolog 1) negatively regulates the BMP pathway, but its precise expression pattern during the development and the differentiation of the GI tract mesenchyme actually remains to be examined. Here, we present the spatio-temporal expression profile of Bapx1 in the chick GI tract. We show that Bapx1 is first expressed in the undifferentiated mesenchyme of the gizzard and the colon. After the differentiation of the digestive mesenchyme, we found Bapx1 strongly expressed in the gizzard smooth muscle and in the submucosa layer of the colon. This expression pattern provides new insights into the roles of Bapx1 during the regionalization of the GI tract and the differentiation of the digestive mesenchyme of the colon and the stomach.

Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite

Remains of parasites in vertebrates are rare from the Mesozoic and Paleozoic. Once most parasites that live in – or pass through – the gastrointestinal tract of vertebrates, fossil feces (coprolites) or even intestinal contents (enterolites) can eventually preserve their remains. Here we announce the discovery of a spiral shark coprolite from the Paleozoic bearing a cluster of 93 small oval-elliptical smooth-shelled structures, interpreted as eggs of a tapeworm.The eggs were found in a thin section of an elasmobranch coprolite. Most of the eggs are filled by pyrite and some have a special polar swelling (operculum), suggesting they are non-erupted eggs. One of the eggs contains a probable developing larva. The eggs are approximately 145–155 µm in length and 88–100 µm in width and vary little in size within the cluster. The depositional and morphological features of the eggs closely resemble those of cestodes. Not only do the individual eggs have features of extant tapeworms, but their deposition all together in an elongate segment is typical to modern tapeworm eggs deposited in mature segments (proglottids). This is the earliest fossil record of tapeworm parasitism of vertebrates and establishes a timeline for the evolution of cestodes. This discovery shows that the fossil record of vertebrate intestinal parasites is much older than was hitherto known and that the interaction between tapeworms and vertebrates occurred at least since the Middle-Late Permian.

Some comparative gross and morphometrical studies on the gastrointestinal tract in pigeon (Columbia livia) and Japanese quail (Coturnix japonica).

To study the comparative morphology and morphometry of the gastrointestinal tract of the Japanese quail and pigeon, a total number of twenty birds twenty birds (comprising of ten pigeons and ten Japanese quails) of both sexes were used obtained and used by the researhers. The birds were weighed, dissected and the different parts of the gastrointestinal tract located and eviscerated from which the comparative morphologic and morphometric studies were carried out. The numerical data generated were subjected to statistical analyses using the Microsoft Office Excel 2007 and GraphPad Instat statistical package, with values of P 0.05), their corresponding lengths were 9.77±0.35cm and 12.46±0.99cm respectively, while the mean body weights of the quail and pigeon used in the study were 159.5±8.18g and 265±4.86g for the quail and pigeon, respectively (P>0.05). The mean weights of the proventriculus in the quail and pigeon were 0.69±0.07g and 0.54±0.09g respectively (P>0.05) and their mean lengths were 1.75±0.13cm and 1.44±0.28cm respectively; this was not considered significant relative terms. The weights and lengths of gizzard in the quail and pigeon showed different values with the ultimate conclusion that the gizzard’s weight and length were higher in the pigeon than in the quail (P 0.05). The ceca in the pigeon was rudimentary in contrast to the robust type found in the quail, the weights of both the right and left ceca in the quail and pigeon were considered very significant (P<0.05) and their corresponding lengths considered extremely ssignificant (P<0.05). The colon, being the terminal part of the large intestine is located caudal to the ceca, had their weights in both quail and pigeon not significantly different statistically, but in absolute and relative terms they differed from each other similarly the lengths of the colon in both bird types were considered significant (P<0.05). The vertebrate gastrointestinal tract is a dynamic and energetically expensive organ system whose various anatomical and physiological parameters were regularly being used in clinical evaluations and for assessing dynamics of growth and associated physiological functions for normal and anomalous developments in birds, the knowledge of which will not only add to literatures in these bird types but which will also aid in understanding their biology and mode of domestication as well as being useful for poultry pathologists and clinician, more especially when carrying out postmortem examination.

INSECTS' INTESTINAL BARRIER AGAINST INFECTION

![Figure][1] The enormously large and hence vulnerable surface of the vertebrate gastrointestinal tract is largely protected from pathogenic micro-organisms by a mucous matrix made of water, glycoproteins and antimicrobial substances. The gastrointestinal tract of insects is also exposed to