The redox state of the gut of termites

The redox potential of the gut of nine species of termites was investigated by feeding the insects with redox dyes. The fore- and mid-gut of all species was aerobic with an E′_o probably in excess of + 100 mV. whereas the paunch and colon were anaerobic with an E′_o of about ?230 to ?270 mV, except in Coptotermes lacteus and Nasutitermes exitiosus whose colons were at a E′_o of ?50 to ?125 mV. In four species (Incisitermes barretti, Glyptotermes brevicornis, Stolotermes victoriensis, Coptotermes lacteus) the rectum was aerobic (E′_o about +60 mV), whereas the rectum of the other species was anaerobic (E′_o from about ?125 to ?270 mV).     

Role of bacteria in maintaining the redox potential in the hindgut of termites and preventing entry of foreign bacteria

The hindgut of the lower termites, Mastotermes darwiniensis and Coptotermes lacteus and the higher termite Nasutitermes exitiosus were made aerobic by exposure of the termites to pure oxygen, a procedure which killed their spirochaetes and their protozoa (lower termites only). The time taken for the hindgut to become anaerobic after the termites were restored to normal atmospheric conditions ranged from 2 to 4.5 hr. After oxygen treatment the number of gut bacteria increased some six- to ten-fold in all termite species, indicating that the bacteria are poised to use oxygen entering the gut. Removal of all the hindgut microbiota by feeding tetracycline caused the hindgut to become aerobic in M. darwiniensis and N. exitiosus. The transferring of M. darwiniensis to fresh wood, free of antibiotic, resulted in the return of the normal flora and the eventual establishment of anaerobic conditions in the hindgut. Thus the bacteria appear to be important in maintaining anaerobic conditions in the gut. Attempts to determine whether the protozoa (in the lower termites) played any part in maintaining the Eh of the hindgut were unsuccessful. Serratia marcescens failed to colonise the gut of normal C. lacteus and transiently colonized (for 5 days) the gut of normal N. exitiosus. Transient colonization by S. marcescens (from 6 to 10 days) occurred in N. exitiosus when its hindgut spirochaetes were killed and in C. lacteus when its spirochaetes and protozoa were killed, indicating a possible role for the spirochaetes and/or protozoa in influencing the bacteria allowed to reside in the hindgut. Exposure of normal termites to Serratia provoked an increase in the numbers of the normal gut bacteria.     

Dependence of the higher termite, Nasutitermes exitiosus and the lower termite, Coptotermes lacteus on their gut flora

The importance of the gut microorganisms in the termites Nasutitermes exitiosus and Coptotermes lacteus was investigated by feeding them with antibiotics. With N. exitiosus, antibiotics which killed both the bacteria and the spirochaetes (ampicillin, kanamycin, chloramphenicol, erythromycin, cephaloridine, tetracycline) reduced the life span of the termite from 250 days to about 13 days, whereas antibiotics which had little effect on the flora (penicillin, methicillin) did not greatly reduce the life span of the termite. The essential role of the spirochaetes in N. exitiosus was shown by feeding metronidazole, or exposing the termites to pure oxygen. Both treatments killed the spirochaetes, but not the bacteria, resulting in a life span for the termite of 13–22 days. Acid fuchsin did not kill the spirochaetes. Fungi were not essential for N. exitiosus. In C. lacteus all treatments, except that with acid fuchsin, killed the protozoa, thereby reducing the life span of the termite from 69 days to 6–29 days.     

The origin and distribution of cellulase in the termites,Nasutitermes exitiosus and Coptotermes lacteus

The cellulase of the higher termite Nasutitermes exitiosus was located in the foregut (19%), the midgut (59%), the mixed segment (14%) and in the hindgut (8%). Removal of the gut flora by feeding tetracycline or by starving the termite did not affect the activity of the enzymes indicating that the termite secretes its own cellulase and is not dependent on its gut flora for the digestion of cellulose. The cellulase of the lower termite Coptotermes lacteus was distributed through the foregut (19%), midgut (32%) and hindgut (49%). Removal of the gut flora and fauna, left the specific activity of the cellulase of the fore- and mid-gut largely unaffected, but led to a 20% decrease in the specific activity of the cellulase in the hindgut. In starved C. lacteus the distribution of cellulase activity was foregut, 44%; midgut, 30% and hindgut, 26%. These results indicate that C. lacteus synthesises its own cellulase in addition to using the gut protozoa for cellulose digestion.     

Enzymes of acetate and glucose metabolism in termites

Extracts of tissues of the lower termites, Reticulitermes flavipes and Coptotermes lacteus, and the higher termite, Nasutitermes exitiosus, possess acetyl-CoA synthetase and all the enzymes of the tricarboxylic acid cycle and are thus able to oxidize acetate to CO₂. The specific activities of these enzymes in R. flavipes are sufficient to cope with the rate of acetogenesis by the gut microbiota. The presence of the malic enzyme and malate dehydrogenase, but not pyruvate carboxylase or phosphoenolpyruvate carboxykinase, indicates that they may be important as anaplerotic enzymes for the conversion of pyruvate to oxalacetate. An apparent absence of pyruvate dehydrogenase in all termites suggests that they do not convert pyruvate to acetyl-CoA, but rather convert acetate (transported from the hindgut) to this compound. All the enzymes of glycolysis were present in termite extracts. Thus any glucose absorbed from the midgut, and originating from hydrolysis of cellulose by salivary or midgut enzymes, can be metabolized by termites as an energy source.     

Direct potentiometric determination of redox potentials of the gut contents in the termites Zootermopsis nevadensis and Cubitermes severus and in three other arthropods

A Pt and calomel electrode combination were used to determine the redox potentials of the gut contents in two termites, Zootermopsis nevadensis and Cubitermes severus. Strongly reducing conditions occurred in the paunch of Z. nevadensis (mean E_h = ?160 mV), consistent with many evidences that anaerobic fermentation of wood polymers occurs at this site. In C. severus, a soil-feeder, equivalent regions of the hindgut were more midly reducing (P1: mean E_h = ?104 mV; P3: mean E_h = ?47 mV) while the colon appeared microaerobic or aerobic. It is argued that these conditions are more appropriate to the digestion of humic materials. Potentials consistent with aerobic conditions were found throughout the guts of Periplaneta americana, Locusta migratoria and Glomeris marginata, although the cockroach hindgut was more reducing than the equivalent structures in the other non-termite species.     

Physicochemical Conditions and Microbial Activities in the Highly Alkaline Gut of the Humus-Feeding Larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

The soil macrofauna plays an important role in the carbon and nitrogen cycle of terrestrial ecosystems. In order to gain more insight into the role of the intestinal microbiota in transformation and mineralization of organic matter during gut passage, we characterized the physicochemical conditions, microbial activities, and community structure in the gut of our model organism, the humus-feeding larva of the cetoniid beetle Pachnoda ephippiata. Microsensor measurements revealed an extreme alkalinity in the midgut, with highest values (pH > 10) between the second and third crown of midgut ceca. Both midgut and hindgut were largely anoxic, but despite the high pH, the redox potential of the midgut content was surprisingly high even in the largest instar. However, reducing conditions prevailed in the hindgut paunch of all instars (E_h ~ −100 mV). Both gut compartments possessed a pronounced gut microbiota, with highest numbers in the hindgut, and microbial fermentation products were present in high concentrations. The stimulation of hindgut methanogenesis by exogenous electron donors, such as H₂, formate, and methanol, together with considerable concentrations of formate in midgut and hemolymph, suggests that midgut fermentations are coupled to methanogenesis in the hindgut by an intercompartmental transfer of reducing equivalents via the hemolymph. The results of a cultivation-based enumeration of the major metabolic groups in midgut and hindgut, which yielded high titers of lactogenic, propionigenic, and acetogenic bacteria, are in good agreement not only with the accumulation of microbial fermentation products in the respective compartments but also with the results of a cultivation-independent characterization of the bacterial communities reported in the companion paper (M. Egert, B. Wagner, T. Lemke, A. Brune, and M. W. Friedrich, Appl. Environ. Microbiol. 69:6659-6668, 2003).     

Aromatic compound degradation by the wood-feeding termite Coptotermes formosanus (Shiraki)

Wood-feeding termites (WFT) have proven to be highly efficient for wood digestion. There is evidence to support the hypothesis that there are ligninolytic enzymes existing in the gut of WFT responsible for wood pretreatment toward cellulose utilization. Elucidating the mechanism of biomass pretreatment through lignin modification in termites will help to develop more efficient lignocellulosic biofuel production processes. The in-vivo degradation of aromatic compounds with different substructures, including dyes, lignin model monomers and dimers, and lignin sulfonate, by Coptotermes formosanus (Shiraki) was investigated. The degradation of aromatic compounds was determined using pyrolysis-gas chromatography/mass spectrometry. The results revealed that WFT were able to metabolize the conjugated aromatic structures and that the degradation efficiency is higher in the foregut and midgut regions than in the hindgut. This is the first time that evidence has been provided to show different aromatic compound degradation in the separate gut segments of a termite. This study provides information on the C. formosanus (Shiraki) lignin modification phenomenon, and it demonstrates that phenomenon’s potential in the breakdown of the plant cell wall. Understanding this lignin modification could contribute to technology that will supplant current harsh pretreatment protocols for plant cell walls and thereby better facilitate the conversion of cellulose and hemicellulose.     

Effect of laboratory containment on the nitrogen metabolism of termites

When Nasutitermes exitiosus, Nasutitermes walkeri and Coptotermes lacteus were brought into the laboratory they rapidly lost, within 24–48 hr, their ability to fix dinitrogen. With N. exitiosus and N. walkeri the loss was linear over the first 26–32 hr at a rate of about 3–4% per hour. N. walkeri completely lost its ability to fix dinitrogen and did not recover it during a further 11 days in the laboratory, whereas N. exitiosus and C. lacteus partially recovered their dinitrogen fixing ability to about 25–50% of the original rate. During laboratory storage of up to 60 days both C. lacteus and N. exitiosus gradually lost total nitrogen, while at the same time their uric acid content increased. The uric acid content of N. walkeri increased during 17 days in the laboratory while total nitrogen remained essentially constant. Xanthine dehydrogenase was not detected in freshly-collected N. walkeri but was detectable after two days of laboratory storage and reached a maximum activity in 8–10 days. The rate of dinitrogen fixation, total nitrogen and uric acid of field populations of N. exitiosus and N. walkeri (tested within 2 hr of collection) remained within close limits over a 6–8 week period, indicating that the changes in these parameters observed in populations kept in the laboratory did not occur in field populations. In field populations of N. walkeri the total nitrogen was about 1.4% of the fresh weight (6.7% of the dry weight) and the uric acid content was about 1.3% of the fresh weight (6.6% of the dry weight), with the amount of total nitrogen present as uric acid being about 31%. In N. exitiosus these values were: total nitrogen about 1.6% of the fresh weight (7.4% of the dry weight), uric acid about 0.6% of the fresh weight (2.9% of the dry weight), with uric acid accounting for about 13% of total nitrogen. When workers of N. walkeri were stored in a container near their nest they lost dinitrogen fixing ability to the same extent as workers brought into the laboratory, indicating that disruption of the nest was sufficient to affect dinitrogen fixation.     

Bacteria from the Gut of Australian Termites

The major gut bacteria of the worker caste of nine species of Australian termites, belonging to four families, were isolated and identified to generic level. All species were either facultative anaerobes or strict aerobes. A correlation appears to exist between the major gut bacterium and the family to which the termite belongs. The major bacterium from the two lowest termites, Mastotermes darwiniensis (family Mastotermitidae) and Cryptotermes primus (family Kalotermitidae), was Streptococcus; from four species belonging to the Rhinotermitidae (Heterotermes ferox, Coptotermes acinaciformis, C. lacteus, Schedorhinotermes intermedius intermedius) it was Enterobacter; and from three species of the Termitidae (Nasutitermes exitiosus, N. graveolus, N. walkeri) it was Staphylococcus. Enterobacter was a minor symbiont of M. darwiniensis, C. primus, and N. graveolus; Streptococcus was a minor symbiont of H. ferox, C. lacteus, S. intermedius intermedius, and N. exitiosus; and Bacillus was a minor symbiont of C. acinaciformis and S. intermedius intermedius. M. darwiniensis possessed another minor symbiont tentatively identified as Flavobacterium. C. acinaciformis from three widely separated locations possessed a similar microbiota, indicating some form of control on the composition of the gut bacteria. Bacteria, capable of growth on N-free medium in the presence of nitrogen gas, were isolated from all termites, except N. exitiosus and N. walkeri, and were identified as Enterobacter. No cellulose-degrading bacteria were isolated.     

Determination of pH and oxygen status in the guts of lower and higher termites

The pH of the gut was determined in vitro in six species of termite by means of indicator dyes and a pH electrode. In the lower termite Zootermopsis nevadensis the pH was close to neutrality throughout, ranging 6.0–7.5, but in Reticulitermes lucifugus, acid conditions (pH 5.5–6.0) occurred in the crop and paunch. In the higher termites Nasutitermes costalis, Microcerotermes arboreus, Cubitermes severus and Procubitermes aburiensis, there was a common trend of incresing pH from the crop, which was slightly or moderately acidic, to the first proctodaeal segment (P1) where moderately (N. costalis) and strongly (M. arboreus, C. severus and P. aburiensis) alkaline conditions prevailed. A pH of 10.4 was measured in C. severus, equalling the highest recorded in any insect. In the posterior regions of the hindgut there was a return towards neutral or acidic conditions. When termite guts were homogenized with air-saturated Ringer's solution, the dissolved O₂ content of the Ringer's was reduced. This was shown to be largely attributable to an oxygen deficit generated within the gut in situ. The combined effects of strongly alkaline conditions and reduced oxygen tension on digestive processes and intestinal micro-organisms are discussed.     

Physicochemical conditions and microbial activities in the highly alkaline gut of the humus-feeding larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

The soil macrofauna plays an important role in the carbon and nitrogen cycle of terrestrial ecosystems. In order to gain more insight into the role of the intestinal microbiota in transformation and mineralization of organic matter during gut passage, we characterized the physicochemical conditions, microbial activities, and community structure in the gut of our model organism, the humus-feeding larva of the cetoniid beetle Pachnoda ephippiata. Microsensor measurements revealed an extreme alkalinity in the midgut, with highest values (pH > 10) between the second and third crown of midgut ceca. Both midgut and hindgut were largely anoxic, but despite the high pH, the redox potential of the midgut content was surprisingly high even in the largest instar. However, reducing conditions prevailed in the hindgut paunch of all instars (E(h) approximately -100 mV). Both gut compartments possessed a pronounced gut microbiota, with highest numbers in the hindgut, and microbial fermentation products were present in high concentrations. The stimulation of hindgut methanogenesis by exogenous electron donors, such as H(2), formate, and methanol, together with considerable concentrations of formate in midgut and hemolymph, suggests that midgut fermentations are coupled to methanogenesis in the hindgut by an intercompartmental transfer of reducing equivalents via the hemolymph. The results of a cultivation-based enumeration of the major metabolic groups in midgut and hindgut, which yielded high titers of lactogenic, propionigenic, and acetogenic bacteria, are in good agreement not only with the accumulation of microbial fermentation products in the respective compartments but also with the results of a cultivation-independent characterization of the bacterial communities reported in the companion paper (M. Egert, B. Wagner, T. Lemke, A. Brune, and M. W. Friedrich, Appl. Environ. Microbiol. 69:6659-6668, 2003).     

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.     

Nitrogen mineralization, denitrification, and nitrate ammonification by soil-feeding termites: a 15N-based approach

Soil-feeding termites are abundant and play important roles in the biogeochemical processes in tropical soils. Previous studies indicated that they preferentially utilize the peptidic components of soil organic matter as a nutrient resource. Here, we determined the corresponding mineralization fluxes and elucidated other N transformation processes that occur during soil gut passage using ¹⁵N tracer techniques. Termite-based rates of N mineralization by Cubitermes umbratus and Cubitermes ugandensis in soil microcosms amended with ¹⁵NH₄ ⁺ were 6.6 and 9.2 nmol N day^?1 (g fresh wt)^?1, which means that the soil peptides fuel about 20 and 40% of the respiratory activity of these insects. Considering the areal biomass of soil-feeding termites in humid savannahs, soil-feeding termites should mineralize about 3% of the total N in their food soil per year. In addition to producing ammonia from ingested ¹⁵NO₃ ^? at approximately 10% of the mineralization rate, C. umbratus also formed N₂ at similar rates. The formation of labelled N₂ in microcosms amended with ¹⁵NH₄ ⁺ seems to be at least partially due to nitrification activity in the soil; evidence for the formation of nitrate in the posterior hindgut remains inconclusive. However, the so far unexplained increase of ¹⁵N abundance in the ammonia pools of the posterior hindgut compartments manifests additional hitherto unknown metabolic processes in this gut region. Collectively, our results not only reinforce the concept of nitrogenous soil components as an important dietary resource for soil-feeding termites, but also allow us to predict that N mineralization and nitrate ammonification activities in the termite gut should positively affect the dynamics of N in tropical soil.     

The Selection of an Isolate of the Hyphomycete Fungus,Metarhizium anisopliae,for Control of Termites in Australia

Ninety-three isolates ofMetarhizium anisopliae,mostly derived from a survey of termite material, were screened for activity againstNasutitermes exitiosusandCoptotermes frenchiorC. acinaciformisusing a grooming assay technique. Twenty-six of the most promising isolates were further evaluated by bioassay againstN. exitiosusandC. acinaciformis.All isolates were pathogenic withCoptotermesspp. being more susceptible thanN. exitiosus.A group of nine isolates, chosen for their level of pathogenicity for one or other genus of termites and to represent a genetically diverse group, was finally compared in a minicolony test using termite colonies in 1 liter jars. The isolate, code-named FI-610 (derived from nest-mound material ofC. lacteusin SE New South Wales), was one of the most effective isolates against termites from both of the two colonies tested. This isolate also grew relatively well on agar plates at 36°C. FI-610 was thus selected for field trials and was found to be effective in killing colonies ofC. acinaciformiswhen 10 g (=3 × 10¹¹conidia) or more of conidial powder was blown into the center of the large mound colonies.     

Lutzomyia longipalpis:pH in the Gut, Digestive Glycosidases, and Some Speculations uponLeishmaniaDevelopment

Gontijo, N. F., Almeida-Silva, S., Costa, F. F., Mares-Guia, M. L., Williams, P., and Melo, M. N. 1998.Lutzomyia longipalpis:pH in the gut, digestive glycosidases, and some speculations uponLeishmaniadevelopment.Experimental Parasitology90, 212–219. Screening for digestive glycosidases in different parts of the gut and associated organs ofLutzomyia longipalpisis reported. Searches for the enzymes were made in blood-fed and non-blood-fed females and the enzymes were characterized as soluble or membrane-bound molecules. A total of four different activities were detected, corresponding to the following specificities: an α-glucosidase, anN-acetyl-β-d-glucosaminidase, anN-acetyl-β-d-galactosaminidase, and an α-l-fucosidase. Their possible role and importance forLeishmaniadevelopment are discussed and the α-glucosidase enzyme was partially characterized. The pH inside the gut of non-blood-fed phlebotomines was measured with pH indicator dyes. The pH ranges obtained for crop, midgut, and hindgut were, respectively, higher than pH 6, pH 6, and lower than pH 6. A hypothesis concerning these data andLeishmaniadevelopment is proposed.     

Physicochemical conditions and metal ion profiles in the gut of the fungus-growing termite Odontotermes formosanus

The physicochemical conditions in an insect's gut microenvironment have been reported to play an important role in food processing and metabolisms. In this study, the profiles of oxygen, pH, redox potentials, and hydrogen in the isolated guts of the fungus-growing termite, Odontotermes formosanus Shiraki, were investigated with a microeletrode system. Compared with those in other termites, O. formosanus exhibited a relatively lower oxygen partial pressures in its gut system ranging from 0 to 8.6kPa. The pH profile in the different gut compartments was neutral (pH 6.1-7.4) except in the rectum region. The average redox potentials at the center of each gut region (except rectum) were high and ranged from approximately +70 to +310mV. Especially, as the central intermediate during lignocellulose degradation, hydrogen partial pressures in the hindgut paunch lumen were recorded as high as 10.4kPa. Furthermore, thirteen metal ion concentrations in the termite's gut system, nest symbiotic fungal combs, as well as the nest soil samples were evaluated with Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which indicated that six metal ions (K, Mg, Mn, Ba, Se, and Mo) out of 13 ions recorded in the major digestive tract regions show some significant differences in their spatial distributions. A significant enrichment of some metal ions was also observed in the rectum, fungal combs, and the nest soil samples. The lower oxygen profiles, neutral pH, higher redox potentials, and higher hydrogen accumulation with the characterized spatial distributions for metal ions in the digestive tract of O. formosanus, highlighted the most important distinctiveness of the fungus-growing termites in its gut microenvironments, suggesting that the unique structure and functions of the intestinal ecosystem may present within its gut.     

Cellulose digestion in termites and cockroaches: What role do symbionts play?

• 1.1. Termites and cockroaches are excellent models for studying the role of symbionts in cellulose digestion in insects: they eat cellulose in a variety of forms and may or may not have symbionts.
• 2.2. The wood-eating cockroach, Panesthia cribrata, can be maintained indefinitely, free of microorganisms, on a diet of crystalline cellulose. Under these conditions the RQ is 1, indicating that the cockroach is surviving on glucose produced by endogenous cellulase.
• 3.3. The in vitro rate at which glucose is produced from crystalline cellulose by gut extracts from P. cribrata and Nasutitermes walkeri is comparable to the in vivo production of CO₂ in these insects, clearly indicating that the rate of glucose production from crystalline cellulose is sufficient for their needs.
• 4.4. In all termites and cockroaches examined, cellulase activity was found in the salivary glands and predominantly in the foregut and midgut. These regions are the normal sites of secretion of digestive enzymes and are either devoid of microorganisms (salivary glands) or have very low numbers.
• 5.5. Endogeneous cellulases from termites and cockroaches consist of multiple endo-β-1,4-glucanase (EC 3.2.1.4) and β-1,4-glucosidase (EC 3.2.1.21) components. There is no evidence that an exo-β-1,4-glucanase (cellobiohydrolase) (EC 3.2.1.91) is involved in, or needed for, the production of glucose from crystalline cellulose in termites or cockroaches as the endo-β-1,4-glucanase components are active against both crystalline cellulose and carboxymethylcellulose.
• 6.6. There is no evidence that bacteria are involved in cellulose digestion in termites and cockroaches. The cellulase associated with the fungus garden of M. michaelseni is distinct from that in the midgut; there is little indication that the fungal enzymes are acquired or needed. Lower termites such as Coptotermes lacteus have Protozoa in their hindgut which produce a cellulase(s) quite distinct from that in the foregut and midgut.

     

Redox potential of plastoquinone A in spinach chloroplasts

The redox potential of plastoquinone A in spinach chloroplasts was determined. The midpoint potential of the quinone is about +80 mV at pH 7.0 with an n value of 2. The pH-dependence of the potential is ?30 mV per pH between pH 4.0 and 5.7, and ?60 mV per pH between pH 5.7 and 8.0. The change of the slope at pH 5.7 is interpreted as the protonation of the oxidized plastoquinone A.     

The Gut Bacterial Communities Associated with Lab-Raised and Field-Collected Ants of Camponotus fragilis (Formicidae: Formicinae)

Camponotus is the second largest ant genus and known to harbor the primary endosymbiotic bacteria of the genus Blochmannia. However, little is known about the effect of diet and environment changes on the gut bacterial communities of these ants. We investigated the intestinal bacterial communities in the lab-raised and field-collected ants of Camponotus fragilis which is found in the southwestern United States and northern reaches of Mexico. We determined the difference of gut bacterial composition and distribution among the crop, midgut, and hindgut of the two types of colonies. Number of bacterial species varied with the methods of detection and the source of the ants. Lab-raised ants yielded 12 and 11 species using classical microbial culture methods and small-subunit rRNA genes (16S rRNAs) polymerase chain reaction-restriction fragment-length polymorphism analysis, respectively. Field-collected ants yielded just 4 and 1–3 species using the same methods. Most gut bacterial species from the lab-raised ants were unevenly distributed among the crop, midgut, and hindgut, and each section had its own dominant bacterial species. Acetobacter was the prominent bacteria group in crop, accounting for about 55 % of the crop clone library. Blochmannia was the dominant species in midgut, nearly reaching 90 % of the midgut clone library. Pseudomonas aeruginosa dominated the hindgut, accounting for over 98 % of the hindgut clone library. P. aeruginosa was the only species common to all three sections. A comparison between lab-raised and field-collected ants, and comparison with other species, shows that gut bacterial communities vary with local environment and diet. The bacterial species identified here were most likely commensals with little effect on their hosts or mild pathogens deleterious to colony health.