Study Of Bacterial Communitity Composition And Diversity In The Alimentary Tracts Of Ants With Different Feeding Habits

Ants are widespread social insects with rich species and quantities in the terrestrial ecosystem,they paly important roles in the substance circulation and energy flow,and are known as the“engineer”of the ecosystem.Ants are highly evolved social insects,and their feeding habits and nutritional niches have differentiated significantly during natural evolution.Morphological modification of the infrabuccal pockets(IBPs)located in the preoral cavity together with the proventriculus of ants are significant manifestations associated with differentiation of feeding habits and survival strategies of ants,and related microorganisms harbored in the alimentary tracts play an important role in nutrition providing,immune responses,population reproduction of their host.However,documents on the morphological variations and bacterial communities in alimentary tracts of ants are limited in some species in tropics,and this is particularly the case on ants occurring in temperate region.This thesis will focus on the dominant ants with distinctly diversified feeding habits and nutritional niches,representing four different subfamilies(Ponerinae,Formicinae,Myrmicinae,and Dolichoderinae)in Qinling Mountains and adjacent areas in Shaanxi province.Comparative study on bacterial communities in the IBPs located in heads,and guts(crops,midguts,and hindguts)located in abdomens of workers,and different developmental stages(larvae,pupae,and cocoons)was conducted by Illumina Hi Seq high-throughput sequencing.The distribution of lactic acid bacteria in honeydew preferring ants,and the ability of dominant strains in decomposing carbohydrates were further studied by using Pac Bio single molecule real time sequencing(SMART),diagnostic PCR and high-performance liquid chromatography method.The main results are as follows:1.Bacterial composition and diversity in the infrabuccal pockets and guts of dominant carnivorous ant species of PonerinaeTwo carnivorous species—Odontomachus monticola and Ectomomyrmex javanus were selected,and the results showed that Wolbachia,Mesoplasma and Spiroplasma are dominant bacteria of the alimentary tracts.Wolbachia and Mesoplasma were dominant in O.monticola,and domiant bacteria were different between colonies.Thereinto,Mesoplasma was dominant in colony O1,Wolbachia was dominant in colonies O2 and O3.Dominant bacteria in the IBPs and larvae were similar,and they also exhibited similarity between different regions of the guts(crops,midguts,and hindguts).Wolbachia,Methyloversatilis and Spiroplasma were dominant in E.javanus,and domiant bacteria were also different between colonies.Thereinto,Wolbachia and Methyloversatilis were dominant in colony E1,Spiroplasma was dominant in colony E2.Dominant bacteria in different regions of the guts were similar but different with the IBPs.β-diversity analysis showed that,bacterial communities were significantly different between the two ponerine ant species and colonies(R~2>0,P=0.001),and exhibited distinct species and colony character;bacterial communities were similar between the IBPs and larvae within colony,but was significantly different with those in the guts(R~2>0,P=0.001);bacteiral communities were similar between different regions of the guts.α-diversity analysis of bacterial communities showed that,Chao and Shannon indices were significantly higher in E.javanus than O.monticola,and they were significantly higher in the IBPs than guts within colony.2.Bacterial composition and diversity in the infrabuccal pockets and guts of dominant omnivorous partial herbivorous ant species of FormicinaeWolbachia and Lactobacillus were dominant in 3 species of Formica(Formica japonica,Formica sanguinea and Formica gageatoides)and 7 colonies,especially in the IBPs and crops.Wolbachia was dominant in the midguts,hindguts,and pupae,Wolbachia and Rickettsiella were dominant in the larvae and cocoons.Lactobacillus,Rickettsiella,and uncultured Acetobacteraceae were dominant in the heads and abdomens of Lasius niger.β-diversity analysis showed that,bacterial communities were different between ant genera(R~2>0,P=0.001),but showed similarity between species within the same genus.Bacterial communities were similar between the IBPs and crops,but distinctly different with those in midguts and hindguts;Bacterial communities were similar between the larvae,pupae,midguts,and hindguts.α-diversity analysis of bacterial communities showed that,Chao and Shannon indices in Lasius niger were significantly higher than F.japonica,F.sanguinea,and F.gageatoides.Chao index in the IBPs,midguts,and hindguts was significantly higher than crops;Shannon index in the IBPs was significantly higher than guts;Chao index in the larvae and pupae was significantly higher than cocoons,Shannon index in the larvae and cocoons was significantly higher than pupae.3.Bacterial composition and diversity in the heads and abdomens of dominant omnivorous ant species of Myrmicinae.Four species(Myrmica excelsa,Myrmica scabrinodis,Messor aciculatus,and Aphaenogaster takahashii)and nine colonies were selected in this thesis,and heads and abdomens of workers,larva and pupa were used to analyze their bacterial composition and diversity.The results showed that Wolbachia was dominant in Myrmica excelsa and Aphaenogaster takahashii,Wolbachia and Acinetobacter were dominant in Myrmica scabrinodis and Messor aciculatus.Wolbachia,Acinetobacter,and Spiroplasma were dominant in the heads,abdomens,larvae,and pupae of most colonies,but different in abundance.β-diversity analysis showed that,bacterial communities were siginificantly different between four ant species and nine colonies(R~2>0,P=0.001),and siginificantly different was exhibited in the heads,abdomens,and different developmental stages(R~2>0,P=0.001).α-diversity analysis of bacterial communities showed that,Chao index in M.excelsa and M.scabrinodis was significantly higher than A.takahashii and Me.aciculatus,and Shannon index in M.excelsa was significantly higher than M.scabrinodis and A.takahashii.Chao and Shannon indices were the highest in the heads and abdomens of the two colonies of M.excelsa(Me1 and Me2),two colonies of M.scabrinodis(Ms1 and Ms2)and the second colony of A.takahashii(At2),and pupae of the colonies At1 and Ms3.4.Bacterial composition and diversity in the infrabuccal pockets and guts of dominant omnivorous ant species of DolichoderinaeLiometopum sinense was selected in this thesis,and the results showed that Acinetobacter was the dominant bacteria.Dominant bacteria between the two colonies were different,thereinto,Acinetobacter was dominant in colony Ls1,Acinetobacter and Anoxybacillus were dominant in colony Ls2;bacteiral communities were different between different regions of the alimentary tracts(IBPs,crops,midguts,and hindguts).β-diversity analysis showed that,bacterial communities showed no significant difference between two colonies,but showed significant difference in different regions of the alimentary tracts(R>0,P=0.001).α-diversity analysis of bacterial communities showed that,Chao index was the highest in the hindguts and lowest in the IBPs in colony Ls1,and no significantly difference was detected between different regions of the alimentary tracts in colony Ls2.Shannon index in the crops and midguts was significantly higher than IBPs in both colonies.5.Function prediction of bacterial communities in the alimentary tracts of ants with different feeding habitsThe function of bacterial communities of dominant ant species in four subfamilies were predicted based on KEGG L3 level,and the results showed that bacterial community genes had similar functions,including metabolic pathway,secondary metabolite biosynthesis,antibiotic biosynthesis,microbial metabolism in different environments,ABC transporter and carbon metabolism.6.Distribution of lactic acid bacteria in honeydew preffering ants,and their ability in decompositing and utilizing carbohydratesThe distribution of lactic acid bacteria in honeydew preferring ants was studied based on bacterial community in the alimentary tracts of dominant ant species of Formicine.The results showed that Lactobacillus was prevalent in 12 of the 15 examined ant species,and especially common in Formica ants.A total of 15 representative bacterial strains were isolated from the IBPs and crops of 7 honeydew preferring ant species,belonging to Lactobacillus lindneri,Lactobacillus sanfranciscensis,Weissella cibaria,and Fructobacillus sp..Two predominant lactic acid bacterial isolates—Lactobacillus sanfranciscensis(La2)and Weissella cibaria(La3)were used in high-performance liquid chromatography to assesse their ability in sugar catabolism,and the results showed that La2 can catabolize sucrose,trehalose,and melezitose,and La3 can catabolize sucrose,melezitose,and raffinose.These results revealed that lactic acid bacteria facilitate ants in catabolizing and utilizing sugars contained in honeydew.In this thesis,bacterial community composition and diversity in alimentary tracts of dominant ant species with different feeding habits were studied,and results showed that bacterial communities in the digestive tracts were significantly different between dominant ant species of different subfamilies,and the difference is closely related to the feeding habits,living environment and structure of digestive tract of ants.Our results revealing the inner relationship between ants and bacteria,and providing new information for exploring co-evolution and nutrient utilization of related bacteria and ants.