Caracteriza????o filogen??tica e funcional da microbiota do intestino do Cupim Comedor de Serapilheira Syntermes wheeleri (Termitidae: Syntermitinae)

Autor: Santana, Renata Henrique
Jazyk: portugalština
Rok vydání: 2017
Předmět:
Zdroj: Biblioteca Digital de Teses e Dissertações da UCBUniversidade Católica de BrasíliaUCB.
Druh dokumentu: Doctoral Thesis
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Termites are well known for their ability to cause agricultural losses and building damage through their ability to digest lignocellulose; however, termites provide important ecosystem services, such as soil bioturbation and nutrient cycling. Microorganisms in the digestive tract of termites are responsible for several of these functions. Syntermes wheeleri (Syntermitinae) is a litter-feeding termite species of the Termitidae family that is abundant in the Brazilian Cerrado. In this work, we characterized the gut microbiota of S. wheeleri, aiming to better understand the ecosystem function of termite-microbe symbiosis and its evolutionary history. First, the gut microbiota composition of worker termites was described by pyrosequencing phylogenetic markers (amplicons), specifically 16S rRNA (archaea and bacteria) and 18S rRNA (fungi). The resulting bacterial taxonomic profile was then compared with the gut microbiota of several other termite species and feeding guilds. To identify the functional groups and activity of the microbiota in the whole gut and the largest proctodeal segments (P1 and P3), the metagenome and metatranscriptome were sequenced by next-generation sequencing (NGS). Amplicon sequences revealed a high abundance of Firmicutes in S. wheeleri, which was not observed in the other termite species. Most archaea belonged to the methanogen orders, and the most abundant fungal classes were Dothideomycetes, Sordariomycetes, and Eurotiomycetes, which have saprophytic species. Ordination analysis of the relative abundance of bacterial taxa showed that the S. wheeleri gut microbiota did not cluster with the microbiota of termites of different clades and feeding guilds. This finding suggests that both variables are important in microbial assembly in termites. The taxonomic profile generated by NGS analysis of the metagenome was similar to the results of amplicon analysis, with higher Firmicutes abundance in P1 and higher Spirochaetes abundance in P3. Additionally, alignment of ribosomal protein S3 identified possible compartment-specific bacterial lineages of Firmicutes, Spirochaetes, Actinobacteria, Bacteroidetes, and Tenericutes. The results of our study revealed a vast metabolic repertoire of termite gut microbes, which supplies nutrients for the host. Differences identified in the P1 and P3 metabolic pathways are likely caused by differences in O2 concentration. As for biomass conversion, the most abundant glycosyl hydrolases (necessary for lignocellulose digestion) detected in the S. wheeleri gut microbiota are a mixture of those that are most abundant in litter-feeding species (fungus growers), as well as wood-, soil-, and dung-feeding species. In addition, putative bacterial laccases (involved in lignin degradation) were detected. Besides the known function of the termite gut microbiota in carbon and nitrogen cycling, we found evidence of its possible involvement in arsenic cycling. This study adds information about microbial establishment in the termite gut, with functional groups selected based on feeding substrate, instead of specific microbial lineages. In addition, our results show that the metagenome can be used to identify molecules with potential industrial applications, such as enzymes useful in biofuel production.
Os cupins s??o conhecidos por causar perdas agr??colas e danos a edifica????es devido a sua capacidade de digerir celulose. No entanto, os cupins tamb??m fornecem importantes servi??os ecossist??micos como a modifica????o do solo e a ciclagem de nutrientes. Os micro-organismos do trato digestivo dos cupins s??o respons??veis por muitas dessas fun????es. Syntermes wheeleri (Syntermitinae) ?? uma esp??cie de cupim da fam??lia Termitidae, comedora de serapilheira e muito abundante no Cerrado. Neste trabalho caracterizamos a microbiota intestinal de Syntermes wheeleri, buscando esclarecer a fun????o ecossist??mica da simbiose entre cupins e micro-organismos e sua hist??ria evolutiva. Inicialmente, a composi????o da microbiota dos oper??rios foi descrita por meio de pirosequenciamento dos marcadores filogen??ticos (amplicons) 16S rRNA (arqueia e bact??ria) e 18S rRNA (fungo). Em seguida, o perfil taxon??mico de bact??rias foi comparado com o apresentado por diferentes esp??cies de cupins e h??bitos alimentares. Finalmente, para identificar os grupos funcionais presentes e ativos da microbiota no intestino inteiro e em seus compartimentos mais volumosos (primeiro - P1 e terceiro - P3 proctodeo) o metagenoma e metatranscriptoma foram submetidos a sequenciamento de alto rendimento (NGS). As sequ??ncias de amplicons revelaram alta abund??ncia de Firmicutes, n??o observada em outras esp??cies de cupins. A maioria das arqueias pertence ??s ordens de metanog??nicas e as classes de fungos mais abundantes foram Dothideomycetes, Sordariomycetes, e Eurotiomycetes, que possuem membros saprof??ticos. Uma an??lise de ordena????o da abund??ncia relativa dos t??xons de bact??ria mostrou que a microbiota de S. wheeleri n??o agrupou com nenhum clado de cupins da fam??lia Termitidae nem com outras guildas alimentares. Esse resultado indica que ambas as vari??veis afetam a composi????o da microbiota. An??lises do metagenoma apontaram perfil taxon??mico semelhante ao obtido pelas an??lises das sequ??ncias de DNA dos marcadores filogen??ticos, com abund??ncia de Firmicutes maior em P1 e de Spirochaetes maior em P3. Adicionalmente, o alinhamento das prote??nas ribossomais S3, mostrou poss??veis linhagens de bact??rias compartimento-espec??ficas de Firmicutes, Spirochaetes, Actinobacteria, Bacteroidetes e Tenericutes. Os resultados deste estudo revelaram vasto repert??rio metab??lico da microbiota, que fornece nutrientes ao hospedeiro. As diferen??as identificadas nas vias metab??licas de P1 e P3 s??o provavelmente causadas por diferen??as na concentra????o de O2. Em rela????o ?? convers??o de biomassa, as fam??lias de glicosil hidrolases (necess??rias para digest??o da lignocelulose) mais abundantes detectadas na microbiota de S. wheeleri s??o uma mistura daquelas mais abundantes na microbiota de cupins comedores de madeira, de esterco e de cultivadores de fungos. Tamb??m foram detectadas lacases putativas (envolvidas na degrada????o de lignina) de origem bacteriana. Al??m da conhecida fun????o da microbiota de cupins no ciclo do carbono e do nitrog??nio, encontramos evid??ncias de sua poss??vel participa????o no ciclo do ars??nio. Este estudo adiciona informa????o sobre o estabelecimento da microbiota no intestino de cupins, com sele????o de grupos funcionais baseados no alimento, ao inv??s de linhagens microbianas espec??ficas. Adicionalmente, os dados aqui gerados podem ser explorados na produ????o de biocombust??veis e em outros processos biotecnol??gicos.
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