Study of the n-TASE cluster on environmental interactions of B. seminalis TC3.4.2R3.

Author(s)

Sarina Tsui

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2021-10-22

Examining board members

Welington Luiz de Araujo; Galdino Andrade Filho; Fernando Dini Andreote; Luiziana Ferreira da Silva

• Advisor: Welington Luiz de Araujo

Abstract

Species of the Burkholderia genus are strongly associated with its pathogenic behavior, due to the worsening of patients with compromised immune systems. Despite this, there is a great interest in bacteria of this genus aiming at biotechnological applications, mainly in the agricultural area. There are studies that demonstrate the importance of Burkholderia spp. in the promotion of plant growth, bioremediation, biological control etc. The Burkholderia seminalis species has been isolated from different types of samples such as water, soil, rhizosphere, seeds, plants and clinics, where it may be involved in nosocomial infections. It is also considered phytopathogenic for apricots, in several animal models it was observed that this species has weak virulence and does not show the ability to colonize/infect rat lungs. The TC3.4.2R3 strain of B. seminalis, isolated from sugarcane roots, presents antagonistic activity against a series of phytopathogenic fungi. Furthermore, it has a potential activity to control symptoms of leaf necrosis in orchids caused by Burkholderia gladioli species. Some characteristics related to growth promotion were observed in this strain. The TC3.4.2R3 lineage has a region comprising the locus tags Bsem_02857 to Bsem_02860 (cluster n-TASE), absent in the other Burkholderia genomes used as reference for its annotation (B. cenocepacia J2315 and B. ambifaria AMMD). It is believed that this cluster was acquired by horizontal transfer and maintained in the genome of this bacterium by selection pressure. Thus, the main objective of this study was to understand the evolutionary origin of this gene cluster, as well as its role in the interaction mechanisms in TC3.4.2R3. The evolutionary history of the n-TASE cluster in TC3.4.2R3 was evaluated by combining HGT study methods such as phylogeny, comparative genomics and molecular analysis. Subsequently, the characterization of the n-TASE cluster was performed, by obtaining two mutants via insertional mutagenesis with the plasmid pGP&#937Tp, SST57 with mutation in the Bsem_02857 gene and SST28 with mutation in the Bsem_02858 gene. The n-TASE cluster of TC3.4.2R3 showed greater similarity with the homologous sequences of Aquamicrobium sp. SK-2 and B. contaminans LMG23361. It was possible to provide evidence that n-TASE was acquired through an HGT event. A correlation of a still unknown nature of the n-TASE cluster genes with swarming motility, biofilm production, tolerance to oxidative stress and bacterial survival in G. mellonella hemolymph, but not correlated to bacterial virulence in this type of infection model. In the future, experiments will be needed to better understand how these genes act in these processes. (AU)

• FAPESP's process: 16/17173-3 - Characterization of the Methyltransferase gene present in the O-antigen gene cluster of the endophytic Burkholderia seminalis TC3.4.2R3, and the role of this gene in the synthesis of antimicrobial compounds
• Grantee: Sarina Tsui
• Support Opportunities: Scholarships in Brazil - Doctorate