Análise genômica e interação Bacillus cereus com bananeira

Abstract

The bacterial isolate EB-40 has been used efficiently in the promotion of plant growth with emphasis on the banana crop. Its application induces the elongation of plants, increases the number of leaves and the production of bunches. However, for the production of a commercial bioinoculant, more information is needed on the mechanisms for promoting plant growth and colonization of plant roots. To this end, two studies were carried out. In study 1, the complete genome sequencing of the EB-4O isolate and the identification of genes associated with the promotion of plant growth were performed. The entire genome was sequenced using a hybrid strategy with a combination of short reads, sequenced using the Illumina NextSeq 550, and long reads, sequenced using the Pacbio RSII. The assembled genome sequence was compared with the genome sequences of different bacteria of the genus Bacillus available in the NCBI Microbial Genomes database. Genomic similarity was also calculated using the dDDH (digital DNA-to-DNA hybridization) technique. Biochemical characterization was also performed, verifying the production of 3-indoleacetic acid, biofilm production and nitrate reduction. The complete circular genome was sequenced with a total of 5,374,645 bp, G+C content 35.25% and 5,437 genes were annotated, including 5,288 CDS (Coding DNA Sequences), 42 rRNA, 106 tRNA and 1 tmRNA. Two complete plasmids were also identified and sequenced. Plasmid 1 with 215,918 bp, G+C content 32.61% and 175 CDS.Plasmid 2 with 7631 bp, G+C content 33.85% and 8 CDS. Sequencing revealed a total of 5,288 coding DNA sequences (CDS). Functions were assigned to 2,943 proteins derived from genome annotation, which were categorized in the functional groups of the COG database. Unknown function was assigned to 329 proteins and function prediction to 319. Genes associated with the production of indole-3-acetic acid, phosphate mineralization, production of volatile compounds and siderophores were identified. plant growth, such as the availability of nutrients and the production of phytohormones. The data obtained in the present work allowed the understanding of the genomic and biological basis of the mechanisms of plant growth promotion exhibited by the EB-40 isolate (Bacillus cereus). In addition, the sequence of data obtained can be used in the future to manipulate the mechanisms of plant-microorganism interaction and production of biostimulants. In study 2, the isolate's ability to produce biofilms, which are essential structures for root colonization, was evaluated. Successful root colonization is critical for the establishment of the microorganism in the field. The objective of this work was to document the production of biofilms in B. cereus (EB-40) and the capacity of in vitro colonization of roots of micropropagated seedlings of banana “Prata Anã”. For the identification of biofilm production and its characterization, samples of bacterial cells cultivated in TSA medium and bacterial cells present in the roots of banana explants were collected. Banana explants were grown in solid and liquid MS culture medium. Light microscopy and scanning electron microscopy images were obtained. The biofilms formed in TSA medium were composed of bacterial cells and polymers capable of promoting cell cohesion and integrity. B. cereus was identified only in roots grown in liquid medium. The strain was observed in the lower and posterior sections of the root near the epidermis, apices and root hairs, forming a dense cluster of cells. The organization of bacterial cells in the root was more cohesive when compared to that built in TSA. The results obtained allowed the characterization of the Bacillus cereus biofilm and the verification of its colonization pattern in the roots.