Vol.65: e22200731, 2022 https://doi.org/10.1590/1678-4324-2022200731 ISSN 1678-4324 Online Edition Brazilian Archives of Biology and Technology. Vol.65: e22200731, 2022 www.scielo.br/babt Article - Engineering, Technology and Techniques Wavelet Applied to the Classification of Bacterial Genomes Leila Maria Ferreira 1 * https://orcid.org/0000-0003-1723-8253 Thelma Sáfadi 1 https://orcid.org/0000-0002-4918-300X Juliano Lino Ferreira 2 https://orcid.org/0000-0002-8502-4444 1 Universidade Federal de Lavras, Departamento de Estatística, Lavras, Minas Gerais, Brasil; 2 Empresa Brasileira de Pesquisa Agropecuária, Embrapa Pecuária Sul, Bagé, Rio Grande do Sul, Brasil. Editor-in-Chief: Alexandre Rasi Aoki Associate Editor: Andressa Novatski Received: 19-Nov-2020; Accepted: 01-Nov-2022. *Correspondence: leilamaria2003@yahoo.com.br; Tel.: 55-35-991740682 (L.M.F.) Abstract: The classifications resulting from phylogenetic analysis are essential tools for evolutionary studies. Phylogenetic is more than a part of evolutionary biology because its underlying philosophy provides a way to see nature, ask questions, and solve problems related to the evolution of organisms. Given the importance of phylogeny, our aim was to devise a method to assess the delimitation of bacterial species. We used the non-decimated discrete wavelet transform. The wavelet function used was Daubechies’ with four null moments, considering seven, four and two decomposition levels. For clustering, the energy (variance) obtained at each level of decomposition and the Mahalanobis distance was used to visualize the dendrogram formation process. Through the analysis, we verified that the gram-positive bacteria were classified well into their respective species, but most gram-negative bacteria did not take into account the more significant amount of energy obtained in scenario two. According to the results, the energy plays an important role in the delimitation of groups of bacterial species. Keywords: Wavelet transform; Decomposition levels; Energy; Bacterial genomes; Species classification. INTRODUCTION To understand evolution, the term ‘phylogenetic tree’ is used to refer to the branching evolutionary history or to a graph that represents this evolutionary history. The phylogenetic tree plays an important role in modern biology because it provides a concise way to visualize evolution from a common ancestor [1]. It is a tool with increasingly recognized utility for various analyses in the field of biological sciences because it helps to HIGHLIGHTS • Advancement of analyzes using the wavelet technique applied to genome data. • Analyze the entire genome, that is, there is no loss of information. • It represents a more detailed technique in which energy (variance) is used.