A Class 4-like Chromosomal Integron Found in sp. Genomospecies Isolated from Human Feces.

Integrons are genetic elements that store, express and exchange gene cassettes. These elements are characterized by containing a gene that codes for an integrase (I), a cassette integration site (I) and a variable region holding the cassettes. Using bioinformatics and molecular biology methods, a functional integron found in sp. 3925, a strain isolated from diarrheal stools, is described. To confirm the integron class, a phylogenetic analysis with amino acid sequences was conducted. The integrase was associated to class 4 integrases; however, it is clearly different from them. Thus, we classified the associated element as a class 4-like integron. We found that the integrase activity is not under the control of the SOS or catabolic repression, since the expression was not increased in the presence of mitomycin or arabinose. The class-4-like integron is located on the chromosome and contains two well-defined gene cassettes: A1 that confers resistance to streptomycin and coding for a lipoprotein. It also includes eight Open Reading frames (ORFs) with unknown functions. The strain was characterized through a Multilocus Phylogenetic Analyses (MLPA) of the B, A, D, A, J and X genes. The phylogenetic results grouped it into a different clade from the species already reported, making it impossible to assign a species. We resorted to undertaking complete genome sequencing and a phylogenomic analysis. sp. 3925 is related to and clusters, but it is clearly different from these species. In silico DNA-DNA hybridization (DDH) and Average Nucleotide Identity (ANI) analyses suggested that this isolate belongs to the genomospecies . This paper describes the first class 4-like integron in and contributes to the establishment of genomospecies