Phylogenetic relationship of nonmammalian and avian Blastocystis isolates and conventional subtypes

Abstract

Blastocystis is an intestinal protist commonly identified in human and animal feces. At present, there are 28 proposed subtypes (STs) identified based on the small subunit rRNA gene, 13 of which are found in both humans and animals. In general, nonmammalian and avian groups are infected by the nonmammalian and avian subtypes (NMASTs). However, NMASTs were also isolated from mammalian hosts, suggesting possible cross-contamination and transmission from nonmammalian and avian hosts to other animals and, potentially, humans. Thus, this study determined the possible relationship between NMAST sequences and conventional STs to provide new insights into Blastocystis classification, identification, and epidemiological significance. Phylogenetic trees were constructed using three statistical models, namely, Maximum Likelihood, Neighbor Joining, and Maximum Parsimony, based on the 30 NMAST sequences. The NMAST sequences formed groups clustered closely with other NMAST subtrees. Most sequences of nonmammalian and avian isolates formed distinct monophyletic clades based on their NMAST classification, with some clustering with mammalian and avian STs. These results indicate the close relationship between Blastocystis isolated from mammalian and avian hosts and nonmammalian and avian hosts.

Supplementary information: The online version contains supplementary material available at (10.1007/s12639-022-01554-7).

Keywords: Blastocystis; Nonmammalian and avian subtypes; Phylogeny; Subtypes.

Fig. 1

The phylogenetic analysis using the Maximum Likelihood (ML) and Neighbor Joining (NJ) models was conducted using the Tamura-3 parameter substitution (G) model and 1000 bootstrap value. Maximum Parsimony (MP) also had the same bootstrap value. A consensus tree using ML as the base tree was constructed by presenting the bootstrap values (> 50) of the statistical model as follows: ML/NJ/MP. The scores < 50 were denoted with an asterisk symbol (*), and the subtrees that were absent in NJ and MP were presented with a minus sign (−). The bold typeface indicates the NMAST sequences acquired for the study. NMAST sequences with the same classifications are placed in the same box. Nonmammalian and avian Blastocystis isolates highlighted in yellow indicate association with identified Blastocystis sp. ST or NMAST group. Reference sequences for conventional Blastocystis sp. STs are used as the basis of comparison with NMAST classification. Proteromonas lacertae was used as the outgroup