Abstract
Our current taxonomic perspective on Entamoeba is largely based on small-subunit ribosomal RNA genes (SSU rDNA) from Entamoeba species identified in vertebrate hosts with minor exceptions such as E. moshkovskii from sewage water and E. marina from marine sediment. Other Entamoeba species have also been morphologically identified and described from non-vertebrate species such as insects; however, their genetic diversity remains unknown. In order to further disclose the diversity of the genus, we investigated Entamoeba spp. in the intestines of three cockroach species: Periplaneta americana, Blaptica dubia, and Gromphadorhina oblongonota. We obtained 134 Entamoeba SSU rDNA sequences from 186 cockroaches by direct nested PCR using the DNA extracts of intestines from cockroaches, followed by scrutinized BLASTn screening and phylogenetic analyses. All the sequences identified in this study were distinct from those reported from known Entamoeba species, and considered as novel Entamoeba ribosomal lineages. Furthermore, they were positioned at the base of the clade of known Entamoeba species and displayed remarkable degree of genetic diversity comprising nine major groups in the three cockroach species. This is the first report of the diversity of SSU rDNA sequences from Entamoeba in non-vertebrate host species, and should help to understand the genetic diversity of the genus Entamoeba.
Highlights
The genus Entamoeba is an important taxonomic group consisting of parasitic species that reside in a variety of vertebrate and invertebrate hosts, and potentially free living species that are isolated from the environment
A fragment corresponding to Entamoeba SSU rDNA was amplified by nested PCR using DNA extracted from the isolated cockroach intestine(s)
A total of 134 Entamoeba SSU rDNA sequences were obtained from 186 cockroaches
Summary
The genus Entamoeba is an important taxonomic group consisting of parasitic species that reside in a variety of vertebrate and invertebrate hosts, and potentially free living species that are isolated from the environment. Clark and colleagues proposed to use “ribosomal lineages”, the nomenclature for newly discovered SSU rDNA sequences close enough to those from other Entamoeba species, but not convincingly considered to be from independent Entamoeba species [2,3,4,5,6,7,8,9]. Quite a few Entamoeba species were identified at the molecular level from primates (e.g. E_nuttalli, and E. gingivalis), reptiles (E. invadens, E. insolita, and E. terrapinae), and environments (E. moshkovskii, E. ecuadoriensis, and E. marina [10]), the genetic diversity of the entire genus Entamoeba remains poorly understood. In order to better understand the genetic diversity of Entamoeba inhabiting invertebrate organisms, we investigated Entamoeba from cockroaches. We report SSU rDNA-based genetic diversity of Entamoeba from three cockroach species: one common house cockroach, Periplaneta americana, and two forest cockroaches, Blaptica dubia (orange-spotted cockroach, Guyana spotted cockroach, or Argentinian wood cockroach) and Gromphadorhina oblongonota (Madagascar forest hissing cockroach)
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