Phylogenetic relationships among members of the sequence type T2/T6 supergroup

(minor revision January 2017, no change November 2023)

Isolates of Acanthamoeba that are classified into either the T2 or T6 sequence types provide a further example of the difficulty of applying a strict 5% sequence divergence rule (for the 18S rRNA gene) for the differentiation of sequence types.  A number of almost complete sequences fall into identifiable subgroups which have less than 5% or approximately 5% sequence divergence from both the T2 and T6 sequence types that were first defined by our lab.  Together with unequivocal T2 or T6 isolates, these intermediates constitute a supertype designated T2/T6.  Phylogenetic analysis suggests that three definable intermediate groups exist, each less frequent in nature than either T2 or T6.  We thus propose the following sub-type classification within the supertype. 


Subtypes within the T2/T6 supertype

T2  – A. palestinensis Reich [ATCC 30870] (U07411)

T2/6A  –  A. polyphaga CCAP 1501/3b [ATCC 30872] (AY026244)

T2/6B  –  isolate OB3b_3A (AB425945)

T2/6C  –  A. palestinensis OX-1  [CCAP 1501/3c] (AF019051)

T6  –  A. palestinensis 2802  [ATCC 50708] (AF019063)


Phylogenetic tree shows relationships among “almost complete” sequences (i.e., deposited sequences of 2000 bases or more) for isolates in the DNA databases as of July 2013.

T2-6 supergroup

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