Chlorococcum turfosum comb. nov. (Volvocales, Chlorophyceae) and visualization of chimeric sequences

Parachlorococcum turfosum was previously described based on morphological studies of a culture collection strain originally identified as ‘Chlorococcum elkhartiense’ and on an 18S rRNA gene phylogeny of a strain derived from the same original strain but from a different culture collection. However, a subsequently published 18S rRNA gene sequence was inconsistent with the original sequence. Therefore, a new 18S rRNA gene sequence was obtained from the strain from which the holotype was derived. Comparative analyses of the new sequence using the basic local alignment search tool and a newly written Perl code, ChimViewP, which visualizes nucleotide signature shifts characteristic of chimeric sequences, revealed that the sequence used in the original description was of a chimeric nature. Similar analyses also indicated that two published ‘Chlamydomonas acidophila’ sequences are chimeric. Phylogenetic analyses excluding all putative chimeras showed that P. turfosum belongs to Chlorococcum, and thus Chlorococcum turfosum comb. nov. is proposed.