DNA base modification inChlorella

Abstract

The nuclear DNA base composition of 26 strains of green algae belonging to the Chlorococcales was analysed by reversed-phase highperformance liquid chromatography (HPLC). 5-Methyldeoxycytidine was the only modified nucleoside detected in addition to the standard nucleosides deoxyadenosine, deoxycytidine, deoxyguanosine and deoxythymidine. The amount of 5-methyldeoxycytidine varied from 1"5 mol% to 12"0 tool% and was correlated with the deoxyguanosine + deoxycytidine (G + C) content of the DNA. No significant influence of deoxycytidine methylation on the thermal stability of the DNA double strand was found. The variation of DNA base composition previously observed within the genus Ckloretla and, in particular, within C. sorokiniana, could not be explained by the influence of variable amounts of modified bases on the DNA melting temperature from which the G + C contents were derived.

BIOCHEMICAL TAXONOMY AND MOLECULAR PHYLOGENY OF THE GENUS CHLORELLA SENSU LATO (CHLOROPHYTA)

“…Ehrlich et al 1975, Rae andSteele 1978). However, both factors are likely not responsible for the observed heterogeneity in base composition in Chlorella because large differences were observed neither in the amount of repetitive sequences nor in DNA base modification Jahnke 1994).…”

“…The bars represent the range of molar guanosine ϩ cytidine (GC) contents determined for the number of strains shown in brackets. Modified after Huss and Jahnke (1994).…”