Isoenzyme analysis of lichen algae in immobilized pH gradients

A base for a modern species' concept of chlorococcal algae can be obtained not by morphological analysis, but by biochemical characters, e.g. isoenzyme banding patterns. From isolated lichen algae of the genus Trebouxia de Puymaly a set of five such enzymes has been studied by isoelectric focusing in immobilized pH gradients (IPG): phosphoglucomutase, phosphoglucose isomerase, malate dehydrogenase, mannitol dehydrogenase and leucine aminopeptidase. The first four are resolved into isoforms in a pH 4-7 IPG interval, while the last one is analyzed in an IPG pH 3.5-5 span. The patterns are specific for distinct populations, inter- and intraspecifically varying in dependence from their geographical distribution or the lichen species from which they have been isolated. Their limited heterogeneity (one to four isoforms) suggests that they are the products of specific genes rather than artefacts of the extraction procedure or the IPG analysis. Sharp isozyme patterns can only be obtained in a mixed-bed, carrier-ampholyte (CA)-IPG gel and by anodic application, suggesting that the recently proposed mechanism of hydrophobic protein-IPG matrix interaction (Electrophoresis, 1987, 8, 62-70) is fully operative here. As an additional mechanism, it is proposed that, in some cases, CA might simply act, when added to an IPG gel, by buffering, in the transient state, the sample zone before the protein migrates from the liquid phase into the IPG matrix.