top agarose or on agar plates containing no zeocine at all wild type no sh ble gene was consistently killed completely at 2 u03bcg ml zeocine resistance to higher concentrations of zeocine e g 25 u03bcg ml indicates higher expression level of the selection gene sh ble at lower irradiance levels fig5 shows the number of exemplary transformed algal cell colonies obtained when cells from a single transformation experiment have been plated under varying light conditions fig5 shows that the number of colonies which is equal to the number of transformed cells which can stand concentrations of zeocine as high as 25 u03bcg ml increases with decreasing light intensities the highest number of transformants was obtained at low light intensities at 5 u03bce u03bcmol photons m2 s the result indicates that the exemplary construct utilized as shown in fig2 has a higher level of gene expression at lower light intensities than at higher light intensities accordingly the exemplary constructs shown in fig2 4 might be utilized for the expression of genes modulated by the intensity of light fig6 shows the number of exemplary transformed algal mutants obtained and showing fifty percent 50 or more growth at a given zeocine concentration but less than 50 at the next highest tested zeocine concentration fig6 illustrates the frequency of 96 clones obtained with the transformation vector pl90 showing more than 50 growth in a liquid assay monitoring growth via od750 at a certain zeocine concentration but less than 50 at the next.