The mechanism of protection by carotenoids against photodynamic killing in Curtobacterium flaccumfaciens pathover poinsettiae (C. poinsettiae) was studied using pigment mutants isolated by treatment with nitrosoguanidine and DNA gyrase inhibitors. Growth rates, pigment composition, pigment levels and the ultrastructure of the wild-type streptomycin resistant strain of G. poinsettiae (wt-str) and all mutants were compared. One mutant, NTG-1, lacked colored carotenoids, and another, NTG-2, was a slow growing mutant containing low levels (14%) of wild-type carotenoid pigments. Except for NTG-1, the other pigment mutants had different proportions of the same pigments found in the wild type as determined by high performance liquid chromatography (HPLC). Only NTG-2 was morphologically distinct at the ultrastructural level.

A series of laboratory experiments and a field investigation were conducted to closely define the application of the ATP assay and ATP as a planktonic biomass estimator for routine use in reservoir limnology. The laboratory experiments verified the published range of C:ATP ratios (i.e. 250:1) as a conversion factor for ATP to biomass in cultured selected genera of freshwater algae, except for the species of blue-green algae examined. The field investigation conducted at Moss Reservoir included organic carbon measurements with ATP biomass in size classes on a depth basis. The ATP biomass varied seasonally and with depth; the best significant mtltiple correlation was between organic carbon and the smallest size class (.45 to 10 um) and total net plankton biomass (.45 to 165 um). Daily monitoring of biomass in size classes demonstrated the sensitivity of the technique.