Planktonic assays

As mentioned above we obtained most of the poison for our chemical and biological work from the Alaska butter clam. However our search for a dinoflagellate or any other poisonous organism in the water as a source of the poison in the clams was never definitely accomplished. In 1948, and in some years following, along with a survey for toxic butter clams in Southeastern Alaska by the staff at the Fishery Products Research Laboratory at Ketchikan, 1 collected plankton in areas where the clams were found to be toxic. Mouse assays of the plankton showed no toxicity. Microscopic examination of the water in these areas showed heavy growth of microscopic plankton but little or no evidence of... 

I. Laurion, D. R. S. Lean, W. F. Vincent (1998). UVB effects on a plankton community Results from a large-scale enclosure assay. Aquat. Microb. Ecol, 16, 189-198. 

Vincent, W.F. (1981) Rapid physiological assays for nutrient demand by the plankton. II. Phosphorus. Journal of Plankton Research 3, 699-710. 

A crystal violet (CV) assay, which stains the total bacterial biomass, was used to study the efficacy of peptoids against biofilms. The absorbance of the CV stain is measured at = 590nm, and a decrease in absorbance (pale purple) compared to imtreated control (dark purple) implies a decrease in biomass. At 12.5 pM, six out of the seven peptoids tested in this study were able to prevent the formation of P. aeruginosa biofilms by 40-70%, with peptoid 1 being the most active (70% redurtion) and comparable in efficacy to ciprofloxacin and tobramycin (Table 3). However, AMPs only caused 10% reduaion. This was probably because the peptoids were able to kill the planktonic cells which in turn reduced the number of bacterial cells that could have led to the formation of biofilms. 

Figure 2.34 MBEC assay, (a) Biofilms form on the polyst5rene pegs of the MBEC device when planktonic bacteria adsorb to the surface. These bacteria become irreversibly attached and grow to form mature biofihns. Biofilms are encased in sUme, which is sometimes visible to the naked eye. Planktonic cells are also shed from the surface of biofilms, which serves as the inoculum for CA determinations, (b) The peg lid has 96 identical plastic pegs. This hd fits into a trough with channels designed to guide an inoculum across the surface of the pegs. The peg lid fits into a standard 96-well microplate as weU, which is used to set up serial dilutions of antimicrobials.

Harries, R. C., White, D. B. and Macfarlane, R. B., 1970. Mercury compounds reduce photosynthesis by plankton. Science 170, Ti6. Heil, J., Reifferscheid, G., Hellmich, D., Hergenroder, M. and Zahn, R. K., 1991. Genotoxidty of the fungicide Dichlofluanid in seven assays. Environ. Molec. Mutagen. 17, 20-6. 

The potential to inhibit binding of cell surface fucose to LecB and thus disrupt biofilms has also been investigated by the group of Consoli and Geraci, [53] using a calix[4]arene fixed in the cone conformation with four a-L-C-fucosyl units at the upper rim 58 (Fig. 22.18). Cell viability assays with planktonic Pseudomonas aeuruginosa (wild type PAOI) confirmed the molecule has no direct antimicrobial... 

Low oxygen coneentrations (2.10 -5.10 M) are evaluated by BL. BL of photobacteria are proportional to the oxygen eoncentration. Luminescent bacteria can be used in the laboratory for the test of different toxic substances. BL can be applied for environment contamination assays e.g. bioluminescent plankton ( bio-indicators ) are used for detection of heavy metal pollution. CL can also monitor dust, cigarette smoke, smog, ionizing- and UV-radiation [42, 43, 44, 45]. BL detectors are very useful for air tests in, for example, coal mining. 

Since bacteria are capable of forming biofilms on most surfaces, future tests should be focused on biofilm quantification. In assaying biocide efficacy, tests should be conducted based on biofilm populations rather than on liquid culture efficacy (Gu et al. 1998c, 2000c). Planktonic cells are not representative of conditions on surfaces of materials. 

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